By W. Hernando. Bowie State University.
Bruna J: Orbital venography: examination Anatomy of the lateral canthal tendon malegra fxt plus 160 mg, Oral cone orbital fat malegra fxt plus 160mg, Plast Reconstr Surg 77:193 160 mg malegra fxt plus, methods 160mg malegra fxt plus, anatomy of the venous orbital Surg Oral Med Oral Pathol Oral Radiol Endod 1986 . Leonardo da Vinci • Goblet-type mucous cells (1452-1519) , whose classical sections of the head illustrate • Basal cells the maxillary antrum and the frontal sinus , apparently recog- Tis mucosa is directly attached to bone and is referred to nized the existence of these cavities as separate functional as the mucoperiosteum . He also referred to the maxillary sinus as “the cavity mucoperiosteum of the sinuses is continuous with that of of the bone which supports the cheek . However , it was only in the drains into the airway, either directly into the nasal cavity late nineteenth century that the frst detailed and systematic (sphenoid ostium) or indirectly by means of more complex anatomic and pathologic descriptions of the paranasal sinuses anatomic structures (frontal recess). Tese descriptions became even more valuable because they could be applied directly to patients and their problems. Ethmoidal Sinus Te invention of the x-ray technique did not add much to the anatomic knowledge of the sinuses. Te last air cells to fnish forming are the strate the incredible accuracy of these pioneers’ knowledge. Te paranasal sinuses develop as out- Ethmoid Air Cells growths from the nasal cavities and erode into the surround- ing bones. All these cavities are lined by respiratory mucosa, Within the labyrinth lie the ethmoid air cells, which are lined which is ciliated and secretes mucus. Tese sinuses air cells are bordered medially by the nasal cavity, laterally by are innervated by the branches of the trigeminal nerve the lamina papyracea, and superiorly by the fovea ethmoida- (Figure 3-3). Te basal lamina of the middle turbinate divides he 9 Te paranasal sinuses start developing from ridges and ethmoid cells into anterior and posterior divisions. Te ante- furrows in the lateral nasal wall as early as the eighth week rior cells empty into the middle meatus, and the posterior of embryogenesis, and they continue pneumatization until cells drain into the superior meatus. Hajek’s scheme depicted the development of a sinus, pneumatization may involve adjacent air cells as existing in three sets of grooves, which form as bones; for example, the ethmoid sinus develops into the valleys between four lamellar projections of bone. Anteriorly frontal, maxillary, or sphenoid bone, and the maxillary sinus the unciform groove (hiatus semilunaris) is formed by the extends into the zygomatic bone. Te third groove is the supe- from the anterior ethmoid cells is via the submandibular rior meatus that is formed between the middle and superior nodes, and the posterior ethmoid cells drain via the retropha- turbinates (Figure 3-4). Innervation is via anterior and posterior by individual; however, seven smaller anterior cells and four ethmoid nerves of the ophthalmic nerve (V1) and the pos- 3 larger posterior cells are typically present. At the middle meatus are one to Maxillary Sinus two agger nasi cells, and posterior to the agger nasi is the 11 ethmoid bulla that contains a superior and inferior cell. Te maxillary sinus begins developing in the third week of Te posterior ethmoid air cells drain via the superior meatus. In the twelfth week of gestation, the maxillary Te anterior ethmoid air cells drain via the middle meatus. Te posterior eth- rapid growth: during the frst 3 years of life and then again moidal artery enters the posterior ethmoid foramen 36 mm from ages 7 to 12 years. Te roof of the sinus contrib- Te maxillary sinuses are paired paranasal sinuses that utes to the foor of the orbit, the foor faces the alveolar develop around the adult dentition to a volume of 15 mL, process, and the sinus proceeds deep and adjacent to the although the volume is smaller in children and enlarges with palate. Te schneiderian membrane lines the maxillary sinus the sinus pneumatization that occurs with advancing age. Te and is composed of pseudostratifed ciliated columnar epi- span of these sinuses is from the region of the third molar thelium. Te concentration of cilia increases with proximity posteriorly to the premolar teeth anteriorly. Te thickness of this membrane is of the sinus vary and range from 25 to 35 mm mesiodistal 0. Compared with the nasal mucosa, the antral mucosa width, 36 to 45 mm vertical height, and 38 to 45 mm deep is thinner and less vascular. At 2 years of age, the sinus continues infe- 8 rather than toward the canine teeth anteriorly. Te foor of the maxillary sinus abuts the alveolar process of the maxilla, frequently approxi- mating the apices of the molar teeth (see the next section). Frontal sinus Te inferior extent of the sinus foor is 1 cm inferior to the foor of the nasal cavity. Te medial wall of the maxillary sinus houses the sinus ostium at its superomedial aspect and the Anterior ethmoid a. Te maxillary sinus ostium empties into the posterior aspect of the semilunar hiatus. Te anterior compartment forms around the primary molars between 8 months and 2 years of age. Te middle compartment forms around the adult frst and second molars from 5 to 12 years of age. By 4 years of age, the sinus reaches the infraorbital the sinus foor to the root tips of the teeth is longest for the canal and continues laterally. By 9 years of age, inferior frst premolar and shortest for the second molar distobuccal growth reaches the region of the hard palate. Te roof contains the infraorbital neurovascular closer to the antral foor than to the palate, and in 20% of bundle. Septa extrinsic to those of maxillary sinus maxillary development are called secondary septa and occur as 0 - 3 years a result of pneumatization after dental extraction. Te overall 7 - 12 years prevalence of septa present in any given maxillary sinus is Adulthood 19 35%. Septa in edentulous regions tend to be larger than those in partially edentulous regions, which are larger still 8 than dentate regions of the alveolus. Te presence of septae is pertinent for sinus lift procedures because they complicate the process of luxating the bony window to expose the sinus and increase the likelihood of sinus membrane perforation. Te accessory ostium typically exists only as an opening and not as a canal, with an average length of 1. Distance from the Roots of the Te clinical signifcance of the ostium existing as a canal is Table 3-1 Maxillary Teeth to the Maxillary an appreciation for how readily a canal obstruction can occur Sinus Floor (Figure 3-6). Two branches of this nerve are usually present: the apices of the maxillary posterior teeth, Oral Surg Oral Med Oral Pathol a smaller superior branch and the larger inferior branch. Te signifcance of this presenta- tion of the superior alveolar nerves is to point out an area at the anterior region of the maxilla where bone can be safely Maxillary Septum removed (e. Septa within the maxillary sinus are of two variet- Te maxillary sinus has rich anastomoses and receives its ies. Te primary septa are formed as part of the three- arterial supply from the infraorbital, sphenopalatine, poste- compartment model of sinus development and act as dividers rior lateral nasal, facial, pterygopalatine, greater palatine, and of the anterior, middle, and posterior components; they are posterior superior alveolar arteries. Innervation of the maxillary sinus is via the anterior superior, middle superior, and posterior superior alveolar nerves. Lymphatic drainage occurs through the infraorbital foramen via the ostium to the 14 submandibular lymphatic system. Te inner plate, or posterior wall (separates the frontal sinus from the anterior cranial fossa), is much Figure 3-7 Frontonasal duct in situ (arrow). Te sinuses often that the degree of pneumatization of the frontal sinuses varies have incompletely separated recesses, which make the and that it may extend laterally as far as the sphenoid wing. Superfcial surgical landmarks for Te ostium of the frontal sinus lies in the posteromedial the frontal sinus were described by Tubbs et al. In their study of 70 adult the anterior part of the middle meatus and the frontal cadavers, these investigators reported that the lateral wall of recess or directly into the anterior end of the infundibulum the frontal sinus never extended more than 5 mm lateral to (Figure 3-7). At this same line and at a plane drawn Tis relationship to the infundibulum and middle meatus through the supraorbital ridges, the roof of the frontal sinus serves to protect the frontal sinus from the spread of disease was never higher than 12 mm, and in the midline, the roof in the osteomeatal complex. Te agger nasi is intimately of the frontal sinus never reached more than 4 cm above the involved, in that the posterior wall of the agger nasi forms nasion. Te frontal sinus is separated from the orbit by a thin the anterior border of the frontal recess, which then passes triangular plate. Tis Regarding the lateral extension of the frontal sinuses, the recess is present in 77% of patients. In the other 23%, drain- authors have observed several cases in which the lateral age occurs via a frontal sinus ostium. For this reason, caution common and are signifcantly related to the presence of must be observed when removing the septum in these cases frontal sinusitis. Te borders of the frontonasal duct are (1) because a brisk avulsion may result in carotid rupture. Te sphenoid sinus drains through a which is formed by the conchal plate; and (4) the lateral single ostium into the sphenoethmoid recess. Te superior wall of the sphenoid Besides the diferent anterior ethmoid cell groups that sinus usually represents the foor of the sella turcica. Conchal: Te area below the sella is a solid block of bone frontal cells into four types: without pneumatization. Presellar: Te sphenoid is pneumatized to the level of • Type 2 is a group of small cells above the agger nasi the frontal plane of the sella and not beyond. Sellar: Te most common type, in which pneumatiza- • Type 3 is a single cell extending from the agger nasi tion extends into the body of the sphenoid beyond the into the frontal sinus. Te internal carotid artery, the most medial of the ophthalmic artery, form the arterial supply of the structure in the cavernous sinus, rests against the lateral frontal sinus. Actual venous drainage for the inner table, however, sphenoid varies from a focal bulge to a serpiginous elevation is through the dura mater and the cranial periosteum for marking the full course of the intracavernous portion of the the outer table. Tese veins are in addition to the diploic carotid artery from posteroinferior to posterosuperior (Figure 2 veins and all venous structures that communicate in the 3-8). In some cases, even without advanced sinus disease, venous plexuses of the inner table, periorbita, and cranial dehiscence in the bony margin can be present, and this should periosteum. Te optic canal is found in the posterosuperior angle Sphenoid Sinus between the lateral, posterior, and superior walls of the sinus, horizontally crossing the carotid canal from lateral to medial Te sphenoid sinuses are located at the skull base at the junc- (see Figure 3-8). Pneumatization of the sphenoid above and tion of the anterior and middle cerebral fossae. Teir growth below the optic canal can result, respectively, in a supraoptic starts between the third and fourth months of fetal develop- recess and an infraoptic recess (the opticocarotid recess). Te ment, as an invagination of the nasal mucosa into the poste- infraoptic recess lies between the optic nerve superiorly and rior portion of the cartilaginous nasal capsule. Pneumatization of the Te canals of two other nerves may be encountered in the sphenoid bone starts at age 3, extends toward the sella turcica lateral wall of the sphenoid sinus, below the level of the 2 by age 7, and reaches its fnal form in adolescence. Te two carotid canal: the second branch of the trigeminal nerve sinuses generally develop asymmetrically, separated by the superiorly through the foramen rotundum and the vidian intersinus bony septum. In some cases, because of this nerve in the pterygoid canal inferiorly (see Figure 3-8). Optic canal Figure 3-8 Simplifed drawing of a lateral wall of the left sphenoid sinus. Optic nerve prominence from anterolateral to posteromedial in the most Carotid canal prominence superior aspect of the lateral wall. Te canals for the second branch of the trigeminal nerve (C) and the vidian nerve (D) can sometimes be endo- scopically identifed and defne the superior and inferior boundaries of the lateral recess (between C and D) in a very pneumatized sphenoid. Rhinologic and Sleep apnea surgi- proaches to the facial skeleton, ed 2, Phila- ment of the relationship between the maxillary cal studies, Zoukaa B. Casiano: delphia, 2006, Lippincott Williams & sinus foor and the maxillary posterior teeth pg 17-26,2007 Wilkins. Som P, Curtin H: Head and neck imaging, ed 5, illary sinus, Arch Otolaryngol 29:640, 1939. Roland Given the intimate association of the external auditory canal of the mandibular fossa and is lined with a thin layer of and middle ear space with the temporomandibular joint, it is cartilage. Disorders of the temporo- is the site of attachment of the sternocleidomastoid, splenius mandibular joint may sometimes present with primarily aural capitis, longissimus capitis, and digastric muscles. A groove in the medial mastoid houses the dural Te peripheral components of the auditory system are sigmoid sinus. Te superior border of the mastoid is the bony housed within or attached to the temporal bone. Te plate that separates the mastoid from the middle cranial auditory system can generally be broken down into several fossa, known as the tegmen mastoideum. During a mastoid- smaller components, including the external ear, the middle ectomy (Figure 4-2), the bone overlying the sigmoid sinus ear and mastoid, the inner ear, and the central auditory and the tegmen are used as landmarks to indicate the poste- system. Also important is the course of the facial nerve within rior and superior limits of dissection. Te arcuate eminence indicates the position of the underlying superior semicircular canal. Medial and anterior Temporal Bone to the superior canal is the facial hiatus, where the greater superfcial petrosal nerve exits the temporal bone to travel on Te temporal bones, which compose a portion of the lateral the superior surface of the petrous bone. Te internal auditory canal is located in this marks identifed during surgical procedures. Te complicated inferior surface of the oriented, fat bone that composes a portion of the lateral petrous bone (see Figure 4-1) includes the carotid canal and skull. Te petrous apex is the most medial portion of and the middle meningeal artery runs in a groove on its the petrous bone, lying medial to the labyrinth. On the anterior, inferior surface of the lateral matized in a minority of patients and otherwise composed of squama, the zygomatic process extends laterally and anteri- bone and marrow. Te zygomatic process is contiguous with a horizontally arising from the undersurface of the temporal bone and oriented structure known as the suprameatal crest or tempo- extending inferiorly. It emanates just anterior to the stylo- ral line, which runs superior to the external auditory canal. Te Te tympanic bone composes the bone of the external squamosa forms the superior and anterior aspects of the auditory canal, the structure of which is discussed in more mandibular or glenoid fossa of the temporomandibular joint. Te anterior tympanic bone forms Te inferior articular tubercle forms the superior boundary the posterior boundary of the glenoid fossa. Lateral semicircular canal Superior semicircular canal Cochlear duct Incus Sigmoid sinus Malleus Stapes Facial n. Mastoid cells Styloid process Figure 4-2 Lateral view of temporal bone, portion of mastoid cortex removed. Petrous part of temporal bone Groove for Internal auditory canal sigmoid sinus Figure 4-3 Medial view of temporal bone. Te auricle begins to form during the sixth week of devel- opment, derived from the frst and second branchial arch.
Smaller studies in single centers performed on surgical and trauma patients have demonstrated positive results in survival and a benefcial effect on glucose homeo- stasis  160mg malegra fxt plus. However 160 mg malegra fxt plus, more recent large multicenter studies performed in mixed patient populations with medical patients have demonstrated adverse outcomes when supra-therapeutic doses of glutamine were administered [38 malegra fxt plus 160mg, 41] malegra fxt plus 160 mg. Most recently , a multicenter trial performed in surgical patients (gastrointestinal , vascu- lar , and cardiac) without renal or hepatic impairment demonstrated neither beneft nor harm with glutamine supplementation when short-term and long-term outcomes were evaluated  . Glutamine may also be used in powder form as part of an early enteral regimen in physiologic doses of 0 . In patients with renal insuffciency , glutamine represents a nonprotein additional nitrogen bur- den and has been demonstrated to be harmful [38, 43]. In addition, there have been concerns that its anabolic effect could be permissive of tumor growth in patients with malignancy. Based on these observations, glutamine should only be given in physiologic doses, early in the post-injury course and withheld in patients with reduced kidney function or malignant tumors. As critical illness is dynamic, caloric and protein requirements can change during its course. Calorie requirements based on resting energy expenditure should be rechecked weekly. Liberalize caloric support with prolonged illnesses to account for accrued defcits. Changes in protein turnover can be monitored with nitrogen balance studies weekly in those patients with adequate kidney function and urine output. Measurement of serum protein in the early phases of critical illness is not indicated, as they refect the infam- matory milieu more than the state of nutritional adequacy . However, as the illness progresses late into the fow phase, prealbumin levels coupled with C-reactive protein values will help determine the adequacy of nutritional support and the return of a more anabolic state . If the patient progresses to a persistent catabolic state despite source control, increased caloric and protein support may be needed. Monitoring should include a daily assessment of the nutrition support that was actually received by the patient with reasonable attempts to minimize calorie and protein defcits. A “therapy bundle” is necessary to overcome the usual barriers of late initiation and loss of support due to frequent interruptions  (Table 15. Volume-based rather than rate-based ordering systems have demonstrated more effective delivery of calories and protein . The volume of feedings required can be given over a cyclic period after feedings are resumed so that the prescribed nutri- tion is delivered. Calorie and protein defcits should be assessed on a daily basis to limit the underfeeding that often occurs. Patients on parenteral nutrition should be monitored for return of gastrointestinal function and their ability to transition to enteral support. An important parameter to follow is adequate wound healing and the development of a robust granulation bed . Keep in mind that inadequate wound healing could also be due to micronutri- ent defciencies. In all patients, routine electrolytes should be monitored and replaced, with a focus on magnesium and phosphorus. While hypomagnesemia may be associated with cardiac dysrhythmias, hypophosphatemia is common in patients with nutri- tional defcits and is associated with decreased respiratory muscle function and weaning failure. The diffculty with this approach is that gastric ileus is often present in patients with an open abdomen. Patients must be carefully selected and monitored closely for toler- ance in an attempt to avoid aspiration . For this reason, current recommenda- tions are to feed continuously or cyclically in a post-pyloric location in open abdomen patients . This route can deliver adequate enteral nutrition more effec- tively and has been shown to be associated with a 30% decrease in the rate of pneu- monia in enterally fed patients . This type of access is technically diffcult, but with expertise, can be achieved at the bedside. As all of these patients are at high nutritional risk, there should be plans made for enteral access at operative procedures. The stability of the abdominal wall must be considered as enteral access can cause fstulae when misplaced or placed too close to the fascial edge (Fig. At the time of follow-up surgery or closure, suturing the stomach to the abdominal wall (Stamm tech- nique) with radiopaque markers can be placed in anticipation for peg placement later when the patient is more stable and anabolic . Note the upper gastric fstula which was caused by a gastrostomy tube placement via the skin fap close to the granulation plate. Fistulae deep in the peritoneal cavity cause peritonitis, and establishing adequate external drainage is more diffcult. Fistulae through or adjacent to a granulated fused visceral block are also problematic . Upon the development of this complication, patients should be started early on parenteral nutrition. There is no need to delay the institu- tion of parenteral nutrition, as it has been reported that 76% of patients will require combination therapy for this illness . As soon as wound management is possible and drainage is adequate, patients should be fed proximally at a trickle rate to start. The early initiation of enteral feedings in open abdomen patients with fstulae (within 14 days) is associated with decreased mortality . Intestinal mapping can be done to give the feasibility of success of proximal feeding and to establish availability of efferent limb for feeding . The efferent limb of the fstula should be evaluated to exclude any leak or obstruction, so that enteral feeding can be started distally via “fstuloclysis” with elemental predigested formu- las or fstula effuent  (see fstuloclysis access in Fig. In addition to aggressive calorie and protein support, support these patients with high doses of minerals and vitamins to replace losses. Zinc, vitamin C, copper, folic acid, and B12 should be monitored and replaced  (Table 15. Nutritional sup- plements that support wound healing with glutamine and arginine can be utilized as long as the patient is not in a state of severe sepsis. In addition, pharmacologic adjuncts are often helpful and include antimotility agents, antisecretory agents, bulking agents, and digestive supplements . Octreotide should not be utilized except for short-term indications when output must be controlled as with skin graft- ing. Because it signifcantly decreases splanchnic and portal blood fow, it can inhibit intestinal rehabilitation  (Fig. Some of these calorically dense formulas, however, may not have adequate protein, so that protein modules are necessary to meet nitrogen require- ments. These can be given even before caloric goals are met to reach protein goals earlier. Because most formulas only contain 65% water, it may be necessary to administer hypotonic enteral fuid boluses in patients without intravenous mainte- nance fuid to avoid dehydration. Nutritional support algorithm Concentrated formulas with more than 1 kcal/mL usually accomplish this goal by increasing fat calories. Do not routinely use formulas with 2 kcal/mL in critically ill patients, as these formulas have high fat content and may promote an infamma- tory response . However, recent animal studies have demonstrated that formulas with more fat calories may mitigate intestinal mucosal injury caused by the air exposure of the open abdomen . Although volume losses are the common sce- nario in the early phases of the open abdomen course, as the patient becomes more chronic, volume restrictions due to underlying illness may become important. These calorically and protein-dense formulas allow adequate nutritional support in patients with these volume restrictions . Patients with intestinal mucosal atrophy, those fed post-pylorically, and patients with gastrointestinal fstulae may require semi-elemental or peptide formulations. The use of immune-modulating formulas with arginine, glutamine, and nucleic acids has been controversial; however, they may be considered for early use in patients without sepsis . There are also commercial products that have increased fber and fat calories for diabetics, formulas that have adjusted electrolyte composi- tion and concentrated calories for renal failure, and those with amino acid and pro- tein adjustments for hepatic insuffciency. These products are far more expensive than the standard enteral products and should not be used without clear indications. Administer a soluble fber product, such as apple pectin or guar gum, routinely to all patients with a colon in continuity. Soluble fber is a source of nutrition for the colonocytes and helps maintain gut barrier function. In addition, soluble fber helps modulate and maintain a healthy colonic microbiome and thus helps to decrease the number of pathogens that may be found in the colons of critically ill patients. The risk can be mitigated by keeping the head of the bed elevated at 30 degrees whenever possible. In patients demonstrating poor gastric emptying, post-pyloric access should be considered. However, whenever there is abdominal distention and evidence of severe feeding intolerance, tube feeding should be immediately decreased or discontinued with the concern for nonocclusive intestinal necrosis. Prompt recognition and surgical intervention for source control are needed for sal- vage from this devastating and highly lethal complication . Dislodgement of percutaneous tubes can result in gastrointestinal contents or tube feeding leaking into the peritoneal cavity. Finally, tube occlusion contributes greatly to underfeed- ing and can be avoided with frequent fushing and appropriate nursing care of feed- ing access tubes. While underfeeding is the most common complication of enteral support, over- feeding is often a complication of parenteral nutrition and has been demonstrated to contribute to adverse outcomes. Overfeeding is associated with increased levels of metabolic stress and is permissive of hepatic steatosis. Associated hyperglycemia is associated with glycosuria, electrolyte derangements, hyperosmolarity, and an increased incidence of infections. This should be treated aggressively by adjusting carbohydrate calories and regulating insulin infusions to maintain blood sugars under 180 mg/dL . Although insulin may be added to the parenteral nutrition formula at 50–60% of the previous day’s requirements, this should only be done in stable patients who are not in fux with insulin resistance and should only cover the caloric load delivered in the parenteral formula. Hypercarbic respiratory failure may be induced by carbon dioxide production from excessive carbohydrate caloric loads. If indirect calorimetry is utilized, the carbohydrate load should be limited to keep the respiratory quotient <1. If indirect calorimetry is not available, the carbohydrate load should be kept to ≤4 mg/kg/min. To decrease the risk of catheter-related sepsis in patients receiving parenteral nutrition, a dedicated access should be utilized for the parenteral nutritional prod- ucts with protection from mixed use. Protocols utilizing alcohol and antibiotic locks can also be used as preventative measures. Take-Home Box • Start enteral feedings in all open abdomens with intestinal continuity as soon as they are hemodynamically resuscitated. A Western Trauma Association multi-institutional study of enteral nutrition in the open abdomen after injury. Effect of immediate enteral feeding on trauma patients with an open abdomen: protection from nosocomial infections. Early enteral nutrition can be successfully implemented in trauma patient with an “open abdomen”. Optimal protein and energy nutrition decreases mortality in mechanically ventilated, critically ill patients: a prospective observational cohort study. Optimization of energy provision with supplemental parenteral nutrition in critically ill patients: a randomized, controlled clinical trial. Proteins and amino acids are fundamental to opti- mal nutrition support in critically ill patients. Altered balance of the aminogram in patients with sep- sis – the relation to mortality. Persistent infammation and immunosuppression: a common syndrome and new horizon for surgical intensive care. Identifying critically ill patients who beneft the most from nutritional therapy: the development and initial validation of a novel risk assess- ment tool. Hypocaloric compared with eucaloric nutritional support and its effect of infection rates in a surgical intensive care unit: a randomized con- trolled trial. Metabolic and nutritional support of the enterocutaneous fstula patient: a 3-phase approach. Can hypocaloric high-protein nutrition support be used in complicated bariatric patients to promote weight loss? Provision of enteral nutrition during vasopressor therapy for hemodynamic instabil- ity– an evidence-based review. High-fat enteral nutrition reduces intestinal mucosal barrier damage after peritoneal air exposure. Specifc intraluminal nutrients alter mucosal blood fow during gut ischemia/reperfusion. Early parenteral nutrition in critically ill patients with short-term relative contra-indications to early enteral nutrition: a randomized controlled trial. Causes and consequences of interrupted enteral nutri- tion: a prospective observational study in critically ill surgical patients. The association between nutritional ade- quacy and long-term outcomes in critically ill patients requiring prolonged mechanical ventila- tion: a multicenter cohort study. Lipid emulsions in parenteral nutrition of intensive care patients: current thinking and future directions. The infuence of parenteral glutamine supplementation on glucose homeostasis in critically ill polytrauma patients – a randomized controlled clinical study. Nutritional support in patients following damage control laparotomy with an open abdomen.
The relationship between these respirophasic changes in stroke volume and position on the Frank–Starling curve can be exploited to make inferences about a patient’s likely response to fluid administration malegra fxt plus 160 mg. A number of metrics to approximate these changes in stroke volume variation have been identified malegra fxt plus 160mg. Thresholds indicating abnormal variation vary by device 160mg malegra fxt plus, but are generally in the range of 10% to 15% 160 mg malegra fxt plus. The higher the degree of variation , the more stroke volume is changing with respiration , and , ultimately , the more likely the patient is to experience an increase in stroke volume with fluid administration . Spontaneous or noninvasive ventilation is associated with a different set of hemodynamic effects , and their relationship to volume responsiveness is being examined. Patients also need to be in a sinus rhythm; atrial fibrillation and frequent ectopy will alter the variation in arterial waveform amplitude independent of respirophasic changes, thereby exaggerating variation. Finally, because such analysis requires patients be synchronous with mechanical ventilation, study patients were generally deeply sedated, if not paralyzed. Another important pitfall to dynamic respirophasic indices is that these measurements do not predict fluid responsiveness in patients with an open chest, which may be becoming95 more frequent after complex cardiac surgery. Some exploit the analysis of the systemic arterial pulse contour, and a range of other modalities such as transesophageal Doppler and bio-reactance exist. Randomized trials of the device in high-risk surgical patients generally show a reduction in complications and improvement in surrogate markers (e. Transesophageal Doppler sonography utilizes a small esophageal probe to monitor descending aortic blood flow velocity continuously. These devices exploit the differential absorption of electrical current by pulsatile blood over time to estimate stroke volume. As the product of anaerobic metabolism, lactate is an indicator of insufficient oxygen delivery to cells. As elevated lactate level decreases, improved perfusion is assumed, and organ function should improve. Clearance of lactate as a goal of resuscitation has been studied recently in patients with septic111 and undifferentiated shock. Although the relationship between measured lactate and 4109 tissue hypoperfusion may not be as direct as it is physiologically intuitive,77 these results suggest that lactate clearance is a reasonable monitoring strategy for the detection and resolution of hypoperfusion. Venous oximetry, or assessment of mixed venous oxygen saturation (SvO ), aims to measure postorgan bed oxygenation as a means to infer the2 oxygen extraction ratio and make further inference about adequacy of oxygen delivery. ScvO is2 2 2 approximately 5 mmHg higher than SvO in critically ill patients, but appears2 to correlate well with SvO during changes in hemodynamic status. Achieving ScvO more than 70% was independently2 associated with improved mortality in a retrospective analysis of sepsis care bundles (the only care factor positively associated with mortality), although79 a much larger and similar analysis did not find the same favorable association between ScvO and mortality. Given the high stakes complexity of hemodynamic and metabolic assessment, the wisest approach is to understand the strengths and weaknesses of many possible strategies, apply the techniques most appropriate to a given patient with an eye toward possible bias, and interpret the information generated within the broader context of the patient’s history, exam, and ever-changing clinical status. Acute Respiratory Failure Acute respiratory failure is characterized by a derangement in pulmonary gas exchange or an imbalance between the work of breathing and respiratory muscle capacity, and is usually accompanied by hypoxemia and/or 4110 hypercapnia. Indeed, in some cases respiratory failure may be caused by “nonrespiratory” issues (e. Suffice it to say that the treatment of acute respiratory failure is primarily supportive, typically necessitates supplemental oxygen, and often requires mechanical ventilation with or without tracheal intubation. Acute respiratory failure typically resolves when the initiating condition is adequately treated. The following subsections will discuss basic principles of mechanical ventilation, some of the more challenging types of respiratory failure, and potential therapeutic approaches to respiratory failure. At its simplest, a preset tidal volume (volume control) or inspiratory pressure (pressure control) and rate provide minimum minute ventilation. Thus, ventilatory modes used today include pressure support ventilation, pressure control ventilation, volume control ventilation, pressure-regulated volume control ventilation, high- frequency ventilation, proportional assist ventilation, airway pressure release ventilation, synchronous intermittent mandatory ventilation, and others. In reality, despite strong regional, local, and individual biases, there is little evidence to suggest that the mode of mechanical ventilation contributes significantly to any major outcome measure, and the choice of mode is at this point largely one of clinician preference. However, evidence suggests that mechanical ventilation may be injurious in certain settings. The use of such “supraphysiologic” tidal volumes (normal resting tidal volumes are 5 to 7 mL/kg) evolved from the 4111 observation that the use of smaller-sized volumes was associated with the development of atelectasis and hypoxemia in anesthetized patients in the operating room. Thus, the ventilatory strategy in these patients should focus on prolongation of the expiratory time, limiting minute ventilation by using low tidal volumes (6 to 8 mL/kg or less) and a low rate (8 to 12 breaths per minute), and by reducing the inspiratory time of the respiratory cycle. In order to decrease inspiratory time, the inspiratory flow rate must increase, and this results in increased peak airway pressure. However, most of the peak pressure is dissipated in the endotracheal tube and large airways, and more importantly, end-expiratory, static or plateau, and mean airway pressures will fall with increased expiratory time. In order to accomplish these goals, deep sedation is often required, and rarely neuromuscular blockade must be used. The adoption of this type of ventilatory strategy in the 1980s and 1990s was associated with a dramatic reduction in mortality due to acute, severe asthma and respiratory failure, from as high as 23% to less than 5%. In addition, because lung volumes correlate with height rather than weight, tidal volume selection should be based on predicted or ideal body weight, rather than actual weight to avoid lung overdistention. These dedicated noninvasive ventilators generate high gas flow, can cycle between a high inspiratory pressure and a lower expiratory pressure, and can sense and respond to patient inspiratory effort. In reality, separation from mechanical ventilation is more a function of the resolution of the cause of respiratory failure, rather than the technique used to withdraw ventilatory support. Thus, the process of separation from mechanical ventilation is expedited when respiratory therapy–driven protocols are used that focus on daily assessment of the ability to breath without assistance, assuming improvement of the inciting process, adequate oxygenation, and hemodynamic stability. These mechanics and gas exchange abnormalities create a challenge in terms of optimizing mechanical ventilation, because maintenance of adequate oxygenation and carbon dioxide elimination are both problematic. In addition, although the ratio of PaO to2 FiO (P/F ratio) does not appear to predict mortality, high dead space2 fraction does, and may reflect the extent of pulmonary vascular injury. Areas of dense opacification are frequently confined to the posterior, dependent portion of the lung, leaving a small, relatively normal, recruitable volume available for ventilation. In regards to the latter, it is critical that tidal volumes and static ventilatory pressures are minimized in order to avoid further injury to the remaining relatively uninjured lung. A large, randomized, prospective trial found that a small tidal volume (6 mL/kg or less) and low static (plateau) airway pressure (≤30 cm H O) resulted in a relative mortality reduction of2 22% when compared to a control group ventilated with tidal volumes of 12 mL/kg. Of these techniques, prone positioning alone is associated with improved survival. However, this intervention is not associated with improved outcomes, as confirmed in a recent meta-analysis. Inhaled vasodilators may be useful as “rescue” therapy in selected patients with severe, refractory hypoxemia, although outcome benefits have not been established. Furthermore, the group receiving methylprednisolone had more ventilator-free days and shock-free days at day 28, in addition to improved oxygenation and respiratory system compliance. The reasons for the lack of improvement in outcome are unclear, but likely include insensitive means for identifying patients with incipient renal failure and lack of effective preventive and therapeutic measures. If contrast must be used, low- or iso-osmolar contrast agents, pre- and postcontrast exposure intravascular volume expansion with saline or sodium bicarbonate solutions, and possibly the use of oral (but not intravenous) N-acetyl cysteine may be useful. Endocrine Aspects of Critical Care Medicine Glucose Management in Critical Illness Hyperglycemia is commonly encountered in critically ill patients and occurs in both diabetics and nondiabetics. Hyperglycemia results primarily because of increased glucose production and insulin resistance caused by inflammatory and hormonal mediators that are released in response to injury. Hyperglycemia may also be aggravated by various therapeutic and supportive interventions, including the use of corticosteroids and total parenteral nutrition. Although the risks of hyperglycemia for patients with diabetes who are ketosis-prone have long been appreciated, hyperglycemia is also detrimental to critically ill patients in a broader sense. Unfortunately, the benefits of the initial trial were not reproduced in multiple subsequent trials, and in fact an increased risk of hypoglycemia and associated harm have been observed. Adrenal Function in Critical Illness The stress response to injury includes an increase in serum cortisol levels in most critically ill patients. The diagnosis of adrenal insufficiency in critical illness is complicated by limitations of commonly used tests of adrenal function. Cortisol is highly protein bound, and serum proteins, including albumin, are commonly depressed in critically ill patients. Although total serum cortisol levels are low in critically ill patients with hypoproteinemia, free cortisol levels are elevated. However, until free cortisol assays are more widely available, the diagnosis of adrenal insufficiency in critical illness must be based on clinical suspicion and total cortisol levels. Evidence for a mortality benefit is unclear, with some trials showing improved mortality and others showing lack of efficacy. A 2015 meta-analysis suggests that there is currently low quality evidence supporting a small mortality benefit with the use of low-dose hydrocortisone (200 to 300 mg/day or equivalent) in sepsis, but that the incidence of metabolic derangements is also increased. There does not appear to be an78 increased risk of gastric ulceration, superinfection, or neuromuscular weakness according to this analysis, but hypernatremia and hyperglycemia are more common in patients receiving steroids. Depression of T4 3 occurs within hours of injury or illness and can persist for weeks. Low4 hormone levels may occur for a variety of reasons, including altered binding and metabolism early in the course of illness, and depressed neuroendocrine function with more prolonged courses. Furthermore, it is not clear whether replacement of thyroid hormones is indicated or beneficial in critical illness. T administration to brain-dead3 organ donors appears to improve hemodynamic stability, although randomized trials have found minimal or no benefit to T or T administration3 4 in patients undergoing cardiopulmonary bypass and cardiac surgery. Larger, randomized prospective trials are necessary to define the role of routine thyroid hormone supplementation in nonthyroidal illness. Importantly, true hypothyroidism may be present in the critically ill, particularly in the geriatric population, and should be considered in the face of refractory shock, adrenal insufficiency, unexplained coma, and prolonged, unexplained respiratory failure. Anemia and Transfusion Therapy in Critical Illness Anemia is a frequent if not obligate accompaniment of critical illness. The cause of anemia in critical illness is multifactorial, and related to blood loss from the primary injury or illness, iatrogenic blood loss due to daily blood sampling, nutritional deficiencies, and marrow suppression. In unstressed subjects, severe anemia (Hb of 5 g/dL or less) is amazingly well tolerated due to physiologic compensations that maintain oxygen delivery and extraction. However, it has long been assumed that critically ill patients have less efficient compensatory mechanisms and reduced physiologic reserve, and thereby require a higher Hb concentration than unstressed individuals. A similar trial in pediatric patients found no mortality difference between restrictive and liberal transfusion strategies, suggesting that a restrictive strategy is safe in critically ill children. Prevention of anemia in critical illness is an appealing alternative to transfusion. As noted earlier, iatrogenic blood loss is a major factor in the development of anemia of critical illness. Another potential approach is the administration of recombinant erythropoietin and iron. Poor nutritional status is associated with increased mortality and morbidity among critically ill patients. Therefore, appropriate nutrition is an important aspect of critical care and adequate nutritional support should be considered a standard of care. Feeding intolerance due to high gastric residual volume can be improved by the administration of gastric prokinetic agents and positioning an enteric tube postpyloric. This effect appears more likely in surgical patients, such as those with burns and those who are in trauma. Specific enteral formulations, particularly those with high concentrations of glutamine, have the strongest data to support their use. Although individual medications frequently provide multiple pharmacodynamic effects, including sedation, analgesia, and anxiolysis, it is helpful to think about these effects separately when selecting medications for an individual patient. For instance, painful procedures such as the insertion of indwelling catheters, endotracheal tubes, and thoracostomy tubes require analgesia, but often do not require anxiolysis or sedation. Conversely, agitated delirium or acute alcohol withdrawal do not require analgesia and are more appropriately treated with sedatives. The patient with an ideal level of sedation and analgesia is at reduced risk for dislodging catheters, removing monitoring devices, or falling out of bed. They are more likely to be synchronous with the mechanical ventilator, which improves oxygenation and reduces the risk of lung injury. They are also better able to participate with care, early mobilization, and physical and occupational therapy. Therefore, it is important to titrate medications according to established therapeutic goals and reevaluate sedation requirements frequently. Features common to all of these scales are the ability to grade sedation over different depths and allow for indicators of agitation. The important point regarding assessment scales for pain, sedation, and delirium is that an assessment utilizing a validated scoring system should be made before and after every intervention to assess progress in achieving treatment goals. However, propofol, midazolam, and dexmedetomidine are the most commonly used hypnotic-anxiolytics. Each of these drugs has its own particular advantages and disadvantages, and detailed discussions of their properties can be found in Chapters 19 and 20. Dexmedetomidine is unique in that its mechanism of action is profoundly different from that of propofol and benzodiazepines. It provides sedation without inducing unresponsiveness or coma, may have some analgesic effects,200,201 and has little affect on respiratory drive. Generally speaking, however, dexmedetomidine is effective for patients who do not require deep sedation (e. Because it does not reliably produce amnesia, it is not appropriate as a solo hypnotic-anxiolytic in patients requiring paralysis. Propofol is generally more effective in these settings, but can cause hypertriglyceridemia and lead to the potentially lethal “propofol infusion syndrome.
Dip the new pads in rehydration buffer or deionized water before placing them in the tray grooves 160mg malegra fxt plus. If run stops malegra fxt plus 160 mg, replace the electrode pads and replenish the mineral oil (cover fuid) to a level no higher than ½ to ¾ height of the tray groove 160 mg malegra fxt plus. Do not turn the machine off until you are ready to collect the peptide fractions as this will cause peptides to migrate back to their starting positions malegra fxt plus 160mg. This is because the electric feld run- ning through the gel also extends into the liquid phase , where the peptides are suspended , thereby ensuring the peptide mol- ecules remain suspended in solution at their respective pI even after the fractionation run is complete . Do not lift the well frames and avoid contaminating the fractions with mineral oil . When collecting fractions , we have) found that leaning the pipette tip against the well frame prevents gel aspiration . Additionally, do not lean over the peptide fraction – sit at a reasonable dis- tance away from the apparatus in order to prevent contamina- tion by other proteins (i. During peptide fractionation, it is normal for some wells to have reduced liquid levels or no liquid in them at all. If there is no liquid visible in a well, simply move on to the peptide recovery step (Step 5 of Subheading 3. Raimondo F, Morosi L, Chinello C, Magni F, Haebel S, Rossel-larsen M, Jakobsen L, Gobom Pitto M (2011) Advances in membranous vesi- J, Mirgorodskaya E, Kroll-kristensen A, Palm‖ cle and exosome proteomics improving bio- L, Roepstorff P (1997) Matrix-assisted laser logical understanding and biomarker discovery. Proteomics Proteomics Method to Identifcation of Protein Profles in Exosomes 153 13(22):3261–3266. Chamley Abstract There is currently no effective method to study multinucleated trophoblast debris extruded from the syncytiotrophoblast into the maternal circulation. In Chapter 9, an in vitro placental explant culture model to generate trophoblast debris was described. Syncytial nuclear aggregates have been observed in the peripheral maternal circulation as early as 6 weeks’ gestation and may play a role in tolerat- ing the maternal immune system during pregnancy. Key words Syncytial nuclear aggregates, Trophoblastic debris, Explant culture, Placenta 1 Introduction Transport of the trophoblast debris from the placenta is known as “trophoblast deportation. He observed large multinucleated trophoblastic fragments trapped in the pulmonary vessels of 14 out of 17 women who had died of eclampsia. These fragments were not observed in the pulmonary circulation of nor- mal pregnant women that had died of other causes, leading Schmorl to propose that this fnding was related to the develop- ment of preeclampsia. It is now accepted that the phenomenon of extrusion of trophoblast debris is a feature of normal pregnancies and that the amount of debris is increased in preeclampsia [2–4]. There are differences in the literature in the nomenclature of the structures referred to here as “syncytial nuclear aggregates. This confusion may arise from the methods of study employed by different researchers. Syncytial knots and syncytial sprouts may represent different popu- lations of multinucleated structures with different functionalities that bud off from the syncytiotrophoblast; however both these structures are defned as histological features of placentae, and the phrases do not refer to the structures that have been extruded from the placenta. Trophoblast deportation is a diffcult phenomenon to study, since thus far there is no effective method to harvest trophoblast debris from the maternal blood in substantial numbers. An in vitro model of trophoblast death and extrusion of trophoblast debris has been established to study the nature of extruded mono- nuclear and multinucleated trophoblast debris and the mechanisms of their clearance in normal and pathological conditions . Placental explants are cultured in Netwell® inserts with 400 μm mesh bottoms, which allows trophoblast debris of a range of sizes to pass into the bottom of the culture well. This model has been utilized to investigate the effect of various factors implicated in the development of preeclampsia on the extrusion of tropho- blast debris from the syncytiotrophoblast [11–14]. Inverted microscope with movable stage that can accommo- date 60 and 35 mm diameter culture plates. Culture placental explants dissected from frst trimester human of Syncytial Nuclear placenta in 6-well plates following the protocol described in Aggregates Chapter 9. Following culture in the appropriate conditions described in the Chapter 9, remove each Netwell® insert containing a pla- cental explant using forceps, taking care to decant as much of the culture medium from around the placental explant as pos- sible back into the well. Pipette to mix the culture medium in each well in order to agitate the trophoblast debris that may have settled at the bot- tom of the culture well. Aspirate the culture medium containing trophoblast debris from two culture wells at a time (3 mL from each well), giving a total volume of 6 mL into a sterile culture dish (dish 1, 60 mm). Turn on the microscope and the micromanipulator system connected to the pneumatic injector system (see Notes 1–3). Attach a glass capillary that has been pulled to create a pointed end to the injection holder (see Note 4). Affx the culture dish (dish 1) containing the cell culture medium with the trophoblast debris securely to the moveable stage of the inverted microscope. Adjust the focus of the inverted microscope so that the large trophoblast debris settled at the bottom of the culture dish is clearly visible. Using the rotating adjustable clamp attached to the injection holder, lower the pointed end of the glass capillary into the center of the culture dish. Centrifuge samples at 17,000 × g at 4 °C for 10 min, remove lysate, and store at −80 °C. This complex is stable and exhibits a strong absorbance at 562 nm, and the color increases in a linear manner with increasing protein concentrations. Incubate the well in the dark at 37 °C for 30 min, and read the absorbance at 562 nm using a spectrophotometer. Tip off block solution, and add 100 μL of primary antibody or irrelevant control antibody to each slide and incubate for 1 h at room temperature. Incubate smears with 100 μL of biotin-conjugated secondary antibody for 1 h at room temperature. Incubate smears with 100 μL of streptavidin-conjugated horseradish peroxidase for 1 h at room temperature. If the tip of the cap- illary is too long, it can be broken off gently prior to autoclav- ing and sterilization. Care must be taken not to aspirate liquid through the capillary into the injection holder and the tubing, which connects the injection holder to the multi-use valve of the pneumatic injec- tor. If this occurs, fush with 70% ethanol and allow to dry overnight before use again. Syncytial nuclear aggregates collected for proteolysis can be stored at −80 °C until proteolysis, thawed on ice, and pooled prior to proteolysis. Syncytial nuclear aggregates collected for immunostaining must be processed and smeared on slides immediately without freezing. Acknowledgment This study was funded by the Marsden Fund of the Royal Society of New Zealand. Schmorl G (1893) Pathologisch-anatomische possible novel immune escape mechanism for Untersuchungen über Puerperal-Eklampsie. Chua S, Wilkins T, Sargent I, Redman C sprouts, apoptosis, and trophoblast deporta- (1991) Trophoblast deportation in pre- tion from the human placenta. J Obstet Gynecol onstrating trophoblast shedding and deporta- 68:611–617 tion during human pregnancy. Mincheva-Nilsson L, Nagaeva O, Chen T, Reprod 12(11):687 Stendahl U, Antsiferova J, Mogren I, Hernestal 11. Placenta 31(1):75 Harvesting and Characterization of Syncytial Nuclear Aggregates 163 12. Chen Q, Viall C, Kang Y, Liu B, Stone P, Chamley L (2012) Phagocytosis of apoptotic Chamley L (2009) Anti-phospholipid antibodies trophoblastic debris protects endothelial cells increase non-apoptotic trophoblast shedding: a against activation. This multinucleated layer regulates gas and nutri- ent exchanges, possesses intensive endocrine functions, and pro- vides immunological support to the fetus. Statistical analysis (paired t-test) was performed using the GraphPad Prism 6 software. The slide can be placed in a dark box or covered with aluminum foil during the incubation period. Wick away excess fuid from the slide and mount the slide with a coverslip 24 mm × 60 mm using Fluoromount-G or other Fluorescent Mounting Medium. Remove any excess mounting medium from around the edges of the coverslip by pipetting or using a wiper, and then seal it with a hardening material such as nail polish to prevent drying and movement under microscope. Store slide on a fat, dry surface protected from light and let stand overnight at 4 °C. The immunofuorescent staining also works with classical sec- ondary antibodies, but the brightness and contrast of the stain- ing are better with the amplifcation method. Fournier T, Guibourdenche J, Handschuh K, blast development downstream of Tead4 and Tsatsaris V, Rauwel B, Davrinche C, Evain- in parallel to Cdx2. McGillick, Stacey Ellery, and Padma Murthi Abstract In recent years ex vivo dual perfusion of the human placental lobule is seeing an international renaissance in its application to understanding fetal health and development. Here, we discuss the methods and uses of this technique in the evaluation of (1) vascular function, (2) transplacental clearance, (3) hemodynamic and oxygenation changes associated with pregnancy complications on placental structure and function, and (4) placental toxicology and post-perfusion evaluation of tissue architecture. Key words Placenta, Perfusion, Methods, Pharmacokinetics, Fetoplacental, Vascular resistance, Structural integrity, Preeclampsia, Off-target effects Overview Ex vivo dual perfusion of the human placenta lobule is the only experi- mental model that presents an opportunity to explore human placental pharmacokinetics, pharmacodynamics, and transplacental clearance of xenobiotics, gases, nutrients, and other endogenous substances [1–10]. It also lends itself to studies of endocrine and vesicle release, immunol- ogy, and vascular resistance in health and diseased states [11–18]. Although variation exists in its methodology detail internationally, most centers conform to the accepted general principles of established dual circulations; homeostasis of temperature, pH, and colloid osmotic pres- sures and osmolality of perfusate; fow rates relative to tissue mass; feto- placental resistance limitations; and transmembrane leakiness thresholds. In this regard, robust evaluation of post-perfusion tissue structure, fol- lowing perfusion of third trimester placenta, has occurred . More recently studies utilizing this technique have focused on oxygen con- sumption  and on the comparative in vivo and ex vivo clearance of paracellular markers for the human placenta . The unique struc- tural, hemodynamic, and functional nature of the human placenta Padma Murthi and Cathy Vaillancourt (eds. The important human placental factors to con- sider here are the hemomonochorial type, with a single continuous syncytiotrophoblast epithelium at the capillary exchanger site; villous maternal blood fow engaging in multi-villous exchange; vascularized fetal blood fow, with sinusoidal capillaries and a continuous endothe- lium; species specifc, infux and effux transporters; and a high collagen content [22–24]. Study themes where the ex vivo placental perfusion model has been employed include (1) transplacental transfer of endogenous sub- stances, oxygen, microbes, parasites, and xenobiotics [2, 6, 25– 29], (2) regulation and dysregulation of fetoplacental vascular tone [12, 30–33], (3) placental infammatory mediation processes , (4) endocrine release [26, 34], and (5) syncytiotrophoblast shed- ding; oxygen transfer and metabolism [20, 35]. This technique has provided a greater understanding of fetoplacental function in pregnancies complicated by (1) preeclampsia , (2) fetal growth restriction , and (3) gestational diabetes . Fetoplacental fow is established frst, within a pair of chorionic plate vessels—one artery and one vein—serving one or more vil- lous trees within an intact lobule of the human placenta. This region is then grossly fow matched on the maternal side, by mim- icking spiral artery fow using one or more cannulas, which is/are simply inserted through the decidual plate to irrigate the intervil- lous space. A physiological salt solution is perfused into each circu- latory system that is isotonic with fetal and maternal blood, with a composition that buffers at pH 7. For successful perfusion experiments, the local arrangements within the clinical research setting should be established, so that midwifery/nursing staff and surgeons understand the need to have the placenta, from recruited cases, handed over for research needs Ex vivo Human Placental Perfusion 175 as soon as possible after delivery, ideally within 10–15 min, so that perfusion can be established within the laboratory within 30 min. Once fetal-side ischemia commences, blood begins to clot within the microcirculation, and cell-free hemoglobin has damaging con- sequences on nitric oxide sequestration and has other irreversible effects through vasoconstriction and infammation . It is also necessary to perform preparatory work the day before perfusion, and a little more on the day of perfusion, prior to placenta collec- tion, inspection, cannulation, and establishment of homeostasis before experimentation. There are key quality control measures, which must be adhered to in the maintenance of tissue structural integrity and in preventing leakage artifact from the fetal to the maternal circulation. Fetomaternal leakage takes two forms: post- partum breakages in the villous tree structure, which provides a route of least resistance for fetal perfusate escape, along a hydro- static pressure gradient and into the intervillous space, and the bulk fow of perfusate through existing paracellular routes when this fetomaternal hydrostatic pressure differential exceeds approxi- mately 30 mmHg [12, 39, 40]. The latter phenomenon is associ- ated with elevated fetal-side infow hydrostatic pressure, which is evoked by prolonged postpartum ischemia, whereby hemostasis leads to platelet activation and irreversible vasoconstriction within the placental microcirculation. Establishing fetal-side perfusion within 30 min, or at least ensuring a fetal-side fush with heparin- ized perfusate in this time period, would normally ensure a basally relaxed fetoplacental microcirculation, preventing fetomaternal leakage to an acceptable level. Fetal-side (and sometimes maternal-side) infow hydrostatic pressure is monitored in real time, to visualize the ease of postisch- emic blood elution within the frst phase of fetal-side perfusion. A steady-state low fetomaternal hydrostatic pressure differential (below 30 mmHg) is preventative of a perfusate fetomaternal “bulk fow” effect and the loss of barrier architectural integrity, whereas a sustained excessive fetal vascular resistance will compro- mise the tissue structural integrity, by vacuolating the vasculosyn- cytial membrane, leading to an increased diffusional pathway length. According to Fick’s law of diffusion, this would otherwise interfere with nutrient transfer effcacy and the accuracy of inter- pretation and in vivo of pharmacokinetics. Fetal-side infow hydro- static pressure is also directly used in experiments designed to assess the regulation of fetoplacental vascular tone, important in the adequacy of provision of fetal blood fow to and from the pla- centa, in the supply of nutrients and oxygen, and in the elimination of waste products of metabolism. Herein, we discuss the methods for ex vivo dual placental perfusion system and uses of this technique to evaluate (1) vascular function, (2) transplacental clearance, (3) hemodynamic and oxy- genation changes associated with pregnancy complications on 176 Paul Brownbill et al. Circulating water bath, set to deliver heated water to the benchtop perfusion chamber, equilibrating to 37 °C, if using. Fetal and maternal peristaltic pumps with appropriate mani- fold tubing ftted to ensure pumps work within their midrange at 6 mL/min and 14 mL/min, respectively, with scope for fetal-side pumps to operate up to 12 mL/min, if investigating fow-mediated vasodilation (see Note 4). Hydrostatic pressure transducers, coupled to a pressure logger and computer with software installed for recording, with real- time screen readout. Gas cylinders and regulators to supply required levels of oxy- gen and carbon dioxide to perfusates. In-line oxygenator system for exchanging oxygen and carbon dioxide to required levels. In-line heat exchanger supplying heated water from a circulat- ing water bath for effective closed circuit perfusion if perform- ing closed-circuit perfusion. A bubble trap for each circuit to prevent non-soluble gases reaching the perfused tissue. A chamber ftted with an oxygen electrode or optode for each circuit to measure oxygen supply to the fetal villous microcir- culation and the maternal intervillous space, plus an additional Ex vivo Human Placental Perfusion 177 Fig. Depicting fetal-side (a) and maternal-side (b) perfusion, the capacity to measure real-time infow hydrostatic pressure as a measure of resistance to fow; pH, which is particularly important in closed-circuit perfusion, ppO2 in the fetal and maternal infow perfusate and the fetal venous perfusate, permitting a measure of tissue oxygen consumption and transfer. An alternative to an oxygenator is through-gassing a perfusate reservoir within a water bath using a sintered gassing tube (for open-circuit perfusion only). Options are available to recirculate perfusate in closed-circuit perfusion with reservoir sampling or send to waste in the open-circuit method with direct sampling. If using the benchtop perfusion system, two perfusate heat exchangers, or equivalent arrangement, one in each circuit, would need to be employed prior to the oxygenator; alternatively, all equipment may be housed within a heated cabinet arrangement to measure the partial pressure of oxygen in the fetal venous perfusate and gauge aerobic metabolism and transplacental oxygen transfer if relevant to the study. A further needle-type oxygen electrode/optode to assess intervillous space oxygen gradient mapping, sampled using a micromanipulator, if relevant to the study. A chamber ftted with a pH electrode for each circuit to enable pH adjustment if employing closed-circuit perfusion.
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