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Virtual endoscopy of the noidal surgery: results of a national survey cheap zithromax 500mg overnight delivery, review of the literature order zithromax 250 mg with mastercard, cerebral ventricles based on 3-D ultrasonography cheap 250mg zithromax mastercard. Pseudoaneurysm Virtual endoscopy combined with intraoperative neuronaviga- of the intracavernous carotid artery following endoscopic endona- tion for planning of endoscopic surgery in patients with occlusive sal transsphenoidal surgery, treated by endovascular approach. Neuroradiology 2002;44: Neurochir (Wien) 2001;143:95–96 279–285 3D Stereoendoscopic Pituitary Surgery* 19 Seth Brown, Vijay K. Schwartz Recent years have seen a rapidly growing interest in both a minimally invasive approach to the tumor with a pan­ endoscopic and robotic surgery, not only in neurosurgery oramic viewing capacity, yet provides the surgeon with and otolaryngology, but also in nearly every surgical feld. The early mimic direct vision, which remains the gold standard in task results of endoscopic pituitary surgery, in terms of length completion. Neurosurgeons performing endoscopic pituitary each movement are afected by the clarity of the visual feed­ surgery are quite familiar with the excellent visualization an back and experience of the surgeon. In endoscopic surgery, endoscope provides because of the ability to bring light to tactile cues must be obtained via long instruments. This, the source of the lesion, as well as the ability to look “around combined with 2D visualization, represents a signifcant the corner” via angled scopes. The acquisi­ dresses some of the limiting factors of traditional transsphe­ tion of endoscopic skills inherently involves the ability to noidal surgery: the long, narrow operative corridor, which translate a 2D image into a mental three-dimensional (3D) limits the feld of view, and the inability to adequately assess representation of a given area. This occurs partially through extension of the pathology behind and around critical neuro­ monocular signals, including variations in color, size, and vascular structures. Despite these advances, conversion of overlap between the various displayed objects. Trained sur­ many neurosurgeons to this technology has been limited, geons also learn to infer spatial relations from haptic cues due partly to the nature of monocular vision of endoscopes. Despite these compensatory fac­ Monocular endoscopes create a two-dimensional (2D) im­ tors, 2D visualization does not match the depth perception age that impairs the surgeon’s perception of depth, spatial aforded by binocular cues, including vergence, stereopsis, relations, and the size of the anatomical structures. This leads to steeper learning curves for trainees, ice and experienced surgeons using 3D as compared with 2D such as residents and neurosurgeons, attempting neuroen­ endoscopes. Depth perception is mance time and error rates in surgical tasks for both resident thought to be critical to precise motor movement. This has and attending surgeons7,14 This appears to be more sensitive been demonstrated in one study that showed the primary as tasks increase in complexity. This works by surgery using a group of practicing skull base surgeons and placing a microscopic array of lenses in front of a single residents performing surgical tasks designed to simulate the video chip on the end of the scope. Hence, as demonstrated in other technology is based on a dual pupil imaging objective and studies, the 3D stereoendoscope makes a more signifcant an image sensor coated by an array of microlenses (a ple­ diference for novice users. The image is created by using a dual pupil laparoscopic surgeons reported improved subjective depth objective that splits light into two paths and a single lens perception but failed to identify any diference in task per­ that then multiplexes these two paths and focuses them formance using 2D versus 3D visualization. These data are processed through a would be in decreasing the learning curve for new users. This provides a natural stereoscopy, which some of the limitations described previously, could become is the two-eyed ability to judge depth, volume, or distance the wave of the future for all endoscopic procedures if de­ accurately. Although the optical resolution of well­designed lenses is generally greater than the resolution of digital image I Three-Dimensional Technology There are several current technologies available that create stereoscopic 3D images. The most widely available is based on dual­channel technology, which incorporates informa­ tion from two distinct perspectives to render a single 3D view, similar to human vision. Another version of this is dual chip-on- the­tip, similarly using a dual­channel video generated by two video chips on a single camera. The main disadvantage that exists with dual­camera technology is related to user side efects, such as fatigue, headache, dizziness, and eye strain, resulting from viewing two images that difer slightly in picture angle, brightness, color, optical distortion, and sharpness. The system also calculates volumetric information that limit the optical resolution. Endoscopes must have a small can be used to create hybrid images with other data sets in­ lens with a high depth of feld and a wide feld of view. The ini­ the endoscope and camera unit and separate light carrier tial endoscopes created with this technology were designed connect directly to the tower and monitor. The resolution for use in laparoscopic surgery and have been approved by of this camera is 800 × 400 pixels with a refresh rate of 50 the Food and Drug Administration for such use. The depth of feld is 15 to 70 mm with the endoscopes were available only as 0­degree endoscopes a feld of view of 70 degrees. Furthermore, the endoscope is of similar profle to display the images in 3D space. Furthermore, although little advantage appears when transitioning from a 2D endoscope to 3D, when con­ Perhaps the most exciting potential of 3D vision is the abil­ verting back to 2D the surgeons have noticed a signifcant ity to see anatomy that is present but not yet visible (i. Future studies will help to better structures deep to the plane of dissection or lying behind Fig. The pituitary gland was dissected from the sur- rounding dura, and the inferior hypophyseal arteries were cut. This would be accomplished by mapping out these critical structures are at potential risk without being in the structures preoperatively on an image­guided system and feld of vision. Specifcally, knowing where the internal ca­ then merging this on the monitor, so that the exact loca­ rotid artery, cavernous sinus, and optic nerve are at all times tion of a structure, such as the internal carotid artery, can could add an extra level of safety to these procedures. This type of image overlay rently available technology such as image­guided navigation provided through fusion of endoscopic and neuronavigation systems and micro-Dopplers can assist in these endeavors. The 3D en- doscopic image (A) and the designated object renderings in the neu- ronavigation software (B) (carotid arteries, circle of Willis, and tumor in this case) are combined to form the real-time endoscopic image C overlay (C). Neurosurgery 2004;55:933–940, discussion Three-dimensional endoscopy may represent the next 940–941 4. The endoscopic versus the technologic frontier in endoscopic anterior skull base and traditional approach in pituitary surgery. The ability to judge depth can only assist 2006;83:240–248 in understanding the location of critical structures. J Neurooncol 2001; more, it will ultimately allow the surgeon to gain better rec­ 54:187–195 ognition of the depth of the tumor to obtain a more complete 6. Finally, in addition to improvement in task comple­ transsphenoidal, transplanum transtuberculum approach for resec­ tion, it will likely decrease the barrier of entry into endoscopy tion of suprasellar lesions. Comparison of two- dimensional and three-dimensional suturing: is there a diference in a robotic surgery setting? Endoscopic pituitary surgery: a second-generation 3D endoscope on the laparoscopic precision of systematic review and meta-analysis. Causes and prevention of laparo­ tions associated with the endoscopic endonasal transsphenoidal ap­ scopic bile duct injuries: analysis of 252 cases from a human factors proach for pituitary adenomas. Curr Biol 1994;4:604–610 dimensional vs three­dimensional camera systems in laparoscopic 12. Infuence of two­dimensional versus three­dimensional imaging on performance three-dimensional vision on surgical telemanipulator performance. Comparison of three-dimensional and two-dimensional laparo­ improves surgical performance for both novice and experienced oper­ scopic video systems. A new 3-D laparoscope in neuroendoscopy: initial descriptions of application to clinical prac­ gastrointestinal surgery.

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Paradoxical breathing is increased by a large thoracotomy or by an increase in airway resistance in the dependent lung buy generic zithromax 500mg on line. Positive-pressure ventilation or adequate sealing of the open chest eliminates paradoxical breathing generic zithromax 250mg amex. The induction of general anesthesia does not cause significant change in the distribution of blood flow buy cheap zithromax, but it has an important impact on the distribution of ventilation. Most of the V enters the nondependent lung, andT this results in a significant V⋅/Q⋅ mismatch. Any reduction in volume in the dependent lung is of a greater magnitude than that in the nondependent lung for several reasons. First, the cephalad displacement of the dependent diaphragm by the abdominal contents is more pronounced and is increased by paralysis. Second, the mediastinal structures pressing on the dependent lung or poor positioning of the dependent side on the operating table prevents the lung from expanding properly. The aforementioned factors will move lungs to a lower volume on the S-shaped volume–pressure curve (Fig. The nondependent lung moves to a steeper position on the compliance curve and receives most of the V , whereas the dependent lung is on the flat (noncompliant) part of theT curve. During inspiration, negative pressure in the intact hemithorax causes the mediastinum to move downward. During expiration, relative positive pressure in the intact hemithorax causes the mediastinum to move upward. However, the upper lung is now no longer restricted by the chest wall and is free to expand, resulting in a further increase in V⋅/Q⋅ mismatch as the nondependent lung is preferentially ventilated, owing to a now increased compliance. During paralysis and positive-pressure ventilation, diaphragmatic displacement is maximal over the nondependent lung, where there is the least amount of resistance to diaphragmatic movement caused by the abdominal contents (Fig. This further compromises the ventilation to the dependent lung and increases the V⋅/Q⋅ mismatch. During two-lung ventilation in the lateral position, the mean blood flow to the nondependent lung is assumed to be 40% of cardiac output, whereas 60% of cardiac output goes to the dependent lung (Fig. Normally, venous admixture (shunt) in the lateral position is 10% of cardiac output and is equally divided as 5% in each lung. Therefore, the average percentage of cardiac output participating in gas exchange is 35% in the nondependent lung and 55% in the dependent lung. During inspiration, movement of gas from the exposed lung into the intact lung and movement of air from the environment into the open hemithorax cause collapse of the exposed lung. The induction of anesthesia has caused a loss in lung volume in both lungs, with the nondependent (up) lung moving from a flat, noncompliant portion to a steep, compliant portion of the pressure–volume curve, and the dependent (down) lung moving from a steep, compliant part to a flat, noncompliant part of the pressure– volume curve. Thus, the anesthetized patient in the lateral decubitus position has most 2578 tidal ventilation in the nondependent lung (where there is the least perfusion) and less tidal ventilation in the dependent lung (where there is the most perfusion). Opening the chest increases nondependent lung compliance and reinforces or maintains the larger part of the tidal ventilation going to the nondependent lung. To this, 5% must be added, which is the obligatory shunt through the nondependent lung. Other considerations that impair optimal ventilation to the dependent lung include absorption atelectasis, accumulation of secretions, and the formation of a transudate in the dependent lung. One-lung Ventilation Absolute Indications for One-lung Ventilation Currently, a variety of thoracic surgical procedures such as lobectomy, pneumonectomy, esophagogastrectomy, pleural decortication, bullectomy, and bronchopulmonary lavage are commonly performed. Customarily, the indications are classified either as absolute or as relative (Table 38-1). The absolute indications include life-threatening complications, such as massive bleeding, sepsis, and pus, in which the nondiseased contralateral lung must be protected from contamination. Bronchopleural and bronchocutaneous fistulae are absolute indications because they offer a low-resistance pathway for the delivered V duringT positive-pressure ventilation. A giant unilateral bulla may rupture under positive pressure, and ventilatory exclusion is mandatory. Finally, during bronchopulmonary lavage for alveolar proteinosis or cystic fibrosis, prevention of drowning the contralateral lung is necessary. Improvements in video-endoscopic surgical equipment and a growing enthusiasm for minimally invasive surgical approaches have contributed to its use. The lung should be well collapsed to provide the surgeon with an optimal view of the surgical field, and to facilitate palpation of the lesion in the lung parenchyma. In addition, it is difficult to place the stapler on a lung that is not completely collapsed, and there is an increase in incidence of postoperative air leak in these circumstances. In some institutions, 80% to 90% of the procedures are now performed using the thoracoscopic approach. Typical values for fractional blood flow to the nondependent and dependent lungs, as well as PaO2 and Q⋅S/Q⋅t for the two conditions, are shown. The Q⋅S/Q⋅t during two-lung ventilation is assumed to be distributed equally between the two lungs (5% to each lung). The 35% of total flow perfusing the nondependent lung, which was not shunt flow, was assumed to be able to reduce its blood flow by 50% by hypoxic pulmonary vasoconstriction. Upper lobectomy, pneumonectomy, and thoracic aortic aneurysm repair are high-priority indications. These procedures are technically difficult, and optimal surgical exposure and a quiet operative field are highly desirable. Nevertheless, many surgeons are accustomed to operating with the lung collapsed for these cases. These procedures include minimally invasive cardiac surgery, lung volume reduction, thoracic aneurysm repair, thoracic spinal procedures, mediastinal mass resection, thymectomies, and mediastinal lymph node dissection. It is important to distinguish between the need for lung isolation versus lung separation. Whenever the nondiseased lung is threatened with contamination by blood or pus from the diseased lung, the lungs must be isolated to prevent potentially life-threatening complications. Other indications are bronchopleural and bronchocutaneous fistulas because they offer a low-resistance pathway for the delivered V during positive-pressureT ventilation. Finally, during bronchopulmonary lavage for alveolar proteinosis or cystic fibrosis, protection of the contralateral lung from drowning is necessary. These situations, however, are relatively uncommon and in modern anesthesia practice constitute less than 10% of all thoracic procedures. This includes all the relative indications that are primarily for surgical exposure. One lumen is long enough to reach a main stem bronchus, and the second lumen ends with an opening in the distal trachea. Lung separation is achieved by inflation of two cuffs: A proximal tracheal cuff and a distal bronchial cuff located in the main stem bronchus (see “Positioning Double-lumen Tubes”). The endobronchial cuff of a right-sided tube is slotted or otherwise designed to allow ventilation of the right upper 2582 lobe because the right main stem bronchus is too short to accommodate both the right lumen tip and a right bronchial cuff. This tube design has the advantages of having D-shaped, large-diameter lumens that allow easy passage of a suction catheter, offer low resistance to gas flow, and have a fixed curvature to facilitate proper positioning and reduce the possibility of kinking.

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Long- term options include fully implantable devices that are placed in the patient’s abdominal cavity with only the control lines exiting the body and can allow patients to return of the activities of daily living buy zithromax 100 mg with amex. This device is composed of a single-use centrifugal pump generic zithromax 100 mg amex, a motor cheap 500 mg zithromax amex, and a primary drive console. Using a bearingless magnetically levitated impeller, it provides continuous flow via a centrifugal-type rotary blood pump. The pump can rotate at speeds of 1,500 to 5,500 rpm and can provide flow rates of up to 9. It can be placed either percutaneously or via a cut down in either the femoral or axillary artery. In addition to standard monitoring, preinduction arterial blood pressure monitoring is essential. The ablation of high sympathetic tone that heart failure patients possess may be catastrophic and cause cardiac arrest on the induction of anesthesia. As such, agents that maintain hemodynamic stability are chosen for these patients. These include the use of etomidate as an induction agent (due to its lack of vasodilatation and myocardial depression) and a careful “balanced technique. One caveat is that, due to the slow circulation times in heart failure patients, care must be taken to allow medications time to circulate and reach the desired effect. A good rule of thumb is that a 20% decrease in blood pressure should be treated using a direct acting agent such as phenylephrine or norepinephrine. This allows for a margin of safety and may prevent profound hypotension due to the long circulation time if the blood pressure is treated only as the patient becomes hypotensive. In each case, maintenance of adequate preload is essential for proper device function. Once the failing ventricle is mechanically supported, the “cardiac output” of that chamber(s) is dependent upon adequate preload to fill the device and normal to low vascular resistance to promote forward flow and provide adequate systemic perfusion. Patients with fully implantable devices should be considered at risk for 2738 pulmonary aspiration and treated accordingly. Postcardiopulmonary Bypass Continued vigilance is mandatory during decannulation, protamine administration, “drying up,” and chest closure. Transient atrial or junctional dysrhythmias may be caused by removal of the atrial cannulae. Heparin is reversed with protamine following removal of the venous cannulae, whereas the arterial return cannula remains in place for transfusion of blood to the systemic circulation as needed. When this is completed and bleeding is controlled the arterial cannula is removed, and if bleeding is considered to be under control the chest is closed. During decannulation, the possibility exists for unexpected bleeding from the atrial or aortic suture lines, and this sometimes requires rapid transfusion. Reversal of Anticoagulation Protamine, a polycationic protein derived from salmon sperm, is used to neutralize heparin. Some use a fixed ratio of protamine to heparin, others use 1-mg protamine to 100-U heparin, and still others look to automated protamine titrations to suggest the initial dose. Regardless of the method selected, further requirements are assessed by repeated measures of the activated coagulation time or other clotting assay(s), as well as by the appearance of the surgical field. True anaphylaxis is rare and characterized by increased airway pressure, vasodilation with systemic hypotension, and skin flushing. Increased incidence of reactions has been reported in patients sensitized to protamine from previous cardiac catheterization, hemodialysis, cardiac surgery, or exposure to neutral protamine Hagedorn insulin. This complication, which may occur in approximately 1% of patients, is mediated by release of thromboxane and C5a anaphylatoxin. Because systemic hypotension is more likely with rapid injection of protamine, slow administration into a peripheral venous site is advisable. The usual causes include inadequate surgical hemostasis or reduced platelet count or function, and neither is identified by a prolonged activated coagulation time. Insufficient doses of protamine, dilution of coagulation factors, thrombocytopenia, and platelet dysfunction, and rarely “heparin rebound,” belong in the differential diagnosis. Blood product transfusion based on point of care testing has been proven effective in treating nonsurgical bleeding. This is occasionally associated with transient decreases in blood pressure, which usually respond to volume infusion. If hypotension persists, the chest should be reopened to rule out cardiac tamponade, a kinked coronary bypass graft, or other problems. Medicated infusions must be maintained, as clinically indicated, with portable infusion pumps. Avoidance of aortic manipulation and cross-clamping especially in elderly patients is associated with lower stroke rates. The development of retractors and stabilization devices allows the surgeon to operate on the beating heart without causing arrhythmia or hypotension. Other advances include the use of intracoronary shunts and sutureless anastomotic devices. Alternate incisions tutored as “minimally invasive” provide limited exposure and increase surgical difficulty. A type of minimally invasive cardiac surgery uses port access technology, with the assistance of a robotic system. A period of single-lung ventilation may be required under capnothorax for insertion of surgical access ports. The hemodynamics are monitored constantly and rapid intervention is needed in the face of changing hemodynamics. In addition, displacement of the heart may cause falsely elevated central venous and pulmonary pressures despite the presence of hypovolemia. Direct observation of the heart and communication with the surgeon are critical in managing hemodynamic swings. Pre-existing high-grade lesions might have caused formation of collateral circulation, which may ameliorate potential ischemia. Right coronary lesions will predispose to bradycardia, atrial dysrhythmias, and heart block. For these reasons, immediate access to cardiac pacing and cardioversion are essential. Left-sided coronary lesions 2741 may cause malignant ventricular dysrhythmias and hemodynamic collapse. These include optimizing preload prior to positioning, judicious use of inotropes and α-agonists, and placing the patient in Trendelenburg position, which allows redistribution of intravascular volume to support the heart in the vertical position. Normothermia contributes to early extubation as well as prevention of coagulopathy. Aggressive pain control improves patient satisfaction and contributes to early extubation. Regional techniques including thoracic epidurals and neuraxial narcotics are used with great success, although anticoagulation is a concern in patients with central regional anesthetics. Postoperative Considerations Bring Backs Postoperative re-exploration is needed in 4% to 5% of cases.

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Causes of hypomagnesemia can be divided into four broad categories: decreased intake purchase genuine zithromax line, gastrointestinal loss generic zithromax 100mg without prescription, renal loss order zithromax overnight delivery, and redistribution. Nutritional hypomagnesemia can result from malabsorption syndromes in patients receiving parenteral nutrition, and it is also present in 25% of alcoholics. Redistribution occurs with acute pancreatitis, administration of catecholamines, and “hungry bone syndrome” after parathyroidectomy. Clinical manifestations of hypermagnesemia (>4 to 6 mg/dL) are serious and potentially fatal. Minor symptoms include hypotension, nausea, vomiting, facial flushing, urinary retention, and ileus. In more extreme cases, flaccid skeletal muscular paralysis, hyporeflexia, bradycardia, bradydysrhythmias, respiratory depression, coma, and cardiac arrest may occur. Although mild hypermagnesemia in the setting of normal renal function can be treated with supportive care and withdrawal of the cause, in some cases dialysis is necessary. Phosphorus is a major intracellular anion that plays a role in regulation of glycolysis, ammoniagenesis, and calcium homeostasis and is an essential component of adenosine triphosphate and red blood cell 2,3- diphosphoglyceric acid synthesis. Hypophosphatemia is clinically more important than hyperphosphatemia and can result in symptoms including muscle weakness, respiratory failure, and difficulty in weaning critically ill patients from mechanical ventilation when serum levels are less than 0. In addition, low phosphate levels may diminish oxygen delivery to tissues and rarely cause hemolysis. Hypophosphatemia can result from intracellular redistribution (from catecholamine therapy), from inadequate intake or absorption secondary to alcoholism or malnutrition, or from increased renal or gastrointestinal losses. Hyperphosphatemia (>5 mg/dL) is generally related to accompanying hypocalcemia although increased phosphate levels may also lead to calcium precipitation and decreased intestinal calcium absorption. Significantly elevated serum phosphate levels are most commonly due to reduced excretion from renal insufficiency but can also result from excess intake or redistribution of intracellular phosphorus. Treatment of chronic hyperphosphatemia includes dietary phosphate restriction and oral phosphate binders. Conditions that cause an increase in negatively charged ions other than bicarbonate and chloride (e. The usual compensatory response to all types of metabolic acidoses is hyperventilation, which leads to a partial pH correction toward normal. Thiazides and loop diuretics 3 both induce a net loss of chloride and free water and can cause a volume “contraction” alkalosis. The kidneys continue to adapt to the+ increased pH through greater titratable acid excretion (e. Mixed Acid–Base Disorders It is not uncommon for a metabolic derangement to coexist with a respiratory derangement, particularly in critically ill patients. A general approach to the diagnosis of mixed acid–base disorders requires a stepwise approach that begins with a focused history and physical examination. It is associated with a decline in glomerular filtration and results in inability of the kidneys to excrete nitrogenous and other wastes. Even studies that advocate the use of extracorporeal32 technology report mortality of between 50% and 70%. There are many pathophysiologic similarities between the various causes of kidney injury. The metabolically active cells of the medullary thick ascending limb of the loop of Henle are especially vulnerable to hypoxic damage because of their relatively high oxygen consumption. Nephrotoxins often act in concert with hypoperfusion or underlying renal vasoconstrictive states to damage renal tubules or the microvasculature. Several common nephrotoxins, some of which are difficult to avoid in a hospitalized patient population, are listed in Table 50-1. The obstructing lesion may occur at any level of the collecting system, from the renal pelvis to the distal urethra. Intraluminal pressure rises and is eventually transmitted back to the glomerulus, thereby reducing glomerular filtration pressure and rate. Nephrotoxins may take the form of drugs, nontherapeutic chemicals, heavy metals, poisons, and endogenous compounds (Table 50-1). These diverse groups of renal toxins share a common pathophysiologic characteristic: They disturb either renal oxygen delivery or oxygen utilization and thereby promote renal ischemia. Antimicrobial and chemotherapeutic–immunosuppressive agents are effective because they are cellular toxins. When these drugs are filtered, reabsorbed, secreted, and eventually excreted by the kidney, toxic concentrations in renal cells can be reached. The aminoglycoside antibiotics and amphotericin B are particularly difficult to avoid because they are effective antimicrobials, with few available alternatives. Their effect can be additive with other nephrotoxic factors causing impairment of kidney function. Hypovolemia, fever, renal vasoconstriction, and concomitant therapy with other nephrotoxic agents should be avoided wherever possible. Electrolyte disorders such as hypercalcemia, hypomagnesemia, hypokalemia, and metabolic acidosis can further enhance nephrotoxic damage to the kidney. Cyclosporin A and tacrolimus are indispensable components of many immunosuppressive drug regimens, but in combination with other nephrotoxins and clinical factors, they can cause acute and exacerbate chronic 3527 kidney injuries in transplant recipients. Radiocontrast dye has effects on renal49 function that develop 24 to 48 hours after exposure and peak at 3 to 5 days. Myoglobin seems to be a more potent nephrotoxin than hemoglobin because it is more readily filtered at the glomerulus and can be reabsorbed by the renal tubules, where it chelates nitric oxide and thus induces medullary vasoconstriction and ischemia. These goals may be accomplished by expanding the intravascular fluid volume with crystalloid infusion, stimulating an osmotic diuresis with mannitol, and increasing the urine pH with intravenous bicarbonate therapy. Though high-quality evidence is lacking, forced mannitol-alkali diuresis is recommended as the second step in the preventive treatment of myoglobinuria, with urine flow rates of up to 300 mL/hour and a urine pH above 6. However, peak fluoride levels during administration of these agents seldom reach toxic levels, and there are few reports describing volatile agent–induced nephrotoxicity. The potential of sevoflurane-induced nephrotoxicity has56 been related to the production of compound A during prolonged, low-fresh- gas-flow sevoflurane anesthesia. Although there are insufficient data to57 conclude that sevoflurane-induced kidney injury occurs in the human population, even during low-gas-flow anesthesia, it is probably prudent to maintain a fresh gas flow of at least 2 L/min during sevoflurane anesthesia. Evidence of increased rates of renal replacement therapy in critically ill and septic patients receiving hydroxyethyl starches resulted in the elimination of these fluids from routine clinical practice. Thus, optimal63 fluid management in the perioperative period, in both the type and amount of fluid, has significant effects on renal function. Patients with decreased renal reserve are often asymptomatic and frequently do not have elevated blood levels of creatinine or urea. It results in inability of the kidney to perform its two major functions: regulation of the volume and composition of the extracellular fluid and excretion of waste products. Situations predisposing patients with renal failure to hyperkalemia are presented in Table 50-2. Both render patients susceptible to an endogenous acid load such as may occur in shock states, hypovolemia, or with an increase in catabolism. Cardiovascular complications of the uremic syndrome are primarily due to volume overload, high renin–angiotensin activity, autonomic nervous system hyperactivity, acidosis, and electrolyte disturbances. Together with volume overload, acidemia, anemia, and possibly the presence of high-flow arteriovenous fistulae created for dialysis access, hypertension may contribute to the development of myocardial dysfunction and heart failure.