By Y. Kalesch.
In this system order genuine levitra on line impotence remedy, V is small (50 to 80 mL) generic levitra 20mg with amex erectile dysfunction treatment lloyds,T and gas exchange occurs through enhanced molecular diffusion and coaxial airway flow. PaO2 increased compared with that obtained during simple collapse of the nondependent lung. Another advantage of high- frequency ventilation is that the rapid-rate small V can be delivered throughT 2632 small tubes or catheters so if an airway has to be divided, the passage of a small tube across the surgical field permits ventilation of the distal airway and lung tissue. This use has been applied during sleeve resection of the lung, tracheal reconstruction, and surgery for tracheal stenosis. In all three situations, the surgeon is able to work easily around the small catheter used to provide the high-frequency ventilation. Drainage is performed with the patient sitting up and leaning toward the affected side. Supplemental oxygen should be administered, and the patient should be constantly reassured. Neuroleptanalgesia is satisfactory in providing a suitably cooperative patient, and the airway is then pretreated with topical anesthesia. Selection of the largest possible tube provides a close fit in the trachea, which helps stabilize the tube. Once the tube is adequately positioned in the trachea, there may be a considerable outpouring of pus from the tracheal lumen if an empyema is present; therefore, this lumen should be immediately suctioned using a large-bore suction catheter. The healthy and possibly the affected lung may then be ventilated; adequacy of oxygenation and ventilation is assessed by pulse oximetry and arterial blood gas analysis. With either technique, the chest drainage tube must be left unclamped to avoid any bouts of coughing and to prevent the buildup of a tension pneumothorax in the event that a predisposing valvular mechanism exists. A rapid-sequence induction with ketamine or propofol followed by a relaxant has also been described, but is associated with considerable risk of contamination and tension pneumothorax. The use of small V results in minimal gas loss through the fistula, which may healT more quickly. In addition, hemodynamic effects are usually minimal and spontaneous efforts at ventilation are usually abolished, thereby decreasing the work of breathing and eliminating the need for relaxants or excessive sedation. Lung Cysts and Bullae Air-filled cysts of the lung are usually bronchogenic, postinfective, infantile, or emphysematous. A bulla is a thin-walled space filled with air that results from the destruction of alveolar tissue. The walls are, therefore, composed of visceral pleura, connective tissue septa, or compressed lung tissue. In general, bullae represent an area of end-stage emphysematous destruction of the lung. Patients may be considered for surgical bullectomy when dyspnea is incapacitating, when the bullae are expanding, when there are repeated pneumothoraces owing to rupture of bullae, or if the bullae compress a large area of normal lung. If the bulla or cyst communicates 2634 with the bronchial tree, positive-pressure ventilation may cause it to expand or even to rupture, if it is compliant, producing a situation analogous to tension pneumothorax. Nitrous oxide should be avoided because it causes expansion of any air spaces in the body, including bullae. Once the chest is open, even more of the V may enter the compliant bulla,T which is no longer limited by chest wall integrity, and an increase in ventilation is needed until the bulla is controlled. The anesthetic management of these patients is challenging, particularly if the disease is bilateral. The avoidance of positive-pressure ventilation (when possible) helps decrease the likelihood of the potential problems described previously, although oxygenation may be precarious with spontaneous ventilation. Once the endotracheal tube is in place, each lung may be controlled separately, and adequate ventilation can be applied to the healthy lung if bilateral disease is not present. Gentle positive-pressure ventilation with rapid, small V and pressures not to exceedT 10 cm H O may be used during the induction and maintenance of anesthesia,2 especially if the bullae have been shown to have no or only poor bronchial communication by preoperative ventilation scanning. While the surgery is being performed, as each bulla is resected, the operated lung can be separately ventilated to check for air leaks and the presence of additional bullae. If positive-pressure ventilation is to be applied before the chest is opened, the possibility of a tension pneumothorax must be kept in mind, and treatment should be readily available. The diagnosis of pneumothorax may be made by a unilateral decrease in breath sounds (this may be difficult to distinguish in a patient with bullous disease), increase in ventilatory pressure, progressive tracheal deviation, wheezing, or cardiovascular changes. Alternatively, general anesthesia is induced only after the surgeon has prepared the operative field and draped the patient. In the event of sudden deterioration in the patient’s condition during induction, the surgeon may perform an immediate median sternotomy. In any event, the time from induction of anesthesia to sternotomy must be kept to a minimum. The side with the largest bulla and least lung function, as assessed before surgery by ventilation and perfusion scans, should be operated on first. Unlike most cases of pulmonary resection, patients after bullectomy are left with a greater amount of functional lung tissue than was previously available to them, and the mechanics of respiration are improved. During this time, the positive airway pressure used should be minimized to avoid causing a pneumothorax owing to rupture of suture or staple lines or of residual bullae. Anesthesia for Resection of the Trachea Tracheal resection and reconstruction are technically difficult for the surgeon and challenging for the anesthesiologist. Indications for this type of procedure include congenital lesions (agenesis, stenosis), neoplasia (primary or secondary), injuries (direct or indirect), infections, and postintubation injuries (caused by an endotracheal tube or tracheotomy). For the surgical team, the major problems are maintenance of ventilation to the lungs while the airway is being operated on and postoperative integrity of the anastomoses. In this respect, the presence of lung disease sufficiently severe to require postoperative ventilatory support is a relative contraindication to tracheal resection or reconstruction. Monitoring of these patients should include placement of an arterial cannula in the left radial artery to permit continuous measurement of blood pressure during periods of innominate artery compression. Numerous methods have been reported to provide oxygenation and ventilation of the lungs during these procedures. A small-bore anode tube may be placed through and distal to an upper tracheal lesion so resection may occur around the tube. Alternatively, an endotracheal tube may be passed through the glottis to above the stenosis, and a sterile endotracheal or bronchial tube may later be inserted into the trachea opened distal to the site of stenosis, with the sterile anesthesia tubing being led across the surgical field. After resection of the lesion, the sterile and distally placed endotracheal tube is withdrawn, and the 2636 upper tube (originally passed through the glottis) is advanced across the anastomosis. During these procedures, the patient is kept in a head-down position to minimize aspiration of blood and debris into the alveoli, and ventilation must be carefully monitored throughout the procedure. Clearly, the presence of a large-bore tube in the airway may make these resections technically difficult, and the use of high-frequency ventilation techniques may improve surgical access. Potential disadvantages of these high-frequency ventilation techniques are that, by necessity, the system is “open” (see “High-frequency Ventilation”), and egress of gas during exhalation may be compromised if the stenosis is tight.
The abdominal aorta is the most frequent location of arterial aneurysm and is approximately nine times more common than a thoracic aortic aneurysm discount levitra 20 mg with amex erectile dysfunction definition. Thoracic aortic aneurysms are discussed in more detail in Chapter 39 (Anesthesia for Cardiac Surgery) order levitra 10 mg with mastercard erectile dysfunction questions to ask. Though many of the risk factors are shared between the two processes, the pathophysiology of aortic aneurysm formation is distinct from atherosclerotic disease. Aortic aneurysm formation is a degenerative process involving the degradation of aortic wall connective tissue (primarily, the medial and adventitial layers), inflammation and immune responses, and biomechanical wall stress. A prospective study followed 300 consecutive patients who were initially managed nonoperatively. The 6-year cumulative incidence of rupture was 1% in patients among patients with aneurysms less than 4. Acute aortic dissection is a life-threatening medical catastrophe that is 2797 associated with very high rates of morbidity and mortality. Acute dissections are those in which clinical symptomatology has lasted fewer than 14 days. Approximately half of aortic dissections originate from the ascending aorta; ascending aortic aneurysms are a surgical emergency. Death from an ascending aortic aneurysm is usually due to acute aortic regurgitation, pericardial tamponade, or myocardial ischemia secondary to coronary ostial compromise. The next most common site of origin is just distal to the left subclavian artery, in the vicinity of the ligamentum arteriosum. Uncomplicated descending aneurysms may be managed medically, whereas complicated (i. Figure 40-11 Cumulative incidence of abdominal aortic aneurysm rupture, according to aneurysm diameter at diagnosis. The most dramatic and consistent effect of aortic cross-clamping is an increase in systemic vascular resistance and mean arterial pressure as a result of the sudden impedance to aortic flow. The extent to which afterload increases depends upon the level the cross-clamp applied. Infrarenal cross- clamping may increase arterial blood pressure 2% to 10%, where as a supraceliac clamp has a significantly greater effect and may increase the mean arterial pressure up to 50% (Table 40-2). A complex interaction between splanchnic venous tone, blood volume redistribution, coronary blood flow, and myocardial contractility may result in an increase or decrease in cardiac preload, central filling pressures, and cardiac output (Fig. Placement of the aortic cross-clamp results in blood volume redistribution proximal to the clamp placement. Infraceliac cross-clamping is relatively well tolerated compared with supraceliac cross- clamping. With lower clamping, blood volume can shift into the compliant splanchnic vasculature, thus limiting preload changes. With the placement of a supraceliac cross-clamp, the splanchnic circulation is unable to absorb this shift in blood volume. Instead, the decrease in splanchnic arterial flow is associated with a decrease in venous capacitance as a result of elastic recoil. The net result is an increase in venous return, central filling pressures, and cardiac output. The increase in preload and afterload increases myocardial work, which in turn leads to coronary vasodilation to maximize coronary blood flow and oxygen delivery. Despite a decrease in ejection fraction, cardiac output and stroke volume increased by expanding the cavity size of the left ventricle. The most dramatic and consistent effect of aortic cross- clamping is an increase in systemic vascular resistance and mean arterial pressure as a result of the sudden impedance to aortic flow. A pragmatic approach is to initially use esmolol to decrease heart rate to a target of around 60 to 65 beats per minute. This can be accomplished via bolus (+/− continuous infusion) of intravenous vasodilating agents (e. The goal is to offset the increase in afterload and myocardial work with systemic vasodilation. It is important to recognize that attempts to normalize systemic vascular resistance above the level of the clamp can even further compromise blood flow distal to the clamp. The administration of sodium nitroprusside has been shown to decrease aortic pressure distal to the level of cross-clamp placement; this decrease was unresponsive to increases in preload via volume challenge or cardiac output. Even if the initial aortic clamp was supraceliac, the anastomosis is most commonly infrarenal. Once the proximal anastomosis is made, the clamp is moved from native aorta to graft in order to allow reperfusion of the celiac and renal beds. This is usually hemodynamically insignificant due to the relatively short duration of ischemia and rapid reapplication of the cross-clamp distal to the visceral vessels until the distal anastomosis (or, in the case of bifurcated graft, anastomoses) are complete. The subsequent release of the distal clamp(s) results in the release of inflammatory mediators, decreased cardiac output, hypoxemia-mediated vasodilation, and a reactive hyperemia that ultimately culminates in profound vasodilation and arterial hypotension (Fig. A relative central hypovolemia develops as blood pools in tissue distal to the cross-clamp. Various therapies have been employed to counteract this response, with no evidence to suggest superiority of one method over another. Most anesthesiologists employ some degree of volume loading during the period of cross-clamp application. Vasoconstrictors such as phenylephrine or norepinephrine, or inotropic agents such as epinephrine or calcium chloride are frequently employed in conjunction with volume loading. It may also be prudent to decrease anesthetic depth and/or discontinue epidural infusions in anticipation of these predictable changes. Preferable to pharmacologic manipulation is a gradual release of the cross- clamp to allow for a slow, controlled release of vasoactive and cardiodepressant mediators. If bilateral iliac clamps are employed, the lower extremities can be reperfused sequentially to allow for a more controlled release and appropriate resuscitation. Clear communication with the vascular surgeon is vital to coordinate appropriate management. For example, bleeding at the anastomosis requires immediate reclamping; if vasopressors and inotropes are administered as boluses and then the clamp is reapplied, profound proximal hypertension can ensue. Passive venous recoil distal the aortic cross-clamp results in a shift in blood volume from distal to the aortic occlusion to proximal to the occlusion. If the aorta is occluded above the level of the celiac axis, the splanchnic reserve is redistributed to the organs and tissues proximal to the clamp. If an infraceliac cross-clamp is placed, the blood volume may shift into the splanchnic system in addition to other organs proximal to the clamp. The ability to shift into or out of the splanchnic vasculature accounts for variability in preload augmentation. Preoperative renal dysfunction is the most powerful predictor of postoperative renal dysfunction. There is no proven renal protective strategy other than minimizing the length of ischemia and avoidance of profound or prolonged hypotension.
Increased awareness of fire hazards in the operating room environment further reinforces the need for careful monitoring of FiO2 in pediatric anesthesia order cheap levitra line doctor yourself erectile dysfunction. Tonsillectomy and adenoidectomy purchase 20mg levitra with visa zopiclone impotence, among the most common of surgical procedures in the pediatric anesthesia population, carry an increased risk of airway fire. In addition to using of cuffed endotracheal tubes, careful monitoring and maintenance of a decreased inspired oxygen concentration whenever electrosurgical equipment is in use may decrease airway fire risk in these patients. The oxygen9 2 saturation (SaO ) of hemoglobin (as a percentage) is related to the2 oxygen tension (as a partial pressure, mmHg) by the oxyhemoglobin dissociation curve. On the steep part of the curve, a predictable correlation exists between SaO2 and partial pressure of oxygen (PaO2). In this range, the SaO2 is a good reflection of the extent of hypoxemia and the changing status of arterial oxygenation. For PaO2 greater than 75 mmHg, the SaO2 reaches a plateau and no longer reflects changes in PaO2. Coexisting medical conditions, such as hypercapnia, acidosis, and hyperthermia, cause the oxyhemoglobin dissociation curve to shift to the right and decrease the affinity of hemoglobin for oxygen. This change favors the unloading of oxygen from hemoglobin to peripheral tissues, as shown in Figure 26-1. The change in color results from the optical properties of hemoglobin and its interaction with oxygen. The ratio of oxyhemoglobin (HbO ) and hemoglobin (Hb) can be2 determined by absorption spectrophotometry. Oxygen saturation is determined by spectrophotometry, which is based on the Beer–Lambert law. At a constant light intensity and hemoglobin concentration, the intensity of light transmitted through a tissue is a logarithmic function of the oxygen saturation of Hb. Light-emitting diodes in the2 pulse sensor emit red (660 nm) and near infrared (940 nm) light. The percentage of HbO is determined by measuring the ratio of infrared and red2 light sensed by a photodetector. Pulse oximeters perform a plethysmographic analysis to differentiate the pulsatile “arterial” signal from the nonpulsatile signal resulting from “venous” absorption and other tissues, such as skin, muscle, and bone. The relationship between arterial saturation of hemoglobin and oxygen tension is represented by the sigmoid-shaped oxyhemoglobin dissociation curve. When the curve is left-shifted, the hemoglobin molecule binds oxygen more tightly. The appropriate use of pulse oximetry necessitates an appreciation of both physiologic and technical limitations. Despite the numerous clinical benefits of pulse oximetry, other factors affect its accuracy and reliability. Factors that may be present during anesthesia care and that affect the accuracy and reliability of pulse oximetry include dyshemoglobins, dyes (methylene blue, indocyanine green, and indigo carmine), nail polish, ambient light, light- emitting diode variability, motion artifact, and background noise. Electrocautery can interfere with pulse oximetry if the radiofrequency emissions are sensed by the photodetector. Surgical stereotactic positioning systems that make use of infrared position sensors may interfere with the infrared signals used by the pulse oximeter. Some of these instruments 1767 use complex signal processing of the two wavelengths of light to improve the signal-to-noise ratio and reject artifact. Studies in volunteers suggest that the performance of pulse oximeters incorporating this technology is superior to conventional oximetry during motion of the hand, hypoperfusion, and hypothermia. They have quick response times and their battery backup provides monitoring during transport. The clinical accuracy is typically reported to be within ±2% to 3% at 70% to 100% saturation and ±3% at 50% to 70% saturation. Published data from numerous investigations support accuracy and precision reported by instrument manufacturers. However, there are no definitive data demonstrating a reduction in morbidity or mortality associated with the advent of pulse oximetry. An older large randomized trial did not detect a significant difference in postoperative complications when routine pulse oximetry was used. However, a reduction14 of anesthesia mortality, as well as fewer malpractice claims from respiratory events, coincident with the introduction of pulse oximeters suggests that the routine use of these devices may have been a contributing factor. Contraindications There are no clinical contraindications to monitoring arterial oxygen saturation with pulse oximetry. Common Problems and Limitations Arterial oxygen monitors do not ensure adequacy of oxygen delivery to, or utilization by, peripheral tissues and should not be considered a replacement for arterial blood gas measurements or mixed central venous oxygen saturation when more definitive information regarding oxygen supply and utilization is required. Placing and obtaining reliable data from blood pressure cuffs and electrocardiogram leads may be challenging in an awake and vigorous child prior to inhalation induction. Therefore, at a minimum, efforts should be made to place a pulse oximetry device on the child or infant prior to induction of anesthesia. Pulse oximetry has also been shown to be a more sensitive monitor than capnography for unrecognized main-stem/endobronchial intubation in pediatric anesthesia. Respiratory events leading to inadequate15 ventilation and oxygenation represent the majority of perianesthetic morbidity in the pediatric anesthesia population. In conjunction with vigilant clinical assessment of the child’s airway and oxygenation, the pulse oximeter usually provides the most important indicator of patient well-being during pediatric anesthesia. Stress caused by hypoxemia and respiratory acidosis in16 infants and young children triggers a vagal response and subsequent systemic hypoperfusion. A decline in the pitch or rapidity of pulse oximetry tones may be the first signs of impending cardiovascular collapse. Anesthesiologists have long sought to measure the composition of expired gases noninvasively and in real time; these measurements can provide vital information regarding the patient’s respiratory condition and assist in the titration of volatile anesthetic agents. Early anesthetic gas detectors were based simply on the change in elastance of rubber strips exposed to the circulating gas. By2 transmitting light through a pure sample of a known gas over the range of infrared frequencies, a unique infrared transmission spectrum (like a fingerprint) can be created for the gas. At this wavelength, there is minimal interference from other gases that may also be present, such as water vapor, O , N O, and inhaled anesthetic agents. Figure 26-2 Gaseous-phase infrared transmission spectrum for carbon dioxide and nitrous oxide. The gas mixture is passed through the optical path of multiple infrared beams whose wavelengths are chosen to correspond to key features in the transmission spectra of the gases of interest. By analyzing the combination of absorption of infrared light at these wavelengths, the presence and concentrations of all of these gases can be determined simultaneously. An optical filter 1770 wheel was then used to cut out all but the desired wavelengths. Contemporary devices make use of small lasers and filters, designed such that they emit only at the desired wavelengths. This approach consumes much less electrical power, is physically less heavy, and has led to the development of conveniently portable handheld gas analyzers.
Although this goal is conventionally accomplished with mannitol discount 20 mg levitra with visa erectile dysfunction medicine with no side effects, some clinicians prefer hypertonic 1027 saline solutions order discount levitra erectile dysfunction vacuum pump demonstration. However, infusion of hypertonic saline increases intravascular volume, while diuresis secondary to mannitol decreases intravascular volume. Table 16-12 Hypertonic Resuscitation Fluids: Advantages and Disadvantages Fluid Status: Assessment and Monitoring For most surgical patients, conventional clinical assessment of the adequacy of intravascular volume is appropriate. Assessment of hypovolemia is mainly based in physical signs that include oliguria, supine hypotension, and a positive tilt test. In general, oliguria implies hypovolemia, keeping in mind that hypovolemic patients can have adequate urinary output and that urinary output can be misleadingly high. Supine hypotension suggests a blood volume deficit greater than 30%, although in elderly or chronic hypertensive patients, an arterial blood pressure within the normal range could represent relative hypotension. A positive tilt test, defined as an increase in heart rate of at least 20 beats per minute and a decrease in systolic blood pressure of 20 mmHg or more when the subject assumes the upright position, can be falsely negative. In contrast, orthostasis may occur in 20% to 30% of elderly patients despite normal blood volume. In volunteers, withdrawal of 500 mL of blood was84 associated with a greater increase in heart rate on standing than before blood withdrawal, but with no significant difference in the response of blood pressure or cardiac index. In acute hemorrhage, hematocrit decreases slowly as fluid shifts from the interstitial to the intravascular space and more rapidly during administration of fluids. The sensitivities and specificities of measurements of blood and urinary variables to hypovolemia are poor. In prerenal oliguria, enhanced sodium reabsorption should reduce urinary [Na ] to 20 mEq/L or+ less and enhanced water reabsorption should increase urinary concentration (i. Intraoperative Clinical Assessment Both surgeons and anesthesiologists tend to underestimate blood loss, based on assessment of blood on surgical gauze pads, pooled on the floor, and accumulated in the surgical field and suction containers. Assessment of the adequacy of intraoperative fluid resuscitation integrates multiple clinical variables, including heart rate, blood pressure, urinary output, arterial oxygenation, and pH. In patients receiving potent inhalational agents, maintenance of blood pressure within the normal range implies adequate intravascular volume. When measured, a central venous pressure of 6 to 12 mmHg suggests adequate blood volume. Tachycardia is an insensitive and 1029 nonspecific indicator of hypovolemia that is also altered by anesthetic drugs. In severe hypovolemia, the accuracy of indirect measurements of blood pressure diminishes. Under those circumstances, direct arterial pressure measurements are more accurate than indirect techniques. Therefore, in the absence of glycosuria or diuretic administration, a urinary output of 0. Mixed venous hemoglobin desaturation, a specific indicator of poor systemic perfusion, reflects average perfusion in multiple organs and cannot supplant regional monitors such as urinary output. Assessing physiologic responses to fluid87 administration can indicate the adequacy of cardiac preload and facilitate management of hemodynamics. Assessment increasingly depends on dynamic physiologic variables rather than static variables such as central venous pressure. Esophageal Doppler assessment of blood flow in the descending aorta is another promising technique in measuring adequacy of cardiac preload during high-risk surgical procedures. Using the esophageal Doppler to guide administration of colloid boluses, Venn et al. Of note, Horowitz and Kumar speculated that the infusion of95 colloid rather than the monitor-driven algorithm was responsible for the improved results. Large multicenter trials are needed in order to ascertain the benefits of the described novel techniques in perioperative outcomes of patients undergoing high-risk surgery. However, there is96 no apparent benefit for patients other than surgical patients and patients undergoing initial resuscitation from septic shock in the emergency department. Postoperative cardiovascular complications occurred significantly more frequently in the group receiving fluids alone (13/25, 52%, vs. Another specific risk associated with use of fluids to achieve goal-oriented resuscitation is an increased incidence of abdominal compartment syndrome in trauma patients. Disorders of sodium concentration, that is, hyponatremia and hypernatremia, usually result from relative excesses or deficits, respectively, of water. Regulation of total body sodium and [Na ] is accomplished primarily by the+ endocrine and renal systems (Table 16-13). Therefore,+ primary hyperaldosteronism is associated with hypervolemia and with hypertension, but not with abnormal [Na ]. The most common clinical scenarios associated with hyponatremia include the postoperative state, acute intracranial disease, malignant disease, medications, and acute pulmonary disease. Recently, hyponatremia, as well as hypokalemia and hypophosphatemia, have been recognized as complications of immunologic treatment of cancers such as hepatocellular carcinoma and melanoma. Symptoms that can accompany+ severe hyponatremia ([Na ] < 120 mEq/L) include loss of appetite, nausea,+ vomiting, cramps, weakness, altered level of consciousness, coma, and seizures. Because the blood–brain barrier is poorly permeable to sodium but freely permeable to water, a rapid decrease in plasma [Na ]+ promptly increases both extracellular and intracellular brain water. Because the brain does not rapidly compensate for changes in osmolality,106 acute hyponatremia produces more severe symptoms than chronic hyponatremia. The symptoms of chronic hyponatremia probably relate to depletion of brain electrolytes. Once brain volume has compensated for hyponatremia, rapid increases in [Na ] may lead to abrupt brain dehydration. Hyponatremia with a normal or high serum osmolality results from the presence of a nonsodium solute, such as glucose or mannitol, which holds water within the extracellular space and results in dilutional hyponatremia. The presence of a nonsodium solute may be inferred if measured osmolality exceeds calculated osmolality by over 10 mOsm/kg. Hyposmolality is more important in generating symptoms than is hyponatremia per se. In contrast, as glycine or sorbitol is metabolized, hyposmolality will gradually develop, and cerebral edema may appear as a late complication. Hyponatremia with a normal or elevated serum osmolality also may accompany renal insufficiency. Calculation of effective osmolality (2[Na ] + glucose/18) excludes the+ contribution of urea to osmolality and demonstrates true hypotonicity. Aquaporin 2, the vasopressin-regulated water channel, is upregulated in experimental congestive heart failure109 and cirrhosis110 and decreased by chronic vasopressin stimulation. In patients with renal insufficiency, reduced urinary diluting capacity can lead to hyponatremia if excess free water is given. Thiazide diuretics, unlike loop diuretics, promote hypovolemic hyponatremia by interfering with urinary dilution in the distal tubule. In patients after subarachnoid hemorrhage, administration of hydrocortisone 1,200 mg/day prevented the cerebral salt-wasting syndrome.