Year : 2006 | Volume
: 22 | Issue : 3 | Page : 194--200
Anesthetic implications of urology surgery
Department of Anesthesia, Christian Medical College, Vellore - 632 004, India
V T Cherian
Department of Anesthesia, Christian Medical College, Vellore - 632 004
Anesthesia for urology surgery poses special problems by way of patient factors and complexity of the procedure. Preoperative optimization of the patients with renal dysfunction and comorbidity; specific complications associated with the operative procedures, such as transurethral resection of prostate, laparoscopy surgery, percutaneous lithotripsy and renal transplantation; and the implications of the various positions that the patient may be subjected to during surgery are briefly presented. The purpose of this review article is to highlight the anesthetic implications of the renal and comorbid problems in a patient scheduled for genitourinary surgery.
|How to cite this article:|
Cherian V T. Anesthetic implications of urology surgery.Indian J Urol 2006;22:194-200
|How to cite this URL:|
Cherian V T. Anesthetic implications of urology surgery. Indian J Urol [serial online] 2006 [cited 2021 Oct 21 ];22:194-200
Available from: https://www.indianjurol.com/text.asp?2006/22/3/194/27623
Surgery of the renal and genitourinary systems includes a wide spectrum of procedures, ranging from the 'minor' outpatient or daycare-based endoscopic procedures to 'major' ones that cause marked physiological disturbances. These patients may have some element of renal dysfunction and associated comorbid medical conditions.
Preoperative optimization of patients with renal (chronic renal failure, dialysis) and comorbid (coronary artery disease) diseases, anticipation of special problems related to the procedure (renal transplantation, transurethral resection of prostate and percutaneous nephrolithotomy) and the implications of the different body positions (prone, flexed-lateral) the patient may be subjected to are some of the challenges a uro-anesthesiologist faces.
Preoperative optimization involves, first, identifying that a patient's physical status can be improved; and, second, implementing appropriate treatment regimen, amending current medication or both. The extent to which this may be possible will depend upon the perceived urgency of the surgery. Patients undergoing renal and genitourinary surgery are frequently at the extremes of age. In children, upper respiratory infections are common and those being operated for congenital urological anomalies may have anomalies in other organ systems. In the elderly, concomitant cardiovascular and respiratory diseases are common, which should be assessed and appropriately optimized.
Hypertension, left ventricular hypertrophy and accelerated atherosclerosis are common complications of chronic renal failure. The most significant risk factors associated with adverse outcome have been identified as congestive heart failure, recent myocardial infarction, unstable angina, significant arrhythmias and severe valvular disease., In patients with coronary artery disease, the dynamic status of the coronary circulation can be estimated by assessing the patient's exercise tolerance. The invasive investigation of coronary angiography is only indicated if the patient is a candidate for myocardial revascularization, namely those who develop ischemia at low levels of exercise or have severe unstable angina. Balancing the myocardial oxygen supply (adequate diastolic blood pressure, hemoglobin and oxygenation) and demand (low heart rate and optimized preload) is the key to perioperative management of patients with coronary artery disease. Although it has been shown that mild to moderate hypertension need not subject patients to added risk provided they are closely monitored, exaggerated blood pressure fluctuations with associated ECG evidence of myocardial ischemia have been demonstrated in patients with severe hypertension. Therefore, it is prudent to control blood pressure preoperatively and it can be achieved quite rapidly by oral administration of nifedipine or a b-blocker. All antihypertensive medications should be continued till the day of surgery except diuretics and angiotensin-converting enzyme inhibitors which can cause persistent hypotension under anesthesia. A patient having a pacemaker should be assessed for the proper functioning of the pacemaker and its battery; electrolyte levels, since potassium is essential for proper myocardial capture of the pacemaker impulse; and the method to convert it to asynchronous mode.
A cardiologist's opinion, prior to surgery, is useful with regard to the assessment of the cardiovascular condition and its optimization.
Preoperative assessment of a diabetic includes immediate and long-term glycemic control and presence of end-organ involvement such as coronary artery disease, nephropathy and autonomic neuropathy. There is a trend towards tight control of glucose perioperatively, keeping the blood glucose Patients on anticoagulants
These include warfarin (prosthetic heart valves, atrial fibrillation), heparin (thromboprophylaxis) and antiplatelet medications. Warfarin is discontinued 4 days prior to surgery and the perioperative period is covered with heparin. Central neuraxial block should be avoided if the international normalized ratio (INR) is greater than 1.5. Risk of venous thromboembolism is higher in patients who are obese, those scheduled for pelvic and radical surgery for malignancy and those expected to be immobilized for a long time. Thromboprophylaxis is usually achieved with low molecular weight heparin (LMWH), which is instituted the evening before the surgery and continued on a 'once or twice a day' regimen. Central neuraxial block should be performed only 12 h after the dose of LMWH and the subsequent dose should be deferred for at least 2 h. If an epidural catheter is sited, its removal should be timed 12 h after the previous dose and the subsequent dose deferred for 2 h. Central neuraxial block in patients on only low-dose aspirin or other nonsteroidal anti-inflammatory drugs can be performed without stopping the medication; however, the recommended interval between discontinuation and neuraxial block is 14 days for ticlopidine and 7 days for clopidogrel.
Acceptable levels of hemoglobin
Although the National Institute of Health consensus in 1988 suggested a hemoglobin level of 10 g.dL -1sub , currently most clinicians would accept a level of 8 g.dL -1sub , as suggested by the ASA task force in 1996.
The choices of anesthetic techniques for urological surgery are local, regional, general or a combination of them. A common misconception is that regional anesthesia is safer and requires less preoperative assessment when compared to general anesthesia, which is not true. A large number of urological surgeries can be performed under regional anesthesia; the level of blockade depends on the organ being operated and the knowledge of its innervation.
General anesthesia is preferred for certain patient-related and surgical factors, e.g., intra-abdominal procedures, anticipated major blood loss and patients with cardiovascular instability. It involves the maintenance of adequate anesthesia and analgesia, monitoring the cardiorespiratory and biochemical parameters, managing any derangement that might occur during surgery and continuing the care into the postoperative period, including postsurgical pain.
Chronic renal failure (CRF)
CRF may be caused by primary renal disease or by systemic diseases which also affect the kidney. It becomes biochemically evident when less than 40% of the nephrons are functioning. Dialysis is usually not required unless less than 10% of nephrons are functioning. The following factors should be addressed when assessing a patient with CRF.
In CRF, sodium and water excretion is relatively fixed and reduced. The degree of hydration should be assessed in the usual manner using skin turgor, mucous membranes, jugular venous pressure, pedal and pulmonary edema. Central venous pressure may occasionally be required. Most patients on dialysis would know their normal hydrated weight and their daily fluid allowance. The patient should be normovolemic prior to surgery.
The most significant biochemical derangements in patients with uncorrected renal disease are hyperkalemia (serum K+ >5 mmol. L -1) and acidosis. ECG changes such as tall peaked T waves, shortened QT interval, widened QRS complexes and loss of P waves become apparent at 6-7 mmol. L -1. Methods to treat hyperkalemia include 0.5 ml.kg -1 of 10% calcium gluconate (maximum 20 ml), 50 ml of 50% glucose as an intravenous bolus (insulin would be required in diabetics), 1-2 mmol.kg -1 sodium bicarbonate intravenously over 5-10 min (provides a large sodium and fluid load) and nebulized salbutamol (2.5-5 mg, which assists in moving K+ into the cells). Total body potassium can be reduced by dialysis or calcium resonium (0.5 g. kg -1 8 hourly either rectally or orally) and by restricting potassium in the diet. Acidosis is best improved by dialysis. Administration of bicarbonate should only be considered when the pH is less than 7.2.
Hypertension, ischemic heart disease, pulmonary edema and pericarditis are the usual manifestations of chronic renal failure.
Pulmonary edema and pleural effusion would reduce lung compliance, functional residual capacity and increase ventilation-perfusion mismatch.
Chronic anemia is common but usually well tolerated in patients with chronic renal failure. Hemoglobin levels of 7-8 g.dL -1 are acceptable. Uremic patients may have bleeding tendency due to a decrease in platelet adhesion and fragility of the vessel walls. Administration of deamino-D-arginine vasopressin (DDAVP) in the dose of 0.3 mg.kg -1sub intravenously has been shown to normalize the bleeding time and improve platelet function. Vasopressin stimulates the release of von-Willibrand-factor VIII complex from the endothelium into the plasma, where it binds and activates the platelets.
Anorexia, nausea, vomiting, delayed gastric emptying and esophageal reflux are the common symptoms. Therefore, peri-anesthetic care should include steps to reduce the possibility of tracheal soiling, such as administration of proton or H 2 receptor inhibitor and rapid-sequence intubation.
Pharmacology of anesthetic drugs
The excretion of water-soluble drugs and their metabolites will be impaired. A reduced dose of thiopentone is indicated because of low protein binding and relative hypovolemia that follows dialysis. Propofol can be used safely, but the usual dose of 2 mg.kg -1 may cause marked vasodilatation. Atracurium is the muscle relaxant of choice as it undergoes spontaneous Hoffman degradation at body temperature. Vecuronium and mivacurium are safe to use in renal failure as only small percentage is excreted renally. Suxamethonium causes hyperkalemia, but if a rapid-sequence intubation is indicated, it is still the drug of choice. Morphine is metabolized to morphine-6-glucuronide and pethidine to norpethidine, both of which accumulate in renal failure after repeated doses, but usual intraoperative doses are well tolerated. Fentanyl and alfentanil can be used in normal doses. Isoflurane is considered the anesthetic of choice in patients with renal failure. Nonsteroidal anti-inflammatory analgesics and other nephrotoxic drugs such as aminoglycoside antibiotics are best avoided in patients with renal failure.
Dialysis is essential to control pulmonary edema, hyperkalemia, acidosis and platelet function. However, it can lead to intravascular hypovolemia and electrolyte deficits (hypokalemia, hypomagnesemia, hypophos-phatemia). The ideal timing of preoperative dialysis is the day before surgery.
Renal transplant surgery
The preoperative optimization of patients with end-stage renal disease (ESRD) scheduled for renal transplantation include dialysis, control of hypertension, treatment of hyperkalemia and coagulopathy. Premedication with a short-acting benzodiazepine, such as midazolam, in an anxious patient; and prophylaxis for acid-aspiration syndrome, using H 2 -blocker or proton pump inhibitor, are advisable. Since these patients are at increased risk of hepatitis and HIV infection, universal precaution should be taken by all. Strict asepsis is essential for all invasive procedures. The ECG, pulse oximeter, capnograph, temperature and central venous pressure monitoring are usually done in all patients. The radial artery pressure monitoring is usually avoided so as to preserve access to future shunt sites. However, it may be indicated for hemodynamic monitoring in patients with uremic cardiomyopathy.
The points to consider during induction of anesthesia are usefulness of preoxygenation in anemic patients, intravascular volume status after dialysis, reducing the dose of thiopentone in hypoalbuminemic patients, precautions for acid aspiration and reducing the hypertensive response to laryngoscopy and tracheal intubation. Intraoperative management involves judicious fluid and electrolyte management, maintaining blood pressure and planning for postoperative care, including pain relief.
The transplanted kidney may not start functioning immediately; this may be due to acute graft rejection or acute tubular necrosis. There are three perioperative management periods that can affect the viability of the transplanted kidney. The first is the management of the kidney donor (living or dead); the second is the preservation of the graft kidney, which involves the period of ischemia; and the third is the perioperative management of the recipient.
The living donor should be in excellent physical health with no evidence of acute or chronic illness. The surgery is performed in the lateral flexed (kidney) position, which can cause hypotension due to impeded venous return and ventilation-perfusion mismatch. Adequate hydration is mandatory. Mannitol, during the handling of the kidney, could provide renal protection. The kidney should be harvested while it is well perfused and producing urine.
The period of ischemic starts with the clamping of the renal vessels in the donor and ends with the completion of vascular anastomosis in the recipient and reperfusion of the graft. Warm ischemia is particularly harmful and is usually a minute or two till the cold preservation fluid is perfused, immediately after removing the kidney from the donor. However, the kidney starts warming up, once placed in the recipient for vascular anastomosis. The cold ischemia time is usually only a few minutes if the donor and recipient surgery are performed simultaneously in adjacent operating rooms. However, in 'cadaveric' transplant it is longer but should ideally be less than 24 h.
Once the vascular anastomosis to the graft is complete, the early onset of urine output has been linked to graft survival. Several measures can be used to stimulate urine production and presumably improve kidney viability. These measures include intravascular volume expansion guided by central venous pressure, liberal use of albumin or blood, use of diuretics such as mannitol and loop diuretics and use of dopamine.
Transurethral resection of the prostate (TURP)
Benign prostatic hypertrophy affects 50% of males at 60 years and 90% of 85-year-olds and so TURP is a commonly performed surgery on elderly patients, a population group with a high incidence of cardiac, respiratory and renal disease. The mortality rate associated with TURP is 0.2-6%, with the commonest cause of death being myocardial infarction.
The prostate gland has a rich blood supply with large venous sinuses adjacent to its capsule. TURP is performed by inserting a resectoscope through the urethra; thereafter, using an electrically powered cutting and coagulating metal loop, the prostatic gland is resected while preserving the capsule. The surgical field is kept clear of the debris and blood by a continuous flow of an irrigating fluid. If the capsule is breached, the irrigation fluid can be absorbed into the peri-prostatic and retroperitoneal spaces and finally into the circulation. If the venous sinuses are inadvertently opened, bleeding could be profuse and there could be significant absorption of the irrigating fluid.
Ideally, the irrigating fluid should be isotonic, electrically inert, nontoxic, transparent, easy to sterilize and inexpensive, but such a solution does not exist. Distilled water, which was used previously, is electrically inert, optically clear and inexpensive, but hypotonic; and its absorption could lead to hemolysis, shock and renal failure. Isosmotic solutions such as normal saline and Ringer's lactate would be well tolerated but cannot be used as these solutions are highly ionized and would facilitate the dispersion of the high-frequency current from the resectoscope. A solution of 1.5% glycine (HO 2 -CCH 2 -NH 2 ), which is moderately hypotonic (220 mOsm.kg -1) so as to keep it transparent, is the commonly used irrigating fluid. Although it does not cause significant hemolysis, excessive absorption can lead to pulmonary edema, hypo-osmolality and hyponatremia. Acute hypo-osmolality allows movement of water into the cells, causing cerebral edema resulting in restlessness, agitation, confusion and coma. Hyponatremia can cause convulsions, arrhythmias, hypotension and pulmonary edema. Glycine can cause retinal toxic effects leading to temporary blindness. Glycine is a major inhibiting transmitter acting in the spinal cord and brainstem. Normal plasma glycine levels are 13-17 mg. L -1. The absorption of the irrigating fluid depends on the duration of resection and the height of the container of irrigating fluid above the operating table as it determines the hydrostatic pressure. On an average, 10-30 ml of fluid is absorbed per minute of resection time, which is usually restricted to about 1 h. TURP syndrome is the term applied to the signs and symptoms caused primarily by excessive absorption of irrigating fluid. Treatment consists of fluid restriction and loop diuretic such as frusemide.
Other problems of TURP are perforation of the bladder by the resectoscope or the cutting loop, bacteremia and septicemia, hypothermia and hemorrhage. Since the blood is washed away into a draining bucket, it is extremely difficult to estimate the blood loss. It is proposed to be about 2-5 ml per minute of resection time or 20-50 ml per gram of prostate. Serial estimation of hematocrit gives a better estimate of blood loss.
Subarachnoid block is the most frequent anesthetic technique used for TURP; the advantages are it provides adequate anesthesia for the patient and good relaxation of the pelvic floor and the perineum for the surgeon. The signs and symptoms of fluid overload can be recognized easily in a patient who is awake. The ideal sensory level of blockade for TURP is the 10th thoracic spinal level as this is required to eliminate the discomfort caused by bladder distension while the patient would experience abdominal or shoulder pain if the bladder is accidentally perforated.
The other advantages of regional anesthesia are decreased incidence of deep vein thrombosis, reduced operative blood loss (reduced arterial and venous blood pressure) and better homeostasis of the neuroendocrine system and improved immune response. The sympathetic blockade produced increases the venous capacitance and tends to mitigate intraoperative fluid overload; but be cautioned that this reverses when the blockade wears off, which usually happens in the not-so-well supervised ward.
Percutaneous nephrolithotomy (PCNL)
Percutaneous nephrolithotomy is a minimally invasive technique, wherein an endoscope is introduced into the lower calyx of the kidney under fluoroscopy, aided by radio-opaque dye in the pelvi-calyceal system; and using laser or ultrasound probes, the calculi are fractured under vision and the fragments are irrigated through a channel in the scope, using saline.
This procedure is performed under general anesthesia. The patient is placed in the prone position and a padded roll is placed under the lower chest so as to push the kidney upwards to assist its localization. This may interfere with the excursion of the diaphragm, especially in the obese patient. The complications that could occur following a PCNL are pain, fever, urinary infection, ureteric colic, septicemia, bleeding, pelvic or ureteric tears, pneumothorax, hydrothorax, extravasation of irrigation fluid into the retroperitoneal space, problems associated with prone position and hypothermia. Presence of rigors, hypothermia or hyperthermia and unexplained hypotension with tachycardia could suggest septicemia. Similarly difficulty in breathing, restlessness and hypoxemia should prompt the possibility of pneumothorax or hydrothorax, necessitating a radiological examination of the chest.
Extracorporeal shock wave lithotripsy
This noninvasive technique uses an acoustic shock wave to shatter renal and upper ureteric calculi. Although this is performed usually as an outpatient procedure under mild sedation, anesthesia may be needed in patients who are not cooperative or cannot lie still due to involuntary muscle spasm or somatic pain.
The side effects of this procedure include pain, blistering of the skin where the shock wave enters, renal edema and hemorrhage into the renal pelvis. The pain, which is due to shock wave induced and cavitation-mediated irritation of the tissues, can be controlled by regional or general anesthesia. Care should be taken during epidural or subarachnoid block to avoid injection of air bubble as it can create an acoustic interface. This can also happen if the patient has been given gas bubble contrast.
Since the effectiveness of this therapy depends on the immobility of the calculus, efforts to reduce shivering and even diaphragmatic excursions helps to minimize its displacement from the line of the shock wave. Sedation helps to reduce diaphragmatic movements. In patients under general anesthesia, high frequency jet ventilation has been advocated as one of the methods.
Pacemaker and automatic implantable cardioverter defibrillator can malfunction or be damaged by the force of the shock wave. The calcified wall of an abdominal aortic aneurysm can provide an acoustic interface and fragmentation of the calcific plaque can lead to aortic rupture, sometimes even weeks after the procedure.
Although urology was one of the last surgical specialties to adopt laparoscopic surgery, it is now well established for nephrectomy, pyeloplasty and pelvic surgery.
The complications associated with laparoscopic surgery are due to the mechanical consequences of and the neuro-humoral responses to pneumoperitoneum, absorption of carbon dioxide and the physiological changes associated with patient positioning. Regulating the insufflation pressure minimizes these effects, but handling of the kidney decreases renal blood flow, glomerular filtration, creatinine clearance and urine production while it increases plasma renin and antidiuretic hormone release. During donor nephrectomy, mannitol (0.5-1 g.kg -1sub ) with frusemide is usually required to maintain a urine flow of 300-500 ml.h -1sub until the kidney is removed.
Positioning of the patient is crucial during laparoscopic surgery. While prostatectomy and cystectomy required the patient to be supine with steep Trendelenburg (>30%) tilt, surgery on the kidney and renal pelvis are conducted in lateral jackknife position.
Patient positioning during urological surgery
Positioning a patient for a surgical procedure is frequently a compromise between what the anesthetized patient can tolerate, both structurally and physiologically and what the surgeon requires for performing the surgery. The various positions that the patient may be placed for urological surgery are supine, prone, lateral, flexed lateral, lithotomy and all these with or without Trendelenburg tilt. The patient's ability to tolerate these positions should be assessed during the preoperative visit - e.g., a patient with ankylosing spondylitis for nephrectomy may not be able to tolerate a flexed lateral position; care should be taken while placing a patient, who has had knee replacement, in lithotomy position; and a patient with cardiorespiratory dysfunction may not tolerate a steep Trendelenburg tilt during laparoscopic, radical prostatectomy.
The patient lies supine with arms crossed on the trunk or extended laterally to less than 90° on arm-boards. The lower limb is flexed at the hip and knee and both limbs are simultaneously elevated and separated so that the perineum becomes accessible to the surgeon. Numerous devices are available to support the lower limb, the height of which should be adjusted according to the stature of the patient. The lateral aspect of the knee should be padded to avoid injury to the common peroneal nerve. While lowering the legs, they should be brought together at the knees and ankles and lowered slowly together so as to minimize torsion stress on the lumbar spine. Lowering of the legs at the end of surgery increases the circulatory capacitance and may lead to hypotension. If the arms are kept by the side of the body, the hands should be protected from being crushed as the leg section of the table is returned to horizontal position.
Tilting the operating table head down gravitates the viscera cephalad and provides better exposure into the pelvic space. Although in the classic Trendelenburg position, 30-45° head-down tilt was used, currently most would employ a tilt of 10-15°. Cephalad displacement of the diaphragm, obstruction to its caudad excursion during inspiration and worsened ventilation-perfusion ratio due to the accumulation of blood in the poorly ventilated lung apices necessitates controlled ventilation in this position. Intracranial vascular congestion and increased intracranial pressure can be expected.
The patient is rolled onto one side and stabilized by flexing the down-side thigh and knee. A pad is placed under the knee of the down-side leg to protect the peroneal nerve, a pillow is placed between the two lower limbs to ease the pressure of the upper leg on the under one and the head should be supported to keep the cervical spine horizontal. A small pad is placed under the down-side axilla ('axillary roll') to ensure adequate perfusion of the arm and to minimize circumduction of the dependent shoulder, which would stretch the suprascapular nerve. Soft padding should be used to protect the down-side ears and eyes. The patient is stabilized in the lateral position by retaining tapes over the hip and the chest. Care must be taken to place the hip tapes between the iliac crest and the head of the femur as compressive pressure over the femur can lead to aseptic necrosis of the femoral head and the tape across the chest should be placed just caudad to the axilla where it has little effect on thoracic expansion.
Lateral jackknife (kidney)
The down-side iliac crest is placed over the hinge between the back and thigh sections of the table, which is angulated to flex the thighs laterally so as to stretch the up-side flank and increase the space between the iliac crest and the costal margin. This is extenuated by the use of an elevated 'kidney' rest under the down-side iliac crest, which improves the access to the upper kidney under the overhanging costal margin. However, it imposes such severe skeletal stress and ventilatory restrictions that most unanesthetized persons cannot tolerate this position. There is considerable venous pooling in the lower limbs, which can cause hypotension and is a risk for deep vein thrombosis. This may be minimized by providing a Trendelenburg tilt to the whole table. All the precautions as for the lateral position should be taken.
In the usual prone position, rolls are placed under the chest and pelvis to elevate the trunk off the table so that ventilatory excursions are not hampered. However, during PCNL a roll is placed under the lower chest so as to push the kidney upwards to assist its localization. This may interfere with the excursion of the diaphragm, especially in the obese patient. Care must be taken in positioning the head and neck. The forehead should be placed on a padded headrest, so as to avoid pressure on the eyeball as compression on the eye can lead to central retinal artery thrombosis resulting in blindness. Brachial plexus injury on the side contralateral to the turned face is possible if the arm by the side of the torso is pulled downwards. If the arm is placed on an arm-board alongside the head, the head of the humerus can stretch and compress the axillary neurovascular bundle. Effective padding should be given to the elbow to protect the ulnar nerve of the pronated forearm. Some patients complain of paresthesia in their arms after keeping them raised above the head. This is suggestive of thoracic outlet syndrome caused by the compression of the brachial plexus and subclavian vessels near the first rib.
Therefore, anesthesia for urological surgery poses problems because of the type of patient population and the type of procedure. Certain positions that the patient might be subjected to can stress the normal physiology and may even cause serious damage unless special care is taken. Although the responsibility of the anesthetized patient lies with the anesthesiologist, it is important that all concerned with the perioperative care of these patients are aware of the potential problems.
|1||Cousins J, Howard J, Borra P. Principles of anaesthesia in urological surgery. Br J Urol Int 2005;96:223-9.|
|2||Cherian VT, Tomlinson AA. Preoperative optimization. In : Cashman JN (editor) Preoperative assessment. BMJ Books: London; 2001. p. 93-132.|
|3||Goldman L, Caldera DL, Nussbaum SR, Southwick FS, Krogstad D, Murray B, et al . Multifactorial index of cardiac risk in noncardiac surgical procedures. N Engl J Med 1977;297:845-50.|
|4||Eagle KA, Brundage BH, Chaitman BR, Ewy GA, Fleisher LA, Hertzer NR, et al . Guidelines for perioperative cardiovascular evaluation for noncardiac surgery. Report of the American College of Cardiology/ American Heart Association task force on practice guidelines. Circulation 1996;93:1278-317.|
|5||Wallace A, Layug B, Tateo I, Li J, Hollenberg M, Browner W, et al . Prophylactic atenolol reduces postoperative myocardial ischaemia. McSPI Research Group. Anesthesiology 1998;88:7-17.|
|6||Prys-Roberts C, Meloche R, Fo'λx P. Studies of anaesthesia in relation to hypertension. I: Cardiovascular responses to treated and untreated patients. Br J Anaesth 1971;43:122-37.|
|7||Ouattara A, Lecomte P, Le Manach Y, Landi M, Jacqueminet S, Platonov I, et al . Poor intraoperative blood glucose control is associated with a worsened hospital outcome after cardiac surgery in diabetic patients. Anesthesiology 2005;103:687-94.|
|8||Miriam A, Korula G. A simple glucose insulin regimen for perioperative blood glucose control: The Vellore regimen. Anesth Analg 2004;99:598-602.|
|9||Horlocker TT, Wedel DJ, Benzon H, Brown DL, Enneking FK, Heit JA, et al. Regional anaesthesia in the anticoagulated patient: Defining the risks (The second ASRA consensus conference on neuraxial anesthesia and anticoagulation). Reg Anesth Pain Med 2003;28:172-97.|
|10||Practice guidelines for blood component therapy. American Society of Anesthesiologists task force on blood component therapy. Anesthesiology 1996;84:732-47.|
|11||Malhotra V, Sudheendra V, Diwan S. Anesthesia and the Renal and Genitourinary systems. In : Miller RD (editor) Miller's Anesthesia (6th ed). Elsevier Churchill Livingstone: Philadelphia; 2005. p. 2175-208.|
|12||Sprung J, Kapural L, Bourke DL, O'Hara JF Jr. Anesthesia for kidney transplant surgery. Anesth Clin North Am 2000;18:919-51.|
|13||Malhotra V. Transurethral resection of the prostate. Anesthesiol Clin North Am 2000;18:883-97.|
|14||Gravenstein D. Extracorporeal shock wave lithotripsy and percutaneous nephrolithotomy. Anesthesiol Clin North Am 2000;18:953-71.|
|15||Taylor JD, McLoughlin GA, Parsons KF. Extracorporeal shock wave lithotripsy induced rupture of abdominal aortic aneurysm. Br J Urol 1995;76:262-3.|
|16||Conacher ID, Soomro NA, Rix D. Anaesthesia for laparoscopic urological surgery. Br J Anaesth 2004;93:859-64.|
|17||Martin JT. Patient positioning. In : Barash PG, Cullen BF, Stoelting RK, (editors) Clinical Anesthesia. Lippincott-Raven: Philadelphia; 1996. p. 709-36.|