Summary

In study session VII you have learnt

• Acute renal failure is a sudden decrease in renal function resulting in inability of the kidneys to excrete wastes. Oligurea, a condition in which a patient does not produce enough urine, is the clinical manifestation of renal failure.
• Pre-renal renal failure results from an acute decrease in renal perfusion or renal blood flow. Renal azotemia is usually due to intrinsic renal disease, renal ischemia, or nephrotoxins. Prerenal azotemia and ischemic tubular necrosis present as a continuum with the initial decreases in renal blood flow leading to ischemia of the renal tubular cells. Post-renal azotemia is the result of urinary tract obstruction or disruption, as with prostatic hypertrophy or cancer of the prostate or cervix.
• The maintenance of normovolemia and an adequate renal perfusion pressure are the two most important factors in avoiding acute renal falure. The urine output should be measured hourly and should be maintained above 1 ml/kg/hr.
• Chronic renal failure is the progressive, irreversible deterioration of renal function that results from a wide variety of diseases.
• Preoperative assessment and treatment of medical problems in renal failure should be done before anesthesia.
• Patients with uremia and other co-morbid conditions (diabetes mellitus) are at an increased risk for aspiration of gastric contents during induction of anesthesia. The use of a rapid sequence induction of anesthesia technique may be indicated in such patients. Succinylcholine is not contraindicated unless the serum potassium increased to > 5 mEq/L.
• If spinal anesthesia is being performed fluid preloading should be kept to a minimum and vasoconstrictors used to maintain the blood pressure. Coagulation profile should be checked preoperatively.
• Intraoperative oliguria is common in healthy surgical patients; it is caused by inadequate renal perfusion. Marked reduction or cessation of urine output may occur abruptly or developed gradually over several hours and can be related to several pathophysiologic processes.
• Oliguria can be diagnosed intraoperatively only via use of an indwelling urinary catheter. Lengthy surgical procedures, procedures that require deliberate hypotension and if large volume loss is anticipated are all indications for placement of a bladder catheter.