Oliguria. A sign of renal success or impending renal failure?

Limiting renal impairment begins with identifying patients at increased risk for renal dysfunction (monitoring of renal function is important in these patients) and understanding the physiology of urine formation, the influence of anesthetic drugs, and intraoperative events on the physiology and pathophysiology of renal function. The fundamental principles emphasized in this article include avoidance of hypovolemia or renal hypoperfusion (e.g., hypotension, decreased cardiac output) in patients at risk (because of pre-existing disease or the nature of the operative procedure) and limitation of toxins that might jeopardize residual renal function. Direct monitors of renal well-being are still in the rudimentary stage of development. Indirect measures of renal function (CVP, MAP) are used on a minute-to-minute basis. The clinical measurement of urine output still is relied on when evaluating renal function over longer time intervals. Currently, only one drug (N-acetylcysteine) improves renal outcome after a high-risk procedure (radiocontrast administration) prophylactically. Manipulation of autorenal regulatory vasodilators (e.g., nitric oxide, PGE2) and vasoconstrictors (e.g., endothelin, vasopressin, angiotensin II) may prove helpful in the future. Currently, maintenance of adequate intravascular volume, MAP, and cardiac output are the most important renal protective measures an anesthesiologist can provide to preserve renal function high-risk patients.