Identification of a period of renal ischemic vulnerability studying the changes in the indicators of acute renal insufficiency after heart surgery with extracorporeal circulation.

Abstract

We studied the pre operative status and the 1st, 4th, 12th and 24th hours of the post operative period after open heart surgery with cardiopulmonary bypass with a crystalloid solution containing 10 gr of mannitol. We considered acute renal failure (ARF) as being any increase in plasma creatinine values of 0.25 mg/dl for the first 24 hours and 0.5 mg/dl for periods longer than 24 hours. Six patients had transitory ARF (28.5%). The maximum value of plasma creatinine was 2.3 mg/dl and no patients required renal function substitution. There were no deaths. We used as ischemia ARF indicators the urinary flow rate, urine/plasma creatinine ratio, urine/plasma osmolality ratio, sodium fractional excretion and free water reabsorption. We also measured the urinary N-A-Glucosaminidase (NAG). We found that creatinine clearance reached its lowest in the first and fourth hours. Beyond the fourth hour we observed, the urinary flow rate reduce significantly, the urine/plasma creatinine and osmolality ratios reach values traditionally associated prerenal ARF, an increase main free water reabsorption and a decrease in sodium fractional excretion with a close relationship between the less than 1 value and the increase in plasma creatinine. There was a significant NAG increase in the 24 th hour. The evidence of a vulnerability period for renal ischemic lesions between the 4 th and 12 th hour suggests a second mannitol administration during the first four hours of the post operative period.