RENAL PROTECTION IN PATIENTS UNDERGOING CARDIOPULMONARY BYPASS WITH PREOPERATIVE ABNORMAL RENAL-FUNCTION

We prospectively studied the effects of renal protection intervention in 17 patients with preoperative abnormal renal function (plasma creat inine >1.5 mg/dL) scheduled for elective coronary surgery. Patients we re randomized to either dopamine 2.0 ,mu g.kg(-1).min(-1) (Group 1, n = 10) or perfusion pressure >70 mm Hg during cardiopulmonary bypass (C PB) (Group 2, n = 7). Glomerular filtration rate and effective renal p lasma flow were measured with inulin and I-125-hippuran clearances bef ore the induction of anesthesia, after sternotomy and before CFB, duri ng hypo-and normothermic CPB, after sternal closure, and 1 h postopera tively. Plasma and urine electrolytes were measured, and free water, o smolar, and creatinine clearances, as well as fractional excretion of sodium and potassium, were calculated ed before and after surgery. Sig nificant differences between groups were found before CPB for glomerul ar filtration rate (higher in Group 1), urine output (2.0 vs 0.29 mL/m in in Group 1 versus Group 2), urinary creatinine (66 vs 175 mg/dL), u rinary osmolarity (370 vs 627 mOsm/L), osmolar clearance (2.1 vs 0.7 m L/min), and urinary potassium (33 vs 71 mEq/L). There were no differen ces between groups during hypo-and normothermic CPB. After CPB, the on ly difference was a slightly higher urinary creatinine in Group 2. Ren al plasma flow was lower than normal in all patients before the induct ion of anesthesia. A nonsignificant trend toward increased flow was se en during hypothermic CPB. Filtration fraction was high before CPB, wh ich suggests efferent arteriolar vasoconstriction, descending toward n ormal during and after CPB. The same pattern of changes was present in both groups. In conclusion, there were no clinically relevant differe nces between the two treatment modalities during and after CPB. Howeve r, significant differences were observed before CPB, when dopamine see med to partially revert renal vasoconstriction. Implications: Two prot ective interventions were compared in patients undergoing heart surger y to prevent deterioration of renal function; these were dopamine infu sion throughout the operation and phenylephrine infusion during cardio pulmonary bypass. We found clinically relevant differences only during surgery before cardiopulmonary bypass.