Perioperative GIK therapy has been advocated to ensure adequate energy substrate levels during cardiac surgery. However, hyperglycemia should be avoided because it may worsen neurologic outcome after cerebral ischemia. A prospective, randomized, clinical comparison was performed between two prebypass infusion regimens in 32 elective nondiabetic CABG patients. Sixteen patients (GIK group) received glucose, 0.6 g/kg/h, insulin, 0.12 U/kg/h, and KCl, 0.12 mmol/kg/h, from the induction of anesthesia to the start of CPB; while the remaining 16 patients (R group) received only Ringer's acetate. The pump prime was glucose free and a blood cardioplegia technique was used in both groups. No differences were found between the groups with regard to myocardial injury; the CK-MB enzyme fractions were elevated to a similar degree and the frequency of postoperative ECG changes were similar in both groups. Likewise, there were no differences in hemodynamic changes, need for inotropic support, arrhythmia frequency, or duration of ICU stay. The GIK patients had higher blood glucose (P < 0.05) and insulin levels (P < 0.01); blood glucose increased to 12.4 +/- 5.4 mmol/L (mean +/- SD) at cannulation, with a drop after starting bypass. Interindividual variation in GIK patients was great, with glucose values ranging between 20.1 mmol/L at cannulation to 2.0 mmol/L after starting CPB. A hyperglycemic response was seen in both groups during rewarming: 15.0 +/- 4.2 and 15.0 +/- 3.1 mmol/L in GIK and R patients, respectively. It is concluded that prebypass GIK infusion had no clinical benefits for elective CABG patients as compared to Ringer's acetate.(ABSTRACT TRUNCATED AT 250 WORDS)