Effects of Low and High Glucose

The effects of infusion of normal saline (NS) and glucose-insulin-potassium (GIK) with either low or high G concentrations on hemodynamics and exercise tolerance were studied in patients with angina pectoris. Studies were performed at rest and during exercise, twice before and once after one of the infusions. Eleven patients (low-G GIK group) received 150 ml of GIK solution that contained 15 g G, 8 U I, and 12 mEq KCI; 10 patients received 150 ml NS; and seven patients (high-G GIK group) received 1.5 g/kg of G orally followed by a 100 ml infusion that contained 0.5 g/kg G, 1.5 U/kg I, and 10 mEq KCI. Before infusion, left ventricular end-diastolic pressure (LVEDP) was higher during the first exercise period (Ex,) than during the second exercise period (Ex2), but the exercise time to angina did not change significantly. After NS, exercise time to angina, hemodynamics and G levels were similar to the preinfusion Ex2 values. After low-G GIK infusion, G levels increased from 99 to 140 mg/dl (p < 0.01), but the exercise time to angina did not change significantly from the preinfusion Ex2 values. Only two of the 11 patients exercised for a longer period of time and had less ST-segment depression. However, LVEDP during exercise after low-G GIK infusion was lower compared with the preinfusion Ex2 values (18 vs 23 mm Hg, p < 0.02). After high-G GIK infusion, G levels increased from 109 to 331 mg/dl (p < 0.01), but exercise tolerance decreased from a mean preinfusion (EX2) value of 159 to 74 seconds (p < 0.01) after this infusion. These studies show that while low-G GIK had variable effects on exercise tolerance and reduced LVEDP during exercise-induced angina, high-G GIK had detrimental effects. Therefore, increasing substrate (G) availability had no beneficial effects on supine exercise tolerance in patients with angina pectoris.