Effects of different cardiopulmonary bypass procedures on intracellular energy metabolism, acid-base equilibrium and muscle water compartments in patients undergoing aortocoronary bypass grafting.

This study compares the effects of cardiopulmonary bypass with different flows and pressures on intracellular energy metabolism, acid-base equilibrium and muscle water compartments in two groups of patients undergoing aortocoronary bypass grafting. Eighteen patients (16 males, 2 females, mean age 54 yrs, +or- 7DS, NYHA class 1-2) undergoing Low-Flow (LF) (Flow rate 1.5 L/m/m2 at 26°). Low Pressure, CPB as well as ten age- and sex-matched patients undergoing normal-flow (Flow rate 2.2 L/m/m2 at 26°) Normal-pressure CPB were studied. Intracellular acid-base equilibrium, cell energetics and muscle water compartments were evaluated in quadriceps muscle specimens obtained by needle biopsy before and at the end of CPB. In both LF-LP and NF-NP groups, ATP levels were unchanged at the end of CPB, whereas PCr was decreased; muscle total water and extracellular water increased without variations of intracellular water; muscle and plasma lactate increased as HCO3 decreased; pH values remained unchanged. The present study suggests that a) CPB is associated with the overall preservation of intracellular compartment metabolism in skeletal muscle (about 40% of body cell mass) of patients undergoing aortocoronary bypass grafting, even though low PCr values and increased plasma and muscle lactate values found at the end of CPB could be an expression of cell functional reserve exhaustion; b) CPB effects on cell metabolism are comparable, regardless of the flows and pressures utilized