Calculation of the dose of sodium bicarbonate for correcting metabolic acidosis in surgery with circulation arrest and deep hypothermia

The study was aimed at detecting the factors which determine the amount of 7% sodium bicarbonate solution needed to correct metabolic acidosis in patients subjected to repair surgery on the aorta involving long arrest of circulation under conditions of deep hypothermia. The total dose of 7% sodium bicarbonate solution was calculated as the sum of volumes of this solution needed to neutralize certain concentrations of underoxidized metabolites and BE. Accumulation of acid metabolites in tissues is caused by ineffective compensation of energy expenditure during warming of a patient after circulation arrest and deep hypothermia. After reperfusion injury to tissues, the release of these metabolites into the blood and further neutralization are appreciably slower during such operations than during other cardiovascular bypass interventions. That is why the routine method for calculating the dose of 7% sodium bicarbonate solution for correcting metabolic acidosis is not adequate in cases with abnormal body temperature. Estimation of the dose with consideration for venous blood temperature and pO2 is more correct. An algorithm of calculation is proposed.