Blood oxygen transport function in cardiopulmonary bypass surgery for acquired heart valvular diseases

Intraoperative analysis of the principal parameters of oxygen transport was carried out in 123 cardiosurgical patients before and after radical correction of an acquired heart valvular disease of rheumatic origin. The study was carried out in two groups of patients operated on under ataralgesia (n = 74) and total intravenous anesthesia (n = 49). The principal parameters that reflect oxygen homeostasis at various stages of the operation are heart productivity, oxygen supply and consumption. Reduced cardiac output, that most frequently develops directly before cardiopulmonary bypass onset, results in impairment of oxygen supply. To maintain metabolism under such conditions, oxygen extraction from the blood is increased. Analysis of correlations helped determine the critical level of oxygen supply: 350 ml/min/m2; a lower level of oxygen supply involves reduction of oxygen consumption, formation of oxygen debt, and lactate accumulations. Limited oxygen supply is more incident in the patients operated on in conditions of ataralgesia including nitrous oxide. Administration of the drugs stimulating heart productivity in the early postperfusion period effectively correct disordered oxygen transport function of the blood in the patients with reduced oxygen supply, whatever the anesthetic method employed. Dopamine infusions in dose 5-7 micrograms/kg/min help compensate for oxygen debt, which fact is proved by a positive time course of blood lactate levels.