[Graded hypercapnia in the postoperative evaluation of central hemodynamics in cardiosurgical patients]

117 patients were examined in the early period after operation on an open heart (aortocoronary shunt and correction of acquired valvular heart diseases). The hemodynamic values were studied by direct methods with catheterization of the right parts of the heart and pulmonary artery. The catheter was introduced into the left atrium during the operation by transseptal puncture. In the absence of the latter, pulmonary capillary wedge pressure was measured. The loading volume test (LVT) was conducted by i.v. infusion of 200-800 ml solution. Graded hypercapnia (GH) was accomplished by stepped administration of 3-5% CO2 into the inspiration line or reducing minute lung ventilation. The study revealed different sensitivity of patients to CO2 and different variants of hemodynamic changes in response to hypercapnia. The underlying factors were; (1) venoconstriction, increased return to the heart, and realization of the Frank-Starling mechanism; (2) arterial vasodilation and reduced left ventricular postload; (3) increased activity of the sympathoadrenal system (revealed by indirect data--increased heart rate and myocardial contractility). The resultant effect was determined by the initial state of circulation in the patient, the contribution of each of the named mechanisms, and the ratio of the central and peripheral effects of CO2. A hypercapnic functional-diagnostic test for appraising the vascular channel volemia and functional condition of the myocardium was elaborated on basis of the obtained data and approbated clinically. It was also shown that the diagnostic significance of LVT significantly increases under conditions of GH.