Altered Hemodynamic, Humoral, and Metabolic Conditions in Nonpulsatile Systemic Circulation

Acute-phase changes in hemodynamic, hormonal, and metabolic conditions after deputation of systemic circulation were investigated in 25 anesthetized goats. A total left heart bypass was instituted between the left atrium and ventricle and the descending aorta with an extracorporeal circuit consisting of pulsatile and nonpulsatile blood pumps. The blood flow rate was finely controlled to maintain the minimum level that allowed total left heart bypass. In this experimental setting, the character of systemic flow was rapidly converted from pulsatile to nonpulsatile mode, and the hieasurements were made 5 min before and 5 min after the deputation. Blood flow rates stayed at the rather low levels of 62.2 ± 15.3 and 62.5 ± 15.4 ml · min-1 · kg-1 in the pulsatile and nonpulsatile modes, respectively. The mean aortic pressure increased from 99 ± 3 to 107 ± 3 mmHg and norepinephrine concentration rose from 300 ± 39 to 373 ± 53 pg/ml, strongly indicating that the sympathetic tone was comparatively high in the initial stage of nonpulsatile circulation. Despite keeping oxygen delivery constant at depulsation, the total oxygen consumption dropped from 1.5 ± 0.2 to 1.0 ± 0.1 ml/min, the venous oxygen saturation increased from 78% ± 6% to 85% ±5%, and the serum lactate level increased from 34 ± 3 to 40 ± 4mg/dl. Thus, the oxygen uptake became less efficient after the depulsation. We conclude that changes in hemodynamic, hormonal, and metabolic conditions occur immediately after the depulsation of systemic circulation in anesthetized goats at relatively low blood flow rates.