Visceral and peripheral tissue perfusion during hypothermic cardiac surgery

Abstract

Central haemodynamics, blood gases, visceral and peripheral tissue perfusion and oxygenation were studied in six patients undergoing coronary artery bypass grafting (CABG) - including one patient with aortic valve reconstruction and another with CABG and aortic valve reconstruction. The patients were operated upon under moderate haemodilution and systemic hypothermia. Visceral perfusion was indirectly assessed by determining the gastric intramucosal pH (pHi). Peripheral tissue perfusion was assessed by continuous recording of subcutaneous tissue PO 2 (PscO2), laser-Doppler skin red cell flux (RCF), transcutaneous PO2 (PtcO2) and fingertip temperature (Tft) in the upper extremity. During cardiopulmonary bypass (CPB) at the deepest hypothermia, pHi, PaO2 and PtcO2 reached maximum values simultaneously with the lowest calculated oxygen utilization: pHi reached its minimum at the end of the operation. During CPB, PscO2, RCF and Tft decreased markedly, rose during rewarming and fell again at the end of surgery. These data suggest that the patients' visceral perfusion is well maintained during CPB, and the patients develop hypoperfusion and hypoxia of peripheral tissues at the same time. After closing the wounds, pHi, PtcO2 index (=PtcO 2/PaO2) and other peripheral tissue perfusion parameters gained the lowest values indicating impending residual hypothermia and tissue hypoperfusion after rewarming.