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 (PscO 2 ), laser-Doppler skin red cell flux (RCF), transcutaneous PO 2 (PtcO 2 ) and fingertip temperature (Tft) in the upper extremity. During cardiopulmonary bypass (CPB) at the deepest hypothermia, pHi, PaO 2 and PtcO 2 reached maximum values simultaneously with the lowest calculated oxygen utilization: pHi reached its minimum at the end of the operation. During CPB, PscO 2 , 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, PtcO 2 index (=PtcO 2 /PaO 2 ) and other peripheral tissue perfusion parameters gained the lowest values indicating impending residual hypothermia and tissue hypoperfusion after rewarming.

Cardiopulmonary bypass—organ blood flow and metabolism in the pediatric patient

“…12 ' 86 When going from conditions of high to low flow, we saw that the percentage of flow to the femoral artery dropped but that it was still above baseline. 8 This is in agreement with the clinical study by Kuttila et al 65 that showed that peripheral perfusion, as measured by the flux of red cells, was essentially unchanged with lowflow and hypothermic bypass. With rewarming during bypass at the high rate of flow, the percentage of flow to the femoral artery and skeletal muscle is seen to decline to baseline levels.…”

“…Fantini et al, 87 however, in examining the function of membranes in skeletal muscle in dogs, found that function during high flow and hypothermia was similar to baseline, but decreased significantly when low-flow and hypothermia was used. The data of Kuttila and associates 65 are somewhat ambiguous, as they found increased transcutaneous but decreased subcutaneous tensions of oxygen during low-flow and hypothermic bypass. During rewarming, we 8 found that consumption and extraction of oxygen increased to those values measured during the initial phase of high flow and warming, even though the average temperature of the muscle had only returned to roughly 35 °C at the end of the 45-minute period of rewarming.…”

“…During rewarming, we 8 found that consumption and extraction of oxygen increased to those values measured during the initial phase of high flow and warming, even though the average temperature of the muscle had only returned to roughly 35 °C at the end of the 45-minute period of rewarming. Kuttila et al 65 found that during and after rewarming on bypass the transcutaneous tension of oxygen declined. They further demonstrated that, when the wounds were being closed, those parameters of peripheral tissue perfusion reached a nadir.…”

“…Minimal edema occurs if 3% albumin is added to the crystalloid prime. 64 Additionally, in a study performed in humans, Kuttila et al, 65 used a gastric tonometer to measure gastric intramucosal pH, which is a recognized parameter of adequacy of perfusion. They found that, during hypothermic bypass, the intramucosal pH was at its highest, that is, the safest level.…”