Pulsatile flow during cardiopulmonary bypass speeds thermal energy transfer: a possible explanation for the reduced afterdrop

The instantaneous thermal energy balance and rates of thermal energy transfer during hypothermic cardiopulmonary bypass were measured for a group of patients receiving continuous flow and compared with a group receiving pulsatile flow. Cooling was more rapid and the rate of thermal energy delivery during rewarming significantly greater in the pulsatile flow group despite similar rewarming times. The final thermal energy balance at the end of cardiopulmonary bypass was larger and the period of postoperative hypothermia shorter in those receiving pulsatile flow. The greater rate of thermal energy transfer may explain the reduced afterdrop.

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Acute Response of Human Aortic Endothelial Cells to Loss of Pulsatility as Seen during Cardiopulmonary Bypass

Cells Tissues Organs ◽

10.1159/000512558 ◽

2021 ◽

pp. 1-11

Author(s):

Khanh T. Nguyen ◽

Leslie Donoghue ◽

Guruprasad A. Giridharan ◽

Jeffrey P. Naber ◽

Doug Vincent ◽

...

Keyword(s):

Endothelial Cells ◽

Cardiopulmonary Bypass ◽

Growth Factor ◽

Pulsatile Flow ◽

Continuous Flow ◽

Short Term ◽

Aortic Endothelial Cells ◽

Short Term Exposure ◽

Flow Group ◽

Human Aortic Endothelial Cells

Cardiopulmonary bypass (CPB) results in short-term (3–5 h) exposure to flow with diminished pulsatility often referred to as “continuous flow”. It is unclear if short-term exposure to continuous flow influences endothelial function, particularly, changes in levels of pro-inflammatory and pro-angiogenic cytokines. In this study, we used the endothelial cell culture model (ECCM) to evaluate if short-term (≤5 h) reduction in pulsatility alters levels of pro-inflammatory/pro-angiogenic cytokine levels. Human aortic endothelial cells (HAECs) cultured within the ECCM provide a simple model to evaluate endothelial cell function in the absence of confounding factors. HAECs were maintained under normal pulsatile flow for 24 h and then subjected to continuous flow (diminished pulsatile pressure and flow) as observed during CPB for 5 h. The ECCM replicated pulsatility and flow morphologies associated with normal hemodynamic status and CPB as seen with clinically used roller pumps. Levels of angiopoietin-2 (ANG-2), vascular endothelial growth factor-A (VEGF-A), and hepatocyte growth factor were lower in the continuous flow group in comparison to the pulsatile flow group whereas the levels of endothelin-1 (ET-1), granulocyte colony stimulating factor, interleukin-8 (IL-8) and placental growth factor were higher in the continuous flow group in comparison to the pulsatile flow group. Immunolabelling of HAECs subjected to continuous flow showed a decrease in expression of ANG-2 and VEGF-A surface receptors, tyrosine protein kinase-2 and Fms-related receptor tyrosine kinase-1, respectively. Given that the 5 h exposure to continuous flow is insufficient for transcriptional regulation, it is likely that pro-inflammatory/pro-angiogenic signaling observed was due to signaling molecules stored in Weible-Palade bodies (ET-1, IL-8, ANG-2) and via HAEC binding/uptake of soluble factors in media. These results suggest that even short-term exposure to continuous flow can potentially activate pro-inflammatory/pro-angiogenic signaling in cultured HAECs and pulsatile flow may be a successful strategy in reducing the undesirable sequalae following continuous flow CPB.

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Thermal energy balance as a measure of adequate rewarming from hypothermic cardiopulmonary bypass

Journal of Cardiothoracic and Vascular Anesthesia ◽

10.1053/jcan.2000.7924 ◽

2000 ◽

Vol 14 (4) ◽

pp. 388-392 ◽

Cited By ~ 1

Author(s):

Charles D. Deakin ◽

Frank Clewlow ◽

J.M.Thomas Pierce

Keyword(s):

Cardiopulmonary Bypass ◽

Energy Balance ◽

Thermal Energy ◽

Hypothermic Cardiopulmonary Bypass

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Bicarbonate Requirements during Hypothermic Cardiopulmonary Bypass the Relative Effects of Pulsatile Flow

Anaesthesia and Intensive Care ◽

10.1177/0310057x7600400311 ◽

1976 ◽

Vol 4 (3) ◽

pp. 232-238 ◽

Cited By ~ 1

Author(s):

A. M. S. Black

Keyword(s):

Cardiopulmonary Bypass ◽

Pulsatile Flow ◽

Constant Flow ◽

Hypothermic Cardiopulmonary Bypass ◽

Flow Perfusion ◽

Total Body

An analysis of 541 patients having total body perfusion under hypothermia (30°–33°C) showed that the use of pulsatile as against constant flow perfusion was not associated with a reduction in bicarbonate requirement, though the use of a vasodilator was. The implications of this are discussed.

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