Do plasma catecholamines influence microcirculatory blood flow in cardiac surgery patients?

Abstract

To investigate whether plasma catecholamines influence blood flow on the microcirculatory level, forehead and forearm skin blood flow was measured by a two-channel laser Doppler blood flux monitor in 50 patients undergoing aortocoronary bypass grafting. Macrohaemodynamics, plasma viscosity, and skin temperatures were additionally monitored. Plasma catecholamines (adrenaline [AD] and noradrenaline [NOR] ) were determined using high-pressure liquid chromatography (HPLC) from arterial blood samples.

In the prebypass period, blood concentrations of both catecholamines increased slightly showing a wide range of values (AD ranging from 3 to 955 pg/ml; NOR ranging from 27 to 5326 pg/ml). In spite of the tremendous increase in plasma catecholamines before and after bypass, laser Doppler flow (LDF) remained almost stable in this period. Neither LDF nor macrocirculatory parameters were correlated to plasma catecholamines. Cardiopulmonary bypass (CPB) resulted in a significant increase in catecholamines (AD ranging from 80 to 2480 pg/ml; NOR ranging from 188 to 9898 pg/ml). Although haematocrit and plasma viscosity were significantly reduced during CPB, LDF decreased in comparison to baseline values (LDF forehead: -25%; LDF forearm: -35%) (p<0.05).

It is concluded that plasma catecholamine levels were markedly changed during cardiac surgery showing a wide range of concentrations. Microcirculatory flow assessed by laser Doppler remained almost unaffected by these alterations and was not correlated to AD or NOR plasma concentrations. However, during CPB a significant increase in catecholamines can contribute to the risk of microperfusion abnormalities which can be assessed by laser Doppler technique.