Direct oxymetric peripheral tissue perfusion monitoring during open heart surgery with the use of cardiopulmonary bypass: preliminary experience

Abstract

Background: Regional hypoperfusion has been associated with the development of postoperative organ dysfunction in cardiac surgery involving cardiopulmonary bypass (CPB). Direct tissue oxymetry is a potentially new method for monitoring the quality of the peripheral tissue perfusion during CPB. The aim of this study was to assess the effects of CPB in skeletal muscle oxygenation when measured in the deltoid muscle by direct oxymetry during perioperative period.

Method: Seven patients underwent on-pump coronary artery bypass grafting. Direct oxymetry was performed by an optical cathether introduced into the deltoid muscle. Continuous measurement was made during the surgical procedure and the postoperative period. Mean arterial blood pressure, blood flow during CPB, laboratory markers of tissue hypoperfusion, blood gases and body temperature were also recorded.

Results: Interstitial muscle tissue oxygen tension (pO₂) decreased after the introduction to anaesthesia and, more significantly, during CPB. After the disconnection from CPB at the end of the operation, the pO₂ returned to pre-anaesthetic values. During the first hours after admission of the patients to the intensive care unit, the pO₂ progressively decreased, reached a minimum value after four hours, and increased slowly thereafter. There was a significant correlation of pO₂ with mean arterial blood pressure and blood flow during that time.

Conclusion: The result of this first measurement seems to demonstrate that the standard technique of conducting cardiopulmonary bypass produces low muscle oxygen tension and, thus, little perfusion of skeletal muscle. The data also indicate that both high mean arterial blood pressure and high flow are necessary during CPB to ensure skeletal muscle perfusion. The investigation is continuing.