Monitoring aortic root effluent during retrograde cardioplegia delivery

Abstract

Continuous monitoring of myocardial protection during aortic crossclamping is not always performed, due to limitations with current technology. The purpose of this study was to use readily available technology to evaluate the effectiveness of retrograde cardioplegia delivery by monitoring the aortic root vent effluent.

The CDI 400, a commonly used blood monitoring device, was used to monitor changes in temperature, pO₂, pCO₂, and pH by placing a 1/4-inch CDI Quick Cell and probe in the aortic root vent line prior to each case. Twenty adult patients undergoing coronary bypass surgery were involved in the study, which resulted in 48 doses of retrograde cardioplegic solution. The study revealed a significant correlation between the temperature of the cardioplegia solution and the temperature of the aortic root effluent (p <0.001, r = 0.88). The cardioplegia temperature did not correlate with the change in effluent pO₂ (p = NS) or the degree of effluent temperature change (p = NS). Furthermore, the change in effluent temperature was not influenced by the amount of cardioplegia solution delivered (p = NS), or the time between administrations (p = NS). Both the decreasing and increasing trends of the effluent pO₂ significantly correlated with the cardioplegia solution flow rate (p = 0.034, r = 0.32 and p = 0.013, r = 0.37, respectively), but not with the time between doses (p = NS) or volume of cardioplegia solution delivered (p = NS). The increase in effluent pO₂ did correlate with the coronary sinus pressure (p < 0.001, r = 0.48).

Measuring aortic root vent effluent may be used to assure the successful delivery of retrograde cardioplegic solution and aid in the detection of various procedural problems. Once the trends from this technique are established by the surgical team, they may be used to adjust cardioplegic solution administration and provide documentation of myocardial protection.