Pressure and oxygen debt on bypass – potential quality markers of perfusion?

Abstract

No markers of quality of perfusion pressure and oxygen delivery during cardiopulmonary bypass (CPB), to complement rewarming rate, maximum temperature on rewarming, lowest haematocrit, and blood glucose, exist. Using the electronic acquisition of blood pressure on bypass (JOCAP system), the percentage of time perfusion pressure was below 30, 40, 50, 60 and 70 mmHg, average deviance, confidence interval, median, mode, standard deviation, variance, and average, maximum and cumulative oxygen debt were calculated. Numerous different readouts of achievement of maintenance of constant pressure on bypass and oxygen debt are now easily achievable with perfusion electronic data management systems. Mean, median, and mode offer poor discrimination of pressure control during CPB. Percentage of time perfusion pressure was below 30, 40, 50, 60 and 70 mmHg, average deviance, confidence interval, and standard deviation all have discriminatory power, but need clinical correlation for their significance. A composite score involving non-pressure readouts (e.g. oxygen delivery, arterial and venous saturations, and flow rates) may need to be integrated into any perfusion quality marker. Assessment of adequacy of constant perfusion pressure and oxygen delivery may allow the scientific evaluation of pressure and oxygen delivery on bypass for patients to be compared accurately. Currently, in studies involving CPB, blood pressure targets are stated with no quantitative assessment of adequacy of achievement of these targets. Electronic data monitoring during cardiopulmonary bypass, when correlated with clinical outcome, may help to provide a marker of quality of perfusion pressure during CPB and may, indeed, allow patient-specific perfusion pressure strategies to be developed.