[Use of microstream capnography and alveolar recruitment during off-pump coronary artery bypass grafting]

The aim of the study was to investigate changes in EtCO2 and its correlation with PaCO2, and cardiac function during off-pump coronary artery bypass grafting (OPCAB) and to evaluate whether the recruitment maneuver was effective in improving gas exchange after OPCAB. Twenty adult patients scheduled for elective OPCAB were enrolled in a prospective randomized study. Anesthesia was maintained with midazolam, propofol, and fentanyl. After OPCAB the patients were randomized to a control group receiving conventional ventilation (n=10) or to a RM group (n=10) having ventilation and RM. RM was performed at min 15 after transfer to an ICU, by increasing airway pressure to 40 cm H2O for 40 sec subsequently adjusting PEEP to a level of 2 cm H2O above the lower inflection point of the pressure-volume curve. The measurements included hemodynamics, microstream capnography, respiratory parameters, and blood gasses. The baseline EtCO2 correlated with PaCO2 and cardiac index in both group (r = 0.7 and 0.81, respectively; p < 0.05). In the control group, OPCAB was followed by a rise in PaCO2 and worsening of arterial oxygenation (p < 0.05). After recruitment, EtCO, increased transiently whereas PaO2/FiO2 return to the baseline level. There was a moderate correlation between EtCO2 and PaCO2 before and after RM (r = 0.7 and 0.8, respectively; p < 0.05). The Bland-Altman analysis has shown that the difference between PaCO2 an EtCO2 was 1.9 +/- 11.4 mm Hg (M +/- 2SD). Thus, during OPCAB, EtCO2 measured by microstream capnography cor related well with PaCO2 and cardiac function. The use of RM after OPCAB increases CO2 elimination and improve arterial oxygenation.