Objective. Coronary artery bypass graft surgery (CABG) is associated with postoperative respiratory depression. The primary endpoint of this study was the determination whether the blood pressure variability during the intensive care unit (ICU) is correlated with the nadir of postoperative respiratory function impairment.
Methods. This prospective study evaluated 44 patients subjected to CABG with cardiopulmonary bypass (CPB). Mean arterial pressure (MAP) was monitored every 30 min for 3 days at the ICU. MAP variability was evaluated through: standard deviation (SD), coefficient of variation (CV), variation independent of mean (VIM), average successive variability (ASV) and SD of ASV. Respiratory function was assessed through maximal inspiratory (MIP) and expiratory (MEP) pressures and expiratory peak flow rate (EPFR) determined 1 day before surgery and on the postoperative days 3rd to 7th.
Results. Respiratory parameters MIP, MEP and EPFR were significantly depressed postoperatively for 4, 4 and 5 days respectively. Patient adherence to EPFR monitoring was higher than for MIP and MEP. None of the perioperative parameters (volume of cardioplegia, CPB duration, aortic cross-clamp time, number of grafts) had any correlation with the postoperative respiratory depression. Of all MAP variability parameters, the ASV and SD of ASV had a significant good positive Spearman correlation (rho coefficients ranging from 0.45 to 0.65, p<0.01) with the nadir depression of EPFR for 5 days after cardiac surgery.
Conclusion. Variability parameters ASV and SD of ASV of the MAP monitored at ICU may have predictive value for the depression of respiratory function after cardiac surgery as determined by EPFR.