Propofol and Early Extubation After Cardiac Surgery

To the Editor: I believe that one of the conclusions generated from the recent clinical investigation by Myles et al. [1] that "results of this trial suggest that a propofol-based anesthetic, when compared to an enflurane-based anesthetic requiring additional dosing of fentanyl and midazolam for cardiopulmonary bypass, can lead to a significant reduction in time to extubation after coronary artery bypass grafting (CABG) surgery" is misleading. At face value, this conclusion implies that propofol facilitated early extubation in these patients after CABG, yet this is not supported by the data. The difference in extubation time between the propofol group (median 9.1 h) and the enflurane group (median 12.3 h) was statistically significant. However, the enflurane group received twice as much intravenous (IV) fentanyl (31.3 micro g/kg versus 15.1 micro g/kg, respectively) and three times as much IV midazolam (1.52 micro g/kg versus 50 micro g/kg, respectively) as the propofol group intraoperatively. Furthermore, the amount of intraoperative IV fentanyl and midazolam that both groups received makes one wonder whether they were truly "propofol-based" and "enflurane-based" techniques. In both groups, the base anesthetic (propofol or enflurane) was discontinued prior to transfer to the intensive care unit (ICU). Therefore, the extubation times of approximately 9-12 h after ICU arrival in these patients were not influenced by either propofol or enflurane (the physiologic effects of both would dissipate rapidly). The difference in extubation time between the two groups was simply caused by the different amounts of IV fentanyl and midazolam that the two groups received intraoperatively. One can accomplish safe and successful early extubation in patients after cardiac surgery without propofol. We have found that intraoperative utilization of IV fentanyl (20 micro g/kg), IV midazolam (120 micro g/kg), and supplementation with isoflurane allows patients to be extubated 3.7-12 h (mean 7.6 h) after ICU arrival after cardiac surgery [2]. Whether propofol is a useful adjunct to facilitate safe and successful early extubation in all patients after cardiac surgery remains to be determined. Although the clinical investigation by Myles et al. [1] reveals that propofol supplementation in a select group of patients undergoing CABG is safe, it does not support the conclusion that propofol facilitates early tracheal extubation. Mark A.