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Background: Cerebral oxygen desaturation during cardiac surgery has been associated with adverse perioperative outcomes. Before a large multicenter randomized controlled trial (RCT) on the impact of preventing desaturations on perioperative outcomes, the authors undertook a randomized prospective, parallel-arm, multicenter feasibility RCT to determine whether an intervention algorithm could prevent desaturations., Methods: Eight Canadian sites randomized 201 patients between April 2012 and October 2013. The primary outcome was the success rate of reversing cerebral desaturations below 10% relative to baseline in the intervention group. Anesthesiologists were blinded to the cerebral saturation values in the control group. Intensive care unit personnel were blinded to cerebral saturation values for both groups. Secondary outcomes included the area under the curve of cerebral desaturation load, enrolment rates, and a 30-day follow-up for adverse events., Results: Cerebral desaturations occurred in 71 (70%) of the 102 intervention group patients and 56 (57%) of the 99 control group patients (P = 0.04). Reversal was successful in 69 (97%) of the intervention group patients. The mean cerebral desaturation load (SD) in the operating room was smaller for intervention group patients compared with control group patients (104 [217] %.min vs. 398 [869] %.min, mean difference, -294; 95% CI, -562 to -26; P = 0.03). This was also true in the intensive care unit (P = 0.02). There were no differences in adverse events between the groups., Conclusions: Study sites were successful in reversal of desaturation, patient recruitment, randomization, and follow-up in cardiac surgery, supporting the feasibility of conducting a large multicenter RCT.

Background: Recent studies of anesthetic-induced unconsciousness in humans have focused predominantly on the intravenous drug propofol and have identified anterior dominance of alpha rhythms and frontal phase-amplitude coupling patterns as neurophysiological markers. However, it is unclear whether the correlates of propofol-induced unconsciousness are generalizable to inhaled anesthetics, which have distinct molecular targets and which are used more commonly in clinical practice., Methods: The authors recorded 64-channel electroencephalograms in healthy human participants during consciousness, sevoflurane-induced unconsciousness, and recovery (n = 10; n = 7 suitable for analysis). Spectrograms and scalp distributions of low-frequency (1 Hz) and alpha (10 Hz) power were analyzed, and phase-amplitude modulation between these two frequencies was calculated in frontal and parietal regions. Phase lag index was used to assess phase relationships across the cortex., Results: At concentrations sufficient for unconsciousness, sevoflurane did not result in a consistent anteriorization of alpha power; the relationship between low-frequency phase and alpha amplitude in the frontal cortex did not undergo characteristic transitions. By contrast, there was significant cross-frequency coupling in the parietal region during consciousness that was not observed after loss of consciousness. Furthermore, a reversible disruption of anterior-posterior phase relationships in the alpha bandwidth was identified as a correlate of sevoflurane-induced unconsciousness., Conclusion: In humans, sevoflurane-induced unconsciousness is not correlated with anteriorization of alpha and related cross-frequency patterns, but rather by a disruption of phase-amplitude coupling in the parietal region and phase-phase relationships across the cortex.

The safety and efficacy of epidural morphine injected into the caudal space for control of postoperative pain following open cardiac surgery in children was studied. Thirty-two children between the ages of 2-12 yr for whom early postoperative tracheal extubation was anticipated were randomly assigned to control and study groups. Study subjects received a caudal injection of preservative free morphine sulfate (0.075 mg/kg) in preservative-free normal saline (5-10 ml) following completion of surgery, but prior to awakening and extubation of the trachea. Supplemental intravenous morphine administration and pain scores were recorded for 24 h. Patients in the study group received significantly less (P less than 0.03) morphine (0.32 mg.kg-1.24 h-1) and had significantly lower pain scores than did patients in the control group (0.71 mg.kg-1.24 h-1). The mean duration of complete analgesia in patients receiving caudally administered morphine was 6 h (range 2-12), but decreased analgesic requirements were noted for the entire 24 h. No respiratory depression was evident by clinical variables or repeated arterial blood gas values. Nausea without vomiting occurred in 4/16 patients in the study group. No patient described pruritus. The authors were unable to evaluate the occurrence of urinary retention because all patients had indwelling urinary catheters. They found caudal epidural morphine to be safe and effective in the treatment of postoperative pain in children following open heart surgery.