Overnight declarative memory consolidation and non-rapid eye movement sleep electroencephalographic oscillations in older adults with obstructive sleep apnea.

STUDY OBJECTIVES: To compare overnight declarative memory consolidation and non-rapid eye movement (NREM) sleep electroencephalogram (EEG) oscillations in older adults with obstructive sleep apnea (OSA) to a control group and assess slow-wave activity (SWA) and sleep spindles as correlates of memory consolidation. METHODS: Forty-six older adults (24 without OSA and 22 with OSA) completed a word-pair associate's declarative memory task before and after polysomnography. Recall and recognition were expressed as a percentage of the morning relative to evening scores. Power spectral analysis was performed on EEG recorded at frontal (F3-M2, F4-M1) and central (C3-M2, C4-M1) sites. We calculated NREM absolute slow oscillation (0.25-1 Hz) and delta (0.5-4.5 Hz) EEG power, and slow (11-13 Hz) spindle density (number of events per minute of N2 sleep) and fast (13-16 Hz) spindle density. RESULTS: There were no significant differences in overnight recall and recognition between OSA (mean age 58.7 ± 7.1 years, apnea-hypopnea index (AHI) 41.9 ± 29.7 events/hour) and non-OSA (age 61.1 ± 10.3 years, AHI 6.6 ± 4.2 events/hour) groups. The OSA group had lower fast spindle density in the frontal region (p = 0.007). No between-group differences in SWA were observed. In the Control group, overnight recognition positively correlated with slow spindle density in frontal (rho = 0.555, p = 0.020) and central regions (rho = 0.490, p = 0.046). Overnight recall was not related to SWA or spindle measures in either group. CONCLUSIONS: Older adults with OSA had deficits in fast sleep spindles but showed preserved overnight declarative memory consolidation. It is possible that compensatory mechanisms are being recruited by OSA patients to preserve declarative memory consolidation despite the presence of sleep spindle deficits.

The addition of a small-dose ketamine infusion to tramadol for postoperative analgesia: a double-blinded, placebo-controlled, randomized trial after abdominal surgery.

BACKGROUND: There are few data on combining ketamine with tramadol for postoperative analgesia in humans. We tested the hypothesis that adding ketamine to tramadol would improve analgesia after major abdominal surgery. METHOD: In this double-blind, randomized, controlled trial, adult patients (n = 120) having elective laparotomy were randomly assigned to a ketamine group (intraoperative ketamine 0.3 mg/kg and postoperative infusion at 0.1 mg x kg(-1) x h(-1) or control group (equivalent volume/rate of normal saline). All patients received intraoperative tramadol 3 mg/kg and a tramadol infusion (0.2 mg x kg(-1) x h(-1) for 48 h postoperatively and had morphine patient-controlled analgesia available for rescue analgesia. RESULTS: The ketamine group had less pain at rest (P = 0.01) and with movement (P = 0.02) and required less morphine (P = 0.003) throughout the 48-h study period. In the 0-24 h period, ketamine improved subjective analgesic efficacy (P = 0.008), was less sedating (P = 0.03), and required fewer physician interventions to manage severe pain (P = 0.01). Hallucinations were more common in ketamine patients, but other side effects were similar. CONCLUSION: Small-dose ketamine was a useful addition to tramadol and morphine after major abdominal surgery.