Clonidine Conserves Sleep Spindle Properties and Age-Dependent Electroencephalogram Patterns Mirroring Physiologic Sleep in Infants Under Spinal Anesthesia.

BACKGROUND Spinal anesthesia is an alternative to general anesthesia in infants. A caveat of spinal anesthesia in infants is short block duration. Clonidine is a common adjunct that prolongs spinal anesthesia. The mechanisms by which clonidine prolongs spinal anesthesia are unknown. Infants under spinal anesthesia appear in a sleep-like state. We hypothesized that infants receiving bupivacaine spinal anesthesia with clonidine may exhibit more sleep spindles on the electroencephalogram (EEG). METHODS We obtained intraoperative frontal EEG recordings in 73 infants under spinal anesthesia. We compared EEG spectral features of bupivacaine and bupivacaine + clonidine spinal anesthesia using nonparametric multitaper spectral analysis. A recently developed switching state-space modeling approach was then applied to extract and compare spindle features in bupivacaine versus bupivacaine + clonidine spinal anesthesia. We then applied the same model to compare younger versus older infants. RESULTS There was no difference in the power spectra and sleep spindle detection probability between bupivacaine and bupivacaine + clonidine spinal anesthesia (P = .51). We found age-related EEG changes in both bupivacaine and bupivacaine + clonidine spinal anesthesia independent of clonidine. Increasing age was associated with decreased spectral power from 0 to 0.6 Hz (median difference -2.9 dB, 95% CI [-5.3, -0.5,]) and increased power from 2 to 15 Hz (median difference 3.4 dB, 95% CI [1.5, 5.2]). Increasing age was also associated with increased spindle strength (R2 = 0.323, F(2,67) = 15.98, P < 0.001). These EEG findings mirror those found in infants under physiologic sleep. CONCLUSIONS Our findings suggest that low-dose clonidine does not impact sleep spindle properties in the EEG of infants under spinal anesthesia. The EEG of infants under spinal anesthesia demonstrate age-related changes that mirror quiet physiologic sleep. In addition, the presence of intrathecal clonidine has no effect on the age-related changes in the EEG pattern. Clonidine is an adjunct for spinal anesthesia in infants that appears to prolong anesthetic duration without affecting their EEG patterns of physiologic sleep.