Electroencephalographic assessment of infant spinal anesthesia: A pilot prospective observational study

Abstract

Introduction: Spinal anesthesia is utilized as an alternative to general anesthesia in infants for some surgeries. After spinal anesthesia, infants often become less conscious without administration of sedative medications. The aim of this study was to assess electroencephalographic (EEG) correlates after spinal anesthesia in a cohort of infants.

Patients and methods: This pilot study included 12 infants who underwent spinal anesthesia. Unprocessed electroencephalography was recorded. The electroencephalogram was interpreted by four neurologists. Processed analyses compared electroencephalogram changes 30 min after spinal anesthesia to baseline.

Results: Following spinal anesthesia, all 12 infants became sedated. Electroencephalography in all 12 demonstrated Stage 2 sleep with the appearance of sleep spindles (12-14 Hz) in the frontal and central leads in 8/12 (67%) of subjects. The median time to onset of sleep spindles was 24.7 interquartile range (21.2, 29.9) min. The duration of sleep spindles was 25.1 interquartile range (5.8, 99.8) min. Voltage attenuation and background slowing were the most common initial changes. Compared to baseline, the electroencephalogram 30 min after spinal anesthesia showed significantly increased absolute delta power (p = 0.02) and gamma power (p < 0.0001); decreases in beta (p = 0.0006) and higher beta (p < 0.0001) were also observed. The Fast Fourier Transform power ratio difference for delta/beta was increased (p = 0.03). Increased coherence was noted in the delta (p = 0.02) and theta (p = 0.04) bandwidths.

Discussion: Spinal anesthesia in infants is associated with increased electroencephalographic slow wave activity and decreased beta activity compared to the awake state, with appearance of sleep spindles suggestive of normal sleep. The etiology and significance of the observed voltage attenuation and background slowing remains unclear.

Conclusions: The EEG signature of infant spinal anesthesia is distinct from that seen with general anesthesia and is consistent with normal sleep. Further investigation is required to better understand the etiology of these findings. Our preliminary findings contribute to the understanding of the brain effects of spinal anesthesia in early development.

Keywords: anesthesia; electroencephalography; infant; sedation; sleep; spinal.

Figure 1.

Unprocessed EEG tracings. A. An example of an EEG during the awake state in a 3 month old male infant. B. Diffuse slowing with sleep spindles in frontal leads (dashed red line) in a 3 month old male. C. Diffuse slowing with sleep spindles in central leads (dashed red lines) in a 4 month old male. D. As sleep continues, diffuse delta activity indicative of stage III of sleep is seen in a 7 month old male.

Figure 2.

Density Spectral Array. Density of spectral power (color coded for percentage of total power as a function of frequency) over an 8-minute period showing transition from the awake state to stage 2 of sleep. Central electrodes from the left (L) and right (R) hemispheres are displayed. Sleep spindles (12–14 Hz) are denoted by the asterisks and the faint yellow density measures.

Figure 3.

Absolute and relative power percent differences between awake and post-SA EEG. A Graphic of group differences in the major bandwidths between the awake and post-SA (30 min) recording. The top panel shows absolute power differences and the bottom panel relative power differences. The figures show the changes in absolute and relative power between the awake and post-SA states. Note increases in slow frequencies and decreases in fast frequencies with SA. B. Graphs of total absolute power comparing the awake and post-SA EEG. High beta and gamma bands are included in the graphs.

Figure 4.

FFT power ratio differences from awake to 30 min following SA. A. Delta/theta, theta/alpha, theta/beta and alpha/beta power ratios 30 minutes post-SA, as compared to the awake recording. B. Compared to the awake state, the delta/beta ratio was significantly higher 30 minutes post-SA than during the awake state.

Figure. 5.

Comparison of coherences between bandwidths during the awake and post-SA EEG. There was an increase in delta (t=2.870, df=11, p=0.024) and theta (t=2.462, df=11, p=0.043) coherence in the post-SA EEG compared to the awake state.