Age dependent changes in EEG in infants under spinal anesthesia
Jerry Y. Chao, Chang A. Liu, Patrick L. Purdon
As discussed in several previous PAADs, the use of intraoperative EEG to guide the administration of intravenous and inhalational anesthetics is becoming increasingly common and to my reading will become as ubiquitous as pulse oximetry and capnography in the near future.
“Infants under spinal anesthesia appear to be sedated despite the absence of systemic sedative medications. In this prospective observational study, Santa Cruz Mercado et al.1 “investigated the electroencephalogram (EEG) of infants under spinal anesthesia and hypothesized that they would observe EEG features similar to those seen during sleep.”
Because I am an EEG novice, I asked Dr. Jerry Chao, an EEG expert and a new addition to the PAAD’s executive council to review this article for us. Myron Yaster MD
Original article
Santa Cruz Mercado LA, Lee JM, Liu R, Deng H, Johnson JJ, Chen AL, He M, Chung ER, Bharadwaj KM, Houle TT, Purdon PL, Liu CA. Age-Dependent Electroencephalogram Features in Infants Under Spinal Anesthesia Appear to Mirror Physiologic Sleep in the Developing Brain: A Prospective Observational Study. Anesth Analg. 2023 Dec 1;137(6):1241-1249. doi: 10.1213/ANE.0000000000006410. Epub 2023 Mar 7. PMID: 36881544.
Newborn spinal anesthesia is increasingly being used for infraumbilical surgeries.2,3 Infants under spinal anesthesia often appear to be sedated despite the absence of systemic sedative medications. In today’s PAAD, Santa Cruz Mercado et al. using EEG, hypothesized “that they would observe EEG features similar to those seen during sleep. Specifically, they hypothesized that they would see the appearance of spindles (12–16 Hz) in infants under spinal anesthesia, and that they would observe an increased incidence of EEG discontinuity in younger infants, particularly preterm infants who may have a predisposition to EEG discontinuity even without spinal anesthesia.”1
They performed a prospective observational study, in which the electroencephalogram (EEG) was obtained in 35 infants to describe the brain activity during spinal anesthesia and how dynamic changes in the EEG during different ages can inform our understanding of neurodevelopment. In the study, the power spectrogram of the EEG was computed and averaged across four frontal channels during periods of apparent sleep with eyes closed and no purposeful movement in infants who received spinal anesthesia.4
The median postmenstrual age of the sample was 49 weeks with 71% of the infants born at term. The predominant EEG patterns observed in the sample were: (1) slow delta (0.5-2 Hz) frequency oscillations, (2) low voltage EEG discontinuity patterns, and (3) a combination of sleep spindle activity of 12-16 Hz frequency4 and slow-delta. Study investigators then modeled the association of sleep spindles and low voltage EEG patterns as a function of age using logistic regression and found that in general, as age increased, the odds of the development of sleep spindles increased, with a 50% probably of spindle activity at 53 weeks postmenstrual age. In contrast, as gestational age increased, the odds of low voltage EEG decreased.
The study findings support the idea that the apparent sedated state observed in infants under spinal anesthesia is likely explained by sleep-like EEG patterns, with age-dependent transitions paralleling similar transitions during physiological sleep. These observations are consistent with a sleep-related mechanism for the apparent sedation during spinal anesthesia. Progressive formation and maturation of brain circuits between the thalamus and cortex (as well as between areas within the cortex) are thought to underlie the progression away from low voltage discontinuous patterns as well as the formation of sleep spindle oscillations during spinal anesthesia. The EEG is a useful tool to help describe and clarify brain correlates as well as neurodevelopmental features during early anesthesia.
What do you think about the use of EEG to guide anesthetic practice and as a research tool? Send your thoughts and comments to Myron who will post in a Friday reader response.
References
1. Santa Cruz Mercado LA, Lee JM, Liu R, Deng H, Johnson JJ, Chen AL, He M, Chung ER, Bharadwaj KM, Houle TT, Purdon PL, Liu CA: Age-Dependent Electroencephalogram Features in Infants Under Spinal Anesthesia Appear to Mirror Physiologic Sleep in the Developing Brain: A Prospective Observational Study. Anesth Analg 2023; 137: 1241-1249
2. Williams RK, Adams DC, Aladjem EV, Kreutz JM, Sartorelli KH, Vane DW, Abajian JC: The safety and efficacy of spinal anesthesia for surgery in infants: the Vermont Infant Spinal Registry. Anesth Analg 2006; 102: 67-71
3. Jones LJ, Craven PD, Lakkundi A, Foster JP, Badawi N: Regional (spinal, epidural, caudal) versus general anaesthesia in preterm infants undergoing inguinal herniorrhaphy in early infancy. Cochrane Database Syst Rev 2015: Cd003669
4. Whitaker EE, Chao JY, Holmes GL, Legatt AD, Yozawitz EG, Purdon PL, Shinnar S, Williams RK: Electroencephalographic assessment of infant spinal anesthesia: A pilot prospective observational study. Paediatr Anaesth 2021; 31: 1179-1186