Abstract
Background: The level of sensory awareness during anesthesia is difficult to monitor. Near infrared spectroscopy NIRS, is a non-invasive bedside tool which allows monitoring cerebral cortical haemodynamic changes in response to different kinds of sensory stimulation.
Aim: To assess the cortical response to auditory stimulation during anaesthesia in infants undergoing elective surgery.
Methods: Water music, by Handel was presented via earphones to three infants aged between 18 and 22 months. NIRS was recorded in different conditions: baseline with no music when the child was asleep (base 1), during the music with the child sleeping before anesthesia (music 1), baseline in deep anesthesia (base 2) and during the music when the child was in deep anesthesia (music 2). HR, satO2, BP, eCO2, did not change during the study. Only small fluctuations of HbO2, HbH and Hbtot where observed during baseline conditions (these fluctuations were slightly more pronounced in base1 than base2, but not significantly different). When the music was played to the infant asleep before anaesthesia, an increase in HbO2 in both hemispheres above the illuminated cortical area (i.e. auditory cortex) was observed. After the anaesthesia was induced and the music played, there was an increase in HbO2 on the left side and a decrease on the right in all three infants (see table and figure 1).
Conclusions: NIRS has been easily used in the operation setting to monitor haemodynamic cortical responses to auditory stimulation. The observed pronounced bilateral HbO2 increase during sleeping is similar to that previously observed in awaked subjects and suggests that the infant perceives the auditory stimulus and likely process it. When the infant is under anesthesia, and many neuronal circuits are not functioning, the auditory stimulus can still be perceived as suggested by the increase of HbO2 on one hemisphere, but processing might be altered.
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Bartocci, M., Ullén, F., Sjögren, D. et al. 19 Auditory Awareness of Music During Sleep and Anesthesia. A Near Infrared Spectroscopy Study of Infants. Pediatr Res 56, 467 (2004). https://doi.org/10.1203/00006450-200409000-00042
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DOI: https://doi.org/10.1203/00006450-200409000-00042