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UBC Theses and Dissertations

Monitoring nociception during general anesthesia with heart rate variability Brouse, Chris J.


We have developed a novel real-time cardiorespiratory coherence (CRC) algorithm to monitor nociception during general anesthesia. We have made two novel and significant contributions to the field. We have developed a novel filter for measuring the respiratory sinus arrhythmia (RSA) in the heart rate variability (HRV) in real-time. The filter uses information from a secondary signal source (a respiration rate derived from a respiration signal) to track the RSA as it moves in time and frequency. It then uses this information to dynamically tune the centre frequency and bandwidth of a band-pass filter to isolate and measure the RSA. This filter is very effective at tracking the RSA in time and frequency, and it may provide the most robust measure of RSA yet devised. We have integrated multiple signals and algorithms together into an end-to-end software system for robust continuous real-time nociception monitoring during general anesthesia. The software system incorporates not only our novel RSA filter to measure nociception, but also many peripheral algorithms for detecting and rejecting artifacts in the input signals. The input signals required for real-time nociception monitoring can be extremely noisy, and artifacts are a very significant challenge. To our knowledge, no other nociception monitor includes such robust artifact handling using redundant signal channels. We estimated the sensitivity of our real-time CRC algorithm to nociception and antinociception, and compared it to traditional univariate HRV measures and standard clinical vital signs. Following ethics approval and informed parental consent, data were collected from 48 children receiving general anesthesia during dental surgery. A total of 42 dental dam insertion (nociception) and 57 anesthetic bolus (antinociception) events were noted. A nociception index was created for each HRV algorithm, ranging from 0 (no nociception) to 100 (strong nociception). Dental dam insertion changed the CRC nociception index by an average of 27 [95% CI from 21 to 33] (P < 0.000005), and a bolus dose of anesthetic changed it by an average of -19 [-27 to -12] (P < 0.00003). Real-time CRC was more sensitive to nociception and antinociception than were the traditional measures.

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Attribution-NonCommercial-NoDerivs 2.5 Canada