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October 14, 2018
10/14/2018 7:30:00 AM - 10/14/2018 9:30:00 AM
Room North, Hall D, Area C
Impact of Intravenous Phenylephrine Bolus on Intraoperative NOL Index Values
Philippe G. Richebe, M.D.,Ph.D., Véronique Brulotte, M.D., M.S., Marie-Andree Coulombe, Ph.D., Etienne Renaud-Roy, M.D., Omar Elsemin, Student, Manon Choiniere, Ph.D., Pierre Drolet, M.D., FRCPC, Louis-Philippe Fortier, M.D., M.S., Olivier Verdonck, M.D., M.S.
University of Montreal, Montreal, Quebec, Canada
Disclosures: P.G. Richebe: None. V. Brulotte: None. M. Coulombe: None. E. Renaud-Roy: None. O. Elsemin: None. M. Choiniere: None. P. Drolet: None. L. Fortier: None. O. Verdonck: None.
Introduction: Recently, the nociceptive level (NOL) index was developed with better sensitivity and specificity to detect noxious stimuli during general anesthesia than other parameters. An ongoing study (NCT#03410485) evaluates the intraoperative combination of both NOL+BIS indices to improve quality of recovery in an ERAS population undergoing colorectal surgery. Our ethical committee initially agreed to an interim analysis on 30 patients. More specifically, all the intravenous (IV) phenylephrine (PE) boluses administered during anesthesia as part of our protocol were compiled to see whether they have a significant impact on intraoperative NOL values. Methods: After REB approval (#CER15083) study NCT#03410485 was conducted. Remifentanil and phenylephrine were given in both groups based on a specific algorithm. NOL values were electronically recorded. Specific outcome NOL index was recorded at 5 seconds intervals starting 30 seconds before to 5 minutes after PE boluses. The peak of NOL after PE bolus was identified and mean values were constructed (5 values around each peak). Time to reach the NOL peak was also assessed. Results: A total of 179 events of PE boluses were identified for 30 patients. Median baseline NOL was 3 (1.8-8.3) IC 95% 5.7-8.7; post-PE bolus: 16 (7.6-29.7) IC 95% 16.9-21.1; Wilcoxon matched-pairs signed rank test (WMPSRT), p<0.0001. Moreover, 95.5% of patients had a pre-PE bolus NOL baseline below nociception threshold of 25. After PE bolus, 74.2% of patients kept a NOL value below 25. When comparing averaged NOL values over 30 seconds prior to PE bolus and over 120 seconds after PE bolus, median NOL baseline was 3 (1.8-8.3) IC 95% 5.7-8.7, and post-PE bolus: 5.3 (2.7-9.9) IC 95% 6.6-8.9; WMPSRT, p=0.0032. When analyzing delta NOL (difference between pre and post-PE bolus in NOL values) for each patient, median delta NOL was 2.9 (1.2-6.1) IC 95% 3.6-5.5. Also, 93% of patients presented a delta NOL under 10. Finally, median time to reach the peak for NOL value after PE bolus was 105 sec (50-195) IC 95% 109.1-134.4 and more than 80% reached this peak within 200 seconds after PE bolus. Discussion: NOL index statistically slightly increased after IV PE bolus. Nevertheless, the NOL variation stayed within a range of 10 points for 93% of patients and below the threshold of 25 in a great majority of patients. Also, the peak value of NOL after PE bolus occurred quickly within 200 seconds in more than 80% of patients and returned to normal quickly. Based on these results, anesthesiologists might consider than IV PE bolus induces no significant interference on NOL index values. Acknowledgments: Sponsored by the CARF neuroanesthesia award in 2016 and by the Medasense LTD through an IIIT. Thank you to Nadia Godin, Research Coordinator for her collaboration.

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