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Changes in BIS Variability Reflect Changes in Remifentanil Infusion During Spinal Surgery

Changes in BIS Variability Reflect Changes in Remifentanil Infusion During Spinal Surgery . Marc J. Bloom, MD, PhD Alex Bekker, MD, PhD Chandran V. Seshagiri, PhD and Scott D. Greenwald, PhD Presented at the American Society of Anesthesiologists (ASA) 2008 Annual Meeting.

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Changes in BIS Variability Reflect Changes in Remifentanil Infusion During Spinal Surgery

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  1. Changes in BIS Variability Reflect Changes in Remifentanil Infusion During Spinal Surgery Marc J. Bloom, MD, PhD Alex Bekker, MD, PhD Chandran V. Seshagiri, PhD and Scott D. Greenwald, PhDPresented at the American Society of Anesthesiologists (ASA) 2008 Annual Meeting. October 18–22, 2008, Orlando, FL.

  2. Background • Measures of electroencephalogram (EEG) variability increase in response to intraoperative somatic stimuli • This increased variability may indicate a lack of adequate anti-nociception • Bispectral Index monitoring/BIS translates information from the EEG into a single number that represents each patient's level of consciousness • The BIS value ranges from 100 (indicating an awake patient) to zero (indicating the absence of brain activity) • Using the BIS value to guide administration of anesthetic medication, clinicians can make informed decisions for optimal anesthesia • This technology has the potential to prevent oversedation, but is currently not a standard monitoring device Bloom M.J., et. al. American Society of Anesthesiologists (ASA) 2008 Annual Meeting. October 18–22, 2008, Orlando, FL.

  3. Background: Example BIS Trend On Off On Off Bloom M.J., et. al. American Society of Anesthesiologists (ASA) 2008 Annual Meeting. October 18–22, 2008, Orlando, FL.

  4. Purpose Since opioids are commonly associated with suppressing responses to noxious stimulation, the purpose of this study is to determine whether the opioid remifentanil affects three previously defined measures of EEG variability, sBIS, sEMG, and CVI, during surgery Bloom M.J., et. al. American Society of Anesthesiologists (ASA) 2008 Annual Meeting. October 18–22, 2008, Orlando, FL.

  5. Methods Data collected from a BIS monitor from a previously published, IRB-approved study consisting of 11 patients undergoing spinal surgery were analyzed General anesthesia was induced with propofol, remifentanil bolus (0.5mg/kg) followed by infusion (0.25 mg /kg/min), and vecuronium Anesthesia was maintained by propofol infusions titrated to maintain a target BIS of 40 Bloom M.J., et. al. American Society of Anesthesiologists (ASA) 2008 Annual Meeting. October 18–22, 2008, Orlando, FL.

  6. Patients were randomized to one of two groups Group 1: the remifentanil infusion was maintained until 30 minutes after surgical incision when it was discontinued Group 2: the remifentanil infusion was discontinued prior to incision and then resumed 30 minutes after incision Two cases continued long enough to include a second cycle of 30 minute remifentanil on and off periods Methods Bloom M.J., et. al. American Society of Anesthesiologists (ASA) 2008 Annual Meeting. October 18–22, 2008, Orlando, FL.

  7. BIS and EMG (power from 70-110Hz) values were continuously recorded throughout the case To quantify the EEG variability, the following were calculated offline for each case: standard deviations of BIS (sBIS) and EMG (sEMG) computed over a sliding 3 minute window Composite Variability Index (CVI), a weighted combination of BIS, sBIS, and sEMG Methods Bloom M.J., et. al. American Society of Anesthesiologists (ASA) 2008 Annual Meeting. October 18–22, 2008, Orlando, FL.

  8. For each patient, pairs of observation periods of equal duration when remifentanil infusion was on and off were identified All observation periods started five minutes after the change in remifentanil rate To compare the effects of remifentanil on EEG variability, the mean sBIS, sEMG, and CVI values were computed for each observation period and a paired t-test was used to compare the change in mean values between infusion on and infusion off states P < 0.05 was considered statistically significant Methods Bloom M.J., et. al. American Society of Anesthesiologists (ASA) 2008 Annual Meeting. October 18–22, 2008, Orlando, FL.

  9. Results For 13 paired observations from 11 patients, mean BIS, sBIS, and CVI were statistically lower during periods of remifentanil infusion compared to periods with no infusion BIS: p=0.014 sBIS: p=0.001 CVI: p=0.002 Mean sEMG was numerically lower during remifentanil infusion, but the difference did not reach significance Bloom M.J., et. al. American Society of Anesthesiologists (ASA) 2008 Annual Meeting. October 18–22, 2008, Orlando, FL.

  10. Results Bloom M.J., et. al. American Society of Anesthesiologists (ASA) 2008 Annual Meeting. October 18–22, 2008, Orlando, FL.

  11. Conclusions Measures of EEG variability have previously been associated with both intraoperative somatic responses and postoperative pain scores These results indicate that sBIS and CVI are lowered by the addition of the opioid remifentanil Further studies are needed to assess whether these measures of EEG variability could be used to monitor the anti-nociceptive effects of anesthesia Bloom M.J., et. al. American Society of Anesthesiologists (ASA) 2008 Annual Meeting. October 18–22, 2008, Orlando, FL.

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