Increases in electroencephalogram and electromyogram variability are associated with an increased incidence of intraoperative somatic response.

BACKGROUND: sBIS, the variability of the Bispectral Index (BIS), sEMG, the variability of facial electromyogram power (EMG), and the Composite Variability Index (CVI) are 3 new measures of electroencephalogram and EMG variability. CVI is a single measure of the combined variability in BIS and EMG. We investigated whether increases in these variables are associated with intraoperative somatic responses. METHODS: This multicenter study included 120 patients undergoing elective, noncardiac surgery from 4 different sites. General anesthesia was maintained using propofol and remifentanil at 2 of the sites and sevoflurane and remifentanil at the 2 other sites. Propofol or sevoflurane was adjusted to maintain BIS between 45 and 60. Clinicians were blinded to CVI (v2.0) at all times, and remifentanil infusions were adjusted at the discretion of the clinician. The times of all intraoperative somatic events, defined as movement, grimacing, or eye opening, were recorded. Offline, the maintenance phase of each case was divided into consecutive, nonoverlapping, 10-minute segments. Segments were identified as containing a somatic event or containing no events. For each segment, mean sBIS, sEMG, and CVI and the heart rate (HR) range and mean arterial blood pressure range were calculated. To quantify how effectively each variable discriminated between somatic event segments and nonevent segments, we computed the area under the receiver operating characteristic (ROC) curve for each variable. Finally, we observed the time course of sBIS, sEMG, CVI, and the HR range before each somatic event and characterized the earliest time before the somatic event at which each variable was able to discriminate between the somatic events and a specified set of nonevents. RESULTS: The analysis included 33 somatic event segments and 829 nonevent segments from 105 surgical cases. The areas under the ROC curve (±SE) for sBIS, sEMG, and CVI were 0.83 ± 0.04, 0.92 ± 0.02, and 0.89 ± 0.03, respectively. The areas under the ROC curve for HR range and mean arterial blood pressure range were 0.77 ± 0.03 and 0.68 ± 0.05, respectively. CVI, sBIS, and sEMG all demonstrated higher average values before upcoming somatic events when compared with nonevents. HR range only showed a difference within a few seconds before the somatic event. CONCLUSION: sBIS, sEMG, and CVI, measures of electroencephalogram and EMG variability, increased when intraoperative somatic events occurred. sBIS, sEMG, and CVI discriminated between 10-minute segments that contained a somatic event and those segments that did not contain an event better than changes in HR and mean arterial blood pressure. Furthermore, CVI increases before somatic events began earlier than HR changes and may provide caregivers with an early warning of potentially inadequate antinociception.

The effects of sevoflurane or remifentanil on the stress response to surgical stimulus.

Tissue injury secondary to surgical lesion produces profound changes in endocrine-metabolic function and defence mechanisms in the patient (inflammatory, immunological), leading to an increase in catabolism, immunosuppression and postoperative morbidity. The best anaesthetic and surgical technique should be capable of modulating this response, especially in major surgery, where it can be most harmful and increase patient morbidity. Many of the changes that maintain homeostasis are controlled by the hypothalamicpituitary- adrenal axis. The autonomic-adrenal response is usually immediate, compared to the hypothalamus-pituitary gland, which is slower and longer lasting. Cytokine synthesis and release are the earliest stages in the response to tissue lesion. The most frequently studied cytokines in surgical stress response are IL-6 and TNF-α. Inflammatory mediator concentrations are direct indicators of perioperative stress, while haemodynamic changes are considered the indirect indicators of this response. Multiple anaesthetic techniques have been described to modify the stress response in patients undergoing elective surgery. The aim of this review is to present clinical evidence on perioperative stress modulation with different anesthetics. We also describe a different point of view in immunomodulation with the intraoperative management of haemodynamic responses with inhalational bolus of sevoflurane or with remifentanil intravenous bolus. The effects of sevoflurane used as an inhalational bolus to counteract patients' intraoperative haemodynamic responses modulates the immune response the same than opioid remifentanil.

An inhalation bolus of sevoflurane versus an intravenous bolus of remifentanil for controlling hemodynamic responses to surgical stress during major surgery: a prospective randomized trial.

UNLABELLED: We studied 120 patients scheduled for elective major thoracic or abdominal surgery, randomized into 2 groups: a Sevoflurane group (n = 63) and a Remifentanil group (n = 57). Heart rate (HR) and mean arterial pressure (MAP) are indicative of sympathetic response to surgical stress. A positive response was defined as a 15% increase in the HR and MAP above baseline measurements. When a positive response occurred, in the Sevoflurane group we administered a bolus dose of 8% sevoflurane (fresh gas flow 6 L/min) and in the Remifentanil group, an IV bolus dose of remifentanil 1 microg x kg(-1) x min(-1), which was maintained until MAP and HR returned to baseline measurements (effective bolus). If, after a bolus dose, a decrease in MAP and/or HR of >15% occurred with respect to baseline values, the response was considered to be excessive. The bolus dose was ineffective in 4.8% of the responses in the Sevoflurane group and in 17.8% of the responses in the Remifentanil group (P < 0.05). In the Sevoflurane group, an excessive effect occurred in 12% of responses, and in 26.7% in the Remifentanil group (P < 0.05). An inhalation bolus of sevoflurane seems to be more effective than an IV remifentanil bolus during maintenance, with more effective control of hemodynamic responses to surgical stress. IMPLICATIONS: We compared an inhalation bolus of sevoflurane with remifentanil for managing hemodynamic responses to major abdominal or thoracic surgery. This prospective, randomized trial demonstrated better results with sevoflurane.