Bispectral index to guide induction of anesthesia: a randomized controlled study

Abstract

Background: It is unknown to what extent hypotension frequently observed following administration of propofol for induction of general anesthesia is caused by overdosing propofol. Unlike clinical signs, electroencephalon-based cerebral monitoring allows to detect and quantify an overdose of hypnotics. Therefore, we tested whether the use of an electroencephalon-based cerebral monitoring will cause less hypotension following induction with propofol.

Methods: Subjects were randomly assigned to a bispectral index (BIS)-guided (target range 40-60) or to a weight-related (2 mg.kg- 1) manual administration of propofol for induction of general anesthesia. The primary endpoint was the incidence of hypotension following the administration of propofol. Secondary endpoints included the degree of hypotension and correlations between BIS and drop in mean arterial pressure (MAP). Incidences were analyzed with Fisher's Exact-test.

Results: Of the 240 patients enrolled into this study, 235 predominantly non-geriatric (median 48 years, 25th - 75th percentile 35-61 years) patients without severe concomitant disease (88% American Society of Anesthesiology physical status 1-2) undergoing ear, nose and throat surgery, ophthalmic surgery, and dermatologic surgery were analyzed. Patients who were manually administered propofol guided by BIS (n = 120) compared to those who were given propofol by weight (n = 115) did not differ concerning the incidence of hypotension (44% vs. 45%; p = 0.87). Study groups were also similar regarding the maximal drop in MAP compared to baseline (33% vs. 30%) and the proportion of hypotensive events related to all measurements (17% vs. 19%). Final propofol induction doses in BIS group and NON-BIS group were similar (1.93 mg/kg vs. 2 mg/kg). There was no linear correlation between BIS and the drop in MAP at all times (r < 0.2 for all) except for a weak one at 6 min (r = 0.221).

Conclusion: Results of our study suggest that a BIS-guided compared to a weight-adjusted manual administration of propofol for induction of general anesthesia in non-geriatric patients will not lower the incidence and degree of arterial hypotension.

Trial registration: German Registry of Clinical Trials ( DRKS00010544 ), retrospectively registered on August 4, 2016.

Keywords: Anesthesia; Bispectral index; Electroencephalogram; Hemodynamics; Hypotension; Induction; Propofol.

Conflict of interest statement

Ethics approval and consent to participate

This trial was approved by the local ethics committee (Medical faculty of Marburg University; approval number: 109/10; 23 August 2010). Written informed consent to participate was obtained from all patients prior to inclusion into the study.

Competing interests

D.R. and H.W. have received honoraria from Covidien Deutschland for lectures.

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Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1

Interventions and measurements included in the study protocol. Legend: HR: Heart rate. NIBP: Non-invasive blood pressure. SpO2:Peripheral oxygen saturation measured by pulse oximetry. BIS: Bispectral index. aIn patients with a body mass index (BMI) > 25 the volume infused was constrained to the weight corresponding to a BMI of 25, bFentanyl 0.2 mg and in patients > 70 years or < 55 kg fentanyl 0.1 mg, cAt the discretion of the anesthetist usually done by checking the verbal response, the response to light touch and if eyelash reflex is abolished, dDose of additional propofol at the discretion of the anesthetist, eNeuromuscular blocking agents were applied at the discretion of the anesthetist

Fig. 2

CONSORT study flow diagram

Fig. 3

Mean arterial pressure over time. Legend: Box-plot of mean arterial pressures of BIS group (blue) and NON-BIS group (green) during the study period. While the bottom and the top of the box represent the first and third quartile, whiskers represent the 10th and the 90th percentile. The line in the middle of the box indicates the median and the notches of the box show the 95% confidence interval of the median

Fig. 4

BIS-indices over time. Legend: Box-plot of BIS- indices of BIS group (blue) and NON-BIS group (green) during the study period. While the bottom and the top of the box represent the first and third quartile, whiskers represent the 10th and the 90th percentile. The line in the middle of the box indicates the median and the notches of the box show the 95% confidence interval of the median