Duration and Depth of Anesthesia Induced by a Bolus of Etomidate

Study Overview
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Brief Summary
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Induction of general anesthesia requires to be safe and to ensure a proper level of anesthesia. A proper anesthesia is sufficient to guarantee loss of consciousness and amnesia and without being too depth leading to a electroencephalogram (EEG) with burst suppression. The depth of anesthesia is monitored by the bispectral index analyse of the EEG, this allows to detect any under- or over-dose of anesthesia. The monitoring works with an unknown algorithm (patent), which evaluate the state of consciousness in the patient. Etomidate and propofol are commonly use to ensure general anesthesia. Actually, really few litterature has objective informations about the monitoring of Etomidate. The few existant are the old ones and has just a clinical evaluation of the depth of anesthesia (loss of consciousness, loss of breathing, loss of palpebral reflex). Except the fact that these clinical evaluations come from the brain stem, and in fact are not reliable to assess the cortical activity which is reduced by etomidate. Therefore, some anesthetists are fearful that etomidate is not sufficient to ensure a proper anesthesia to intubate the patient. This interventionnal study has two purpose. Firstly, a survey will be conduct about the habits and beliefs when use of etomidate. Secondly, a prospective study will be conduct to monitore with the bispectral index the depth and duration of anesthesia with etomidate.

Detailed Description
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Protocol with randomization in one of the 2 arms (0.2 vs. 0.3 mg / kg of etomidate), blind to the investigators. The right dosage will be prepared at the same time by a colleague anesthetist who will not participate in the study according to the randomization envelope that we will give to him earlier. To remain blind to this dosage, it will be diluted with physiological serum up to 30 ml. These following procedures will be carried out in order: - Preparation by a colleague of the adequate dose of etomidate, reduced to 20 cc with physiological serum. No premedication with benzodiazepines (xanax). Standard monitoring (ECG + NIBP + SpO2) Monitoring the depth of anesthesia by bispectral analysis of the electroencephalography (BIS) trace Placement of a peripheral venous line (18 or 20 G) at the bend of the elbow (vein of good size to avoid potential discomfort during the injection of etomidate). Preoxygenation with a face mask Start remifentanil (20 μg / ml) in AIVOC mode with a site-effect concentration (Cet) of 2 μg / ml) and wait for an equilibration. Injection of the induction dose of etomidate over 30 seconds. After loss of consciousness, curarisation with 0,6 mg/kg (rocuronium). Observation period of the depth of anesthesia. Ventilation support by light ventilation with a face mask. Special attention will be paid to avoid any interference with the BIS recording (do not move the patient to set it up, do not turn on the heating blanket). When the BIS rises above 60, the study stops. The anesthesia is then deepened by administration of propofol and is left to the discretion of the anesthesiologist in charge of the room.

Official Title
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Evaluating Duration and Depth of Anesthesia by Bispectral Index Induced by an Induction Dose of Etomidate.

Conditions
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Anesthesia

Intervention / Treatment
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* Drug: induction by Etomidate bolus


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: ASA I, ASA II, schedule for minor or moderate surgery. Exclusion Criteria: Dependance to alcohol, to drugs, morphinique or psychotrop. Epilepsia of severe CNS impairement Body weight <70% or >130% to ideal body weight.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 74 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Etomidate 0,2 mg/kg<br>8 patients recruited, to receive an injection of bolus of Etomidate at dosage 0,2 mg/kg, | Drug: induction by Etomidate bolus<br>* General anesthesia induction by Etomidate bolus with different concentration in either of the two arms. First arm, has the concentration (0,2 mg/kg) commonly used of Etomidate to induce anesthesia. Second arm, has the concentration (0,3 mg/kg) usually proposed in medical literature.<br>|
| Experimental: Etomidate 0,3 mg/kg<br>10 patients recruited, to receive an injection of bolus of Etomidate at dosage 0,3 mg/kg | Drug: induction by Etomidate bolus<br>* General anesthesia induction by Etomidate bolus with different concentration in either of the two arms. First arm, has the concentration (0,2 mg/kg) commonly used of Etomidate to induce anesthesia. Second arm, has the concentration (0,3 mg/kg) usually proposed in medical literature.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| time to loss of consciousness | Time for loss of consciousness after etomidate administration | During general anesthesia induction | 
| time to loss of palpebral reflex | Time to loss of palpebral reflex after etomidate administration | During general anesthesia induction | 
| Time for BIS decrease < 60 | Time for BIS decrease < 60 after etomidate administration | During general anesthesia induction | 
| Duration of adequate general anesthesia | Time spent with a bis < 60 after etomidate administration | During general anesthesia induction | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Presence of secondary effect of etomidate, about presence of myoclonia | Myoclonia | During first 15 minutes of general anesthesia |