Awareness during laryngoscopy and intubation: quantitating incidence following induction of balanced anesthesia with etomidate and cisatracurium as detected with the isolated forearm technique.
OBJECTIVE
To measure the incidence of awareness during induction of anesthesia with etomidate and fentanyl, and to model its frequency as a function of dose of etomidate.


METHODS
Prospective cohort study.


METHODS
Anesthesia department of a university hospital.


METHODS
30 ASA physical status I, II, and III patients undergoing elective general surgery.


METHODS
Patients were assigned to one of three groups of etomidate (0.2 mg/kg, 0.3 mg/kg, 0.4 mg/kg) and received fentanyl (2 microg/kg) and 2 x ED(95) of cisatracurium (0.1 mg/kg). Neuromuscular block was monitored with a peripheral nerve stimulator. Intubation was performed after maximum T(1)-depression. To identify awareness, the isolated forearm technique (IFT) was used. The IFT was performed by prompting the patient every 20 seconds. Only a verified response was considered a positive IFT response. Anesthesia was maintained with isoflurane in oxygen/air and fentanyl.


RESULTS
Maximum neuromuscular block occurred after 352 +/- 96 seconds and intubation was performed 424 +/- 86 seconds after loss of consciousness (LOC). Awareness was dose dependent: 80% of patients receiving 0.2 mg/kg etomidate, 70% of patients receiving 0.3 mg/kg etomidate, and 20% of patients receiving 0.4 mg/kg etomidate had a positive IFT response. Awareness occurred in one patient 3 minutes after LOC, in 65% during laryngoscopy, and in 30% within the following 120 seconds. One patient had explicit recall without finding awareness unpleasant. Hemodynamic parameters did not differ between patients with a positive or a negative IFT response.


CONCLUSIONS
The incidence of awareness during bolus induction can be modeled as dose dependent. However, when combining a short-acting induction drug and a delayed-onset neuromuscular blocker, the continuous infusion of the hypnotic drug may prevent awareness during induction.
St Pierre
M
M
Klinik für Anästhesiologie, F.A. Universität Erlangen-Nurnberg, Erlangen, Germany. UM.St_Pierre@01019freenet.de
Landsleitner
B
B
Schwilden
H
H
Schuettler
J
J
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000771:Anesthesia, Intravenous; D018685:Anesthetics, Inhalation / Q000008:administration & dosage; D018686:Anesthetics, Intravenous / Q000008:administration & dosage*; D001279:Atracurium / Q000008:administration & dosage / Q000031:analogs & derivatives*; D001364:Awareness / Q000187:drug effects; D015331:Cohort Studies; D004305:Dose-Response Relationship, Drug; D017558:Elective Surgical Procedures; D005045:Etomidate / Q000008:administration & dosage*; D005260:Female; D005283:Fentanyl / Q000008:administration & dosage*; D005542:Forearm / Q000294:innervation; D006801:Humans; D006993:Hypnotics and Sedatives / Q000008:administration & dosage; D007442:Intubation, Intratracheal; D007530:Isoflurane / Q000008:administration & dosage; D007828:Laryngoscopy; D008297:Male; D008875:Middle Aged; D019148:Neuromuscular Blockade; D009466:Neuromuscular Blocking Agents / Q000008:administration & dosage*; D009469:Neuromuscular Junction / Q000187:drug effects; D011446:Prospective Studies; D013997:Time Factors
D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D006993:Hypnotics and Sedatives; D009466:Neuromuscular Blocking Agents; D001279:Atracurium; D007530:Isoflurane; C101584:cisatracurium; D005283:Fentanyl; D005045:Etomidate