Comparison of the trapezius and the adductor pollicis muscle as predictor of good intubating conditions: a randomized controlled trial

Abstract

Background: Adequate muscle relaxation is important for ensuring optimal conditions for intubation. Although acceleromyography of the adductor pollicis muscle is commonly used to assess conditions for intubation, we hypothesized that acceleromyography of the trapezius is more indicative of optimal intubating conditions. The primary outcome was the difference between both measurement sites with regard to prediction of good or acceptable intubating conditions.

Methods: Neuromuscular blockade after injection of rocuronium 0.3 mg/kg IV was measured simultaneously with acceleromyography of the adductor pollicis muscle and the trapezius muscle in sixty female patients, American Society of Anesthesiologists physical status I to III, undergoing general anesthesia for gynecologic surgery. Exclusion criteria were: expected difficult tracheal intubation (e.g. history of difficult intubation, reduced mouth opening (< 2 cm) and/or Mallampati Score 4), increased risk of pulmonary aspiration (e.g. gastroesophageal reflux or delayed gastric emptying) allergies to drugs used during the study, pregnancy, neuromuscular diseases, medication with potential to influence neuromuscular function (e.g. furosemide, magnesium, cephalosporins) and hepatic or renal insufficiency (serum bilirubin >26 μmol/L, serum creatinine >90 μmol/l). Patients were randomized to 2 groups: group A (n = 30): endotracheal intubation after onset of the neuromuscular block at the adductor pollicis muscle. Group B (n = 30): endotracheal intubation after onset at the trapezius muscle. Intubating conditions were compared between both groups by means of a standardised score (the Copenhagen score) with Fisher's exact test.

Results: Onset of the block after rocuronium injection was observed at the adductor pollicis muscle compared to the trapezius with 2.8 (1.1) versus 2.5 (1.1) min (mean ± SD; P = 0.006). Intubating conditions were poor in 2 patients (7%) of group A, and in 1 patient (3%) of group T. They were acceptable (either excellent or good) in 28 patients (93%) in group A, and in 1 patient (97%) in group T (P = 0.82).

Conclusions: Performing acceleromyography at the trapezius muscle reduced the time between injection of neuromuscular blocking agents and intubation by 18 s (11%). Thus, trapezius muscle acceleromyography is an acceptable alternative to adductor pollicis muscle acceleromyography in predicting acceptable intubating conditions, which allows for earlier indication of adequate intubating conditions.

Trial registration: ClinicalTrial.gov Identifier: NCT01849198 . Registered April 29, 2013.

Keywords: Intubating conditions; Neuromuscular block; Trapezius muscle.

Conflict of interest statement

Ethics approval and consent to participate

The study was approved by the local ethics committee (Ethikkommission der Ärztekammer Nordrhein, Düsseldorf, Germany, April 23th, 2013; No 2013056). Written informed consent to participate was obtained from all patients.

Consent for publication

Not applicable

Competing interests

The authors declare that they have no competing interests.

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Figures

Fig. 1

Position of the electrodes at the accessory nerve and the piezoelectric element (white arrow) on the trapezius muscle. Blue lines: sternocleidomastoid muscle. Red line: anterior border of the trapezius muscle. Yellow lines: accessory nerve

Fig. 2

Measurement of onset time in case of an incomplete neuromuscular block (defined as T1 height did not fall

Fig. 3

Flow chart of patient selection. Group A: measurement of intubating conditions when onset time was reached at the aductor pollicis muscle. Group T: measurement when onset was reached at the trapezius muscle