Double burst stimulation for monitoring neuromuscular blockade for tracheal intubation

Abstract

Summary Responses 66%). Palpation of evoked response to double burst stimulation can be used to predict intubating conditions and neuromuscular response to tracheal intubation with nondepolarising muscle relaxants such as vecuronium. Key wordsMonitoring; neuromuscular, double burst stimuli. Neuromuscular relaxants; vecuronium. Intubation; tracheal. Double burst stimulation (DBS) is a newly introduced pattern of nerve stimulation for neuromuscular monitoring [I]. Essentially, two short bursts of three stimuli each at 50 Hz separated by an interval of 750 ms comprise the DBS pattern. The responses to the two bursts of stimulation are palpated as two discrete contractions. Palpable fade between the two responses indicates significant residual paralysis during recovery from nondepolarising neuromuscular block [I, 21. This study assesses the usefulness of palpation of responses to DBS for deciding the appropriate time to attempt tracheal intubation with vecuronium. Material and methodsSixty adult patients. ASA grade I or I1 undergoing routine surgical procedures and requiring muscle relaxation, were included in this study. Patients with any type of neuromuscular disorder or taking drugs likely to alter neuromuscular function were not studied. The protocol was approved by the hospital ethics committee and informed consent was obtained. All patients were premedicated with diazepam 10 mg orally 2 h before surgery. On the operation table an intravenous infusion line was set up in one forearm and the other forearm was used for neuromuscular monitoring with a DBS 3,3 stimulator connected to skin surface electrodes placed over the ulnar nerve at the wrist. Other parameters monitored intra-operatively were continuous ECG, heart rate, blood pressure (every 5 min), temperature, Spo, and end-tidal carbon dioxide.Morphine 0.15 mg.kg-' was administered intravenously 5 to 10 min before induction of anaesthesia with thiopentone 4-5 mg.kg-I . Vecuronium 0.2 mg.kg-' was used to facilitate tracheal intubation. The patients' lungs were ventilated with halothane 0.5 to 1 YO in oxygen using a face mask with a Magill breathing system. Responses to DBS 3,3 stimulations were palpated every 15 s by an observer with about 3 years experience in clinical neuromuscular monitoring. He was blinded to the dose of relaxant used. The observer palpating the responses was required to indicate the number of palpable responses each time to the anaesthesiologist who was to perform tracheal intubation. The latter also recorded the intubating conditions and