BJA Advance Access originally published online on November 19, 2008
British Journal of Anaesthesia 2009 102(1):61-64; doi:10.1093/bja/aen327
Effect of propofol on twitch diaphragmatic pressure evoked by cervical magnetic stimulation in patients
1 Department of Anaesthesiology
2 Guangzhou Institute of Respiratory Disease, First Affiliated Hospital of Guangzhou Medical College, No. 151 Yanjiangxi Road, Guangzhou 510120, China
* Corresponding author. E-mail: yu2ge3{at}yahoo.com.cn
Background: Several studies have demonstrated the inhibitory effect of propofol on diaphragmatic contractility in laboratory animals, but there have been few studies in humans. We have investigated the effect of a single bolus injection of propofol on twitch diaphragmatic pressure (TwPdi) evoked by cervical supramaximal magnetic stimulation, and its impact on diaphragmatic contractility.
Methods: In 16 patients scheduled for elective operation, TwPdi was evoked bilaterally at the cervical phrenic nerves with supramaximal magnetic stimulations using a 140 mm diameter magnetic coil. Changes of TwPdi were monitored dynamically before and during general anaesthesia induced by single bolus of propofol 2 mg kg –1. During the study, all patients breathed 100% oxygen by a face mask, maintaining SpO2
99% and PE'CO2 4.6–5.2 kPa.
Results: TwPdi declined after administration of propofol with gradual recovery. Compared with baseline [20.6 (6.0) cm H2O], TwPdi decreased by 23.3% (P<0.001) to [15.8 (6.4) cm H2O]. When the patients regained awareness, TwPdi returned to [19.1 (6.1) cm H2O], close to baseline (P=0.063). The time from starting the propofol infusion to the lowest TwPdi was [240 (86) s]. Total time course of stimulation lasted [363 (89) s].
Conclusions: A single bolus propofol depressed TwPdi evoked by cervical magnetic stimulation, demonstrating inhibitory effects of propofol on diaphragmatic contractility in patients during general anaesthesia.
Keywords: anaesthetic techniques, i.v. bolus; anaesthetics i.v., propofol; monitoring, neuromuscular function; muscle skeletal, diaphragm
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