1 Division of Anaesthesiology, Department of Anaesthesiology, Pharmacology and Surgical Intensive Care, Geneva University Hospitals, Geneva, Switzerland. 2 University Clinic, Balgrist Hospital, Zürich, Switzerland
Corresponding author: Pediatric Anaesthesia, Hôpital des Enfants, Geneva University Hospitals, Rue Willy Donze 6, CH-1205 Genève 4, Switzerland. E-mail: michel.pellegrini@hcuge.ch
Accepted for publication: October 21, 2002
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Abstract |
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Methods. One hundred and eight children received propofol 1% (n=55) or 2% (n=53) for induction and maintenance of anaesthesia. For induction, propofol 4 mg kg1 was injected at a constant rate (1200 ml h1), supplemented with alfentanil. Intubating conditions without the use of a neuromuscular blocking agent were scored.
Results. Pain on injection occurred in 9% and 21% of patients after propofol 1% and 2%, respectively (P=0.09). Loss of consciousness was more rapid with propofol 2% compared with propofol 1% (47 s vs 54 s; P=0.02). Spontaneous movements during induction occurred in 22% and 34% (P=0.18), and intubating conditions were satisfactory in 87% and 96% (P=0.19) of children receiving propofol 1% or 2%, respectively. There were no differences between the two groups in respect of haemodynamic changes or adverse events.
Conclusions. For the end-points tested, propofol 1% and propofol 2% are similar for induction of anaesthesia in children undergoing minor ENT surgery.
Br J Anaesth 2003: 90: 3757
Keywords: anaesthetic techniques, induction; anaesthetics i.v., propofol; children; pain, injection
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Introduction |
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Methods and results |
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Propofol was given on a mg kg1 h1 basis by an infusion pump (Medfusion® 2010i, USA) in an absolutely blinded manner, so that the anaesthetist was not aware of the propofol concentration.
After 3 min preoxygenation, alfentanil 20 µg kg1 was administered i.v. Before the propofol, lidocaine 0.5%, 1 ml was injected i.v. without a tourniquet. An i.v. bolus of propofol 4 mg kg1 was then administered by the Medfusion® pump at a constant rate of 1200 ml h1. Tracheal intubation was performed 1 min after the end of the bolus, without the use of any neuromuscular blocking agent. Anaesthesia was maintained by propofol given at a preprogrammed infusion rate of 12 mg kg1 h1, reduced to 9 mg kg1 h1 during surgery, and to 6 mg kg1 h1 when awaiting haemostasis. The childrens lungs were ventilated with 60% nitrous oxide/oxygen throughout the procedure.
Pain on injection was considered present when the child complained about it or when they withdrew their hand during the injection. Abnormal movements were defined as purposeless movements of any part of the body during or immediately after the injection of propofol.2 The anaesthesia induction sequence was video recorded for subsequent analysis by one of the authors who was not involved in the administration of the anaesthetic (AB). Unconsciousness was defined as the absence of a reaction to verbal stimulation (OAAS score <2). The quality of intubation was evaluated according to a validated and widely used score3 4 (1=excellent, 2=good, 3=unsatisfactory, 4=bad). Side-effects and time of recovery (from the end of propofol infusion to extubation) were recorded.
The two sets of data were analysed using the 2-test and relative risks with 95% confidence intervals. An unpaired t-test with P<0.05 or a 95% confidence interval excluding 1 was considered significant.
Nine children in the propofol 1% group and eight children in the propofol 2% group were excluded because of agitation, failure to obtain venous access or technical problems. Five children had laryngospasm after the injection of propofol (Table 1). These patients were intubated with succinylcholine and removed from further study.
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There were no significant differences between the two groups for all primary end-points except that loss of consciousness was more rapid with propofol 2% compared with the 1% emulsion (47 s vs 54 s respectively; P=0.02).
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Comment |
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A potential advantage of propofol 2% might have been a lower incidence of pain on injection, but this was not detected in this study (Table 1). However, the present study has shown a lower incidence of pain than that previously reported.1 A larger number of children would need to have been studied to demonstrate any significant difference between propofol 1% and 2% in this respect. This lower incidence of propofol-related pain may be attributable in part to the administration of alfentanil before lidocaine and propofol. It has been shown that opioids decrease propofol-related pain. Furthermore, although it has been questioned,6 the speed of injection may have influenced the results in the present study5 as propofol was injected at a constant, albeit much slower, rate than that used clinically for administration from a syringe. In order to compare the concentration effects rather than the speed of injection, propofol was administered during maintenance of anaesthesia at a comparable rate in both groups in terms of mg kg1 h1. Finally, the incidence of spontaneous movements following injection of either propofol 1% or 2% was similar to that described in the literature.2 Although it has been suggested that these movements are of a subcortical rather than a cortical nature,2 their cause remains unclear.
In conclusion, the present study shows that induction of anaesthesia in children with propofol 1% or 2% provided comparable clinical conditions. The difference observed in the time to loss of consciousness was probably related to the higher concentration of propofol 2% used in one group as a single bolus for induction of anaesthesia.
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References |
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2 Borgeat A, Dessibourg C, Popovic V, et al. Propofol and spontaneous movements: an EEG study. Anesthesiology 1991; 74: 247[ISI][Medline]
3 Borgeat A, Fuchs T, Tassonyi E. Induction characteristics of 2% propofol in children. Br J Anaesth 1997; 78: 4335
4 Fuchs-Buder T, Tassonyi E. Intubating conditions and time course of rocuronium-induced neuromuscular block in children. Br J Anaesth 1996; 77: 3358
5 Scott RP, Saunders DA, Norman J. Propofol: clinical strategies for preventing the pain of injection. Anaesthesia 1988; 43: 4924[ISI][Medline]
6 Grauers A, Liljeroth E, Akeson J. Propofol infusion rate does not affect local pain on injection. Acta Anaesthesiol Scand 2002; 46: 3613[CrossRef][ISI][Medline]