1Department of Anaesthesia, Hakujikai Memorial Hospital, 5-11-1 Shikahama, Adachi-ku, Tokyo 123-0864, Japan. 2Department of Anaesthesia, Chiba Hokusoh Hospital, Nippon Medical School, Chiba, Japan. 3Department of Anaesthesiology, Tokyo Jikeikai Medical School, Tokyo, Japan. 4Department of Anaesthesiology, Nippon Medical School, Tokyo, Japan*Corresponding author
This work was carried out at Chiba Hokusoh Hospital, Nippon Medical School, 1715 Kamakasi Inba-mura, Inba-gun, Chiba 2701694, Japan.
Accepted for publication: January 29, 2001
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Abstract |
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Br J Anaesth 2001; 86: 8746
Keywords: sympathetic nervous system, clonidine; anaesthetics i.v., propofol
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Introduction |
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Methods and results |
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An 18-gauge Teflon cannula (Insyte-W Vialon E; Becton Dickinson, Franklin Lakes, NJ, USA) was inserted into the cephalic vein of the non-dominant hand, without infiltration of local anaesthetic, about 180 min before the induction of anaesthesia when the patient was still in the ward on the day of surgery. The cannula was used for i.v. infusion of Ringers lactate solution.
Non-invasive systolic arterial blood pressure (ni-SBP), non-invasive diastolic arterial blood pressure (ni-DBP) and heart rate were recorded in the ward about 120 min before transferring the patient to the operating theatre and before administration of oral clonidine or placebo. Measurements were repeated in the operating theatre before induction of anaesthesia.
Patients in the clonidine group (n=41) were given powdered clonidine 5.5 µg kg1 orally 120 min before induction of anaesthesia. Propofol 2.5 mg kg1 was given into the cannula at induction of anaesthesia. Control patients (n=40) were given placebo (cornstarch 5.5 µg kg1) orally 120 min before induction of anaesthesia. Propofol was then administered as described for the clonidine group.
Propofol was kept in an incubator at 2023°C until immediately before administration. It was infused through a three-way tap directly connected to the i.v. cannula, with the i.v. infusion line closed, using an electrically powered syringe pump (Graseby Anaesthesia Pump 3500; Graseby Medical, Hertfordshire, UK). The infusion rate was 3 mg kg1 min1 and the total amount infused was 2.5 mg kg1. Before administration of propofol, the patient was requested to rate immediately any sensation of pain during injection as either none (0), mild (1), moderate (2) or severe (3), similar to the method used in previous studies.1 2 3 A blinded anaesthetist recorded the reported degree of pain. The maximum degree of pain reported before the patient fell asleep was recorded as the pain score (pain score) for that patient. We also recorded the interval before pain was experienced. If there was no pain, this interval was recorded as 50 s, representing the total time required for injecting the propofol.
After induction of anaesthesia, the lungs were ventilated mechanically with 3050% oxygen in air through an endotracheal tube, in combination with epidural anaesthesia and continuous i.v. propofol.
Power calculation indicated that recruitment of 40 patients in each group would be sufficient to demonstrate a reduction of pain score of 1 at a level of significance of P=0.05 and power of 99.3%. Statistical analysis was carried out using SPSS version 10.0 and SamplePower J version 1.0 (SPSS, Chicago, IL, USA), on a Toshiba DynaBook Satellite 2520 computer running the Microsoft J Windows 98 operating system.
Differences in continuous variables between groups were statistically evaluated with the unpaired t-test, ASA status with the 2 test and pain score with the MannWhitney U-test. The relationship between pain score and time to pain was analysed with Spearmans rank correction coefficient, excluding patients with a pain score of 0 because there were no patients with a pain score of 0 in the control group. A P value of <0.05 was regarded as significant.
There were no significant differences in patient characteristics between the control and clonidine groups. Median pain score in the clonidine group was 1 (02), significantly lower than the score of 2 (13) in control patients (P<0.001) (Table 1).
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Comments |
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Previous studies have demonstrated that oral clonidine administered before anaesthesia increases the analgesic effects of opioids after operation5 6 and reduces anaesthetic7 and/or opioid requirement8 9 during the peri-operative period, and that clonidine attenuates the haemodynamic responses to noxious stimuli such as tracheal intubation.8 10 Because of these beneficial properties, clonidine is a useful premedication. Our results demonstrate the efficacy of oral clonidine for pain on injection of propofol.
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Acknowledgements |
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References |
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