Department of Anaesthesiology and Reanimation, SSK Okmeydani Training Hospital, Istanbul, Turkey
* Corresponding author: Ortaklar Cad. Mevlut Pehlivan Sok. Ali Balaban Apt. No:10/3 Mecidiyekoy, Istanbul, Turkey. E-mail: neturgut{at}ttnet.net.tr
Accepted for publication November 11, 2004.
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Abstract |
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Methods. Sixty ASA III patients undergoing spinal surgery were randomized into three groups. Group M received magnesium sulphate 30 mg kg1 as a bolus before induction and 10 mg kg1 h1 by infusion. Group CL received clonidine 3 µg kg1 as a bolus before induction and 2 µg kg1 h1 by infusion during the operation period. The same volume of isotonic solution was administered to the control group (group CT). Anaesthesia was induced with propofol and was maintained with propofol infusion [dose according to the bispectral index (BIS)], fentanyl and cisatracurium. Analysis of variance and the Bonferroni test were used for statistical analysis.
Results. Induction of anaesthesia with propofol was rapid in the presence of magnesium sulphate and clonidine. The time for BIS to reach 60 was significantly shorter in group M and group CL (P<0.0001) but postoperative recovery was slower with magnesium sulphate compared with the clonidine and control groups (P<0.0001). There was no statistical difference in heart rate and arterial blood pressure between the groups. Propofol requirements for induction and maintenance of anaesthesia were significantly lower with magnesium and clonidine (P<0.0001).
Conclusion. Clonidine caused bradycardia and hypotension and magnesium sulphate caused delayed recovery, but can be used as adjuvant agents with careful management.
Keywords: anaesthetics i.v., propofol ; pharmacology, magnesium sulphate ; premedication, clonidine
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Introduction |
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Parenteral magnesium sulphate administration has been used for many years on an empirical basis as an antiarrhythmic agent and for prophylaxis against seizures in pre-eclampsia. This placebo-controlled, double-blind study was designed to assess the effects of i.v. magnesium sulphate and i.v. clonidine on peroperative haemodynamics, propofol consumption and postoperative recovery when used as adjuvant agents.
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Methods |
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All patients were also evaluated with the Aldrete postanaesthesia recovery scoring system.2
Statistical analysis was with analysis of variance and the Bonferroni test. The analysis was conducted on an intention-to-treat basis. A value of P<0.05 was considered significant.
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Results |
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Discussion |
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Magnesium sulphate has been reported to produce general anaesthesia and enhance the activity of local anaesthetic agents. In these studies, depressant effects on the CNS of animals injected with magnesium sulphate salts were reported. However, Aldrete and Vazeery7 suggested that this was actually a sleep-like state caused by cerebral hypoxia from progressive respiratory and cardiac depression. When ventilation was maintained, even very high levels of serum magnesium sulphate produced no CNS depression. However, increasing the magnesium sulphate dose was found to be associated with a reduction in halothane MAC in rats.8 Magnesium sulphate antagonizes NMDA receptors in the CNS and may reduce catecholamine release, thus decreasing peripheral nociceptor sensitization or the stress response to surgery. In our study, fentanyl requirements were lower in the magnesium sulphate group. Van Den Berg and colleagues found that magnesium sulphate attenuated the haemodynamic response to tracheal intubation.9 In our study, both magnesium sulphate and clonidine lowered the haemodynamic response to intubation but clonidine was more effective in attenuating the sympathetic response.
Taittoven and colleagues compared clonidine and midazolam as premedication agents and observed no difference in oxygen consumption, anxiolysis, energy expenditure and carbon dioxide production.10 Preoperative oral clonidine protects against the pressor response to intubation.11 Hypotension and bradycardia may be encountered with clonidine,1 12 and in our study we found more bradycardia and hypotension in the clonidine group than in the other groups. Clonidine has been shown to decrease propofol requirements during anaesthesia13 and our study confirms this. Preoperative administration of clonidine, in addition to careful anaesthetic management, results in improved perioperative haemodynamic stability in patients with mild or moderate arterial hypertension and a reduction of the anaesthetic requirement,14 but further studies are necessary to investigate whether this approach may be safely extended to hypertensive patients.
In conclusion, both clonidine and magnesium sulphate lowered propofol consumption and attenuated the haemodynamic response to tracheal intubation. Clonidine was associated with bradycardia and hypotension and magnesium sulphate caused a delay in recovery.
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References |
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2 Aldrete JA, Kroulik D. A post anesthetic recovery score. Anesth Analg 1970; 49: 92434[Medline]
3 Gan TJ, Glass PS, Windsor A, et al. Bispectral index monitoring allows faster emergence and improved recovery from propofol, alfentanil, and nitrous oxide anesthesia. Anesthesiology 1997; 87: 80815[CrossRef][ISI][Medline]
4 Cullen PM, Turtle M, Pyrs-Roberts C, Way WL, Dye J. Effects of propofol anesthesia on baroreflex activity in humans. Anesth Analg 1987; 66: 111520[Abstract]
5 Coates DP, Monk CR, Prys-Roberts C, Turtle M. Hemodynamic effects of infusions of the emulsion formulation of propofol during nitrous oxide anesthesia in humans. Anesth Analg 1987; 66: 6470[Abstract]
6 Telci L, Esen F, Akcora D, et al. Evaluation of effects of magnesium sulphate in reducing intraoperative anaesthetic requirements. Eur J Anaesth 2001; 18: 7239[CrossRef][ISI][Medline]
7 Aldrete JA, Vazeery A. Is magnesium sulfate an anesthetic? Anesth Analg 1989; 68: 1867
8 Thompson SW, Moscicki JC, Difazio CA. The anesthetic contribution of magnesium sulfate and ritodrine hydrochloride in rats. Anesth Analg 1988; 67: 314[Abstract]
9 Van Den Berg AA, Savva D, Honjol NM. Attenuation of the hemodynamic responses to noxious stimuli in patients undergoing cataract surgery. A comparison of magnesium sulphate, esmolol, lignocaine, nitroglycerine and placebo given i.v. with induction of anaesthesia. Eur J Anaesth 1997; 14: 13447[CrossRef][ISI][Medline]
10 Taittonen M, Kirvela O, Aantaa R, Kanto J. Cardiovascular and metabolic responses to clonidine and midazolam premedication. Eur J Anaesth 1997; 14: 1906[CrossRef][ISI][Medline]
11 Costello TG, Cormack JR. Clonidine premedication decreases hemodynamic responses to pin head-holder application during craniotomy. Anesth Analg 1998; 86: 10014[Abstract]
12 Kulka PJ, Tryba M, Zenz M. Does clonidine modify the hypnotic effect of propofol? Anaesthetist 1993; 42: 6307[ISI][Medline]
13 Fehr SB, Zalunardo MP, Seifert B, et al. Clonidine decreases propofol requirements during anaesthesia: effect on bispectral index. Br J Anaesth 2001; 86: 62732
14 Ghignone M, Calvillo O, Quintin L. Anesthesia and hypertension: the effect of clonidine on perioperative, hemodynamics and isoflurane requirements. Anesthesiology 1987; 67: 310[ISI][Medline]
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