The effect of low-dose ketamine infusion on the remifentanil induced hemodynamic changes during general anesthesia

Beigmohamadi, M.T and Khan, Z.H and Mahoori, A.R (2008) The effect of low-dose ketamine infusion on the remifentanil induced hemodynamic changes during general anesthesia. Tehran University Medical Journal, 65 (11). pp. 44-48.

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Abstract

Remifentanil is known to produce side-effects of hypotension and bradycardia. In this study, we examine the effect of low-do se ketamine infusion on the heart rate and blood pressure of patie nts anesthetized with remifentanil. Methods: In a randomized clinical trial, 54 patients aged 20-50 years old, with ASA physical status Ι , were studied in two groups (n= 27 ), Ketamine- Remifentanil ( K-R group) and Placebo- Remifentanil ( P-R group). Exclusion criteria were ASA physical status >1 , gastroesophageal reflux, t achycardia, bradycardia, sy stemic diseases, use of antihypertensive drugs, difficult intubations, risk of aspiration and contraindications of ketamine. Remifentanil was started at a rate of 0.5 μg. kg -1 . min -1 and anesthesia was induced with thiopental sodium 2 mg.kg -1 . Maintenance of anesthesia included halothane and nitrous oxide/oxygen mixture. Remifentanil infusion was continued in both groups at a rate of 0.5 μg.kg -1 .min -1 . In the K-R group, ketamine was started with an infusion rate of 10 μg.kg -1 . min -1 , 10 minutes after intubation, while in the P-R group, normal saline was started with the same dose of remifentanil. Heart rate, systolic, diastolic and mean arterial blood pressure were measured and compared at 1 , 3 , 5 , 10 , 15 , 20 , 25 and 30 minutes. Results: No significant differences were found be tween basic patient characteristics of mean of age, sex, weight, systolic, diastoli c and mean arterial blood pressure and heart rate (p >0.2 ) in the two groups. However, the rate of systolic, diastolic and mean arterial blood pressure changes in the P-R group was significantly greater than that of the K-R group (p <0.006 ). Heart rate changes were sim ilar between the two groups (p= 0.6 ). Incident of severe hypotension (a decrease of more than 25% of the basic value) was less in the K-R group than that of the P-R group ( 11% vs. 89% ; p= 0.000 ). Conclusion: Low-dose ketamine infusion modulates the effect of remifentanil-induced hypotension and provides better hemodynamic stability during general anesthesia.

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