Tehran University Medical Journal

Background: Remifentanil is known to produce side-effects of hypotension and bradycardia. In this study, we examine the effect of low-dose ketamine infusion on the heart rate and blood pressure of patients 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, tachycardia, bradycardia, systemic 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 between basic patient characteristics of mean of age, sex, weight, systolic, diastolic 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 similar 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.

Background: Axillary block is used for inducing anesthesia in outpatient hand and forearm surgeries. Few researches have studied hemodynamic and blockade effects of low doses of Epinephrine. The aim of the present study was to compare the duration of analgesia and hemodynamic changes following the injection of high/low epinephrine doses in such surgeries.

Methods: The present randomized clinical trial study was conducted on healthy individuals (ASA I-II) who were candidates for hand and forearm surgeries. The patients were randomly divided into three groups. The first two groups were allocated to receive lidocaine with low (0.6µg/cc) and high (5µg/cc) doses of epinephrine whereas lidocaine plus normal saline was injected in the third group. The hemodynamic changes (Mean arterial blood pressure and heart rate) and the occurance of any side-effects along with the duration of analgesia and motor block were recorded.

Results: From among the total of 75 patients, 15 cases were excluded due to incomplete blockade or failure needing general anesthesia. The duration of analgesia and the motor block were longer in the high dose epinephrine group, the difference, however, was not statistically significant. Heart rate changes within the groups was significant in the 4^th-7^th and 10^th minutes. Mean arterial blood pressure changes was only significant in the 4^th minute, within the groups.

Conclusions: Administering low doses of epinephrine plus lidocaine as a local anesthetic not only provides acceptable analgesia compared to higher doses of the medication, but also is associated with fewer side effects.