Moderate hypothermia and its effects in reducing the applied dose of anesthetics for patients with opium dependence in cardiac surgery: A randomized controlled trial

BACKGROUND: An increasing number of patients addicted to opium are experiencing awareness during coronary artery bypass surgery (CABG) as a result of tolerance to anesthetics. OBJECTIVES: This research was primarily intended to determine the potential diminishing effects of moderate hypothermia on anesthetic dosage and recall of anesthesia during the procedure. METHODS: In this double-blind randomized controlled trial, a total of 80 CABG candidates with known addiction to opium were divided into two groups: one normothermic (N) and the other moderately hypothermic (H), both undergoing induction as well as close monitoring from September 2014 to January 2016. The candidates were initially set for a target bispectral index (BIS) score of between 40 and 60. As the score rose to 60, an additional dose of propofol was administered, alongside rise in blood pressure and tear-shedding. To enhance the accuracy of our evaluation of anesthetic depth, we also used two questionnaires to test candidates’ recall filled with the assistance of a colleague 24 hours following surgery. Independent-samples t-test and chi-square test were used by SPSS v 18 for data analysis. RESULTS: Eighty patients were studied in two groups of normothermic (N) (n = 40) and hypothermic (H) (n = 40). Given similar demographic data as well as the duration of surgery, we arrived at a propofol dose of 122.52±13.11 cc for normothermic patients and 101.28±14.06 cc for hypothermic subjects (p=0.001). As for fentanyl, the total required sum came up to 39.60±21.04 cc and 31.72±5.81 cc for the above-mentioned groups in order (p=0.025). Moreover, the post-operative interview showed that there was no report of a patient with memory recall following surgery. CONCLUSIONS: Moderate hypothermia can substantially reduce the need for anesthetics in patients with addiction to opium when undergoing CABG surgery. TRIAL REGISTRATION: This study is registered in Iranian Registry of Clinical Trials with registration number of IRCT2014050513159N5. FUNDING: This research was supported financially by the Research Council of Mashhad University of Medical Sciences (grant number 920405).