A COMPARISON OF INDUCTION ANESTHETIC REGIMENS ETOMIDATE VS MIDAZOLAMFENTANYL COMBINATION IN THE PREVENTION OF AWARENESS DURING GENERAL ANESTHESIA IN CORONARY ARTERY DISEASE PATIENTS POSTED FOR NON CARDIAC SURGERIES.

INTRODUCTION: Anaesthesia, although of great help to mankind, can cause untold misery and suffering if not administered properly. Awareness under general anaesthesia is one of them. Patients who experience awareness and recall during anaesthesia describe auditory perceptions, the sensation of paralysis, anxiety, panic, helpless and powerlessness.The present study is done to study the incidence of awareness under general anaesthesia and to study the effect of induction agents etomidate and midazolam-fentanyl combination in the incidence and prevention of awareness during general anesthesia in cardiac patients posted for non cardiac surgeries under general anaesthesia. METHOD : A clinical study of awareness under general anaesthesia is done at DCMS as prospective, comparative, single blind study which include 100 patients aged between 50 to 75 years undergoing various elective surgical procedures, who were co-operative and could converse intelligently were selected. Except for the surgical condition, they were healthy and were of ASA l ,II and III physical status with history of CAD . They had no history of hearing impairment, difficulty in speaking, psychiatric disorder and history of alcohol or drug dependence. During the preanaesthetic visit all the patients were explained about the study and informed consent was obtained. All the patients were exposed to auditory stimuli like popular music, which was psychologically non-traumatic to the patient, throughout the procedure, using ear phones and a tape recorder. At the end of surgical procedure neuromuscular blockade was antagonised by neostigmine and glycopyrrolate in adequate doses. After reversal of neuromuscular blockade, the lungs were ventilated with oxygen. The patients were asked to open the mouth. If there was no response, laryngoscopy and suction was carried out. The time interval from the time of withdrawal of nitrous oxide till the patient made appropriate response to a verbal request was taken as ‘The time to correct response” (TCR).All the patients were interviewed on the same evening of surgery and also on the post-operative day within 24 hours. The following questions were asked and the reply noted. Awareness under general anaesthesia was taken as the ability of the patient to recall, with or without prompting, any event which occurred between induction of anaesthesia and recovery of consciousness at the end of anaesthesia. Recall of dreams that occurred during anaesthesia was also considered as awareness. In this study, memory recall and ‘time to correct response’ test were taken into consideration, to study the awareness under anaesthesia. RESULT : The prospective, comparative, single blind study include 100 patients undergoing various surgical procedures were administered general anaesthesia and the following observations were made. In Group I none of the patients remembered the intubation. Five patients had dreams (Case No. 6 , 17, 23, 39, 45). Five patients said that they hear songs (Case No. 26, 31, 33, 39, 47) and two of them even remembered the singer (Case No. 31, 39). Two patients remembered somebody talking but could not remember the content (Case No. 37, 45). Five patients remembered the intraoperative events vaguely (Case No. 30, 34, 37, 45, 47) and said that they remembered suturing and pain. In the Group II none of the patients remembered any intraoperative events or auditory input. Four patients reported having had dreams intraoperatively (Case No. 22, 24, 26, 47).Inspite of the dreaming, recalling of music, conversation and some intraoperative events, only two patients of the group-I answered that the anaesthesia was unpleasant (Case No. 34, 47).It can be observed from the study that in few patients of group-I dreams, recalling of music, conversation and intraoperative events and unpleasant experience occurred simultaneously. Regular follow-up of the patients who showed awareness was done and they did not have any adverse psychological sequelae. The mean time in seconds of time to correct response (TCR) in the group I and II patients were 42.5 ± 21.1 and 72.6 ± 31.9 respectively. The difference in the mean time is statistically significant (P<0.05).The mean time in seconds of time to correct response (TCR) in group – I patients who had awareness and who did not have awareness were 35.8 ± 20.0 and 44.4 ± 22.5 respectively. The difference in the mean value within the group is statistically significant (P<0.05) by t-test. The mean time in seconds of time to correct response (TCR) in group – II patients who had awareness and who did not have awareness were 67.8 ± 7.6 and 72.9 ± 33.13 respectively. The difference in the mean value within the Group II, is statistically significant (P<0.05) by t-test. CONCLUSION: From the above study its concluded awareness under anaesthesia is a common problem of nitrous oxide, oxygen and muscle relaxant technique of anaesthesia. The incidence of awareness under general anaesthesia was less in Group-II patients who received fentanyl - midazolam as induction. There was a significantly higher incidence of awareness under anaesthesia in the patients with etomidate induction. In the patients who had awareness under general anaesthesia the time to correct response (TCR) was significantly lesser than those who did not have awareness. Thus TCR test is a simple, valuable and reliable test in assessing awareness under GA. Hence, it is recommended to induce with midazolam-fentanyl, routinely as induction in cardiac patients to decrease the incidence of awareness.