COMPARISON OF ISOFLURANE-PROPOFOL & ISOFLURANE-THIOPENTAL EFFECTS ON PLASMA NOREPINEPHRINE LEVEL FOLLOWING PAINFUL STIMULUS AT EQUAL ANESTHESIA DEPTH

Responses to painful stimulus are associated with broad spectrum of physiological changes in human body. One of these significant responses is an increase in plasma norepinephrine level that may cause pathophysiological changes in the body. The present study attempted to investigate plasma norepinephrine level changes by inducing appropriate anesthesia depth under BIS monitoring and using different drugs for induction and maintenance of anesthesia. Thus, thiopental and propofol were used for induction and isoflurane as maintenance drug, then norepinephrine level was measured following painful stimulus. Sixty ASA I patients candidated for elective ACL repair surgery, in the range of 15-45 years old, were randomly allocated into two groups. BIS monitoring was performed to measure depth of anesthesia. For all of the patients, midazolam was administered to reach BIS 70. Then blood sampling was done to measure basal norepinephrine level. Thiopental in group I and propofol in groups II were administered to reach BIS 40. Then 3 mcg/dl fentanyl as analgesic and 0.5mg/kg atracurium to facilitate intubation were injected. Endotracheal intubation was done in at most 15 seconds and patients who had difficult or prolonged intubation were excluded. Three minutes after intubation, blood sampling was done to measure norepinephrine level. Isoflurane at dose 1.2% was administered to maintain anesthesia. After stabilizing anesthesia depth(BIS=40), skin incision was allowed to repair ACL and after 3 minutes blood sampling was done to determine plasma norepinephrine level. By using ELISA method, plasma norepinephrine level was measured after laryngoscopy and Isoflurane administration and skin incision. Data showed that basal norepinephrine level in propofol group was 0.245±0.113mcg/dl(mean±SD), in thiopental group was 0.210±0.105mcg/dl(Pvalue=0.225). Norepinephrine level after laryngoscopy in propofol group was 0.236±0.125mcg/dl and in thiopental group was 0.216±0.118mcg/dl(Pvalue=0.534). Norepinephrine level after skin incision and isoflurane administration in propofol group was 0.229±0.102mcg/dl and in thiopental group was 0.223±0.128mcg/dl(Pvalue=0.716). It was concluded that norepinephrine level changes did not have significant difference in propofol and thiopental and isoflurane groups.