The effects of cognitive function disoders on the requirements of anaesthetic agents and recovery in the elderly

Background and aim: Age-related changes in CNS causes decrease in cognitive function. Cognitive dysfunction commonly manifests itself as the clinical syndromes of dementia, delirium or depression. It has been reported that patients with dementia had lower BIS value in the awake state than control group of similar age. This study was designed to investigate the effects of cognitive dysfunction on the requirement of anesthetic agents and recovery in elderly patients.Materials and Methods: After obtaining approval from ethic comittee and written, informed consent, 62 ASA I-II patients over 65 year of age undergoing elective surgery were enrolled in this study. The MMSE was performed to the patients 24 h before surgery for the evaluation of cognitive function. The patients had MMSE score ? 25 were assigned as group 1, while they had MMS score ? 21 were assigned as group 2. All unpremedicated patients received standard anesthetic technique. Thirty second after the beginning of remifentanil 0.5 mg/kg/min, propofol 0.5 mg/kg was administered. An additional propofol 20 mg bolus was given every 20 s until loss of consciousness. Upon loss of consciousness, a propofol infusion was started at 75 mg / kg/ min. BIS value was kept between 45 and 60 during surgery. After discontinuation of anesthetic agents, the times for tracheal extubation and the eye opening with verbal stimuli were recorded. MAP, HR and BIS values were evaluated before the anesthesia induction (baseline value, T1), after the anesthesia induction (T2), after tracheal intubation (T3), mean value recorded during maintenance of anesthesia (T4), before tracheal extubation (T5) and 5 min after tracheal intubation (T6). The MMSE was repeated in all patients at one and 24 h after surgery.Results: There was no statistically significant difference between groups except body weight for demographic datas. In both groups, MMT score was low 1 h after the surgery while it was significantly high 24 h after the surgery when compared with the baseline value (p< 0.001).BIS score was low in group 2 according to group 1 in all measurement times except the duration period of anesthesia in the assesment between groups (p< 0.05). BIS score was low in all measurement times when compared with baseline value in both group 1 and group 2 (p< 0.001).Although the mean induction dose and infusion rate of propofol was low in group 2, it was not statistically significant.There was no difference in MAP and HR values between the groups. In group 1 and group 2, MAP and HR was low before entubation, after entubation and in the during maintenance of anesthesia when compared with baseline values, while they were not different before and after extubation.The extubation time was not significantly different between the groups, but the eye opening time with verbal stimuli was longer in group 2 than group 1 (p<0.05).Conclusion: BIS value was lower for elder patients in the awake state in the terms of anesthesia induction and recovery from anesthesia when compared with control group. The period of recovery from anesthesia was long because of this reason.But we saw that the decrease in BIS value does not affect the need for anesthetic agent.Key words: Elderly, Cognitive disfunction, Anesthesia in elderly, Mini mental test, BIS, TIVA