Sevoflurane vs isoflurane anaesthesia: a study of postoperative mental concentration and fine motor movements

Ambulatory anaesthesia is a challenging specialty. Often locoregional techniques are preferred due to the speedy recovery and short hospital stay. However a reasonable number of day-case surgery are performed under general anaesthesia where the recovery of cognitive functions are delayed. Therefore we conducted this study in order to assess the postoperative mental concentration and fine motor movements following isoflurane versus sevoflurane anaesthesia. Twenty adult patients were enrolled in the study. They were ASA 1, age 33 +/- 10 yr and weight 68 +/- 7 kg. They were divided into two groups A and B for isoflurane and sevoflurane respectively. After routine monitoring, induction for both groups was achieved with propofol, endotracheal intubation was facilitated with atracurium and maintenance with either isoflurane or sevoflurane 1 MAC with 50% nitrous oxide in oxygen. During the recovery period the cognitive functions were assessed using the tracing test equipment where the time error product (TEP) was used as a test score. In both groups 30 min after anaesthesia the TEP was 10,000 sec. Thirty minutes later the median TEP was 6,316 sec and 10,000 sec in groups A and B respectively. Another thirty minutes later, the TEP median was 4,052 sec and 1,209 sec for groups A and B respectively. Five hours after anaesthesia the TEP in both groups became identical but still significantly higher compared with the preoperative values. In the present study the TEP was reduced in the sevoflurane group 2 hr after anaesthesia from 10,000 sec to nearly 1,000 sec where in the isoflurane group it was reduced from 10,000 sec to 4,000 sec. In conclusion, sevoflurane anaesthesia resulted in superior recovery of the early TEP scores compared to isoflurane but in both groups the late TEP scores were identical. We believe that following general anaesthesia in day-case set up the patients should refrain from any kind of work that necessitates fine motor movement and mental concentration for at least 24 hr postoperatively.