[Neuromuscular monitoring during anesthesia.]

Muscle relaxants are very important in anesthetic practice but must be used with great care. Studies have shown that 17-40% of patients in postanesthesia care units (PACU) have residual muscle weakness. The purpose of this study was to evaluate whether the use of neuromuscular monitors during anesthesia could reduce the incidence of muscle weakness in the postoperative period.

Eighty patients operated for laparoscopic cholecystectomy or lumbal disc prolapse given muscle relaxants during anesthesia were studied, randomly allocated to four groups. Fourty of these patients were monitored with neuromuscular monitor (TOF-guard") during anesthesia and the set point was a TOF-ratio of at least 70% before extubating the patients. Fourty patients were monitored by usual clinical signs (spontaneus breathing, cough and muscle movement). Twenty patients in each group were given vecuronium as muscle relaxant and 20 patients recieved pancuronium, again patients were randomly selected. In the PACU all patients were evaluated and the "5-sec headlift test" was used to find patients with muscle weakness. Hand grip strength was also measured before anesthesia and in the PACU. Glascow Coma Score (GCS) was used to evaluate if patients were too drowsy to co-operate and patients with GCS < 12 were excluded. Measurements were made after arrival to the PACU and every 30 minutes thereafter until headlift was at least 5 sec.

The incidence of restcurarization was 15% on arrival to the PACU. No statistically significant difference was found between those monitored with neuromuscular monitors and those that were not. Similarily no statistical difference was found between short acting neuromuscular blocking agents and longer acting agents.

Although we didn t find any benefit from neuromuscular monitoring or using shorter acting drugs, the use of nervestimulators and short acting drugs is still recommended, especially for high risk patients. The generally accepted train-of-four (TOF-) ratio of 70% has been questioned by some authors, recommending a higher ratio (85%). Further studies using a higher TOF-ratio are therefore recommended.