Dynamometer based hand grip strength as a clinical tool for objective assessment of post-operative residual muscle weakness

BACKGROUND AND AIMS: Residual neuromuscular block continues to be a significant postoperative complication despite neuromuscular monitoring. This study aims to determine the applicability of a hand-held forced dynamometer for hand grip strength assessment as an objective measure of residual muscle weakness. METHODS: The study included patients undergoing surgery under general anaesthesia. A demonstration was given to the patient on the usage of a dynamometer for handgrip strength and a peak expiratory flow meter for peak expiratory flow rate (PEFR) and baseline values were recorded. The parameters were monitored at 15 minutes post-extubation and again at intervals of 15 minutes until one hour, half-hourly until four hours, and hourly until six hours post-operatively. Paired t-test was used for comparison of baseline muscle strength and PEFR with the parameters at different time points. Association between muscle strength and PEFR was tested with the Pearson-correlation test. RESULTS: Muscle strength was 50 to 60%, 75% and 100% of baseline at 15, 45 and 210 minutes after extubation, respectively. PEFR was 50 to 60%, 75% and 100% of baseline at 15, 60 and 180 minutes after extubation. The Pearson-correlation test established a positive correlation between handgrip strength and PEFR (correlation-coefficient 0.86). CONCLUSION: A significant reduction in the postoperative muscle strength can be detected using an objective forced dynamometer to measure handgrip strength even when train of four count has returned to unity and even when there are no clinical signs of muscle weakness. The residual muscle weakness is significant enough to affect the PEFR in the postoperative period.