Succinylcholine is still used in clinical practice. Its duration is highly variable and neuromuscular monitoring is recommended to assess its recovery. Unfortunately, depolarizing neuromuscular block cannot be evaluated by train-of-four (TOF) as no fade occurs. Only single twitch (ST) allows to monitor depolarizing block. The TOFScan monitor proposes a modified TOF ratio (T4/Tref) not referring to fade within a TOF series. We hypothesized that the T4/Tref allows to assess recovery from succinylcholine. This observational study aims to compare recovery from depolarizing block simultaneously assessed with T4/Tref and ST. After Ethics Committee approval and written informed consent 45 patients receiving a single dose of succinylcholine were included. ST recovery, measured with TOF-Watch SX, and T4/Tref recovery, measured by TOFScan, were assessed simultaneously. Difference between measurements was compared using Mann-Whitney U test and overall concordance with the intraclass correlation coefficient (ICC). The ICC was 0.85 [95% CI 0.82-0.87]. The first T4/Tref ratio ≥ 90% was 97% [95% CI 93-101%] the corresponding ST value was 91% [95% CI 87-97%]. The first T4/Tref ratio ≥ 100% was 103% [95% CI 102-107%], the corresponding ST value was 104% [95% CI 100-106%]; median [95% confidence interval of the median]. Time to recovery to 90% and 100% of baseline did not differ between ST or T4/Tref. It was10.0 [8.0-13.0] min vs 10.0 [8.0-12.0] min, P = 0.307 and 10.0 [9.0-15.0] min vs 10.0 [8.0-15.0] min, P = 0.546; respectively; median [IQR]. Agreement between both parameters was excellent. The T4/Tref can be used accurately to measure recovery from depolarizing neuromuscular block.
Keywords: Depolarizing neuromuscular blockade; Neuromuscular blocking agents; Single twitch monitoring; Succinylcholine; Train of four.
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