Why do we see TOF ratios greater than 100%?

• When monitoring Train of Four prior and post NMBA administration, ratios of more 100% are often noticed and might go as high as 147%.
• The effect is ascribed to the mobilization of presynaptic acetylcholine in the Neuromuscular Junction (NMJ) after T1 promoting release in synaptic cleft during subsequent stimulations.
• Both the Stimpod NMS450X and TOF-Watch SX (uncalibrated) show values greater than 100%.

Suzuki T, Fukano N, Kitajima O, Saeki S, Ogawa S, 2006.’Normalization of acceleromyographic train-of-four ratio by baseline value for detecting residual neuromuscular block.’ British Journal of Anaesthesia; 96:44–7