Equipment Neuromuscular Monitoring
How does TOF change with degree of NMB?
Say it out loud first.
| Prior to NMBD | Normal, equal, four twitches | |
| After intubating dose of NMBD | No response Complete block = ToF 0, ToF ratio 0, PTC 0 – required for relaxation of larynx, diaphragm, upper abdominal muscles | |
| After partial block by suxamethonium | 4 twitches of equal but sub-maximal height | |
| After partial non-depolarising NMBD | 4 twitches of decreasing height (with fade) Deep block = PTC ≥ 1 (1-5), ToF 0/4, TOF ratio 0 Moderate block: ToF 1-3/4 Shallow block: ToF 4/4, ToF ratio < 0.4 Minimal block: ToF 4/4, ToF ratio 0.4-0.9 | |
| Earliest acceptable point of reversal | Minimum 3 twitches | |
| Following successful reversal | Four full twitches Recovered block: ToF 4/4, ToF ratio > 0.9 |
Fade hysteresis = higher T4:T1 ratio during onset than recovery
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