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In TOF, electrodes are placed on the patient's wrist, and the number of thumb twitches is counted. After the NMBA infusion is begun, thumb twitches are measured every 30 min for 2 hr to ensure the appropriate level of paralysis has been reached. The absence of contractions indicates that too much NMBA is being given; 1 to 2 twitches indicate the appropriate level of drug is being administered, and 3 to 4 twitches indicate the need to increase the infusion rate. Once the desired level is reached, response to peripheral nerve stimulation is measured every 4 hr.
Patients retain sensory nerve function and awareness of their surroundings, so analgesics and sedatives are usually administered concurrently. Whether TOF augments clinical assessment of neuromuscular blockade is controversial; it may be more useful with some neuromuscular blocking agents (e.g., vecuronium) than others.