Fig. 12.1
Diagram of a train-of-four (TOF) stimulation and of a post-tetanic count (PTC). Various impulse strengths can be chosen from peripheral nerve stimulator
During nerve stimulation, it is important that the area of stimulation is warm enough, in order to receive a valid result. Ideally, skin temperature should be >35 °C and most certainly at least >32 °C.
12.1.4.2 Reversal of Neuromuscular Blockade
The most common medications used for reversal of non-depolarizing muscle relaxants are acetylcholine esterase inhibitors, most commonly neostigmine and edrophonium. They can be used if there is at least one twitch after the TOF stimulus, which is equivalent to a relative receptor block of about 90 %. It is, however, safer to wait until at least 25 % of the receptors have recovered, equivalent to a TOF of three or four.
A requirement for the evaluation of a valid TOF is that no PTC was performed 10 min prior to the TOF. Attending anesthesiologist Dr. Eldridge was therefore correct when he said that reversal of neuromuscular blockade could not yet be done.
Sugammadex is in Europe available for reversal of deep rocuronium blockade [3]. The medication is costly and therefore not routinely used.
>> Dr. Leto made herself comfortable next to Ms. Lee. The patient was breathing regularly and the end-expiratory CO 2 showed normocapnia. Every minute, she did a TOF measurement, always with the same negative result. Dr. Leto had often seen that atracurium worked an unexpectedly long time, but 80 min was a new personal record. She documented the last vital signs on the anesthesia record and suddenly everything started to happen very quickly. Ms. Lee moved her legs, sat up with a jerk, and attempted to extubate herself. As she fought to get her arms free, she yanked out her IV.
Dr. Leto jumped up, removed the endotracheal tube fixation, ripped off the cuff’s external balloon, and extubated Ms. Lee. Ms. Lee promptly lay down again and went back to sleep. Dr. Leto stopped the propofol infusion and held an oxygen mask over Ms. Lee’s face. “Strange,” she thought, as she set off another TOF test, “still negative.”
Ten minutes later, Ms. Lee woke up again and was transferred to the PACU. One hour later, she went to the ward.
The incident bothered Dr. Leto, so she went to see the patient the next day, with her nerve stimulator in her pocket. Ms. Lee was very happy with the anesthesia and couldn’t remember a thing. The TOF measurement that Dr. Leto did once again was still negative.
12.2 Case Analysis/Debriefing
12.2.1 What Is Your Explanation for the Negative Nerve Stimulation?
CMT disease usually affects the lower extremities, especially the peroneal nerve. Neurophysiological tests show:
A reduction of the nerve conduction velocity
An extended latency period
A reduction in action potential amplitude
Anatomically, axon degeneration often remains clinically unapparent for a long time. In the most serious cases with disease progression over many, many years, neurophysiological alterations on the upper extremities can be seen, especially in the area of the ulnar and median nerves. The result is that monitoring the muscle relaxation is with great difficulty or not possible at all [4].
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