Closing the loop on relaxant reversal.

In Reply: We thank Dr. Caruso for his comments related to our observational study reporting a substantially increased risk of postoperative residual paralysis in patients having qualitative train-of-four (TOF) monitoring of eye muscles compared with those monitored at the adductor pollicis.1 Reversal of neuromuscular blockade before extubation was assessed clinically as per routine care. Due to the observational nature of the study, we did not standardize what clinical tests that may have been used. We agree with Dr. Caruso that subjective assessment of the response to nerve stimulation, and of clinical tests, is inadequate to confirm successful reversal. Although the presumed mechanism behind the association of monitoring site and residual paralysis would be a more generous administration of neuromuscular-blocking drugs to patients with monitoring of eye muscles, we did not observe differences in neuromuscular-blocking drugs dosing. It is conceivable that patients in the eye muscle monitored group would have had lower adductor pollicis TOF-counts at the time of neostigmine such as tidal volume may explain this finding. While most patients will not be harmed (as shown in this study) by extubating with a train-of-four ratio less than 90, these patients are likely at increased risk of respiratory complications.4 As such, we encourage practitioners to confirm that the reversal drug has had the desired effect. To not do so makes an assumption which will be incorrect in a small but real percentage of patients.

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