To the Editor:—
We read with interest the report of Blumenthal et al.1 of a case of prolonged neurologic deficits after regional anesthesia in a patient with an undiagnosed (subclinical) neuropathy. We congratulate the authors on the exemplary treatment of the patient with a neurologic complication—early evaluation, appropriate investigations, and adequate support and follow-up till resolution.
However, we are not clear how this case report should change our future practice. The author's opening statement that “Nerve injury is a well-recognized complication [italics our own] of peripheral nerve blocks” is misleading in that it implies that nerve injury related to regional anesthesia is a common occurrence. Large series have already shown that neurologic deficits after peripheral nerve block are mostly transient and, overall, very uncommon.2 Even neurologic complications specific to continuous catheter techniques are reported as infrequent.3 The etiology of neurologic complications is polyfactorial, and there are multiple possible causes of neurologic deficit after surgery, most of which are more common than those related to the regional anesthetic technique.4,5 Even in this case, with the evidence from the investigations conducted, it is not absolutely certain that the tourniquet was not at least partly responsible for the nerve injury.
This case does, however, highlight the complications associated with subclinical neuropathy. These are probably more common than appreciated, given the high incidence of diabetes (and other causes of neuropathy) in our clinical workload. The preoperative diagnoses of a subclinical neuropathy may not be possible unless specific preoperative investigations are directed toward this etiology. Further, there may be an overall increased susceptibility to the other etiologies of nerve injury.6,–8 Whether the finding of this risk factor will lead to fewer patients being offered regional anesthesia (and/or tourniquets) is speculative and open to further discussion. Nonetheless, the results of this case further reinforce the fact that in the unfortunate event of a postoperative neurologic deficit, the findings of preexisting subclinical neuropathy could become important. Advocacy of regional anesthesia and careful discussion of its benefits (balanced by its risks) should begin preoperatively and continue even in the event of an adverse outcome or complication. We believe that the benefits of peripheral nerve blocks are significant and the risks, although present, are very low and that regional anesthesia should be offered to all suitable patients.
