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Department of Anesthesiology University of Tuebingen Tuebingen, Germany
To the Editor:
I have read with great interest the article by Sia et al. (1) comparing onset time and success rate of the multiple injection axillary brachial plexus block performed with neurostimulation guidance versus paresthesia elicitation. I would like to express my general concern against the use of needle-evoked paresthesia for peripheral nerve blocks. Recently, Kaufman et al. (2) reported a series of seven patients suffering from severe, debilitating chronic pain states after peripheral nerve blocks. In all seven cases, painful paresthesias were elicited at the time of the nerve block, be they voluntary or accidental, with a progress to a severe chronic pain condition. Neurological complications following peripheral nerve blocks, referred to as postblock neuralgia, show an incidence of 0.2% (3), 1.7% (4) up to 12.5% (5). Symptoms mostly are moderate and transitory, with a tendency of spontaneous recovery within times related to nerve regeneration and repair mechanisms (6). Therefore, I feel that deliberate needle-elicited paresthesias are at least a questionable clinical standard because growing strong evidence exists that even minor nerve damage can proceed to intractable chronic pain (7). Thus, the principle "primum non nocere" should be kept in mind when performing peripheral nerve blocks to assure maximum patient safety.
References
Department of Anesthesiology Centro Traumatologico Ortopedico Firenze, Italy
In response:
We read with interest the letter from Dr. Kiefer, which contains a general concern against the practice of paresthesia-elicitation for peripheral nerve blocks, an old and still unresolved question.
The results of clinical studies with regard to the role of paresthesia in the development of nerve injury are conflicting. Neurological complications after peripheral nerve block (postblock neuralgia) may follow an axillary block performed by paresthesia elicitation as well as transarterial approach and peripheral nerve stimulation (1–4).
Selander et al. (5) reported a more frequent incidence of postoperative nerve injury after axillary blocks in patients in whom a paresthesia was sought (2.8%) compared with that in patients undergoing a transarterial technique (0.8%), although the difference was not significant. Auroy et al’s study (6), a prospective survey of regional anesthesia complications, demonstrated that paresthesia was a consistent precursor in a high percentage of nerve injury cases involving neural blockade. Four of 21,278 peripheral nerve blocks were associated with nerve injury; in all of these cases, needle puncture was associated with either paresthesia during puncture or with pain during injection.
A recently published article analyzed the 670 claims for nerve injury from the ASA Closed Claims Project (7). Of the 13 brachial plexus injury associated with regional blocks, paresthesias were noted in four axillary blocks. In two of these blocks, paresthesias occurred during injection of the local anesthetic. The mechanism of injury was attributed to the performance of an axillary block in three cases of ulnar nerve damage (no paresthesia noted), in three of radial nerve (one with paresthesia) and in five of median nerve (two with paresthesia).
In a retrospective analysis performed on 607 patients undergoing repeated axillary blocks, a 1.2% frequency of anesthesia-related neurologic complications was found (8). No regional anesthetic technique risk factors, including elicitation of paresthesia, were found. A paresthesia was elicited in nearly 60% of blocks; one or more paresthesias were elicited in five of seven patients with a persistent neurologic problem. The postoperative nerve deficit occurred in the distribution of an elicited paresthesia in four of five patients (8).
Fanelli et al. (4) in a prospective study on 3996 patients undergoing peripheral nerve blockade by nerve stimulation, recorded an incidence of neurologic dysfunction of 1.7%. Although 15% of patients complained of unintentional paresthesia during block placement, the follow-up failed to confirm that paresthesia elicitation is a risk factor for postoperative nerve injury. The only variables showing significant association with the development of postoperative neurologic dysfunction in the last two studies were the tourniquet inflation pressure (4) and the total tourniquet time (8). Individual case reports describe serious nerve injury after peripheral blocks performed by paresthesia elicitation (9), transarterial injection (10), peripheral nerve stimulation (11).
Kaufman et al’s case report (9) describing a group of seven patients suffering from severe chronic pain after peripheral nerve block requires some comment. All these patients experienced significant discomfort during the block procedure and described their blocks as: "unbelievable," "extremely painful," "the most painful experience of his life," "more painful than anything he had ever experienced before," "the most excruciating pain she had ever experienced." These terms are not commonly used to describe a normally conducted paresthesia elicitation technique. It was not specified in any of the seven cases if the painful sensation happened during the nerve localization procedure or local anesthetic injection. The authors themselves wrote about "presumed intraneural injection."
We do not agree with Moore et al’s (11) classical assertion "No paresthesia, no anesthesia," as we found that nerve stimulation allows a more reliable nerve trunk localization, especially when the radial or the musculocutaneous nerves are involved in the surgical area (12). However, we think that there are insufficient data to recommend an absolute avoidance of paresthesia technique.
Clinical prospective studies, however challenging, need to be performed to clear up the role of paresthesia elicitation in producing postoperative nerve dysfunction. In particular, the main controversy to settle is, in our opinion, if neurological complications are because of the technique per se or because of technical errors. First, it is necessary to exclude the role of all the factors that may independently cause injury to the nerves, such as preexisting injury, patient position, surgical trauma, and tourniquet use. Second, any wrong technical approach must be ruled out. Paresthesia should be elicited with the greatest care, using a fine needle. Repeated and rough probing of the nerves should be avoided, a partially anesthetized nerve should not be reblocked, and the blocks should not be performed in adults under general anesthesia or deep sedation. In case of pain during injection, the procedure must be stopped immediately and the needle withdrawn. Every complaint of pain during the procedure must be evaluated with consideration given to changing or even abandoning the block if necessary. Even Kaufman et al. (9) concluded their case report by arguing that "It is likely that the risk of devastating iatrogenic disability can be minimized if a few basic principles are respected during the administration of peripheral blocks."
References
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