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Correspondence |
Toronto, Ontario
To the Editor:
We wish to comment on the article by Korscielniak-Nielsen et al.1 regarding upper limb brachial plexus blockade by the targeted approach. First, the authors claim that this approach reduces total anesthetic time compared with the single injection approach because block supplementation for the single-injection recipients was time-consuming. However, the success rates for complete blockade in the singleinjection group was only 54%. Even when the author excludes those supplementary blocks unnecessary for surgery, success increased to only 65%. This is a high failure rate. Most studies produce successful blockade in 85-100% of subjects2–6 and the single-injection technique is faster. Second, 22% of the targeted group experienced tourniquet pain, compared with 4% in the single-injection group. As brachial plexus blockade is the regional technique of choice for prolonged surgery, tourniquet pain to this degree may become a limiting factor when using the targeted approach. Third, the author states that the targeted method may be safer, as 17% of single injection recipients developed signs of intravascular injection and local anesthetic toxicity. This incidence is high,5,6 perhaps due to the large volumes of mepivacaine (80 mL). Would smaller volumes (40-60 mL), result in a lower incidence of complications?
Finally, is it logical to assume that injection of four individual nerves may increase the incidence of complications four fold, for a technique that is generally very well served by a single-injection approach. We feel that the targeted method does not have as many benefits as the author claims, when compared with the classic single-shot approach.
References
1
Koscielniak-Nielsen ZJ, Nielsen PR, Sørensen T, Stenør M. Low dose axillary block by targeted injections of the terminal nerves. Can J Anesth 1999; 46: 658–64.
2 Selander D. Axillary plexus block: paresthetic or perivascular (Editorial). Anesthesiology 1987; 66: 726–8.[Medline]
3
Horlocker TT, Kufner RP, Bishop AT, Maxson PM, Schroeder DR. The risk of persistent paresthesia is not increased with repeated axillary block. Anesth Analg 1999; 88: 382–7.
4 Schroeder LE, Horlocker TT, Schroeder DR. The efficacy of axillary block for surgical procedures about the elbow. Anesth Analg 1996; 83: 747–51.[Abstract]
5
Palve H, Kirvela O, Olin H, Syvalahti E, Kanto J. Maximum recommended doses of lignocaine are not toxic. Br J Anaesth 1995; 74: 704–5.
6 Pearce H, Lindsay D, Leslie K. Axillary brachial plexus block in two hundred consecutive patients. Anaesth Intensive Care 1996; 24: 453–8.[Medline]
Copenhagen, Denmark
The main object of Drs. Coleman and Day’ letter is the low success rate of axillary block by single injection in our study. They refer to one editorial view,2 and four studies,3–6 neither randomized nor controlled. In a review of RCTs of axillary block in the Cochrane Controlled Trial Register, Medline and Embase between 1966 and 1998, the average success rates were: single injection (13 RCTs - 67%), catheter injection (9 RCTs - 61%), double injections (9 RCTs - 73%, multiple injections (5 RCT’s - 84%) whereas almost all retrospective studies of axillary block in the same period reported higher success rates.
Tourniquet pain was a disturbing factor and we did not recommend low doses for a standard axillary block: surgical analgesia is better after four targeted, than after one large injection. Drs. Coleman and Day postulate that smaller volumes (40-60 ml) by single injection are as effective as a large volume (80 ml). The only RCT addressing this question shows that they are equally ineffective.2
Theoretically, four injections are more dangerous than a single injection. However, assessment of the needle- nerve distance, which is possible with a nerve stimulator, use of atraumatic needles (pencil-point) and injections above and below the axillary artery reduce the risks of nerve damage and of accidental arterial puncture. The risk of accidental intravenous injection may be increased, but is compensated for by a smaller dose of a local anesthetic per injection. Therefore, while a single large dose intravascular injection results in loss of consciousness, grand-mal seizures and/or cardiac arrest, the small dose produces tachy- or bradycardia, circumoral numbness, headache and muscle twitches.
References
1 Koscielniak-Nielsen ZJ, Stens-Pedersen HL, Lippert FK. Readiness for surgery after axillary block: single or multiple injection techniques. Eur J Anaesthesiol 1997; 14: 164–71.[Medline]
2 Vester-Andersen T, Christiansen C, Sørensen M, Kaalund-Jørgensen HO, Saugbjerg P, Schultz-Møller K. Perivascular axillary block II: influence of injected volume of local anaesthetic on neural blockade. Acta Anaesthesiol Scand 1983; 27: 95–8.[Medline]
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