Once a niche of only ‘true believer afficionados’, epidural, caudal, spinal, and ultrasound guided peripheral nerve blockade have transformed the practice of pediatric anesthesia. Indeed, regional anesthetic techniques are now foundational, ubiquitous, and integral to our everyday practice. A fundamental question: Is it safe? The Pediatric Regional Anesthesia Network (PRAN) database pioneered the use of a large database to answer this question.1,2 When I read the article by Frawley et al, today’s Pediatric Anesthesia Article of the Day, which investigated the efficacy and safety of lower limb blocks, I thought the ideal reviewer would be my good friend and former colleague Dr. David Polaner who was amongst the original pioneers of PRAN. Myron Yaster MD
Original article
Geoff Frawley, Vanessa Marchesini, Brian Loh, James Koziol. Pediatric lower limb peripheral nerve blocks: Indications, effectiveness, and the incidence of adverse events. Paediatr Anaesth. 2022 Aug;32(8):946-953. PMID: 35451202
As regional anesthesia becomes a nearly ubiquitous practice in pediatric patients, especially for orthopedic operations, peripheral nerve blockade continues to supplant neuraxial techniques for most unilateral and extremity surgeries. The publication of large scale, prospective, rigorously audited data from the Pediatric Regional Anesthesia Network (PRAN) database, the French-Language Society of Paediatric Anaesthesiologists (ADARPEF) studies,3 and others firmly established regional techniques as safe but still left questions to be answered. Neither the PRAN nor the ADARPEF studies were able to report on analgesic effectiveness. While this was an initial goal of PRAN, lack of reliability and confidence in the accuracy of the pain scoring across multiple study centers led to abandoning this metric in the analyses. These studies also did not correlate the specific operation with the block performed and its outcome, but rather looked at the risk and incidence of complications associated with each block independently of surgical factors. In a new single center, retrospective study by Frawley, et al,4 some of these questions are addressed, adding important information to what we already know about the risk of peripheral nerve blocks in children, but also raising further questions.
In their retrospective, single center study, the authors detected four cases of persistent nerve injury. All were in those who underwent tibial osteotomy with application of an external fixator for tibial lengthening in two cases. All cases had an intraoperative popliteal sciatic nerve block. This translates to a population incidence of over four times the neurological complications found in the most recent PRAN study. Note that the nearly ten times figure cited in Frawley, et al’s discussion compares their data to the aggregate findings of all blocks by PRAN, but the PRAN incidence of postoperative neurological complications in 20,367 single injection peripheral blocks of the lower extremity in children over 10 years of age, a cohort more comparable to the population in this study, is actually about 7/10,000 (CI 5-10.7/10,000).
It is critical to emphasize, as do the authors, that one cannot with any certainty attribute these complications to the blocks, not least because causality can never be determined with retrospective studies. Imaging studies in all four patients failed to demonstrate injury at the site of blockade (the popliteal approach to the sciatic nerve) further questioning the causality of the blocks. We know that adverse neurologic outcomes after orthopedic surgery can occur as a result of operative factors, particularly with limb lengthening surgery,5 that can easily be mistaken for block complications, but it is also possible that certain blocks, or performance factors of those blocks, might lend themselves to a higher risk when employed for certain operations.
The authors note that although nerve injury is known to occur with tibial osteotomy in the absence of neural blockade, we cannot be sure that the blocks were not in some way contributory to the outcome. Does the presence of a nerve block, particularly with very high doses of local anesthetic, predispose to or enhance the possibility of surgically induced nerve injury? We have evidence that local anesthetics, particularly at high doses or concentrations, may cause neurotoxicity via multiple cellular pathways.6 Although the doses employed in this study overall were quite high, only one patient who sustained neuropraxia was dosed in the high range. Are blocked nerves more susceptible to injury from stretch or other mechanical factors? It is worrisome that three of the four patients with nerve injury showed signs of CRPS 1. This may also be suggestive of mechanical nerve injury, even if of a relatively trivial nature.
As has been seen in other studies, most notably that by Taenzer and the PRAN investigators,7 there was considerably variability of local anesthetic dosing in this cohort. I think this represents further evidence that unwarranted variability continues to be an issue in pediatric regional anesthesia. The evidence pinpointing the ideal dose for any of these blocks, whether considering volume or concentration, remains elusive, and is fertile ground for additional investigation. Although we cannot eliminate the risk of nerve injury (especially if it is due to surgical factors), reducing local anesthetic toxicity of any nature can be promoted by using the lowest effective dose for a given block.
PS: From Myron
Not discussed by David but mentioned by the authors: the paucity of lower limb trauma in the data presented either reflects the lower incidence of tibia fractures in children or a reluctance to perform lower limb blocks in the setting of potential compartment syndrome. This was my experience when considering either neuraxial or specific peripheral nerve blocks for tibial osteotomy surgery. Surgeons were dead set opposed to using these techniques because of the fear of masking a compartment syndrome.
References
1. Walker BJ, Long JB, Sathyamoorthy M, Birstler J, Wolf C, Bosenberg AT, Flack SH, Krane EJ, Sethna NF, Suresh S, Taenzer AH, Polaner DM, Martin L, Anderson C, Sunder R, Adams T, Martin L, Pankovich M, Sawardekar A, Birmingham P, Marcelino R, Ramarmurthi RJ, Szmuk P, Ungar GK, Lozano S, Boretsky K, Jain R, Matuszczak M, Petersen TR, Dillow J, Power R, Nguyen K, Lee BH, Chan L, Pineda J, Hutchins J, Mendoza K, Spisak K, Shah A, DelPizzo K, Dong N, Yalamanchili V, Venable C, Williams CA, Chaudahari R, Ohkawa S, Usljebrka H, Bhalla T, Vanzillotta PP, Apiliogullari S, Franklin AD, Ando A, Pestieau SR, Wright C, Rosenbloom J, Anderson T: Complications in Pediatric Regional Anesthesia: An Analysis of More than 100,000 Blocks from the Pediatric Regional Anesthesia Network. Anesthesiology 2018; 129: 721-732
2. Polaner DM, Taenzer AH, Walker BJ, Bosenberg A, Krane EJ, Suresh S, Wolf C, Martin LD: Pediatric Regional Anesthesia Network (PRAN): a multi-institutional study of the use and incidence of complications of pediatric regional anesthesia. Anesth Analg 2012; 115: 1353-64
3. Ecoffey C, Lacroix F, Giaufré E, Orliaguet G, Courrèges P: Epidemiology and morbidity of regional anesthesia in children: a follow-up one-year prospective survey of the French-Language Society of Paediatric Anaesthesiologists (ADARPEF). Paediatr Anaesth 2010; 20: 1061-9
4. Frawley G, Marchesini V, Loh B, Koziol J: Pediatric lower limb peripheral nerve blocks: Indications, effectiveness, and the incidence of adverse events. Paediatr Anaesth 2022; 32: 946-953
5. Simpson AH, Halliday J, Hamilton DF, Smith M, Mills K: Limb lengthening and peripheral nerve function-factors associated with deterioration of conduction. Acta Orthop 2013; 84: 579-84
6. Verlinde M, Hollmann MW, Stevens MF, Hermanns H, Werdehausen R, Lirk P: Local Anesthetic-Induced Neurotoxicity. Int J Mol Sci 2016; 17: 339
7. Taenzer AH, Herrick M, Hoyt M, Ramamurthi RJ, Walker B, Flack SH, Bosenberg A, Franklin A, Polaner DM: Variation in pediatric local anesthetic dosing for peripheral nerve blocks: an analysis from the Pediatric Regional Anesthesia Network (PRAN). Reg Anesth Pain Med 2020; 45: 964-969