Risks & Benefits of Peripheral Nerve Blocks

The use of peripheral nerve blocks (PNBs) in multimodal analgesia has increased in hospital and ambulatory settings, and the technique confers multiple benefits. In addition to improved postoperative pain and more rapid recovery, PNBs are also associated with reductions in opioid use and the average length of hospital stay.¹

In a qualitative review published in the Journal of Clinical Anesthesia, anesthesiologists from several US universities examined the risks and benefits of single-shot PNBs (sPNBs) and continuous PNBs (cPNBs) using a perineural catheter.²

According to their analysis of randomized trials comparing the efficacy of PNBs and opioids, PNBs resulted in lower pain scores for at least 24 hours postoperatively–and up to 72 hours in some studies–as well as reduced opioid use.³ Other research has shown that combining PNBs with opioids led to greater pain control than the use of opioids alone.⁴

The evidence suggests that cPNBs offer advantages over sPNBs, including a longer duration of analgesia. In an analysis that included 21 studies comparing the 2 approaches, cPNB was associated with reduced pain scores and opioid use on postoperative days 1 and 2.⁵

Additionally, with some of the  patients having received  cPNB were able to return home sooner followingsurgery, and those who received cPNB until the fourth day after surgery demonstrated readiness for discharge sooner than those who received it for just 1 day after surgery.⁶

One of the risks of PNB is vascular puncture; this can be reduced by using ultrasound to guide placement of the block.

Neurologic complications have been reported in up to 8.2% of patients receiving PNB, and rates are higher with the use of interscalene blocks (ISBs), compared to blocks in other locations (3.5% vs 0.5%, P=.002).^7,8 It is unclear whether the risk of nerve damage is higher with sPNB or cPNB.

Results of multiple studies indicate that PNBs of the lower extremities may increase the risk of falls, though such findings have been mixed. In 3 randomized trials, 7% of patients who received cPNB experienced falls, compared to no falls in those who received perineural saline (P=.013), and a meta-analysis showed that the risk of falls was almost 4-fold in patients who had received cPNB of the lumbar plexus, compared with those having received sPNB or no PNB.^9,10

“However, avoiding the use of cPNB is unlikely to eliminate the risk of falls and may have a negative impact on pain management and recovery,” wrote the authors of the current review.

The usefulness of sPNB is limited due to the short duration of action, while a major limitation of cPNB is the significant investment–in terms of equipment cost, necessary infrastructure, and provider training–required by facilities providing it. A minor complication of cPNB is the risk of catheter dislodgment and catheter site-related issues.

While cPNB resolves the problem of sPNB’s short-lived effect, certain patients may not be candidates for it “because of comorbid conditions, logistical issues, or unwillingness to participate in management,” the authors stated. “Additional PNB modalities are needed to reach this population, in addition to minimizing risks of complications and costs among patients who are cPNB candidates.”

Summary and Clinical Applicability

Though single-shot and continuous peripheral nerve blocks offer many advantages in multimodal analgesia, each approach has unique limitations, primarily the shorter duration with the single-shot technique and the requirement of significant resources with the continuous method.  

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References

1. Liu Q, Chelly JE, Williams JP, Gold MS. Impact of peripheral nerve block with low dose local anesthetics on analgesia and functional outcomes following total knee arthroplasty: a retrospective study. Pain Med. 2015; 16(5):998-1006.
2. Joshi G, Gandhi K, Shah N, Gadsden J, Corman SL. Peripheral nerve blocks in the management of postoperative pain: challenges and opportunities. J Clin Anesth. 2016; 35: 524-529.
3. Chan EY, Fransen M, Parker DA, Assam PN, Chua N. Femoral nerve blocks for acute postoperative pain after knee replacement surgery. Cochrane Database Syst Rev. 2014; (5):CD009941.
4. Bates C, Laciak R, Southwick A, Bishoff J. Overprescription of postoperative narcotics: a look at postoperative pain medication delivery, consumption and disposal in urological practice. J Urol. 2011; 185(2):551-555.
5. Bingham AE, Fu R, Horn JL, Abrahams MS. Continuous peripheral nerve block compared with single-injection peripheral nerve block: a systematic review and meta-analysis of randomized controlled trials. Reg Anesth Pain Med. 2012; 37(6):583-594.
6. Ilfeld BM, Mariano ER, Girard PJ, et al. A multicenter, randomized, triple-masked, placebo-controlled trial of the effect of ambulatory continuous femoral nerve blocks on discharge-readiness following total knee arthroplasty in patients on general orthopaedic wards. Pain. 2010; 150(3):477-484.
7. Fredrickson MJ, Kilfoyle DH. Neurological complication analysis of 1000 ultrasound guided peripheral nerve blocks for elective orthopaedic surgery: a prospective study. Anaesthesia. 2009; 64(8):836-844.
8. Sites BD, Taenzer AH, Herrick MD, et al. Incidence of local anesthetic systemic toxicity and postoperative neurologic symptoms associated with 12,668 ultrasound-guided nerve blocks: an analysis from a prospective clinical registry. Reg Anesth Pain Med. 2012; 37(5):478-482.
9. Ilfeld BM, Duke KB, Donohue MC. The association between lower extremity continuous peripheral nerve blocks and patient falls after knee and hip arthroplasty. Anesth Analg. 2010; 111(6):1552-1554.
10. Johnson RL, Kopp SL, Hebl JR, Erwin PJ, Mantilla CB. Falls and major orthopaedic surgery with peripheral nerve blockade: a systematic review and meta-analysis. Br J Anaesth. 2013; 110(4):518-528.