Impact of peripheral nerve blocks on opioid use following flap reconstruction involving the lower extremity: A systematic review and meta-analysis.

[BACKGROUND] Peripheral nerve blocks (PNBs) are recommended by several multimodal pain regimens, but the evidence supporting their use in lower extremity surgery is limited. This study aimed to evaluate the association between PNBs and opioid use for free flap reconstruction involving the lower extremity.

[METHODS] We conducted a systematic review on the use of PNBs in lower extremity surgery, followed by a blind, dual extraction of the study outcomes. Variables of interest included opioid use (intravenous [IV] morphine milligram equivalents [MMEs]), patient-reported pain, length of surgery (hours), and length of stay (days). We then performed meta-analyses using random effects models for mean difference (MD).

[RESULTS] We included 11 studies comprising 417 patients for analysis. PNBs were significantly associated with reduced 24-hour (MD=-15.4 IV MMEs, p<0.05) but not total postoperative opioid use (MD=-80.3 IV MMEs, p>0.05). Patients who received PNBs reported significantly less pain at 24 h (standardized MD=-0.72 IV MMEs, p<0.05) but not 48 h (standardized MD=-0.21, p>0.05). Length of stay was 0.6 days shorter for patients who received PNBs (p<0.05), but length of surgery was not significantly different (MD=0.06 h, p>0.05). When considering the data from only randomized controlled trials, total opioid use was significantly reduced for patients who received PNBs (MD=-19.62 IV MMEs, p<0,05), but there was no difference in the length of stay (MD=-0.28 days, p>0.05).

[CONCLUSION] Peripheral nerve blocks may offer statistically significant reductions in postoperative opioid use, particularly within the first 24-hours postoperatively, but the clinical significance of this reduction is relatively minor (approximately 4 to 6 oxycodone 5-mg equivalents).