Development and Internal Validation of a Multivariable Risk Prediction Model for Severe Rebound Pain After Lower Limb Orthopedic Surgery Involving Single-Shot Popliteal Sciatic Nerve Blocks: A Single Centre Retrospective Cohort Study

Rebound pain is a well-recognized phenomenon after the resolution of peripheral nerve blocks. Severe rebound pain is prevalent after ambulatory surgery, with potential resultant increased health-care utilization and cost. Risk factors for severe rebound pain may include younger age, female sex, high preoperative pain score, bone surgeries, and upper limb surgeries. Use of tourniquet for lower limb procedures is also associated with worse postoperative pain compared to without. Protective factors may include continuous perineural catheter, regional anesthesia adjuncts, and multimodal oral pain management prior to resolution of peripheral nerve blockade. However, placement of continuous peripheral nerve block catheters utilizes additional health care resources; hence, a targeted approach where continuous perineural catheters are offered to patients at the highest risk of severe rebound pain could potentially offer the biggest benefit.

The aim of the study is to derive and validate a multivariable prediction model for severe rebound pain after lower limb surgery involving popliteal blockade, to assist with risk stratification and shared decision making.

The primary model endpoint is severe rebound pain, defined by transition from well-controlled pain (numerical rating scale [NRS] 3 or less or patient report of satisfactory pain control) in the post anesthetic care unit (PACU) while the block is working to severe pain (NRS pain score 7 or greater) within 48 h of block performance. This definition is modified from that of Barry et al., 2020 as clinically, the investigators have noted some patients having sensory blocks lasting more than 24 hours with the use of adjuncts.