Table 1.

Description of Rebound Pain influenced by Block Duration and Baseline Pain, and Case Study Illustrations

Raw data:
Author’s blocks (n=50) with ropivacaine-clonidine-buprenorphine:		22.7 (20.8–24.5) hr duration
Colleagues’ blocks (n=117) with ropivacaine with/without clonidine:		17.4 (16.7–18.2) hr duration
Linear regression analysis demonstrating associations between block duration (hr) and/or preoperative baseline pain with rebound pain (on 0–10 numeric rating scale):
Rebound Pain Score (intercept):	6.10 (95% CI: 4.00–8.20) units
Baseline Pain Score (per unit)	0.22 (95%CI: 0.04–0.40) units	(p=0.016)
Effect of Nerve block duration (per hr):	−0.1 (95% CI: 0.01–0.20) units	(p=0.031)
Case Study Illustration #1 – Patients with Zero Baseline Pain preop and 15 hr duration:
Patient with 15 hr block duration and preop baseline pain score of 0 had a rebound pain score of 4.6
•    6.1 base units minus 1.5 units = 4.6 units on a 0–10 scale
Case Study Illustration #2 – Patients with Zero Baseline Pain preop and 25 hr duration:
Patient with 25-hour duration and preop pain score of 0 had a rebound pain score of 3.6
•    6.1 base units minus 2.5 units = 3.6 units on a 0–10 scale
Case Study Illustration #3 – Patients with Baseline Pain preop of 5, with 15 hr duration:
Patient with 15-hour duration and preop pain score of 5 has a rebound pain score of 5.7
•    6.1 base units plus (5 × 0.22=) 1.1, minus 1.5 units = 5.7 units on a 0–10 scale
Case Study Illustration #4 – Patients with Baseline Pain preop of 5, with 25 hr duration:
Patient with 25-hour duration and preop pain score of 5 had a rebound pain score of 4.7
•    6.1 base units plus (5 × 0.22=) 1.1, minus 2.5 units = 4.7 units on a 0–10 scale
Summary, 10 extra hours of nerve block duration was associated with a decreased Rebound Pain Score by 1 unit, on a scale of 0–10.