Background
Pain after hip arthroscopy is variable but can be severe [11-point Numerical Rating Scale (NRS-11) pain scores of 10] despite multimodal analgesia. Although postoperative rescue regional analgesia is useful in these cases its efficacy may be limited by the maximum safe dose of local anaesthetic (LA) permissible when high-dose intra-articular local anaesthetic (IALA) has already been used. IALA may reduce acute postoperative pain after hip arthroscopy, however neither its optimum dose nor timing of administration have been systematically evaluated.
Methods
In 132 randomly assigned adult patients scheduled for therapeutic hip arthroscopy we compared the effects of two different doses of IALA given at procedure end (Group L [low-dose]: 100mg ropivacaine; Group H [high-dose]: 200mg ropivacaine). We also investigated the effect of an additional pre-emptive dose at the beginning of the procedure (Group P [pre-emptive]: 100mg ropivacaine at procedure start and end).
Results
There were no statistically significant differences between groups for NRS-11 pain scores in recovery (mean[SD]: Group L – 2.2[1.9]; Group H – 2.3[2.1]; Group P – 2.7[2.5]; lowest p = 0.6), or post recovery Visual Analogue Scale (VAS) pain scores [largest mean difference VAS 1.5 hours: 5mm (p = 0.32); VAS 2 hours: 5mm (p = 0.35); VAS 4 hours: 2mm (p = 0.7); VAS 6 hours: 3mm (p = 0.7)]. There were also no significant differences in antiemetic usage and requirement for rescue fascia iliaca block (FIB) between groups.
Conclusions
Compared to a single 100 mg dose of ropivacaine at the end of the procedure, we were unable to demonstrate any advantage of either a higher dose IALA or a pre-emptive dose IALA when multimodal analgesia is used. Lower-dose IALA could reduce total systemic LA absorption if a given rescue regional analgesic LA dose is used postoperatively.