Optimizing the dose of local infiltration analgesia and gabapentin for total knee arthroplasty, a randomized single blind trial in 128 patients

Effective analgesia is essential for postoperative recovery and rehabilitation in TKA. The challenge of analgesic regimes is to obtain adequate pain relief and maximum muscle control to mobilize and rehabilitate patients early. However, the optimal dose and best composition are not known. We hypothesized that there would be no differences in reported postoperative pain on the day of the TKA surgery as well as the first day after surgery when different combinations of ropivacain for LIA and gabapentin are given. This prospective randomized trial examined 128 TKA patients treated with LIA and gabapentin in four groups. Group A: 300-mg ropivacain/600-300-300-mg gabapentin. Group B: 150-mg ropivacain/600-300-300-mg gabapentin. Group C: 300-mg ropivacain/300-100-100-mg gabapentin. Group D: 150-mg ropivacain/300-100-100-mg gabapentin. Primary endpoint was pain (NRS) at multiple moments. Secondary endpoints were number of adverse effects, length of hospital stay (LOS), the amount of consumption of pain medication, and wound leakage. Generalized estimating equation (GEE) was used to detect differences between the four groups regarding the course of pain. No differences regarding adverse effects, LOS, and wound leakage were found. GEE revealed a significant difference in course of pain between group A and B, with group B experiencing higher NRS scores postoperatively than group A (p=0.021). No differences between the other groups were found. The results of the current study suggest that LIA with 300-mg (150ml) ropivacain might be more effective than 150-mg (75ml) ropivacain. Alteration in dose of gabapentin appears not to have influence on the course of pain.