ADVERSE EFFECTS FOLLOWING NERVE BLOCK IN KNEE ARTHROPLASTY

Abstract

Regional anaesthesia, and the supplementation of either general or spinal anaesthesia with nerve block is well established and becoming increasingly more popular. Femoral, sciatic and obturator nerve blockade, in alone or in combination, by means of single shot or continuous infusion has been shown to significantly improve pain control and post operative nausea and vomiting (PONV). We identify equally significant morbidity associated with this practice, with delayed post operative rehabilitation, increase in length of stay, reduction in range of movement and local adverse symptoms at the site of injection and paraesthesia at 3 months post operatively.

2 surgeons were recruited to contribute 100 consecutive total knee replacements each to this study. Each worked exclusively with a one anaesthetist. Each had a predictable and different practice. One employed either spinal or general anaesthesia which the surgeon supplemented with end of operation infiltration of soft tissues in the surgical field including the capsule and skin incision with ropivacaine 300mg, adrenaline 500μg and ketorolac 30mg with normal saline added to make a volume of 100ml. The second employed either spinal or general anaesthesia but supplemented this with a single combined femoral and sciatic nerve block performed pre-operatively. Intravenous opiate analgesia administed via patient controlled analgesia pump for 24 hours post operatively, paracetamol 1g 6 hourly and ibuprofen 300mg 8 hourly where appropriate were prescribed by both anaesthetists. We recorded the incidence of insertion of urinary catheter, deep venous thrombosis diagnosed within 3 and 12 weeks, recovery of lower limb power to grade 5/5, range of movement achieved in each postoperative day and at 12 weeks post operatively, length of stay in addition to PONV and pain scores using the visual analogue scale (VAS) and collected every 6 hours. Localised pain and tenderness at the site of injection was noted at 12 weeks, and persistent paraesthesia.

As predicted patients in the group receiving nerve block has significantly less pain and post operative nausea and vomiting (p< 0.05). There was no statistically significant difference in the use of urinary catheters (p = 0.052) or the incidence of deep venous thrombosis (p=0.58). There was however a significant difference in the recovery of lower limb power (p = 0.023), range of movement recorded at 24hr intervals (p=0.038) (at 12 weeks p=0.54) and length of stay in hospital (0.038). One patient had an almost complete femoral nerve palsy at 12 weeks and required a manipulation under anaesthesia of her knee following recovery of same.

Nerve blockade is an increasingly popular method of controlling post-operative pain. We demonstrate some adverse effects on rehabilitation following this practice in addition to the increased financial and logistical burden of a longer inpatient stay.