Use of a single injection femoral nerve block in the patients of total knee replacement with concomitant epidural analgesia

Abstract

Background: Since central neuraxial analgesia cannot provide adequate post operative pain relief when it is used alone in patients who had undergone Total Knee Replacement Surgery (TKR), an alternative analgesic method is usually advised. The alternatives include either systemic analgesics (opioids, Non Steroidal Anti Inflamatory Drugs, [NSAIDs], etc) or peripheral nerve blocks. When complete analgesia is aimed in such patients, combining the sciatic nerve blocks along with the Femoral Nerve Blocks (FNBs) will be beneficial. But performing femoral and sciatic nerve blocks together in patients with regional or general anaesthesia will be too cumbersome and in this direction, the major clinical trials are yet to decide on their feasibility. Thus, in an attempt to keep the analgesia methods very simple and effective, the physicians may decide on doing a single nerve block when an ongoing epidural analgesia infusion is in situ.

Aim: To evaluate the safety, convenience and the efficacy of a single injection femoral nerve block in patients who had undergone TKR surgeries, who had received concomitant epidural sensory analgesia.

Methods: The patients who had undergone TKR were inserted with an epidural catheter for continuous analgesia and this was supplemented with an additional single injection femoral block. Postoperatively, each patient was recorded with a Visual Analogue Score (VAS) of pain assessment. The total number of patients who required additional bolus doses of epidural and additional analgesics, the individual patient ratings, and the complications, if any, were noted and analyzed on day 1(D1) and day 2(D2) of the surgery.

Results: The mean time for developing a VAS score of at least 3 was 8.55±1.78 hours. The VAS assessment mean scores were compared to that of D2 and the ratio which was obtained was 0.4±0.32. The mean VAS scores were higher on D2 as compared to those on D1 and they were statistically significant (P<.0001). A categorical score comparison too revealed higher scores on D2 (P<.001). A total of 52% patients required bolus doses of epidural analgesia with bupivacaine on D2 as compared to those on D1 (16%). Additional analgesia on demand was noted in 21% patients on D1 in contrast to 67% patients on D2. The rating of the analgesia as 'excellent' by 29% patients, as 'good' by 46% patients, as 'adequate' by 17% patients and as 'poor' by 8% patients was noted on D1. Similarly, the ratings as 'excellent' by 4% patients, as 'good' by 29% patients, as 'adequate' by 58% patients, and as 'poor' by 8% patients, was recorded for D2, respectively (P<.001).

Conclusion: A single injection femoral nerve block provides adequate analgesia for the patients who undergo TKR surgery, when an active epidural is in-situ on the day of the surgery. It keeps the analgesic mode as simple and comfortable and it achieves lower pain scores on the day of the surgery, also with least complications, in patients with an ongoing epidural local anaesthetic infusion.

Keywords: Epidural analgesia; Femoral; Nerve block; T knee replacement.

[Table/Fig-3]:

Comparison of VAS on two different days of surgery

[Table/Fig-4]:

Patient rating of analgesia on day 1 and day 2