◊ BACKGROUND:
High-volume infiltration analgesia may be effective with a low risk of side effects in hip and knee arthroplasty. The present placebo-controlled study was carried out to evaluate the analgesic effect of high-volume infiltration analgesia in bilateral total knee arthroplasty, along with a detailed description of the infiltration technique.
◊ METHODS:
In a randomized, double-blind, placebo-controlled trial in 12 patients undergoing bilateral knee arthroplasty, saline or high-volume (170 ml) ropivacaine (0.2%) with epinephrine was infiltrated around each knee, with repeated doses administered through an intra-articular catheter for 24 h and pain and opioid requirements assessed for 48 h in a fast-track setting.
◊ RESULTS:
Pain at rest and during movement was significantly reduced for up to 32 h with the high-volume local anesthetic infiltration technique. No major side effects were observed. The median hospital stay was 4 days.
◊ CONCLUSION:
High-volume infiltration analgesia is effective in knee arthroplasty and, due to its simplicity, may be preferable compared with other analgesic techniques in knee arthroplasty.
◊ Reviewed by W. Harrop-Griffiths, MD
Imperial College Healthcare NHS Trust, London
There is an increasing consensus that the analgesic technique used for lower limb joint replacement should not only provide effective pain relief but should also allow early mobilisation. Epidural analgesia, once very popular for hip replacement and commonly used for knee replacement, is falling out of fashion, to be replaced in many centres by peripheral nerve blocks. Although undoubtedly effective, these can delay mobilisation by up to 36 h after surgery. Two Australian clinicians - Kerr and Kohan [1] - published a case series in 2008 that detailed an infiltration technique using large volumes of dilute ropivacaine to which is added ketorolac and adrenaline. This study by Andersen et al is the first to take this technique and assess it with a randomised, controlled trial. Although only 12 patients were studied, they underwent bilateral knee replacement and were thus able to act as their own controls, a powerful statistical ruse that highlights differences readily.
Surgery was conducted under spinal anaesthesia. One knee was infiltrated with ropivacaine 0.2% during and at the end of surgery. A catheter was left in place; further ropivacaine was injected down the catheter at 8 h and 24 h after surgery. For the other knee, the ropivacaine was replaced by saline. All patients were given paracetamol, celecoxib, gabapentin and a morphine PCA after surgery. The primary endpoint was pain as measured on a 0 – 10 numerical rating scale.
The results show that the use of ropivacaine by infiltration was associated with significantly lower pain scores between 4 h and 26 hours after surgery. However, it is worth noting that the median pain scores at 45 degrees of knee flexion during this period were approximately 8/10 in the saline-treated knee and 6/10 in the ropivacaine-treated knee. The median morphine consumption in the Post-Anaesthesia Care Unit (PACU) was 20 mg.
The authors accept that this technique is at an early stage of development and that further study and perhaps modification will be required both to optimise the technique and to prove its value in knee replacement when compared with other, established techniques. However, I think that their confident declaration that “high-volume infiltration analgesia is effective in knee arthroplasty” should not be accepted without qualification. While the differences in pain scores between the ropivacaine and saline knees were undoubtedly statistically significant and welcomed by the patients, one has to ask how the scores would compare with those achieved with other regional analgesic techniques. The fact that morphine consumption in PACU was high in this study suggests that the analgesia, even with the ropivacaine infiltration, was less than ideal. A better summary of the results of this study might therefore be that “high-volume infiltration analgesia is better than nothing in knee arthroplasty”.
The Holy Grail for lower limb joint replacement is good analgesia with early mobilisation. This study may be a small step towards this goal, but it is not a giant leap. However, it is a promising technique that needs to be compared with single-shot and continuous peripheral nerve blocks performed with low concentrations of local anaesthetic. It is not possible to say which of these two techniques will prove to be the more popular in years to come. I will simply say that at this stage, I would rather have sciatic and femoral nerve blocks performed by an expert regional anaesthetist and risk staying in bed for a few more hours than the surgeon would prefer. But that is only my opinion!
[1] Kerr DR, Lohan L. Local infiltration analgesia: a technique for the control of acute postoperative pain following knee and hip surgery. Acta Orthopaedica 2008; 79: 174-83
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