◊ BACKGROUND:
Postoperative regional analgesia for total knee replacement can provide excellent pain control and speedy rehabilitation compared with systemic opioid analgesia but the optimal technique to provide best analgesia with minimal adverse effects remains unclear. We carried out an observer-blinded randomized trial of side-directed epidural infusion with lumbar plexus infusion after total knee arthroplasty.
◊ METHODS:
Sixty patients scheduled for total knee replacement were randomized to receive epidural or lumbar plexus infusions of levobupivacaine and clonidine. Pain, sensory and motor block were assessed at 0, 6, 24 and 48 h postoperatively. Range of knee movement and mobility were assessed on the first and second postoperative days.
◊ RESULTS:
No significant differences were detected between the epidural and lumbar plexus groups in 24-h pain scores at rest (median visual analogue scale, 30 mm (interquartile range, 10-45) vs. 39 mm (17-51), P = 0.286), and on movement (48 mm (20-66) vs. 60 mm (47-81), P = 0.068). The only statistically significant difference in pain scores in favour of the epidural groups was at 6 h postoperatively (P < 0.001). Median morphine usage in the epidural group was 0 mg (interquartile range, 0-35) compared with 14.5 mg (0-44) in the lumbar plexus group (P = 0.33). Range of movement (epidural: median 70 degrees (interquartile range, 58-75) vs. lumbar plexus: 70 degrees (50-75), P = 0.79) or mobility was similar between groups. Adverse effects were also similar between groups, apart from a higher incidence of bladder catheterization in the epidural group (37.9% vs. 12.5%, P = 0.04).
◊ CONCLUSIONS:
Lumbar plexus infusion is a reasonable alternative to epidural anaesthesia for total knee arthroplasty.
◊ Reviewed by P. Narchi, MD
Anesthesia Department, Clinical center, Soyaux, France
This well-designed study confirms once again that peripheral nerve block provides analgesia comparable to an epidural after total knee replacement (TKR). Patients in the epidural group had an original “unilateral epidural analgesia” using a side-directed epidural catheter. Based on Borghi’s study, this technique seems attractive to provide selective unilateral epidural analgesia. However, the authors in this study did not assess the unilateral effects. Moreover, if “unilaterality” was clinically demonstrated, one could still argue about the high incidence (37.9%) of urinary retention in the epidural group.
In their discussion, the authors addressed the issue of the “ideal peripheral block after TKR”. Indeed, the controversy about this has been extensively discussed in previous studies. First, a single shot block cannot overcome postoperative pain after TKR. In fact, these patients require early-on intensive physiotherapy during their hospital stay in order to achieve a 90 degree flexion of the knee before discharge. It is obvious that physiotherapy is less comfortable and effective if pain is not adequately controlled. Thus, a regional catheter seems mandatory. Second, the equivalent analgesia of lumbar plexus block (whether psoas or femoral blocks) and standard epidurals makes it very logical to move away from the epidural space. Third, Kaloul et al (Can J Anaesth 2004) have already demonstrated that analgesia provided to the lumbar plexus by either approach, whether posterior (psoas compartment block) or anterior (femoral nerve block), are clinically comparable even if block of the obturator nerve is more frequent with the posterior approach. Taking all this into consideration, the femoral nerve catheter is considered in many countries as the gold standard for pain relief after TKR.
The authors found that pain scores were comparable between groups except at T6 after surgery. This is in agreement with previous studies which showed that pain after TKR is global around the knee (anterior and posterior pain) during the first 24 hours after surgery suggesting that analgesia should combine femoral nerve block with either systemic opioids or the addition of a single shot sciatic block to cover posterior pain. Thus, the addition of a single shot sciatic block using a long-acting local anesthetic combined with the femoral block leads to complete analgesia of the whole lower limb during the first 24 hours after TKR. However, prolonging its effects by inserting a sciatic nerve catheter is not appropriate because posterior pain resolves after day 1. Furthermore, sciatic catheters may disable the patient to stand and walk in the postoperative period.
The adjunction of clonidine to local anesthetics is known to potentiate surgical anesthesia after bolus injection, especially when short acting local anesthetics are used for surgery (lidocaine or mepivacaine). It is doubtful that adding clonidine to diluted long-acting local anesthetics, postoperatively administered as an infusion, could improve the quality of analgesia after surgery. In addition, the authors showed that clonidine has probably contributed to the development of hypotension in both groups (30% in the epidural group and 26.9% in the LP group). Thus, I would not recommend using clonidine in combination with local anesthetics for postoperative analgesia.
The major disappointment in this study concerns the high incidence of accidental dislodgement of these catheters, whether epidural (23%) or LP (34%). The readers would have appreciated getting some more details on the way these catheters have been secured. Accidental dislodgement of nerve catheters are mainly observed with superficial blocks such as the lateral approach to the interscalene space where the incidence may vary between 15-40%. However, lumbar plexus and epidural blocks are considered as “deep blocks” because the distance from the skin to the nerves is significantly greater. The high incidence of accidental dislodgement strongly weakens the validity of study results. Moreover, it has contributed to the surprisingly high failure rates in both groups (epidural 30%, LP 27%).
The authors found similar durations of hospital stay after surgery (6 days). However, strict criteria for discharge were not defined beforehand. Moreover, this criterion is known to be highly influenced by the willingness of local medical teams to encourage (and even in some countries to stress on) discharging patients as soon as they achieved a number of criteria. Very often, the duration of stay after TKR is predefined (5-7 days) by surgeons before surgery, even if objective criteria for discharge (such as a 90 degree knee flexion) are achieved earlier than 5 days … Indeed, we all know, from our clinical practice, that some patients may achieve these objective discharge criterias 3 or 4 days after surgery while others may need 5, 6 or 7 days after surgery. So, if the duration of stay observed in this study (6 days in both groups) was not attributed to “objective criterias” such as 90 degree knee flexion (which should have been mentioned in Methods section), the comparison of these results is not valid.
Finally, even if pain scores were found to be comparable between groups after surgery, the readers remain curious about intermediate rehabilitation criteria which were not assessed. Indeed, one of the main advantages of regional analgesia (whether epidural or peripheral nerve catheters) after TKR remains the significantly decreased need for physiotherapy after discharge, as has been demonstrated in many studies.
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