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Psoas compartment block for lowe extremity surgery - a meta-analysis.
- Marcel A de Leeuw (12 March 2009)
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Length of postoperative analgesia after psoas compartment block.
- Dr R.R. Byreddy, Dr C.M.Harper, Dr S.M.White (2 February 2009)
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Marcel A de Leeuw, anesthesiologist Zaans Medical Center, Zaandam, The Netherlands
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We thank Dr Byreddy for his interest in our review and the interesting data presented. In response to the question concerning the duration of analgesia with PCB, it is important to distinguish between pain quantified using a visual analogue scale (VAS) and opioid consumption. Although they are both measures of pain intensity the two do not necessarily correlate. To determine the duration of blockade with PCB it makes more sense to analyse VAS scores as the VAS is a patient-centered outcome and direct measure of analgesia. Fig. 1 in our meta-analysis is based on the studies by Stevens et al and Biboulet et al. This plot demonstrates that compared to opioids, single-injection PCB results in lower VAS scores only during first 4-8 hours following block injection. A continuous infusion however reduces VAS scores for the duration of the infusion as demonstrated in fig. 3. Opioid consumption on the other hand is an indirect measure of pain intensity. We agree with Dr Byreddy that PCB is associated with an opioid sparing effect and therefore a lower cumulative opioid intake following surgery. This is demonstrated in fig. 2 of the paper which shows significantly lower opioid consumption up to 24 hours following surgery. Cumulative opioid consumption, however, provides no information on the duration of block with PCB. In fact as a result of opioid sparing in the early postoperative period cumulative opioid consumption would be expected to be lower in patients that have received a PCB at all time periods following surgery. To estimate the duration of block with PCB using opioid consumption it makes more sense to analyse hourly opioid consumption or opioid consumption over short time intervals within a 48 hour period. Unfortunately, this data is not available in the literature we identified for review. We therefore reiterate our finding that compared to the gold standard (postoperative opioid titration), PCB is only effective for analgesia during the first 4-8 hours following surgery. This analgesic effect results in reduced opioid titration in the early postoperative period which in turn results in a lower cumulative opioid intake following surgery. This conclusion is consistent with Dr Byreddy’s findings although we cannot confirm his observation of reduced cumulative opioid consumption beyond 24 hours as a result of lack of data in the studies we analyzed. Our conclusion also supports the PROSPECT guidelines on single-injection PCB for hip surgery which recommends a cautious appraisal of the risk/benefit ratio of single-injection PCB on a case by case basis. S.T. Touray, M.A. de Leeuw, W.W.A. Zuurmond and R.S.G.M. Perez. Conflict of Interest:None declared |
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Dr R.R. Byreddy, SpR Anaesthesia Brighton Anaesthesia Research Forum, Royal Sussex County Hospital, Eastern Road, Brighton, East Suss, Dr C.M.Harper, Dr S.M.White
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Editor- we read Touray et al.’s review of psoas compartment block (PCB) for lower extremity surgery with considerable interest1. Whilst our own practice mirrors the benefits of PCB suggested by their meta-analysis, namely superior analgesia after hip surgery compared to either opioid or ‘3-in-1’ block analgesia, we were surprised by the conclusion that the duration of analgesia after single injection PCB is limited to the first 4-8 hrs postoperatively. We have recently completed an audit of morphine requirements in the immediate post-operative phase of 100 patients receiving PCB for hip surgery (elective and emergency). 80 patients did not require any morphine in the postanaesthesia care unit; 20 required 5-10mg morphine. Analysis up to 48 hours postoperatively suggests a morphine-sparing effect greater than that suggested by Touray et al., with a mean morphine requirement of 10mg over this time period. Our findings are more in line with those reported by Stevens et al.2, and support the recommendations of the PROSPECT working group’s conclusion that PCB is a valuable technique in the management of analgesia for patients who have undergone total hip arthroplasty. Furthermore, we suggest that the extended duration of single-shot PCB may be of greatest benefit to elderly patients undergoing hip fracture surgery, in whom renal and respiratory co-morbidities may preclude excessive perioperative opioid analgesia4 – although research remains to be done to support this hypothesis. References 1. Touray ST, de Leeuw MA, Zuurmond WWA, Perez RSGM. Psoas compartment block for lower extremity surgery: a meta-analysis. Br J Anaesth 2008 101: 750-60. 2. Stevens RD, van Gessel E, Flory N, Fournier R, Gamulin Z. Lumbar plexus block reduces pain and blood loss associated with total hip arthroplasty. Anesthesiology 2000; 93: 115–21 3. PROSPECT Working Group. Total Hip Arthroplasty. http://www.postoppain.org/frameset.htm. Accessed 30th January, 2009. 4. Conway BR, Fogarty DG, Nelson WE, Doherty CC. Opiate toxicity in patients with renal failure. Br Med J 2006; 332: 345-6. Conflict of Interest:None declared |
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