Letters to the Editor: Letters & Announcements
For the time being, no study can demonstrate safety of guideline recommendations on the use of anticoagulants and neuraxial anesthesia. Indeed, the highest risk, found in the literature, of neuraxial hematoma is 1/36001 only after total knee arthroplasty under epidural anesthesia in elderly patients. Thus, a randomized study with greater than 100,000 patients is required to demonstrate safety of any recommendation. This explains why most guidelines are little more than “expert advice” and are so different between continents and even within countries for the same anticoagulant.
The bleeding risk associated with plexus and peripheral nerve block techniques (without or with anticoagulants) is unknown. However, compression neuropathy due to perineural hematoma after peripheral nerve blocks seems to be very uncommon.2 The risk of clinically important bleeding associated with superficial nerve blocks seems to be so low that no precautions other than those appropriate to the surgical procedure are required.
Regarding lumbar plexus block, hematoma inducing neurological compression does exist.3–5 Weller5 described two cases of delayed retroperitoneal hematoma after lumbar plexus block. In the first case, the hematoma was diagnosed on postoperative day (POD) 4 but vessel trauma was suggested by blood aspiration after catheter placement. Enoxaparin 30 mg twice daily had been started 40 h after insertion of the catheter. In the second case, no apparent vessel trauma was noted during needle stimulation and heparin was started 8 h later, clinical symptoms of retroperitoneal hematoma occurred on POD three. Because of a deep plexus blockade, we decided in Expert study6 to classify this puncture as a neuraxial puncture. The reason is that hematoma cannot be diagnosed by direct vision as femoral block, but in case of deep block. We need radiographic imaging (Compressive Ultrasonography or magnetic resonance imaging).
Furthermore, the symptoms occur between POD 3 and 173 and thus all patients should be monitored carefully and regularly for the symptoms and signs of femoral compression until POD 17. In practice, this is not that easy.
The pharmacokinetic profile of each anticoagulant is different. For example, the half-life is only 5 h for low-molecular weight heparin and 16 h for fondaparinux. Therefore, we have to adapt our prescription for indwelling catheter use to the pharmacokinetics of each drug to decrease the risk of compressive hematoma (even if this event is very rare) related to vessel injury. It is quite surprising to read in all recommendations that the time window between the last injection of anticoagulant and the insertion of an indwelling catheter is so important whereas they never focus on the timing of the next injection. Obviously if there is a vessel injury, the risk of hematoma is linked to the last injection, as well as the next one. The time necessary to reach maximum concentration (Tmax) is also quite different for each anticoagulant. For instance Tmax for fondaparinux is only 30–60 min while it is 4 h for low-molecular weight heparin. Thus the risk of hematoma is not the same if the injection is done at the same time after a supposed vessel injury. Only a pharmacokinetic model can suggest the time window appropriate for the injection before and after removal.7 Because of the delay of appearance of clinical symptoms of a compressive hematoma, we also have to focus on the injection following the catheter removal. That is the reason why we decided to skip one injection of fondaparinux to remove a deep catheter after 2 half-lives (36 h) and to administer the next injection 12 h to ensure better hemostasis in the case of a potentially injured vessel.7 The only risk related to this strategy of skipping one injection in the first few PODs is the possibility of an increase in deep vein thrombosis. The expert study was performed to evaluate this risk.6 The results demonstrated that deep vein thrombosis rate is not different after skipping one injection with a trend of even lower risk in this group (probably because regional anesthesia can improve early mobilization without pain).
Finally, new ACCP guidelines8 about recommendations for the prevention of DVT state: “bleeding complications have been described with the use of continuous deep nerve blocks. Bleeding may be related to the experience of the anesthesiologist and may be reduced by use of ultrasound-guided catheter placement. Until further data become available, we recommend that the above suggestions for neuraxial blocks also be considered for deep peripheral nerve blocks.”
Nadia Rosencher, MD
Department of Anesthesiology and Intensive Care
Cochin Hospital (AP-HP)
Paris 5 University
1. Moen V. Severe Neurological Complications after Central Neuraxial Blockades in Sweden 1990–1999. Anesthesiology 2004;101:950–9
2. Capdevila X, Pirat P, Bringuier S, Gaertner E, Singelyn F, Bernard N, Choquet O, Bouaziz H, Bonnet F; French Study Group on Continuous Peripheral Nerve Blocks. Continuous peripheral nerve blocks in hospital wards after orthopedic surgery: a multicenter prospective analysis of the quality of postoperative analgesia and complications in 1,416 patients. Anesthesiology 2005;103:1035–45
3. Aveline C, Bonnet F. Delayed retroperitoneal haematoma after failed lumbar plexus block. Br J Anaesth 2004;93:589–91
4. Hsu DT. Delayed retroperitoneal haematoma after failed lumbar plexus block. Br J Anaesth 2005;94:395; author reply 395–6
5. Weller R, Gerancher J, Crews J, Wade K. Extensive retroperitoneal hematoma without neurologic deficit in two patients who underwent lumbar plexus block and were later anticoagulated. Anesthesiology 2003; 98:581–5
6. Singelyn F, Verheyen CCPM, Felicissimo P, Piovella F, Van Aken HK, Rosencher N. Use of neuraxial catheter for Anesthesia/ analgesia in major orthopedic lower limb surgery Patients treated with prophylactic dose of fondaparinux in routine practice. J Thromb Haemost 2005;3(Suppl 1):1102–3
7. Rosencher N, Bonnet MP, Sessler DI. Selected new antithrombotic agents and neuraxial anaesthesia for major orthopaedic surgery: management strategies. Anaesthesia 2007;62:1154–60
8. Geerts WH, Bergqvist D, Pineo GF, Heit JA, Samama CM, Lassen MR, Colwell CW; American College of Chest Physicians. Prevention of venous thromboembolism: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Chest 2008; 133(6 Suppl):381S–453S