Regional anaesthesia in patients treated with aspirin and clopidogrel
London, UK
* E-mail: robert.self{at}rmh.nhs.uk
Editor—I read the recent review on coronary artery stents and non-cardiac surgery1 with interest. Howard-Alpe and colleagues refer to the difficult clinical situation in which an anaesthetist wishes to perform a central neuroaxial block on a patient treated with antiplatelet therapy. The authors suggest preoperative platelet transfusion ‘if regional neuroaxial blockade is thought to be essential’ for emergency surgery. I wish to highlight three practical difficulties in transfusing platelets in order to allow a central neuroaxial block to be performed.
First, how many pools of platelets should be transfused? The authors cite French guidelines from 2003, which refer to platelet count.2 However, it is likely that patients on antiplatelet therapy will have a platelet count of > 100 000 µl–1 and the platelet count tells us little about platelet function. A recent healthy volunteer study suggests that at least two to three pools of platelets may be required to normalize platelet function after clopidogrel and aspirin administration.3
Secondly, how can platelet function be monitored after platelet transfusion to decide that a block may be safely performed? None of the platelet function tests described in the review will exclude the possibility of the very rare complication of haematoma after an epidural or spinal block. The platelet count may be normal despite abnormal platelet function, as demonstrated in pre-eclampsia.4 A case report of spinal anaesthesia in a patient taking clopidogrel and aspirin describes the use of platelet aggregometry to monitor the effect of platelet transfusion.5 However, as Howard-Alpe and colleagues state, this technique is laboratory-based and therefore may be unavailable to the clinician.
Finally, is the risk of platelet transfusion before central neuroaxial block offset by the perceived benefits of the block to the patient? Platelet transfusion is not without risk, including administration errors, and bacterial contamination of platelets.6
Until anaesthetists have further data to support the safety (or otherwise) of epidural and spinal anaesthesia in patients taking both clopidogrel and aspirin, it is likely that those patients in ‘whom regional neuroaxial blockade is thought to be essential’ will be confined to a small group, such as those awaiting lung transplantation.5
Oxford, UK
* E-mail: georgina.howard-alpe{at}nda.ox.ac.uk
Editor—I would like to thank Dr Self for his interesting and informative letter. In our review article,1 we highlighted the difficulties and risks associated with performing neuroaxial blockade in patients taking dual antiplatelet therapy with aspirin and clopidogrel. We presented the dilemmas that arise in the care of a patient on dual antiplatelet therapy, who needs emergency surgery where neuroaxial blockade is felt to be essential. The question of how many pools of platelets need to be transfused to perform neuroaxial blockade safely was an issue we discussed. We quoted the French guidelines of 2003,2 stating that in the absence of platelet dysfunction, for spinal anaesthesia a platelet count of 50 000 µl–1 should be achieved and for epidural anaesthesia, 80 000 µl–1. Obviously, in the case of aspirin and clopidogrel therapy, there is platelet dysfunction in the absence of thrombocytopenia. However, at the time we wrote our article, the amount of platelet transfusion needed to safely reverse the combined effects of clopidogrel and aspirin therapy was not known. Consequently, we welcome Dr Self's reference to the recently published healthy volunteers study suggesting at least two to three pools of platelets are needed to normalize platelet function after clopidogrel and aspirin therapy,3 and would advise any clinician to follow this recommendation in the absence of alternative guidelines.
With regard to Dr Self's second point, we would agree that no platelet function test excludes the rare possibility of haematoma after spinal or epidural anaesthesia. Haematoma is a rare complication of neuroaxial blockade that has also been reported in patients not taking either anticoagulant or antiplatelet therapy. In our article, we referred to two separate case reports of haematomas after spinal and combined spinal and epidural anaesthesia; in both cases, the clopidogrel was stopped 7 days before the procedure.7 8 As with many aspects of medicine nothing is guaranteed, and patients must be made aware of the possible complications of anaesthesia at consent. Dr Self drew attention to the case report we quoted where platelet aggregometry was used to guide the correction of platelet function with platelet transfusion before neuroaxial blockade in the patient undergoing emergency surgery while awaiting lung transplantation.5 We believe that in the increasingly litigious world in which we practice medicine, the security of a normal result on platelet function testing, or correction of an abnormal result with platelet transfusion, will enable the anaesthetist to feel and prove they did all possible to avoid the devastating complication of epidural haematoma. We agree that the platelet count may well be normal, despite abnormal platelet function as can be the case in pre-eclampsia and, as we highlighted, in the patient taking antiplatelet therapy. It is precisely for this reason that we advise if you suspect abnormal platelet function, you should perform platelet function testing and correct the platelet function as guided by the test result or, if testing is unavailable, transfuse platelets before you proceed.
Finally, we also agree that platelet transfusion is not without risks to the patient and increasingly platelets are an expensive and scarce resource. Not only, as stated by Dr Self, are there risks of administrative errors, transfusion reactions, and infective contamination, but also in this patient subgroup, the risk of thrombosis associated with platelet transfusion is high. Subsequently, we do not advise neuroaxial blockade in the emergency scenario in patients on dual antiplatelet therapy with aspirin and clopidogrel unless there is an essential indication for the block such as end-stage respiratory disease. In the elective scenario, guidelines state that clopidogrel should be stopped for 7 days before neuroaxial blockade and aspirin can be safely continued. This strategy does not completely rule out the possibility of epidural haematoma, but reduces the risk significantly. We believe that communication between members of the clinical team and the patient involved with a full explanation of the risks and benefits of different perioperative strategies is vital as in all situations.
Editor's comment: This subject was addressed further in the review article in September's British Journal of Anaesthesia on antiplatelet drugs and anaesthesia.9 In relation to regional anaesthesia and antiplatelet drugs, the authors addressed the perceived opinion that regional is safer than general anaesthesia in elective, at risk patients and stated ‘We conclude that the risk/benefit ratio of preoperative withdrawal of antiplatelet drugs in order to perform a regional or neuraxial blockade is not justified’.
References
1 Howard-Alpe GM, De Bono J, Hudsmith L, Orr WP, Foex P, Sear JW. Coronary artery stents and non-cardiac surgery. Br J Anaesth (2007) 98:560–74.
2 Samama CM, Djoudi R, Lecompte T, Nathan-Denizot N, Schved JF. Perioperative platelet transfusion: recommendations of the Agence Francaise de Securite Sanitaire des Produits de Sante (AFSSaPS) 2003. Can J Anaesth (2005) 52:30–7.
3 Villahur G, Choi BG, Zafar MU, et al. Normalisation of platelet reactivity in clopidogrel-treated subjects. J Thromb Haemost (2007) 5:82–90.[CrossRef][ISI][Medline]
4 Davies JR, Fernando R, Hallworth SP. Hemostatic function in healthy pregnant and preeclamptic women: an assessment using the platelet function analyzer (PFA-100®) and thromboelastograph®. Anesth Analg (2007) 104:416–20.
5 Herbstreit F, Peters J. Spinal anaesthesia despite combined clopidogrel and aspirin therapy in a patient awaiting lung transplantation: effects of platelet transfusion on clotting tests. Anaesthesia (2005) 60:85–7.[CrossRef][ISI][Medline]
6 Serious Hazards of Transfusion—Annual Report 2005. Available from www.shotuk.org.
7 Litz RJ, Gottschlich B, Stehr SN. Spinal epidural haematoma after spinal anaesthesia in a patient treated with clopidogrel and enoxaparin. Anesthesiology (2004) 101:1467–70.[ISI][Medline]
8 Tam NL, Pac-Soo C, Pretomas PM. Epidural haematoma after combined spinal-epidural anaesthetic in a patient treated with clopidogrel and dalteparin. Br J Anaesth (2006) 96:262–5.
9 Chassot P-G, Delabays A, Spahn DR. Perioperative antiplatelet therapy: the case for continuing therapy in patients at risk of myocardial infarction. Br J Anaesth (2007) 99:316–28.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  L. T. Newsome, R. S. Weller, J. C. Gerancher, M. A. Kutcher, and R. L. Royster Coronary Artery Stents: II. Perioperative Considerations and Management Anesth. Analg., August 1, 2008; 107(2): 570 - 590. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||