Continuous peripheral nerve blocks and anticoagulation
Take calculated risks. That is quite different from being rash.General George S. Patton (1885–1945)
The increased clinical role and enthusiasm for continuous peripheral nerve block (CPNB) catheters in the anaesthetic and analgesic management of surgical patients is undeniable in modern anaesthetic practice. This is not surprising considering the many benefits regional anaesthesia techniques can provide the surgical patient.1 2 Advances in perioperative venous thromboembolism prevention therapies have paralleled the development of CPNB.3 Unfortunately, these two advances in perioperative patient care have come into conflict because of the risk for haemorrhage, real4 or perceived,5 when CPNB catheters are manipulated in the anticoagulated patient.
In 1993, with the introduction of low molecular weight heparin (LMWH) in the USA, there was a significant increase in the incidence of spinal haematomas after neuraxial anaesthesia.6 Interestingly, the use of LMWH in European surgical practice had been routine for years at this point without significant bleeding complications. Differences in US and European LMWH dosing, and the timing of the dose, possibly contributed to this inconsistency.7 The low incidence of spinal haematoma, even with LMWH use, complicates research into the mechanism(s) of the problem. The devastating nature of spinal haematomas prompted the American Society of Regional Anesthesia and Pain Medicine (ASRA) to convene a Consensus Conference on Neuraxial Anesthesia and Anticoagulation in 1998 for the purpose of establishing practice guidelines. These recommendations were updated in a second conference in 2003.8
The guidelines provided clinicians with a roadmap for navigating the complexities of pharmacologic venous thromboembolism prophylaxis treatment regimens based on decades of peer-reviewed research on the subject. Armed with this information, clinicians who desired their anticoagulated patients to receive the benefits of neuraxial anaesthesia could proceed with confidence, knowing that the risk for bleeding complications had been minimized. Regrettably, minimization does not equate to elimination of risk. The only method available to eradicate bleeding complication risk associated with neuraxial anaesthesia, regardless of the patient's anticoagulated state, would be to avoid the technique altogether. In today's litigious medical practice environment, this approach is tempting, but often the wrong choice for the patient. Fortunately, most anaesthetists choose a more principled approach to regional anaesthesia that is based on available evidence or guidelines allowing them to weigh the risk and benefits of any anaesthetic technique and discuss options with the patient. This approach breaks down when available evidence or guidelines are lacking. This is the case with ASRA Consensus Conference guidelines and CPNB. The Conference statement provided little direction for peripheral regional anaesthesia or CPNB, citing no evidence upon which to base recommendations. The Conference left the issue suggesting that neuraxial guidelines could be applied to peripheral nerve block patients as a conservative approach while admitting this ‘may be more restrictive than necessary’.8
Without clearer guidance regarding how to manage CPNB catheters in the anticoagulated patient, anaesthetists are again tempted to avoid this useful technique without information regarding risk beyond published case reports describing isolated serious complications.4 9 10 The British Journal of Anaesthesia has taken a leading role in providing clinical articles upon which guidelines can be based in the near future. In this issue, Chelly and colleagues11 describe their experience in 670 patients receiving lumbar plexus CPNB for total hip surgery along with warfarin thromboembolic prophylaxis. Although retrospective in its analysis, these types of population-based data are vital if an understanding of CPNB and anticoagulation risk is going to be developed. A prospective, randomized trial, while certainly the gold standard for medical evidence, is unlikely to be obtained due to the overall rare occurrence of CPNB bleeding, the thousands of cases that would be needed to complete such a study, and the improbability of an ethics committee approving such a study. One-third of the patients in the Chelly and colleagues study had an international normalized ratio (INR) greater than 1.4 which is the highest Conference recommended limit for the removal of neuraxial catheters.
Does this suggest that removal of lumbar plexus CPNB catheters in warfarin anticoagulated patients is a ‘safe’ practice? Emphatically no, and the authors note this in their conclusions. Some respected regional anaesthetists do not even consider the lumbar plexus block a very ‘safe’ approach to the lumbar plexus.12 Nevertheless, this article is a basis for cautious optimism in clinicians who use lumbar plexus CPNB catheters for acute pain management in total hip patients anticoagulated with warfarin.
There are other issues with Chelly and colleagues' study. Even though the authors had INR information on patients before removing the lumbar plexus CPNB catheter, the catheters were removed ‘on postoperative day two without any consideration of the INR value’. The one patient who did have bleeding at the catheter site during the study had an INR of 3 when the catheter was removed. Before the author's study, no information was available on the risk of removing a catheter in a patient taking warfarin. It may have been prudent for the authors to set defined parameters for removal of the CPNB catheter in the face of undefined risk to the patient. While such limits are arbitrary, they can be based on clinical experience and provide an additional measure of safety to the patient. If nothing else, increased vigilance in patients with INRs greater than an agreed upon value will facilitate development of initial clinical guidelines that other anaesthesiologists can use to assist in clinical decisions. As time passes and experience with CPNB in anticoagulated patients evolves, initial guidelines can be refined.
This approach has been taken by clinicians at our centre who rely on CPNB catheters for the management of pain in combat wounded who are anticoagulated with LMWH.13 Using the Conference guidelines as a starting point coupled with their extensive experience in CPNB catheters, a set of practice parameters was established for the use of CPNB in LMWH-treated casualties.13 These parameters were not as restrictive as the Conference neuraxial guidelines. Of note, based on the multiple case reports describing delayed development of retroperitoneal haematoma in patients receiving LMWH after lumbar plexus single injection block or CPNB,10 14 our group elected to manage lumbar plexus blocks using Conference guidelines for neuraxial blocks. Lumbar plexus CPNB was used 88 times in the 187 casualties treated between March 2003 and April 2004 with CPNB and LMWH, and there were no catheter-related bleeding complications. However, like Chelly and colleagues study, this sample population is too small to avoid the possibility of a type II error.
The effort by Chelly and colleagues to better define the risk of CPNB in anticoagulated patients is commendable. This work, while not as definitive as a randomized, controlled clinical trial, is no less vital to the advancement of the speciality. This manuscript and similar works should figure prominently in the next Consensus Conference and provide clinicians better information concerning peripheral nerve block and anticoagulation. In the absence of a ‘cookbook’ for anaesthesia practice, the anaesthesia community depends on academic research like this to provide the clinical evidence and experience that, combined with good clinical judgement, allows for calculated risk management in anaesthesia practice. These safety measures will ultimately benefit our patients and provide a more secure environment in which to practice the art and science of regional anaesthesia.
Walter Reed Army Medical Center
Uniformed Services University of the Health Sciences
Walter Reed Army Medical Center
6900 Georgia Avenue NW
Washington, DC 20307-5001
USA
* E-mail: chester.buckenmaier{at}amedd.army.mil
References
1 Capdevila X, Dadure C, Bringuier S, et al. Effect of patient-controlled perineural analgesia on rehabilitation and pain after ambulatory orthopedic surgery: a multicenter randomized trial. Anesthesiology (2006) 105:566–73.[CrossRef][Web of Science][Medline]
2 Evans H, Steele SM, Nielsen KC, Tucker MS, Klein SM. Peripheral nerve blocks and continuous catheter techniques. Anesthesiol Clin North Am (2005) 23:141–62.[CrossRef][Medline]
3 Geerts WH, Pineo GF, Heit JA, et al. Prevention of venous thromboembolism: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest (2004) 126:338S–400S.[CrossRef][Web of Science][Medline]
4 Bickler P, Brandes J, Lee M, Bozic K, Chesbro B, Claassen J. Bleeding complications from femoral and sciatic nerve catheters in patients receiving low molecular weight heparin. Anesth Analg (2006) 103:1036–7.
5 Ben-David B, Joshi R, Chelly JE. Sciatic nerve palsy after total hip arthroplasty in a patient receiving continuous lumbar plexus block. Anesth Analg (2003) 97:1180–2.
6 Rowlingson JC, Hanson PB. Neuraxial anesthesia and low-molecular-weight heparin prophylaxis in major orthopedic surgery in the wake of the latest American Society of Regional Anesthesia guidelines. Anesth Analg (2005) 100:1482–8.
7 Bergqvist D, Wu CL, Neal JM. Anticoagulation and neuraxial regional anesthesia: perspectives. Reg Anesth Pain Med (2003) 28:163–6.[CrossRef][Web of Science][Medline]
8 Horlocker TT, Wedel DJ, Benzon H, et al. Regional anesthesia in the anticoagulated patient: defining the risks (the second ASRA Consensus Conference on Neuraxial Anesthesia and Anticoagulation). Reg Anesth Pain Med (2003) 28:172–97.[CrossRef][Web of Science][Medline]
9 Maier C, Gleim M, Weiss T, Stachetzki U, Nicolas V, Zenz M. Severe bleeding following lumbar sympathetic blockade in two patients under medication with irreversible platelet aggregation inhibitors. Anesthesiology (2002) 97:740–3.[CrossRef][Web of Science][Medline]
10 Weller RS, Gerancher JC, Crews JC, Wade KL. Extensive retroperitoneal hematoma without neurologic deficit in two patients who underwent lumbar plexus block and were later anticoagulated. Anesthesiology (2003) 98:581–5.[CrossRef][Web of Science][Medline]
11 Chelly JE, Szczodry DM, Neumann KJ. International normalized ratio and prothrombin time values before the removal of a lumbar plexus catheter in patients receiving warfarin after total hip replacement. Br J Anaesth (2008) 101:250–4.
12 Boezaart AP, Rosenquist RW. The lower the indications, the higher the complications. Reg Anesth Pain Med (2005) 30:413–4.[Web of Science][Medline]
13 Buckenmaier CC III, Shields CH, Auton AA, et al. Continuous peripheral nerve block in combat casualties receiving low-molecular weight heparin. Br J Anaesth (2006) 97:874–7.
14 Aveline C, Bonnet F. Delayed retroperitoneal haematoma after failed lumbar plexus block. Br J Anaesth (2004) 93:589–91.
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