Regional anaesthesia and thromboprophylaxis
Neuraxial (spinal or epidural) anaesthesia and analgesia are commonly used in major surgery and may provide several advantages over systemic analgesia, including superior analgesia, reduced blood loss and need for transfusion. However, there is an increased risk of spinal canal bleeding when used in patients who have a coagulopathy or who are receiving anticoagulant drugs. The incidence of neurological sequellae following haemorrhagic complications related to neuraxial block is not definitively known, although a literature review by Tryba 1993 estimated it to be <1/150,000 after epidural anaesthesia and <1/220,000 in spinal anaesthesia (Tryba 1993).
Assessment of the associated risk with concurrent use of neuraxial anaesthesia and antithrombotic therapy is crucial, since bleeding complications following neuraxial block may be difficult to detect and may lead to serious consequences. Serious adverse events associated with vertebral canal haematoma include spinal cord ischaemia and transient or permanent paraplegia. Since the spinal canal is an enclosed space, the bleeding may be occult and difficult to diagnose. Furthermore, the presence of postoperative sensory and motor deficit due to the local anaesthetic effect may delay the diagnosis of spinal haematoma.
Anticoagulants that are commonly used in surgical patients include (Horlocker 2003):
• Thrombolytic drugs
• Antiplatelet drugs
• Oral anticoagulants
• Unfractionated heparin
• Low molecular weight heparin
• New anticoagulants (direct thrombin inhibitors and fondaparinux)
Several studies have helped to identify more accurately patients who may be more susceptible to spinal haematoma during a neuraxial block:
• Patients with anatomic abnormalities – spina bifida occulta, spinal angioma, ankylosing spondylitis, spinal ependymoma, and vascular malformations (Vandermeulen 1994)
• Patients receiving antiplatelet medications and oral anticoagulants directly before or after the spinal or epidural anaesthesia (Vandermeulen 1994)
• Patients in whom needle placement is difficult or bloody, and patients requiring multiple punctures (Vandermeulen 1994)
• Female gender, advanced age (>65 years), and a history of easy bruising (Vandermeulen 1994; Owens 1986; Horlocker 1995)
The decision to perform spinal or epidural anaesthesia/analgesia should be made on an individual case basis, balancing the risk of spinal haematoma against the benefits of regional anaesthesia:
• History of unusual bleeding during previous surgery or trauma, medical history, inherited disorders of coagulation can provide a useful guide to the patient’s present coagulation status
• Timing of catheter removal relative to timing of anticoagulant drug administration is important
• Monitoring for signs of cord compression in the peri-operative period is crucial
• A prompt diagnosis and intervention in the event of a spinal haematoma is vital to prevent permanent neurological damage
Individual co-morbidities, antithrombotic therapy, and the current coagulation status are important decisive factors in the use of neuraxial anaesthesia and analgesia, and thus have a strong impact on postoperative pain management. Alternative anaesthetic and analgesic techniques are therefore essential to ensure patient safety in those considered to have an unacceptable risk of bleeding during neuraxial anaesthesia.
In response to these patient safety issues, the American Society of Regional Anesthesia and Pain Medicine (ASRA) convened its Second Consensus Conference on Neuraxial Anesthesia and Anticoagulation (April 25-28 2002). The outcomes of this conference are found at the following website: (http://www.asra.com/publications/2nd-consensus-conference.html)