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NewsletterThoracic Epidurals are Worth the Risk of Hematoma Formation in Patients Undergoing Full or Partial Systemic Heparinization 
CON Mihail P. Nikolov, MD
With any therapeutic option, one must always consider the risk: benefit ratio. At the present time, the potential risks of using thoracic epidurals in patients who will subsequently undergo full or partial systemic heparinization far out weigh the potential benefits. The potential benefits of thoracic epidurals include postoperative analgesia, stress response attenuation, and thoracic cardiac sympathectomy 1. However, postoperative analgesia can be achieved easily via other modalities such as intravenous or intrathecal anagesics that do not carry the same risk of hematoma formation as thoracic epidurals. Also, although a few studies have shown that perioperative "stress response" attenuation may be beneficial, it remains a matter of debate. Especially intriguing is thoracic cardiac sympthectomy, which has been shown to initiate coronary artery vasodilation, improve myocardial oxygen supply: demand ratio, improve left ventricular function, and decrease myocardial infarct size in animal models of coronary artery occlusion 1. For patients at risk for myocardial ischemia, the potential benefits are obvious. However, use of thoracic epidurals in patients with ischemic heart disease remains controversial for a wide variety of reasons 2,3. Of primary concern, myocardial ischemia is the end result of multiple pathophysiologic pathways, most importantly being intracoronary clot formation, which thoracic epidurals do not affect 3. The cornerstones of treatment, therefore, remain anticoagulation and platelet inhibition, both of which increase risk of hematoma formation if a thoracic epidural catheter is inserted 3. Furthermore, pharmacologic options such as beta-adrenergic blockers, angiotensin-converting enzyme inhibitors that improve myocardial oxygen supply: demand ratio are available that have proven efficacy in patients with ischemic heart disease yet do not carry risk of hematoma formation 3. The estimated incidence of hematoma formation following routine epidural catheterization is approximately 1:150,000 yet this is probably an underestimation l .Epidural hematoma is now the most common mechanism of spinal cord injury in the American Society of Anesthesiologists Closed Claims Project Database and spinal cord injury is the leading cause of claims for nerve injury 4. Although everyone agrees that any degree of anticoagulation before or after catheter insertion increases risk, there is little objective evidence to quantify the magnitude. Owens et al estimated the risk at 0.35% 5. Recently, Ho et al performed an elaborate statistical analysis suggesting risk was approximately 1 :1,500 6. Although there has never been a report of epidual hematoma formation in a patient exposed to full systemic heparinization required for cardiopulmonary bypass, there exist many case reports of hematoma formation with lesser degrees of anticoagulation 1,5,7. An epidural hematoma has profound detrimental neurologic consequences that are often permanent. Rapid diagnosis is very important for timely surgical intervention, which may be difficult in patients following major thoracic or cardiac surgery. Furthermore, subjecting these patients to a second emergent surgical procedure for decompression in the immediate postoperative period would undoubtedly increase morbidity and mortality 7. Little objective evidence exists in the literature to guide an anesthesiologist in the "safe" insertion and removal of a thoracic epidural in a patient who will subsequently undergo full or partial systemic heparnization. Studies are generally small and uncontrolled. Most authors recommend obtaining laboratory evidence of normal coagulation parameters prior to catheter insertion, which increases cost and may delay surgery. Most will delay surgery 24 hours in the event of a bloody tap, which increases cost and upsets surgeons. For cardiac surgery, most insert the catheter the night before surgery, which is impractical. The technique cannot be used in a large number of patients because of preoperative idiopathic or pharmacologic (heparin, aspirin, etc.) coagulopathy. Lastly, more than half of all cases of hematoma formation occur following catheter removal, so care must be taken in the postoperative period. In summary, at the present time, the risk: benefit ratio of using thoracic epidurals in patients who will subsequently undergo full or partial systemic heparinization is not sufficient. The potential benefits of thoracic epidurals can be achieved via other modalities that do not carry risk of hematoma formation, a catastrophic event. Appropriately designed clinical studies are required prior to definitive analysis of the risk: benefit ratio of the technique. History shows that even therapies with sound pharmacologic and physiologic rationale may prove ineffective or even harmful when evaluated by randomized clinical trials 3. References
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