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NewsletterThoracic Epidurals are Worth the Risk of Hematoma Formation in Patients Undergoing Full or Partial Systemic Heparinization 
PRO Patricia Gramling-Babb, MD
No technique in anesthesia has been as controversial as the use of neuraxial blockade in patients undergoing anticoagulation. The patients we are referring to are usually ASA 3 or 4 undergoing either cardiac or aortic surgery and are considered high risk for intraoperative and postoperative morbidity and mortality due to their comorbidities. The question ultimately is whether or not to subject these patients to the risk of a potential catastrophic epidural hematoma. The actual risk of developing an epidural hematoma under these circumstances is not known. Ho, et al collected data from the available literature and attempted to estimate the minimum and maximum risk of a clinically significant hematoma. His estimate ranged from 1: 150,000 to 1:1500 with a 95% confidence level. 1 To date, I am unaware of any reported hematomas in the CABG literature where this technique was used. Although the potential risk is present, it is a very rare occurrence when proper care is taken. Considering the comorbid state of many of these patients, thoracic epidural anesthesia (TEA) can offer a number of benefits to reduce the potential complications often encountered in these patients. The coronary artery bed is heavily innervated by the sympathetic nervous system. In diseased coronary arteries, sympathetic stimulation has a paradoxical effect by inducing vasoconstriction instead of vasodilatation. The exact mechanism is unclear but is attributed to the loss of endothelial integrity or the release of mediators (possibly serotonin) not normally found at the sympathetic terminals. The probable source of serotonin would be platelets that are damaged in the highly turbulent flow of the diseased vessels. 2 This vicious cycle of vasoconstriction causing ischemia can be effectively ablated by TEA. In addition, studies have revealed a preferential shunt of myocardial blood to the endocardium which is not caused by a decrease in left ventricular end-diastolic pressure. There is a 20-25% lower resistance to flow in ischemic areas and no change in normal areas. Infarct size and arrhythmia scores are also lower.3,4 In beta-blocked patients, TEA had little influence at rest but during exercise, global ejection fraction improved while reducing rate pressure product and ST segments improved. 5 Stress response to surgery has always been a concern for high-risk patients. In Liem's study, norepinephrine and epinephrine levels were reduced or more stable in the prebypass and bypass periods as were systemic vascular resistance, heart rate, and mean arterial pressure. At 48 hrs post surgery, the lower pain scores correlated with lower epinephrine and cortisol levels. 6 Physiologic pulmonary changes can be especially significant in thoracic aneurysm surgery through a thoracotomy. A number of factors are involved in inadequate postoperative ventilation, including reduced lung volumes, diaphragmatic dysfunction, and inability to generate sufficient pressures. A study by Fratacci, et al revealed that in spontaneously breathing patients receiving TEA infusions containing local anesthetics, tidal volume, vital capacity, and esophageal, transdiaphragmatic and gastric pressures were all increased.7 In summary, patients can benefit from the neuroendrocrine, cardiac, and pulmonary effects that have been discussed. The risk of a catastrophic hematoma formation is small if proper attention to detail is taken in the placement of the catheter. All patients should have their medications thoroughly reviewed and be questioned about bleeding disorders. If indicated, the appropriate lab testing should be ordered. If at all possible, there should be adequate time between placement of the catheter and anticoagulation. At our institution, nearly all high-risk patients receive some type of neuraxial blockade. The epidurals are placed the day before surgery, if feasible, but other institutions have done them the day of surgery without reported incident. The most experienced hands present should perform the procedure. The anesthetic management should be conducted to allow for early awakening to assess the neurologic status of the patient postoperatively. Following these precautions, the use of TEA in the face of heparinization should afford an acceptable risk.
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