Epidural hematoma is a rare, but serious complication of neuraxial blockade, the frequency of which is affected by patient and practice variables. Recent publications have been epidemiologic series (typically from Europe) or included only cases of epidural hematoma (without overall population demographics).1–7 In this issue, Bateman et al.8 report the frequency of epidural hematoma within a multicenter North American consortium of academic anesthesia departments. Their findings are relevant in that they represent current applications for epidural analgesia as well as risk for epidural hematoma. Specifically, the frequency is similar to that of other recent epidemiologic series (and is higher than reported 2 decades ago when thromboprophylaxis was less aggressive); epidural analgesia for labor and delivery is associated with less risk of symptomatic neuraxial bleeding than epidural analgesia for a non-obstetric surgical indication; and the demographics of the patients reflect the diminished utilization of epidural analgesia for major orthopedic surgery and continued application among high-risk patients undergoing major abdominal, thoracic, or open vascular surgery.
Before the introduction of potent antithrombotic drugs and routine thromboprophylaxis, the risk of neuraxial bleeding after epidural blockade was assumed to be a rare event. For example, in a meta-analysis published in 1993, Tryba9 identified 13 cases of epidural hematoma following 850,000 epidural anesthetics and calculated the incidence to be <1 in 150,000. The following year, Vandermeulen et al.10 reported 46 cases of epidural hematoma associated with epidural anesthesia/analgesia occurring between 1906 and 1994, representing the first century of neuraxial block. Importantly, 60% of cases occurred in the last decade of the study period. The authors stated that it was unclear whether these results represented an increased frequency of epidural hematoma, an increased number of patients undergoing epidural blockade and/or increased reporting of anesthetic complications. On the basis of the meta-analysis performed by Tryba9 and their case series, the authors concluded:10
Knowledge of the pharmacologic properties of the different anticoagulants and their combination with strict patient selection, individual risk-benefit analysis, appropriate regional anesthetic techniques, respecting proper time intervals separating anticoagulant and epidural or spinal anesthesia, and continuous awareness of the possibility that a compressing neuraxial hematoma may develop should enable us to make anesthetic practice safer without withholding anesthetic techniques from patients who would most certainly benefit from them.
It was into this climate of cautious optimism that neuraxial blockade was performed in the presence of low molecular weight heparin (LMWH). Enoxaparin, the first LMWH approved for general use in the United States, was released in 1993. Labeled applications included thromboprophylaxis after total knee and hip replacement, a procedure in which patients are known to have moderate to severe postoperative pain that was successfully treated with epidural analgesia. Safety was not a concern in that >10 years’ experience in Europe. Pharmaceutical companies estimated that several million patients had received LMWH while undergoing neuraxial block with only a single epidural hematoma.11,12 However, in the United States, 40 cases of neuraxial hematoma (over half of which involved an epidural technique) were voluntarily reported through the MedWatch system over a 5-year period (May 1993–May 1998), representing an estimated risk of neuraxial hematoma of approximately 1 in 3000 epidural anesthetics. However, this is most likely an underestimation, because additional epidural hematomas occurred but were not reported to the MedWatch system at the time of the risk calculation.13 The marked disparities in frequencies in the North American and European reports were attributed to differences in dosing, timing of LMWH administration, and preference for spinal (rather than continuous epidural) techniques in Europe.14 The increased risk of epidural hematoma in patients anticoagulated with LMWH prompted a reevaluation of the relative risks and benefits of neuraxial blockade. For example, American Society of Regional Anesthesia and Pain Medicine guidelines recommended against the administration of twice daily LMWH in a patient with an indwelling epidural catheter, noting that improved analgesia was not balanced with the risk of paraplegia.13,14
Not surprisingly, the complication of epidural hematoma became almost synonymous with LMWH administration and epidural analgesia after major orthopedic surgery. However, in the 5 following years, few were described.13 The decline in the number of cases voluntarily reported was ascribed to decreased reporting, publication of national recommendations by the German Society for Anaesthesiology and Intensive Care in 199715 and American Society of Regional Anesthesia and Pain Medicine16 in 1998, and/or avoidance of neuraxial blockade in patients receiving LMWH. However, during this same time frame, and almost certainly associated with the decrease in reported cases, the analgesic superiority of peripheral techniques for patients undergoing total hip and knee replacement was determined.17
It would seem logical that with the number of LMWH-associated cases decreasing, the overall frequency of neuraxial hematoma associated with epidural analgesia would also fall. Unfortunately, that was not the case. More recent series and epidemiologic studies suggest that epidural hematoma after epidural blockade occurs more frequently than initially estimated, ranging from 1:2700 to 1:19,505 patients (1–4, 7, 8), and that there are patient populations at significantly higher risk. For example, Moen et al.7 reported the overall frequency of neuraxial hematoma after epidural block to be 1:18,000, with bleeding occurring rarely in parturients (1:200,000) compared with elderly female patients undergoing total knee replacement (1:3800).7 Similar results by Pöpping et al.1 reported the overall risk of symptomatic epidural hematoma to be 1:4741, but increased to approximately 1:1000 for elderly women undergoing lower extremity surgery.
Bateman et al.8 confirm the findings of Moen et al.7 that obstetric patients undergoing epidural catheterization are at significantly lower risk for spinal hematoma compared with perioperative (non-obstetric surgical) patients undergoing epidural catheterization. There were 7 epidural hematomas among 142,287 patients undergoing epidural anesthesia/analgesia, for an overall risk of 1 in 20,326 epidural catheterizations. However, none of the 79,837 obstetric patients who underwent epidural placement developed a neuraxial hematoma requiring decompressive laminectomy (upper limit of 95% confidence interval, 1:21,643), compared with 7 of 62,450 patients who received perioperative epidural catheter placement (1:9000; 95% confidence interval, 1:22,189–1:4330). This difference in incidence is even more striking when considering that bloody taps are more common in the obstetric population and have been reported to occur in approximately 3% of all obstetric epidural placements.5 The relatively hypercoagulable state of pregnancy may be protective and offers one possible reason for the lower rate of neuraxial hematomas in this population. The normal anatomic changes that occur in the aging spine may provide another explanation for the differing incidence. Both Moen et al.7 and Pöpping et al.1 cited osteoporotic deformities as likely contributing to the risk of symptomatic vertebral canal bleeding after epidural blockade in elderly women. The prevalence of vascular disease, osteoporosis, and degenerative changes of the spine increase with age, ultimately resulting in a decrease in the volume of the epidural space.18 In contrast, the younger obstetric patient has a more compliant epidural space, with the ability to accommodate a larger volume of blood before the onset of symptoms. Magnetic resonance imaging after epidural blood patch revealed blood leaking out through the intravertebral foramina after injection in young individuals.19 To date, all case reports of neuraxial hematomas in obstetric patients have occurred in parturients with an existing coagulopathy (hemorrhage, preeclampsia, hemolysis-elevated liver enzymes-low platelets) either at the time of epidural placement or removal. There have been no published cases associated with antithrombotic/antiplatelet therapy.16
Finally, the surgical procedures of the patients in the series by Bateman et al.8 reflect the diminished utilization of epidural analgesia for major orthopedic surgery. Current evidence suggests that benefits of epidural analgesia are probably limited to high-risk patients undergoing major abdominal, thoracic, or open vascular surgery.20 There is increasing evidence that alternative analgesic techniques, such as wound infiltration with sustained release (liposomal) bupivacaine, wound catheter infusions, and single injection peripheral blocks are as effective as epidural analgesia for many patients undergoing these procedures. Nearly 2 decades ago, peripheral techniques replaced epidural analgesia as the gold standard for patients undergoing major lower extremity surgery. As the prevention and treatment of thromboembolism progresses, we must continue to evaluate less invasive analgesic methods recognizing, “When you’re at the cutting edge, someone’s going to bleed.”
Dr. Terese Horlocker is the section Editor for Regional Anesthesia for the Journal. This manuscript was handled by Dr. Steven L. Shafer, Editor-in-Chief, and Dr. Horlocker was not involved in any way with the editorial process or decision.
Name: Terese Horlocker, MD.
Contribution: This author helped write and collect data for the manuscript.
Attestation: Terese Horlocker approved the final manuscript and is the archival author.
Name: Sandra Kopp, MD.
Contribution: This author helped write and collect data for the manuscript.
Attestation: Sandra Kopp approved the final manuscript.
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