Review of unusual patient care experiences is a cornerstone of medical education. Each month, the AQI-AIRS Steering Committee abstracts a patient history submitted to the Anesthesia Incident Reporting System (AIRS) and authors a discussion of the safety and human factors challenges involved. Real-life case histories often include multiple clinical decisions, only some of which can be discussed in the space available. Absence of commentary should not be construed as agreement with the clinical decisions described. Feedback regarding this article can be sent by email to firstname.lastname@example.org. Report incidents or download the AIRS mobile app at www.aqiairs.org.
A 57-year-old woman developed acute right shoulder pain within minutes following intralaminar epidural steroid injection with a 17g blunt-tipped needle at the C7-T1 interspace. The patient was transferred from the pain clinic to a nearby hospital where urgent MRI scan showed an acute epidural hematoma. Urgent surgical decompression was successful, and the patient recovered without incident.
Acute epidural hematoma is one of several very rare, but very serious, complications of anesthesia. Mitigating the risk of permanent harm from such events – turning hits into near-misses – is a critical skill of the mindful anesthesiologist. Whether local anesthetic systemic toxicity, malignant hyperthermia or unexpected anaphylaxis, the ability to quickly recognize life-threatening adverse events and prevent them from doing permanent harm is a key factor in anesthesiology’s position as the safest of all medical specialties.
The incidence of epidural hematoma in the spinal canal is low enough that it can only be estimated – likely no more than a few hundred cases a year in the U.S. What is known about epidural hematoma is almost entirely from case series consisting of small numbers of patients; prospective studies of high-risk cohorts, even those enrolling thousands of patients, have seldom identified even a single event. A metanalysis in 2003 collected 613 cases published over a 170-year period. The most common cause of hematoma in that report was “idiopathic,” followed by patients on anticoagulant therapy and those with identified vascular malformations. The fifth and tenth leading groups were patients who had undergone spinal or epidural procedures, with and without anticoagulant risk factors, respectively. Risk factors commonly found in epidural hematoma cases include use of oral anticoagulants or platelet inhibitors (including aspirin), older age, female sex, history of gastrointestinal bleeding and higher INR values.
A 1994 series identified 61 patients with hematoma after spinal or epidural needle placement. Forty-two (68 percent) had a known hemostatic defect; other risk factors included difficult epidural catheter placement (15 patients), blood noted after catheter placement (15 patients), an indwelling epidural catheter at the time of diagnosis (32 patients) or a recently removed catheter (15 patients). Several patients had multiple risk factors, but chillingly, 8 patients (13 percent) had none at all. Of the 61 patients reported, only 38 percent recovered any neurologic function following diagnosis.
Epidural hematoma can present as unexpected extension or duration of an existing neuraxial block, new onset of neurologic symptoms or – less commonly – new onset of pain. In 2019, diagnosis is typically made by MRI scan. Surgical decompression should occur as soon as possible, as timeliness is associated with improved outcomes.
Because of the catastrophic nature of epidural hematoma, including the potential for life-long paraplegia, most anesthesiologists will avoid epidural or spinal procedures in any patient with a known coagulation defect. From the information reported to AIRS in this case, it seems that no risk factors were present prior to the epidural pain procedure. No mention is made of procedural difficulty or obvious bleeding. The reporter is to be commended for rapid recognition of a very rare complication.
The case presented seems cognitively simple, but a more difficult scenario can be imagined in which the anesthesiologist must weigh a variety of risks and benefits. For example, the postoperative patient with an indwelling epidural catheter who has received a postoperative dose of low-molecular weight heparin. When is it safe to remove the catheter, knowing that this is a risk factor for epidural hematoma? The American Society of Regional Anesthesia and Pain Management has published guidelines on this topic that are widely cited, but it is important to consider the quality of evidence they are working from. Epidural hematoma is a disastrous complication that is known to be associated with anticoagulant therapy, but the actual risk is unquantifiably small – we simply can’t measure it. In real life, this risk must be balanced against other concerns. What are the risks of interrupting postoperative prophylaxis against venous thromboembolism? Postoperative pulmonary embolus is also a serious complication and likely occurs an order of magnitude more commonly than epidural hematoma. The same might be said of the risk of interrupting anti-platelet therapy in a patient with coronary artery disease. And what are the risks of keeping the patient in the hospital when they are otherwise ready for discharge? Hospital-acquired pneumonia is less serious than epidural hematoma but hundreds of times more common.
Moving anesthesiology from the five-sigma to the six-sigma level of safety will require evidence-based minimization of practice variability when a clearly superior course of action can be defined (But not when the evidence is unclear – as noted in previous AIRS articles, clinical variability breeds resilience for our profession.) As safety improves, anesthesiologists will be increasingly required to make decisions in the absence of definitive data on relative risks. Society-sponsored guidelines provide a useful tool for organizing thought, but mindful physicians will know that guideline recommendations cannot be followed blindly. Individualized assessment of risks and benefits – the art of medicine – is likely to remain the most important skill of anesthesiologists for generations to come.