AnesthesiaWeb - Lit Reviews- Epidural hematoma following epidural analgesia in a patent receiving unfractionated heparin for thromboprophylaxis

July 2000

Epidural hematoma following epidural analgesia in a patent receiving unfractionated heparin for thromboprophylaxis.
Sandhu H, Morley-Foster P, Spadafora S. Regional Anesthesia & Pain Medicine. 25 (1): 72-5, 2000

Commentary by Peter Dwane, M.D.

[see abstract below]

Low Dose Heparin and Neuraxial Block

In their recent paper, Sandhu et al. note that risk factors for hematoma formation after epidural anesthesia include coagulopathies (congenital and acquired), ankylosing spondylitis, traumatic epidural insertion, old age, and epidural catheter manipulation while anticoagulated. The risk of epidural hematoma in the absence of heparin is estimated to be 1:150,000.

Following generally accepted recommendations at the time, the epidural catheter was placed two hours after the initial dose of 5000U of standard, unfractionated heparin for thromboprophylaxis. However, this timing coincides with the peak effect of this common heparin regime, and current American Society of Regional Anesthesia (ASRA) guidelines now recommend delaying subcutaneous heparin until one hour after neuraxial block placement. These new guidelines go on to suggest that catheter removal occurs one hour prior to the next planned dose of standard heparin, or 2-4 hours after the last given dose of standard heparin. Although there was a delay of almost 24 hours of recognizing the presence of aberrant leg weakness, this patient fortunately had a good outcome after her subsequent decompression laminectomy for epidural hematoma. The author cautions that unexpected sensory/motor symptoms, with or without back pain, are crucial markers that must trigger the immediate search for, and removal of, an epidural hematoma.

Liu et al., [1] in a significant review of standard (unfractionated) heparin and neuroaxial block note that the drug's half life (T1/2) is both dose- and molecular-size dependant; and increases disproportionately with increasing dose.

Heparin dose	T1/2 IV Heparin
25 u/kg	30 min
100 u/kg	60 min
400 u/kg	150 min

The administration of low dose (5000 u) subcutaneous [sc.] Heparin q12h for deep venous thromboprophylaxis usually does not elevate the aPTT. But this result can be unpredictable, and 15% of patients can develop an elevated aPTT, which is usually less than 1.5 times the normal level. In addition 2-4% patients achieve an aPTT that is in the therapeutic range. In spite of this, there are several published series, totaling over 9,000 patients who received mini-dose heparin prophylaxis without developing spinal hematomas. And, like Sandhu, many anesthesiologists believe that this therapy does not contraindicate neuraxial block, but the risk of hematoma may be reduced by delaying the initiation of heparin therapy until after the block.

Horlocker [2], in a review article in a new journal, also examines neuraxial anesthesia and anticoagulation, including the use of standard heparin. I mention this journal because, like Survey of Anesthesiology, it attempts to summarize current anesthesia knowledge for busy anesthesiologists. Instead of selected abstracts, Current Anesthesiology Reports presents several review articles, covering two major areas of anesthesia, in each of its 6 bimonthly issues.

On the topic of neuraxial anesthesia and anticoagulants, 1998 was a banner year for review articles on specific classes of drugs, many of which appeared in the last issue of the ASRA journal that year. In addition to Liu's article, Horlocker [3] examined low molecular weight heparin (LMWH) while Enneking [4] reviewed oral anticoagulants and Urmey [5] antiplatelet drugs in separate articles, which contained the appropriate ASRA recommendations.