Grant Weicht, MD, contributor
A 70 year-old woman was admitted to Harborview Medical Center after sustaining injuries in a high-speed motor vehicle accident. She was the restrained front-seat passenger in a "T-bone" collision which impacted the passenger side of her vehicle. Except for diffuse contusions and abrasions her only injuries consisted of a right-sided hemo-pneumothorax and fractures of the second through eighth ribs. She underwent right chest tube thoracostomy in the emergency room.
On the morning after admission the Pain Relief Service was consulted for management of pain related to her thoracic injuries. Parenteral morphine administered on a PRN basis over the previous night provided inadequate analgesia and resulted in excessive sedation. The patient's oxygen saturation on nasal cannula oxygen at 4L/min flow was 94%, and occasional desaturation to the upper 80s occurred with movement. She exhibited splinting with inspiration and was unwilling to cough due to chest pain.
In light of her deteriorating pulmonary function and localized site of injury, placement of a thoracic epidural catheter for continuous analgesia was planned. Recent coagulation studies including protime, international normalized ratio, partial thromboplastin time, and platelet count were normal.
An epidural catheter was placed at the T7-T8 interspace using the paramedian approach and loss of resistance technique. An 18-gauge Tuohy needle was redirected 6-7 times to "walk off" the lamina, but placement of the needle into the epidural space was atraumatic. A 20-gauge epidural catheter threaded easily. Four milliliters of 2% lidocaine with epinephrine were then administered and a T3-T8 bilateral block resulted with effective analgesia.
It was then noted that the patient had received enoxaparin 30 mg subcutaneously at 9 o'clock, 6 hours prior to epidural catheter placement.
1. How does enoxaparin (a low molecular weight heparin) differ from unfractionated heparin?
2. What laboratory tests reflect the anticoagulant activity of enoxaparin?
3. What is the risk of epidural hematoma following neuraxial blockade in patients who have recently received enoxaparin for thromboprophylaxis?
4. What would be the clinical signs of epidural hematoma in a patient who is receiving an infusion of local anesthetic or opioid through an epidural catheter?
5. What is the management of a suspected epidural hematoma?
6. How long should one wait following a dose of enoxaparin for thromboprophylaxis to initiate neuraxial blockade?
7. How long should one wait following placement of an epidural catheter to restart thromboprophylaxis with enoxaparin?
8. How long should one wait following a dose of enoxaparin for thromboprophylaxis to remove an epidural catheter?
FDA Public Health Advisory, December 15, 1997
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