Physician anesthesiologist at Stanford at Associated Anesthesiologists Medical Group
Richard Novak, MD is a Stanford physician board certified in anesthesiology and internal medicine.Dr. Novak is an Adjunct Clinical Professor in the Department of Anesthesiology, Perioperative and Pain Medicine at Stanford University, the Medical Director at Waverley Surgery Center in Palo Alto, California, and a member of the Associated Anesthesiologists Medical Group in Palo Alto, California.

Clinical Case for Discussion regarding postoperative anticoagulation: You’re scheduled to anesthetize a 58-year-old, 80 kg male for a left total knee replacement. You utilize the current multimodal strategies for operating room anesthesia and postoperative pain reduction, including an ultrasound-guided adductor canal block with 0.5% ropivicaine, a spinal anesthetic (using a pencil-tipped 25-gauge Quincke needle) of 1.5 mls of 0.75% bupivicaine plus 25 µg of fentanyl and .300 mg of morphine, and a light general anesthetic using 1-1.5% sevoflurane and an intravenous propofol infusion, with an LMA for airway management. The patient does well, and is discharged from the Post Anesthesia Care Unit in excellent condition.


On postoperative day #1 the surgeon contacts you and says that the patient has a severe frontal headache whenever sitting up in bed or attempting to stand. The headache disappears when the patient lies down.

What do you do?


You visit the orthopedic ward to interview the patient. As described, his headache symptoms are postural and severe whenever he sits up or stands. There are no other neurological symptoms or findings. The patient is doing well regarding control of his knee pain, and both the physical therapist and the surgeon are eager to initiate ambulation.

You make a diagnosis of post-dural puncture spinal headache. You discuss the diagnosis and the treatment options with the patient. You tell him the simplest course is to remain recumbent for several days to give the dural puncture a chance to heal. The patient objects. He wants to get out of bed, walk as much as possible, and go home from the hospital as soon as he can. You discuss the procedure of a blood patch and he says, “Yes, that’s what I need. Let’s do it.”

The epidural blood patch was introduced by Gormley in 1960,1 and requires a repeat epidural needle placement with injection of a volume of autologous blood into the epidural space near the level of the subarachnoid leak. Szeinfeld demonstrated that an injected volume of 15 ml of blood will spread over a mean distance of nine spinal segments, and that the spread was preferentially cephalad.2 He recommended performing the blood patch at or caudad to the level of the previous dural puncture. A randomized multinational trial suggests that 20 ml of autologous blood is a reasonable volume to inject.3

You explain the blood patch procedure and its risks to the patient, he signs a consent, and you perform the blood patch within the hour. You position the patient on his side, prep his back with Betadine, and insert an 18-gauge Tuohy needle in the L3-L4 interspace where you inserted the spinal injection the day before. You advance the needle and easily locate the epidural space by loss of resistance. At this point you move to his left arm, prep the skin with Betadine, and in a sterile fashion withdraw 20 ml of the patient’s blood into a syringe. You then attach the syringe to the epidural needle and inject the patient’s blood into his epidural space, with the planned expectation of clotting off the dural leak from yesterday’s spinal puncture. You withdraw the Tuohy needle and announce to the patient that the procedure is over. After a ten minute wait, you ask the patient to sit up. He does, and with a smile announces that he has no headache. The physical therapist arrives, and helps the patient to stand. They walk out of the hospital room together, and the patient, still headache free, looks back over his shoulder to you and says, “Thanks, Doc. You’re the greatest.”

A fine story, correct?

It would seem so, until 2 a.m. that night when the orthopedic surgeon phones you. The patient began complaining of numbness and weakness in his right leg, the contralateral leg to the knee which was replaced. You drive to the hospital to find the patient has already had a stat MRI of his spine, and the diagnosis was a perispinal hematoma at L3. Neurosurgeons have taken him to the operating room to drain the hematoma and decompress the spinal column.

One week later, the patient still has significant weakness and numbness in his right leg. His headache is gone, but he’s angry as hell. He believes his neurosurgical procedure and his weak right leg have something to do with his anesthesiologist.

He’s right. What happened?

You didn’t read the patient’s chart on post-op day #1 after his knee replacement, that’s what happened.

The standard of care after total joint replacement has long been to administer anticoagulant prophylaxis against venous thromboembolism (VTE). Which anticoagulants are used? A meta-analysis looked at sixteen randomized controlled trials, and compared low-molecular weight heparin (enoxaparin/Lovenox) with the newer anticoagulants rivaroxaban, dabigatran, and apixaban.4 The study concluded that the rivaroxaban, dabigatran, and apixaban are higher in efficacy, but have a higher risk of bleeding than enoxaparin. Your patient was receiving enoxaparin 30 mg SQ every 12 hours, initiated on his arrival to his orthopedic ward room after his total knee replacement. His most recent dose was 3 hours before you inserted the 18-gauge needle into his lumbar spine.

The Black Box warning for enoxaparin (Lovenox) reads:

Important Safety Information for LOVENOX® 


Epidural or spinal hematomas may occur in patients who are anticoagulated with low molecular weight heparins (LMWH) or heparinoids and are receiving neuraxial anesthesia or undergoing spinal puncture. These hematomas may result in long-term or permanent paralysis. Consider these risks when scheduling patients for spinal procedures.

How can an anesthesiologist make such an error? It can happen, and it’s not that difficult in some hospital systems. Selected electronic medical records (EMRs) have a Chart Review screen which contains multiple tabs, each tab listing pertinent information. There are separate tabs for physician notes, consultations, laboratory reports, ECG reports, radiology reports, media, medications, allergies, and anesthesia records. If you review one or two of these tabs but don’t view the medications tab, you can miss the fact that a significant medication was added. Regardless of the method of the medical recordkeeping, unless there is a specific warning on the chart that a patient is receiving anticoagulant medications, you could proceed with an invasive procedure without awareness of that medication. Introduction of a needle into the vicinity of the spinal cord in an anticoagulated patient runs a high risk of a hematoma, and such a hematoma can cause a permanent neurologic deficit to the lower extremities.

What about a Time Out procedure? Did you call a Time Out prior to your blood patch? Current Universal Protocol requires us to call a Time Out prior to every surgery and every invasive procedure, so the physician(s) and nurse(s) can review all the pertinent information for that patient and that planned procedure. The Joint Commission requires the Time Out to include confirmation of the correct patient, correct side and site, agreement on the procedure to be performed, correct patient position, and availability of needed equipment/supplies/implants. Many institutions include broader patient safety practices into the Time Out, including a list of pertinent medical problems, and pertinent pharmacology, such as the presence or absence of thromboembolism prophylaxis.

How and when should this patient’s epidural blood patch have been done? A well-informed anesthesiologist, properly aware of the anticoagulation medication, chooses to time his blood patch per the accepted guidelines for enoxaparin. He waits until 12 hours have passed since the last dose of enoxaparin, performs the epidural blood patch at hour 13, and then has the next dose of enoxaparin delayed for at least 4 hours after the epidural blood patch. Because communication is important, the anesthesiologist also contacts the attending orthopedic surgeon and discusses his intended plan. After concurrence with the surgeon, the anesthesiologist proceeds. The headache is relieved, and no epidural hematoma occurs.

The FDA recommends that “health care professionals and institutions involved in performing spinal/epidural anesthesia or spinal punctures should determine, as part of a pre-procedure checklist, whether a patient is receiving anticoagulants and identify the appropriate timing of enoxaparin dosing in relation to catheter placement or removal. To reduce the potential risk of bleeding, consider both the dose and the elimination half-life of the anticoagulant:

  • For enoxaparin, placement or removal of a spinal catheter should be delayed for at least 12 hours after administration of prophylactic doses, such as those used for prevention of deep vein thrombosis. Longer delays (24 hours) are appropriate to consider for patients receiving higher therapeutic doses of enoxaparin (1 mg/kg twice daily or 1.5 mg/kg once daily).
  • A postprocedure dose of enoxaparin should usually be given no sooner than 4 hours after catheter removal.
  • In all cases, a benefit-risk assessment should consider both the risk for thrombosis and the risk for bleeding in the context of the procedure and patient risk factors.”5

The same FDA document states: “Health care professionals and institutions involved in performing spinal/epidural anesthesia or spinal punctures should determine, as part of a preprocedure checklist, whether a patient is receiving anticoagulants and identify the appropriate timing of enoxaparin or other anticoagulant dosing in relation to catheter placement/removal.”

What are the lessons learned from this Case Discussion?

  1. Read all pertinent parts of your patient’s chart. This will require thorough knowledge of your hospital’s EMR to guarantee a comprehensive review, but that’s your job. If it’s in your patient’s medical record, and it’s both relevant and important, you need to know it.
  2. Do a checklist /Time Out before every spinal invasive procedure, and listen to and trust your nursing colleagues. If the nurses are administering an anticoagulant such as enoxaparin, they will be aware of that fact.
  3. An institutional policy requiring prominent documentation and labeling in the chart or at the bedside for all patients on pharmacological VTE prophylaxis may be an indicated and wise policy. I recommend your hospital considers adding a medical records warning system that identifies when a patient is on an anticoagulant, be it enoxaparin, Coumadin, or the newer anticoagulant drugs rivaroxaban, dabigatran, or apixaban. If even one anticoagulated patient is spared an iatrogenic spinal hematoma, the policy will be worth it.

Goals of include helping keep your patients safe, preventing you from being sued, and helping you stay out of the courtroom. Be smart and be safe. Learn from other’s mistakes, learn from quality assurance committees and meetings, and learn from the Case Discussions you’ll find on this website.


  1. Gormley JB: Treatment of postspinal headache. Anesthesiology 1960; 21: p. 565.
  2. Szeinfeld M, Ihmeidan IH, Moser MM, et al: Epidural blood patch: evaluation of the volume and spread of blood injected into the epidural space. Anesthesiology 1986; 64: pp. 820-822.
  3. Paech MJ, Doherty DA, Christmas T, and Wong CA: Epidural Blood Patch Trial Group. The volume of blood for epidural blood patch in obstetrics: a randomized, blinded clinical trial. Anesth Analg 2011; 113: pp. 126-133.
  4. Outes GA, Fernandez AIT, Gea LS, Castrillon EV: Dabigatran, rivaroxaban, or apixaban vs enoxaparin for thromboprophylaxis after total hip or knee replacement: systematic review, meta-analysis, and indirect treatment comparison. BMJ. 2012;344:e3675.
  5. FDA Drug Safety Communication: Updated recommendations to decrease risk of spinal column bleeding and paralysis in patients on low molecular weight heparins.


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