An epidural blood patch (EBP) is a procedure in which a small volume of autologous blood is injected into a patients epidural space to stop a leak of cerebrospinal fluid (CSF). This leak of CSF is thought to decrease CSF pressure, particularly when the patient is upright, allowing for increased cerebral blood flow via vasodilation producing a characteristic post-dural puncture headache (PDPH or "a spinal headache"). An alternate theory suggests that loss of CSF pressure, particularly with upright posture, creates traction on the cerebral meninges which is continuos with the vertebral meninges.
PDPHs occur when the dura has been violated. Typically this occurs following a subarachnoid injection (a "spinal"), or from inadvertent puncture of the dura when attempting epidural injection or placement of an epidural catheter. PDPHs can also occur following diagnostic or therapeutic procedures (diagnostic lumbar puncture, lumbar myelogram) or following spinal surgery. EBP is rarely used to treat "spinal" a headache following the creation of a dural rent following spine surgery.
The incidence is less than 1% following subarachnoid block performed with a 25-gauge spinal needle. This increases to nearly 36% when using a 20-gauge or 22-gauge needle for diagnostic lumbar puncture. Following inadvertent puncture of the dura with a 17-gauge epidural needle, the incidence of PDPH is approximately 75% to 80%. Risk factors include needle puncture size, age less than 60 years and female gender. Typical onset is 24 to 48 hours following a puncture. A headache is often described as intense, vise-like in the frontal-occipital region and may be accompanied by cranial nerve symptoms of auditory impairment and/or blurred vision. Pathognomonic for PDPH is an aggravation of symptom in an upright position with relief in a supine position. Left untreated more than 90% of PDPHs are self-limiting and will resolve spontaneously in 7 to 10 days. A prophylactic EBP following an inadvertent dural puncture in parturients for epidural catheter placement has not been shown to decrease the incidence of PDPH.
Although many treatments including bedrest, analgesics, NSAIDs, hydration, intravenous (IV) caffeine, or consumption of caffeinated products have been used, these produce only temporary relief. The definitive treatment is performing an EBP with approximately 85% success rate. EBP may be repeated and is reported to have a 90% success rate. In rare refractory instances, surgical exploration and placement of fat graft may be considered.
The epidural space is bounded by the dural meninges anteriorly, the ligamentum flavum posteriorly and the sides of the vertebral walls laterally. It extends from the foramen magnum to the sacral hiatus. Its contents are tiny arteries and lymphatics, epidural fat, and a network of small valveless veins (Batson's plexus). The epidural "space" is more of a potential space; a series of discontinuous compartments which open up when injected with liquid or air.
Epidural Blood Patch (EBP) is indicated for the treatment of Post-Dural Puncture Headache in people who don't respond to conservative treatment (rest, IV hydration, PO analgesics, IV/PO caffeine) and who will not tolerate the 7-10 days in which most dural puncture headaches resolve.
Contraindications for EBP include anticoagulation/coagulopathy, infection at the injection site, and patient refusal or lack of cooperation.
Equipment required for EBP includes a standard epidural kit and an 18-gauge or 20-gauge angiocatheter from which to draw autologous blood in a sterile fashion. The author prefers to place the catheter and cap it off and saline flush to expedite autologous blood draw once access to the epidural space is achieved.
Although EBP can be performed by a single operator, it usually requires a second operator for a sterile blood draw and, possibly, a third assistant to help with patient positioning.
Following an explanation of the procedure and obtaining informed consent, the patient is placed in a lateral or seated position. A seated position will exacerbate symptoms, and some patients will not tolerate this for more than a few minutes, if at all. The back injection site, either from previous dural puncture or a vertebral interspace one above or below, is sterilely prepped and draped as well as the extremity from which blood is to be drawn.
The epidural space is identified in the standard fashion using loss-of-resistance to air or saline. In particularly difficult instances the use of C-arm radiography or ultrasound guidance may be used. Once the placement of needle tip of the 17-gauge epidural needle is confirmed, approximately 20 mL of autologous blood is drawn from the patient in a sterile fashion. The blood is injected slowly (30 to 60 seconds) to create a blood patch. The introduction of blood into the epidural space may produce discomfort and cramping occasionally limiting the volume of injected blood. Smaller injected volumes will often work in creating a blood patch. Reports have indicated successful EBP for PDPH with as little as 5 mL of autologous blood (range 5 to 25 mL); however, most practitioners will use approximately 20 mL if possible.
The most frequent and problematic complications of EBP include failure (15% to 20%), worsening of PDPH by inadvertently creating additional dural rent(s), back pain and infection. Mild to moderate back pain is commonly reported. This is self-limited, generally resolving in days and preferable to the discomfort of a PDPH. Also, patients need to be made aware of signs and symptoms of infection at the injection site: fever, malaise, erythema, or purulence as injected blood may serve as a nidus for infection. This requires urgent evaluation and care.
As most cases of PDPH's resolve spontaneously within 7 to 10 days, some patients may opt for conservative treatment rather than EBP. These include limiting upright position, hydration, oral analgesics, and intravenous or oral caffeine. Caffeine is a cerebral vasoconstrictor. It is administered as 500 mg sodium caffeine benzoate in 1000 mL of NS or LR over 1 to 2 hours. This, however, generally produces short-term relief. A patient who chooses conservative therapy should keep well hydrated and consume caffeine-containing beverages and oral analgesics as necessary at home.
The majority of patients who elect to have EBP are those that cannot minimize activity, for example, recent parturients with newborns or younger patients. Also, those patients that are extremely symptomatic (some cephalgia even when supine and cannot tolerate any degree of upright positioning, tearful or crying at rest, photophobia) will likely consent to EBP with or without conservative treatment.
It is important to keep in mind that not all headaches, even if the patient is a post-dural puncture, are PDPHs, and this must be considered in the work-up before performing EBP. Furthermore, in mildly symptomatic patients, for example, mild cephalgia when standing 15 to 20 minutes will spontaneously resolve with conservative therapy, and may be preferable to risking a second, large bore (17-gauge) dural puncture, back pain, and the possibility of infection.
An epidural blood patch is a highly effective way to treat a specific subset of post-dural puncture headache patients. It is an elective procedure that carries a relatively low degree of risk.