Theories for effectiveness:
(1) hole in dura sealed by blood clot
(2) increased pressure in epidural space reduces CSF leakage
Criteria for use:
(1) failure of conservative therapy with bed rest and adequate hydration
(2) Some authors have had success giving an oral dose of 300 mg caffeine, which may vasoconstrict cerebral blood vessels (Janssens et al)
(3) moderate to severe headache
Technique:
(1) The physician has the patient lie on the side and places a spinal needle in the epidural space. Since the injected blood tends to move cephalad after injection, the patch should be attempted below the previous puncture site.
(2) Blood is collected into a syringe without anticoagulant from the patient's arm or hand. The phlebotomy must be performed only after scrupulous cleansing of the skin surface (better than for a blood culture).
(3) The amount of blood to inject is 15-20 mL in adults. For pediatric patients 0.2 - 0.4 mL per kg body weight of blood may be used (Ylonen and Kokki), but no more than 10-15 mL.
(4) The physician then injects the blood through the spinal needle.
(5) The patient should remain flat for at least 1 hour and preferably 2 hours.
If a first attempt at blood patch fails, a second attempt may be successful. However, it is important to consider alternative causes of headache, especially if the symptoms are atypical in any way.
Failure may occur with:
(1) use of a larger spinal needle during the initial dural puncture
(2) too small a volume of blood injected (less than 10 mL in an adult)
(3) delay between onset of the headache and placement of the blood patch. Ideally the patch should be placed within 1-3 days of headache onset.
(4) early mobilization after the injection
(5) misplacement of the patch (not at or near the site of the leak)
(6) headache due to another cause
Contraindications:
(1) sepsis
(2) local infection at the site of injection
(3) coagulopathy (for epidural puncture)
(4) inability to access the epidural space due to anatomic or operator difficulties
Potential complications:
(1) subdural hematoma (unclear to me if the subdural hematoma may have preceded the epidural blood patch)
(2) meningitis
(3) radicular symptoms (from nerve compression), which may limit the total volume of blood injected during the procedure
Limitations: While some authors are enthusiastic about the method, other authors have had less success with the method. The first patch may be effective in 61-75% of patients (Duffy and Crosby, 1999). Some patients will have initial benefit from the procedure, only to have recurrent headache later.
