Performed since 1960 for PDPS, the epidural blood patch (EBP) has also been successfully used in the treatment of spontaneous intracra-nial hypotension and postlaminectomy leaks. The mechanism of action is likely due to the thrombotic plug patching the hole or a rent in the dura as well as the generation of increased pressure in the epidural space.
It has been reported that up to 60% of patients with postdural puncture headache recover spontaneously, with symptoms rarely lasting more than a week. Patients with persistent or severe headache may be relieved by EBP. Cure rates of 85 to 98% have been reported. In a large study of 504 patients, 75% had complete relief, 18% had incomplete relief, and only 7% were considered failures.15 Repeat EBP is more common after inadvertent dural puncture with a Tuohy needle than with smaller gauge spinal needles. There are no controlled studies evaluating the efficacy of epidural blood patch to the author's knowledge. For these reasons, rules for determining when to perform the EBP are not clearly defined in the literature. Some authors perform EBP in as little as 24 hours after a dural puncture in a symptomatic patient; others recommend up to 3 weeks of conservative therapy.16 For a patient with cranial nerve palsy or auditory disturbance, it is probably preferable to perform the epidural blood patch sooner rather than later owing to the potential risk of ischemic damage to the cranial nerves. Also, one must consider the severity of the patient's symptoms and whether earlier treatment might facilitate that patient's return to work and/or normal daily activities.
Once an epidural blood patch has been administered for PDPS, relief of symptoms may be almost immediate. Anecdotally, some patients may report relief of their headache even while the injection is being performed. Most patients with hearing loss secondary to CSF hypo-volemia will demonstrate significant improvement in hearing within an hour, as demonstrated on audiometric testing.17 An in vitro study in a canine model showed that the coagulation time of autologous blood was accelerated when the blood was mixed with CSF. It was suggested that CSF accelerates the coagulation cascade.18 The acceleration of the coagulation cascade might explain why the epidural blood patch may invoke such a rapid response. Another proposed reason for the rapid response is that the injected volume raises the pressure in the epidural and subarachnoid space, forcing CSF back inside the cranium. In vivo pressure measurements during epidural injection support this theory.19 Potential contraindications to EBP include presence of intracerebral subdural hematoma. There is a case report of a patient with SIH who developed so significant an increase in subdural hematoma after an epidural blood patch that surgical decompression was required.20 The epidural blood patch is contraindicated when sepsis or leukemia are present, to avoid the theoretical risk of seeding infection or malignancy into the neuroaxis. Other contraindications include severe coagulopa-thy or a patient who is a Jehovah's Witness. Relative contraindications include HIV infection and severe anemia. Patients infected with HIV have been treated with autologous EBP with no reports of subsequent HIV-related infections of the central nervous system in a 2-year follow-up period. Epidural blood patches have been performed in children and do not appear to be contraindicated in the proper clinical setting. Previous EBP is not thought to be a contraindication to subsequent epidural anesthesia.
The risks of EBP are low, but reported complications including sepsis, transient facial paralysis, exacerbation of postdural puncture symptoms, seizure, encephalopathy, arachnoiditis, and transient brachycar-dia. Intrathecal and subdural hematoma have been described. Transient backache or radiculopathy has been reported in patients receiving a lumbar blood patch. Acute meningeal irritative reaction has also been described. Some of these symptoms might be attributed to inadvertent subarachnoid or subdural injections of blood. Image-guided EBP with epidurography is believed to be more accurate and likely to have a lower complication rate than blind EBP. In general, fluoroscopically guided spinal injections are more accurate than blind injections, and the use of image guidance is advocated for EBP if feasible. It has been demonstrated in the literature that blind epidural injections are highly inaccurate. Twenty-five percent of non-image-guided, attempted epidural injections were shown to be not epidural in location when checked under fluoroscopy.21 A recent large study has demonstrated that fluoroscopically guided epidural steroid injections are highly accurate, and the associated complication rate is very low.22
Other alternative treatments for CSF hypovolemia include bed rest, intravenous fluid hydration, epidural dextran or saline injection, continuous infusion of dextran through an epidural catheter, and oral or intravenous caffeine infusion. Intravenous caffeine sodium benzoate (500 mg) in 1 liter of fluid over 90 minutes may provide immediate relief, though symptoms may recur. Caffeine may alleviate symptoms via its vasoconstrictive properties or by decreasing cerebral blood flow, increasing cerebral vascular resistance, and increasing CSF production. Other pharmacotherapeutic agents that have been described for treatment of CSF hypoglycemia include steroids and subcutaneous sum-itriptan. A bolus of saline or dextran (10-30 mL) may provide a tamponade effect and is an alternative treatment for a septic patient or a Jehovah's Witness. In patients lacking venous access for withdrawal of autologous blood, a fibrin patch might be an alternative. The fibrin patch is described in another section of this chapter.
A prophylactic epidural blood patch has been described in the literature, with some authors advocating its use in some situations. However, the overall literature shows no definite benefit when this procedure is performed on a routine basis in patients undergoing spinal anesthesia or lumbar puncture for other reasons.
When MRI has been performed on patients who have undergone epidural blood patch, the epidural blood has been seen consistently 45 minutes afterward and may be seen up to 18 hours postinjection.23
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Are Headaches Taking Your Life Hostage and Preventing You From Living to Your Fullest Potential? Are you tired of being given the run around by doctors who tell you that your headaches or migraines are psychological or that they have no cause that can be treated? Are you sick of calling in sick because you woke up with a headache so bad that you can barely think or see straight?