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[edit] An epidural blood patch

refers to the injection of a small volume of autologous blood into the epidural space of the vertebral column.

The vertebral column, an elaborate structure of bony vertebral bodies, houses and protects the spinal cord, nerve roots, and various structures within its spinal canal. The spinal cord is covered by a fine membrane called the 'pia mater' and extends from the foramen magnum at the base of the skull to the L1 vertebral body. The spinal cord and nerve roots are bathed in cerebrospinal fluid (CSF), within a 'sac.' The outer covering of this sac is called the 'arachnoid mater'. In turn, another thick membrane covers the arachnoid mater and is termed the 'dura mater'. This sac is loosely termed the 'spinal sac' although anatomically, it is called the 'subarachnoid space'. The subarachnoid space and CSF communicates with an elaborate circulation that extends rostrally up the brain. Termed the 'fourth circulation,' CSF circulates actively through the central nervous system.

External to the subarachnoid space exists another space, the 'epidural' or 'extradural' space, since it is outside the dura mater. (Figure 1) Of interest, there is another space, termed the 'subdural space' between dura mater and arachnoid mater. The epidural space is not as well-defined as the subarachnoid space, since it is a potential space containing blood vessels, fatty tissue, small slivets of fascia and lymphatics, through which nerve roots pass. Pressure within the lumbar epidural space may be sub-atmospheric. The epidural space extends from the base of the skull all the way down to the sacral bone, where it is referred to as the 'caudal canal'. The epidural space varies in size depending on the size of the spinal cord. The outer landmark of the epidural space is a thick, yellow, ligamentous structure termed the 'Ligamentum flavum'.

[edit] Why is it done?

The CSF can yield diagnostic information about a variety of conditions; in turn, obtaining a sample of this fluid assists physicians with various diagnostic and therapeutic challenges. A diagnostic lumbar puncture, called a 'spinal tap', is performed by placing a needle via the L3/4 or L4/5 vertebral interspace into the subarachnoid space, where pressure may be measured and fluid removed. 'Neuraxial anesthesia' is the term used to describe the use of regional anesthetic techniques in the cervical, thoracic, lumbar, and caudal regions of the vertebral column. 'Spinal anesthesia' refers to the administration of a local anesthetic substance into the subarachnoid space. Typically, this is injected via the interspace between the L3/4 or L4/5 vertebra; since the spinal cord ends at L2, this technique will ensure that direct injury to the spinal cord by the needle is reduced.

The epidural technique places the anesthetic in the epidural space, either as a 'single shot' or via a catheter, and can be utilized during labor, surgical procedures, or as treatment (epidural steroids or hypertonic saline) for back pain. If an epidural catheter is placed, the needle used is much larger than spinal anesthetic needles; i.e. 17g vs. 20g. The epidural space can be entered at any level of the vertebral column. Location of the space requires considerable finesse and various techniques are used, such as the 'loss-of-resistance' and 'hanging-drop' methods.

Myeolography is a technique where a radiologist injects a radiocontrast dye via a needle into the subarachnoid space, in order to outline structures in the spinal canal and vertebral column (this technique has been largely superceded by more modern tomographic techniques.) Any technique that penetrates the dura mater will potentially create a leak of CSF out of the subarachnoid space into the epidural space. ^[1] Small 'holes', such as those that occur during administering spinal anesthesia with a small (23g) needle, which is tapered and non-cutting, will typically seal quite rapidly; whereas, larger 'holes' in the dura are associated with a greater likelihood of CSF leakage and non-sealage. ^[2]

As CSF leaks out of the subarachnoid space, structures within the cranium(skull) gradually shift downwards. This mechanism stretches sensitive fascial and ligamentous structures, that are attached to cerebral tissue, and dilates cerebral vessels; thus, producing a typical postural headache. ^{[3] [4]}Termed "Post-Dural Puncture Headache," (PDPH) it is characterized by headache that dissipates while supine, but reoccurs when upright. ^{[5] [6]} Other symptoms include neck stiffness and pain across the upper back. Although the headache itself is harmless, it can be very severe and very debilitating. Pregnant mothers receiving epidural anesthesia may inadvertently develop PDPH if the dural sac is punctured by either the needle used to locate the space or by the catheter. Most cases of PDPH are short-lived, resolving within 24 hours. However, when persisting for more than 24-36 hours, additional measures are needed.

Treatments may be conservative or interventional;

[edit] Conservative Methods

1. Bedrest - Since the symptoms of PDPH are alleviated by assuming the horizontal position, keeping a patient horizontal for a period of time (eg. 24 hours) after an intervention is thought to enable spontaneous closure of the dural 'hole.'^[7] Unfortunately, it rarely works.
2. Hydration - Normal hydration of the patient should be maintained. Extra hydration is thought to facilitate increased CSF production. This, too, rarely works.
3. Analgesics - Narcotic analgesics and, in some instances, non-steroidal anti-inflammatory agents are often administered for symptomatic treatment of the headache. Other agents that have been used include; ACTH, theophylline, vasopressin, and sumatriptan.^{[8] [9] [10]}
4. Caffeine - Caffeine has been suggested as a mode of therapy to help constrict the vasodilated cerebral vessels. It is best administered early in the day so that the patient can sleep at night. The dose of caffeine sodium benzoate is 500 mg intravenously which can be repeated once; two hours later, if the first dose does not have the desired effect. ^{[11] [12] [13]}
5. Epidural saline injection - Boluses or infusions of epidural normal saline can help to transiently increase the epidural pressure; thus, slowing the speed at which CSF leaks through the dural hole. This may facilitate spontaneous closure of the dural 'hole.' The bolus dose is 30-60 mls given every 6 hours for 4 doses. The rate of infusion is 1000 mls administered over a 24 hour period.^{[14] [15]}

[edit] Interventional Methods

If conservative measures are ineffective in ameliorating PDPH, one specific intervention that has a long track record of safety and efficacy, is the epidural blood patch.

Introduced in 1960 by Gormley, ^[16] the epidural blood patch consists of injecting 5-20 mLs og autologous blood into the epidural space, in the region of the suspected dural 'hole.' Once the epidural space is located by the anesthesiologist, autologous blood is typically drawn from an in-dwelling intravenous (IV) line, and then injected as a bolus into the epidural space. In 90% of cases, the response is positive and immediate. Subsequently, long-term relief of PDPH occurs in the majority of cases. ^{[17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27]}

[edit] How is it done?

Typically, the patient lies on their side with their legs flexed and drawn up against the chest, in order to open the intervertebral spaces. An IV access port or line is placed in the uppermost extremity - for eg, for a patient lying on the right side, i.e. right lateral decibitus, the IV would be placed in the left or upper extremity.

There are two basic approaches to this technique;

1. Non-contiguous. The needle in the epidural space and the indwelling IV catheter are independent of each other.
2. Closed-circuit. Contiguity of the source of autologous blood and the epidural space is maintained as an 'closed' or unbroken circuit.

For both techniques, sterility must be maintained at all times. For the non-contiguous approach, once the epidural space has been located by the epidural needle, blood is withdrawn from the IV line into a syringe. It is then disconnected from the IV line port and reconnected to the epidural needle. Autologous blood is then slowly injected, 5 - 20 mLs may be used, until there is enough to cover the suspected 'hole' in the dura. This usually is 5-7 spinal segments. Although the optimal volume for the blood patch has been actively debated, 15 mLs is the recommended volume. However, during injection of blood, if the patient complains of backache, leg pain, or other neurologic symptoms, the injection must stop. ^{[28] [29]}

For the closed-circuit technique, both the IV catheter and the epidural needle are setup as a continuous circuit, so that when blood is drawn from the IV catheter, it stays within a closed-circuit, and may be injected from that closed-circuit into the epidural space. This technique is suitable for some patients who object to blood leaving the body, such as Jehovah's Witnesses.

The following is one suggested approach for the Closed-Circuit Epidural Blood Patch technique. Embedded figures demonstrate the "in vitro" component assemble, saline priming and blood injection techniques.

[edit] Closed-Circuit Epidural Blood Patch Technique

Step 1 - Component Assembly Assemble the various components needed for the procedure. This includes an 18g or 16g IV catheter, needleless injection port, low-volume tubing, stopcock, male-to-male connector, syringes, saline flush and epidural anesthesia tray.	Step 2 - Saline Prime Place an IV catheter in the upper most extremity - ensure that blood may be freely drawn from this catheter. Connect tubing to needleless port and stopcock; connect tubing to male-to-male connector and stopcock. Via stopcock, prime tubing with saline to remove air and bubbles. Connect needleless port to IV catheter and flush.
Step 3 - Needle Placement Place epidural needle within the desired epidural space. Once the epidural space has been located, connect saline-primed tubing ensemble to epidural needle and flush.	Step 4 - Autologous Blood Collection Draw 10-20 mLs blood from IV catheter into syringe via stopcock.
Step 5 - Autologous Blood Injection Close stopcock to the IV catheter, open to the epidural needle. Slowly inject 10-20 mLs blood via saline primed tubing and epidural needle into the epidural space.	Step 6 - Completion of Procedure View Enlarged Remove epidural needle. Detach tubing from IV catheter and discard tubing ensemble. Turn patient supine and observe for 30 minutes.

[edit] When should EBP be used?

This decision should be based upon the severity of symptoms, the response to conservative measures, and the need to have the patient ambulate or be discharged. Initially, conservative measures are attempted for 24 -48 hours. Since the epidural blood patch is an invasive technique, it should be discussed in detail with the patient and then decided upon after a review of all the various alternatives. 'Prophylactic blood patch' refers to the situation where the blood patch is performed in close temporal relation to the actual dural 'hole' formation. For example, it might be performed at the time an epidural is performed, during which dural entry has occurred, thus allowing for blood to be injected through the same needle. Alternatively, blood could be injected via an indwelling epidural catheter, prior to removal of the catheter, if the patient symptoms warrant this. (Figures 2, 3) However, both of these approaches would employ a non-contiguous technique. Unfortunately, the efficacy of prophylactic epidural blood patch in documented cases of dural puncture appears significantly less than the delayed symptom-driven epidural blood patch technique.^[30]

Catheter Figure 2

Prophylactic Blood Patch View Enlarged Figure 3 - Prophylactic blood patch via epidural catheter

[edit] See also

• Patients Who Refuse Blood Transfusions - FAQs : Epidural Blood Patch
• NoBlood Forum discussion: Blood Patch

[edit] References

1. ? Glass PM, Kennedy WF (1972), "Headache following Subarachnoid Puncture: Treatment with Epidural Blood Patch.", JAMA, no. 219:, pp. 203-204
2. ? Colonna-Romano P, Shapiro BE (1989), "Unintentional Dural Puncture and Prophylactic Epidural Blood Patch in Obstetrics", Anesth Analg, no. 69:, pp. 522
3. ? Benhamou D, Hamza J, Ducot B (1995), "Postpartum headache after epidural analgesia without dural puncture.", Int J Obstet Anesth, no. 4, pp. 17-20
4. ? Jones R J (1974), "The role of recumbency in the prevention and treatment of postspinal headache.", Anesthesia and Analgesia, no. 53, pp. 788-796
5. ? Ostheimer GW (1979), "Headache in the Postpartum Period in Clinical Management of Mother and Newborn (Eds. Marx GF)", Springer-Verlag, New York, pp. 27-41
6. ? Choi PT, Galinski SE, Takeuchi L, et al (2003), "PDPH is a common complication of neuraxial blockade in parturients. A meta-analysis of obstetrical studies.", Can J Anaesth, no. 50, pp. 460-469
7. ? 4
8. ? Schwalbe SS, Schiffmiller WM, Marx GF (1991), "Theophylline for postdural puncture headache [abstract].", Anesthesiology, no. 75, pp. A1082
9. ? Hodgson C, Roitberg HA (1997), "The use of sumatriptan in the treatment of postdural puncture headache.", Anaesthesia, no. 52, pp. 808
10. ? Kshatri AM, Foster PA (1997), "ACTH infusion as a novel treatment for postdural puncture headache.", Reg Anesth, no. 22, pp. 432-434
11. ? Camann WR, Murray RS, Mushlin PS, et al (1990), "Effects of oral caffeine on postdural puncture headache A double-blind placebo-controlled trial.", Anesth Analg, no. 70, pp. 181-184
12. ? Yucel A, Ozyalcin S, Talu GK, et al (1999), "Intravenous administration of caffeine sodium benzoate for postdural puncture headache.", Reg Anesth Pain Med, no. 24, pp. 51-54
13. ? Sechzer PH (1979), "Post-spinal anesthesia headache treated with caffeine. Part II Intracranial vascular distension, a key factor.", Current Therapeutic Research, no. 26, pp. 440-448
14. ? Usubiaga JE (1967), "Effect of saline injections on epidural and subarachnoid space pressures and relation to postspinal anesthesia headache.", Anesthesia and Analgesia, no. 46, pp. 293-296
15. ? Bart AJ (1978), "Comparison of epidural saline placement and epidural blood placement in the treatment of post-lumbar-puncture headache.", Anesthesiology, no. 48, pp. 221-223
16. ? Gormley JB (1960), "Treatment of postspinal headache.", Anesthesiology, no. 21, pp. 565
17. ? DiGiovanni A J, Galbert MW, Wahle WM (), "Epidural Injection of Autologous Blood for Postlumbar-puncture Headache.", Anesth Analg, no. 51, pp. 226-232
18. ? Palahnuik R J, Cumming M (1979), "Prophylactic Blood Patch Does Not Prevent Postlumbar Puncture Headache.", Can Anaesth Soc J, no. 26, pp. 132-133
19. ? Looser EA, Hill GE, Bennett GM, et al (1978), "Time Versus Success Rate for Epidural Blood Patch.", Anesthesiol, no. 49, pp. 147-148
20. ? Abouleish E, de la Vega S, Blendinger L, et al (1975), "Long-term Follow-up Epidural Blood Patch.", Anesth Analg, no. 54, pp. 459-463
21. ? Ostheimer GW, Palahnuik RJ, Shnider SM. (1974), "Epidural Blood Patch for Post-Lumbar Puncture Headache.", Anesthesiol, no. 41, pp. 307-308
22. ? Crawford JS (1980), "Experience with Epidural Blood Patch.", Anaes, no. 35, pp. 513-515
23. ? Safa-Tisseront V, Thormann F, Malassine P, et al (2001), "Effectiveness of epidural blood patch in the management of post-dural puncture headache.", Anesthesiology, no. 95, pp. 334-339
24. ? Taivaninen T, Pitkanen M, Touminen M, et al (1993), "Efficacy of epidural blood patch for postdural puncture headache.", Acta Anaesthesiol Scand, no. 37, pp. 702-705
25. ? Carrie LES (1993), "Postdural Puncture Headache and Extradural Blood Patch.", Anaes, no. 71, pp. 179-181
26. ? Rosenberg PH, Heavner JE (1985), "An In-Vitro Study of the Effect of Epidural Blood Patch on Leakage through a Dural Puncture.", Anesth Analg, no. 64, pp. 501-504
27. ? Safa-Tisseront V, Thormann F, Mallassine P, et al (2001), "Effectiveness of epidural blood patch in the management of PDPH.", Anesthesiology, no. 95, pp. 334-339
28. ? Coombs DW, Hooper D (1979), "Subarachnoid pressure with epidural blood patch.", Reg Anesth, no. 4, pp. 3-6
29. ? Szeinfeld M, Ihmeidan IH, Moser MM, et al (1986), "Epidural blood patch Evaluation of the volume and spread of blood injected into the epidural space.", Anesthesiology, no. 64, pp. 820-822
30. ? Scavone BM, Wong CA, Sullivan JT, et al (2004), "Efficacy of prophylactic blood patch in preventing post dural puncture headache in parturients after inadvertent dural puncture.", Anesthesiology, no. 101, pp. 1422-1477

• Ostheimer GW (Eds. Marx GF) (1979), "Headache in the Postpartum Period in Clinical Management of Mother and Newborn", Springer-Verlag, New York, pp. 27-41</ref>