Epidural Blood Patch - The Effect of Volume

In this study we wish to work out what volume of blood, injected into the epidural area in an "epidural blood patch" best cures or helps treat headache caused by leak of spinal fluid. This leak occurs because a hole has been made in a membrane containing the spinal fluid, near the epidural space. An epidural blood patch is the only known way of stopping or effectively reducing headache of this type and is used worldwide to treat severe headaches of this type. It can fix the headache completely, but is often only partially effective. Many years ago the volume of blood used in an epidural blood patch was very small. Later the recommended volume was increased to about 15 ml, as this appeared to work better. Subsequently, larger volumes of blood, such as 20 ml, were recommended, while some anaesthetists now claim best results when even more is injected. There have not been any well controlled studies comparing different volumes of blood for epidural blood patch. Although larger volumes of blood are currently favoured, these may be associated with a higher incidence of mild or moderate low back pain during the injection and subsequent back soreness. A number of maternity units in Australasia and overseas will be involved in this study and the results will be of interest internationally. What does the study involve? The epidural blood patch will be performed in the usual way. Patients will be randomised to one of three groups, each group receiving a slightly different volume of blood (15 ml, 20 ml or the maximum volume up to 30 ml that can be injected without causing significant discomfort in the back). It is usually easy to inject 15 or 20 ml without causing significant back discomfort and the volumes chosen are all ones commonly used by maternity units around the world. In addition, to make sure the most accurate results are obtained, neither the patient or the staff asking questions about well-being after the epidural blood patch will know which group the patient was in. Patients will be asked questions about the severity and characteristics of the headache both before and at regular intervals after the epidural blood patch (at 2, 4, 24, 48, 72 hours and 5 days, by telephone if the patient has left hospital). Patients will also be asked about back discomfort experienced during and after the procedure, and whether they noticed any effects other than relief of the headache. As is usual practice, patients will be rested flat in bed for 2 hours after the epidural blood patch and then be allowed to get up, according to the usual practice in the hospital. If the patient does not get complete relief of the headache or suffers a return of headache later, they will be able to use a variety of drugs to try and get some relief. Also, if necessary, another blood patch could be performed, once more than 48 hours has passed from the first epidural blood patch. We will not know whether any particular volume is more effective than another. With an epidural blood patch, a common effect is mild back discomfort during injection and for a variable time after the blood patch, lasting up to a few days. If the patient experiences significant back pain during the injection, the injection will be stopped according to usual practice, irrespective of whether they have received the amount for their group. Usually back pain during injection is mild and easy to handle. Most women describe back stiffness rather than pain after the epidural blood patch. It has been suggested that injection of the largest volume of blood may be more effective but also cause more back discomfort, but this has not been confirmed by proper study. There are some very rare serious complications of epidural blood patch, such as infection, severe back pain and blood clots around the brain, but there is no suggestion that taking part in the study is likely to affect the risk of these in any way.