 CORRESPONDENCE Anesthesiology 2005; 103:900 © 2005 American Society of Anesthesiologists, Inc. Lippincott Williams & Wilkins, Inc. Why Does Prophylactic Epidural Blood Patch Fail to Demonstrate Efficacy in Preventing Post–Dural Puncture Headache in Parturients after Dural Puncture? To the Editor:— We read with interest the study by Scavone et al. 1 that demonstrates the absence of efficacy of a prophylactic epidural blood patch after inadvertent dural puncture. We suggest that two factors could have influenced the negative result of this trial. First, inadvertent dural puncture could have been overdiagnosed, namely when loss of resistance to saline was used to locate epidural space. This could explain the lower incidence of post– dural puncture headache and less frequent realization of therapeutic epidural blood patch reported in this study compared with others. 2,3 Second, 20 ml may not be the adequate blood volume to test a prophylactic epidural blood patch. This volume has tended to increase over time to 20 ml or more, 23  5 ml in a study by Safat-Tisseront et al. 3 The optimal blood volume may be the volume at which pain in the back, buttocks, or legs occurs, which was only achieved for seven patients in the study of Scavone et al. This higher volume may lead to either a larger patch over the dural tear or a significantly higher increase in lumbar and intracranial pressure, leading to reduced cere- bral vasodilation. Olivier Pruszkowski, M.D.,* Orlando Goncalves, M.D., Claude Lentschener, M.D., Alexandre Mignon, M.D., Ph.D. *Ho ˆpital Cochin Maternite ´ Port-Royal, Assistance Publique–Ho ˆpitaux de Paris, Paris, France. olivier.prus@club-internet.fr References 1. Scavone BM, Wong CA, Sullivan JT, Yaghmour E, Scherwani SS, McCarthy RJ: Efficacy of prophylactic epidural blood patch in preventing post dural punc- ture headache in parturients after inadvertent dural puncture. ANESTHESIOLOGY 2004; 101:1422–7 2. Safat-Tisseront V, Thormann F, Malassine P, Henry M, Riou B, Coriat P, Seebacher J: Effectiveness of epidural blood patch in the management of post– dural puncture headache. ANESTHESIOLOGY 2001; 95:334–9 3. Crawford JS: Experiences with epidural blood patch. Anaesthesia 1980; 35:513–5 (Accepted for publication June 7, 2005.) Anesthesiology 2005; 103:900 © 2005 American Society of Anesthesiologists, Inc. Lippincott Williams & Wilkins, Inc. In Reply:—We appreciate the comments of Dr. Pruszkowski et al. regarding our recently published article. 1 Although we did not stan- dardize epidural placement technique, it is standard practice at our institution to use loss of resistance to air to identify the epidural space, and it is unlikely that many, if any, procedures were performed using the loss of resistance to saline technique. Therefore, we do not believe this contributed to an overdiagnosis of inadvertent dural puncture, as suggested. In fact, the loss of resistance to air technique may be associated with a higher rate of post– dural puncture headache than the loss of resistance to saline technique. 2 The rate of post– dural puncture headache in our study (56%) corresponds closely with that found in a meta-analysis of dural puncture with an epidural needle in obstetric patients: 52.1% (95% confidence interval, 51.4 –52.8%). 3 We agree with the authors that the optimal volume of blood for an epidural blood patch is not known. Although approximately 20 ml seems to be the standard dose, volume of blood was not associated with epidural blood patch success in the retrospective study cited by the authors. 4 As noted, sacral pressure or pain was observed in only a small number of subjects who received a prophylactic epidural blood patch. This likely reflects the fact that the blood was, of necessity, injected through the 19-gauge, 88-cm epidural catheter at a much slower rate than is possible through a 17- or 18-gauge, 9-cm epidural needle, thus resulting in a smaller increase in epidural pressure during the injection. Although it is possible that modifications of the tech- nique could result in a higher rate of efficacy of prophylactic epidural blood patch, our study clearly demonstrated no difference in the incidence of post– dural puncture headache using the technique as it is commonly practiced. Barbara M. Scavone, M.D.,* Cynthia A. Wong, M.D. *Northwestern University Feinberg School of Medicine, Chicago, Illinois. bimscavone@aol.com References 1. Scavone BM, Wong CA, Sullivan JT, Yaghmour E, Sherwani SS, McCarthy RJ: Efficacy of a prophylactic epidural blood patch in preventing post dural puncture headache in parturients after inadvertent dural puncture. ANESTHESIOLOGY 2004; 101:1422–7 2. Aida S, Taga K, Yamakura T, Endoh H, Shimoji K: Headache after attempted epidural block. ANESTHESIOLOGY 1998; 88:76–81 3. Choi PT, Galinski SE, Takeuchi L, Lucas S, Tamayo C, Jadad AR: PDPH is a common complication of neuraxial blockade in parturients: A meta-analysis of obstetrical studies. Can J Anaesth 2003; 50:460–9 4. Safa-Tisseront V, Thormann F, Malassine ´ P, Henry M, Riou B, Coriat P, Seebacher J: Effectiveness of epidural blood patch in the management of post– dural puncture headache. ANESTHESIOLOGY 2001; 95:334–9 (Accepted for publication June 7, 2005.) Anesthesiology 2005; 103:900–1 © 2005 American Society of Anesthesiologists, Inc. Lippincott Williams & Wilkins, Inc. Iliac Crest Bone Harvest: Should We Really Use Continuous Infusion of Ropivacaine? To the Editor:—We read with interest the article by Blumenthal et al. 1 about effectiveness of continuous ropivacaine infusion at the iliac crest donor site. This study seems to confirm the results of Brull et al. 2 obtained with continuous bupivacaine infusion. However, several points deserve some comments from the authors before their conclu- sions can be accepted. First, the primary goal and the calculation of the number of patients needed for the study deserve clarification. Was this study built to Anesthesiology, V 103, No 4, Oct 2005 900 Downloaded from http://pubs.asahq.org/anesthesiology/article-pdf/103/4/906/359844/0000542-200510000-00042.pdf by guest on 01 January 2022