Unilateral Epidural Block: A Persistent Problem with No Good Solution

Ling-Qun Hu and Joseph B Bavaro

Department of Anesthesiology, Northwestern University Feinberg School of Medicine, USA

*Corresponding author: Ling-Qun Hu, M.D., Department of Anesthesiology, Northwestern University Feinberg School of Medicine, 251 E. Huron St. F4-701 Chicago, IL 60611, USA, Tel: 1-312-695-0061, Fax: 1-312-695-9013, E-mail: l-hu2@northwestern.edu

Editor: Li-Ming Zhang, MD, PhD, Department of Anesthesiology, University of Pittsburgh, 200 Lothrop Street, UPMC MUH Suite N-467, Pittsburgh, PA 15213, United States of America, 412-648-6077, zhangl1@anes.upmc.edu

Received: March 22, 2018 | Accepted: March 28, 2018| Published: April 05, 2018

Citation: Hu LQ, Bavaro JB. Unilateral Epidural Block: A Persistent Problem with No Good Solution. Transl Perioper & Pain Med 2018; 5 (2):38-39.

Unilateral epidural analgesia is a common and persistent issue of incomplete analgesia. This phenomenon of one-sided epidural catheter placement was first described in 1967 through radiographic analysis [1], and examples of unilateral epidural analgesia continue to exist a half century later.

Clinically, it is important to better understand how to troubleshoot and even avoid unilateral analgesia in daily practice. This is especially important when stat cesarean delivery is involved. In 2015, Yeager, et al. showed that unilateral epidural catheter placement is associated with complicated postoperative courses [2]. To this end, efforts have been made to decrease the incidence of inadequate epidural block. These efforts include: improved epidural catheter design [3], comparing the use of saline versus air to find loss of resistance when placing catheters [4], and examining outcomes from shallow catheter placement (i.e. < 4 cm) in epidural space [5]. However, these solutions have not proven to be entirely effective.

In this editorial, we review a novel approach, proposed by Dr. Zhang, to increase the likelihood of bilateral epidural analgesia by using patient feedback during epidural catheter insertion and rotating the epidural needle to direct the catheter medially [6].

Several studies support this concept. One study used computerized tomography (CT) to investigate the positioning of epidural catheter tips and spread of injected radiocontrast, and correlated these findings with spread and laterality of sensory blockade. Far lateral catheter position was found to be the most common cause of unilateral block [7]. In another study, 7 out of 236 patients (3.0%) showed signs of unilateral block due to epidural catheter tips located either at the anterior epidural space (4 patients) or in the transforaminal passage (3 patients) [8]. Two studies investigating intentional rotation of epidural needles have found this to be an effective technique in targeting specific sides for analgesia/anesthesia. This suggests that needle orientation and rotation can contribute to unilateral blocks and may be important in avoiding these blocks [9,10]. Finally, imaging-guided epidural catheter placement has been routinely used to provide bilateral analgesia, with high success rates, in chronic pain management, suggesting increasing rates of centrally-placed catheters may decrease the incidence of unilateral block [11].

However, Zhang's approach raises three interesting questions: 1) Can all individuals feel their epidural catheter insertion and appreciate its laterality? 2) Is it a good idea to redirect catheters by rotating the needles and potentially "core out" the dura, or to repeatedly insert and withdraw the epidural catheter from the end of the epidural needle, with the risk of potentially shearing or otherwise damaging the catheter [9]? and 3) While this technique may increase likelihood of midline catheter placement initially, how often does subsequent catheter migration within the epidural space ultimately lead to a unilateral block?

Moreover, another study investigated 11 parturients with unilateral epidural analgesia and their epidurogram findings suggested at least three other explanations: 1) 5 cases with midline anatomical barriers, 2) 2 cases with spinal deformity, and 3) 4 cases with catheter malfunction [12]. Bolusing of local anesthetic was more effective than catheter manipulation at resolving unilateral block [13], and the use of programmed intermittent epidural bolus, rather than continuous epidural infusion, for maintenance of labor analgesia decreased the incidence of unilateral block 3-fold [14]. Interestingly, the incidence of right-sided block was approximately 4.2 times greater than the incidence of left sided-block [13]; this could potentially be attributable to preferential use of left uterine displacement of laboring women with patient-controlled epidural analgesia or continuous epidural infusion. Studies have also revealed that a previous history of unilateral block is a risk factor for the development of subsequent unilateral block, suggesting that that anatomic variations such as epidural septae may significantly contribute to this phenomenon [15]. In the other words, Dr. Zhang's method may not solve unilateral block issue completely.

In conclusion, while Dr. Zhang's approach has generated a hypothesis for future studies (with some outstanding concerns regarding safety and effectiveness), it is unlikely to be adopted as the standard of care under current conditions.




  1. Singh A. Unilateral epidural analgesia. Anaesthesia. 1967 Jan 1;22(1):147-9.
  2. Yeager MP, Bae EE, Parra MC, Barr PA, Bonham AK, Sites BD. Fluoroscopy‐assisted epidural catheter placement: an exploratory analysis of 303 pre‐operative epidurograms. Acta Anaesthesiologica Scandinavica. 2016 Apr 1;60(4):513-9.
  3. Toledano RD, Tsen LC. Epidural catheter design history, innovations, and clinical implications. Anesthesiology. 2014 Jul 1;121(1):9-17.
  4. Schier R, Guerra D, Aguilar J, Pratt GF, Hernandez M, Boddu K, Riedel B. Epidural space identification: a meta-analysis of complications after air versus liquid as the medium for loss of resistance. Anesthesia & Analgesia. 2009 Dec 1;109(6):2012-21.
  5. D'angelo R, Berkebile BL, Gerancher JC. Prospective examination of epidural catheter insertion. Anesthesiology: 1996 Jan 1;84(1):88-93.
  6. Zhang J. Correct Positioning of Epidural Catheters Is the Key to Avoiding Unilateral Labor Analgesia. 2018; 5(2):33-37.
  7. Hogan Q. Epidural catheter tip position and distribution of injectate evaluated by computed tomography. Anesthesiology. 1999 Apr 1;90(4):964-70.
  8. Asato F, Goto F. Radiographic findings of unilateral epidural block. Anesthesia & Analgesia. 1996 Sep 1;83(3):519-22.
  9. Borghi B, Agnoletti V, Ricci A, van Oven H, Montone N, Casati A. A prospective, randomized evaluation of the effects of epidural needle rotation on the distribution of epidural block. Anesthesia & Analgesia. 2004 May 1;98(5):1473-8.
  10. Sen O, Donmez NF, Ornek D, Kalayci D, Arslan M, Dikmen B. Effects of epidural needle rotation and different speeds of injection on the distribution of epidural block. Brazilian Journal of Anesthesiology. 2012 Nov 1;62(6):852-62.
  11. Parra MC, Washburn K, Brown JR, Beach ML, Yeager MP, Barr P, Bonham K, Lamb K, Loftus RW. Fluoroscopic guidance increases the incidence of thoracic epidural catheter placement within the epidural space: a randomized trial. Regional anesthesia and pain medicine. 2017 Jan 1;42(1):17-24.
  12. Collier CB. Why obstetric epidurals fail: a study of epidurograms. International journal of obstetric anesthesia. 1996 Jan 1;5(1):19-31.
  13. Beilin Y, Zahn J, Bernstein HH, Zucker-Pinchoff B, Zenzen WJ, Andres LA. Treatment of incomplete analgesia after placement of an epidural catheter and administration of local anesthetic for women in labor. Anesthesiology. 1998 Jun 1;88(6):1502-6.
  14. McKenzie CP, Cobb B, Riley ET, Carvalho B. Programmed Intermittent Epidural Boluses for Maintenance of Labor Analgesia: An Impact Study. International Journal of Obstetric Anesthesia. 2017 Mar 1;37(1):1-2.
  15. Padalia RB, Reeves CJ, Shah N, Patel AA, Padalia DM. Case report: bilateral tunneled epidural catheters to prevent unilateral analgesia for cancer-related pain. Local and regional anesthesia. 2017;10:79.