Abstract
Epidural anesthesia and analgesia are commonly used for a number of medical and surgical procedures. Although the blind loss of resistance is usually successful in experienced hands, it can be challenging at times. Imaging technology is increasingly used to assist in the accurate localization of the epidural depth (ED). When compared to the blind loss of resistance technique, ultrasound measurements slightly underestimated; computed tomography slightly overestimated; while MRI depth measurement was more accurate, although it occasionally overestimated the ED. Ultrasound imaging resulted in fewer placement trials and increased the chances of success. The strongest predictor of epidural depth is body weight and body mass index. The epidural space is deeper in men than in women and in pregnant than in non-pregnant women. The role of ethnicity was studied in parturients and found to be deeper in patients of African origin and shallowest in the east Asian parturients. Regarding the level of insertion, it is deepest at the cervicothoracic and lumbosacral areas and the shallowest at the thoracolumbar area. It is also deeper when using the lateral, compared to the sitting position, and when using the paramedian or off-the-midline approach than the midline. The height, age, and technique probably have no effect or are controversial at best. The posterior epidural distance is smallest at the cervical level, enlarges as one moves caudally, and is largest at L4–5.
Similar content being viewed by others
References
Aldrete JA, et al. Skin to cervical epidural space distances as read from magnetic resonance imaging films: consideration of the “hump pad.” J Clin Anesth. 1998;10(4):309–13.
Palmer SK, et al. Distance from the skin to the lumbar epidural space in an obstetric population. Anesth Analg. 1983;62(10):944–6.
Watts RW. The influence of obesity on the relationship between body mass index and the distance to the epidural space from the skin. Anaesth Intensive Care. 1993;21(3):309–10.
Balki M. Locating the epidural space in obstetric patients-ultrasound a useful tool: continuing professional development. Can J Anaesth. 2010;57(12):1111–26.
Han KR, et al. Distance to the adult cervical epidural space. Reg Anesth Pain Med. 2003;28(2):95–7.
Sutton DN, Linter SP. Depth of extradural space and dural puncture. Anaesthesia. 1991;46(2):97–8.
Peralta F, et al. The relationship of body mass index with the incidence of postdural puncture headache in parturients. Anesth Analg. 2015;121(2):451–6.
Fujinaka MK, et al. Cervical epidural depth: correlation between needle angle, cervical anatomy, and body surface area. Pain Med. 2012;13(5):665–9.
Lirk P, et al. Accuracy in estimating the correct intervertebral space level during lumbar, thoracic and cervical epidural anaesthesia. Acta Anaesthesiol Scand. 2004;48(3):347–9.
Algrain H, et al. Cervical epidural depth: correlation between cervical MRI measurements of the skin-to-cervical epidural space and the actual needle depth during interlaminar cervical epidural injections. Pain Med. 2018;19(5):1015–22.
Lai HC, et al. Depth of the thoracic epidural space in paramedian approach. J Clin Anesth. 2005;17(5):339–43.
Adachi YU, Sanjo Y, Sato S. The epidural space is deeper in elderly and obese patients in the Japanese population. Acta Anaesthesiol Scand. 2007;51(6):731–5.
Piccioni F, et al. Weight and BMI are the most important predictors influencing the needle insertion distance to the thoracic epidural space. Eur J Anaesthesiol. 2015;32(11):820–2.
Hirabayashi Y, et al. Magnetic resonance imaging of the extradural space of the thoracic spine. Br J Anaesth. 1997;79(5):563–6.
Kim SH, et al. Sonographic estimation of needle depth for cervical epidural blocks. Anesth Analg. 2008;106(5):1542–7 table of contents.
Jones JH, et al. Assessing the agreement between radiologic and clinical measurements of lumbar and cervical epidural depths in patients undergoing prone interlaminar epidural steroid injection. Anesth Analg. 2017;124(5):1678–85.
Luo Y, et al. Suitable depth of epidural puncture in nulliparous pregnant woman. Cell Biochem Biophys. 2015;71(2):875–80.
Harrison GR, Clowes NW. The depth of the lumbar epidural space from the skin. Anaesthesia. 1985;40(7):685–7.
Meiklejohn BH. Distance from skin to the lumbar epidural space in an obstetric population. Reg Anesth. 1990;15(3):134–6.
Kaydu A, et al. Examination of spinal canal anatomy with MRI measurements in lumbar disc herniation patients: an anesthesiologist viewpoint. Anesth Essays Res. 2021;15(1):38–44.
Rasoulian A, et al. Utility of prepuncture ultrasound for localization of the thoracic epidural space. Can J Anaesth. 2011;58(9):815–23.
Ravi KK, et al. Distance from skin to epidural space: correlation with body mass index (BMI). J Anaesthesiol Clin Pharmacol. 2011;27(1):39–42.
D’Alonzo RC, et al. Ethnicity and the distance to the epidural space in parturients. Reg Anesth Pain Med. 2008;33(1):24–9.
Hamza J, et al. Parturient’s posture during epidural puncture affects the distance from skin to epidural space. J Clin Anesth. 1995;7(1):1–4.
Chen KP, Poon YY, Wong CH. The depth to the epidural space. Ma Zui Xue Za Zhi. 1989;27(4):353–6.
Bevacqua BK, Haas T, Brand F. A clinical measure of the posterior epidural space depth. Reg Anesth. 1996;21(5):456–60.
Sutherland GPR, Shaw M, Broom MA. Predicting epidural space depth in an obstetric population using patient demographics: an observational study of 1534 patients. Eur J Anaesthesiol. 2021;38(7):794–6.
Clinkscales CP, et al. An observational study of the relationship between lumbar epidural space depth and body mass index in Michigan parturients. Int J Obstet Anesth. 2007;16(4):323–7.
Zhao Q, et al. The distance from skin to cervical and high thoracic epidural space on Chinese adults as read from MRI. Pain Physician. 2014;17(2):163–8.
Tran D, et al. Preinsertion paramedian ultrasound guidance for epidural anesthesia. Anesth Analg. 2009;109(2):661–7.
Hirabayashi Y, et al. The distance from the skin to the epidural space. J Anesth. 1988;2(2):198–201.
Carnie J, Boden J, Gao Smith F. Prediction by computerised tomography of distance from skin to epidural space during thoracic epidural insertion. Anaesthesia. 2002;57(7):701–4.
Grau T, et al. Ultrasound imaging of the thoracic epidural space. Reg Anesth Pain Med. 2002;27(2):200–6.
Kao MC, et al. Prediction of the distance from skin to epidural space for low-thoracic epidural catheter insertion by computed tomography. Br J Anaesth. 2004;92(2):271–3.
Salman A, et al. Ultrasound imaging of the thoracic spine in paramedian sagittal oblique plane: the correlation between estimated and actual depth to the epidural space. Reg Anesth Pain Med. 2011;36(6):542–7.
Kessler J, Moriggl B, Grau T. The use of ultrasound improves the accuracy of epidural needle placement in cadavers. Surg Radiol Anat. 2014;36(7):695–703.
Kosturakis A, et al. Using computed tomography scans and patient demographic data to estimate thoracic epidural space depth. Pain Res Treat. 2015;2015:470240.
Sahota JS, et al. Ultrasound estimates for midline epidural punctures in the obese parturient: paramedian sagittal oblique is comparable to transverse median plane. Anesth Analg. 2013;116(4):829–35.
Singh S, et al. Epidural catheter placement in morbidly obese parturients with the use of an epidural depth equation prior to ultrasound visualization. Sci World J. 2013;2013:695209.
Balki M, et al. Ultrasound imaging of the lumbar spine in the transverse plane: the correlation between estimated and actual depth to the epidural space in obese parturients. Anesth Analg. 2009;108(6):1876–81.
Nishiyama T. Thoracic epidural catheterization using ultrasound in obese patients for bariatric surgery. J Res Obes 2014; 2014 (2014)
Wang Q, Yin C, Wang TL. Ultrasound facilitates identification of combined spinal-epidural puncture in obese parturients. Chin Med J (Engl). 2012;125(21):3840–3.
Sharma V, et al. Effect of ethnicity and body mass index on the distance from skin to lumbar epidural space in parturients. Anaesthesia. 2011;66(10):907–12.
Shiroyama K, et al. Distance from the skin to the epidural space at the first lumbar interspace in a Japanese obstetric population. Hiroshima J Med Sci. 2003;52(2):27–9.
Grau T, et al. The lumbar epidural space in pregnancy: visualization by ultrasonography. Br J Anaesth. 2001;86(6):798–804.
Helayel PE, et al. Evaluating the depth of the epidural space with the use of ultrasound. Rev Bras Anestesiol. 2010;60(4):376–82.
Grau T, et al. Efficacy of ultrasound imaging in obstetric epidural anesthesia. J Clin Anesth. 2002;14(3):169–75.
Arzola C, et al. Ultrasound using the transverse approach to the lumbar spine provides reliable landmarks for labor epidurals. Anesth Analg. 2007;104(5):1188–92 tables of contents.
Grau T, et al. Real-time ultrasonic observation of combined spinal-epidural anaesthesia. Eur J Anaesthesiol. 2004;21(1):25–31.
Cork RC, Kryc JJ, Vaughan RW. Ultrasonic localization of the lumbar epidural space. Anesthesiology. 1980;52(6):513–6.
Currie JM. Measurement of the depth to the extradural space using ultrasound. Br J Anaesth. 1984;56(4):345–7.
Bahk JH, et al. Computed tomographic study of lumbar (L3–4) epidural depth and its relationship to physical measurements in young adult men. Reg Anesth Pain Med. 1998;23(3):262–5.
Saravanakumar K, Rao SG, Cooper GM. Obesity and obstetric anaesthesia. Anaesthesia. 2006;61(1):36–48.
Hood DD, Dewan DM. Anesthetic and obstetric outcome in morbidly obese parturients. Anesthesiology. 1993;79(6):1210–8.
Perlow JH, Morgan MA. Massive maternal obesity and perioperative cesarean morbidity. Am J Obstet Gynecol. 1994;170(2):560–5.
Bamgbade OA, et al. Obstetric anaesthesia outcome in obese and non-obese parturients undergoing caesarean delivery: an observational study. Int J Obstet Anesth. 2009;18(3):221–5.
Vricella LK, et al. Anesthesia complications during scheduled cesarean delivery for morbidly obese women. Am J Obstet Gynecol. 2010;203(3):276 e1-5.
Gerig HJ, Kern F. Success and failure rate in peridural anesthesia. A 1-year study. Reg Anaesth. 1985;8(2):25–32.
Le Coq G, Ducot B, Benhamou D. Risk factors of inadequate pain relief during epidural analgesia for labour and delivery. Can J Anaesth. 1998;45(8):719–23.
Ehrenberg HM, et al. Prevalence of maternal obesity in an urban center. Am J Obstet Gynecol. 2002;187(5):1189–93.
Lau HP. The distance from the skin to the epidural space in a Chinese patient population. Ma Zui Xue Za Zhi. 1989;27(3):261–4.
Prakash S, et al. A prospective observational study of skin to subarachnoid space depth in the Indian population. Indian J Anaesth. 2014;58(2):165–70.
Taman HI, Farid AM, Abdelghaffar WM. Measuring skin to subarachnoid space depth in Egyptian population: a prospective cohort study. Anesth Essays Res. 2016;10(3):468–72.
Tan SH, Teo EC, Chua HC. Quantitative three-dimensional anatomy of lumbar vertebrae in Singaporean Asians. Eur Spine J. 2002;11(2):152–8.
Deurenberg P, Deurenberg-Yap M. Validity of body composition methods across ethnic population groups. Forum Nutr. 2003;56:299–301.
Norgan NG. Population differences in body composition in relation to the body mass index. Eur J Clin Nutr. 1994;48(Suppl 3):S10-25 discussion S26-7.
Konrad C, et al. Learning manual skills in anesthesiology: is there a recommended number of cases for anesthetic procedures? Anesth Analg. 1998;86(3):635–9.
Ellinas EH, et al. The effect of obesity on neuraxial technique difficulty in pregnant patients: a prospective, observational study. Anesth Analg. 2009;109(4):1225–31.
Butwick A, et al. Retrospective analysis of anesthetic interventions for obese patients undergoing elective cesarean delivery. J Clin Anesth. 2010;22(7):519–26.
Keplinger M, et al. Lumbar neuraxial anatomical changes throughout pregnancy: a longitudinal study using serial ultrasound scans. Anaesthesia. 2016;71(6):669–74.
Bassiakou E, et al. The distance from the skin to the epidural and subarachnoid spaces in parturients scheduled for caesarean section. Minerva Anestesiol. 2011;77(2):154–9.
Canturk M, Kocaoglu N, Hakki M. Abdominal girth has a strong correlation with actual and ultrasound estimated epidural depth. Turk J Med Sci. 2019;49(6):1715–20.
Grau T, et al. Paramedian access to the epidural space: the optimum window for ultrasound imaging. J Clin Anesth. 2001;13(3):213–7.
Neerken S, et al. Characterization of age-related effects in human skin: a comparative study that applies confocal laser scanning microscopy and optical coherence tomography. J Biomed Opt. 2004;9(2):274–81.
Gallagher D, et al. Appendicular skeletal muscle mass: effects of age, gender, and ethnicity. J Appl Physiol (1985). 1997;83(1):229–39.
Borkan GA, et al. Comparison of body composition in middle-aged and elderly males using computed tomography. Am J Phys Anthropol. 1985;66(3):289–95.
Gulay U, et al. Ultrasound-guided evaluation of the lumbar subarachnoid space in lateral and sitting positions in pregnant patients to receive elective cesarean operation. Pak J Med Sci. 2015;31(1):76–81.
Grau T, et al. Ultrasound control for presumed difficult epidural puncture. Acta Anaesthesiol Scand. 2001;45(6):766–71.
Hogan QH. Epidural anatomy: new observations. Can J Anaesth. 1998;45(5 Pt 2):R40–8.
Brummett CM, et al. A prospective, observational study of the relationship between body mass index and depth of the epidural space during lumbar transforaminal epidural steroid injection. Reg Anesth Pain Med. 2009;34(2):100–5.
Kim LK, et al. Analysis of influencing factors to depth of epidural space for lumbar transforaminal epidural block in Korean. Korean J Pain. 2011;24(4):216–20.
Hoffmann VL, et al. Posterior epidural space depth: safety of the loss of resistance and hanging drop techniques. Br J Anaesth. 1999;83(5):807–9.
Grau T, et al. Ultrasound imaging facilitates localization of the epidural space during combined spinal and epidural anesthesia. Reg Anesth Pain Med. 2001;26(1):64–7.
Furness G, Reilly MP, Kuchi S. An evaluation of ultrasound imaging for identification of lumbar intervertebral level. Anaesthesia. 2002;57(3):277–80.
Watson MJ, Evans S, Thorp JM. Could ultrasonography be used by an anaesthetist to identify a specified lumbar interspace before spinal anaesthesia? Br J Anaesth. 2003;90(4):509–11.
Whitty R, Moore M, Macarthur A. Identification of the lumbar interspinous spaces: palpation versus ultrasound. Anesth Analg. 2008;106(2):538–40 table of contents.
Schlotterbeck H, et al. Ultrasonographic control of the puncture level for lumbar neuraxial block in obstetric anaesthesia. Br J Anaesth. 2008;100(2):230–4.
Broadbent CR, et al. Ability of anaesthetists to identify a marked lumbar interspace. Anaesthesia. 2000;55(11):1122–6.
Perlas A, Chaparro LE, Chin KJ. Lumbar neuraxial ultrasound for spinal and epidural anesthesia: a systematic review and meta-analysis. Reg Anesth Pain Med. 2016;41(2):251–60.
Wallace DH, et al. Indirect sonographic guidance for epidural anesthesia in obese pregnant patients. Reg Anesth. 1992;17(4):233–6.
Greene NH, et al. Measurements of epidural space depth using preexisting CT scans correlate with loss of resistance depth during thoracic epidural catheter placement. Anesthesiol Res Pract. 2015;2015:545902.
Kim WJ, et al. Fluoroscope guided epidural needle insertion in midthoracic region: clinical evaluation of Nagaro’s method. Korean J Anesthesiol. 2012;62(5):441–7.
Patel A, Helm ER. Poster 381 depth assessment for cervical spinal epidural injections. PM R. 2016;8(9S):S285.
Hoffmann VL, et al. A new combined spinal-epidural apparatus: measurement of the distance to the epidural and subarachnoid spaces. Anaesthesia. 1997;52(4):350–5.
Capogna G, et al. Anatomy of the lumbar epidural region using magnetic resonance imaging: a study of dimensions and a comparison of two postures. Int J Obstet Anesth. 1997;6(2):97–100.
Nickalls RW, Kokri MS. The width of the posterior epidural space in obstetric patients. Anaesthesia. 1986;41(4):432–3.
Hogan QH. Lumbar epidural anatomy. A new look by cryomicrotome section. Anesthesiology. 1991;75(5):767–75.
Hollway TE, Telford RJ. Observations on deliberate dural puncture with a Tuohy needle: depth measurements. Anaesthesia. 1991;46(9):722–4.
Lyons G, Macdonald R, Mikl B. Combined epidural/spinal anaesthesia for caesarean section. Through the needle or in separate spaces? Anaesthesia. 1992;47(3):199–201.
Evans RW. Complications of lumbar puncture. Neurol Clin. 1998;16(1):83–105.
Westbrook JL, Renowden SA, Carrie LE. Study of the anatomy of the extradural region using magnetic resonance imaging. Br J Anaesth. 1993;71(4):495–8.
Vallejo MC, et al. Ultrasound decreases the failed labor epidural rate in resident trainees. Int J Obstet Anesth. 2010;19(4):373–8.
Abe KK, et al. Lumbar puncture needle length determination. Am J Emerg Med. 2005;23(6):742–6.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Human and Animal Rights and Informed Consent
This article does not contain any studies with human or animal subjects performed by any author.
Conflict of Interest
The author declares no competing interests.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
About this article
Cite this article
Nada, E. Predictors of Epidural Depth and the Role of Technology. Curr Anesthesiol Rep (2023). https://doi.org/10.1007/s40140-023-00573-1
Accepted:
Published:
DOI: https://doi.org/10.1007/s40140-023-00573-1