Large intrathecal volume: a cause of true failed spinal anesthesia

Abstract

A 37-year-old woman scheduled for postpartum tubal ligation received two intrathecal doses of 2% hyperbaric mepivacaine (44 mg and 40 mg) and a subsequent single dose of 5% hyperbaric lidocaine (62.5 mg). Her sensory level never extended beyond S1. She subsequently underwent an uneventful general anesthetic, and had no residual sensory or motor deficits. An examination of the patient's lumbosacral magnetic resonance imaging (MRI) scan revealed an unusually large thecal volume. A large lumbosacral intrathecal volume may result in significant dilution or poor redistribution of hyperbaric local anesthetic. The final sensory level may be reduced or absent as a result. Intrathecal volume may be the most important non-modifiable factor affecting intrathecal distribution of local anesthetics; however, it cannot be easily measured or predicted. True failed spinal anesthesia should be distinguished from technical mishap, i.e., failing to introduce the anesthetic into the intrathecal space. The differential of a truly failed single-injection spinal anesthetic may include a large thecal volume, dural ectasias, cysts, and simple anatomic sacral restriction. To minimize maldistribution and neurotoxicity, the sum dose of all intrathecal local anesthetics administered for a single procedure should not significantly exceed the maximum recommended single-dose amount.

An observational prospective cohort study of incidence and characteristics of failed spinal anaesthesia for caesarean section

“…Other reasons for failure of spinal anaesthesia include sacral maldistribution of local anaesthetics, ductal ectasia, cyst and simple anatomic sacral restriction. 20,21 Other studies have also attributed failure to defective batches of bupivacaine, especially when cases are clustered together. 22,23 Our cases were sporadic, thus we do not believe that this was the case.…”

Abdominal girth and dorso‐sacral distance can be used to estimate lumbosacral cerebral fluid volume

“…The high variability in individual lumbosacral cerebrospinal fluid volumes resulted in the spinal spread being highly unpredictable. Spiegel, J. E. et al reported a case of failed spinal anaesthesia caused by a large volume of cerebrospinal fluid in the intrathecal space. From a three‐dimensional reconstructed image of the lumbosacral cerebrospinal fluid, lower fluid volumes were found in volunteers with greater abdominal girth and shorter dorso‐sacral distance, and vice versa.…”

“…Previous studies have shown that lumbosacral cerebrospinal fluid volume is the primary determinant for the spinal spread . Because of wide individual variations in lumbosacral cerebrospinal fluid volume, variability in the extent of the spinal spread occurs frequently following intrathecal injection with a given dose of local anaesthetic Although lumbosacral cerebrospinal fluid volume can be measured by magnetic resonance imaging, this technique cannot be general adopted during spinal anaesthesia because of inconvenience and cost. A simple method for the assessment of the lumbosacral cerebrospinal fluid volume for spinal anaesthesia is needed in the clinical setting.…”

A Second Prone Dose Algorithm for Patients Undergoing Spinal Anesthesia During Thoracolumbar Surgeries

“…The size of the thecal sac and volume of CSF present are considerations as a large lumbar cistern may prevent the analgesic from reaching an effective concentration. A case study by Spiegel et al 19 presented a patient whose exceptionally large intrathecal volume, as measured by MRI, was the likely cause of a failed spinal anesthesia attempt. Another study by Wang et al 20 used the cross-sectional area of the dural sac acquired using ultrasound to effectively dose spinal anesthesia for patients undergoing transurethral prostate resection.…”