Pressure-Volume Relationships in the Spinal Canal and Potential Neurological Complications After Epidural Fluid Injections

Abstract

High-volume fluid injections into the spinal canal may lead to severe neurological complications. But when anatomical or pathological conditions in the spinal canal are unfavorable, even small volume epidural injections can cause dangerously high epidural, subarachnoid, and intracranial pressures or pressure gradients. Data obtained from the scientific literature and direct clinical observation are used to derive a first-order approximation of epidural, subarachnoid, and intracranial pressure responses to epidural fluid injections. Maximum allowable fluid volumes for single or multiple divided fluid injections over time are calculated. In the presence of spinal pathology, 10 ml of fluids may increase epidural pressure to >100 mmHg. Injection speed >4 ml per second may also generate dangerously high intraspinal and intracranial pressures. Intermitted bolus injections provide limited protection, but intraspinal pressures may rise very fast when a critical total injected volume is reached. Potential complications of increased intracranial pressures or large pressure waves include nerve palsies, tinnitus, blindness, stroke, and death. Spinal injections or endoscopy should be performed in an awake responsive patient or with direct cerebrospinal fluid pressure monitoring. A set of guidelines for epidural fluid management is given.

Suspected ischaemic myelopathy following lumbosacral epidural steroid injection in a dog

“…Therefore, it is recommended that all dogs should have a thorough pre‐anaesthetic examination performed to ensure systemic cardiopulmonary stability and have comprehensive monitoring during general anaesthesia regardless of the type of procedure and length of anaesthesia. Altered spinal cord blood flow could theoretically also occur secondary to the introduction of a significant volume of fluid into the epidural space, due to increased epidural pressure causing vascular compression 56 ; however, significant alterations in epidural pressure are considered unlikely in the current case given the small volume of fluid (both contrast and corticosteroid preparation) that was injected.…”

Is It Safe to Perform an Autologous Epidural Blood Patch on Patients with Underlying Spinal Stenosis or Lumbar Disc Disease? Case Report and Literature Review

“…In patients with lumbar stenosis, where the epidural space compliance is low, the pressures in the epidural space can be transmitted to the subarachnoid space and cause the subarachnoid pressure to rise. In patients who already have compressed nerve roots, this increase in intrathecal pressure can lead to further compression and potential ischemia of the vascular and neural structures of the spinal canal [9]. A prior case report by Hooten et al (2008) documents an instance of a patient with a history of congenital lumbar spinal stenosis developing acute back pain with radicular symptoms after an attempted epidural blood patch for PDPH.…”

Comparison of Peak Bulk Flow Rate of Programmable Intermittent Epidural Bolus and Manual Epidural Bolus Using a Closed-End Multiorifice Catheter

“…Fast fluid injection may cause steep pressure waves in the epidural space and may exert significant forces on the tissues of the central nervous system. 6 However, until now, there was no information on how high pressure would need to be elevated to cause any morbidity. And, of course, it was unethical to conduct these trials.…”