How much work is required to puncture dura with Tuohy needles?

The effects of needle bevel orientation and cerebrospinal fluid (CSF) pressure on dural displacement and force required to penetrate cadaveric dura were studied using 40 samples. A constant hydrostatic pressure was applied to the subdural surface, either high or low, simulating the sitting and lateral positions. A 17-gauge Tuohy needle was advanced through the dura with the bevel oriented parallel or perpendicular to dural fibres. Travel distance and peak force at which dural penetration occurred were measured under both pressure conditions. The work required to produce dural penetration was calculated. Greater force and work were required to penetrate dura in the perpendicular orientation (P < 0.05), regardless of the subdural pressure exerted. Dural displacement was similar under both pressure conditions.

Effects of epidural steroids on lumbar dura material properties.

Epidural steroid injections are commonly used in the treatment of low back pain and radiculopathy based on their antiinflammatory and analgesic benefits. However, steroids are known to affect collagen synthesis, material strength, and tissue healing. The purpose of this study was to assess the effects of serial epidural steroid injections on the material properties of the lumbar dura mater. Serial epidural steroid injections of saline or methylprednisolone at 2-week intervals were performed in three paired groups of canines; a separate noninjected group was used as controls. Postmortem, dural sample testing to failure and histologic analysis was performed. Mechanical failure testing revealed no clinically significant change in the transverse dorsal dura tensile strength between all saline-injected, steroid-injected, or noninjected controls. Histologic analysis demonstrated no overt disruption of collagen matrix organization; however, electron microscopy demonstrated a significant decrease in the number of intracytoplasmic mitochondria of dural fibroblasts in steroid-injected animals, suggesting a metabolic inhibitory effect within steroid-injected dura mater. In the clinical time frame of this study, serial epidural steroid injections appeared to produce no significant material or matrix changes in the lumbar dura.

Subdural injection of a local anesthetic with steroids: complication of epidural anesthesia.

We describe the unintentional injection of a small amount of local anesthetic with steroids into the subdural space during an attempted lumbar epidural injection for low back pain. When small volumes of local anesthetic are injected into the subdural space, a patchy and unilateral block of greater magnitude than expected will result. When larger volumes of local anesthetic are injected, a massive motor and sensory block can occur due to the small confines of this space. Accidental subdural injection must be recognized early and treated appropriately to avoid serious complications, especially in an outpatient setting.

Anatomic and biomechanical properties of human lumbar dura mater.

Determinants of dural defects subsequent to deliberate or accidental dural puncture include the equipment, techniques, and the inherent anatomic and biomechanical properties of dura mater. These properties were studied in specimens of human and canine lumbar dura mater in an attempt to delineate the structure of the tissue and to characterize its behavior in biomechanical terms. Human dura had a longitudinal orientation on gross appearance, and was confirmed microscopically to be composed of longitudinal lamella of collagen and elastin fibers. Longitudinal tensile strength and stiffness were greater than transverse tensile strength and stiffness, which is consistent with the dura's apparent anatomic structure and functional requirements. Additional biomechanical testing of the dura demonstrated the property of relaxation which is a characteristic of a viscoelastic material. Significant differences were observed between human and canine dural properties, suggesting limited value of this animal model. Integration of these observed anatomic and biomechanical properties of the lumbar dura provides a greater understanding of dural puncture and may explain previous and often confusing clinical and experimental findings.

Epidural anesthesia for lumbar spine surgery.

A retrospective review of the hospital records of 80 patients undergoing elective lumbar spine surgery was performed, in order to determine the effect of anesthetic technique on various clinical parameters. Forty patients receiving epidural bupivacaine anesthesia were matched with 40 patients receiving general endotracheal anesthesia; these two groups were homogeneous based on age, sex, type of operative procedure, and number of spinal levels operated upon. Significant results included lower injectable narcotic requirements (p less than 0.001), lower incidence of postoperative urinary retention (p less than 0.01), and lower operative blood loss (p less than 0.1) for patients receiving epidural anesthesia. Epidural bupivacaine provided satisfactory anesthesia, and allowed intraoperative testing of lower extremity motor function. In a follow-up surgery, 38 of 40 patients who received epidural anesthesia were satisfied with the technique. For patients undergoing decompressive lumbar spine surgery, epidural bupivacaine anesthesia is an effective, well tolerated technique with several potential advantages, and an acceptable incidence of complications, as compared with general endotracheal anesthesia.

Technical and pharmacologic management of distal hypotension during repair of coarctation of the aorta.

Neurologic and abdominal complications can occur in the postoperative period of aortic coarctation repair, ischemia being the pathogenic factor most likely to be involved. This study was designed to evaluate the extent of the hemodynamic changes proximal and distal to the coarctation at the time of cross-clamping, as well as the effects of pentolinium and isoproterenol upon the hemodynamic changes. Included in the study were 17 patients with adult type coarctations who had dual hemodynamic monitoring. During cross-clamping, there was an increase in the gradient between proximal and distal pressures, with severe distal hypotension (< 50 mm Hg) occurring in six patients. Isoproterenol corrected the hypotension in five patients, but the sixth required a surgical shunt. Pentolinium was effective for the treatment of proximal hypertension; however, it also decreased distal pressure. The ligation of collateral vessels was associated with a decrease in distal pressures as well. During cross-clamping, pentolinium was useful for the management of proximal hypertension and isoproterenol increased the distal pressures in some of the patients who presented distal hypotension. However, because of the difficulties in predicting the individual response, their administration would be best guided by dual pressure monitoring. It is postulated that the recognition and proper treatment of distal hypotension may be an important factor in the prophylaxis of postoperative complications.