Robert E. Molloy

Sign of complete sympathetic blockade: Sweat test or sympathogalvanic response?

The sensitivity, specificity, and accuracy of the cobalt blue and ninhydrin sweat tests were compared with the sympathogalvanic response (SGR) in assessment of complete sympathetic blockade. Patients were randomly assigned to receive epidural administration of either preservative-free physiologic saline solution and 80 mg methylprednisolone (group I, control group, 9 patients) or 1.5% lidocaine with 80 mg methylprednisolone (group II, sympathetic blocked group, 10 patients). In group I, there was one false positive SGR (absence of SGR) before the block and there were four false positive SGRs after the block. In comparison, there were no false positive sweat tests (absence of sweating) before and after injection in group I. In group II, there were three false positive SGRs and no false positive sweat test before injection. After injection, one patient with an upper level of sensory blockade at T5 had persistent SGRs and positive sweat tests (false negative results). The study showed the sensitivity of the SGR and the sweat tests to be 90%. The specificity of the SGR was 56% compared to 100% for the sweat tests. The accuracy of the SGR was 74% compared to 95% for the sweat tests.

Postdural Puncture Headache in Patients with Chronic Pain

The incidence of headache after dural puncture in patients being treated for chronic pain was studied prospectively. Dural punctures were performed in 142 patients and headache developed in 13 (9.2%). Four of 32 patients (12.5%) who underwent diagnostic differential spinal and nine of 110 patients (8.2%) given intrathecal steroid injection developed headache. There was a 10.7% incidence of headache when a 22-gauge needle was used as compared to 5% with a 25-gauge needle. This difference was not statistically significant. The incidence decreased with increasing age. The incidence of postdural puncture headache in chronic pain patients does not differ significantly from that previously reported for surgical patients. All patients who developed headache responded to treatment which consisted of intravenous and oral fluids, analgesics, bed rest, and, if necessary, epidural blood patch.

Delayed onset of epidural anesthesia in patients with back pain

Onset and completeness of anesthesia were compared in 15 patients with back pain or sciatica and in 10 patients without back pain given lumbar epidural anesthesia with 20 to 25 ml of 1.5% mepivacaine, 80 mg of methylprednisolone, and 1:200,000 epinephrine. Sensory block was complete within 30 minutes in patients without back pain. Eleven of 15 (73%) patients with back pain had delayed onset of anesthesia ranging from 35 to 95 minutes. The difference between the two groups was statistically significant (p < 0.001). When there was a delay, the affected nerve roots were blocked 10 to 70 minutes after the contralateral unaffected roots. Differences in time of onset between affected nerves and contralateral nerves were also significant (p < 0.01). The nerve roots involved, as determined from the myelogram or the electromyogram, or those adjacent to them, were the roots with delayed onset of block. Any effect of the steroid on nerve blockade was ruled out as there was solid anesthesia in patients without back pain.

The current status of epidural steroids

Caudal, lumbar, and cervical epidural steroid injections (ESI) have been used for a number of years. A suspension of methylprednisolone acetate or triamcinolone diacetate is injected with a diluent of normal saline or local anesthetic. Steroids are used to decrease nerve root inflammation and suppress neuronal discharge. Response to lumbar ESI has been correlated with herniated disk, nerve root irrigation, and recent onset of symptoms. Failure to respond has been associated with prolonged duration of pain, unemployment due to pain, nonradicular diagnosis, and smoking. The few well-performed studies of ESI have yielded conflicting results. For cervical ESI, radicular pain predicts a better response; a radiologic diagnosis of herniated disk or a normal scan predicts a poorer outcome. ESI-related complications occur infrequently and are generally benign. However, adrenal suppression occurs for 1 month after injection. Preventive efforts are indicated for the rare but serious sequelae of epidural hematoma or abscess formation.