Despite conflicting evidence regarding the safety of intrathecal midazolam from animal investigations, its clinical use is increasing. We investigated the potential of intrathecal midazolam to produce symptomatology suggestive of neurological damage. This study compared two cohorts of patients who received intrathecal anesthesia with or without intrathecal midazolam (2 mg). Eighteen risk factors were evaluated with respect to symptoms representing potential neurological complications. The definitions of these symptoms were made wide to maximize the chance of counting patients with neurological sequelae after intrathecal injections. Eleven-hundred patients were followed up prospectively during the first postoperative week by a hospital chart review and 1 mo later by a mailed questionnaire. Symptoms suggestive of neurological impairment, including motor or sensory changes and bladder or bowel dysfunction, were investigated. Intrathecal midazolam was not associated with an increased risk of neurologic symptoms. In contrast, neurologic symptoms were found to be increased by age >70 yr (relative risk, 8.72) and the occurrence of a blood-stained spinal tap (relative risk, 8.07). The administration of intrathecal midazolam, 2 mg, did not increase the occurrence of neurologic or urologic symptoms, as suggested by some preclinical animal experimentation.
Implications: Intrathecal midazolam provides segmental analgesia, but conflicting animal studies have cast doubts on its safety. This investigation studied the effect of intrathecal midazolam by observing two cohorts of patients. In clinical practice, intrathecal midazolam (2 mg) did not increase adverse neurological symptoms compared with conventional therapies.