Unpredictable Central Nervous System Effects after Lorazepam Premedication for Neurosurgery

Abstract

Administration of lorazepam for preanaesthetic medication is generally expected to produce amnesic action. We conducted two studies to evaluate the relationship of plasma levels of lorazepam with its clinical effects. Forty patients, receiving 0.03 or 0.05 mg/kg lorazepam i.m. as preanaesthetic medication for various neurosurgical procedures, were asked 24 h after anaesthesia whether they could recall the insertion of the i.v. needle and a picture shown to them before induction of anaesthesia. Another 11 patients were given 0.03 mg/kg lorazepam i.v. and their degree of drowsiness was rated immediately before induction of anaesthesia. Plasma levels of lorazepam were measured by gas chromatography from samples drawn before induction of anaesthesia. No relationship between either the dose of lorazepam used or the plasma levels of lorazepam and the incidence of amnesia or the degree of drowsiness was observed. Three patients receiving 0.05 mg/kg of lorazepam i.m. had prolonged drowsiness, which made it difficult to check the patients' neurological condition after the operation. It is postulated that the unpredictable and variable central nervous system effects of lorazepam in neurosurgical patients may be due to differences in the capacity of lorazepam to penetrate the blood brain barrier.

Preoperative Assessment of Adult Patients for Intracranial Surgery

“…A recent study found that there was an increased need for information, especially about surgery, in patients with high levels of preoperative anxiety [24]. Preoperative treatment with anxiolysis or opioids is a controversial subject [25]. Patients who have increased ICP, or are obtunded are at a high risk of developing respiratory depression and even further increases in ICP with any sedation.…”