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Unpredictable central nervous system effects after lorazepam premedication for neurosurgery.

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.

Adult↗

The use of midazolam in premedication.

Socio-psychological factors, such as increased anxiety in developed societies and cultures, and separation anxiety, particularly in children, justify the use of premedicants. In addition, the link between a central nervous "anxiety centre" and biochemical stress responses is blocked by an efficient anxiolytic. The elimination half-life of midazolam is longer in the elderly than in the young and in the obese than in the thin, which demands longer intervals between repeated doses in old and fat patients. The hypoxic ventilatory response is depressed in most patients and the ventilatory CO2 response in patients with chronic pulmonary disorders, which justifies increased monitoring of O2 saturations. It is important for the choice of dose and for estimating the duration of recovery time to know that midazolam is at least four times as potent as diazepam.

Anxiety↗

Dixyrazine premedication for cataract surgery. A comparison with diazepam.

Peroral dixyrazine (15-30 mg, n = 50) and diazepam (4-10 mg, n = 50) were used as premedicants for geriatric patients having cataract surgery under regional block. Compared to the diazepam patients, a larger number of the dixyrazine medicated patients appeared anxious, and there was a statistically significant difference between the groups, when summing up changes in anxiety throughout the study period. The dixyrazine patients needed more frequent supplementation with intravenous sedative drugs, compared with their diazepam counterparts. Peroral dixyrazine is an applicable choice for calm patients, when only slight sedation, or avoidance of somnolence are required.

Administration, Oral↗

The effect of premedication with OTFC, with or without ondansetron, on postoperative agitation, and nausea and vomiting in pediatric ambulatory patients.

BACKGROUND: The purpose of this study was to evaluate, in the pediatric ambulatory surgical population, the efficacy of: (i) oral transmucosal fentanyl citrate (OTFC), when given preoperatively, to reduce postoperative excitement associated with sevoflurane, and (ii) intravenous ondansetron to reduce postoperative nausea and vomiting (PONV) associated with OTFC. METHODS: This randomized, double-blinded, placebo controlled study evaluated the efficacy of OTFC [normal dose (ND) = 10-15 microg x kg(-1) or low dose = 100 microg] compared with placebo in the prevention of postoperative agitation; and the efficacy of ondansetron (0.1 mg x kg(-1) to 4 mg) compared with placebo to reduce PONV associated with OTFC. RESULTS: There were 125 patients evaluated (2-10 years old, ASA class I or II and weight 10-40 kg). Preoperatively OTFC was associated with an increased likelihood of cooperation at baseline (P = 0.018). Postoperatively there was a higher incidence of vomiting in children that received OTFC. The anxiety/agitation of patients entering the PACU was significantly less in children who received OTFC ND (P < 0.001). This effect decreased over time. Patients with respiratory adverse events related to the study drug were significantly higher in groups who received OTFC, however, they were not of clinical significance. OTFC was associated with delays in time for eligibility to PACU discharge (P = 0.003). CONCLUSIONS: Even though OTFC reduced early postoperative agitation the increase in side effects, namely PONV and prolonged recovery times, limits its clinical usefulness. The study demonstrates the tradeoffs between anxiety and agitation vs vomiting, respiratory events and prolonged recovery times. Ambulatory pediatric patients undergoing procedures in which opioids would be routinely used might benefit the most from OTFC combined with ondansetron as part of the anesthetic technique.

Administration, Oral↗

Dose-sparing effects of romifidine premedication for thiopentone and halothane anaesthesia in the dog.

Two intravenous doses of romlfidine (40 and 80 micrograms/kg) and a placebo were compared as premedicants for anaesthesia induced with thiopentone and maintained using halothane in oxygen. Romifidine significantly and linearly reduced the induction dose of thiopentone; placebo-treated dogs required 15.1 +/- 3.6 mg/kg, while dogs treated with 40 micrograms/kg and 80 micrograms/kg romifidine required 6.5 +/- 1.6 and 3.9 +/- 0.3 mg/kg thiopentone, respectively. Romifidine also significantly and linearly reduced the end tidal halothane concentration necessary to maintain a predetermined level of anaesthesia; placebo-treated dogs required 1.6 +/- 0.3 per cent halothane, while dogs treated with 40 micrograms/kg and 80 micrograms/kg romifidine required 1.3 +/- 0.4 and 0.8 +/- 0.2 per cent, respectively. Romifidine produced a significant shortening in the recovery from anaesthesia, and the higher dose of romifidine significantly improved the overall quality of anaesthesia.

Adrenergic alpha-Agonists↗