New drugs--boon or bane? Premedication and intravenous induction agents

A comprehensive evaluation between dexmedetomidine and midazolam for intraoperative sedation in the elderly: protocol for a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

The sedative effect of intraoperative sedation in elderly surgery exerts critical influence on the prognosis. Comparison on the safety and efficacy between dexmedetomidine and midazolam in many clinical randomized controlled trials (RCTs) was inconsistent and suspicious. We aim to comprehensively evaluate the safety and efficacy between dexmedetomidine and midazolam for intraoperative sedation in the elderly via meta-analysis and systematic reviews.

METHODS

RCTs regarding to the comparison of sedative effects and safety between dexmedetomidine and midazolam in elderly patients (aged ≥ 60 years) will be comprehensively searched from 2000 October to 2022 May through 4 English databases and 4 Chinese databases. After extraction in duplicate, the systematic review and meta-analysis will be performed on the primary outcomes (hemodynamic changes, sedative effect, cognitive function) and secondary outcomes (analgesic effect, surgical characteristics, complications, or adverse reactions) for assessing the two therapy methods using Review Manager software (Version 5.3). Sensitivity analysis will be conducted to evaluate the heterogeneity of the results; funnel plot and Egger's trial will be performed to analyze publication bias of the included studies, and trial sequential analysis will be applied to assess the robustness and reliability of preliminary meta-analysis results. Finally, rating quality of evidence and strength of recommendations on the meta results will be summarized by Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach.

DISCUSSION

This systematic review and meta-analysis will evaluate the safety and efficacy between dexmedetomidine and midazolam for intraoperative sedation in the elderly; it will give an insight on the application of dexmedetomidine and midazolam and will provide evidence-based reference for clinical decision-making.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42021221897.

Cardiovascular effects of pregnanolone emulsion: an experimental study in artificially ventilated dogs

The acute cardiovascular effects of pregnanolone emulsion, a new steroid preparation for intravenous anaesthesia, were investigated in artificially ventilated dogs. The anaesthetic was administered as repeated intravenous bolus injections, doubling the dosage with each injection. The plasma concentration of pregnanolone, and the haemodynamic, respiratory and metabolic variables were determined after each injection. Cardiac output and heart rate increased from the first bolus dose of the anaesthetic (0.5 mg/kg), which produced anaesthesia lasting 10 to 15 min. Both continued to increase after administration of 1.0, 2.0 and 4 mg/kg, whereas reductions of systemic arterial pressure and estimated myocardial contractility were observed only at the two highest dosages. A decrease in vascular resistance was calculated in the systemic circulation, whereas vascular resistance increased in the pulmonary circulation. A state of circulatory shock followed administration 8, 16 and 32 mg/kg of the anaesthetic.

Midazolam versus fentanyl/droperidol and placebo as intramuscular premedicant

Midazolam, a new short-acting benzodiazepine with promising premedicant effects, was investigated in a double-blind, randomized clinical trial in 203 patients versus fentanyl/droperidol and placebo. Subjective effects, side-effects, amnesia and overall satisfaction were recorded. Midazolam caused the greatest decrease in anxiety level, and while causing more confusion and somnolence than placebo, caused less confusion and somnolence than fentanyl/droperidol. Half the patients who received midazolam reported anterograde amnesia. No serious side-effects were reported. Patient satisfaction was greater in the midazolam group than in the other groups.

Midazolam: the first water-soluble benzodiazepine. Pharmacology, pharmacokinetics and efficacy in insomnia and anesthesia

Midazolam is a 1,4-benzodiazepine derivative with a unique chemical structure: depending on environmental pH, the drug can produce highly water-soluble salts (pH less than 4) or exist in lipophilic diazepine ring-closed form (pH greater than 4). This characteristic contributes to rapid onset of action and to good local tolerance after parenteral administration. After both oral and parenteral administration, midazolam has a fast absorption rate and is rapidly excreted, with a half-life of only about 2 hours. A reasonably good correlation has been found between plasma levels and clinical effects, indicating a fast but brief response. As a hypnotic, midazolam is mainly indicated in insomniac patients with difficulties in falling asleep or having a pathologic sleep pattern during the first half of the night. No marked hangover effects are present the next morning. In anesthesiology, midazolam appears to be a useful, short-acting, sedative-anxiolytic and amnesic premedicant after both oral and parenteral administration. In minor surgery, however, the slow, unpredictable onset and variable duration of action, as compared with thiopental, may inhibit its routine use as an induction agent, especially in young patients, without heavy premedication. In major surgery, midazolam is an alternative to thiopental for induction of anesthesia in spite of its slow, variable induction time. Its advantages include good cardiovascular stability, transient and mild respiratory depression, low frequency of venous irritation, production of anterograde amnesia and short duration of action in comparison with other benzodiazepines.

[Intramuscular premedication with midazolam in infants and children]

The useful intramuscular premedication dose of midazolam was determined in 100 children divided up in three age groups: one month to three years, 3 to 10 years, 10 to 15 years. All biometric parameters were normal for the age, and comparable between similar age groups. Haemodynamic and respiratory parameters were not altered by the premedication. The reduction in anxiety, as assessed by the child's behaviour, was good or excellent in more than 85% of cases from all age groups; it was proportional to the dose used. The doses that had, for equivalent reductions in anxiety as assessed by the chi-square test, the least hypnotic effect, were: 0.5 mg X kg-1 before three years of age, 0.4 mg X kg-1 for the 3 to 10 yr olds, and 0.25 mg X kg-1 for the 10 to 15 yr olds. This fall in dose with age, quite usual in paediatrics, was not unexpected. The level of consciousness, one hour after surgery, was always normal. No undesirable side-effect was observed. These results, together with its physical, chemical and pharmacodynamic characteristics, make midazolam a choice drug for intramuscular premedication in children, with a foreseeable use in day-care anaesthesia. The unexpected finding of an age-dependent dissociation between the reduction in anxiety and the hypnotic effect is discussed in the light of a study carried out in the adult and recent data from the literature.