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BENZODIAZEPINSThey are most widely represented in modern anesthesiology by diazepam (seduxen, sibazonum, relanium), midazolam (dormicum) and flunitrazepam (rohypnol).
Diazepam is produced as 5-mg tablets and in ampules by 1 ml of 0.5% solution, midazolam in ampules — by 3 ml of 0.5% solution, flunitrazepam in tablets — 2 mg and in ampules — 1 ml of 0.2% solution. Effect of benzodiazepins is conditioned by their binding with specific benzodiazepin receptors it intensifies GABA-ergic inhibition of nerve cells. Its inhibitory effect on CNS is dose-dependent. Sedative doses are accompanied by anterograde amnesia, inhibition of consciousness is less profound, but more prolonged than in barbiturates, and it does not ensure absolutely an analgesia. They decrease an oxygen demand of the brain, cerebral blood flow and ICP, but less than barbiturates, prevent and control fits of convulsions. They are easily absorbed in peroral intake, and midazolam — in intramuscular administration, all are infused intravenously, in which connection diazepam and flunitrazepam irritate venous walls, therefore, it is recommended to administer them into major veins and slowly. 90-98% of them is bound with proteins. They penetrate easily hematoencephalic barrier. The action comes in 1-3 min following intravenous, in 15-30 min after intramuscular and in 30-60 min after peroral administrations. A dose-dependent duration of action is from 15 min to 3-4 hours. In the liver diazepins conjugate with glucuronic acid, however, so formed glucuronides continue to exert their effect, retaining in the organism from 2 hrs in case of midazolam and to 30 hrs in diazepam administration. They are applied for sedation (diazepam intravenously 0.04-0.2 mg/kg, midazolam — 0.1-0.4 mg/kg, flunitrazepam 0.015-0.03 mg/kg), for premedication (diazepam per os 0.2-0.5 mg/kg, midazolam intramuscularly 0.07-0.15 mg/kg, flunitrazepam per os 12 mg/kg) and for initial narcosis (diazepam intravenously 0.3-0.6 mg/kg, midazolam 0.1-0.4 mg/kg). In order to maintain anesthesia repeated administrations are made depending on clinical signs of the deepness of anesthesia, on the average, diazepam 0.2-0.5 mg/kg and midazolam — 0.05-0.2 mg/kg. Side effects: diazepam, insignificantly, and midazolam, more markedly, decrease TPVR, cardiac output and AP, but HR sometimes increases. In intravenous injection they, diazepam in particular, inhibit respiration and may cause apnea in case of fast administration. They act as CNS myorelaxants. The principal and side effects of diazepins become more intense in their combination with other CNS depressants. It is necessary to decrease dosages in hypothermia, cachexia, and in elderly patients. Contraindications: hypersensitivity to diazepins, myasthenia gravis, intake of alcohol, hypnotics and agents used for treating neuropsychic diseases (neuroleptics, antidepressants, lithium), do not apply under out-patient conditions, in cesarean section prior to umbilical ligation. Дата добавления: 2015-02-05 | Просмотры: 771 | Нарушение авторских прав |
