[Cardiocirculatory and respiratory effects of the combination of midazolam and ketamine].

This study summarizes our results with various ataralgesic combinations and their effects on circulation and respiration. Together with the new water-soluble 8-chloro-6-(2-fluorophenyl)-1-methyl-4H-imidazo[1,5-a][1,4]benzodiazepine midazolam, Ro 21-3981, Dormicum), 7-chloro-1,3-dihydro-1-methyl-5-phenyl-(2H)1,4-benzodiazepin-2-one (diazepam) and 5-(o-fluorophenyl)-1,3-dihydro-1-methyl-7-nitro-2H-1,4-benzodiazepin-2-one (flunitrazepam) are also considered, for the purpose of comparison. Pharmacokinetic studies confirm the clearly shorter duration of action of midazolam. The poor respiratory depressant action of the benzodiazepines can be easily and rapidly increased by premedication, ataralgesic combinations and substances for the prolongation of anaesthesia. Adequate spontaneous respiration is possible only in exceptional cases. The threshold doses for 100% suppression of cardiac stimulation due to 2-(o-chlorophenyl)-2-methylaminocyclohexanone (ketamine) were determined for all three benzodiazepines. These doses are also valid for hypertension. The effect of intubation is not suppressed by the ataralgesic combination alone, whereas it does suppress the increase in pressure in the pulmonary circulation which is synchronous with the systemic blood pressure. The rise in intracranial pressure following ketamine alone is also prevented by premedication with benzodiazepines, which on the other hand offer no protection against certain other effects (hypoxia, hypercapnia, intubation), The same is true for increases in intraocular pressure. According to the results of investigations carried out, the new benzodiazepine midazolam justifies our hope for a substance with a similar basic effect, but with a clearly improved pharmacokinetic profile.