[The effects of neuroleptanalgesia on the sympathetic activity and the circulation in animals (author's transl)]

Abstract

The effects of i.v. injected Fentanyl and droperidol used either singly or in combination were observed in 50 experiments carried out on cats which had been relaxed and artificially respirated. The preganglionic discharges of the cervical sympathetic nerve and action potentials of the phrenic nerve, the mean arterial pressure and the heart rate were recorded. The experiments showed that with the dosage of 0.0042-0.0083 mg/kg Fentanyl no significant change in the recorded functions took place. The dosage of 0.0166 mg/kg Fentanyl led to an activation of the central sympathetic activity and to a inhibition of the respiratory centre which persisted for as long as 60 min after the injections. Other than as above, a dosage of 0.15-0.6 mg/kg droperidol led to a decrease of the blood pressure and a depression of the sympathetic nerve activity, while the activity of the phrenic nerve remained unchanged. The effect on the blood pressure was mainly influenced by the central nervous system as the inhibition of the pressor effect of noradrenaline was only minimally. The dosage of 0.0083 mg/kg Fentanyl combined with 0.3 mg/kg dropendol as administered for neuroleptanalgesia led to a decrease in blood pressure and a depression of the central sympathetic and phrenic nerve activity both in rest and in stress during asphyxia. The effects were minimal and accorded virtually to the effects produced by 0.5 vol-% Halothane during the first 25 min of inhalation, which had been registered in previous experiments. Contrary to the effects of Halothane, neuroleptanalgesia produced no decrease in the heart rate, no depression on the pressor effects of noradrenaline and no accumulation of irregularities in cardiac rhythm after administration of noradrenaline.