[The effects of combining halothane and neuroleptanalgesia on the preganglionic sympathetic activity, the respiratory centre and the circulation (author's transl)].

The effects of Halothane, Fentanyl and droperidol in combination on the circulatory system, the preganglionic sympathetic nerve activity and the respiratory centre were examined in 21 experiments carried out on cats which were relaxed and artificially ventilated with nitrous oxide in oxygen. The results showed that even the minimal dosage of 0.5 vol-% Halothane combined with 0.0042 mg/kg Fentanyl and 0.15 mg/kg droperiodol led to a significant decrease of blood pressure and a depression of the sympathetic and phrenic nerve activity both in rest and in stress during asphyxia. A dosage of 1 vol-% Halothane produced a significant increase in the above mentioned effects when at rest, while the doubled dosage of Fentanyl and droperidol combined with the original Halothane dosage of 0.5 vol-% produced no marked increase in its effects. A comparison of these results with those of previous experiments using only the inhalation of Halothane shows that an anaesthesia consisting of 0.5 vol-% Halothane combined with Fentanyl and droperidol has virtually equal effects on the decrease of blood pressure and on the depression of central sympathetic nerve activity as the inhalation of 1 vol-% Halothane alone. Using a combination of 1 vol-% Halothane, Fentanyl and droperidol the effects induced by 2 vol-% Halothane are reached.