Narcotics combined with low flow N₂O-O₂ in open-heart surgery

Dihydroetophine(DHM₉₉)and Fentanyl（F）are potent narcotics.DHM₉₉ was compared with F under nearly closed circuit N₂O-O₂ anesthesia in open-heart surgery,each including 10 clinically similar patients,both groups represented satisfactory results. Induction was started with 2:1 N₂O-O₂ after denitrogenation,either 0.5ug/kg DHM₉₉ or 5 ug/kg F was then administered intravenously.After that,2 mg/kg of Succinycholine was given for tracheal intubation,blood pressure and pulse rate were measured at 1,3,5 and 10 minutes, rate pressure product could also be calculated at the same time. Anesthesia was maintained with nitrous oxide and oxygen,with intermittent intravenous doses of DHM₉₉ or F when necessary during skin incision,sternotomy and electric cautery.For the first hour,N₂O/O₂ flow ratio was maintained at 300 ml/250 ml（60% to 70% N₂O）or 300ml/200ml （50% to 60% N₂O）;while in the next hour,we cut N₂O supply down to 1/2 of the first hour dose.Only oxygen was given during cardiopulmonary bypass,since termination of artificial circulation,no narcotic was administered so as to avoid residue respiratory depression,and 1:1 N₂O/O₂ was restarted up to the end.Post-intubation hemodynamic change within ten minutes seems better in DHM₉₉ than F group（p less than 0.05—0.01）.