[Low concentration enflurane anesthesia and local administration of epinephrine in rat. Comparison between the lidocaine group and the distilled water group].

Abstract

In the surgical operation for oral region, local anesthetic agent added with epinephrine is usually given to the site to be operated in order to obtain better hemostatic effect even under general anesthesia. However, there have been relatively few reports, which describe the circulatory changes after the injection into oral region, the fluctuation of plasma catecholamine concentration and the concentration of local anesthetic agent in plasma. In the present study, 1% lidocaine or distilled water added with 10 micrograms/ml epinephrine was locally injected at 0.5 ml/kg into the palatal submucosa of Wistar rat under anesthesia with 1% enflurane. With the increase of heart rate and arterial pressure, the catecholamine concentration in arterial blood was determined when heart rate reached the peak value. Further, in the 1% lidocaine group added with 10 micrograms/ml epinephrine, lidocaine concentration was measured under three different conditions of normoventilation, hypoventilation and hyperventilation. Also, for the normoventilation group under 1% enflurane anesthesia, the epinephrine concentration when several events of ventricular arrhythmia occurred and the lidocaine concentration required until the arrhythmia disappeared were measured. The results were as follows: 1. In the case of lidocaine group added with 10 micrograms/ml epinephrine, heart rate and arterial pressure showed less increase than the case of distilled water with 10 micrograms/ml epinephrine, and the time to the peak value of heart rate was shorter. 2. The concentration of plasma epinephrine when heart rate reached the peak value significantly increased compared with the control in both 1% lidocaine group added with 10 micrograms/ml epinephrine, and the distilled water group added with 10 micrograms/ml epinephrine, whereas the increase was more conspicuous in the former than the latter. The concentration of plasma epinephrine at the occurrence of ventricular arrhythmia was by about 2.3 times as much as that of 1% lidocaine group added with 10 micrograms/ml epinephrine when heart rate reached the peak value and by about 5.8 times as much as that of the distilled water group added with 10 micrograms/ml epinephrine. The correlation between plasma epinephrine concentration and the increase of heart rate was noted only in the distilled water group added with 10 micrograms/ml epinephrine. 3. The concentration of plasma norepinephrine when heart rate reached the peak value significantly increased compared with the control only in the distilled water group added with 10 micrograms/ml epinephrine. 4. The concentration of plasma lidocaine when heart rate reached the peak value was about 1/4 of the concentration required for protection against epinephrine-induced ventricular arrhythmia.(ABSTRACT TRUNCATED AT 400 WORDS)