The purpose of this study was to clarify the effect of general anesthesia on blastogenesis of lymphocytes in dogs. Lymphocytes collected from the anesthetized dog were incubated with concanavalin A (Con A) or phytohemaggulutinin (PHA) mitogen. Blastogenesis of lymphocytes stimulated by these mitogens were evaluated by the stimulation index (S.I.) from the incorporation of³H-thymidine. In halothane anesthesia (GOF) group, each dog was induced anesthesia by mask inhalation of 4% halothane and maintained by 1% halothane through a tracheal tube for 2 hrs (Group A) . A significant decrease in S.I. value was indicated from 24 hrs to 4 weeks and the lowest value was recorded at 2 weeks after the anesthesia. In pentobarbital anesthesia group, receiving at a dose of 25 mg/kg intravenously (Group B), the lower values compared to those of pre-anesthesia were recognized at 24 hrs and 2 weeks after the anesthesia. The suppressive effect on blastogenesis of peripheral lymphocytes of halothane anesthesia was stronger than that of the pentobarbital anesthesia.

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The influence of repeated injections of ketamine hydrochloride was studied using 12 dogs. They were anesthetized a total of 10 times. They were injected intervenously every three days. Six dogs were injected with 5 mg/kg each time. The other six were injected with 10 mg/kg each time.
The following results were obtained : Dogs of both groups seemed to develop a tolerance to this agent for the following three reasons. 1. The time needed to recover their pain sensation, 2. the time needed for rising, 3. the time needed for ambulation steadily decreased throughout the testing period. Blood pressure, heart rate, respiration rate and body temperature were not affected by the repeated anesthesia, and no serious side effects were encountered. Dogs remained in good health throughout the experimental study. It seems likely that the risk of repeated injections with ketamine is minimal but we must take into account the development of a tolerance to the agent and the number, frequency and dose of the dosages.

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After preanesthesia using atropine sulfate (0.01 mg/kg, IM) and diazepam (0.2 mg/kg, IM), and induction of anesthesia using xylazine hydrochloride (1 mg/kg, IM) and ketamine hydrochloride (7 mg/kg, IM), a young steller sea lion was maintained with inhalation anesthesia using oxygen-halothane mixture to ophthalmectomize. During the surgery, the sea lion was sufficiently sedated. Recovery from the anesthesia was prolonged despite of administrations of tolazoline hydrochloride as an antagonist to xylazine hydrochloride. It seemed that the sea lion entered a dive response during the recovery.

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