Control of Spontaneous Ventricular Fibrillation during Induced Hypothermia in Cats by Acute Cardiac Sympathectomy

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Abstract
17 adult cats were subjected to cardiac sympathectomy under nembutal anesthesia by bilateral excision of the cervical sympathetic chains between and including the superior cervical and stellate ganglia. Immediately after operation, the anesthetized animals were cooled by submersion in an ice‐water bath. Blood pressure, ECG, rectal temperature and respiration were continuously observed. Angiotensin was administered intermittently to maintain the blood pressure at an adequate level at the lower body temperatures. Artificial respiration was applied when indicated. Under these conditions, only 2 out of 17 denervated animals died in ventricular fibrillation, at 23 and 18.4oC rectal temperature. The remaining animals were cooled to 17.7–15oC and subsequently re‐warmed to normothermia without complications. All of 17 unoperated control animals subjected to hypothermia in the same way developed ventricular fibrillation. Cardiac noradrenaline determined fluorimetrically at the end of the experiments did not differ significantly between the two experimental groups. The results of the present and earlier investigations indicate that hypothermia activates the sympathetic system through a central mechanism and that the cardiac sympathetic nerves represent an important factor for the spontaneous development of ventricular fibrillation, a characteristic complication of induced deep hypothermia in homeothermic mammals.