J.Jpn. Surg. Soc.. 62(1): 102-119, 1961

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EXPERIMENTAL STUDY ON HEMODYNAMICS DURING HYPOTHERMIC ANESTHESIA

Using 38 rabbits, hemodynamic changes on hypothermia were studied under various anesthetic conditions. Hypothermic anesthesia was performed as the following groups; 1st group non anesthetic as a control, 2nd group light ether anesthesia (1.5-2 cc of ether /kg of body weight), 3rd group deep ether anesthesia (3-4 cc/kg) and 4th group ether combined ganglionlytic (ether 1.5-2 cc/kg and cocktail M₁ 1 mg/kg). Under these anesthetic conditions, hypothermia was induced by immersed method to 20°C and mesenterial circulation was observed microscopically and blood pressure, cardiac output (by modified dye dilution method), total peripheral resistance and mean circulating time were measured. Perfusion of rabbit's ear were performed in either isolated or preserved nerve innervated ear, in order to observe behaviour of superficial blood vessel for direct cooling. Results were as follows.
I. Hemodynamics of peripheral circulation
a) Mesenterial circulation
1) Blood pressure increased at the initial phase of cooling and decreased at degree of lowering temperature and easy decreased during deep anesthesia.
2) Rate of blood circulation was observed in parallel change of blood pressure and difficult to decrease at light anesthesia.
3) There were scarcely change of diameter of the arteriole or venule in the 3rd and 4th group, decreased diameter at the beginning of cooling phase in the 1st group, tend of increased diameter at all hypothermic process in the 4th group.
4) Capillary flow was restricted initially and then no restriction incur at the certain temperatures in the various groups. Temperatures were observed 22°C of the 1st group, 24°C of the 2nd group, 27°C of the 3rd group and finally the 4th group was not restricted at any time at all and showed circulatory failure due to high peripheralisation at about 20°C.
5) All changes at this period of cooling were recovered at rewarming process except for non-anesthetic group.
b) Perfusion of rabbit's ear
There were decreasing perfusion in lowering temperature with isolated ear, on the contrary, with nerve preserved ear did not interfere by lowering temperature.
II. Central hemodynamics
1) Cardiac output decreased 40-20% at 20°C and delayed recovery in rewarming phase is observed. There were little differences with various anesthetic conditions.
2) Total peripheral resistances were observed temporalily increase at 27°C and tend to decrease at 20° with the 3rd or 4th group and increase constantly with the 1st or 2nd group.
3) Mean circulating time was delayed by lowering process, shortened by rewarming period.
By these experimental results, the author confirmed that there was a tendency of centralisation above 25°C, peripheralisation below 25° C.
The author pressumed that deep ether anesthesia was the best choice with hypothermic anesthesia because of difficulty to control shivering with light anesthesia or hazardous circulatory failure of usieg ganglionplegics.
(Author's abstract)

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