DRUGS AND INTERNAL COOLING— DAAIMANN and MULLER 427 



much smaller volume of hlood. This makes a smaller, cheaper and more efficient 

 machine possible. At low temperatures, the normal ckjtting- mechanism is inter- 

 fered with. Consequently, when the pnui]) is in use, a much lower heparin dosage 

 can he used. Hemolysis of hlood in the tubing of the pump is reduced by the reduc- 

 tion of temperatures. A reduction in hlood flow means a reduction in coronary cir- 

 culation and therefore a reduction in the amount of blood that enters the operative 

 field from the coronary sinus. Finally, a pump-oxygenator is a man-made machine 

 It is, therefore, subject to breakdown. If a breakdown does occur when the tem- 

 perature of the patient is low, the low metabolic rate permits more time for repair. 



The final method of cooling which we will discuss involves the use of the French 

 lytic cocktail,"' ** either alone or in combination with external cooling. The basic 

 ingredients of the French lytic cocktail are Thorazine and Phenergan. Both drugs 

 belong to the generic group phenothiazine. Thorazine is primarily a central nervous 

 system depressant. It is a mild antispasmodic, antihistaminic and adrenolytic drug. 

 It is alleged to potentiate hypnotics, sedatives, narcotics, anesthetics, alcohol and 

 antispasmodics. It may potentiate carbon dioxide narcosis. It produces sedation, 

 probably by interrupting impulses passing between the diencephalon and cerebral 

 cortex. It is not a hypnotic and does not produce addiction. Its value in hypothermia 

 is that it blocks the thermo-regulating mechanism, thus permitting a closer approxi- 

 mation of body temperature to environmental temperature. Phenergan is a strong 

 antihistaminic but a poor antithermic. One of its chief effects is decreasing capillary 

 permeability. When these two drugs are used in combination with a small dose of 

 Demerol, a state of drowsiness is produced. The normal body response to the appli- 

 cation of ice is greatly inhibited. The peripheral vasoconstriction constituting the 

 body's first line of defense against cold is markedly reduced and shivering, the 

 second line of defense, is minimized. Thus, the patient can be cooled more rapidly. 

 In experimental work. Dundee^- found that shivering could be controlled equally 

 well with deep anesthesia, curare, or Thorazine. Angus Smith*"^ used the lytic cock- 

 tail without additional external cooling and noted a drop in temperature to 95° F. 

 In America, Ripstein^*' has combined the use o"f Thorazine with a cooling blanket. 

 Temperature is reduced to 83 in about an hour and a half. The patient is first 

 anesthetized and placed on a refrigeration blanket. A 50-mg. dose of Thorazine is 

 given intravenously, followed by 100 mg. intramuscularly. Then, 50 mg. are 

 given every one to two hours during the procedure and for rewarming. Dr. Ripstein 

 feels that the chief advantages of this technique are a more rapid fall in temperature 

 and the avoidance of shivering without the use of curare or a heavy anesthetic. 



It is difficult to assess the advantages and disadvantages of the French lytic cock- 

 tail. Most workers in this country have avoided use of the cocktail because Thora- 

 zine and Phenergan are potent drugs with diverse pharmacologic effects. The dosage 

 is variable. The degree to which hypnotics and barbiturates are potentiated varies. 

 Since the hazards of hypothermia still have not been thoroughly elucidated and 

 controlled, it seems unwise to add to the difficulties potent drugs, the actions of 

 which are not clearly understood. 



REFERENCES 



L Bigelow, W. G., Hopps, J. A., and Callaghan, J. C. : Radio frequency rewarming in resusci- 

 tation from severe hypothermia, Canadian J. Med. Sciences 30: 185, 1952. 



