Part V 



PROBLEMS IN METHODS OF INDUCING HYPOTHERMIA 

 BY EXTERNAL COOLING 



\\ ILLIAM H. MULLI'.R, JR. and J. FRANCIS DAMMANN 



Ideally, a method lor lowering body temperature should be simple, inexpensive, 

 readily availal)le, should permit one to cool at various rates with accurate control 

 and should allow one to re warm the subject without having to make extensive al- 

 terations in the apparatus. The methods in current use for inducing hypothermia 

 l)y external cooling will be reviewed from these standpoints. 



Immersion in cold ivater. This technique has been one of the most popular to 

 date. It consists of Ijringing a tub partially filled with water and crushed ice into 

 the operating room and immersing the patient in it. The temperature of the media 

 is in the neighborhood of 4° C. and cooling is accomplished rapidly. Swan,^-- 

 Bigelow,^ Hegnauer/' ° and others have used it in preference to other methods. Its 

 advantages are that it is simple, rapid, inexpensive, and readily available. The cold 

 medium is evenly distributed over the body surface and makes cooling more uni- 

 form. Its disadvantages are that it is somewhat cumbersome, the patient must be 

 moved from the tub to the operating table which, in the anesthetized state, can be 

 accomplished but presents greater difficulties than when the patient is cooled on the 

 table. Cooling must be virtually complete at the time the patient is positioned on 

 the operating room table unless other adjunct means are available to drop the tem- 

 perature to lower levels if desired. Another disadvantage is that if cardiac arrest 

 should occur diu-ing the cooling period the patient would probably have to be moved 

 from the tub to the operating table before cardiac resuscitation measures could be 

 begun. 



Application of ice bags. This method has been used extensively by Bigelow;,'' 

 Shumacker," Kaplan,® and Scott'' (fig. 1). It is simple, inexpensive, and readily 

 available. It allows one to begin the operation before the desired temperature level 

 is reached. This method also distributes the cooling medium over a relatively large 

 surface which is desirable for rapid cooling. The disadvantages are that accurate 

 control of the temperature is lacking. This is especially true if one begins the 

 operation before the maximum temperature drop is reached and leaves the patient 

 on a bag of ice during the beginning of the operation. When the bag is removed, 

 the underlying sheets and mattress are often wet and cold and the temperature may 

 continue to drop for a period of time in excess of the expected drift. The plastic 

 bags often develop leaks and as the ice melts water accumulates and makes the 

 operating area messy. One of the more serious disadvantages is that fat necrosis 

 has developed in infants cooled by this method. Collins, Spellman, and Scott, ^ who 

 first reported this complication, noted that the chemical composition of fat in the 



415 



