COOLING PATIENTS— LEWIS, RING and ALDEN 397 



mazine is still required. As the body temperature falls below 100° F. the blanket 

 temperature may be increased from its original level of 40-50° F. up to 60 or 70° F. 

 and later, when the body temperature levels off at 95-98° F., the blanket may be 

 warmed a little more. Our objective has been to keep the body temperature within 

 a range of 95 to 98° F. To maintain this level, once it has been reached, a blanket 

 temi)erature of 70 to 80° F. is usually adequate. It is surprising, at first, to find that 

 the blanket at this temperature provides enough cooling in most cases after the first 

 few hours. The blanket is at room temperature and it does not feel ccjid to the 

 touch. It is effective, however, because the entire blanket and consequently a large 

 area of the patient's skin is kept at this temperature due to the constantly circulat- 

 ing fluid in the coils of the blanket. The patient's back feels cool — as cool as the 

 blanket — while in an ordinary bed the back would be hot. 



It is not difficult to decide when cooling is no longer required. Any time the pa- 

 tient's temperature falls below the desired range the circulating pump is turned off 

 and the patient is allowed to rewarm himself slowly. Then, if the body temperature 

 begins to rise slightly above normal again, usually in the afternoon or early evening, 

 the pump is turned back on. Cooling may be required intermittently in this fashion 

 for several days, but finally, if the patient is to recover, it is no longer needed during 

 any part of the day. When the rectal temperature drops below the desired level 

 during cooling it is dangerous to rewarm the patient by heating the blanket above 

 the skin temperature. By hurrying to rewarm the patient this way one is likely to 

 bring the temperature up to a fever level again and the intense cooling and heavy 

 sedation will have to be used once more, as at the l^eginning. It is much better to 

 simply turn off the circulating pump when the temperature drops too low and wait 

 patiently for the patient to rewarm himself. 



Unwanted swings of temperature are avoided ])y watching the rectal temperature 

 continuously so that appropriate changes in the blanket temperature may be made 

 to counteract a slight rise or fall. For this close observation, we have used an 

 electrical thermometer with a temperature sensitive thermistor kept at one position 

 in the rectum. 



Results. Twenty-five seriously ill patients with temperatures of 103° F. or 

 higher have been treated with surface cooling. In most cases the method was em- 

 ployed only after more conventional treatments appeared to have failed. Prior to 

 cooling the prognosis for recovery was poor in each case, and a number of the pa- 

 tients were failing rapidly. In fact, two patients whom we were asked to treat died 

 while we were assembling the equipment. They are not included in the statistics. 

 Of the 25 who were treated, 12 died and 13 survived. One of the 13 survivors died 

 over one month after cooling had been stopped. 



There was a wide range in age (6 to 84 years) but most of the patients were past 

 middle age (median age for the group was 59). The sex distribution was almost 

 equal (13 females and 12 males). 



Each patient had a high body temperature but surface cooling brought it down 

 to normal in every case. Rectal temperatures before treatment were 103° F. or over 

 and the highest temperature was 107° F., in the oldest patient — an 84-year-old man 

 who survived. It took a median time of three hours after cooling had been started 

 to bring the body temperature down to 99° F. Thirty minutes was the shortest 



