On the muscular rigidity and hyperreflexia due to hypothermia in man with observations on the accommodation of peripheral nerve.

Before the development of controlled hypothermia as a therapeutic measure in man little was known of the effects of prolonged lowering of the body temperature in the human subject. The pioneering work of Smith and Fay (1940) and of Talbott (1941, 1944) in the use of refrigeration for the treatment of malignant disease, schizophrenia, and intractable pain has found little support and the technique is now most widely used as a means of lowering metabolism during surgical operations (Lewis and Taufic, 1953). The earlier work enabled studies to be made on the conscious subject in conditions suitable for observation. The effect of progressive hypothermia on the human nervous system was described by Davis (1940), Fay and Smith (1941), and Dill and Forbes (1941). A striking feature of these reports was the hyperreflexia and muscular rigidity shown by the majority of patients at a particular range of temperatures. These authors were unable to give a satisfactory explanation of this phenomenon. This paper reports observations on a case of spontaneous hypothermia which suggest a possible mechanism. The clinical picture of progressive hypothermia is described by Fay and Smith (1941) in a report based on a study of 42 patients who were treated by controlled cooling for various malignant diseases. In three patients, in whom spinal anaesthesia was used during the early stage of refrigeration, cerebration was progressively delayed with the reduction of body temperature. Mental faculties were fairly well preserved until the body temperature approached 930 F. but there was retrograde amnesia for the period during which the body temperature remained below 920 F. Dysarthria began at approximately 930 F. and response to the spoken word became practically nil below 800 F. Pain present before refrigeration was completely relieved in all but 4-7%' of the 42 cases but appreciation of pain, heat, and cold was not lost during or after refrigeration as long as consciousness was retained. The pupils remained equal, regular, and normal in size throughIs ouit the hypothermic period, but response to light stimuli became progressively more sluggish as the body temperature was lowered. The light reflex was abolished at 78° F. The psychical and pupillary changes resemble those of pharmacological anaes' thesia and, indeed, it would not be surprising that the cerebrum should cease to function when its metabolism is lowered by cold (Fazekas and Himwich, 1939) in a manner closely resembling the effects of chemical inhibitors of metabolism. An unusual feature, however, compared with chemicat anaesthesia is the retention of muscle tone and the, stretch reflexes. The clinical picture vividly described by Fay and Smith (1941) emphasizes this unique feature:-