Studies on the physiology of awareness: an oximetric investigation of the anoxaemia accompanying insulin coma therapy.

Abstract

This investigation deals with the measurement, by a peripheral method of discontinuous spectroscopic oximetry, of the arterial blood oxygen saturation levels in a group of schizophrenic patients undergoing insulin coma therapy.The association between tissue anoxia and insulin hypoglycaemia was first established by Campbell and Dudley in 1924. Dameshek and Meyerson (1935), using the arterio-venous oxygen difference method with the internal jugular vein as the source of venous blood, showed that the injection of insulin in coma doses was accompanied by an anoxaemia in the schizophrenic patients they studied. This work was confirmed by Himwich, Bowmanet al.(1939), and in another paper Himwich (1951, p. 277) and his co-workers found that the correlation of progressively developing clinical symptoms with the decrease of cerebral oxygen uptake was a closer one than the correlation with the more acute fall in the blood-sugar curve. An important symptomatic aspect of insulin hypoglycaemia includes the progressive changes in the levels of consciousness accompanying the approach towards coma. Wilder (1943) has outlined some of these changes, and Frostig (1940) and Himwich (1951, pp. 258-265) have delineated these awareness thresholds and discussed their relationship to the Hughlings Jackson theory of the phyletic organization of the central nervous system. Thus, during thefirst hourfollowing insulin injection, somnolence and lassitude appear to be associated with suppression of cortical and cerebellar activity; in thesecond hourfurther clouding of consciousness, sometimes with excitement, perceptual disturbances, periods of confusion, exacerbations of previously existing hallucinations and latent psychotic syndromes are seen; in thethird hourmotor restlessness and loss of consciousness suggest the release of basal ganglia and hypothalamus; in thefourth hourdeepening stupor and depression of exteroceptive sensitivity indicate a probable release of the midbrain and suppression of pyramidal function; in thefifth hourthe deep pre-mortal coma presages medullary release. Similarly, it is with awareness changes that many workers prefer to diagnose the “real coma” level in a patient under treatment. Thus Sakel (1937) held that coma was to be diagnosed when no further personal contact with the patient was possible, and Kalinowsky and Hoch (1946) agree that the real coma level is reached when it is completely impossible to awaken the patient.