Observations on EEG changes during anaphylactic shock

For the study of pathogenesis of anaphylactic shock, we had carried out observations on EEG patterns of normal rabbits, rabbits in anaphylactic shock caused by horse serum, and rabbits in hemorrhagic shock. The main findings are as follows: (1) The EEG of 46 normal rabbits fell into three groups: (i) the waking type characterized by fast waves with low amplitude found in 30 rabbits; (ii) the sleeping type giving patterns of slow waves with high amplitude and spindles observed in 11 rabbits; (iii) the mixed type presenting alternate waking and sleeping patterns shown by 5 rabbits. (2) The EEG during the course of anaphylactic shock induced in 15 rabbits showed phasic changes, beginning with a phase of excitement followed by one of inhibition, ending in complete disappearance of the waves. In two rabbits which eventually recovered from the state of shock, their EEG gradually regained the normal features. (3) The EEG changes during the course of hemorrhagic shock in 7 rabbits were similar to those in anaphylactic shock. This similarity indicates that the EEG changes in both cases are merely correlated with changes in blood pressure: the phase of excitement occurs as the blood pressure begins to fluctuate at large amplitude and the phase of inhibition appears most often during the development of hypotension. When the blood pressure falls below 20—66 mm Hg, the electrical activity of the brain disappears entirely.