CONTRIBUTORY FACTORS IN PARATHYROID TETANY IN DOGS

Abstract

Bilateral thyro-parathyroidectomy was performed on 40 dogs. The pH of the blood did not vary appreciably until tetany actually developed. The body temp. rose slowly with the development of fibrillary contractions, and rapidly after the onset of violent tetanic attacks, in extreme instances reaching 44[degree] C. A definite shift toward alkalinity, i.e., increased pH and decreased CO2 tension, of the blood developed as a result of overventilation due to the panting which accompanied the rise in body temp. during the acute attacks. The existing hyper-excitability due to low blood Ca was augmented by increased alkalinity due to panting. These summated conditions might precipitate attacks or markedly intensify attacks in progress. An equivalent or even greater acid-base change accompanying a rise in temp. and panting of otherwise normal dogs did not precipitate tetanic attacks. The acid products of muscular activity during a tetanic attack may temporarily overcome the decreased cH due to overventilation and may thus cause a temporary decrease in the severity of the attack; this phase is followed by an exacerbation of the attack when the increased pH of overventilation again predominates. The augmentation of parathyroid tetany during the inspiratory phase of respiration is confirmed. The important components in the symptom complex after parathyroidectomy in dogs develop in the following sequence: fibrillary muscular contractions, rise of body temp., which in turn causes panting and results in overventilation and increased pH. Violent tetany ensues and further augments the rise of temp. There is thus instituted a vicious cycle which progressively increases the severity of the attack unless relief is obtained by suppression of one or more of the contributory factors.