Experimental urethane anaesthesia prevents digoxin intoxication: electrocardiographic and histological study in rabbit.

An electrocardiographic and histological study was performed in rabbit to detect the effects of urethane (ethyl carbamate) intraperitoneal (i.p.) anaesthesia in digoxin intoxication, since it has been previously shown that this anaesthetic and digitalis glycosides exert specific peripheral effects on the cardiovascular system involving central structures of the autonomic nervous system. We observed that i.p. urethane anaesthesia prevented the onset of the electrocardiographic signs of digitalis intoxication, as well as inhibiting the appearance of histological myocardial alterations after treatment with toxic digoxin doses. On the other hand, lethal arrhythmias and severe myocardial damage were observed in animals that had not undergone preliminary urethane anaesthesia. These results indicate that the effect exerted by urethane in preventing the toxic action of digoxin is probably due to a decrease of sympathetic activity in anaesthetized animals by centrally mediated sympathetic inhibition.

Serum and intracellular magnesium concentrations in intoxicated chronic alcoholic and control subjects.

Serum magnesium levels may not accurately reflect overall magnesium homeostasis. To clarify the relationship between serum and intracellular magnesium concentrations in chronic alcoholism, we determined intralymphocytic magnesium levels and serum magnesium, sodium and potassium concentrations in ten chronic alcoholic subjects admitted to the emergency room during acute ethanol intoxication, and compared the results to those of 14 healthy nonalcoholic controls. Serum magnesium, sodium and potassium concentrations were within the normal range in both groups of subjects and determination of intralymphocytic magnesium levels revealed a nonsignificant decrease in alcoholic subjects compared to controls. In conclusion, serum and intralymphocytic magnesium concentrations did not differ between chronic alcoholics and controls in our population; the results of the present study do not support the practice of routine magnesium administration to chronic alcoholics in the emergency room setting.

Role of the parasympathetic autonomic nervous system in digitalis intoxication: electrocardiographic and histological study.

The role of the parasympathetic autonomic nervous system (ANS) in digoxin intoxication was investigated in atropine pretreated conscious rabbits. Both the electrocardiographic registration and the histologic analysis indicated possible prevention of lethal arrhythmias by atropine pretreatment. The hearts of animals pretreated with atropine appeared less damaged, since they presented only a light cytoplasmic vacuolization. It was evident that the administration of digoxin without atropine pretreatment provoked dramatic signs of digitalis intoxication followed by animal death. Myocardia of these rabbits were highly damaged. On the other hand, our experimental data indicated that the abolishment of the vagal tone by atropine blockade caused only signs (i.e. inversion of the T wave) due to myocardial ischemia, to which the light cytoplasmic vacuolation could be correlated. Myocardial ischemia could be caused by constriction of coronary blood vessels, which could be consequential to both the prevalent activity of the orthosympathetic ANS, following parasympathetic blockade, and direct digoxin effects on vascular fibrecells, which both produce vasoconstriction. Therefore, it is reasonable to assume that the parasympathetic ANS plays a major role in digitalis intoxication in rabbits.

Differential effects of disuse preceding denervation on the onset and development of fibrillation in fast and slow muscles.

Section of the sciatic nerve, performed after a week of muscular disuse, is followed by fibrillation earlier in the soleus (S) than in the anterior tibialis (AT) muscle of the rat. The subsequent development of fibrillation, which is different in the control denervated S as compared with the control denervated AT, tends to become similar in the disused-denervated muscles.