Electrocardiographic changes on sublethal poisoning of Vacor and Silmurin to Bandicota bengalensis.

A single sublethal dose of Vacor (1 mg/rat) or Silmurin (50 microgram/rat) brought about dissimilar changes in cardiac physiology of bandicoot rats. Delayed myocardial repolarization and stress on cardiac tissues were noticed. Elevation of S-T segment above the isoelectric axis diagnostic of recent myocardial infarction was observed. Vacor and Silmurin induced differential changes in heartbeat; Vacor poisoning resulted in bradycardia, whereas Silmurin tachycardia. It is inferred that Vacor deaths may be due to bradycardia associated with atrioventricular block and that of Silmurin to delayed myocardial repolarization and tachycardia.

Diuresis during fluid infusion : buffer nerve and spinal influences on it.

The rate and cumulative volume of diuresis were measured sequentially for each incremental infusion dose of 5 ml/kg body weight till a 100 ml/kg or more dose was reached. Normal saline (NS), Ringer-Locke (RL) and tender coconut water (TCW) were infused in three groups each of paraldehyde (PLD), and chloralose and urethane (C & U) anaesthetised dogs. The slow infusion rate of about 0.5 ml/kg/min was used. The RL infusion was repeated in vagotomised and/or carotid sinus (CS) denervated dogs and spinal dogs with or without intact vagi. During the NS and RL infusion schedules in PLD anaesthetised dogs produced much less urine than C & U groups. The order of minimum to maximum diuretic effect caused by these fluids were RL, NA and TCW in PLD groups and NA, TCW and RL in C & U groups. The study indicates that the type of anaesthesia and the composition of infusion fluid determines the rate of infusion induced diuresis. PLD anaesthesia has antidiuretic effect, which is not overcome by vagotomy. In C & U anaesthetised dogs the vagotomy and CS denervation performed separately greatly increased the rate of infusion induced diuresis but the diuresis largely decreased when combined surgery was performed. The diuresis in spinal dogs was very low, though in the vagotomised-spinal dogs, the rate of diuresis was more than in the spinal dogs.

Electrolyte changes in plasma and urine during tender coconut water infusion in dogs.

Intravenous infusion of tender coconut water to paraldehyde and chloralose-urethane anaesthetised dogs at a rate of 0.5 ml/kg/min to a total dose of 100 ml/kg body weight decreased serum Na and increased K and Ca levels. Simultaneously, urinary Na excretion decreased and K and Ca excretion increased and there was glycosuria. Serum electrolyte changes were more prominent in paraldehyde anaesthetised dogs.

Vagus stimulation effects during various doses of fluid infusion in dogs.

Stimulation of caudal and cranial ends of vagi in vagotomised chloralose-urethane anaesthetised dogs with 7.5V, 30Cps pulses of 2 msec width after 0, 25, 50, 75 and 100 ml/kg body weight infusion dose of Ringer-Locke solution caused well known effects on heart rate, BP, amplitude of peripheral blood pressure waves, amplitude and frequency of respiration and amplitude of ECG waves. The vagal stimulation effects did not appear to be related to volume of fluid infused into circulation except that caudal end stimulation effect on QRS amplitude was prominent during higher infusion doses while its effect on amplitude of peripheral blood pressure waves and respiration was prominent during lower infusion doses.

Regression pattern of amplitude of electrocardiographic waves during intravenous infusion in intact, buffer nerve denervated and spinal dogs.

Electrocardiographic (ECG) amplitude changes during clinically feasible rate of infusion of normal saline (NS), Ringer-Locke (RL) solution and tender coconut water (TCW) upto a dose of 100 ml/kg in paraldehyde (PLD) and chloralose and urethane (C&U) anaesthetised dogs were studied. The infusion caused a net decrease in P and QRS amplitudes but had varied effect on T wave amplitude in intact PLD and C&U anaesthetised dogs. Infusion of RL in vagotomised and/or carotid sinus (CS) denervated dogs and in spinal dogs indicated that these neural pathways had a significant effect on basal amplitude of ECG waves but their influence on infusion induced ECG changes was only marginal; in this the vagi seem to have a greater influence than the other pathways. The T wave changes during infusion were independent of simultaneous P and QRS changes and appeared to depend on the ionic composition of the infusion fluid. TCW infusion was very well tolerated, particularly by the C&U anaesthetised dogs. It would seem that the evaluation of ECG from patients on parenteral fluid be done in the context of the present observation that infusion per se decreases the amplitude of ECG.