Cardiovascular effects of toxic concentrations of theophylline in the dog

A canine model of theophylline toxicity was used to study the cardiovascular effects seen in severe theophylline poisoning. Eight mongrel dogs were divided equally into two groups. The dogs were anesthetized with pentobarbital and paralyzed with pancuronium bromide. They were ventilated with 100% oxygen and underwent the placement of pulmonary arterial, central venous, femoral arterial, and peripheral venous lines. Group 1 animals received 5.6 mL/kg D5W intravenously (IV) over 20 minutes. Group 2 animals received 140 mg/kg (5.6 mL/kg) of aminophylline IV over the same period. Peak theophylline levels in Group 2 animals averaged 208.9 micrograms/mL. Group 2 animals suffered a marked fall in mean arterial pressure (MAP) and an increase in heart rate. In spite of the fall in MAP (P less than .01), cardiac index actually was increased almost two-fold over Group 1 animals, due mainly to a fall in systemic vascular resistance index (P less than .01). There were no physiologically significant differences in ventricular filling pressures or stroke index between the two groups.