Cardiac Hypoxia

Bassett, Bigger and Hoffman, The Journal of Pharmacology and Experimental Therapeutics (1970),804 reported that PHT protected canine Purkinje fibers during hypoxia. Purkinje fibers in isolated heart preparations were stimulated electrically at a constant rate, and the electrical responses were measured until optimal performance was established. Then hypoxia was induced by perfusion with a nitrogen-carbon dioxide mixture, resulting in a sharp reduction in electrical response. During hypoxia, PHT improved electrical response, as measured by phase zero Vmax PHT also improved electrical response when the Purkinje fibers had already been depressed by hypoxia. The authors suggest that the protective and therapeutic action of PHT on Purkinje fibers may in part explain its effectiveness in suppressing arrhythmias caused by myocardial ischemia and hypoxia.

804. Bassett, A. L., Bigger, J. T., and Hoffman, B. F., Protective action of DPH on canine Purkinje fibers during hypoxia, J. Pharmacol. Exp. Ther., 173: 336-343, 1970.

Aldrete and Cubillos, Anesthesia and Analgesia (1984),2279, 2280 compared the effects of PHT (15 mg/kg), thiopental (40 mg/kg), and placebo on hemodynamic tolerance and survival after severe hypoxia in rabbits. PHT significantly delayed the onset of bradycardia and hypotension compared to thiopental and placebo. Survival was highest (eight of twelve) in the PHT-treated group compared to the thiopental group (three of twelve) and the placebo group in which none survived. See also Anti-anoxic Effects of PHT.

2279. Aldrete, J. A., Cubillos, P., Protection against anoxia by phenytoin and thiopentone in rabbits, Sixth Eur. Congress of Anaesthesiology, 248, Sept. 8-15, 1982.
2280. Aldrete, J. A., Cubillos, P., Phenytoin improves hemodynarnic tolerance and survival after severe hypoxia, Anesth. Analg., 63: 1021-4, 1984.