Effect of dichloroacetate in the treatment of anoxic lactic acidosis in dogs

The pharmacology of dichloroacetate

Dichloroacetate (DCA) exerts multiple effects on pathways of intermediary metabolism. It stimulates peripheral glucose utilization and inhibits gluconeogeneis, thereby reducing hyperglycemia in animals and humans with diabetes mellitus. It inhibits lipogenesis and cholesterolgenesis, thereby decreasing circulating lipid and lipoprotein levels in short-term studies in patients with acquired or hereditary disorders of lipoprotein metabolism. By stimulating the activity of pyruvate dehydrogenase, DCA facilitates oxidation of lactate and decreases morbidity in acquired and congenital forms of lactic acidosis. The drug improves cardiac output and left ventricular mechanical efficiency under conditions of myocardial ischemia or failure, probably by facilitating myocardial metabolism of carbohydrate and lactate as opposed to fat. DCA may also enhance regional lactate removal and restoration of brain function in experimental states of cerebral ischemia. DCA appears to inhibit its own metabolism, which may influence the duration of its pharmacologic actions and lead to toxicity. DCA can cause a reversible peripheral neuropathy that may be related to thiamine deficiency and may be ameliorated or prevented with thiamine supplementation. Other toxic effects of DCA may be species-specific and reflect marked interspecies variation in pharmacokinetics. Despite its potential toxicity and limited clinical experience, DCA and its derivatives may prove to be useful in probing regulatory aspects of intermediary metabolism and in the acute or chronic treatment of several metabolic disorders.

Effects of various doses of sodium dichloroacetate on hyperlactatemia in fed ischemic rats

In shock, the presence of hyperlactatemia is prognostic of a failure to survive. An experimental model of stroke that combines bilateral carotid ligation and bleeding to a mean arterial pressure of 50 mm Hg induces hyperlactatemia like that associated with tissue hypoperfusion of hemorrhagic shock. In previous nonsurvival studies with this model, post-ischemic treatment of fed rats with 25 mg/kg of sodium dichloroacetate (DCA) was effective in lowering brain tissue lactate but did not significantly affect the ischemia-induced increase in serum lactate measured after 30 minutes of ischemia followed by 30 minutes of reperfusion. Investigators using other animal models treated hyperlactatemia associated with tissue hypoperfusion successfully with a DCA dose of more than 25 mg/kg. Our goal was to determine the effect of a higher dose of DCA on serum lactate in the model of cerebral ischemia with systemic hypotension that we had used in previous studies. The previously unstudied dose-response also was evaluated in our study. Rats that had been fed ad libitum were assigned randomly to either a real or sham (control) ischemic group. Immediately after 30 minutes of ischemia and subsequent reinfusion of blood or after 30 minutes of sham ischemia, rats received DCA (0, 25, 50, 100, 200, or 300 mg/kg). Comparisons were made of blood values measured at the end of equilibration before ischemia, after 30 minutes of ischemia, and after 30 minutes of reperfusion. All ischemic rats were hyperlactatemic. Serum lactate levels were not correlated to blood glucose elevation during ischemia. After treatment in both control and ischemic rats, the percentage decrease in serum lactate varied as a logarithmic function of the DCA dose administered. Glucose levels and pH were not affected by DCA treatment at any dose. Because acidemia decreases lactate uptake by the liver, values for acidotic rats were compared with those for nonacidotic rats. Whereas lactate in acidotic rats decreased significantly only when treated with DCA, nonacidotic rats evidenced this decrease regardless of whether they received DCA. We discuss the relationship of these findings to the peak levels of lactate achieved, the resolution of hyperlactatemia, and factors that affect the interpretation of data in therapeutic studies using DCA.

Effects of dichloroacetate following canine asphyxial arrest

Sodium dichloroacetate (DCA) has been shown to lower elevated serum lactate levels produced by hypoxia, exercise, and phenformin. We conducted a study to investigate the effect of DCA treatment on lactic acidosis following resuscitation from asphyxial cardiac arrest. Conditioned dogs were anesthetized with pentobarbital (30 mg/kg), endotracheally intubated, and mechanically ventilated to maintain an arterial pCO2 of 30 to 40 mm Hg. Asphyxial cardiac arrest was produced by endotracheal tube occlusion for six to eight minutes. After five minutes of cardiac arrest, the endotracheal tube was unclamped and closed-chest CPR was begun. Six animals received DCA 100 mg/kg IV push after one minute of CPR. Control animals (n = 6) received an equal volume of saline. CPR was continued until the return of a spontaneous pulse, when mechanical ventilation was resumed. Arterial and venous blood gases, glucose, and lactate levels were obtained at baseline and 15, 30, 45, 60, 90, and 120 minutes after resuscitation. Mean arterial blood pressure, pulse, and glucose, and venous and arterial blood gases were similar in both groups throughout the study. By 45 minutes after resuscitation, the DCA-treated group showed a significantly faster rate of decline in lactate levels that continued to the final sampling period. By 90 minutes, arterial lactate in DCA animals was not significantly different from baseline (pre-arrest) values. DCA given during cardiac arrest will cause a more rapid normalization of arterial lactate after successful resuscitation. Further studies are needed to evaluate the effects of lowered lactic acid on survival and neurological outcome following cardiac arrest.