The use of dichloroacetate in the treatment of overwhelming hypoxic acidosis

Clinical use of plasma lactate concentration. Part 2: Prognostic and diagnostic utility and the clinical management of hyperlactatemia

OBJECTIVE

To review the current literature pertaining to the use of lactate as a prognostic indicator and therapeutic guide, the utility of measuring lactate concentrations in body fluids other than blood or plasma, and the clinical management of hyperlactatemia in dogs, cats, and horses.

DATA SOURCES

Articles were retrieved without date restrictions primarily via PubMed, Scopus, and CAB Abstracts as well as by manual selection.

HUMAN AND VETERINARY DATA SYNTHESIS

Increased plasma lactate concentrations are associated with increased morbidity and mortality. In populations with high mortality, hyperlactatemia is moderately predictive in identifying nonsurvivors. Importantly, eulactatemia predicts survival better than hyperlactatemia predicts death. Consecutive lactate measurements and calculated relative measures appear to outperform single measurements. The use of lactate as a therapeutic guide has shown promising results in people but is relatively uninvestigated in veterinary species. Increased lactate concentrations in body fluids other than blood should raise the index of suspicion for septic or malignant processes. Management of hyperlactatemia should target the underlying cause.

CONCLUSION

Lactate is a valuable triage and risk stratification tool that can be used to separate patients into higher and lower risk categories. The utility of lactate concentration as a therapeutic target and the measurement of lactate in body fluids shows promise but requires further research.

Hyperlipidemia with hypoglycemia reduces myocardial oxygen utilization efficiency but not contractile function during coronary hypoperfusion

This study was designed to determine changes in myocardial contractile function and fuel selection during moderate coronary hypoperfusion in the presence of elevated plasma free fatty acid (FFA) at normal and reduced blood glucose concentrations. Coronary perfusion pressure (CPP) was sequentially lowered from 100 to 60, 50, and 40 mmHg in the left anterior descending coronary artery (LAD) of anesthetized, open-chest dogs. Regional glucose uptake (GU), fatty acid uptake (FAU), percentage segment shortening (%SS), and oxygen consumption (MV O(2)) were determined with normal arterial plasma FFA concentrations (Group 1) or with elevated FFA concentrations (Groups 2 and 3). In Group 3, glucose in the coronary perfusate blood was reduced from 3.53+/-0.36 to 0.15+/-0.03 m M by hemodialysis. In Group 1, FAU fell by 85% as CPP was lowered to 60 mmHg and remained depressed as CPP was reduced further; GU did not fall significantly. Hyperlipidemia in Group 2 did not alter GU at any CPP, but maintained FAU at baseline levels until CPP was lowered to 40 mmHg. At 40 mmHg CPP, myocardial function and metabolic variables were similar in Groups 1 and 2. In Group 3 at 40 mmHg, FAU increased four-fold and MV O(2)doubled v Groups 1 and 2, and GU fell to zero. Despite these metabolic changes, %SS in Group 3 was unchanged relative to Group 2. Addition of glucose to the dialysate prevented the effects of dialysis on FAU, GU, and MV O(2). Thus, preferential glucose oxidation sustains myocardial oxygen utilization efficiency [(heart rate x %SS x maximum left ventricular pressure)/MV O(2)] during hypoperfusion. Blocking preferential glucose oxidation by combined hyperlipidemia and hypoglycemia lowers oxygen utilization efficiency, but does not compromise myocardial contractile function.

Dichloroacetate enhances myocardial functional and metabolic recovery following global ischemia

This study was undertaken to determine the effect of dichloroacetate (DCA) on myocardial functional and metabolic recovery following global ischemia. Sixteen isolated rabbit hearts were subjected to 120 minutes of mildly hypothermic (34 degrees C) cardioplegic arrest with multi-dose, modified St. Thomas' cardioplegia. Following ischemia, hearts were reperfused with either a physiologic salt solution (PSS) as controls, (CON, N = 10), or PSS containing DCA (DCA, N = 6) at a concentration of 1 mmol/L. Functional and metabolic indices were determined at baseline and at 15, 30, and 45 minutes of reperfusion. Results were analyzed using analysis of variance (ANOVA, Sheffe F test) and significance was defined as P < 0.05. Functional recovery was significantly better in hearts reperfused with DCA. Developed pressure (DP) recovered to 62 +/- 4% of baseline in DCA hearts, compared to 37 +/- 8% in CON hearts. Recovery of dP/dt was also improved in DCA versus CON hearts (67 +/- 5 v 43 +/- 10%). Coronary blood flow was not different between groups either at baseline or during reperfusion, but myocardial oxygen consumption (MVO2) was increased in the DCA versus CON hearts (71 +/- 10% of baseline, v 51 +/- 19%). Diastolic compliance during reperfusion was improved in those hearts receiving DCA, as was myocardial mechanical use efficiency (DP/MVO2). Correction of myocardial tissue pH to baseline values was similar in both groups, indicating that the beneficial effect on functional recovery seen with DCA was not solely related to amelioration of acidosis.(ABSTRACT TRUNCATED AT 250 WORDS)