Measurements of blood-lactate levels help in assessing critically ill patient
Jan 01, 2005
Under aerobic conditions, the intermediate product of glycogenolysis, pyruvic acid, follows an aerobic glycolysis pathway and eventually participates in the Citric-acid cycle or "Krebs cycle" that provides substrates (16 H+) for the oxidative phosphorylation. This oxidative phosphorylation provides a large amount of energy for the cells. Under anaerobic conditions, pyruvic acid follows a different route, the anaerobic glycolysis pathway, and the end-product of this complex cascade of reactions results in accumulation of lactate.
This anaerobic glycolysis provides much less energy for the body compared to aerobic metabolism but represents a necessary effort to provide power for the cells of the body under undesirable conditions, such as hypoxia. After production, lactate is transported to the liver for eventual metabolism. If lactate production exceeds the liver capacity for metabolism, then hyperlactatemia occurs.
The normal resting blood lactate level in dogs is between 1.8 and 22.5 mg/dl or <2.5 mmol/L. In their study of 90 dogs with canine babesiosis, the authors noted that the best predictor of survival was obtained at 24 hours after initiating treatment with antibabesial drugs (and transfusion "as needed"). In this specific study, lactates >40 mg/dl at 24 hours correctly predicted death in every case. Conversely, if the lactate at 24 hours was <40 mg/dl, then the patient always would survive.
There are several options available for the practicing veterinarian to measure blood-lactate concentration. Regardless which method is chosen, plasma-lactate concentration ideally should be measured immediately after venous blood collection. Some methods require collecting whole blood in a potassium oxalate-sodium fluoride "grey-top" tube before assay, while others require "bedside" introduction directly into a cartridge.
In conclusion, serial measurements of blood-lactate levels can be very helpful in the assessment of the critically ill patient. When used in conjunction with serial physical examinations, follow-up lactate determinations can provide valuable information allowing the veterinary clinician to assess the effectiveness of the current therapy and help in prognostication. This can assist the owner in his or her difficult choice between continued treatment or euthanasia in some critical cases.