Lactate is a chemical that is a by product of anaerobic metabolism. Animals produce lactate in situations of “hypoperfusion”, an inadequate blood supply to the organs and tissues, or shock. In humans, an increase in serum lactate levels is associated with a poorer prognosis, independent of other measures of hemodynamic stability. In addition to absolute lactate value, trends in lactate have been very useful for measuring the success or failure of resuscitation and therapy. In canine patients, lactate levels and trends have been used extensively to predict prognosis and measure response to therapy.
The utility of lactate values and trending in feeling patients has not been evaluated. The purpose of this study was to investigate the utility of these tests in hospitalized cats.
A total of 123 cats presenting to a referral center over a 10 month period were included in this study. Cats ranged from 1-20 years in age, with 65% male and 35% female. Any cat receiving IV fluids, steroids, or diuretics in the 24h period prior to admission were excluded. Cats were not stratified based on illness severity. The majority of cats had gastrointestinal or urogenital diseases; musculoskeletal, respiratory, neurologic, cardiovascular, and other diseases made up a lesser proportion.
Blood samples were collected from jugular or medial saphenous veins at admission, and at 6 and 24h after admission.
Median plasma lactate at admission was significantly higher at admission than at times 6 and 24. There was no difference between times 6 and 24. Older cats had slightly (but significantly) higher lactate than younger cats. There was no correlation between lactate at admission and sex, disease, breed, weight, duration of stay, or survival.
23% of cats were hyperlactatemic on presentation. 18% of these remained elevated at time 6, and only 3.5% at time 24. Several cats developed elevated lactates at times 6 or 24. Hyperlactatemia t T6 or T24 had no correlation with survival.
Changes in serial lactate were present in many cats. Changes in lactate between T0-T6, T0-Y24, or T6-T24 were not found to be predicative of survival. Serial lactate measurements were also not associated with the underlying disease state.
This study ultimately concluded that there was no prognostic utility to measuring or trending lactate values in sick cats. This finding is contrary to data in other species, including dogs and humans. Possible reasons for this include small sample size, lack of stratification between different types of lactic acidosis, sampling bias (ie, the most sick cats may not haven been recruited in the study due to difficult obtaining samples), or inappropriate timing. Alternatively, there may be intrinsic differences in feline metabolism which decrease the utility of lactate measurement. Further work is needed in this area. (MRK)