Lactate testing for veterinary applications

Lactate testing for veterinary applications

Lactate testing for veterinary applications


Lactate has long been used in human clinical practice as a diagnostic and prognostic aid in critically ill patients1. Lactate can be used in sepsis diagnosis and also aid in monitoring post-surgical morbidity, post-cardiac event morbidity, post-transplant morbidity and in assessing patients recovering from pneumonia.

 

Did you know?

Normal lactate levels are the same for both dogs and humans.  Elevated lactate levels in clinical situations in both man and dogs indicates underlying pathology that requires further investigation.

Did-you-know-lactate-testing-in-small-animals

 

Increasingly, lactate testing is being used in the veterinary clinic for prognosis and diagnosis in a number of clinical presentations2. Additionally, the availability of hand held lactate analysers and the demonstration that results from hand held lactate analysers have comparable results to laboratory-based lactate testing methodsmeans that rapid, cost effective and near patient results are available as a prognostic and diagnostic tool for the veterinarian. 

 

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1. Singer et al 2016 JAMA 315 801-810; Shankar-Hari et al 2016 JAMA 315, 775-787; Vincent et al 2016 Critical Care
2. eg Sharkey & Wellman 2015 and Table 1
3. Di Mauro & Schoeffler 2016; Acinero et al 2007; Karagiannis et al 2013

Vet-lactate-testing-in-small-animals
Lactate  is useful tool in treatment decision making

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Rapid, cost effective, near patient results 

Lactate testing in small animals

Whilst lactate is not diagnostic of any particular disease state, when taken in isolation as a single reading, it is a useful tool in overall treatment decision making pathway and as a guide to morbidity and/or the need to monitor more closely specific patients.

 

For example, a normal lactate value (approx. 2.0 mmol l-1) in dogs is a far better predictor of survival than a high lactate value is of morbidity or death.

 

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Vet-lactate-testing-in-small-animals-diagnosis

Studies on lactate testing in small animals

Recent studies have highlighted the use of lactate testing for a number of animal conditions. 

 

Troja et al 2018

Gastric dialtion volvulus

Correlation between lactae concentartion and dogs with confirmed GDV

Aona et al 2017

Gastric dialtion volvulus

Increased lacate levels assocaited with GDV and cahmges in ventricular diameter 

McQuown et al 2018

Lymphoma

Increased lactate in dogs with confirmed lymphoma compared with controls

Robbins et al 2017

Fatigue

Increased lacate correlates with other parameters of fatigue in working dogs

Keyserling et al 2017

Abnormal thoracic radiographs

In dogs with abonormal thoracic xrays not associated with cardio/pulmonary diagnosis, increased lactae was assocaitged with increased morbidity

Castagnetti et al 2017 Post partum distress Increased lacacte levels and inability to normalise lacate within 24 of birth was associated increased morbidity in puppies
Groppetti et al 2015 Post partum distress Still born puppies have elevated amniotic fluid lacate levels compared with live births and lacate could be a predictor of post partum outcomes 
Fahey et al 2017 Cardiac effusion Elevated lacate levels above 5 mmol L-1 were assocaited with dogs with cardiac effusion
Bush et al 2016 Septic peritonitis Increased lactate levels were associated with secondary septic peritonitis
Cortellini et al 2015 Septic peritonitis Lactate concentration and lactate clearance were good prognostic indicators in dogs with septic peritonitis
Gillespie at al 2017 NA Normal lacate value is a better predictor of survival than a high lacate value is of death
Eichenberger et al 2016 Babesiosis Increased levels of lactate are associated with increased chance of non-survival in confirmed cases of babesia infection
Bruchim et al 2016 Heat shock Lacate is significantly elevated at 12 hours post presenation in non-surviving with heatstroke
Sharma & Holowaychuk 2015 Head trauma Elevated lactae levels post-head trauma is a risk factor for non-survival
Proot et al 2015 Septic arthritis Synovial fluid lactate concentration is significantly increased in septic arthritis and could help rule out this condition in a quick and cost-effective way
Ateca et al 2015 Hypotension Blood lactate is negatively associated with systolic blood pressure and survival probability and may represent a useful prognosis in hypotensive dogs
Hall et al 2014 Trauma Low lacate levels at admsiion were predictive of survival to discharge
Malek et al 2013 Post-cholecystectomy recovery Elevated lacate post gall bladdre removal are assocaited with poor clinical outcomes
Volpato et al 2013 Pyometra Lacate levels are increased in bitches with pyometra

Table 1

Lactate testing in equine athletes


Lactate accumulation in muscle cells and blood is a normal consequence of exercise in horses. At low exercise intensity, the aerobic metabolism of glycogen, glucose and fat provides energy in the form of ATP to fuel muscle activity. As exercise intensity increases, oxygen levels can no longer meet the ATP requirement and rather than pyruvate being used in the citric acid cycle in the mitochondria, it is metabolised to lactate to fuel muscle energy requirements.  Because lactate cannot be used as an energy source in muscle, lactate is sequestered into the blood for transport to the liver where it is used as an energy source or converted to pyruvate. Blood lactate levels during exercise are therefore an indicator of anaerobic metabolism and provide an indicator of muscle exertion. It is the onset of the “switch” from aerobic to anaerobic metabolism and the ability to maintain steady state lactate levels at any given exercise intensity that is of interest in conditioning athletes, be they human or equine.

 

Did you know?

Resting lactate levels in horses are equivalent to those in humans (1.5-2 mmol/L).  After exercise horse lactate levels can exceed 20 mmol/L whereas in humans, post exercise levels rarely rise above 10mmol/L

Did-you-know-lactate-testing-in-horses.png

 

In order to determine optimum training regimes and fitness gains, set exercise tests (SETs) or step tests are used.  Typically, a SET consists of a baseline lactate reading (t = 0) and several lactate measurements over 10 – 40 minutes of either steady state exercise (eg treadmill running at a specific velocity) or increasing exercise intensity (eg treadmill running with increased velocity at set time points) followed by a recovery period.  The same SET is then performed after a period of training and the plots of the lactate levels are compared.  (See figure 1)

 

Resting blood lactate concentration in the horse is approximately 1–1.5 mmol/L. At low speeds this value does not change greatly from the resting value. At moderate speeds lactate begins to accumulate in the blood with accumulation accelerating when exercise/speed increases above the level at which blood lactate is about 4 mmol/L. This threshold workload at which blood lactate is maintained at 4 mmol/L is often referred to as the anaerobic threshold, or the speed at onset of accumulation of blood lactate (OBLA) and also as VLa4. VLa4 is therefore the work velocity/intensity which results in a blood lactate of approximately 4 mmol/L. This value is derived from inspection of graphs of exercise speed (on the X axis) plotted against blood lactate concentration (on the Y axis) (See figure 1). At speeds greater than VLa4, lactate accumulates rapidly in the blood. The general relationship between velocity and blood lactate is therefore usually described as exponential. However, if sufficient steps are used in the exercise test, the relationship is described by two straight lines, with an obvious velocity at which the blood lactate begins to accumulate in blood.

 

Use-of-Lactate-Testing-Equine-AthletesFIgure 1

 

After a race or intense training, blood lactate concentrations are usually greater than 20 mmol/L. It is normal for the blood and muscle lactate concentration to then gradually decrease over a 1–2 h period after a race or fast work. Acidosis of muscle and blood is a normal result of fast work, and this acidosis is rapidly reversed by the horse’s own metabolism.

 

Many studies of horses trained on both treadmills and on racetracks consistently demonstrate that training results in lower blood lactate concentrations at the same work speed. The speed at which blood lactate begins to accumulate rapidly, VLa4, also increases ie the horse is able to work at a higher speed/intensity without accumulating lactate. Repeated tests of the blood lactate relationship with velocity are suitable as a means of measuring increasing stamina with training. VLa4 measurements every 2–3 weeks also enable measurement of changes in fitness through the training program.

 

Capillary blood sampling

EKF has described how to take capillary sample in humans, and the same basic principles apply except that lancets should be larger (21G, 7mm) and the fur will need to be shaved at the sample site.  As described by Kobayashi (2007), the capillary puncture site should be the central region of the left neck. Shave an area approximately 1cm2 and disinfect with 50% ethanol in water to wash off dirt before exercise.  Post exercise, remove sweat using distilled water and puncture the shaved site with a 21G 7mm long lancet. Wipe away the initial drop of blood and use the second drop to take the lactate sample.

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Blood lactate levels provide an indicator of muscle exertion

Note

EKF Diagnostics does not warrant the validity of the reported results and it is the responsibility of the individual veterinarian to balance the risk/benefits of any treatment pathway based on an understanding of the scientific data available.