Measuring blood lactate levels in dogs with Gastric Dilatation Volvulus (GDV) can guide you on your resuscitation efforts and help you better understand the prognosis as you communicate with dog owners.
Below are tips on measuring blood lactates that may help you in your practice.
What is a Blood Lactate Actually Measuring?
Lactic acid is a weak acid and dissociates into lactate (-) and H+. Normally glucose is converted into pyruvate via glycolysis in the cytosol and then can go through 4 different pathways.
These pathways include:
- TCA cycle where 36 ATP formed and then enters the electron transport chain in the mitochondria
- Forms lactate via lactate dehydrogenase
- Formation of alanine
- Gluconeogenesis where it is converted back to glucose
The conversion of pyruvate to lactate is favored by:
- Systemic hypoperfusion necessitating anaerobic metabolism
- Regional hypoperfusion or dysfunction at the microcirculatory level (small capillaries(
- Increased anaerobic glycolysis where tons of pyruvate us formed (due to cytokines, catecholamines, increased WBCs)
- Mitochondrial dysfunction in sepsis and drug toxicity
Lactate levels represent the balance between production and clearance. Lactate clearance is done mainly in the liver and about 40% via the kidney.
The normal lactate blood level ranges include:
- Less than 2 to 2.5 is normal
- 3 to 5 is a mild increase
- 5 to 8 is moderately increased
- Over 8 is marked increased
There are 2 types of lactate – referred to as Lactate L and Lactate D. The “L” Lactate is the kind that matters in most of our emergency patients but “D” lactate can be produced in bacterial fermentation of carbohydrates (SIBO).
Hyperlactatemia is broken into 4 categories – Type A, Type B1, B2, and B3. Type A and B1 are the most clinically relevant.
- Type A: Imbalance of delivery of oxygen and utilization of oxygen = malperfusion
- Decreased delivery due to shock, anemia, hypoxemia, hypoperfusion
- Increased oxygen utilization due to exercise, shivering, tremors, or seizures
- Type B1: Decreased lactate clearance due to acute liver or kidney disease, hyperthyroidism, sepsis
Blood Lactate Levels in Dogs with GDV
Lactate has been looked at as a biomarker in GDV as a prognostic indicator. The first papers looked at a single lactate measure. What we have found over time is that it is really the clearance of lactate (the change of lactate over time from therapy, also known as delta lactate) is a better indicator of prognosis.
A landmark human paper looking at lactate clearance in sepsis found that a delta lactate of > 10% is a good indicator.
Below is a summary of lactate variables looked at in various publications:
- Lactate > 6 associated with gastric necrosis
- Lactate < 9 associated with increased survival
- Initial lactate > 6 did not predict necrosis
- Lactate < 4.1 associated with better survival
- Lactate increased with necrosis (6.35 vs. 3.4) and with non survival ( 6.8 vs. 3.4)
- Initial lactate > 7.4 predicted necrosis and outcome
- Post treatment (fluids, before surgery) > 6.4, delta lactate < 4 or < 42.5% associated with nonsurvival
- 100% of those with D lactate > 42% survived vs. 56% of those with D lactate < 42%
- Delta lactate > 50% good prognosis
- Initial lactate > 7.4 predicted necrosis and outcome
What you can see is that there isn’t a great consensus and that some of the papers contradict themselves. We utilize lactate solely as interpreted as delta lactate and even with that with a grain of salt.
This means I will do a lactate on presentation and after fluid resuscitation before surgery if the initial is high. If the second value remains high and if the initial value is very high I will have a more serious conversation that we may find gastric necrosis in surgery and may need to do a gastric resection. We also may have a sicker dog that needs more intensive care post-operatively.
A single high lactate or even failure to clearance doesn’t mean the dog will die or even need a gastric resection. It may be telling you that you are not fluid resuscitated yet, there is some other failure of clearance.
I try to discourage euthanasia based solely on a lactate value as the post-operative management with critical care has evolved greatly over the years. There are many of these dogs that survive hospitalization even with numbers that say they wouldn’t.
