Serum lactate can be considered a marker of clinical badness.
Elevated lactate (greater than 4) indicates bad things may be happening to your patient. It is up to you to figure out what those things might be.
History of Lactate.
Serum lactate was first described following the autopsy heart puncture of a 23 year old female who had probably died from septic shock in 1843 by a German physician chemist; Johann-Joseph Scherer.
The relationship of raised lactate levels and poor outcomes has been described in the literature since the early sixties. Particularly in relation to septic shock.
Why is it important?
Studies have repeatedly shown that elevated lactate is associated with increased mortality. For example, a lactate above 4 is associated with mortality 10 times higher than that for patients with normal values.
What elevates serum Lactate?
In long: you will need to go back and review the Krebs Cycle. Good luck. I’ll be in the pan room if you need me.
In short: Lactate is the metabolic end-product of anaerobic glycolysis as the body attempts to generate energy (ATP) in an environment of cellular hypoxia.
It is usually seen in all tissues, including skeletal muscle, brain, intestine and red blood cells. But when your patient becomes critically unwell lactate is increasingly produced in the lungs, white blood cells and splanchnic organs.
However, cellular hypoxia is not the only thing that causes a rise in your unwell patients serum lactate. In fact, it is probably NOT the primary cause.
Serum lactate is also elevated by the bodies stress response. That is: the body attempts to increase glycolysis via the stimulation of beta-adrenergic receptors (particularly in skeletal muscle cells) by circulating adrenaline.
It has been suggested that the elevated lactate levels produced in the stress response may even be beneficial to improving cardiac and cerebral function.
This compensatory mechanism may be so efficient that patients with elevated lactate (and therefore a proximity to badness) may still be maintaining normal vital signs.
Lactate is a marker of endogenous catecholamine release. This makes lactate useful for detecting patients who have occult shock: patients who are maintaining their blood pressure due to a vigorous endogenous catecholamine response. These patients may have deceptively reassuring vital signs, masking the fact that they are in a catecholamine-dependent shock state (simply using their own catecholamines rather than, for example, a norepinephrine infusion). Elevated lactate identifies these patients as having an increased risk of death or decompensation, thus requiring more aggressive management. Although most often associated with sepsis, occult shock with elevated lactate may be seen with any cause of shock.
What other things can elevate serum Lactate?
|Elevated Serum Lactate|
|Seizures||Intense exercise||ethanol intoxication|
|adrenaline||Renal failure||leukaemia / Lymphoma|
How do I test for serum Lactate?
Serum Lactate can be obtained from a venous or arterial blood gas sample sent to the lab.
Many critical care and emergency departments now have point of care (bedside) blood gas analysers that can accurately determine serum Lactate levels.
It has been shown that there is no significant difference between venous and arterial blood values when using point of care testing.
Original featured image via emiliano.marocchi
- Fuller, B. M., & Dellinger, R. P. (2012). Lactate as a Hemodynamic Marker in the Critically Ill. Current Opinion in Critical Care, 18(3), 267–272. http://doi.org/10.1097/MCC.0b013e3283532b8a
- Lactate = LactHATE. (2015, September 5). Retrieved February 5, 2016, from http://stemlynsblog.org/lactate-lacthate/
- Understanding lactate in sepsis & Using it to our advantage. Retrieved from http://emcrit.org/pulmcrit/understanding-lactate-in-sepsis-using-it-to-our-advantage/
- Lactic Acidosis. (n.d.). Retrieved February 5, 2016, from http://lifeinthefastlane.com/ccc/lactic-acidosis/
- Lactate PK by Dr Laura Castle. Retrieved February 5, 2016, from http://broomedocs.com/2013/07/lactate-pk-by-dr-laura-castle/