Lactate Levels and Sepsis: What’s the Big Deal?
Today, I was going to post a hilarious (but helpful) video clip of UCLA’s Kern Medical Center staff singing “SEPSY Back”, a play on Justin Timberlake’s hit song. But, as I pulled up the video to re-watch the clip before posting, I decided to take a more serious look at sepsis as well (if you’re not in the mood for a review, scroll to the bottom of the post for entertainment only). Sepsis measures have been a big push in the emergency department where I work lately. One component of the ED’s sepsis campaign is the drawing of lactate levels. Why?
Why Do We Care about Sepsis?
Sepsis occurs when bacteria enter the bloodstream. It can arise from common infections such as those of the urinary tract, skin, or even a dental abscess. Eventually, the infection can cause internal organs like the heart, kidney, and lungs to malfunction. Septic shock ensues causing blood pressure to plummet, the heart to fail, and subsequently, without adequate blood flow, cells throughout the body are deprived of essential oxygen. While most people with mild sepsis are effectively treated, septic shock has a mortality rate of nearly 50 percent.
What is Lactate?
When cells are forced to operate in a hypoxic environment, such as in the case of septic shock, they must turn to a less efficient means of producing energy to function. This method of energy manufacturing results in excess production and impaired clearance of lactic acid. Due to the body’s neutral pH, most lactic acid in the blood is present in the form of lactate. So, clinically, lactate levels are helpful in monitoring conditions involving inadequate delivery of oxygen to the body such as sepsis.
Lactate Levels in Septic Shock
Lactate levels are important in the diagnosis and treatment of septic shock as they are closely tied to mortality rate and give an indication as to the severity of the patient’s condition. A lactate level above 4.0 mmol/L is associated with a 27% mortality rate, compared with a mortality rate of 7% for patients with a lactate level of 2.5-4.0 mmol/L and a death rate below 5% for those with a lactate level below 2.5 mmol/L (ACEP News). Patients with septic shock can be identified as those with a lactate level above 4.0 mmol/L or a systolic blood pressure below 90 mm Hg after a 20-30 mL/kg fluid bolus.
Not only is lactate helpful in identifying septic patients, it is useful in monitoring their treatment. With a half-life of about 20 minutes, lactate levels change rapidly in the body. Decreasing lactate levels indicate effective treatment of the condition. Patients whose lactate levels decrease by 10% after six hours of treatment, for example, have a mortality rate below 20%, compared with a more than 50% mortality rate for septic patients whose lactate level has not fallen.
Clinical Pearls
Theoretically, prolonged application of a tourniquet can raise lactate levels at the site of the blood draw. So, if you suspect a tourniquet was left on for more than two minutes, redraw the lactate level.
And, as promised, here’s an entertaining video review of sepsis.
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