Is serum lactate necessary in patients with normal anion gap and serum bicarbonate?

There has been an increase in patients having serum lactate drawn in emergency situations. The objective of this study was to determine whether or not it was necessary to obtain a lactate level in patients with a normal serum bicarbonate level and anion gap.

This is a retrospective chart review evaluation of 304 patients who had serum lactate and electrolytes measured in an emergency setting in one academic medical center.

In 66 patients who had elevated serum lactate (>2.2mmol/L), 45 (68%) patients had normal serum bicarbonate (SB) (greater than 21 mmol/L). Normal anion gap (AG) (normal range <16 mEq/l) was found in 51 of the 66 patients (77%).

We found that among patients with elevated serum lactate, 77% had a normal anion gap and 68% had normal serum bicarbonate. We conclude serum lactate should be drawn based on clinical suspicion of anaerobic tissue metabolism independent of serum bicarbonate or anion gap values.