Hypoxemia in the presence or absence of systemic inflammation does not increase blood lactate levels in healthy volunteers.

PURPOSE

Elevated lactate levels are a sign of critical illness and may result from insufficient oxygen delivery. We investigated whether hypoxemia and/or systemic inflammation, results in increased lactate levels in healthy volunteers.

MATERIALS AND METHODS

30 healthy volunteers were exposed to either 3.5 h of hypoxemia (FiO ± 11.5%), normoxemic endotoxemia (FiO 21%, administration of 2 ng/kg endotoxin), or hypoxemic endotoxemia (n = 10 per group). Blood lactate, hemoglobin, SpO, PaO PaCO, pH, and hemodynamic parameters were serially measured.

RESULTS

Hypoxemic treatment resulted in lower SpO (81.7 ± 2.6 and 81.4 ± 2.4% in the hypoxemia and hypoxemic endotoxemia groups, respectively) and hyperventilation with a PaCO decrease of 0.8 ± 0.5 and 1.5 ± 0.6 kPa and an increase in pH. Arterial oxygen content (CaO) decreased by 20.5 ± 2.9 and 23.5 ± 4.4%, respectively. Lactate levels were slightly, but significantly higher in both hypoxemic groups compared with the normoxemic endotoxemia group over time (p < 0.0001 for both groups), but remained below 2.3 mmol/L in all subjects. Whereas PaO and SpO did not correlate with lactate levels, PaCO, pH and CaO did.

CONCLUSIONS

Hypoxemia, in the absence or presence of inflammation does not result in relevant increases of lactate. The small increases in lactate observed are likely to be due to hyperventilation-related decreases in glycolysis.