Lactate levels in arterial and venous blood may be correlated but not equivalent

Lactate Arterial-Central Venous Gradient among COVID-19 Patients in ICU: A Potential Tool in the Clinical Practice

Objective

In physiological conditions, arterial blood lactate concentration is equal to or lower than central venous blood lactate concentration. A reversal in this rate (i.e., higher lactate concentration in central venous blood), which could reflect a derangement in the mitochondrial metabolism of lung cells induced by inflammation, has been previously reported in patients with ARDS but has been never explored in COVID-19 patients. The aim of this study was to explore if the COVID-19-induced lung cell damage was mirrored by an arterial lactatemia higher than the central venous one; then if the administration of anti-inflammatory therapy (i.e., canakinumab 300 mg subcutaneous) could normalize such abnormal lactate a-cv difference.

Methods

A prospective cohort study was conducted, started on March 25, 2020, for a duration of 10 days, enrolling 21 patients affected by severe COVID-19 pneumonia undergoing mechanical ventilation consecutively admitted to the ICU of the Rimini Hospital, Italy. Arterial and central venous blood samples were contemporarily collected to calculate the difference between arterial and central venous lactate (Delta a-cv lactate) concentrations within 24 h from tracheal intubation (T ₀) and 24 hours after canakinumab administration (T ₁).

Results

At T ₀, 19 of 21 (90.5%) patients showed a pathologic Delta a-cv lactate (median 0.15 mmol/L; IQR 0.07-0.25). In the 13 patients undergoing canakinumab administration, at T ₁, Delta a-cv lactate decreased in 92.3% of cases, the decrease being statistically significant (T ₀: median 0.24, IQR 0.09-0.31 mmol/L; T ₁: median -0.01, IQR -0.08-0.04 mmol/L; p=0.002).

Conclusion

A reversed Delta a-cv lactate might be interpreted as one of the effects of COVID-19-related cytokine storm, which could reflect a derangement in the mitochondrial metabolism of lung cells induced by severe inflammation or other uncoupling mediators. In addition, Delta a-cv lactate decrease might also reflect the anti-inflammatory activity of canakinumab. Our preliminary findings need to be confirmed by larger outcome studies.

Arterial vs venous lactate: Correlation and predictive value of mortality of patients with sepsis during early resuscitation phase

PURPOSE

To compare the lactate concentrations obtained from venous to those obtained from arterial blood in predicting hospital mortality of patients with sepsis and septic shock. To also assess lactate clearance as predictor for mortality.

METHODS

100 patients with septic shock were prospectively enrolled. Serum was sampled at baseline and after 6 h of resuscitation from arterial and venous lines. Demographic, severity indices, hemodynamic measures as well as lactate clearance levels were noted. Data were analyzed for bias and precision.

RESULTS

There was correlation between venous and arterial lactate concentrations at the baseline (R = 0.68) and at the 6-hour time point (R = 0.95). Venous concentrations were consistently higher than those obtained from an arterial access by 0.684 mg/dL. Further, arterial lactate level > 3.2 mmol/L and clearance of <20% were considered the cutoff for the mortality risk. While only 8% of the patients with no risk died, all 20 patients who had lactate level > 3.2 mmol/L and clearance of <20% died within the hospital.

CONCLUSION

Our data suggests a strong correlation between arterial and peripheral venous the lactate levels and in the initial phase of resuscitation in septic shock patients we can use venous lactate level as biomarker instead of arterial lactate level. The study also showed that combining lactate levels and its clearance is a reliable predictor of mortality in sepsis.