Arterial lactate vs venous lactate as indicator of metabolic limitation during cardiopulmonary exercise testing.

Background: In the pulmonary function department of the Academic Medical Centre in Amsterdam the lactate is determined through venous blood sampling at 3 minutes after peak exercise and the gas exchange is assessed with arterial blood sampling at peak exercise. Since the collection of both the arterial and venous blood samples are expensive and invasive for the patient, the determination of the lactate value from the arterial blood sample would be most practical. Aim: The aim of this study was to determine if the arterial lactate can be used as alternative to venous lactate in the assessment of metabolic tolerance during exercise testing. Methods: This study included 56 patients referred for cardiopulmonary exercise testing. Arterial samples were obtained from the radial artery at peak exercise and venous samples were obtained 3 minutes after peak exercise. Results: The Bland and Altman analysis of arterial and venous lactate showed difference of 1.57 mmol/l (limits of agreement (LOA) -1.37 – 4.50). The correlation between venous and arterial lactate was r=0.778. For venous lactate and base excess was the correlation r=-0.761. Conclusion: Determining the lactate value from the arterial blood sample obtained at peak exercise is more useful than venous sampling alone. Although the difference between arterial and venous lactate is small (1.57), the range can be wide. Arterial blood sampling is both economical and less invasive for the patient while obtaining more information about gas exchange during exercise testing.