Abstract
Lactate levels are commonly used as an indirect measure to assess metabolic stress in clinical conditions like sepsis. Dynamic lactate measurements are recommended to assess and guide treatment in patients with shock and other critical care conditions. A minimally invasive, continuous lactate monitor has potential to improve clinical decisions and patient care. The purpose of the study was to evaluate continuous lactate measurements of a novel enzymatic Continuous Lactate Monitor (CLM) developed in our laboratory. Lactate levels were monitored during incremental cycling exercise challenges as a tool for hyperlactatemia. Six healthy individuals 18–45 y/o (4 males, 2 females) participated in the study. CLM devices were inserted subcutaneously in the postero-lateral trunk below the renal angle, one hour before the exercise challenge. Each exercise challenge consisted of a 3 to 12-min warm up period, followed by up to 7, 4-min incremental workload bouts separated by rest intervals. Continuous lactate measurements obtained from CLM were compared with commercial lactate analyzer (Abbott iSTAT) measurements of venous blood (plasma) drawn from the antecubital vein. Blood was drawn at up to 25 time points spanning the duration of before exercise, during exercise, and up to 120 min post exercise. Area under the curve (AUC), and delay time were calculated to compare the CLM readings with plasma lactate concentration. Average plasma lactate concentration increased from 1.02 to 16.21 mM. Ratio of AUC derived from CLM to plasma lactate was 1.025 (0.990–1.058). Average dynamic delay time of CLM to venous plasma lactate was 5.22 min (2.87–10.35). Insertion sites examined 48 h after CLM removal did not show signs of side effects and none required medical attention upon examination. The newly developed CLM has shown to be a promising tool to continuously measure lactate concentration in a minimally invasive fashion. Results indicate the CLM can provide needed trends in lactate over time. Such a device may be used in the future to improve treatment in clinical conditions such as sepsis.
Highlights
L-Lactate is a product of the glycolysis pathway via pyruvate and has been used as a biomarker of oxygen deficits in tissues during events such as hypovolemic, septic, or cardiogenic shock [1, 2]
Continuous Lactate Monitor (CLM) sensor output was calibrated to blood plasma lactate concentrations via least squares regression of the two timeseries after alignment by cross correlation, as described above
area under the concentration–time curve ratio (AUCR) and dynamic delay analyses were performed on all time periods when CLM data and plasma lactate data were both available
Summary
L-Lactate (subsequently referred to as lactate) is a product of the glycolysis pathway via pyruvate and has been used as a biomarker of oxygen deficits in tissues during events such as hypovolemic, septic, or cardiogenic shock [1, 2]. Expanding on the value of a single venous lactate measurement, investigators have evaluated serial lactate concentration dynamics and found association between reduction in serial lactate concentration over time and improved outcomes [7,8,9]. This association may be related to roles of blood lactate as a volumetric integrator of cell glycolysis in hypoxic tissues, and the multiple roles of lactate as a substrate for cell metabolism and signaling [10, 11]. Controlling blood lactate using a strategy that includes a continuous lactate monitoring system has potential to improve treatment of critically ill or injured patients
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