Clinical evaluation of a novel subcutaneous lactate monitor

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.

Transcutaneous Flexible Sensor forIn VivoPhotonic Detection of pH and Lactate

“…After poisoning and cobinamide treatment, PALS detected the expected increase in lactate concentration and decrease in blood pH, which were also in agreement with the intermittent i-STAT blood assays (Figure B,C). The area under the concentration-time curve ratio between PALS and i-STAT measurements was calculated and assessed as described in Dror et al, following FDA guidelines. , The area under the concentration-time curve ratio for pH (0.979) and lactate (1.084) indicates PALS bioequivalence to the i-STAT blood analyzer in this study. There is a difference in pH measurements between i-STAT and PALS beginning at 110 min.…”

“…In regard to miniaturizing the MSF, our research group has successfully reduced the lactate optode to a width of 300 μm. 39 For the pH optode, the dimensions of the photodetector are the limiting factor for miniaturization. In future work, we will incorporate photodetectors having dimensions similar to the MSF LEDs, yielding a 1/3 mm wide device.…”

“… 34 , 36 , 37 As an alternative to electrochemical sensing, our group and others have published the use of a phosphorescent oxygen-sensitive dye for continuous measurements of lactate and other analytes. 38 , 39 In our clinical studies, oxygen was detected by the metalloporphyrin dye platinum(II) meso-tetraphenyl tetrabenzoporphine (PtTPTBP). 39 PtTPTBP phosphorescence is quenched by oxygen, reducing its luminescence lifetime.…”

“… 38 , 39 In our clinical studies, oxygen was detected by the metalloporphyrin dye platinum(II) meso-tetraphenyl tetrabenzoporphine (PtTPTBP). 39 PtTPTBP phosphorescence is quenched by oxygen, reducing its luminescence lifetime. This lifetime can be assessed by determining the phase shift between excitation and emission waveforms.…”

“…The LOX reaction consumes both oxygen and lactate while producing hydrogen peroxide and pyruvate. This allows lactate to be indirectly measured through monitoring the consumption of oxygen or generation of hydrogen peroxide. , The generation of hydrogen peroxide is commonly used for electrochemical-based LOX sensing of lactate. − Common challenges in such electrochemical sensing include high operation voltages, dependencies on electron-transfer mediators (which can be toxic and exhibit poor solubility), and acetaminophen interference. ,, As an alternative to electrochemical sensing, our group and others have published the use of a phosphorescent oxygen-sensitive dye for continuous measurements of lactate and other analytes. , In our clinical studies, oxygen was detected by the metalloporphyrin dye platinum­(II) meso-tetraphenyl tetrabenzoporphine (PtTPTBP) . PtTPTBP phosphorescence is quenched by oxygen, reducing its luminescence lifetime.…”