The overall purpose of this study is to demonstrate the usability of a clinical-grade device in the form of a finger clasp similar to a pulse oximeter for monitoring lactate values, by comparing its performance in reading interstitial fluid lactate values against a known clinical standard in the form of venous lactate levels.

Serum lactate measurements are used clinically as a measure of end-organ dysfunction and physiologic stress. Changes in lactate may indicate worsening infection in the setting of sepsis, drug toxicity for certain xenobiotics, or exercise tolerance in exercise physiology. Serum lactate cutoffs have been developed for various disease states and trigger a variety of medical decisions directed at managing the course of the disease.

A common theme in the application of lactate measurements to understanding changes in physiology is the need to obtain venous blood to determine lactate. While point-of-care assays have been developed that improve the processing speed, there continues to be a need to obtain fingerstick blood or in most cases, venous blood. Obtaining venous blood for serum lactate requires an individual with phlebotomy skills, the processing capabilities of a laboratory to determine lactate concentrations, or the availability of point of care technology.

An alternative method to measure lactate is to sample interstitial fluid which surrounds cells and tissues in the body. Obtaining interstitial fluid is potentially less invasive without the need for repeat phlebotomy or the presence of an indwelling intravenous catheter which can become complicated by infection. The analysis of interstitial fluid for glucose has been validated and is clinically utilized in continuous glucose monitors in individuals with diabetes. In this investigation, the investigators will utilize a novel device, the Lab Clasp to obtain interstitial fluid in a noninvasive method. The Lab Clasp is manufactured to resemble a finger pulse oximeter with additional onboard microfluidics channels that obtain a lactate concentration from interstitial fluid. This streamlined process of obtaining the point of care lactate measurements on demand allows for tasks like serial lactate measurements to be accomplished on a reliable schedule with less workload for nursing staff typically required to draw venous blood. Additionally, the portable and noninvasive nature of the Lab Clasp system may render it usable in facilities that lack skilled staff necessary to perform phlebotomy.

Inclusion Criteria

1. Are 18 years or older
2. In general good health, evidenced by no unstable medical problems (no medication changes in the past 3 months)
3. Have no known skin allergy to the components of the Lab Clasp
4. Willing to comply with all study procedures including providing venous blood samples at the CCI
5. Are English speaking
6. Provide consent to participate in the study

Exclusion Criteria:

1. Individuals <18 years old
2. General frailty of health
3. Prohibitively poor vascular access
4. History of malignancy or active malignancy
5. History of cardiac illness
6. History of HIV on antiretrovirals
7. History of alcohol abuse
8. History of uncontrolled psychiatric illness
9. Recent hospitalization within the past 30 days
10. History of vaping, propylene glycol use
11. History of statin use
12. Non-English speaking
13. Pregnant women, children, vulnerable populations
14. Investigator discretion for suspicion of poor study compliance