Evaluation of lacrimal fluid as an alternative for monitoring glucose in critically ill patients

Objective: This study evaluated the use of lacrimal fluid glucose concentrations as a minimally invasive, alternative sampling strategy for monitoring glucose concentrations in surgical/trauma ICU patients. Design and setting: Prospective, paired sample study in an adult surgical/trauma ICU. Patients: Patients receiving subcutaneous or intravenous insulin requiring routine capillary blood glucose measurements. Patients receiving ocular lubricants, artificial tears, or routinely administered ophthalmic medications and patients with facial injuries were excluded. Interventions: Lacrimal fluid was collected using glass capillary tube placed near the cul-de-sac of the eye. Capillary blood glucose was determined using a bedside glucose meter as per routine ICU care. Measurements and results: Lacrimal fluid glucose concentration was analyzed using high-performance liquid chromatography with pulse amperometric detection. Forty-four paired samples from five patients were analyzed. Pearson correlation between lacrimal fluid (μM) and blood glucose (mM) concentrations and the proportional change from baseline revealed no significant associations. Due to the very poor association, enrollment was discontinued after five patients. Conclusions: Lacrimal fluid and blood glucose concentrations were poorly correlated, suggesting that the former is not a reliable alternative to blood glucose monitoring in surgical/trauma ICU patients requiring insulin therapy.