Fingerstick Pseudohypoglycemia
A Teachable Moment article published on November 27, 2017 in JAMA contained a valuable lesson regarding the limitations of fingerstick glucose measurements in critically ill patients. This article began with a case study of a70 year old male with an ejection fraction of 20% due to alcoholic cardiomyopathy who was admitted for increasingly frequent episodes of lightheadedness. During hospitalization his fingerstick blood glucose levels (FSBGs) ranged between 60 mg/dL and 70 mg/dL during episodes of lightheadedness. He was not diabetic and did not take any medications known to cause hypoglycemia. His symptoms failed to improve with glucose replacement. His repeatedly low FSBGs led to a workup for insulinoma, which required him to be transferred to a higher level of care for supervised fasting and overnight glucose checks. Overnight fasting increased the elderly patient’s risk for delirium and diverted the medical team’s attention away from his primary diagnosis of severe heart failure.
During this investigation, it was noted that simultaneous venous plasma glucose levels were significantly higher than fingerstick blood glucose values. Because of this discrepancy, systemic hypoglycemia was excluded as a cause of his lightheadedness. Instead, his symptoms were attributed to end-stage heart failure. He improved after treatment for fluid overload and was discharged.
Low FSBGs were attributed to poor peripheral vascular perfusion secondary to advanced cardiomyopathy. FSBGs accurately measure glucose levels in the microcirculation, but are considerably lower than systemic plasma glucose due to sluggish capillary blood flow and continued peripheral tissue glucose consumption.
As this case clearly illustrated, physicians need to be educated about the limitations of fingerstick glucose measurements in critically ill patients. Pseudohypoglycemia may occur in patients with trauma, shock, sepsis, severe dehydration, peripheral vascular disease, cyanotic heart disease, acrocyanosis, Raynaud phenomenon, and scleroderma.
References
Wang EY, Patrick L and Connor DM. Blind obedience and an unnecessary workup for hypoglycemia: A teachable moment. JAMA, published online November 27, 2017. E1-E2.
AtkinSH,DasmahapatraA,JakerMA, Chorost MI, Reddy S. Fingerstick glucose determination in shock. Ann Intern Med. 1991;114:1020-24.
