ARTERIAL BLOOD-SAMPLING DEVICES INFLUENCE IONIZED CALCIUM MEASUREMENTS

Objective: To determine the effect of commercially available arterial blood sampling devices on ionized calcium measurements. Design: Prospe ctive study. Setting: Neurosurgical and shock-trauma intensive care un its (ICU) at a tertiary care teaching hospital. Patients: Fourteen pat ients admitted to the ICU, Each patient had an indwelling arterial cat heter. Interventions: Arterial blood sampling, Measurements and Main R esults: In 14 ICU patients, measurements of arterial blood ionized cal cium concentrations were performed, using 12 different commercially av ailable arterial blood sampling devices. Significant underestimation o f ionized calcium in blood samples compared with the reference test tu be (Vacutainer 45) was seen in seven of the devices. Arterial blood io nized calcium concentrations measured, using one commercially availabl e syringe, were significantly higher compared with the reference test tube. There was no correlation between either the amount or type of he parin in the arterial blood sampling devices and arterial blood ionize d calcium measurement. Conclusions: This study demonstrates that vario us commercially available arterial blood sampling devices alter arteri al blood ionized calcium measurements, These alterations are clinicall y important because ICU patients may be treated with inappropriate cal cium supplementation.