Use of glass capillaries avoids the time changes in high blood Po-2 observed with plastic syringes

Study objectives: in adults, arterial blood samples are usually drawn using plastic syringes. In contrast to glass syringes, plastic syringes let oxyg en diffuse through their wall. This results in Po-2 changes during storage, especially when Po-2 is high. An alternative to glass syringes is the Micr osampler (Roche Diagnostics; Schaffhausen, Switzerland), a commercially ava ilable device consisting of a heparinized glass capillary fitted with a 26- gauge needle and used to collect arterial blood in the same way as a plasti c syringe fitted with a needle. Design: We evaluated the performance of the Roche Microsampler for storing arterial blood in view of Po-2 measurement, comparatively with glass and pl astic syringes. Five approximate initial Po-2 levels (650, 400, 200, 130, a nd 80 mm Hg) and two storage temperatures (ambient temperature and 4 degree sC) were studied. Settings: Bench study. Results: Plastic syringes allowed reliable measurement of Po-2 values when initial Po-2 was too low to ensure complete hemoglobin oxygen saturation, b ut were associated with time-dependent underestimation of Po-2 at higher in itial Po-2 values. No such underestimation occurred with the Roche Microsam pler stored at 4 degreesC for up to 1 h for all Po-2 levels studied. Conclusion: The Roche Microsamplers appeared to be reliable devices in prev enting oxygen diffusion.