Changes in oxygen measurements when whole blood is stored in iced plastic or glass syringes

Tonometered whole-blood and plasma specimens were tested in plastic and glass syringes to determine whether clinically significant changes in gas tensions occur during sample storage. When whole blood was tonometered with 60 and 100 mL/L (6% and 10%) oxygen and then stored for 30 min in iced plastic syringes, the pO2 of the samples remained stable (mean change = +0.4 and +0.8 mmHg, respectively). However, for 140 mL/L (14%) oxygen tonometry, the pO2 increased significantly (mean change = +8.4 mmHg; P less than 0.0001). When tonometered plasma was stored in iced plastic syringes, the pO2 increased progressively at all three concentrations, with the smallest change occurring at 140 mL/L (mean change = +12.6 mmHg) and the greatest at 60 mL/L oxygen (mean change = +20.9 mmHg). In contrast, when iced glass syringes were used for storing plasma or whole blood, no clinically significant changes in pO2 were found at any of the tonometered oxygen values for 60 min. When whole blood was stored in plastic syringes at ambient temperature for 30 min, again no clinically significant changes in pO2 were found at these tonometry conditions. Apparently, some blood gas samples stored in iced plastic syringes may yield clinically significant errors in oxygen tension.