The Effect of Oxygen Tension, Syringe Type and Temperature on Arterial Blood Gas Storage in Healthy Alpacas

Abstract

Objective: To assess the influence of storage temperature, syringe type and oxygen tension on arterial blood gas (ABG) parameters in alpacas.

Study Design: Prospective, randomized, cross-over study.

Animals: Six healthy, adult alpacas (2-8 years).

Methods: All alpacas were randomly exposed to supplemental oxygen, room air, and hypoxic oxygen/nitrogen gas mixtures via a sealed facemask and non-rebreathing circuit, following recovery from sedation (0.1 mg kg-1 IV xylazine) for saphenous arterial catheterization. For each gas type, 16 ABG samples were collected into heparinized glass and plastic syringes, with eight stored at room temperature and eight in iced water (3-4°C). Samples were analyzed at 5, 30, 60 and 120 minutes after collection and evaluated via repeated measures ANOVA and paired samples t-test (P<0.05).

Results: The PaO₂ significantly decreased at room temperature in both normoxemic and hyperoxemic blood, following storage for ≥30 minutes in glass syringes, and in hyperoxemic blood stored in plastic syringes at room temperature. However, the mean PaO₂ of hyperoxemic blood stored in plastic syringes on ice significantly increased at all time-points. Overall, two hour storage induced a mean change of <3.4 mmHg, <1.2 mEq L-1 and <0.03 in PaCO₂, HCO₃- and pH, respectively. Cold storage in glass syringes resulted in the smallest mean alteration in PaO₂ (≤10.28 mmHg).

Conclusions and Clinical Relevance: ABG from alpacas should be stored on ice in glass syringes to reduce variability in PaO₂ if analysis is delayed. In contrast to human reports, the PaO₂ of cooled hyperoxygenated camelid blood increases following storage in plastic syringes.