Continuous intra-arterial blood gas monitoring in rats

Abstract

Studies on lung injury and its treatment options are often performed on small animals like rats. Because conventional blood gas analyses may not detect rapid changes in gas exchange during respiratory distress syndrome and intermittent blood withdrawal can result in hypovolaemia and anaemia, we tested the applicability and accuracy of a continuous intra-vascular blood gas monitor (Paratrend 7+). Anaesthetized and ventilated rats with a body weight of 398 ± 45 g (n = 22) had a 20-gauge cannula inserted in both carotid arteries. A photochemical blood gas sensor for continuous measurement (Paratrend 7+) was advanced into the aorta via the left carotid artery. Blood was sampled for intermittent blood gas analysis by means of the right carotid artery. Arterial pO2 was varied by applying different inspiratory oxygen concentrations, and arterial pCO2 by applying different respiratory rates. Paired blood gas measurements (n = 136) were analysed over a wide range of pO2 values (5.3-76.8 kPa). We found an acceptable correlation for pO2 (r2 = 0.98), pCO2 (r2 = 0.96) and pH (r2 = 0.92). The calculated bias and imprecision for pO 2 was -1.0 ± 3.3 kPa, for pCO2 0.04 ± 0.28 kPa and for hydrogen ion concentration -0.05 ± 2.2 nmol/l. We conclude that in rats, continuous blood gas monitoring with a photochemical blood gas sensor provides pO2, pCO2 and pH measurements with acceptable accuracy.