Accuracy and utility of a continuous inta-arterial blood gas monitoring system in pediatric patients

Objectives: To determine the accuracy of the Paratrend 7 continuous intra-a rterial blood gas monitor (CI-ABGM) in radial and femoral artery catheters placed in children compared with simultaneous measurements of pH, Pa-CO2, a nd Pao, performed by intermittent blood gas analysis. To determine sensor l ongevity in pediatric patients at different arterial sites. To determine th e utility of CI-ABGM for tracking unanticipated events related to blood gas deterioration. Setting. A pediatric intensive care unit of a university hospital. Design: A prospective clinical investigation. Patients: Fifty critically ill pediatric patients, ranging in age from 1 wk to 18 yrs of age, who required either radial or femoral artery catheters f or intermittent arterial blood gas monitoring. Interventions: None. Measurements and Main Results: A Paratrend 7 intra-arterial sensor was plac ed through either an 18- or 20-gauge catheter previously inserted into the radial or femoral artery. At clinically predetermined intervals ranging fro m every 1 to 8 hrs, the CI-ABGM measurements of pH, P-CO2, and Po-2 were co mpared with the values determined by standard intermittent blood gas analys is. The Paratrend 7 system values were individually adjusted to match BEG r esults when the Paratrend 7 pH differed by greater than +/-0.05 units, P-CO 2 was greater than +/-5 torr (0.7 kPa), and Po-2 was greater than +/-15% of the ABG value. Significant aberrations in gas exchange defined as unantici pated events were categorized as isolated metabolic acidosis (pH <7.20), hy percapnia (P-CO2, >70 torr; 9.3 kPa), and hypoxemia (P-O2, <50 torr; 6.7 kP a). All unanticipated events were earmarked from consecutive monitoring epo chs ranging from 4 to 24 hrs duration from the time of Paratrend 7 sensor i nsertion to the time of sensor removal. Fifteen sensors were placed into th e radial artery, 34 sensors were placed into the femoral artery, and one se nsor was initially placed in the radial and moved to a femoral artery locat ion. Mean radial artery insertion duration was 35 hrs. Mean femoral artery duration was 137.2 hrs. A total of 1445 pairs of ABG results were available for comparison. After removal of individual values, which did not meet inc lusion criteria, 1411 pH data pairs, 1408 P-CO2 data pairs, and 1326 P-O2 d ata pairs were analyzed. The bias and precision for the pH data were 0.00 a nd 0.04 units, respectively; for the P-CO2 data were -0.4 and 4.8 torr (-0. 05 and 0.64 kPa), respectively; and for the P-O2 data 1.0 and 25 torr (0.1 and 3.3 kPa), respectively. Detection of unanticipated events was evenly sp read across the three categories and was most commonly related to iatrogeni c causes or cardiac failure. Persistent waveform dampening necessitating se nsor removal was more frequently encountered in radial placement compared t o femoral placement. Conclusions: The Paratrend 7 CI-ABGM is accurate within the extremes of phy siologic gas exchange typically encountered in the pediatric intensive care setting. The device is capable of tracking extreme fluctuations in gas exc hange with a response rate suitable for making real-time therapeutic decisi ons. The sensor can be recommended for insertion into a femoral artery cann ula. There is a high incidence of blood pressure waveform dampening encount ered in radial artery use.