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

OBJECTIVES

To determine the accuracy of the Paratrend 7 continuous intra-arterial blood gas monitor (CI-ABGM) in radial and femoral artery catheters placed in children compared with simultaneous measurements of pH, Pa(CO2), and Pa(O2) performed by intermittent blood gas analysis. To determine sensor longevity in pediatric patients at different arterial sites. To determine the 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 for intermittent arterial blood gas monitoring.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A Paratrend 7 intra-arterial sensor was placed through either an 18- or 20-gauge catheter previously inserted into the radial or femoral artery. At clinically predetermined intervals ranging from every 1 to 8 hrs, the CI-ABGM measurements of pH, P(CO2), and P(O2) were compared with the values determined by standard intermittent blood gas analysis. The Paratrend 7 system values were individually adjusted to match ABG results when the Paratrend 7 pH differed by greater than +/-0.05 units, P(CO2) was greater than +/-5 torr (0.7 kPa), and P(O2) was greater than +/-15% of the ABG value. Significant aberrations in gas exchange defined as unanticipated events were categorized as isolated metabolic acidosis (pH <7.20), hypercapnia (P(CO2), >70 torr; 9.3 kPa), and hypoxemia (P(O2), <50 torr; 6.7 kPa). All unanticipated events were earmarked from consecutive monitoring epochs ranging from 4 to 24 hrs duration from the time of Paratrend 7 sensor insertion to the time of sensor removal. Fifteen sensors were placed into the radial artery, 34 sensors were placed into the femoral artery, and one sensor was initially placed in the radial and moved to a femoral artery location. 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 inclusion criteria, 1411 pH data pairs, 1408 P(CO2) data pairs, and 1326 P(O2) data pairs were analyzed. The bias and precision for the pH data were 0.00 and 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 spread across the three categories and was most commonly related to iatrogenic causes or cardiac failure. Persistent waveform dampening necessitating sensor removal was more frequently encountered in radial placement compared to femoral placement.

CONCLUSIONS

The Paratrend 7 CI-ABGM is accurate within the extremes of physiologic gas exchange typically encountered in the pediatric intensive care setting. The device is capable of tracking extreme fluctuations in gas exchange with a response rate suitable for making real-time therapeutic decisions. The sensor can be recommended for insertion into a femoral artery cannula. There is a high incidence of blood pressure waveform dampening encountered in radial artery use.