The Science Journal of the American Association for Respiratory Care

2000 OPEN FORUM Abstracts

CONTINUOUS ARTERIAL BLOOD GAS MONITORING ACCURACY AND RELIABILITY - THIS TIME THROUGH AN UMBILICAL ARTERY CATHETER (UAC)

Patricia Meyers RRT, Catherine Worwa RCP, Robert Trusty RRT, Mark Mammel MD. Infant Pulmonary Research Center, Children's Hospitals and Clinics, St. Paul, MN

Introduction: Arterial blood gases (ABG) are a necessary diagnostic parameter in the management of critically ill neonates. Can an intravascular blood gas sensor, adapted for use through a UAC, be a viable alternative to discrete blood gas analysis?

Methods: We evaluated the Neotrend? (Diametrics Medical, Inc) intravascular blood gas sensor in 23 consecutive neonates (weight 1.8±1.3 kg., gestational age 31±6 weeks) with respiratory failure. Data was collected to compare successful placement, sensor longevity, and bias and precision in low (L3-L4) and high (T8-T11) UAC placement. The sensor is fiberoptic, using fluorescent technology for the measurement of PO2, and optical absorption to measure pH and PCO2, with a thermocouple for temperature. The sensors were inserted via a 4.0 or 4.5 Fr. UAC and extended 20 mm beyond its tip, in the descending aorta.

Results: Duration of use was 1 to 304 hrs. In high position, range from 3 to 304 hrs, in low position from 1 to 91 hrs. 9 sensors were used >72 hrs, 1 in low and 8 in high position. 9 sensors were placed in low position with a success rate of 56%; 18 sensors were placed in high position with a success rate of 89%. ABG's were obtained as clinically indicated, and analyzed using an ABL 725. Sensor measurements were recorded at ABG sampling. Statistical analysis included determination of bias (B) and precision (P) by Bland-Altman technique and linear regression (r).

ABL - Neotrend
Combined Data High Position Low Position
B-P r B-P r B-P r
pH 0.00±0.03 0.88? 0.00±0.03 0.87? 0.03±0.04 0.86?
PCO2 (mmHg) -3±4 0.87? -2±4 0.87? -4±5 0.77?
PO2 (mmHg) 4±14 0.80? 4±14 0.79? 6±14 0.88?
? p<0.0001


Conclusions:
Neotrend? was accurate and reliable in the neonatal setting. Catheter placement in high position increases the likelihood of successful sensor placement and longevity. We found Neotrend? to be a viable alternative to discrete blood gas measurements in critically ill neonates.
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