Continuous blood gas monitoring using an in-dwelling optode method: comparison to intermittent arterial blood gas sampling in ECMO patients.

INTRODUCTION

The ability to measure postmembrane arterial blood gases is essential in the management of critically ill neonates treated with extracorporeal membrane oxygenation (ECMO). A new technology using, the Paratrend 7 system (Diametrics Medical, High Wycombe,UK) allows for continuous measurement of pH, PCO(2) and PO(2), and calculates oxygen saturation, bicarbonate, and base excess.

OBJECTIVE

To evaluate and compare the results of continuous blood gas measurement using the Paratrend 7 system with a standard system of blood gas analysis in our intensive care unit.

DESIGN

Prospective, controlled, interventional study.

SETTING

The neonatal intensive care unit of a tertiary referral center.

PATIENTS: Neonates who required extracorporeal life support and were expected to have frequent postmembrane arterial blood sampling during the testing period.

RESEARCH DESIGN AND METHOD: To enable Paratrend 7 sensor access to the ECMO circuit, the postmembrane access port extension set that is routinely used for blood drawn for blood gas analysis was used. The study began with the insertion of the Paratrend 7 sensor. Subjects remained on the study until the ECMO was discontinued and/or frequent blood gases were no longer needed. The blood gas results from the Paratrend 7 system were not used in clinical management of the patient. BLOOD GAS MEASUREMENT: During the study period, with each blood sample drawn for laboratory analysis, a printout from the Paratrend 7 monitor was recorded for comparison.

RESULTS

A total of 242 pairs of blood gas samples were collected from 10 neonates. The mean bias/precision for pH was -0.02/0.04; for PO(2) 68.35/93.44 mm Hg; and for PCO(2) 1.75/4.23 mm Hg. The correlation (r value) between the sensor reading and the blood gases were 0.89 for pH, 0.96 for PO(2), and 0.73 for PCO(2) (Table 1).

CONCLUSION

The blood gases compared in the two methods had a strong correlation for pH, PCO(2) and PO(2). Results of this study indicate that this technology provides an accurate means of monitoring continuous blood gas parameters in neonatal ECMO patients. Use of the Paratrend 7 should allow reduced health-care provider exposure to blood and decreased patient iatrogenic blood loss.