Chest
Volume 111, Issue 1, January 1997, Pages 174-179
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Clinical Investigations in Critical Care
The DCO2 Measured by Gastric Tonometry Predicts Survival in Children Receiving Extracorporeal Life Support: Comparison With Other Hemodynamic and Biochemical Information

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Study objective

To assess the role of gastric tonometry in monitoring children receiving extracorporeal life support (ECLS) and to determine if Dco2 or pHi in the weaning phase of ECLS predicts survival.

Design

A prospective study of consecutive patients treated with ECLS.

Setting

A tertiary pediatric ICU that is the ECLS referral center for Australia.

Patients

Twenty consecutive children receiving ECLS for cardiovascular or respiratory failure. Interventions: All children were monitored throughout their ECLS course using a tonometer inserted into the stomach via the orogastric route. The Pco2 in the tonometer balloon was measured every 4 to 6 h and the pHi was calculated using the Henderson-Hasselbalch equation. The Dco2, which is the difference between Pco2 in tonometer saline solution and arterial blood, was calculated. We compared the ability of pHi, Dco2, heart rate, mean arterial pressure, arterial pH, base deficit, and blood lactate to predict death or survival during the weaning phase. Measurements were taken on the lowest level of support, which for veno-arterial extracorporeal membrane oxygenation and ventricular assist device was defined as the lowest ECLS pump flows, and on veno-venous extracorporeal membrane oxygenation was defined as the time of lowest ECLS gas flow. Predictive power was assessed using the receivor operating characteristic (ROC) analysis on the data collected at these times.

Results

In the weaning phase of ECLS, the pHi was significantly lower in children who died (pHi=7.21; 95% confidence intervals, 7.14 to 7.28) than in those who survived (pHi=7.38; 95% confidence intervals, 7.28 to 7.47). The Dco2 was significantly higher in children who died (23.6 mm Hg; 95% confidence intervals, 14.3 to 33.1) compared with survivors (4.7 mm Hg; 95% confidence intervals, −0.78 to 10.1). The area under the ROC curve was 0.95 for Dco2 (and 0.88 for pHi). pHi and Dco2 predicted survival better than base deficit (area under ROC curve, 0.82), blood lactate level (0.29), arterial pH (0.65), heart rate (0.62), and mean arterial pressure (0.74). Conclusions: Dco2 is a clinically meaningful measurement in children receiving ECLS. A high DCO2 was a good predictor of death in this series. Gastric tonometry may provide a useful measure of the adequacy of regional perfusion and oxygenation in this group of patients.

Section snippets

Clinical Series

Twenty consecutive patients who required ECLS for circulatory shock or hypoxemia were studied prospectively. This study was approved by the Hospital Ethics Committee on Human Research and informed consent was obtained from the parents of all children enrolled. We used the same technique as Krafte-Jacobs et al,10 introducing a 7F adult sigmoid tonometer (TRIP Sigmoid Catheter; Tonometrics, Inc; Bethesda, Md) into the stomach lumen via the orogastric route. All patients had a tonometer passed

RESULTS

In this series of 20 children receiving ECLS, there were 12 deaths and 8 survivors. The patient characteristics and indications for ECLS are outlined in Table 1. The deaths occurred while receiving ECLS in 7 children, and from 2 to 30 days after decannulation in the other 5. There have been no deaths after discharge from the ICU. The first PiCO2 measurement and first PaCO2 measurement for each patient after stabilization on a regimen of ECLS, taken anytime from 0.5 to 8 h after cannulation, are

DISCUSSION

We have shown that measures made by gastric tonometry predict survival and death in children receiving ECLS. The finding that Dco2 had greater predictive power than pHi suggests that Dco2 is a more specific indicator of poor regional perfusion. The pHi calculation is influenced by systemic metabolic acidosis, as arterial blood bicarbonate concentration is part of the Henderson-Hasselbalch equation. In addition, there is no correction in the pHi calculation for the influence of PaCO2 on PiCO2.

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