Critical Care: Mechanical Ventilation & Respiratory Failure II |

Is Venous Blood Gas on Admission Predictive of Intubation During Acute on Chronic Respiratory Failure? FREE TO VIEW

Lisa Domaradzki, MD; Sahiti Gosala, MD; Khaled Iskandarani; Andry Van de Louw, MD
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Penn State Milton S. Hershey Medical Center and College of Medicine, Hershey, PA

Copyright 2016, American College of Chest Physicians. All Rights Reserved.

Chest. 2016;150(4_S):316A. doi:10.1016/j.chest.2016.08.329
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SESSION TITLE: Mechanical Ventilation & Respiratory Failure II

SESSION TYPE: Original Investigation Poster

PRESENTED ON: Wednesday, October 26, 2016 at 01:30 PM - 02:30 PM

PURPOSE: Arterial blood gas (ABG) analysis is part of the assessment during COPD exacerbation, and arterial pH has been shown to predict non-invasive ventilation (NIV) failure, a risk factor for mortality. Venous blood gas (VBG) has gained popularity in Emergency Departments (ED) as a substitute for ABG, as studies have shown a good agreement between venous and arterial values for pH or PCO2. We aimed to investigate whether initial VBG can predict requirement for intubation during acute on chronic respiratory failure.

METHODS: Retrospective chart review of patients admitted to the ED between 2004 and 2014 with acute on chronic respiratory failure and who had VBG performed before initiation of any mechanical ventilation. Demographic, clinical and biological data were collected throughout the hospital course. Do not intubate (DNI) and tracheostomized patients were excluded.

RESULTS: We included 151 patients (83 males, 68 females), 117 had COPD, 74 patients were on home O2, 23 on home CPAP or BIPAP. Sixty nine patients required NIV. Mean±SD values were 68±12 for age and 7.31±0.06, 67±22 mmHg, 34±10 mmol/L for venous pH, PCO2 and bicarbonates respectively. As compared to intubated patients (n=24), non-intubated patients (n=127) had a higher Glasgow Coma Score (14.8±0.9 versus 13.6±2.5, p=0.03) but no significant difference in venous pH (7.32±0.06 versus 7.29±0.07, p=0.08), PCO2 (66±22 versus 71±19 mmHg, p=0.33) or bicarbonates (34±10 versus 34±9 mmol/L, p=0.98) was observed. ROC curve showed poor sensitivity and specificity of venous parameters for prediction of intubation with an AUC of 0.37 for pH. Hospital mortality was 7% (n=11), without significant differences in VBG associated with mortality. As compared to patients not requiring NIV (n=82), patients started on NIV (n=69) had lower venous pH (7.30±0.06 versus 7.33±0.06, p=0.005) and higher PCO2 (74±24 versus 61±17 mmHg, p=0.005) and bicarbonates (36±10 versus 32±9 mmol/L, p=0.04), and among this group patients who subsequently required intubation (n=16) had lower venous PCO2 (63±17 versus 77±25 mmHg, p=0.02) and bicarbonates (31±8 versus 37±10 mmol/L, p=0.03) than non-intubated patients, while their pH was not significantly different (7.30±0.08 versus 7.30±0.06, p=0.78).

CONCLUSIONS: During acute on chronic respiratory failure, VBG on admission is poorly predictive of intubation and hospital mortality. Further studies are warranted to delineate the role of VBG versus ABG in these patients.

CLINICAL IMPLICATIONS: Arterial pH and changes in arterial pH during NIV have been shown to predict requirement for intubation during COPD exacerbation and are therefore used for clinical-decision making. As a good agreement between arterial and venous pH and PCO2 has been shown, VBG are sometimes used as substitutes for ABG in initial ED evaluation of acute on chronic respiratory failure. Our results show that venous pH and PCO2 are poorly predictive of intubation and outcome in this setting and therefore cannot fully replace ABG for clinical decision-making. Further studies comparing dynamic changes in ABG and VBG during NIV and their ability to predict outcome would be warranted.

DISCLOSURE: The following authors have nothing to disclose: Lisa Domaradzki, Sahiti Gosala, Khaled Iskandarani, Andry Van de Louw

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