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Abstract: TH-PO1125

Diagnostic Accuracy of a Central Venous Blood Gas in the Diagnosis of Acid-Base Disorders in the Medical Intensive Care Unit

Session Information

Category: Fluid, Electrolytes, and Acid-Base

  • 704 Fluid, Electrolyte, Acid-Base Disorders

Authors

  • Schrauben, Sarah J., University of Pennsylvania, Philadelphia, Pennsylvania, United States
  • Negoianu, Dan, University of Pennsylvania, Philadelphia, Pennsylvania, United States
  • Cohen, Raphael M., University of Pennsylvania, Philadelphia, Pennsylvania, United States
  • Berns, Jeffrey S., University of Pennsylvania, Philadelphia, Pennsylvania, United States
Background

Acid-base disturbances are frequently encountered in critically ill patients. Arterial blood gas (ABG) is the gold standard in the diagnosis but has potential hazards to the patient. For patients with a central venous catheter, venous blood gas (VBG) sampling may be an alternative, less-invasive diagnostic tool. However, little is known about the central VBG diagnostic accuracy. The primary objective of this study was to assess the accuracy of a central VBG for the diagnosis of acid-base disorders in critically ill adult patients.

Methods

This was a cross-sectional single blinded study at two university-based urban hospitals. Study participants were adults in a medical intensive care unit (MICU) that had simultaneously drawn ABG and central VBG samples. Expert acid-base diagnosticians, all nephrologists, were blinded to the clinical data and blood gas origin to interpret the acid-base disorder(s) from each sample. Blood gas samples were classified as: no disorder, metabolic acidosis, metabolic alkalosis, respiratory acidosis, respiratory acidosis, or as a mixed disorder. Diagnostic accuracy of central VBG-based diagnoses were compared to ABG-based diagnoses by assessing percent clinical agreement, sensitivity and specificity.

Results

The study involved 23 participants. The most common underlying primary diagnoses were respiratory-related (45.5%) and sepsis-related (40.9%). Overall, the central VBG had 100% sensitivity for metabolic acidosis, metabolic alkalosis, and respiratory acidosis, and 71% for respiratory alkalosis, and high percent clinical agreement, ranging from 75-94%, with a lower agreement of 57% for respiratory alkalosis. VBG-based diagnoses in vasopressor dependent patients (n=13, 56.5%) performed very similarly.

Conclusion

In critically ill adult patients, central VBG detects acid-base disturbances with good diagnostic accuracy, even in shock states. This study supports the use of central VBG for diagnosis of acid-base disturbances in MICU patients.

Diagnostic Accuracy of VBG-based Diagnosis compared to ABG-based Diagnosis.
DisorderSensitivitySpecificity% Clinical Agreement
Metabolic Acidosis100%64%87.5%
Metabolic Alkalosis100%100%75%
Respiratory Acidosis100%60%94%
Respiratory Alkalosis71%100%57%

Funding

  • NIDDK Support