From the Guidelines
Venous blood gas (VBG) findings in diabetic ketoacidosis (DKA) typically reveal metabolic acidosis with a pH less than 7.3 and bicarbonate levels below 18 mEq/L, as stated in the most recent and highest quality study 1.
Key Findings
- The anion gap is elevated, usually greater than 12 mEq/L, due to the accumulation of ketone bodies (acetoacetate, beta-hydroxybutyrate, and acetone) 1.
- Blood glucose levels are markedly elevated, generally above 250 mg/dL, as indicated by the DKA diagnostic criteria 1.
- Potassium levels may initially appear normal or elevated despite total body potassium depletion due to the acidosis-driven shift of potassium from intracellular to extracellular spaces.
- The VBG will also show an increased base deficit, reflecting the severity of the acidosis.
- Lactate levels may be mildly elevated.
- PCO2 is often decreased as a respiratory compensation mechanism for the metabolic acidosis.
Pathophysiology and Treatment
These findings reflect the underlying pathophysiology of DKA, where insulin deficiency leads to hyperglycemia, lipolysis, and ketone body production, resulting in metabolic acidosis 1. Serial VBG measurements are essential during treatment to monitor the resolution of acidosis and guide fluid and electrolyte replacement therapy, as recommended in the study 1.
Monitoring and Management
- Blood should be drawn every 2–4 h for determination of serum electrolytes, glucose, blood urea nitrogen, creatinine, osmolality, and venous pH (for DKA) 1.
- Generally, repeat arterial blood gases are unnecessary; venous pH (which is usually 0.03 U lower than arterial pH) and anion gap can be followed to monitor resolution of acidosis 1.
From the Research
VBG Findings in DKA
- The diagnostic accuracy of venous blood gas (VBG) electrolytes for identifying diabetic ketoacidosis (DKA) has been evaluated in several studies 2.
- A study found that VBG electrolytes were 97.8% sensitive and 100% specific for the diagnosis of DKA in hyperglycemic patients, with a correlation coefficient of 0.94 for bicarbonate and 0.81 for anion gap between VBG and serum chemistry electrolytes 2.
- Another study investigated the utility of venous bicarbonate concentration in predicting arterial pH in adults with DKA, and found that a serum venous bicarbonate concentration of ≤20.6 mEq/L predicted arterial pH ≤7.3 with over 95% sensitivity and 92% accuracy 3.
- The use of VBG electrolytes can potentially replace the need for serum chemistry analysis in diagnosing DKA, making it a more efficient and cost-effective option 2.
- DKA is characterized by the triad of hyperglycemia, ketosis, and anion gap metabolic acidosis, and can be diagnosed using criteria such as serum glucose ≥ 250 mg/dL, serum anion gap > 10 mEq/L, bicarbonate ≤ 18 mEq/L, serum pH ≤ 7.30, and presence of ketosis 4, 5, 6.