Venous Blood Gas Sampling in Diabetic Ketoacidosis
Venous Blood Gas Sampling in Diabetic Ketoacidosis
ABSTRACT & COMMENTARY
This study examined the correspondence between arterial and venous blood gas results in ED patients presenting with diabetic ketoacidosis (DKA). Patients were enrolled if they had a serum glucose of more than 250 mg/dL, urine ketones, and clinical suspicion of DKA. Arterial and venous blood gas samples were drawn at approximately the same time and analyzed identically. Brandenberg and Dire determined the agreement between pH and bicarbonate results by arterial and venous sampling.
Forty-four episodes of confirmed DKA were analyzed. Venous pH was an extremely strong predictor of arterial pH. The mean difference in pH between the two measures was 0.03 with a range of 0-0.11. Only one case had an arterial-venous pH difference of more than 0.1. The two samples correlated highly (r2 = 0.94). Extremely strong agreement was also demonstrated between arterial and venous bicarbonate. The authors conclude that venous blood gas measurement reliably determines the extent of acidosis in ED patients with DKA (Brandenberg MA, Dire DJ. Comparison of arterial and venous blood gas values in the initial ED evaluation of patients with diabetic ketoacidosis. Ann Emerg Med 1998;31:459-465).
COMMENT BY DAVID KARRAS, MD, FACEP
This is one of the handful of studies published each year that is likely to have an immediate effect on bedside patient management. Arterial blood gas measurement, with its attendant pain and risk, has been regarded as a necessary diagnostic evil in DKA. While the agreement between arterial and venous pH has been intermittently documented over the years, few ED physicians have been willing to make the leap of faith necessary to report venous blood gas samples to the admitting physician. This study provided welcome justification for avoiding arterial puncture in many patients with DKA.
A few caveats are warranted. The sample size is small, although I believe that the extraordinarily strong agreement between arterial and venous results justifies clinical application. Importantly, more than one-third of enrolled cases were retrospectively excluded when they did not fulfill criteria for DKA upon further testing. Those included in the final analysis were unlikely to have mixed acid-base disorders, and the use of venous blood gas sampling in patients with complicated metabolic abnormalities is not addressed. I am, therefore, hesitant to generalize these results; I would rely on venous blood gas results only when a straight-forward diagnosis of DKA is being entertained.
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