Diabetic ketoacidosis: venous blood may be used to assess the degree of acidosis.

Clinical bottom line (level 4)

  1. Venous blood pH and bicarbonate levels correlated closely in patients with diabetic ketoacidosis.
Brandenburg and Dire: Annals of Emergency Medicine 1998; 31: 459-465
Expires October 2003

The study

Setting: emergency department, university hospital, USA

38 patients (aged mean 35 years, 53% male) with 44 suspected episodes of diabetic ketoacidosis (capillary glucose >14 mmol/l, ketonuria and clinical suspicion)

Excluded if
  • not acidotic
  • no ketonaemia
  • not hyperglycaemic
  • incomplete investigations



    • Independent unblinded reference standard, applied in all patients from a consecutive ?appropriate spectrum.
    Reference standard:
    • arterial blood analysis taken before treatment with fluids or insulin and sample transported on ice. DKA defined as arterial pH <7.35 or serum CO2 M20 nM, serum glucose >14 mmol/l and ketonaemia.
    Diagnostic test: venous sample taken as near, temporally, as possible to the arterial sample (analysed using same machine)

    The evidence

    • mean difference (SD) in pH:
      • control group 7.20 (0.14)
      • experimental group 7.17 (0.13)
      • mean difference (95% CI) 0.03 (0.0 to 0.06)
    • mean difference (SD) in HCO3:
      • control 11.0 (6.0)
      • experimental 12.8 (5.5)
      • mean difference (95% CI) 1.8 (0.48 to 3.2)
      • Arterial and venous pH correlated closely (r=0.969)
      • Arterial and venous HCO 3 correlated closely (r=0.954)

    Comments

    1. Convenience sample and small numbers makes these results less certain. They may not necessarily be true in patients with severe acidosis or hypotension.
    2. The study demonstrates not only that venous pH measurement is reliable but also accurate when measured against arterial pH.
    3. Bland Altman plots used to show the level of agreement between arterial and venous results. In only one case did the venous pH exceed the arterial pH by more than 0.1.

    Citation

    1. Brandenburg MA, and Dire DJ: Comparison of arterial and venous blood gas values in the initial emergency department evaluation of patients with diabetic ketoacidosis. Annals of Emergency Medicine 1998; 31: 459-465
    Contributor: Richard Hardern and Chris Ball, July 2000
    Reviewer: Jon Levine

    Clinical Question.
    Patient suspected DKA
    Intervention or Exposure venous blood sample
    Outcome diagnosis