Friday, July 27, 2012

DKA Management

Above is a useful algorithm for the management of DKA, taken from CMAJ's 2003 paper (a classic and must-read for medicine residents):

Diagnosis and treatment of diabetic ketoacidosis and the hyperglycemic hyperosmolar state 

Added management pearls:

- Many people find it convenient to manage DKA by a flowchart updated ~hourly (although not everything needs to be checked hourly). You may want to record:
Time, Vitals, urine output, pH, HCO3, AG, Ket, Glu, K, PO4, IV fluid rate, insulin dose

-Ketones may increase even though the anion gap is decreasing. This is because beta-hydroxybutyrate (major ketoacid of DKA) is not detected by the ketone test. It is then metabolised to acetoacetate, which is detected.

-When calculating the anion gap, use the uncorrected sodium concentration. Note that even though we see hyponatremia in hyperglycemic states (and there is a "correcting calculation"), the anion gap reflects the balance between positively and negatively charged electrolytes in the extracellular fluid. Glucose is electrically neutral and does not directly alter the anion gap. However, glucose is osmotically active so water is pulled into the extracellular fluid. This has a dilutional effect on all extracellular electrolyte concentrations, both positive or negative, and so the anion gap is minimally altered.

- Use of bicarbonate is reserved for severe acidosis (pH<7.0) after 1 hour of rehydration

- Expect to see non-anion gap metabolic acidosis (ie. hyperchloremic) after AGMA resolves, because of loss of ketone bodies without H+ (i.e. loss of anion with Na+/K+ as cation). This is equivalent to the loss of a "potential bicarbonate". This lost bicarbonate is replaced by chloride ion (which is abundant in the saline we are giving).

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