Correct!
5. All of the above
There are a number of common causes of an elevated anion gap metabolic acidosis which can be quickly excluded. Diabetic ketoacidosis is possible because the patient has diabetes and an elevated blood sugar, however, his urine ketones were negative. Lactic acidosis is commonly do to poor tissue perfusion and our patient has another potential cause, his metformin which can cause a lactic acidosis.
One way of narrowing the differential diagnosis is by calculating the osmolal gap. Sodium, chloride, bicarbonate, glucose, and urea are normally the most important
osmotically active particles in the serum. The calculated serum osmolality is determined by (3):
Serum Osmolality = (2 x (Na + K)) + (BUN/2.8) + (glucose/18) + serum (alcohol/4.6)
A difference between the calculated osmolality and the measured osmolality of >10 mOSM indicates the presence of a molecule significantly raising the serum osmolality. Our patient’s calculated serum osmolality calculated osmolality is (2 x (129 + 4.7)) + (10 / 2.8) + (395 / 18) + (0 / 4.6) = 292 mOSM but his measured osmolality was 333 mOSM.
Which of the following are the common cause(s) of an anion gap acidosis with an elevated osmolal gap? (Click on the correct answer to be directed to the fifth of six pages)