A 45 year old male is brought to the ER unconscious. He is afebrile. His pupils are regular, equal and 4mm. they are reactive to light. His glucometer reading is 487. His Physical examination is unremarkable. He is taking shallow breaths at the rate of 18/minute. Hie ABG shows pH 7.1, HCO3 7, pO2 87, pCO2 32. His Na131, K3.3, CL 87, HCO3 is 8, BUN 42, Cr1.3 .
Q1. Which of the following is the most appropriate description of his acid/base situation?
The answer is choice 2. In a case with metabolic acidosis, The pCO2 is equal to the HCO3 x 1.5 + 4. The difference on each side of the equation should not be more than 2. If the pCO2 is higher than that predicted by the formula (as it is in this case), then there is respiratory acidosis. If the HCO3 is higher than predicted, there is additional metabolic alkalosis.
Q2. The patient recovers fully from his current crisis and is sent home. He sees you regularly for the next few years. At one point you see that his potassium is 5.8. Na is 138, Cl is 110, HCO3 is 20, BUN & Cr are stable. ABG shows a pH of 7.27. Which of the following mechanisms are responsible for his metabolic disturbance?
The answer is choice 3. This is a case of metabolic acidosis with a normal anion gap. There is hyperkalemia too. The Renal tubular acidoses are important for the exam. Type 4 is the only one that has hyperkalemia. The underlying mechanism for type 4 is hyporeninemic hypoaldosteronism. Types 1 & 2 have hypokalemia and will be discussed later.