A 70 year-old man is complaining of severe nausea. He has had problems with pept

Question

A 70 year-old man is complaining of severe nausea. He has had problems with peptic ulcer disease and has been having similar pain for the past two weeks. Rather than seeing a physician, he opted to self medicate. Over the past week, he has been consuming large quantities of TUMS (calcium carbonate), an over the counter antacid. While breathing room air, an arterial blood sample is drawn and reveals the following: pH = 7.48, PaCO2 = 49 mm Hg, PaO2 = 68 mm Hg, HCO3? 35 mEq/L, Na+ = 139 mEq/L, K+ = 4 mEq/L, Cl? = 96 mEq/L, and glucose = 387 mg/dL. The most likely explanation for the observed hypoxemia is:

A) hypoventilation that is secondary to a metabolic alkalosis

B) hyperventilation that is secondary to calcium toxicity

c) altitude-induced hyperventilation

d) a leftward shift of the oxyhemoglobin curve

e) hypoventilation that is secondary to diabetic keto acidosis

Explanation / Answer

Ans A) hypoventilation that is secondary to metabolic alkalosis

Due to high use Of antacid TUMS ( calcium carbonate) there is decrease of acidic level eventually leading to increase of of condition metabolic alkalosis. And resulting in hypovolemia ,which leads to secreation of aldosterone and renin and enhance absorption of HCO3 . Persistent metabolic alkalosis reflects inability of kidney to excrete HCO3 . Hence to counter effect of alkalosis respiratory system generate typical response that is hypoventilation leading to pH correction to normal.

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