A 26-year-old man presents with abdominal pain and vomiting. He drinks alcohol regularly and smokes marijuana. On examination, there is epigastric tenderness with guarding. Vitals: BP 100/60, PR 100/min, T 37.5

His VBG:pH  7.47            (Mild Alkalosis) 

pCO2  66  mmHg           (elevated)

HCO3  47  mmol/l           (elevated)  —->  Metabolic Alkalosis 

Expected PCO2 = (0.7x HCO3) + 20  = 0.7×47 + 20 = 52.9   Obserserved >Expected 

BE  19       +ve in Alkalosis

Na  131  mmol/l           (low)

K  2.9  mmol/l               (low)

Chloride  80  mmol/l            (Low)

Creatinine  321  umol/l        (elevated)

Glucose  6.8  mmol/l

Lactate  1.8  mmol/l

Interpretation:

Hypochloremic Metabolic Alkalosis with Respiratory acidosis

Causes of Metabolic Alkalosis:

Most common causes: vomiting, diuretics, incr aldosterone

Chloride loss (saline responsive, Urine Cl <10)

kidney reabsorbs HCO3 > Cl to maintain electroneutrality
aka contraction alkalosis (fluid loss – decr renal perfusion – incr aldosterone – loss H/reabsorp HCO3)
GI: vomiting, NG suction
GU: diuretics
Skin loss: burns

Potassium loss (saline resistant), Urine Cl >10, often hypertensive)
Syndromes: Cushings, Conns, Bartters
Eating disorders
Excess liquorice

Excess base (saline resistant, Urine Cl >10, normotensive)
Antacids, milk-alkali, bicarb, citrate (dialysis, transfusion)