ANALYSIS OF ACID-BASE DISORDERS
...CO2 = 48 mmHg Bicarbonate 36 mmol/l Metabolic alkalosis Causes of metabolic alkalosis pH 7.2 PCO2= 21mmHg Bicarbonate 8 mmol/l Metabolic acidosis Types of Metabolic acidosis Anion Gap Metabolic acidosis Non-Anion Gap Metabolic acidosis Anion Gap = Na-(Cl + Bicarbonate) = 12+2 Causes of Anion Gap Metabolic acidosis Ketoacidosis Diabetic Alcoholic Renal failure Lactic acidosis Rhabdomyolysis Toxins Methanol Ethylene glycol Paraldehyde Salicylates Causes of Non-Anion Gap Metabolic acidosis GI bicarbonate loss Diarrhea Ureteral diversions Renal bicarbonate loss Renal tubular acidosis Early renal failure Carbonic anhydrase inhibitors Aldosterone inhibitors Hydrochloric acid administration Mixed Acid-Base Disorders Use the rule of thumb Look at the pH Check electrolyte and calculate anion gap Calculate the excess anion gap (total anion gap – normal anion gap {12 mmol/l}, add this value to the measured bicarbonate concentration) If the sum of the excess anion gap and the measure bicarbonate is greater than normal serum bicarbonate concentration (normal range 23 to 30 mmol/l) then an underlying metabolic alkalosis is present. If the sum is less than a normal bicarbonate concentration then an underlying non-gap metabolic acidosis is present. If the anion gap is 20 mmol/l or greater, then metabolic acidosis is present regardless of the pH or serum bicarbonate concentration. The greater the anion gap, the more likely it is that a specific metabolic acidosis will be found. The relation between level of Anion Gap and Biochemical Diagnoses in 51 patients without renal failure Case 1 pH 7.50 Pco2= 20 mmHg Bicarbonate concentration 15 mmol/l Na 140 Cl 103 mmol/l Anion Gap 140 – (103 + 15) = 22 mmol/l Excess Anion Gap 22 – 12 = 10 mmol/l The sum of Excess anion gap is 10 + 15 = 25 mmol/l Respiratory Alkalosis and metabolic acidosis Case 2 Case 3 pH 7.40 Pco2= 40 mmHg Bicarbonate 24 mmol/l Na 145 Cl 100 mmol/l Anion Gap 145 – (100 + 24) = 21 mmol/l Excess Anion Gap 21 – 12 = 9 mmol/l The sum of Excess anion gap is 9 + 24 = 33 mmol/l Metabolic acidosis and metabolic alkalosis Case 4 pH 7.5 pCo2= 20mmHg Bicarbonate 15 mmol/l Na 145 Cl 100 mmol/l Anion Gap 145 - (100+15) = 30 mmol/l Excess AG = 30 – 12 = 18mmol/l The sum of Excess anion gap is 18 + 15 = ...