8 Steps To Solving Acid-Base Problems 1. Is the patient acidemic or alkalemic? 2. What is the minimum diagnosis? 3. Calculate the anion gap Anion gap = (Na+) – ( HCO3

-) – (Cl-) 4. Calculate the delta gap ∆gap = anion gap - 12 5. Calculate the "starting bicarbonate" “starting bicarbonate” =∆gap + (HCO3

-) 6. Calculate compensation (if necessary) “compensated PaCO2” =1.5(HCO3

-) + 8 7. List all of acid-base disorders identified 8. Clinical correlation

Primary Disorder Expected Compensation Metabolic Acidosis PaCO2=1.5(HCO3

-) + 8 Metabolic Alkalosis ∆PaCO2=0.6(∆HCO3

-) Respiratory Acidosis Acute (∆HCO3

-)=0.10∆PaCO2 Chronic (∆HCO3

-)=0.35∆PaCO2Respiratory Alkalosis Acute (∆HCO3

-)=0.2∆PaCO2 Chronic (∆HCO3

-)=0.5∆PaCO2

Anion Gap Acidosis M=methanol U=uremia D=DKA P=paraldehyde I=iron,isoniazid/ibuprofen/inhalents/CN/strychnine/toluene L=lactate:shock,sepsis,CHF,hypoxia,anemia,CO,CN,metformin,

ischemic bowel/liver fx/seizures/leukemia/inborn errors(G6PD, fructose 1,6 diphosphatase, pyruvate carboxylase or dehydrogenase, malignancy,heat stroke,D-lactic acidosis,mitochondrial myopathies) E=ethanol/ethylene glycol S=salicylate, solvents, starvation ketoses Hyperchloremic Metabolic Acidosis Loss of bicarbonate from kidney or GI (replaced by HCl)

Gain of HCl (hyperalimentation-cationic acids from H+) Renal loss (RTA, obstrx) Positive (+20)Urine Anion Gap (UAG)

UAG= (Na+)+(K+)-(Cl-) normal is Negative GI loss (diarrhea, fistula, ileostomy,cholestyramine)neg UAG (-20)

Ingestion of CaCl2, MgCl2Diamox, hypoaldosteronism,hyperparathyroidism,

Rapid NS hydration, post-tx DKA (replace HCO3- with Cl-)

Acid-Base Workbook Page 2 of 2

Metabolic Alkalosis UCl-<15=”chloride responsive” Vomiting NG suction Volume contraction Diuretics

Cystic Fibrosis Posthypercapnea Alkali syndrome

UCl->15=”chloride resistant” Hypercortisolism (Cushing or Conn’s) Hyperaldosteronism (1o or 2o)

2o:CHF,cirrhosis,ascites,malig HTN Sodium bicarbonate therapy Severe renal artery stenosis Bartter,licorice,renin-tumor,chewing tob

Liddles,severe K dep,cong adrenal hyper MISC:refeeding alkalosis, non-parathyroid↑Ca Respiratory Alkalosis Early shock Early sepsis Fear, anxiety Pulmonary dz (CHF,asthma, pneumonia,PE) CNS infection or CVA Pregnancy Liver disease Hyperthyroidism Salicylates (adults) Respiratory Acidosis CNS depression Paralysis of respiratory muscles Airway obstruction Respiratory failure Chronic lung disease Extreme kyphoscoliosis Pickwickian syndrome