Property of Dr. Fady, Department of General Surgery, Faculty of Medicine, University of Zagazig, Egypt

1. Acid – Base Disorders

2. Normal Values
Arterial Venous
pH 7.40 <7.35
HCO3 24 24
pCO2 40 >40
pO2 >70 <60

3. Four Main Acid-Base Disorders
Disorder Primary
Alteration
Secondary
Response
Mechanism of
Response
Metabolic
Acidosis
in plasma
HCO3
in plasma
pCO2
Hyperventilation
Metabolic
Alkalosis
in plasma
HCO3
increase in
pCO2
Hypoventilation
Respiratory
Acidosis
in plasma
pCO2
in plasma
HCO3
Increase in acid
excretion; increase in
reabsorption of HCO3
Respiratory
Alkalosis
in plasma
pCO2
in plasma
HCO3
Suppression of acid
excretion; decrease in
reabsorption of HCO3

4. Step by Step
1. Determine the primary disturbance:
 Acidemia or Alkalemia: look at the pH
< 7.40 = acidemia
> 7.40 = alkalemia
 Respiratory or Metabolic: look at HCO3 and CO2
HCO3 = primary metabolic acidosis
pCO2 = primary respiratory acidosis
and vice versa for alkalosis

5. Pneumonics for pnuemonic lovers
Metabolic
Acidosis Anion
Gap
“MUDPILERS”
Metabolic
Acidosis Non-
Gap
“HARDUPS”
Acute Resp.
Acidosis
“anything
causing
hypoventilation”
Metabolic
Alkalosis
“CLEVERPD”
Respiratory
Alkalosis
“CHAMPS”
•Methanol
•Uremia
•DKA/Alcoholic
ketoacidosis
•Paraldehyde
•Isoniazid
•Lactic acidosis
•Ethanol
•Renal
failure/Rhabdo
•Salicylates
•Hyperalimentation
•Acetazolamide
•Renal Tubular
Acidosis
•Diarrhea
•Uretero-Pelvic
shunt
•Post-hypocapnia
•Spironolactone
•CNS depression
•Airway
obstruction
•Pulmonary
edema
•Pneumonia
•Hemo/Pneumo
thorax
•Neuromuscular
•Contraction
•Licorice
•Endocrine
(Conn/Cushing
/Bartters)
•Vomiting
•Excess alkali
•Refeeding
•Post-
hypercapnia
•Diuretics
•CNS disease
•Hypocapnia
•Anxiety
•Mech. Ventilation
•Progesterone
•Salicylates
•Sepsis

6. Organ dysfunction
 CNS – respiratory acidosis (suppression) and
alkalosis (stimulation)
 Pulmonary – respiratory acidosis (COPD) and
alkalosis (hypoxia, pulmonary embolism)
 Cardiac – respiratory alkalosis, respiratory acidosis,
metabolic acidosis (pulmonary edema)
 GI – metabolic alkalosis (vomiting) and acidosis
(diarrhea)
 Liver – respiratory alkalosis, metabolic acidosis (liver
failure)
 Kidney – metabolic acidosis (RTA) and alkalosis (1st
aldosteone)

7. Organ Dysfunction
 Endocrine
 Diabetes mellitus – metabolic acidosis
 Adrenal insufficiency – metabolic acidosis
 Cushing’s – metabolic alkalosis
 Primary aldosteronism – metabolic alkalosis
 Drugs/toxins
 Toxic alcohols – metabolic acidosis
 ASA – metabolic acidosis and respiratory alkalosis
 Theophylline overdose – respiratory alkalosis