Acid-Base Disorders Flashcards
What does pH represent?
The [ ] of free hydrogen ions (protons) in circulation
What is normal human pH?
7.4
What pH level of extracellular fluid must be maintained for optimal functioning of body cells?
7.35-7.45
What is pH > 7.4?
alkalosis
What is pH < 7.4?
acidosis
What is an acid?
A molecule that releases hydrogen ions in solution
What is a base?
Any substance that can accept a hydrogen ion (removes free protons from solution)
What are 3 ways the body eliminates acids?
(1) pulmonary excretion of CO2
(2) metabolic utilization of organic acids
(3) renal excretion of nonvolatile acids (H+ + buffers)
Excess CO2 causes a(n) (inc/dec) in H+ leading to an (acidic/alkalotic) pH level in the body.
Inc in H+ → acidic
Excess HCO3- causes a(n) (inc/dec) in H+ leading to an (acidic/alkalotic) pH level in the body.
Dec in H+ → alkalotic
What are 4 sources of H+ gain?
(1) inc CO2
(2) production of phosphoric and sulfuric acids-metabolism of proteins and other organic molecules
(3) loss of bicarb from GI losses
(4) loss of bicarb from urine
What are 2 sources of H+ loss?
(1) loss of H+ in vomit
(2) loss of H+ in urine
Hypoventilation or respiratory diseases result in what?
Retention of CO2→ respiratory acidosis
Hyperventilation results in what?
Blowing off CO2→ respiratory alkalosis
What are 3 common causes of metabolic acidosis?
(1) excess production of lactic acid (>4 mEq/L): severe exercise or seizure, shock/hypoxia
(2) formation of ketone bodies: uncontrolled DM, fasting states
(3) loss of bicarbonate: diarrhea
What is the anion gap?
Difference b/w the plasma [ ] of the major cation (Na+) and the sum of the measured anions (Cl- and HCO3-) → AG = Na+ - [Cl- + HCO3-]
What does the difference of the anion gap represent?
The [ ] of unmeasured anions such as phosphates, sulfates, organic acids and proteins
What is responsible for a normal anion gap?
Excessive bicarbonate loss either intestinally or renally
What 2 things are responsible for an elevated anion gap?
Excess metabolic acid production and impaired elimination of metabolic acids; kidney dysfunction
What is the most common cause of metabolic acidosis in hospitalized pts?
Lactic acidosis
What are the 2 types of lactic acidosis? Describe each and say which is the most common.
Type A (hypoxic): most common
- Dec tissue perfusion→ inc lactic acid production
- Ex: cardiogenic, septic, hemorrhagic shock, carbon monoxide or cyanide poisoning
Type B (metabolic causes):
- Impaired cellular metabolism or tissue ischemia w/o systemic hypoperfusion
- Ex: DKA, alcoholism, infxns, malignancy, metformin, bowel necrosis
What does the AG metabolic acidosis mnemonic MUDPILES stand for?
Methanol Uremia DKA Propylene glycol Isoniazid Lactic acidosis Ethylene glycol and ethanol Salicylates (aspirin) and starvation
What are 4 causes of metabolic alkalosis?
(1) ingestion or admin of alkali
(2) stomach loss of H+
(3) renal loss of H+
(4) diuretic use
What are 4 causes of contraction alkalosis?
(1) loss of large volumes of bicarb free fluid
(2) bicarb [ ] remains constant
(3) admin of IV loop diuretics is the most common cause
(4) NaCl loss in cystic fibrosis
