Electrolytes Lecture 2 Flashcards
What ion does chloride normally change with?
Typically changes with Na+ (but is able to change independently of Na+)
A change in [Cl-] will be met by an equal and opposite change in _______
[HCO3-]
What are the two main ways that hypochloraemia arises (= increase in [HCO3-])
- Cl- is sequestered/lost 2. Cl- is diluted
What are the three main ways that hyperchloraemia arises?
- Excessive Cl- is resorbed 2. Excessive Cl- “intake” 3. Cl- mistake
What is the formula for corrected chloride?
Corrects for changes in water
What is an acid?
Proton donor (HA)
What is a base?
Base = proton acceptor (A-)
What is the pKa?
pH where 50% of an acid is dissociated in an aqueous solution - depicts strength of the acid - lower pKa = a stronger acid
What is a volatile acid?
CO2 (can form H2CO3)
What are non-volatile acids?
Noncarbonic acids = all acids other than H2CO3
What is a buffer?
Weak acid - pKa within 1 unit of blood pH - scavenge H+ or OH- (tight regulation is essential)
What are the main buffers in the body?
The main buffer = carbonic acid
Others: Hemoglobin, Albumin, Phosphate, Bone
What are the three steps that are involved in assesing the acid base status?
- Asses the pH
- Asses respiratory contribution (pCO2)
- Assess the metabolic contribution (pHCO3-)
How does hypoventilation affect acid-base balance?
Hypoventilation results in acidosis
How does hyperventilation affect the acid base status?
Hyperventilation = alkalosis
What is base excess and how can it be interpreted?
Base Excess:
mmol/L of strong acid or base required to return plasma to normal pH
Negative BE - metabolic BE - metabolic acidosis
Postive BE - metabolic alkalosis
What are the causes of metabolic acidosis?
- Bicarbonate buffers an acids - high anion gap caused by unmeasured anions - L.U.K.E - Lactic acid, Uremic acids, Ketoacids, Ethylene glycol metabolites
- Bicarbonate is lost from the body - diarrhea, renal tubular acidosis
- Bicarbonate dilutes by Cl- containing solution
- Compensation for primary respiratory acidosis
What are the causes of metabolic alkalosis?
- Gastric acid loss/sequestration
- Loop diuretics
- Bicarb administration
- Compensation for primary respiratory acidosis
What are the cause of respiratory acidosis?
- Hypoventilation
- Rebreathing
- Compensation from primary metabolic alkalosis
What are the causes of respiratory alkalosis?
- Excitement
- Excercise
- Pain
- Pulmonary parenchymal disease
- Fever, SIRS/species
- Hypotension
- Compensation for primary metabolic acidosis
