Acid/Base Flashcards
What is the equation of PAO2?
Anticipated Compensation for Acid-Base Disorders
Herderson-Hasselbalch
Used to estimate the pH of a buffer solution
Anion Gap equation
(Na+K+) - (HCO3 + Cl-)
pH normal
7.35 - 7.45
PaCO2 normal range
35-45
HCO2 normal range
20-28
Rule of 4 for pH, PaCO2, HCO3
Averages
pH: 7.4
PaCO2: 40
HCO3: 24
Normal anion gap
12-24meq/L
What does high anion gap indicate?
Cations > anions
If Na and K are normal, likely to indicate other cations are high
- lactic acidosis
- ketoacidosis
- renal failure (uremic - sulphates and phosphates)
- toxin (ethylene glycol, sialcyates - aspirin/sunscreen)
Pneumonic: DUEL
DKA
Uremic
Ethylene glycol
lactic acidosis
Indications for metabolic acidosis with normal anion gap
GI or renal bicarb loss
impaired renal excretion
What are four causes of Metabolic Alkalosis?
Bicarbonate concentration increases
examples:
- GI outflow obstruction
- hypokalemia (K+ shifts out of cells in exchange for H+ ions into the cells increasing blood pH)
- bicarbonate administration
- excessive loss of Chloride (Cl-)
- volume depletion
- loop diuretics and thiazide diuretics
- vomiting (loss of acid in stomach)
- Excessive NGT suctioning (removing the stomach acid)
What are four methods of developing metabolic acidosis?
- Loss of bicarbonate (e.g. small bowel diarrhea)
- Inability to excrete H+ (e.g. chronic renal failure)
- Increase acid production (e.g. increased cellular metabolism causing an increase in formation of biproducts (lactate, CO2, H+), DKA - build up of ketone bodies –> Kussamaul breathing - large quick breaths to get rid of CO2)
- Addition of exogenous acids to the body.
What are clinical signs of hypernatremia
nonspecific central nervous system signs
* lethargy
* weakness
* behavioral or postural changes
* ataxia
* seizures
* altered level of consciousness
* coma
* death
clinical signs not observed until sodium concentrations > 170mEq/L
What are idiogenic osmoles? When and why are they produced?
The body makes intracellular osmolytes when hypernatremia persists for more than a few hours to help restore the osmolality of the intracellular space. Full compensation occurs in roughly 24 hours.
Explain why rapid sodium correction is detrimental?
Because the idiogenic osmoles allowed for intracellular fluid and extracellular fluid to be in equilibrium. Rapid fluid administration will reduce extracellular osmolality. The intracellular fluid is hyperosmolar compared to the extracellular fluid, so water will travel back into cells resulting in cellular swelling, cerebral edema and life-threatening neurological dysfunction.