Acid-Base Balance Flashcards
For the purposes of this class what is the definition of an acid and a strong acid?
Acids can donate a hydrogen ion; strong acids completely or nearly completely dissociate into a hydrogen ion and its conjugate base in aqueous solution
What is a buffer?
A mixture of substances (usually a weak acid and its conjugate base) in aqueous solution, that can resist changes in hydrogen ion concentration when strong acids or bases are added
How is pH calculated?
pH= -log [H+]
What is the pH cutoff value for acidemia? alkalemia?
Acidema= pH 7.45
What is the normal, healthy value of blood pH?
7.4
How are volatile acids eliminated from the body? What are examples of volatile acids?
Eliminated by lungs- include glucose and fat
How are fixed acids eliminated from the body? What are examples of fixed acids?
Eliminated by kidneys- include glucose, cysteine, and phosphoprotein
What is the isohydric principle?
All buffer pairs in a homogenous solution are in equilibrium with the same hydrogen ion concentration
What is the fastest buffer in blood?
Bicarbonate
How does phosphate as a buffer?
It can take up and bind hydrogen
How do bones act as buffers in chronic acidosis?
Ca++ is replaced with H+
What is the effect of increased CO2 on blood pH and bicarbonate concentration?
Increased CO2 will decrease pH and the bicarbonate concentration will increase?
Why does bicarbonate increase with increased CO2 levels in spite of decreasing pH?
Some H+ will be buffered by other non-bicarbonate buffers in the body, which frees up more bicarbonate
How does increased hemoglobin affect bicarbonate levels at different pHs?
There will be increased bicarbonate at lower pHs because more H+ can bind to Hb
What is the respiratory compensation for metabolic acidosis?
Increased H+ conc. stimulates chemoreceptors, which increase alveolar ventilation, decreasing CO2 and increasing pH
What is the renal compensation for acidosis? For alkalosis?
Acidosis= increased fixed acid excretion and decreased bicarbonate excretion; alkalosis= decreased hydrogen ion excretion and increased bicarb excretion
How is the anion gap calculated? What is the normal value?
Anion gap= [Na+]-([Cl-] + [HCO3-]); Normally 12 +/- 4 mEq/L
What conditions could result in metabolic acidosis with an abnormally great anion gap?
Lactic acidosis, ketoacidosis; ingestion of organic acids like salicylate, methanol or ethylene glycol, or renal retention of anions such as sulfate, phosphate, and urate
What are the different classifications of the causes of hypoxia?
Hypoxic hypoxia, V/Q mismatch, anemic hypoxia, hypoperfusion hypoxia, histotoxic hypoxia
What is hypoxic hypoxia?
Conditions in which arterial PO2 is abnormally low
What are some possible causes of hypoxic hypoxia?
Low alveolar PO2, Diffusion impairment, right to left shunts, V/Q mismatch
What causes anemic hypoxia?
A decreased in the amount of functioning hemoglobin
What is histotoxic hypoxia?
Poisoning of the cellular machinery that uses oxygen to produce machinery
