Regulation
Identify the most important buffer system in the body and write the equation on the board.
Bicarbonate/CO2 buffer system.
CO2+H20–>H2CO3–>HCO3+H+
Write Winter’s Formula on the board.
pCO2=(1.5xHCO3)+8 (+/-2)
First step in determining an acid-base disorder.
Look at the pH
List 1 cause of non anion gap metabolic acidosis.
FUSEDCARS
Fistula, ureterogastric conduit, saline administration, endocrine (Addison’s Disease), diarrhea, carbonic anhydrase inhibitors, ammonium chloride, renal tubular acidosis, spironolactone
Write out the Henderson-Hasselbach Equation on the board (Bicarbonate and pCO2 version).
PH= 6.1+log([HCO3]/(.03xpCO2))
Timeline of compensation and how it occurs in metabolic disorders vs. respiratory disorders.
Metabolic disorders have rapid compensation w/in minutes by changes in ventilation.
Respiratory disorders have slower compensation that can take hours to days based on renal excretion.
Metabolic disorders have pH and pCO2 changes in____direction, while respiratory disorders have pH and pCO2 changes in____ direction.
Same, opposite
SMORE
List 4 signs/symptoms of aspirin toxicity.
Tachypnea, tinnitus, nausea, vomiting, altered mental status, fever, abdominal pain,
List other buffer systems the body utilizes to maintain acid-base balance.
Phosphate, ammonia, proteins intracellularly like hemoglobin
Describe acute vs. chronic compensation in respiratory acid-base disorders.
Acute: buffers found in blood
Chronic: Changes in reabsorption of HCO3 and excretion of H+ w/ urinary buffers based on if alkalosis or acidosis.
Winter’s formula can help identify secondary ____ disorders, while delta ratios can identify secondary ____ disorders.
Respiratory, metabolic
Winter’s Formula will ______ pCO2 values in an aspirin overdose.
Overestimate
Hemoglobin is an _____ buffer and can bind H+ ions in ____.
Intracellular, capillaries of tissues.
Expected change in bicarbonate in acute respiratory disorders.
Bicarbonate increases by 1 unit above 24 mEq/L for every 10 units of increase in pCO2 above 40mmHg if acidosis, decreases by 2 units per every 10 if alkalosis
1,2,3 rule
Explain the difference between a normal anion gap metabolic acidosis and an anion gap metabolic acidosis.
Normal is due to loss of bicarbonate with an increase in chloride to maintain anion gap. High anion gap is due to increased concentration of organic acids w/ no compensatory increase of chloride.
Explain the pathophysiology of the acid-base disorders caused by aspirin toxicity.
Stimulation of medullary receptors leads to hyperventilation and respiratory alkalosis. Uncoupling of oxidative phosphorylation leads to metabolic acidosis.
Describe the major sites of acid-base balance in the kidney and be able to explain their mechanism.
Look at our Nephron Project.
Expected change in bicarbonate levels in chronic respiratory disorders.
Bicarbonate will increase by 4 units from 24 mEq/L for every 10 units of increase in pCO2 above 40mmHg if acidosis, decrease by 5 units for every 10 if alkalosis
3,4,5 rule
When should you calculate the anion gap? Write the equation on the board, along with the delta ratio. What is the normal ratio?
Metabolic acidosis.
Na-(Cl+HCO3)
Change in anion gap is AG-12, Change in bicarbonate is 24-[HCO3]. Delta ratio is change in AG over change in bicarbonate. 1-2 is normal.
Fill out the acronym MUDPILES on the board and indicate whether these are causes of normal or high anion gap acidosis
Methanol, Uremia, Diabetic Ketoacidosis, Propylene glycol, Iron or INH, Lactic Acidosis, Ethylene glycol, and Salicylates. Cause high anion gap acidosis