Acid-Base Disorders Flashcards
what is the range of normal arterial pH?
7.35-7.45
what is the range for normal intracellular pH?
7.0-7.3
what is the effect of HCO3 on pH?
it increases pH
what is the effect of pCO2 on pH?
it causes a decrease in pH
how is metabolic acidosis defined?
low serum levels of HCO3-
how is metabolic alkalosis defined?
increased levels of HCO3-
how is respiratory acidosis defined?
increased levels of pCO2
how is respiratory alkalosis defined?
low pCO2
what are the different kinds of metabolic acidosis?
High anion gap metabolic acidosis and normal anion gap acidosis (aka hyperchloremic acidosis)
how many acid-base disturbances can be present at the same time?
three is the most possible since it is not possible to breathe fast and slow at the same time
what are the standardized steps to approaching a patient with symptoms suggesting an acid-base disturbance?
1) determine if acidosis or alkalosis is present 2) determine if the primary disturbance is metabolic or respiratory 3) if metabolic acidosis is present, calculate the anion gap 4) calculate appropriate compensation for primary acid-base disorder
what is the value that defines acidosis?
anything less than 7.35
what is the value that defines alkalosis?
anything greater than 7.45
what is the normal range for pCO2?
35-45
what is the normal range for HCO3-?
22-26
what is the normal range for anion gap?
10 (+/- 5 or 6 ie 5-16)
what is the normal range for osmolality gap?
10-15
how do you calculate anion gap?
Na - (HCO3- + Cl-)
why is an anion gap clinically used?
to differentiate the etiologies of metabolic acidosis (HAGMA or NAGMA), to diagnose paraproteinemias (low anion gap levels), to diagnose lithium, bromide, or iodide intoxications (low or negative anion gap levels)
if you discover HAGMA in a patient, what should you do next?
calculate the osmolarity gap
how do you calculate the osmolarity gap?
osmolarity gap= measured osmolality- calculate osmolality
how do you find the calculated serum osmolality?
2(Na) + (glucose/18) + (BUN/2.8)
what is a normal osmolality gap?
anything 10 or less
what does it mean if a patient has an osmolality gap greater than 10?
it is suggestive of additional solutes in the blood–> there are foreign invaders!!
what is the osmolality gap clinically useful for?
screening for alcohol ingestions, screening for ketoacidosis, screening for lactic acidosis
when do you find the delta-delta gap?
used in patients with HAGMA to determine if there is a coexistent NAGMA or metabolic alkalosis also present
how do you calculate the delta gap?
calculate anion gap- the normal anion gap; then you have to find the delta HCO3-: normal HCO3- - delta gap
what does it mean if the delta HCO3- is around 16?
then there is no additional acid-base disorder present
what does it mean if the delta HCO3- is greater than 16?
then there is a metabolic alkalosis also present in addition to the HAGMA
what does it mean if the delta HCO3- is less than 16?
then a non-gap metabolic acidosis (NAGMA) is present in addition to the HAGMA
what are the two mnemonics for the causes of metabolic acidosis?
MUDPILES and GOLDMARK
what does MUDPILES stand for?
Methanol Uremia Diabetic ketoacidosis Propylene glycols Iron or isoniazid Lactic acidosis Ethanol/ ethylene glycol Salicylates
What does GOLDMARK stand for?
Glycols Oxoproline L-lactic acidosis D-lactic acidosis Methanol Aspirin Renal failure Ketoacidosis (alcoholic, diabetic, starvation)
What is the mnemonic for causes of increased osmolarity gaps?
ME DIE
what are the causes of increased osmolarity gaps? (ME DIE)
Methanol Ethanol Diethylene glycol Isopropyl alcohol (rubbing alcohol) Ethylene glycol
what is the enzyme needed for alcohol metabolism?
Alcohol dehydrogenase (ADH)
what is the mnemonic for NAGMA?
DURHAAM
what are the causes of NAGMA (DURHAAM)?
Diarrhea Ureteral diversion or fistula Renal tubular acidosis Hyperalimentation Acetazolamide Addison's disease Miscellaneous
what are the miscellaneous causes of NAGMA?
toluene toxicity (glue sniffing), pancreatic fistula, medications
what are the various renal tubular defects that can be present that lead to RTA?
impaired H+ ion secretion or impaired HCO3- reabsorption
What are the different types of renal tubular acidosis and where do they occur?
RTA 1: distal RTA
RTA 2: proximal RTA
RTA 4: collecting duct
What is occurring in RTA 1?
there is decreased net H+ ion secretion in distal tubules and collecting duct
what is occurring in RTA type 2?
there is decreased HCO3- reabsorption in the proximal tubule
What is occurring in RTA type 4 (aka hyperkalemic RTA)?
there is decreased aldosterone secretion or aldosterone resistant leading to decreased net H+ and K+ secretion in the collecting duct
What is the urine anion gap used for?
it is clinically used to differentiate renal from non-renal causes of NAGMA
what is the urine anion gap (UAG)?
it is a marker of NH4Cl (ammonium chloride) excretion, which indicates proper urine acidification
what happens to the urinary ammonium chloride excretion in cases of metabolic acidosis?
it should increase
how do you calculate UAG?
(Urine Na+ Urine K) - Urine Cl
what does it mean if the UAG is negative?
it indicates appropriate distal nephron urinary acidification
what does it mean if the UAG is positive?
it indicates inappropriate distal nephron urinary acidification
what is urine chloride used as?
a surrogate marker of ammonium excretion
What are the 3 broad causes of respiratory acidosis?
anything that lowers respiratory rate/tidal volume, increases dead space, or worsens airway obstruction; inadequate ventilator settings; increases in CO2 production
what could cause an increase in CO2 production?
increased carbohydrate diet, hyperthermia, and seizures
What are some examples of things that lead to an increased respiratory rate, therefore leading to respiratory alkalosis?
pna, PE, pulmonary edema, pneumothorax, pregnancy, sepsis, anxiety
what is the relationship between acidosis/alkalosis and serum potassium?
acidosis is associated with hyperkalemia and alkalosis is associated with hypokalemia
