Acidosis and Alkalosis Case Questions Flashcards
What is the first rule of evaluating acid base?
look at the pH on ABG.
What is the second rule of acid base evaluation?
calculate the anion gap
If the anion gap is elevated, what does that suggest?
most likely a primary metabolic acidosis
can also be a mixed acid base problem that includes an anion gap
What is the thurd rule of acid base evaluation? Aka, what should you check if there is an anion gap?
Calculate the osmol gap
How do you check an osmol gap?
you do measured osmolarity (by lab) - calcualted osmolarity
How do you calculate osmolarity?
2(Na) + Glucose/18 + BUN/2.8
What is a normal osmol gap and what does a high osmol gap suggest?
should be equal to or less than 10
over 10 suggests the person took in a volatile chemical like ethylene glycol or methanol
What is rule 4?
If there’s an anion gap, you need to calular the excess anion gap (also called the delta gap) - this tells you whether the patient is compensating appropriately with bicarb
How co you calcualate a delta gap?
Calculated anion gap minus 12 (the excess gap) added to the measured bicarb should euqal a normal bicarb level (24-26)
If the delta gap is low, what does that suggest? If it’s high, what does that suggest?
low delta gap means there is also a non-anion gap acidosis going on (because the body isn’t compensating appropriately)
high delta gap means there is an underlying metabolic alkalosis as well
What is rule 5 of acid base evaluation?
interpret using the clinical picture!!
What do you have if the ABG is normal but you have an elevated anion gap?
you must have a mixed metabolic alkalosis and anion gap metabolic acidosis
What is the primary disturbance in metabolic acidosis?
overproduction or retention of acid (with subsequent decrease in bicarb)
What is the compensation for a metabolic cacidosis?
hyeprventilation to blow off CO2
What’s an easy rule to see whether someone is compensating apropriately for a metabolic acidosis?
pCO2 should equal the last 2 digits of the pH
What is the differential diagnosis for metabolic acidosis with a high anion gap?
MUDPILES methanol uremia - from kidney failure DKA and AKA Paraldahydre Iron OD or Isoniazid use Lactic acidosis Ethylene glycol (and ethanol) Salicylates
What is a normal anion gap metabolic acidosis caused by?
It’s a loss of bicarb from GI or the kidney with an equal rise of Cl for the loss of bicarb
What are some of the causes of GI/kidney bicarb loss with subsequent normal anion gap metabolic acidosis?
HARDUP Hyperventilation/hyperalimentation Acid ingestion RTA (?) Diarrhea Ureteral and ileal diversion Pancreatic fistulas
What is the primary disturbance in metabolic alkalsois?
increased plasma HCO3 (with subsequent decrease in plasma H) - can happen vice bersa too though
What is the compensation for metaoblic alkalsosis/
hypoventilation - so compensation is limited (you can’t stop breathing)
If a metabolic alkalosis is accompnanied by a urine chloride less than 10, it’s chloride responsibe and will repsond to what treatment?
saline infusion
What are some examples of chloride responsive metabolic alkaloses?
vomiting diuretics NG suction dehydration from diarrhea with Cl wasting villous adenoma
If the metabolic alkalosis if chloride unresponsive, what is the general cause?
high aldosterone, which leads to icnreased H and K excretion in exchange for reabsorbing Na as sodium bicarb
What are the common causes of chloride unresponsive metabolic alkalosis?
Cushings
Hyperaldosterone - including Barter’s
Secondary hyperaldosterone like CHF and CRF
bicarb ingestion
What is the primary disturbance in respiratory acidosis?
hypoventilation leading to an increase in arterial CO2 (with subsequent increase in both bicarb and H+)
How do you compensate for a respiratory acidosis?
kidneys excrete H+ and reabsorb bicarb
FOr a respiratory acidosis, how can you figure out if the compensation is acute or chornic?
For every 10-point rise in pCO2, the bicarb will go up 1 point if acute and up 3 points if chronic
What are the common causes of respiratory acidosis?
airway obstruction
COPD, Aasthma, pneumothroax, infections
CNS depression or respiration - sedatives, hypnotics, drugs, tumors
neuromuscular weakness
What is the primary disturbance in respiratory alkalosis?
hyperventioation blowing off too much CO2, with subsequent decrease in both acid and bicarb
What is the compensation in respiratory alkalosis?
kidney excretion of bicarb and reabsorbtion of acid (beta intercalated cells)
In a respiratory alkalosis, how do you determine if the compensation is acute or chronic?
For every 10 increase of pCO2, bicarb will fall by 2 if acute and by 4 if chronic
What are some common causes of respiratory alkalosis?
anxiety, aspirin, cocaine, progesterone,
any cause of tachypnea = sepsis, fever, PE, pneumonia, hypoxia
alcohol or narcotic withdrawal
