Flashcards in UWorld - Renal & Electrolytes Deck (22)
What uremic toxins are responsible for platelet dysfunction in chronic renal failure?
How do you correct the platelet dysfunction seen in uremia coagulopathy and how do you assess response to the treatment?
DDAVP releases factor VIII:vWF multimers from endothelial storage sites, increasing platelet aggregation and improving bleeding time. Cryoprecipitate and unconjugated estrogens can also be used.
Name 4 causes of hypovolemic hyponatremia
Volume depletion, renal insufficiency, GI loss and renal loss (diuretics). Note that ADH is appropriately increased in these conditions because stimulation due to hypovolemia trumps suppresses due to decreased osmolality. This is why hyponatremia is correct with NS bolus in these conditions.
Name 4 causes of euvolemic hyponatremia
SIADH, psychogenic polydipsia, secondary adrenal insufficiency and hypothyroidism. ADH is inappropriately increased in these conditions.
Name 3 causes of hypervolemic hyponatremia
CHF, cirrhosis and CKD/nephrotic syndrome. ADH is inappropriately increased in these conditions.
What anions present in the serum account for the normal anion gap of 6-12?
Proteins, citrate, phosphate and sulfate
Most common causes of anion gap metabolic acidosis?
#2) Ketoacids (beta-hydroxy butyrate + acetoacetate)
#3) Methanol/Formaldehyde ingestion
#4) Ethylene glycol ingestion
#5) Salicylate poisoning
Remember MUDPILES: methanol, uremia, DKA, paraldehyde, INH or iron, lactic acid, ethylene glycol, salicylates
Common causes of non-gap metabolic acidosis?
Diarrhea, RTA, GI fistula, post-hypoventilation, post-gap acidosis
Why is NS infusion of 200mL/hr to the point of 100-150mL/hr of urine output first line treatment for hypercalcemia? Why is this better than loop diuretics?
Hypercalcemia causes urinary salt wasting leading to hypovolemia. Hypovolemia impairs Ca excretion and exacerbates the pre-existing hypercalcemia. Giving lots of fluids corrects the hypovolemia and allows for Ca excretion. Loop diuretics exacerbate the hypovolemia, so despite "wasting" Ca, they make the situation worse.
How to check for appropriate compensation in a metabolic acidosis? Acute metabolic alkalosis? Acute respiratory acidosis? Acute respiratory alkalosis?
MAc = Winter's formula
MAl = PaCO2 increases by 0.7 for each 1 increase in HCO3
RAc = HCO3 increases by 1 for each 10 increase in PaCO2
RAl = HCO3 decreases by 2 for each 10 decrease in PaCO2
Indications for urgent dialysis
Acidosis: pH 6.5 refractory to treatment or symptomatic
Ingestion: alcohols, salicylate, Li, valproate, carbamazepine
Overload: refractory to diuretics
Uremia w/symptoms (encephalopathy, pericarditis, bleeding)
What conditions can cause asterixis
Hepatic encephalopathy, renal encephalopathy and hypercapnea
Most common cause of nephrotic syndrome in patients with HIV
FSGS. This can occur even when CD4 counts are high and viral load is low.
Common causes of crystal-induced AKI
Acyclovir, sulfonamides, methotrexate, ethylene glycol and protease inhibitors. This usually occurs within 24-48 hours of taking the medication.
Common drugs that cause AIN?
Beta-lactam antibiotics and PPIs. Note that AIN usually takes place 7-10 days after taking the medication.
Reversible causes of urinary incontinence
Pharm: alpha blockers and diuretics
Excessive output: CHF & DM
Restricted mobility: surgery
How does aspirin overdose cause a mixed acid base picture?
Salicylates stimulate the medullary respiratory center and cause a respiratory alkalosis. At the same time it stimulates increased production and decreased elimination of ketoacids and lactic acids, resulting in a metabolic acidosis.
How does glomerular damage progress in a patient with diabetes?
1) Glomerular hyperfiltration
2) Thickening of the basement membrane
3) Mesangial expansion
4) Nodular sclerosis
ACE-I work to prevent renal damage in diabetics by dilating the efferent arteriole and minimizing glomerular hyperfiltration
Next step when the anion gap is markedly elevated and frank uremia is not present?
Calculate the osmolar gap to assess for ethanol, methanol or ethylene glycol intoxication.
1) Calculate serum osmolality = (2Na) + (Glu/18) + (BUN/2.8)
2) Calculate the gap = observed - calculated osmolarity
3) Gap > 10 = ethanol, methanol or ethylene glycol intoxication
A patient presents to the ED in acute heart failure, renal failure and ARDS. There is a gap acidosis and osmolar gap is > 10. Urine shows rectangular, enveloped-shaped crystals. What is causing his symptoms?
Ethylene glycol intoxication. The crystals seen are calcium oxalate crystals that precipitate in patients with ethylene glycol poisoning.
A patient presents to the ED with snowfield vision and acute pancreatitis. There is a gap acidosis and osmolar gap is > 10. What is causing his symptoms?