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Flashcards in UWorld - Renal & Electrolytes Deck (22)
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What uremic toxins are responsible for platelet dysfunction in chronic renal failure?

Guanidinosuccinic acid


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?

#1) Lactate
#2) Ketoacids (beta-hydroxy butyrate + acetoacetate)
#3) Methanol/Formaldehyde ingestion
#4) Ethylene glycol ingestion
#5) Salicylate poisoning
#6) Uremia

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

Infection: UTI
Atrophic vaginitis/urethritis
Pharm: alpha blockers and diuretics
Psych: depression
Excessive output: CHF & DM
Restricted mobility: surgery
Stool impaction


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?

Methanol poisoning.


Dietary habits that can lead to nephrolithiasis

High protein
High vitamin C intake
High sodium intake
Low calcium (paradoxical effect)
Low fluid intake