Renal & Electrolytes Flashcards
CKD, AKI, Hyponatremia
How is CKD evaluated?
↓ GFR (< 60 mL/min for > 3 months)
UA: ↑ BUN/Cr, ↑ potassium, proteinuria.
What is the treatment for CKD?
ACE inhibitors/ARBs (↓ intraglomerular pressure)
(decrease protein intake, EPO if anemic)
What are complications of CKD?
Cardiovascular disease
mineral bone disorder
acidosis
uremia
What are the 3 main types of hyponatremia?
- Hypovolemic
- Euvolemic (SIADH)
- Hypervolemic (CHF, cirrhosis)
How is hyponatremia treated?
Slow correction; Hypertonic saline in severe cases to avoid central pontine myelinolysis.
Severe hyponatremia can lead to…
confusion, then seizures, AMS or cerebral edema
What is the mnemonic for metabolic acidosis causes?
MUDPILES
Methanol
Uremia
DKA
Paraldehyde (historical Rx used for alcohol w/d)
Isoniazid
Lactic acidosis
Ethanol/Ethylene glycol
Salicylates
How is anion gap calculated?
Anion gap = Na⁺ - (Cl⁻ + HCO₃⁻).
What is the most common cause of CKD?
Diabetes mellitus → followed by hypertension.
AKI will show an:
↑ Serum Cr by ≥ … in 48 hours
↑ Serum Cr by ≥ …% from baseline in 7 days
↓ Urine output < … for ≥6 hours
- 0.3 mg/dL
- 50%
- 0.5 mL/kg/hr
A patient with new azotemia (↑ BUN/Cr), oliguria, or sudden electrolyte changes → dx?
AKI
What are the three types of AKI?
(hint: similar to hepatic disease)
- Pre-renal (↓ Perfusion)
- Intrinsic (Direct damage)
- Post-renal (Obstruction)
what are the main differences in the presentation of pre-renal AKI and intrinsic AKI?
- Pre-renal: urea is high (BUN:Cr >20:1), sodium retained, rapid improvement with fluids
- Intrinsic: sodium low, no improvement with fluids
(post-renal/obstruction is improved w/catheter)
MCC of pre-renal AKI?
(3 categories: hypovolemia, circulation, drugs)
- hypovolemia: n/v/d, hemorrhage, dehydration
- low cirulation: CHF, cirrhosis, sepsis
- drugs: NSAIDs (afferent arteriole vasoconstriction, ACE-i’s (efferent arteriole dilation)
MCC of intrinsic AKI?
Acute Tubular Necrosis (ATN): muddy brown casts, FENa > 2%. (from prolonged ischemia, sepsis, shock or toxins (rhabdo, cisplatin, amphotericin B)
(acute interstitial nephritis/AIN from Rx and Glomerulonephritis are the other two causes)
When does a patient need to start dialysis?
(hint: only one of the following: AEIOU)
- Acidosis (pH < 7.1)
- Electrolytes (K+ >6.5), refractory to tx
- Ingestion (toxic alcohol, salicylates, lithium)
- Overload: pulmonary edema, refractory to diuretics
- Uremia: encephalopathy, pericarditis, pleeding diathese
For respiratory acid-base disorders, CO2 & HCO3 are in the (same/opposite) direction?
For metabolic acid?
- Respiratory: CO2 & HCO3 opposite
- Metabolic: CO2 & HCO3 same
By using Winter’s Formula, we can find out if…
compensation is appropriate; pCO2 should match expected compensation
In metabolic alkalosis, check urine… to determine treatment
Cl-
(if it is high, give NaCl and K, if low Aldo blockr or surgery)
3 causes of Cl- responsive metabolic alkalosis
- Vomiting
- NG suction
- Diuretics
(If urine Cl⁻ <10 → Saline-Responsive → Treat with fluids. If urine Cl⁻ >10 → Look for hyperaldosteronism.)
3 causes of Cl-resistant metabolic alkalosis
hyperaldo
cushing’s
bartter/
(If urine Cl⁻ <10 → Saline-Responsive → Treat with fluids. If urine Cl⁻ >10 → Look for hyperaldosteronism.)
Biggest danger of correcting hyponatremia too fast =
Osmotic Demyelination Syndrome (formerly CPM)
If hyponatremia + high glucose (e.g., DKA) → its not true hyponatremia, it is a …
dilutional effect
(plasma osmolality will be high (over 295); causes are DKA/glucose, mannitol or contrast)
True hypotonic hyponatremia has a plasma osmolality of less than…
275
3 key sx of hypovolemic hyponatremia?
- dry mucous membranes
- orthostasis
- low BP
(causes: dehydration or diuretics) n/v/d, adrenal insufficiency)
4 causes of euvolemic hyponatremia
- SIADH
- psychogenic polydipsia
- hypothyroidism
- adrenal insufficiency (also causes hypovolemic hyponatremia)
