MTB 3 Flashcards
Causes of Hyponatremia
HYPERvolemia
HYPOvolemia
Addison Dz
Euvolemia
Pathophys of Hypervolemia Hyponatremia
Examples
Intravascular volume depletion leads to increased ADH. Pressure receptors in atria and carotids sense decrease in volume, stimulate ADH
- CHF
- Cirrhosis
- Nephrotic Sydnrome
Pathophys of Hypovolemia Hyponatremia
Examples
Sweating, burns, fever, pneumonia, diarrhea, diuretics
- When chronic replacement with water
Pathophys of Euvolemia Hyponatremia
Examples
Pseudohyponatremia Psychogenic Polydipsia Hypothyroidism SIADH Hypothyroidism
Hyperglycemia pathophys in Hyponatremia
Very high glucose levels lead to decrease in sodium levels.
Every 100mg/dL of glucose above normal, there is 1.6 mEq/L decrease in sodium
Psychogenic Polydipsia Pathophys
Massive water ingestion above 12 to 24 liters/day
Hx of Bipolar
SIADH pathophys
Examples
Lung or Brain Dz
Drugs: SSRIs, sulfonylureas, vincristine, cyclophosphamide, TCAs
Presentation of Hyponatremia
Confusion Lethargy Disorientation Seizures Coma
What is Urine osmolality in SIADH
High - inappropriately concentrated urine
Uric Acid - Low
BUN - Low
Most accurate test in SIADH
High ADH level
TX for SIADH
Severe, symptomatic
- ADH Antagonists: Tolvapatan, Conivaptan
Chronic
- Demeclocycline blocks ADH at collecting duct
Correction of low sodium too rapidly?
Central Pontine Myelinolysis
Osmotic demyelinization
How fast do we correct low sodium
0.5-1 mEq per hour OR
12 to 24 mEq per day
Causes of pseudohyperkalemia
Hemolysis
Repeated fist clenching
Thrombocytosis or leukocytosis
Drugs that cause hyperkalemia
Non-selective beta blockers ACE, ARBs Spironolactone Digitalis Cyclosporine Heparin NSAIDs Succinylcholine Trimethoprim (esp HIV)
Hyperkalemia - causes of decreased excretion
Renal Failure Aldosterone decreases - ACE/ARBs - Type IV renal tubular acidosis - Spironolactone/Eplerenone - Triameterene and amiloride - Addison Dz
Hyperkalemia from increased release by tissues
Tissue destruction
-Rhabdomyolysis
- Tumor lysis syndrome
Decreased insulin
Acidosis - cells pick up hydrogen and release potassium in exchange
Beta blockers/Digoxin - inhibit Na/K ATPase
Heparin
Role of insulin and potassium
Inusulin drives potassium INTO cells
K+ is intra or extracellular
95% Intracellular
Presentation of hyperkalemia
Muscle contraction and cardiac conduction Weakness Paralysis Ileus Cardiac rhythm disorders
Most urgent test in severe hyperkalemia
EKG
EKG findings in hyperkalemia
Peaked T waves
Wide QRS
PR interval prolongation
TX for Hyperkalemia w abnormal EKG
- Calcium chloride or calcium gluconate
- Insulin and glucose drive K+ back into cells
- Bicarbonate - drives K+ into cells
- used most when acidosis causes hyperkalemia
TX for removing K+ from the body
- Kayexalate - sodium polystyrene sulfonate - removes thru bowel over several hours by binding K+ in gut
How to lower K+ Levels
- Insulin and Bicarb redistribute into cells
- Inhaled beta agonist - albuterol
- Dialysis
When is calcium used in hyperkalemia
Only when EKG is abnormal to protect the heart
Causes of hypokalemia
Shifting into cells
Decreasing intake
Renal loss
GI Loss
Renal loss of K+ hypokalemia Causes
Loops Increased aldosterone Primary hyperaldosteronism = Conn's Cushing syndrome Bartter syndrome = Salt loss at LOH Licorice Volume depletion Hypomagnesemia RTA = types I and II
Presentation of hypokalemia
Muscular contraction and cardiac conduction
Weakness
Paralysis
Loss of reflexes
EKG of Hypokalemia
U waves
PVCs (ventricular ectopy), flattened T waves, ST depression
TX for Hypokalemia
Oral K+ replacement
AE of IV K+ replacement
Fatal arrhythmia if done too fast
How long do bicarb and insulin take to work in hypokalemia
15 - 20 mins
RTA = what kind of acidosis
Metabolic Acidosis with normal AG
How to calculate Anion Gap
Normal range
Na - (Cl + HCO3)
6-12
Two most important causes of Metabolic Acidosis with normal AG
Why normal AG
- RTA
- Diarrhea
BC both are hyperchloremic = Cl rises
Type I RTA
Pathophys
Causes
Distal tubule damage where HCO3 cannot be generated, so acid cannot be excreted into tubule which raises pH of urine
Nephrocalcinosis = Calcifies renal parenchyma
Drugs - Ampho B
AI - SLE, Sjogren
What is role of Distal tubule
Generates new bicarb under Aldosterone influence
What kind of urine (acidic/alkaline) do we see increased formation of kidney stones
Alkaline - from calcium oxalate
Best initial test for RTA type I
UA - abnormally high pH > 5.5
Most accurate test for RTA type I
Infuse acid into blood w ammonium chloride
TX for RTA type I
Replace bicarbonate that will be absorbed at proximal tubule
RTA Type II
Location
Causes
Proximal
-90% of filtered HCO3 reabsorbed at proximal tubule
Damage causes decreased ability to reabsorb HCO3, and is lost in urine
What damages proximal tubule
Damage by
- Amyloidosis
- Myeloma
- Fanconi syndrome
- Acetozolamide
- Heavy metals
What effect does chronic metabolic acidosis have on calcium
Leaches calcium out of bones - softens them
Osteomalacia
Most accurate test for Type II RTA
Evaluate HCO3 malabsorption in kidney
- give HCO3 and test urine pH
- urine pH rises b/c kidney can’t absorb
K+ in Type I RTA
Hypokalemic
K+ in Type II RTA
Hypokalemic
TX for Type II RTA
Volume depletion enhances HCO3 reabsorption
- Thiazides
Type IV RTA
pathophys
MC in which population
Hyporeninemia, Hypoaldosteronism Decreased amt or effect of aldosterone at kidney tubule - Na Loss - K+ and H+ retention MC in Diabetes
Testing for Type IV RTA
Persistently high urine Na despite Na-depleted diet
Hyperkalemia
Which RTA do we see nephrolithiasis
Type I - Distal
RTA with Variable urine pH
Type II - Proximal
RTA with high urine pH
Type I - Distal
TX for Type IV RTA
Fludrocortisone
- highest aldosteronelike effect
RTA with Hyperkalemia
Type IV
