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GU 7 Electrolyte Dis
Electrolyte Disturbances
| Question | Answer |
|---|---|
| What is the tx for febrile seizures? | Lower temp (acetaminophen or ibuprofen), reassurrance. |
| A pt is found to have a honeycomb pattern on CT scan of the chest. What is the dx and tx? | DIffuse interstitial pulmonary fibrosis. Tx: steroids, AZT or cyclophosphamide, and N-acetylcysteine |
| A 45yo obese woman with pruritis, clay-colored stools, and dark urine has an elevated alk phos and elev bilirubin. What is the most likely cause? | Biliary tract obstruction (possibly gall stones) |
| What is the definition of hypernatremia (give specific #)? What is it usually caused by? | serum Na >155mEq/L. Usually caused by volume contraction like dehydration, insensible losses, vomiting or dirreah, DI, or increased aldosterone. Giving too much hypertonic saline is another cause. |
| At pt presents complaining of uncontrollable thirst. Labs show serum Na of 160. What should you work this pt up for? | Diabetes insipidus |
| What should a normal 24h urine osmolality be? | 500-800 mOsm/kg of water |
| Pt with oliguria (<500ml/d) has a low urine osmolality (<400/d) with signs of fluid overload. What should you work this pt up for? | Excess aldosterone |
| Pt with oliguria (<500ml/d) has a normal urine osmolality (>400/d). What might be the cause? | Low fluid intake or excess losses |
| What kind of saline should be given to treat hypernatremia? What is the max amt of correction per day and what can happen if this is exceeded? | Give hypotonic saline. Max reduction of Na is 12mEq/d. Exceeding this can cause cerebral edema |
| What is the difference between central and nephrogenic diabetes insipidus (DI)? | Central is caused by failure of posterior pituitary to secrete ADH. Nephrogenic is caused by insensitivity of the kidneys to ADH. |
| Name 5 major causes of central DI. | Idiopathic, cerebral trauma, pituitary tumor, hypoxic encephalopathy, or anorexia nervosa. |
| Name 4 causes of nephrogenic DI. | Hereditary renal dz, lithium toxicity, hypercalcemia, or hypokalemia. |
| How can the water deprivation test be used to distinguish central from nephrogenic DI? | Withhold water for 2-3h. Give ADH. Nephrogenic will show no change because the kidneys can't respond to it. Central will have increased urine osmolality b/c the body will concentrate the urine in an attempt to hold onto water. |
| Tx for central DI? | ADH analog like desmopressin (DDAVP) |
| Tx for nephrogenic DI? | salt restriction, increased water intake, HTZ (first line), tx underlying condition |
| What is the tx for nephrogenic DI caused by lithium toxicity? | HTZ + amiloride |
| What is the definition of hyponatremia (give specific values)? What is the max correction per day? What complication can arise if this is exceeded? | Na <135mEq/L. Max correction is 12mEq/d. Central pontine myelinolysis in the case of rapid overcorrection with hypertonic saline. |
| When should saline be given to a pt with hyponatremia? | If they are hypovolemic and have serum osmolality <280mOsm/kg (normal is 280-295). |
| How should a pt with Na <120mEq/L be treated? | Loop diuretics or hypertonic saline. This is severe hyponatremia! |
| Interpret these findings: Pt with hyponatremia and normal serum osmolarity. What might you expect to find on labs? Likely dx? | Hyperlipidemia on labs. Dx: Pseudohyponatremia. Happens b/c serum vol gets expanded by lipids so the amt of sodium per volume of serum decr even though the amt of sodium per unit of water in the serum is appropriate. Multiple myeloma can cause this. |
| Interpret these findings: pt with high serum osmolality (>295) and high glucose. Dx and pathogenesis? | Osmotic hypovolemia. Elevated glucose causes hyperosmolality. Increased osmolarity pulls water out of cell thereby diluting serum sodium. |
| How do you calculate the correct serum [Na] that will result from correction of hyperglycemia? | Add 1.6 mEq of Na for every 100mg/dL of glucose over 100. (e.g., if glucose is 300, add 3.2 to serum [Na]) |
| Interpret these findings: pt with hyponatremia presents with high serum osmolarity (>295) and normal glucose. Dx? | Hypertonic intake (maybe mannitol) |
| What could cause a low FeNa (<1%) in terms of physiology? | the physiologic response to a decrease in renal perfusion is an increase in sodium reabsorption to control hypovolemia |
| What could cause a high FeNa (>1%) in terms of physiology? | either excess sodium is lost due to tubular damage, or the damaged glomeruli result in hypervolemia resulting in the normal response of sodium wasting |
| Interpret these findings: a pt with hyponatremia, low serum osmolality (<280), and a high FeNa (>1%) with a fluid overload state. | Renal failure. Sodium is getting dumped into urine, but body is still fluid overloaded b/c kidneys are unable to keep up and get all that fluid out. |
| Interpret these findings: pt with hyponatremia, low serum osmolarity, and high FeNa >1% with euvolemic state | SIADH or hypothyroidism. For SIADH, picture body dumping sodium to try and get rid of all that water, yet somehow the fluid state stays normal b/c ADH is fighting against this mechanism and causing you to retain water. Think of this as bipolar kidneys! |
| Interpret these findings: pt with hyponatremia, low serum osmolarity, and high FeNa >1% with hypovolemic state | Diuretics and ACE-i. Drugs are causing the body to dump too much water. Normally kidneys should hold onto sodium if you're dehyrated to keep water in, but the drugs override the kidneys. |
| Interpret these findings: pt with hyponatremia, low serum osmolarity, and low FeNa (<1%) with fluid overload state | Cirrhosis, nephrotic syndrome, CHF (body prob holding onto sodium in an attempt to keep volume up b/c due to loss of proteins, the kidneys think they're being underperfused) |
| Interpret these findings: pt with hyponatremia, low serum osmolarity, and low FeNa (<1%) with euvolemic state | Polydipsia |
| Interpret these findings: pt with hyponatremia, low serum osmolarity, and low FeNa (<1%) with dehydration | Vomiting, diarrhea. Even though your body is holding onto sodium to try and increase volume, you're dehydrated b/c you're losing your volume from someplace else (gut to butt) |
| What kind of electrolyte abnormality and volume status is seen with SIADH? | Euvolemic hyponatremia |
| Causes of SIADH? | Paraneoplastic syndromes, CNS pathology, sarcoidosis, major surgery, pneumonia, HIV |
| Tx for SIADH? | Fluid restriction. Loop diuretics and hypertonic saline if symptomatic. Last resort is demeclocycline |
| Define hyperkalemia. | Serum K>5mEq/L |
| EKG finding in hyperkalemia? | Tall, peaked T waves |
| Tx for hyperkalemia? | Calcium gluconate to prevent arrhythmias by stabilizing the myocardium. Other tx involve lowering the serum K levels. |
| What medications can be used to rapidly correct hyperkalmeia by shifting potassium into cells? | Insulin (+glucose to prevent hypoglycemia), sodium bicarb, albuterol nebs |
| Define hypokalemia. | Serum K <3.5mEq/L |
| Which diuretics are K wasting? | Loops and thiazides. |
| EKG finding with hypokalemia? | Flattened T waves. Also ST depression and U waves. |
| Low potassium and HTN? W/u for _____. | hyperaldosteronism |
| Low potassium, no HTN, and metabolic acidosis. Dx? | Renal tubular acidosis |
| Define hypercalcemia | Serum Ca >10.5 |
| S/s of hypercalcemia. | Bones (fractures), stones (nephrolithiasis), groans (GI sx like constipation), and psychiatric overtones (mental status changes) |
| Back pain, anemia, renal dysfunction, elevated ESR, and constipation. Dx? | Multiple myeloma. Constipation is 2/2 hypercalcemia caused by bone lysis. |
| EKG finding on hypercalcemia? | SHortened QT interval |
| EKG finding on hypocalcemia? | Lengthened QT interval |
| Name 2 signs seen in hypocalcemia and describe them. | Chvostek's sign: tapping the facial n causes a spasm. Trousseau's sign: inflating BP cuff causes carpal spasm |
| How does hypoalbuminemia affect Ca levels? | As albumin decreases, the true value of calcium increases 0.8mg/dL for each 1g/dL of albumin <4. |
| What volume status would you expect in a pt with hyponatremia due to thiazide diuretics? | Hypo or euvolemia |
| What volume status would you expect in a pt with hyponatremia due to SIADH? | Euvolemia |
| What volume status would you expect in a pt with hyponatremia due to cirrhosis? | Hypervolemia |
| What volume status would you expect in a pt with hyponatremia due to Addison's dz? | Hypovolemia |
| What volume status would you expect in a pt with hyponatremia due to hypothyroidism? | Euvolemia |
| What volume status would you expect in a pt with hyponatremia due to renal failure? | Hypervolemia |
| What volume status would you expect in a pt with hyponatremia due to psychogenic polydipsia? | Euvolemia |
| Name 4 medication classes that cause hyperkalemia. | Spironolactone, digoxin, ACE-i/ARB, and beta blockers |
| Name 5 medication classes that cause hypokalemia. | Loop diuretics, HTZ, albuterol, insulin, carbonic anhydrase inhibitors (acetazolamide) |
Created by:
sarah3148
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