Electrolytes Flashcards
Sx of hyponatremia
Nausea and malaise, stupor, coma
Sx of hypernatremia
Irritability, stupor, coma
Sx of hypermagnesia
Decreased DTRs, lethargy, bradycardia, hypotension, cardiac arrest, hypocalcemia
Sx of hypomagnesia
Tetany, arrhythmias, hypokalemia
Sx of hyperphosphatemia
Renal stones, metastatic calcifications, hypocalcemia
Sx of hypophosphatemia
Bone loss, osteomalacia
What are the systems most affected by hypercalcemia?
CV:
- Short QT syndrome
- Hypertension
Renal:
- Nephrolithiasis
- Diabetes insipidus
- Renal insufficiency
Bone:
- Osteoporosis
What is the MCC of hypercalcemia? What causes that disorder?
Primary hyperparathyroidism is the MCC of hypercalcemia. It is caused by:
- Solitary adenoma (80-85%)
- Hyperplasia of all 4 glands (15-20%)
- Parathyroid malignancy (1%)
What are the causes of hypercalcemia?
Primary hyperPTH and cancer account for 90% of hyperCa cases. Other causes are:
- Vit D intoxication
- Sarcoidosis and other granulomatous diseases
- Thiazide diuretics
- Hyperthyroidism
- Multiple myeloma and metastases to bone
What is the Rx for hypercalcemia?
1) Saline hydration at high volume
2) Bisphosphonates: pamidronate, zoledronate
Two electrolyte imbalances that cause hypocalcemia
Hypermagnesia, hyperphosphatemia
Sx of hypercalcemia
Acute, symptomatic hypercalcemia presents with confusion, stupor, lethargy, and constipation.
Renal stones, bone pain, abdominal pain*, psychiatric overtones (anxiety, altered mental status); there is not necessarily calciuria
*“stones, bones and belly groans”
What are the Sx of hyperkalemia?
Potassium disorders interfere with muscle contraction and cardiac conduction. Look for:
- Muscle weakness; paralysis when severe
- Ileus (paralyzes gut muscles)
- Arrhythmias
Sx of hypocalcemia
Signs of neuronal hyperexcitability in hypoCa:
- Tetany (Trousseau sign)
- Facial nerve hyperexcitability (Chvostek sign)
- Seizures
- Carpopedal spasm
- Perioral numbness
- Mental irritability
What are the causes of hypocalcemia?
- Primary hypoPTH: most often a comp. of prior neck surgery e.g. thyroidectomy.
- Hypomagnesemia: Mg is necessary for PTH to be released from the gland. Low Mg levels –> increased urinary Ca loss
- Renal failure: the kidney converts Vit D to its active form
Less common causes:
- Vit D deficiency
- Fat malabsorption
- Genetic disorders
- Low albumin states
How does albumin affect Ca levels?
Low albumin causes a decrease in total serum calcium, but the free calcium is normal, so the pt is symptomatic.
For every point decrease in albumin, the calcium level decreases by 0.8
What diagnostic tests are used to see if hypocalcemia is symptomatic? What are the findings?
EKG shows QT prolongation that may eventually cause arrhythmia.
Slit lamp exam shows early cataracts.
What is the Rx for hypocalcemia?
Replace Ca and Vit D - orally if Sx are absent or mild, intravenously if Sx are severe.
What are the 3 mechanisms that cause hyperkalemia?
- Pseudohyperkalemia
- Decreased excretion
- Release of K from tissues
What are the causes of pseudohyperkalemia?
- Hemolysis
- Repeated fist clenching with tourniquet in place
- Thrombocytosis or leukocytosis will leak out of cells in the lab specimen
*None of these require further treatment or investigation beyond repeating the sample.
What are the causes of hyperkalemia due to decreased excretion?
1) Renal failure
2) Aldosterone decrease:
- ACEIs or ARBs
- Type IV RTA (hyporeninemic, hypoaldosteronism)
- Spironolactone and eplerenone (aldosterone inhibitors)
- Triamterene and amiloride (other K-sparing diuretics)
- Addison disease
What causes hyperkalemia due to release of K from tissues?
- Any tissue destruction, such as hemolysis, rhabdomyolysis, or tumor lysis syndrome.
- Decreased insulin
- Acidosis: cells pick up H and release K in exchange
- B-blockers and digoxin: inhibit the Na/K ATPase that drives K into cells
- Heparin
Besides looking at the potassium level, what test(s) must also be done for hyperkalemia? What are the findings?
EKG is the most urgent test in severe hyperkalemia, primarily because Rx is based on severity and hyperK is considered severe when their are findings on EKG, such as:
- Peaked T waves
- Wide QRS
- PR interval prolongation
What is the most important Rx for severe hyperkalemia? What else is used?
Severe hyperkalemia means there is an abnormal EKG. The first and most important Rx is calcium chloride or calcium gluconate because it stabilizes the cell membrane. The time of onset is only a few minutes. Other treatments include:
- Insulin and D50W drive K+ into cells; onset 15-30 min
- Bicarbonate is used when acidosis is the cause of hyperK; drives K+ into cells in exchange for H+; onset 15-30 min
- Hemodialysis decreases total body K+ in cases of renal failure or life-threatening hyperK
