Electrolytes Flashcards
How does aldosterone affect sodium
aldosterone causes:
- increased sodium reabsorption
- increased potassium excretion
What is the most common electrolyte abnormality in hospitalized patients
hyponatremia
What is the most common result of hyponatreamia?
Seizures
What is pseudohyponatremia?
Serum Na is <135 but NORMAL osmolality due to hyperlipidemia and hyperproteinemia
What is a common cause of redistributive hyponatremia?
hyperglycemia
Euvolemic Hyponatremia: treatment
fluid restriction, treat underlying cause
Euvolemic Hyponatremia: causes
- SIADH
- Primary polydipsia
- Hypothyroidism
- Adrenal Insufficiency
What are the hallmark findings of SIADH?
-concentrated urine with low serum osmolality and euvolemia
If a patient presents with hyponatremia, what are the first labs you would want?
- UA -sodium
- UA - osm
- serum osm
- CMP
What should you do if a patient’s Na is less than 125?
Hospitalize!!
Rapid increase in serum sodium can lead to what?
cerebral pontine myelinolysis
Treatment of Hyponatreamia: rate of correction
First 24 hours: 6-12 mEq/L
First 48 hours: Less than 18 mEq/L in 48 hours
How often should you check serum sodium when you are replacing to make sure you aren’t overcorrecting?
every 2 hours
If a patient has low serum sodium and high serum osmolarity what is the most likely cause?
Hyperglycemia
If a patient has high urine osmolarity and is hypervolemia what two things might you suspect?
- CHF
2. Cirrhosis
If a patient has high urine osmolarity and is euvolemic what might you suspect?
- SIADH
- Hypothyroid
- Adrenal Insufficiency
If a patient has high urine osmolarity and is hypovolemic and urine sodium is <10 what might be the cause?
vomiting or diarrhea
If a patient has high urine osmolarity and is hypovolemic and has urine sodium >20 what might be the cause?
Adrenal insufficiency
Diuretics
At what level is someone technically hypernatremic?
> 145mEq/L
What are the two causes of Diabetes insipidus?
- Central DI - ADH isn’t being secreted
2. Nephrogenic DI - kidneys aren’t responding to ADH
What is the treatment for nephrogenic diabetes insipidus?
Thiazide diuretic**
How is water deficit calculated?
Normal Total Body Water - current Total Body Water
Where does regulation of renal K+ excretion take place in the nephron?
distal nephron
under the influence of aldosterone which increases sodium reabsorption and increases renal K+ excretion
Hypokalemia: clinical manifestations
- Hyporeflexia*
- Muscle cramps*
- Weakness, fatigue
- Flaccid paralysis (ascending)
Hypokalemia: ECG findings
- PVCs
- Flattened T waves
- Prominent U waves
- Depressed ST segments
Name the causes of Hypokalemia (8)
- insulin
- caffeine
- bronchodilators
- hyperthyroidism
- Metabolic alkalosis
- Diuretics***
- Cushing’s
- Vomiting or diarrhea
If a patient is low on potassium what is the best way to replace?
oral potassium replacement is preferred over IV as it has better absorption and won’t damage vessels
Hyperkalemia - ECG
(in order of progression):
- peaked T waves
- Widened QRS
- Junctional rhythm
- Ventricular fibrillation
Name some causes of Hyperkalemia
- Drugs (ACE, ARB, K+ sparing diuretics, NSAIDs, Bactrim)
- rhabdomyolysis
- Acidosis
- Decreased Insulin
Hyperkalemia: Emergent Treatment
- IV calcium to stabilize membrane
- Sodium Bicarbonate (increases pH, K+ is exchanged for H+ in the cells)
- Insulin (add with sugar)
- IV lasix
Hyperkalemia: not urgent
Kaexalate - exchanges sodium for potassium in the gut
or
Lasix (furosemide)
When calicum goes up ______ will go down
phosphate
ECF calcium
Free - 50%
Protein bound - 40%
Complexed - 10%
Serum calcium is impacted by what other substance?
albumin
So, in hypoalbuminemia need to correct the measured calcium level
At what level is calcium considered Hypercalcemia?
Calcium >10.1
What are the symptoms of hypercalemia?
- Kidney stones
- Bone pain
- Abdominal pain, N/V, constipation
- Fatigue, lethargy, memory loss, psychosis
- Decreased neuromuscular excitability
What will happen to the QT interval with Hypercalcemia?
shortened QT
What are the 2 biggest causes of hypercalcemia
- Malignancy
2. Primary hyperparathyroidism
Which medications can cause Hypercalcemia?
- Thiazide diurectics
- Antacids
- Lithium
- Vitamin A analogs (Accutane)
Hypercalcemia: Treatment
- Volume expansion - Normal saline!***
- Calcitonin
- Pamidronate
- Zoledronic Acid
Hypocalemia: clinical presentation
- Increased neuromuscular excitability (tetany)**
- Parestheisas around lips, fingers and toes
- Hyperreflexes
- Chvostek’s Sign
- Trousseau’s Sign
What are the cardiovascular effects of hypocalcemia?
- Prolonged QT inverval, arrhythmia
2. Hypotension
Hypocalcemia: Causes
- Hypoalbuminemia
- Large blood transfusion (citrate additives bind free calcium)
- Hypomagnesemia (need Mg to help PTH work properly)
- Hypoparathyroidism
- Renal failure - retention of phosphate and reciprocal loss of Ca
- Malabsorption/Vitamin D deficiency
What will happen to phosphate in refeeding syndrome?
Phosphate floods into cells and causes cell death
What two conditions do you need to first correct hypomagnesemia before you can fix them?
- Ca++
2. K+
