N15 - Electrolyte Disorders Flashcards
What is hypokalemia?
- definition: serum potassium (K+) is < 3.5mmol/L
- clinical manifestations: hypertension, arrhythmia, sudden cardiac death, weakness, rhabdomyolysis, alterations in acid-base balance (metabolic alkalosis), paralytic ileus
- long-term effects: mortality, risks of cardiovascular disease increases, renal cyst formation, renal fibrosis
What is the etiology for hypokalemia?
pseudohypokalemia
- artifact in blood sample
- ie. acutre leukemia (leukocytes take up potassium)
redistribution
- K+ shifts from the ECF to the ICF
- aldosterone increases, β2-adrenergic effects, anabolic state, insulin, alkalosis
extrarenal loss
- diarrhea, vomiting (alkalosis), sweating, laxative abuse
renal loss
- medication: thiazide, furosemide, piperacillin-tazobactam, aminoglycosides
- bicarbonaturia
- magnesium deficiency (increased ROMK-mediated K secretion)
- genetic diseases (Bartter syndrome, Gitelman syndrome)
- hormonal diseases (Liddle syndrome, Cushing syndrome, hyperaldosteronism)
What is the treatment for hypokalemia?
urgent therapy:
- in case of paralysis, AMI, ventricular ectopy
- max. speed: 5-10 mmol KCl in 20 mins
- monitor ECG
- avoid solution with dextrose (increase in insulin levels can worsen hypokalemia)
lack of severe symptoms:
- per os supplementation
magnesium depletion:
- magnesium supplementation
What is hyperkalemia?
- definition: serum K+ > 5.5mmol/L
- clinical manifestations: can be asymptomatic, mild or life-threatening; muscle weakness (diaphragmatic muscle-respiratory failure); metabolic acidosis; ECG changes (peaked T-waves, ST-depression, prolonged QRS, ventricular fibrillation etc.)
- long-term effects: increased risk of mortality
What are ECG changes in hyperkalemia?
- 6-7mmol/L K+: peaked T waves
- 7-8mmol/L K+: flattened P wave, prolonged PR interval, depressed ST segment, peaked T wave
- 8-9mmol/L K+: atrial standstill, prolonged QRS duration, further peaking T waves
- >9mmol/L K+: sinusoid wave pattern
What is the etiology of hyperkalemia?
pseudohyperkalemia
- artifact in the blood sample
- ie. hemolysis, difficult phlebotomy
redistribution
- K+ moves from ICF to ECF, or there could be inhibition of ICF uptake of K+
- hyperglycemia, insulin resistance, acidosis, hyperosmolarity (mannitol), medications (digoxin, β2-antagonist)
excess intake (w/ damaged excretion)
- salt substitutes, enteral nutrition products, high-potassium diet
impaired renal excretion
- medication (ACEi, ARB, spironolactone)
- obstructive uropathy, other renal failure
- aldosterone deficiency/resistance, Addison’s disease, pseudohypoaldosteronism
What is the treatment for hyperkalemia?
if ECG changes, sever symptoms present:
- 10% Ca-gluconate (10ml/10min); for membrane stabilization and its effect lasts 20-60 mins
- insulin (4-10U/h) + 10% dextrose iv. (monitor serum glucose)
- hemodialysis
- β2 agonist by nebulizer (albuterol)
potassium removal:
- resin 15-60g/day (Na+/Ca+ polystyren-sulfonate, per os or as retention enema)
- diuretics: furosemide, thiazide
treatment of chronic hyperkalemia:
- in CKD, therapeutic goal is >5.5mM but >6.0mM is acceptable too
- review of medication
- dietary restrictions
- intermittent resin/Patiromer treatment
- Fludrocortisone (hypoaldosteronism)
What is hyponatremia?
- definition: serum Na+ <135mmol/L (clinical signs usually begin <125mmol/L)
- clinical manifestations: headache, yawning, lethargy, nausea, reversible ataxia, psychosis, seizures, cerebral edema, tentorial herniation, respiratory depression
What is the differential diagnosis for hyponatremia?
pseudohyponatremia:
- serum Na+ ↓, serum osmolarity is normal
- solid phase of serum increases (ie. hypertriglyceridemia, paraproteinemia)
translocational hyponatremia
- serum Na+ ↓ and serum osm. ↑
- movement of water from ICF to ECF due to osmotically active substances (ie. glucose, mannitol, glycine, maltose)
real/hypotonic hyponatremia:
- serum Na+ ↓ and serum osm. ↓
What is the etiology of hyponatremia?
assess volume status, first!!
hypovolemia
- hypovolemia as a result of decreased TBW, and consequently very low total body Na+
- if urine Na ≥ 20mM, then it is due to renal losses
- if urine Na < 20mM, the it is due to extrarenal losses
euvolemia
- TBW increased with normal total body Na+
- urine Na > 20mM
hypervolemia
- TBW is very high and total body Na increases too
- if urine Na ≥ 20mM, then it is due to renal loss w/ water retention
- if urine Na < 20mM, the it is due to water retention
What renal volume loss can cause hypovolemic hyponatremia?
- diuretics (thiazide!)
- mineralocorticoid deficiency
- salt-losing nephropathy
- bicarbonaturia (renal tubular acidosis, metabolic alkalosis)
- osmotic diuresis
What extrarenal volume loss can cause hypovolemic hyponatremia?
- vomiting
- diarrhea
- burns, trauma
- pancreatitis
What are the possible causes of euvolemic hyponatremia?
- glucocorticoid deficiency
- hypothyroidism
- medication, drugs
- SIAD
What renal volume loss w/ water retention can cause hypervolemic hyponatremia?
acute or chronic kidney injury
What are the possible causes of water retention?
- cardiac failure
- cirrhosis
- nephrotic syndrome
What is SIAD?
SIAD: syndrome of inappropriate antidiuresis
- a defect in osmoregulation causes vasopressin (AVP/ADH) to be inappropriately stimulated
diagnostic criteria
- serum osm. ↓, urine osm. > 100mOsm/kgH2O, urin Na > 20mmol/L
- euvolemia
- diagnosis by exclusion: absence of adrenal, thyroid, pituitary, or renal insufficiency; or absence of diuretic use
supplementary criteria
- abnormal water-load test result (inability to excrete, failure to dilute urine)
- serum Na is almost not corrected with any volume expansion
- serum uric acid ↓, fractional excretion of uric acid ↑
What medication/drugs cause hyponatremia?
- thiazide (-like) diuretics
- SSRI, tricyclic antidepressants, haloperidol
- vasopressin analogs (desmopressin, oxytocin)
- carbamazepine
- NSAID (nonsteroidal anti-inflammatory drugs)
- clofibrate
- cyclophosphamide
- iv. immune globulin (IVIG)
- vincristine
- nicotine
- metamphetamin (ecstasy)
How is acute hyponatremia treated?
- acute (symptoms within 48 hours)
- 1-2 mL/kg 3% NaCl infusion in 1 hour ± furosemide (to reach serum Na+ of 4-6mmol/L
- SLOW correction to normal level
How is chronic hyponatremia treated?
- chronic: (>48h symptoms or unknown duration)
- in case of severe symptoms, same treatment as acute hyponatremia
- in case of moderate symptoms, 0.9% NaCl infusion w/ furosemide
- in case its asymptomatic, no immediate correction is needed but identify the cause
How is chronic hypovolemic hyponatremia treated?
- 0.9% NaCl infusion, per os fluids
- increase per os Na intake
- stop diuretics
How is hypervolemic chronic hyponatremia treated?
- usually in case of heart failure or cirrhosis
- water and salt restriction
- furosemide, V2-R antagonists (vaptans)
How is euvolemic chronic hyponatremia treated?
- water restriction: 500-1500mL/day w/ furosemide
- increase in per os Na intake, V2-R antagonists (vaptans)
What to be cautious of when treating hyponatremia?
acute, severe hyponatremia can be life threatening
- cerebral edema
- herniation
rapid correction of serum Na is life threatening
- central pontine myelinolysis (CPM); osmotic demyelination
- symptoms: encephalopathy, behavioral changes, cranial nerve palsies, progressive weakness, quadriplegia, “locked-in” syndrome
treatment efficacy is not predictable
- frequently check serum Na (every 2 hours)
- max. 8mmol/L per 24hours (1-1.5mM/hour)
- in case of rapid correction: iv. dextrose, desmopressin
What is hypernatremia?
- definition: serum Na >145mmol/L
- clinical manifestations: altered mental status, lethargy, irritability, restlessness, seizures, muscle twitching, hyperreflexia, spasticity, fever, nausea, vomitin, labored breathing
- at risk: elderly, infants, hypertonic infusions, feeding tubes, mechaical ventilation, uncontrolled DM, polyuric disorders
What is the etiology of hypernatremia?
assess volume first!!
hypovolemia
- TBW is very low and total body Na is low
- if urine Na ≥ 20mM: renal losses
- if urine Na < 20mM: extrarenal losses
euvolemia
- TBW is low but total boday Na is variable
- urine Na is variable: renal or extrarenal losses
hypervolemia
- TBW is high and total body Na is very high
- urine Na >20mM: sodium gains
What renal losses can lead to hypovolemic hypernatremia?
- diuretics (loop and osmotic)
- postobstruction (polyuria)
- osmotic diuresis (DM)
- intrinsic renal disease
What extrarenal losses can lead to hypovolemic hypernatremia?
- excess sweating
- diarrhea
- burns
- fistulas
What renal losses lead to euvolemic hypernatremia?
- diabetes insipidus
- hypodipsia
What extrarenal losses lead to euvolemic hypernatremia?
- respiratory loss
- dermal loss
What sodium gains can lead to hypervolemic hypernatremia?
- primary hyperaldosteronism
- cushing’s syndrome
- NaCl tablets
- hypertonic infusions (NaHCO3, NaCl)
- hypertonic dialysis
What is the treatment for hypovolemic hypernatremia?
- correction of volume deficit (0.9% NaCl), treatment of the cause
- correction of water deficit (0.45% NaCl, 5% dextrose, per os water)
What is the treatment for euvolemic hypernatremia?
- correction of water deficit (0.45% NaCl, 5% dextrose, per os water)
- long-term therapy (diabetes insipidus, vasopressin analog)
What is the treatment for hypervolemic hypernatremia?
- treatment of cause
- removal of Na: furosemide, hemodialysis as needed (renal failure)
What is the maximum speed of correction for hypernatremia?
2mmol/L/hour, 10mmol/L/day
caution: cerebral edema
Overview of hypermagnesemia
- normal Mg level: 0.75 - 1.0 mmol/L
- causes: renal failure; Mg supplements; familial hypocalciuric hypercalcemia; acromegaly; adrenal insufficiency
- symptoms: deep tendon reflexes decrease (>3mM), paralysis (>5mM)
- treatment: Ca-gluconate iv.
Overview of hypomagnesemia
- normal Mg level: 0.75 - 1.0 mmol/L
- causes: decreased intake, malabsorption; increased excretion; medication; acute pancreatitis; chronic alcoholism; idiopathic
- symptoms: weakness, hyperreflexia, tremor, spasm, ECG changes
- treatment: MgSO4 iv., per os Mg-salts
What can lead to increased excretion of Mg?
- polyuric disease
- prolonged infusion with excessive Na
- primary aldosteronism
- metabolic acidosis
- phosphate deficiency
- hyperthyroidism
- Gitelman syndrome
What medications can lead to hypomagnesemia?
aminoglycosides, calcineurin inhibitors, cisplatin, amphotericin, thiazide
What are the ECG changes in hypomagnesemia?
- prolonged QT interval
- ST depression
- risk of arrythmias increases
