Hypernatremia and hyponatremia Notes

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Hypernatremia

Hyponatremia

NOTES NOTES HYPERNATREMIA & HYPONATREMIA GENERALLY, WHAT ARE THEY? PATHOLOGY & CAUSES ▪ Sustained blood/sodium imbalance ▪ Sodium does not easily cross cell membrane → water drawn to ↑ concentration areas SIGNS & SYMPTOMS ▪ Hypernatremia ▫ Intracellular dehydration/systemic fluid depletion ▪ Hyponatremia ▫ Fluid shift into cells/systemic fluid overload DIAGNOSIS LAB RESULTS ▪ Serum sodium levels ▪ Urine sodium, osmolality TREATMENT OTHER INTERVENTIONS ▪ Cause-dependent ▫ Fluids/electrolyte administration ▫ Fluid restriction to restore balance HYPERNATREMIA osms.it/hypernatremia PATHOLOGY & CAUSES ▪ High sodium concentration in extracellular fluid ▫ Sodium > 145 milliequivalents/liter (mEq/L) ▪ Draws water out of cells ▪ Acute onset: no cellular adaptation → cells shrivel, die ▪ Slow onset: osmotically active particles generate → prevent water loss 808 OSMOSIS.ORG CAUSES Water loss > sodium loss ▪ Extrarenal water loss ▫ Skin losses (sweating when hot, exercising, fever), gastrointestinal (GI) losses (vomiting, drainage, diarrhea) ▪ Hypothalamic lesions ▫ Antidiuretic hormone (ADH) ↓ → dilute water loss ▫ Thirst center loss (insufficient intake), ↑ serum sodium ▫ Both ▪ Renal water loss (e.g. nephrogenic diabetes insipidus)
Chapter 114 Hypernatremia & Hyponatremia Sodium ↑ ▪ ↑ sodium intake, kidney dysfunction ▪ Iatrogenic ▫ Intravenous (IV) sodium-containing solutions administered too quickly/too high concentration RISK FACTORS ▪ Uncontrolled diabetes, underlying polyuria disorder, diuretic therapy, inability to act on thirst impulse, age extremes (elderly/ neonate), mental/physical impairment, nursing home residency, hospitalization COMPLICATIONS ▪ Acute hypernatremia ▫ Demyelinating brain lesions, rapid brain volume ↓ → blood vessel rupture → cerebral haemorrhage SIGNS & SYMPTOMS ▪ Dehydration ▫ Thirst, sunken orbits, dry mucous membranes, reduced skin turgor, postural hypotension, tachycardia ▪ Acute hypernatremia ▫ Lethargy, weakness, irritability, twitching, seizure, coma ▪ Long-standing hypernatremia ▫ Fewer symptoms, cells adjust MNEMONIC: FRIED SALT Hypernatremia Signs & Symptoms Fever (low), Flushed skin Restless (irritable) Increased fluid retention, Increased blood pressure Edema (peripheral, pitting) Decreased urinary output, Dry mouth Skin flushed Agitated Low-grade fever Thirst DIAGNOSIS LAB RESULTS ▪ Measure blood sodium ▫ Hypernatremia: > 145mEq/L Intravascular volume hypovolemic ▪ Drinking too little/losing too much water ▫ Urine osmolality: > 600 milliosmoles per kilogram (mOsm/kg) ▫ Urine sodium: < 20mEq/L ▪ Kidneys losing sodium ▫ Urine sodium: > 20mEq/L ▫ Kidney disease, medications (e.g. osmotic,loop diuretics) ▪ Euvolemic ▫ Urine osmolality: < 300mOsm/kg ▫ Urine sodium: < 20mEq/L ▫ Kidneys losing water (diabetes insipidus) TREATMENT OTHER INTERVENTIONS ▪ ↓ sodium concentration ▪ ↑ water intake ▫ Extrarenal water loss ▫ Diabetes insipidus, normal thirst mechanism ▪ Monitor serum sodium, glucose ▫ Dextrose water hydration, isotonic to plasma, electrolyte free ▫ Overly dextrose water infusion → hyperglycemia → osmotic diuresis, counteracting rehydration efforts ▪ Chronic cases ▫ Slower correction ▪ IV 5% dextrose water → lowers sodium ▫ Hypernatremia correction with IV fluids → practice care to avoid cerebral edema ▪ Rapid overcorrection ▫ Administer sodium-containing IV fluids (e.g. saline, Ringer’s lactate) ▪ Concomitant extracellular fluid depletion presenting with severe hypernatremia, hypovolemia signs ▫ Isotonic sodium containing fluids OSMOSIS.ORG 809
HYPONATREMIA osms.it/hyponatremia PATHOLOGY & CAUSES ▪ Low sodium concentration in extracellular fluid ▫ < 135mEq/L TYPES Hypervolemic hyponatremia ▪ Significant total body water ↑, small sodium ↑ ▪ Congestive heart failure, hepatic cirrhosis, nephrotic syndrome, water lost to extracellular space → circulating volume ↓ → ADH, aldosterone released → pure water retention ↑, sodium retention ↑ (further pure water retention ↑) Hypovolemic hyponatremia ▪ Small total body water, large sodium ↓ ▪ Diarrhea, vomiting, medications (e.g. diuretics) → sodium actively pumped into GI tract ▪ Cerebral salt wasting, intracranial injury/ infection disrupts kidney sympathetic stimulation → ↑ sodium loss Euvolemic hyponatremia ▪ ↑ body water, no body sodium change ▪ Dilute urine ▫ Adrenal insufficiency, hypothyroidism, polydipsia (excessive water drinking), potomania (excessive beer drinking) ▪ Concentrated urine ▫ Syndrome of inappropriate antidiuretic hormone secretion (SIADH) False hyponatremia/pseudohyponatremia ▪ No water, sodium level changes ▪ Hypertriglyceridemia (excessive lipid concentration), multiple myeloma (excessive protein concentration) → affect lab equipment → false sodium reading 810 OSMOSIS.ORG CAUSES ▪ Sodium loss > water loss ▪ Water gain > sodium gain COMPLICATIONS ▪ Sudden/severe hyponatremia → water shifts into brain cells → swelling → ↑ intracranial pressure → ischaemia/ herniation → respiratory center damage → death ▪ Excessively rapid sodium-level correction → cerebral pontine myelinolysis (rapid sodium, water shifts → myelin-loss in pons) SIGNS & SYMPTOMS ▪ Nausea, vomiting, muscle cramps, confusion, seizure, coma DIAGNOSIS LAB RESULTS ▪ Measure serum sodium concentration ▫ <135mEq/L ▪ Measure serum osmolality (hyponatremia, pseudohyponatremia) ▪ Edema: hypervolemic hyponatremia ▪ Dehydration: hypovolemic hyponatremia ▪ Urine osmolality: dilute, concentrated euvolemic hyponatremia ▪ Urine concentration ▫ > 100mOsm/kg → SIADH ▪ Dilute urine ▫ < 100mOsm/kg → excessive fluid intake ▪ Urine sodium ▫ > 20–40mEq/L → SIADH, cerebral salt wasting ▪ Urine sodium ▫ < 20mEq/L → hypovolemia
Chapter 114 Hypernatremia & Hyponatremia TREATMENT OTHER INTERVENTIONS ▪ SIADH ▫ Fluid restriction ▪ Hypovolemia ▫ Fluids ▪ Hyponatremia ▫ Hypertonic saline (slowly—prevents cerebral pontine myelinolysis) Figure 114.1 An MRI scan in the sagittal plane demonstrating central pontine myelinolysis. There is faint, but well demarcated, hypoattenuation in the centre of the pons. OSMOSIS.ORG 811

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