Hypernatremia Flashcards
Definition?
An electrolyte imbalance consisting of a rise in serum sodium concentration. Hypernatraemia is defined as a serum sodium concentration of >145 mmol/L
RF?
- Dehydration
- Infancy
- Old age
- Renal concentrating defect
- GI disorders
- Insensible water losses
- DI
- Drugs
- Large salt intake
- Traumatic brain injury
- Primary hypodipsia
DDX?
spurious
Epidemiology?
Age: Infants/older pts
Sex:
Ethnicity:
P:
Aetiology?
Hypovolaemic
euvolaemic
hypervolaemic
hypovolaemic?
- Description:high serum Na+levels with decreased extracellular volume as a result of hypotonic fluid loss
- Extrarenal cause(manifests witholiguriadue todehydration)
- Gastrointestinal loss(e.g.diarrhea, vomiting, drainage from nasogastric tubes,fistula)
- Dermalfluid loss (e.g.,burns,excessive sweating)
- Third-spacing(peritonitis,ascites)
- Renal cause(leads todehydrationdue topolyuria)
- Diuretics
- Osmotic diuresis(e.g.,hyperglycemia,mannitol,uremia,high-proteintube feeding,osmotic diuretics)
- Recovery (polyuric) phase ofacute tubular necrosis
euvolaemic?
• Description: high serum Na+levels with normal or minimal changes in extracellular volume as a result of pure water deficit
• Extrarenal causes(manifests witholiguriadue to decreased water intake)
• Lack of access to water
○ Altered mental status (e.g.,dementia, drug-induced)
○ Immobilization
○ Physically restrained patients
○ Quadriparesis
• Impaired thirst mechanism: primary hypodipsia
• Mechanical ventilation
• Renal cause(causes increased thirst due topolyuria)
• Diabetes insipidus
○ Central: complete or partial lack ofADHsecretion
○ Nephrogenic: complete or partial resistance to the action ofADH
Hypervolaemic?
- Description: high serum Na+levels with increased extracellular volume as a result of intake of hypertonic water or retention of sodium in excess of water
- Extrarenal causes(initially manifests withpolyuriadue to fluid overload, followed bydehydrationdue topolyuria)
- Iatrogenic: excessive infusion of NaCl,sodium bicarbonatesolutions, or hypertonic saline;hemodialysis
- Seawater consumption
- Renal causes(causeshypertensionandhypokalemiawith normalurineoutput and no fluid overload)
- Primary hyperaldosteronism
- Cushing syndrome
CP?-acute?
Symptoms are primarily neurological and depend on the severity of hypernatremia. • Mild symptoms:signs ofdehydration • Decreased salivation • Drymucous membranesandskin • Moderate symptoms • Confusion • Irritability, restlessness • Lethargy • Muscle weakness • Hyperreflexia • Severe symptoms: typically occur only withsevere hypernatremia (serum concentration> 160 mEq/L)[2] • Focal neurological deficits • Seizures • Altered consciousness • Stupor • Coma
CP-chronic?
- Often asymptomatic or nonspecific, mild symptoms
- Commonly:signs ofdehydration(especially inhypovolemic hypernatremia)
- Rarely: irritability,anorexia, nausea, weakness, and/or altered mental status
CP GI Loss?
diarrhoea
n and v
NG tube
enteric fistula
CP Skin?
febrile
burns
increased sweating
CP dehydration
vulnerable
immobile
ENT
Incorrect fluids
CP Impaired thirst
elderly
dementia
no change in recent fluid intake
excessive salt intake
iatrogenic
ingestion
Patho?
- Either losing more water than sodium or gaining more sodium than wate-increased sodium conc-draws water out
- Chronic-osmotically active particles are generated to stop water from moving out
- Acute-no adaptation-water leaves-shrivel
- Dehydration-thirst is increased
- Central DI-no signal from hypothalamus to release ADH and increase absorption in the DCT/CD-can drink more water
- Nephrogenic DI-receptors in CD don’t respond to ADH release-drink more water
- Damage to thirst water-no response
- Sodium gain
- IV fluids
- Increased diet
- Precipitated by worsening kidney function
Investigations-first line
- History and exam
- Electrolyte panel-high sodium, urea, creatinine,hypokalaemia
- Urine osmolality
- High UOsm(> 600 mOsmol/kg) supports an extarenal mechanism.
- Low UOsm(< 600 mOsmol/kg) supports an intrarenal mechanism.
- Serum osmolality-hyperosmolality
- Urine electrolytes
- UNa< 20 mEq/Lsupportshypovolemia.
- UNa> 100 mEq/Lsupports sodium overload
- Urine flow rate-to help calculate electrolyte-free water excretion
Investigations second line
- Desmopressin challenge test-DI
- AVP level-low
- MRI or CT brain-pituitary adenoma
- Find underlying cause
What is free water deficit?
ideal serum Na
Electrolytes free water ?
Vx (1- Urinary sodium and potassium/ plasma sodium)
Management fluids?
- Give water orally if possible. If not, give glucose 5%ivslowly (1L/6h) guided by urine output and plasma Na+. Use 0.9% salineivif hypovolaemic, since this causes less marked fluid shifts and is hypotonic in a hypertonic patient.
- Avoid hypertonic solutions.
- Some physicians recommend an initial rate of approximately 3-6 mL/kg/hour (acute hypernatraemia) or 1.35 mL/kg/hour (chronic hypernatraemia)
- Serum sodium correction rate: in patients with severe symptoms (e.g., neurological symptoms), the serum sodium concentration should be lowered by 2 mmol/L/hour in the first 2-3 hours, followed by a correction rate of 0.5 mmol/L/hour thereafter.
Management next?
- Treatment of the underlying cause (e.g., giving insulin, treating renal failure/obstructive uropathy, treating nausea/diarrhoea/fever) should be a priority.
- Causative medications (e.g., mannitol, loop diuretics, activated charcoal/sorbitol) should be ceased.
- Monitoring
- Frequent measurement of the serum sodium concentration (e.g., every 1-2 hours for acute hypernatraemia or every 4-6 hours for chronic hypernatraemia until stable, then every 12-24 hours) is necessary to make sure that levels are returning to the correct range at the desired rate.
- Urine sodium concentration, urine osmolality, and urine output.
- Serum electrolytes should also be monitored to assess for electrolyte imbalances (e.g., hypokalaemia)
- serum glucose to assess for treatment-related hyperglycemia (if dextrose-containing solutions are used).
Management second line?
• Desmopressin- Central DI
Thiazide-Nephrogenic DI
Managment Third line?
RRT
Prognosis?
- MR 32-70%
- Hospital-acquired is worse
- Severity worse than duration
Complications?
• Treatment-related brain oedema • Treatment releated hyperglycaemia • Myelinolysis • Rhabdomyolysis • Cardiac toxicity Metabolic effects
Complications?
• Treatment-related brain oedema • Treatment related hyperglycaemia • Myelinolysis • Rhabdomyolysis • Cardiac toxicity Metabolic effects
