5b.) Sodium Clinical Lecture Flashcards
Case Study 1
- 68 year old male
- Admitted recurrent falls
- Epilepsy post stroke 6 years ago
- Smoker- 30 pack year
- Medication: epilepsy meds, aspirin
- BP, GCS, temp, CVS/GI/resp all fine
- Mini mental score: 6/10
- Ataxic gate, intention tremour
- Electrolytes: Low [Na+]
Future tests show:
- Serum osmolarity decreased
- Urine osmolarity increased
- Urine Na+ increased
SIADH
Syndrome of inappropriate anti-diuretic hormone secretion. Too much ADH causes too much water to be reabsorbed which will result in:
- Serum osmolarity decreased
- Urine osmolarity increased
Why might serum osmolarity low?
- Decreased effective osmoles
- Too much water
Hyponatremia is generally a problem with….?
Water, not Na+. Remember the results in blood test are conc of Na+. Usually conc decreased to excess water (99% time)
If someone has too much water in body, what kind of urine osmolarity would you expect?
LOW- lots of water in urine
How do you treat hyponatremia due to too much water?
- Fluid restriction
- Diuretics (rarely used)
- Hypertonic infusion (rarely used)
Medications for which illness can cause SIADH?
Epilepsy medications
Does hyponatremia often kill people?
Not often the low sodium itself. Low sodium indicates major physiologically concerns as they cannot manage water homeostasis. If you cannot maintain water homeostasis it is not a good prognosis.
State some symptoms of hyponatremia:
- Anorexia
- Headache
- Nausea
- Lethargy
- Confusion
- Muscle cramps
- Seizures
State some possible causes of true Na+ loss
- D&V (lose water and sodium so little change in osmolarity)
- Diuretics
- Peritonitis (accumulation of fluid in peritoneum)
- Burns
State some possible causes of imbalances in ADH secretion
- Heart failure
- Kidney disease
- Liver disease
- Medication
- Tumours e.g. Small cell lung carcinoma
State some drugs that cause changes/imbalances in ADH secretion
- Thiazides
- SSRIs
- PPI
- ACE inhibitors
- Loop diuretics
Why do we rarely use diuretics or hypertonic infusions to treat hyponatremia?
Cause central pontine myelinolysis or osmotic demylelination syndrome because:
- The Na+ is too rapid
- Cerebrum has adapted to compensate for low Na+ over time
- Leads to cerebral damage
How do you calculate serum osmolarity from other values on FBCs?
In what circumstances could this calculation give a false result?
Serum osmolarity= (2 x Na+) + glucose + urea
- Hyperglycaemia
- High urea- poor kidney function
What does hypo-osmolality of plasma do to brain cells?
Brain cells swell as water moves in
What does hyperosmolality do to brain cells?
Causes shrinkage as water moves out
In a patient with abnormal serum sodium, what 3 things must you consider?
- Patients volume status
- How much sodium being lost in urine
- Is patient symptomatic
State symptoms of hypernatremia
- Excessive thirst
- Fatigue
- Confusion
- Seizure
