Hyponatremia Lecture Notes

Comprehensive vocabulary flashcards covering the definitions, causes, classifications by osmolality, symptoms, and treatment protocols for Hyponatremia based on the lecture notes.

Hyponatremia

A condition where the blood sodium level goes below $135\,mEq/L$.

three types of hypotonic (<280) hyponatremia

hypovolemic, euvolemic, and hypervolemic hyponatremia.

indication for renal cause of hypotonic hyponatrmia

U Na+ > 20meq/L

renal cause of hypotonic hyponatremia

renal salt loss: Diuretics, ACE inhabitors, mineralocorticoid deficiency.

other casuse for hypotonic hyponatremia (UNa+>20mEq/L)

dehydration, Diarrhea, vomiting. third space fluid losting (eg: pancreatitis)

Cerebral salt-wasting syndrome

A cause of hypovolemic hyponatremia characterized by increased brain natriuretic peptide.

Hypervolemic Hyponatremia (hypotonic) uninary sosium < 20 mEq/ L

Heart failure, cirrhosis, nephrosis, hypoalbiuminemia, which leads to an increase in total body water relative to sodium, causing diluted serum sodium levels.

Hypervolemic Hyponatremia (hypotonic) uninary sosium > 20 mEq/ L

renal failure, causing an inability to excrete free water, resulting in diluted serum sodium levels.

Euvolemic Hyponatremia

A subtype involving drugs (vasopressin, SSRIs, thiazides, carbamazepine ACE inhabitor), SIADH, Addison’s disease hypothyroidism, or high fluid intake (primary polydipsia, beer potomania).

Isotonic hyponatremia

Hyponatremia occurring with a normal serum osmolality of $\text{280-290 msOm/kg}$ ,pseudohyona often due to hyperproteinemia or hyperlipidemia.

Hypotonic hyponatremia

Hyponatremia occurring with low serum osmolality ($<280\,mOsm/kg$).

Hypertonic hyponatremia

Hyponatremia occurring with high serum osmolality (>290\,mOsm/kg caused by hyperglycemia, mannitol, sorbitol, glycerol, maltose, or radiocontrast agents.

Extrarenal salt loss

Hypovolemic condition characterized by a urinary sodium concentration of $UNa^+ < 10\,mEq/L$, seen in dehydration, diarrhea, and vomiting.

Renal salt loss

Hypovolemic condition characterized by a urinary sodium concentration of $UNa^+ > 20\,mEq/L$, seen with diuretics, ACE inhibitors, nephropathies, and mineralocorticoid deficiency.

SIADH (Syndrome of inappropriate antidiuretic hormone)

A cause of euvolemic hyponatremia which can be triggered by CNS disorders, ectopic ADH production (small cell carcinoma of the lung), drugs( Carbamazepine), HIV, pulmonary diseases, or postoperative pain medication.

Ectopic production of ADH

A cause of SIADH most commonly associated with small cell carcinoma of the lung.

Hyponatremia Clinical Symptoms

Nausea, vomiting, headache, confusion, fatigue, low blood pressure, loss of energy, muscle weakness, twitching, cramps, seizures, coma, and restlessness.

Severe Hyponatremia Treatment

Defined as values $<120\,mmol/L$; requires hypertonic $3\%$ saline in the first-hour.

Moderately severe hyponatremia

Defined as values between $\text{120-130 mmol/L}$; treated with hypertonic $3\%$ saline while limiting the increase in serum sodium concentration. Limited the increase in serum concentration to avoid associated complications such as osmotic demyelination syndrome.

Osmotic demyelination syndrome

A risk associated with the rapid correction of sodium levels or fluid shifts, manifesting as dysarthria, dysphagia, tetraparesis, behavioural disturbances, lethargy, confusion, and coma.

under which sodium level the patient start having symptom

< 120 mmol/L

reason for SIADH

Neurosurgical or neurological :Guillain-Barré syndrome

• Subarachnoid haemorrhage

• Subdural haemorrhage

Infective: Meningitis, scarcoidosis

Respiratory: TB, pneumonia, pneumothroax asthma

Medications – increased ADH release:

• Antidepressants (eg sertraline)

• Anticonvulsants (eg carbamazepine, leveteiracetam)

• Antipsychotics (eg haloperidol)

• Anti-inflammatory drugs: trimethoprim

• Ecstasy

• Cyclophosphomide

Malignancy – ectopic ADH production:

• Nasopharyngeal

• Mesothelioma

• Pancreatic

• Gastrointestinal

• Lymphoma

• Sarcoma

investigation for SIADH

• biochemistry looking at serum sodium level

• serum osmolality

• urine osmolality (random sample collected at same time as serum sample)

• thyroid function tests

• morning cortisol level if hyponatraemia is potentially related to Addison’s disease

• computed tomography (CT) of the head if a neurosurgical condition is suspected (eg subarachnoid haemorrhage, subdural haematoma)⁸

• chest X-ray if pulmonary causes of SIADH are suspected.

Diagnosis of SIADH

• decreased serum osmolality (<275 mOsm/kg)

• increased urine osmolality (>100 mOsm/kg)

• euvolaemia

• increased urine sodium (>20 mmol/L)

• no other cause for hyponatraemia (no diuretic use and no suspicion of hypothyroidism, cortisol deficiency, marked hyperproteinaemia, hyperlipidaemia or hyperglycaemia).

treatment for SIADH

Asymptom: symptom (duration )