HYPONATREMIA

Question 1

MANAGEMENT

Answer 1

1. TREAT NEUROLOGICAL EMERGENCIES RELATED TO HYPONATREMIA WITH HYPERTONIC SOLUTION:

Indications: Na <120 mEq AND Seizures or Obtundation or Coma or Headache / Nausea / Vomiting, suspected cerebral herniation

100 ml of 3% hypertonic saline IV over 10 min

If symptoms persist, 1-2 additional boluses may be given

OR

8.4% Sodium Bicarbonate, 2 mL / kg

STOP ALL FLUIDS after the second bolus

Recheck serum sodium level 1-2 hr after each bolus

Goal: Increase Na by 4-6 mmol. Limit increase to no more than 6 mmol during first 6 hrs OR 8 mmol / L in first 24 hrs.

Saline Lock

DDAVP 1-2 ug SC / IV while using 3% Saline to prevent over correction. USE WITH CAUTION.

2. DEFEND INTAVASCULAR VOLUME

HYPOVOLEMIC:
250-500 cc LR IV guided by BP
LR closer to hyponatremic patient, will not raise the Na as quickly

EUVOLEMIC:
NPO
Saline Lock

HYPERVOLEMIC:
NPO
Fluid Restriction
Sodium restriction
IV Furosemide

3. PREVENT WORSENING OF THE HYPONATREMIA

Strict Fluid restriction

Saline lock the IV

4. PREVENT RAPID OVERCORRECTION

Insert a foley catheter and monitor the ins and outs. Check urine output q hr

If urine output > 100 cc / hour, send a STAT urine osmolarity and urine sodium

If urine osmolarity < 100, consider administering 1 ug DDVAP IV

Continue steps 2-3 as per urine output

5. CORRECT THE HYPONATREMIA: RULE OF 6’s

6 mmol in the first 6 hours for severe symptoms

Otherwise, 6-8 mmol / day

6. ASCERTAIN THE CAUSE OF THE HYPONATREMIA

INVESTIGATIONS
Volume Status Exam
Serum {Na}
Serum Osmolality
Urinary Sodium (U Na)
Urine Osmolality (U Osm)
Cortisol
TSH

MONITOR
seizures
coma
respiratory arrest

DISPOSITION
Severe (Na < 120): Stepdown
Moderate (120-129): Hospitalist

Question 2

DOCUMENTATION

Answer 2

CLINICAL FEATURES

Mild to Moderate Hyponatremia: MC Chronic
headache
fatigue
lethargy
nausea / vomiting
dizziness
confusion
ataxia
muscle cramping

Severe:
Seizure
Obtundation
Coma
Respiratory Arrest

i. Chief Complaint: look for conditions which can increase output or decrease intake such as vomiting and diarrhea, pain or altered level of awareness

ii. Meds: look for those that cause SIADH
Thiazide diuretics (most common)
Loop diuretics
Antipsychotics
Angiotensin-converting enzyme inhibitors
Angiotensin receptor blockers
Spironolactone
Selective serotonin reuptake inhibitors
patients who have been on chronic steroids may have adrenal insufficiency

iii. PMHx: look for history of end organ failure (CHF, liver failure, renal failure) or cancer (SIADH)

iv. Labs: Glucose (hyperglycemia), potassium (hyperkalemia may suggest adrenal insufficiency), TSH (hypothyroidism)

Question 3

DDX

Answer 3

HYPEROSMOLAR HYPONATREMIA
Hyperglycemia
High Protein (myeloma, IVIG)
Hypertriglyceridemia
Exogenous osmoles

HYPERVOLEMIC HYPOTONIC HYPONATREMIA

Urine Na < 20:
CHF
Cirrhosis

Urine Na > 20:
CKD?
Nephrotic Syndrome

EUVOLEMIC HYPOTONIC HYPONATREMIA

Urine Na > 20: RATS
RTA IV
Adrenal Insufficiency (Addison’s) (early)
HypoThyroid
SIADH (MOST COMMON)

Water>Solute Intake:
Psychogenic Polydipsia (MOST COMMON)
Beer Potomania
Low-solute-diet (tea and toast)

Urine OSM Low
Urine Na Low

HYPOTONIC HYPOVOLEMIC HYPONATREMIA:
Renal vs. Non Renal Causes

Urine Na > 20: Renal
Diuretics
Hypoaldosterone (late)

Urine Na < 20: Non Renal
Diarrhea / Vomit
Reduced PO intake
Sweat / Burn