1 / 13

Approach to Hyponatremia

Approach to Hyponatremia. Core Topic UCI Internal Medicine Residency, 2012. Clinical Scenario. 74-year-old man p/w recent gastroenteritis characterized by n/v/d x 5 days, in addition to fatigue and headache.

abby
Download Presentation

Approach to Hyponatremia

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Approach to Hyponatremia Core Topic UCI Internal Medicine Residency, 2012

  2. Clinical Scenario • 74-year-old man p/w recent gastroenteritis characterized by n/v/d x 5 days, in addition to fatigue and headache. • CT head (-) in ED. No focal neurologic deficits found. He looks dry on physical exam, with no evidence of fluid overload. • BMP significant for Na+ of 118, baseline unknown. Serum osmolality is 266. Urine osmolality is 377. Urine sodium is 8. • How would you approach this patient’s hyponatremia? • How would your approach be different if this patient presented with new-onset seizures?

  3. Lecture Objectives • Hyponatremia • Clinical manifestations • Diagnostic approach • Clinical Scenario discussed

  4. Hyponatremia Defined • Definition: Serum Na+ <135 meq/L • Generally associated with decreased osmolality to <275 • Most common electrolyte abnormality in the US • Caused by retention of water • Usually a drop in osmolality will suppress ADH to allow excretion of the excess water via dilute urine • Most forms of hyponatremia are associated with elevated ADH (whether appropriate or inappropriate), which concentrates urine

  5. Signs & Symptoms • More profound when the decrease in sodium is very large or occurs rapidly(i.e. over hours) • Generally asymptomatic if Na+ level >125 • Symptoms include: • Headache • Nausea, vomiting • Muscle cramps • Disorientation, depressed reflexes, lethargy, restlessness • Seizure, coma, permanent brain damage, respiratory arrest, brainstem herniation & death • Serious complications are more commonly seen in primary polydipsia, after surgery, and in menstruating women

  6. Approach to Hyponatremia • 1st assess volume status • Is the patient volume overloaded, depleted, or euvolemic? • 2nd assess osmolality (hyper, iso, or hypo) • Is the blood concentrated? For hypotonic hyponatremia, continue to 3rd step: • 3rdassess urinary sodium excretion and FeNa % • Is the urine concentrated? *Remember VOU – volume status, osmolality, and urine studies

  7. STEP 1 – (V) Volume Status • 1st assess volume status (extracellular fluid volume) • Hypotonic hyponatremia has 3 main etiologies: • Hypovolemic – both H2O and Na decreased (H20 < Na) • Consider obvious losses from diarrhea, vomiting, dehydration, malnutrition, etc • Euvolemic – H20 increased and Na stable • Consider siADH, thyroid disease, primary polydipsia • Hypervolemic – H20 increased and Na increased (H2O > Na) • Consider obvious CHF, cirrhosis, renal failure

  8. STEP 2 - (O) Osmolality • 2nd assess osmolality hyper, iso, or hypo • Hypotonic hyponatremia = warrants further workup, especially when there is no obvious fluid overload or depletion • Serum Osmolality: lab value or calculation – in mosm/kg • =(2 x Na+) + (glucose/18) + (BUN/2.8) + (ethanol)/4.6 • Hypertonic - >295 • hyperglycemia, mannitol, glycerol • Isotonic- 280-295 • pseudo-hyponatremia from elevated lipids or protein • Hypotonic - <280 • excess fluid intake, low solute intake, renal disease, siADH, hypothyroidism, adrenal insufficiency, CHF, cirrhosis, etc.

  9. STEP 3 – (U) Urine Studies • For euvolemic hyponatremia, check urine osmolality • Urine osmolality <100 - excess water intake • Primary polydipsia, tap water enemas, post-TURP • Urine osmolality >100 - impaired renal concentration • siADH, hypothyroidism, cortisol deficiency • Check urine sodium & calculate FeNa % • A low urine sodium (<10) and low FeNa (<1%) implies the kidneys are appropriately reabsorbing sodium • A high urine sodium (>20) and high FeNa (>1%) implies the kidneys are not functioning properly

  10. Hyponatremia Flow Sheet

  11. Treatment of Hyponatremia • Be CAUTIOUS with correction: • 0.5 meq/L increase per every hour initially • Do not increase Na more than 10 meq/L in 24 hrs or 18 meq/L in 48 hrs • Treatment varies greatly by etiology of hyponatremia, and it is important to look-up via online or other resources.

  12. Clinical Scenario - Conclusion • 74-year-old man p/w recent gastroenteritis characterized by n/v/d x 5 days, in addition to fatigue and headache. • BMP significant for Na+ of 118, baseline unknown. Serum osmolality is 266. Urine osmolality is 377. • How would you approach this patient’s hyponatremia? The steps: • 1) Serum osmolality – 266, decreased (hypotonic) • 2) Urine osmolality –377, increased (>100) • 3) Volume status - hypovolemic • 4) Urine Na, FeNa – urine Na 8, appropriately reabsorbing, likely volume depleted 2/2 N/V • 5) Treatment: Mild symptoms, correct slowly w/ isotonic saline • How would your approach be different if this patient presented with new-onset seizures? • For symptomatic, severe hyponatremia, more rapid correction using 3% normal saline

  13. TAKE HOME POINTS • Symptoms: Usually Na <125 or rapid decline • N/V, headache, lethargy, AMS, seizures, coma • WORK-UP in 3 important steps (V-O-U): • 1) Assess volume status • 2) Assess serum osmolality • 3) Check urine sodium, osmolarity, & calculate FeNa • Treatment varies by etiology, but cautious correction of sodium important to prevent demyelination as fluid leaves the brain

More Related