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Renal - Hyponatremia
ACP Nephrology p11
Question | Answer |
---|---|
Formula for total osmolality | 2 x Serum sodium + plasma glucose / 18 + BUN / 2.8 |
Does urea exert an osmotic effect? | No because it is freely diffusible across most cell membranes |
What is normal osmolality | 280-285 (or 275 - 295) |
What is the function of ADH? | Promotes water reabsorption in the distal tubule and collecting duct of the kidney (causes fluid retention). Also has a peripheral vasoconstriction effect. |
Serum sodium under which a patient is considered to have hyponatremia | 135 |
First step in assessing hyponatremia | Serum sodium less than or equal to 135 |
Second step in assessing hyponatremia | Is the patient symptomatic? |
What are mild symptoms of hyponatremia? | Headache, lethargy, dizziness |
What are symptoms of severe hyponatremia? | confusion, ataxia, seizures, obtundation, coma, respiratory depression |
If a patient with hyponatremia is asymptomatic or has mild symptoms, then what is the next step? | Assess serum osmolality. Hypotonic hyponatremia is osmolality < 280. Isotonic hyponatremia is osmolality 280-285. Hypertonic hyponatremia's osmolality > 285. |
What is the differential for isotonic hyponatremia? | Hyperproteinemia or hyperlipidemia |
What is the differential for hypertonic hyponatremia? | Hyperglycemia, mannitol, sorbitol, contrast |