How is syndrome of inappropriate antidiuretic hormone secretion (SIADH) diagnosed in Haemophilus influenzae type b (Hib) meningitis?

Updated: Jul 09, 2018
  • Author: Prateek Lohia, MD, MHA; Chief Editor: Niranjan N Singh, MBBS, MD, DM, FAHS, FAANEM  more...
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Answer

Diagnostic criteria for SIADH are as follows:

  • Serum sodium less than 135 mEq/L

  • Serum osmolality less than 270 mOsm/L

  • Urine osmolality greater than twice serum osmolality

  • Urine sodium greater than 30 mEq/L

  • No evidence of confounding hypovolemia or dehydration

In some instances, low serum sodium is due to cerebral salt wasting rather than SIADH. Unlike SIADH, cerebral salt wasting is associated with a decline rather than an increase in patient mass. In other instances, hyponatremia is produced by the excessive intravenous administration of hyposmolar fluids.


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