Water Deprivation Test:

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This test is dangerous for patient which clinically dehydrated.

· Test can be conducted if plasma osmolality is less than 295 mOsmol/kg.

 

At 10.00pm weigh the patient, collect plasma and urine sample for Osmolality and Sodium.

· No water intake is allowed until test is terminated.

· Care should be taking to ensure that body weighed doses not decrease by more than 5%.

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At 6.00am, the patient is weighed again. All urine passed out hourly is collected for measurement of volume and osmolality.

 

When (i) urine osmolality is stable (a change of <= 30mOsmol/kg for 2 consecutive hours-usually takes 8-12 hours to occur)

(ii) or patient lost>=3kg in body weight

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Specimens are collected for plasma osmolality and sodium level.

· 5 unit of aqueous vasopressin (ADH) is given subcutaneously.

· Collect urine for osmolality one hour after injection.

· List of samples as follow: