A client passes 3.5 liters of urine a day. Plasma osmolality is 305 mOsm/kg, urine osmolality is 150 mOsm/kg, urine specific gravity is 1.000, and plasma ADH is raised. What is the priority intervention?

1. A

   Give desmopressin

2. B

   Start fluid replacement

3. C

   Restrict fluids and monitor serum sodium closely

4. D

   Give 3 percent hypertonic saline

Appeared in: NORCET-11 Mains

Explanation

• The patient's signs and lab values are classic for Nephrogenic Diabetes Insipidus (NDI), where the kidneys fail to respond to ADH.
• This lack of response leads to massive excretion of dilute urine, causing significant free water loss.
• The resulting dehydration is indicated by the high plasma osmolality (305 mOsm/kg).
• The most immediate life-threatening risk is severe dehydration and hypovolemic shock.
• Therefore, the priority nursing intervention is to start fluid replacement to restore intravascular volume and prevent circulatory collapse.

Why Other Options Were Wrong

• Option A: Desmopressin is a synthetic form of ADH. It is ineffective in NDI because the core problem is the kidneys' resistance to ADH, not a deficiency of the hormone.
• Option C: Restricting fluids in a patient who is already severely dehydrated from massive urine output is dangerous and would rapidly worsen the hypernatremia and dehydration, potentially leading to seizures, coma, or death.
• Option D: Hypertonic saline (3%) is used to treat severe, symptomatic hyponatremia (low sodium). This patient has hypernatremia (high sodium) due to free water loss. Administering hypertonic saline would dangerously elevate the serum sodium further.

Related Visual

Clinical Relevance

• Nursing practice connection: Use the key finding related to Management of Nephrogenic Diabetes Insipidus to guide bedside assessment, documentation, and the next nursing action.
• A nurse's priority for a patient with suspected Diabetes Insipidus is the strict monitoring of fluid intake and output, daily weights, and vital signs to assess for dehydration and hypovolemic shock.
• Closely monitor serum sodium levels. Rapid changes in sodium can cause serious neurological complications like cerebral edema or osmotic demyelination.
• Patient education is vital, focusing on the importance of maintaining adequate fluid intake to match urine output.

How to Approach the Question

• First, analyze the patient's primary symptoms and lab values. Note the polyuria (3.5 L/day).
• Compare the plasma osmolality to the urine osmolality. High plasma osmolality (305) with low urine osmolality (150) indicates the kidneys are inappropriately losing free water despite the body being dehydrated. This points towards Diabetes Insipidus (DI).
• Next, use the ADH level to determine the type of DI. The problem states ADH is 'raised'. This means the pituitary is working correctly, but the kidneys are not responding. This confirms Nephrogenic DI.
• Identify the core physiological problem: massive water loss leading to dehydration.
• Based on this problem, evaluate the options. The most logical and immediate priority is to replace the lost water to correct the dehydration. Therefore, starting fluid replacement is the correct answer.

Concept Tested & Keywords

• Concept Tested: Management of Nephrogenic Diabetes Insipidus
• Stem keywords: polyuria, plasma osmolality, urine osmolality, urine specific gravity, raised plasma ADH
• Lead-in keywords: priority intervention
• Clinical cues: The combination of high plasma osmolality (dehydration) and low urine osmolality (inability to concentrate urine) is a key indicator of Diabetes Insipidus.
• Clinical cues: The elevated ADH level is the critical clue that differentiates Nephrogenic DI from Central DI.

Question ID

Q4kWiTZ4VW2tUPBBgnZYZX

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Reference Book

E6 Ghai Essential Pediatrics(pp 26-904 of 913) p. 524-526

E6 Nursing Brunner Adult Health 3SA Vol 1 Part 4 p. 11-13

E6 Medicine Harrison 22e Part 1 p. 394-396