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Difficulty: Very hardPhysiological Adaptation

A client is receiving care in the neuroscience unit on the second day following surgical clipping of a ruptured cerebral aneurysm. Assessment reveals increasing lethargy, a heart rate of 118 beats/min, a blood pressure of 88/54 mm Hg, and a central venous pressure (CVP) of 2 mm Hg. Laboratory results show a serum sodium of 122 mEq/L, serum osmolality of 258 mOsm/kg, and a urine sodium of 150 mEq/L. Which of the following is the priority nursing action?

  1. Start a prescribed continuous infusion of 0.9% sodium chloride.Answer
  2. B
    Implement a strict fluid restriction of 800 mL per day.
  3. C
    Prepare to give a prescribed dose of intravenous mannitol.
  4. D
    Obtain an arterial blood gas sample to assess for respiratory alkalosis.

Answer

The priority action is to start a prescribed continuous infusion of 0.9% sodium chloride to restore intravascular volume.
The client is exhibiting classic signs of Cerebral Salt Wasting (CSW) syndrome, a complication of subarachnoid hemorrhage. CSW is characterized by hyponatremia, high urine sodium, and profound hypovolemia (evidenced by hypotension, tachycardia, and a low CVP). The absolute priority is to restore intravascular volume with isotonic fluids (such as 0.9% sodium chloride) to maintain adequate cerebral perfusion pressure and prevent circulatory collapse.

Step-by-Step Solution

1
Analyze the client's vital signs and hemodynamic parameters.
A heart rate of 118 beats/min, blood pressure of 88/54 mm Hg, and CVP of 2 mm Hg indicate severe hypovolemia.
Identifying the client's perfusion status is critical for recognizing early signs of impending shock.
2
Correlate the hemodynamics with the laboratory findings.
The presence of hyponatremia (122 mEq/L) and high urine sodium (150 mEq/L) alongside hypovolemia points to Cerebral Salt Wasting (CSW) rather than Syndrome of Inappropriate Antidiuretic Hormone (SIADH).
CSW and SIADH both present with hyponatremia, but CSW causes hypovolemia due to renal salt loss, whereas SIADH causes euvolemia or hypervolemia.
3
Determine the most critical nursing intervention.
Isotonic fluid replacement (0.9% sodium chloride) is required immediately.
Addressing the profound intravascular volume deficit is the highest priority to maintain cerebral perfusion pressure and prevent hypovolemic shock following a subarachnoid hemorrhage.

Key Concept

Differentiating Cerebral Salt Wasting (CSW) from SIADH using hemodynamic indicators and prioritizing volume resuscitation.
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Topics

Physiological Adaptation

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