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Difficulty: MediumPhysiological Adaptation

A nurse is assessing a client who is two days postoperative following a right total knee arthroplasty. The client suddenly becomes severely restless and reports sharp, pleuritic chest pain. Which of the following assessment findings would indicate that the client has developed a pulmonary embolism complicated by obstructive shock? Select all that apply.

  1. Arterial blood gas showing a pH of 7.51, PaCO2 of 28 mm Hg, and PaO2 of 56 mm HgAnswer
  2. Blood pressure decreasing from a baseline of 128/82 mm Hg to 84/50 mm HgAnswer
  3. Heart rate of 132 beats per minute accompanied by a weak, thready pulseAnswer
  4. D
    Arterial blood gas showing a pH of 7.26, PaCO2 of 58 mm Hg, and HCO3 of 24 mEq/L
  5. E
    Widening of the pulse pressure with warm, flushed extremities

Answer

The assessment findings indicating a pulmonary embolism with obstructive shock are the arterial blood gas showing respiratory alkalosis and hypoxemia, the significant drop in blood pressure, and the tachycardia with a weak, thready pulse.
A massive pulmonary embolism creates an acute obstruction in the pulmonary vasculature, severely limiting blood flow to the left side of the heart. This precipitous drop in left ventricular preload and cardiac output defines obstructive shock, which presents with profound hypotension, compensatory tachycardia, and a weak, thready pulse due to decreased stroke volume and peripheral vasoconstriction. Concurrently, the obstruction creates a severe ventilation-perfusion mismatch, resulting in hypoxemia. The body's natural response to this hypoxia, along with severe pain and anxiety, is hyperventilation, which drives down carbon dioxide levels and causes respiratory alkalosis.

Step-by-Step Solution

1
Analyze the clinical scenario and the client's risk factors.
The client is postoperative from major orthopedic surgery, which is a high risk factor for deep vein thrombosis and subsequent pulmonary embolism (PE). The sudden onset of pleuritic chest pain and restlessness strongly suggests an acute PE.
Identifying the primary pathophysiological event is essential to anticipate the resulting hemodynamic and respiratory changes.
2
Evaluate the respiratory parameters and arterial blood gas (ABG) findings.
A PE blocks pulmonary blood flow, causing a ventilation-perfusion mismatch and leading to hypoxia (low PaO2). The client hyperventilates in response, exhaling excess carbon dioxide and causing respiratory alkalosis (high pH, low PaCO2).
Understanding the acid-base imbalance helps distinguish between different types of respiratory distress.
3
Evaluate the hemodynamic parameters for signs of obstructive shock.
A massive PE creates a physical obstruction that severely reduces left ventricular filling and cardiac output. This manifests as significant hypotension and a compensatory tachycardia. Due to intense peripheral vasoconstriction and low stroke volume, the pulse becomes weak and thready, and the pulse pressure narrows.
Differentiating the types of shock ensures accurate assessment. Findings of widened pulse pressure or warm extremities would indicate distributive shock, not obstructive shock.

Key Concept

Clinical Manifestations of Pulmonary Embolism and Obstructive Shock
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Topics

Physiological Adaptation

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