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Difficulty: MediumPhysiological Adaptation

A client admitted with severe lobar pneumonia is receiving targeted intravenous antibiotic therapy. During hourly rounds, the nurse observes that the client has become increasingly agitated and diaphoretic. Current vital signs include a temperature of 39.2∘C39.2^\circ\text{C} (102.6∘F102.6^\circ\text{F}), a heart rate of 126126 beats per minute, a respiratory rate of 3030 breaths per minute, and a blood pressure of 94/68 mm Hg94/68\text{ mm Hg}.

An arterial blood gas (ABG) analysis is drawn and reveals the following results:

ParameterResult
pH\text{pH}7.287.28
PaCO2\text{PaCO}_231 mm Hg31\text{ mm Hg}
HCO3−\text{HCO}_3^-14 mEq/L14\text{ mEq/L}

Based on these assessment findings, which physiological alteration is the client most likely experiencing?

  1. Systemic tissue hypoperfusion resulting in metabolic acidosisAnswer
  2. B
    Uncompensated respiratory alkalosis caused by infection-induced tachypnea
  3. C
    Primary respiratory acidosis developing from respiratory muscle fatigue
  4. D
    Expected hyperdynamic cardiovascular response to the elevated core temperature

Answer

The correct answer is systemic tissue hypoperfusion resulting in metabolic acidosis. This is evidenced by the client's progression to early septic shock, characterized by agitation, tachycardia, borderline hypotension, and an ABG confirming a primary metabolic acidosis.
The correct answer identifies that the client is experiencing systemic tissue hypoperfusion resulting in a metabolic acidosis. The client's presentation of a severe infection combined with new-onset agitation, tachycardia, and a blood pressure of 94/68 mm Hg are classic indicators of early septic shock. As tissues become deprived of oxygen, they shift to anaerobic metabolism, which rapidly produces lactic acid. This accumulation of lactic acid consumes bicarbonate buffers, causing the primary metabolic acidosis seen on the ABG (pH 7.28, HCO3- 14 mEq/L).

Step-by-Step Solution

1
Analyze the arterial blood gas (ABG) results to determine the primary acid-base imbalance.
The pH of 7.28 indicates acidemia. The low HCO3- (14 mEq/L) matches the acidic pH, confirming a primary metabolic acidosis. The PaCO2 (31 mm Hg) is low, indicating a partial respiratory compensation.
Accurate ABG interpretation is the first step in diagnosing the client's internal physiological state.
2
Evaluate the current vital signs and clinical presentation for signs of physiological deterioration.
The client is tachycardic (126 bpm), tachypneic (30 breaths/min), hypotensive relative to normal parameters (94/68 mm Hg), and exhibiting an altered mental status (agitation).
Vital sign trends provide critical information about systemic tissue perfusion and end-organ function.
3
Synthesize the laboratory data and clinical findings to identify the underlying pathophysiological process.
The combination of an active infection (pneumonia), signs of poor systemic perfusion, and a metabolic acidosis points directly to lactic acid accumulation from anaerobic metabolism, indicating early septic shock.
Connecting lab values with physical assessment findings enables the nurse to anticipate the correct medical emergency and prioritize life-saving care.

Key Concept

Septic shock presents with signs of systemic hypoperfusion (hypotension, altered mental status, tachycardia), which forces cells into anaerobic metabolism, leading to lactic acid production and a subsequent metabolic acidosis.
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Topics

Physiological Adaptation

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