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Difficulty: MediumPulmonary and Critical Care

A 76-year-old man who resides in an assisted living facility is evaluated in the emergency department for altered mental status. Facility staff report that he had a productive cough and low-grade fever over the preceding three days. His medical history includes essential hypertension, diet-controlled type 2 diabetes mellitus, and osteoarthritis. Upon arrival, his temperature is 38.8°C (101.8°F), blood pressure is 78/46 mm Hg, pulse is 122/min, and respirations are 26/min. Pulse oximetry shows 91% on a 2 L/min nasal cannula. Physical examination reveals a lethargic man who arouses to tactile stimuli. Mucous membranes are dry. Auscultation of the chest reveals bronchial breath sounds and egophony over the right lower lung field. The jugular venous pressure is flat. Heart sounds are rapid but regular, with no murmurs. Arterial blood gas analysis on the current oxygen setting shows:

- pH: 7.29
- PaCO2: 25 mm Hg
- PaO2: 68 mm Hg
- HCO3-: 12 mEq/L

Serum lactate is 4.8 mmol/L. Peripheral venous access is obtained. Blood and sputum cultures are drawn, and empiric intravenous antibiotics (ceftriaxone and azithromycin) are initiated. An infusion of 3 L of normal saline is administered over 60 minutes. Reassessment reveals a blood pressure of 80/48 mm Hg and a pulse of 118/min. Urine output has been 10 mL over the past hour. Which of the following is the most appropriate next step in the management of this patient?

  1. A
    Administer an intravenous bolus of furosemide
  2. Initiate a continuous intravenous infusion of norepinephrineAnswer
  3. C
    Perform endotracheal intubation and initiate mechanical ventilation
  4. D
    Broaden the antibiotic regimen to piperacillin-tazobactam and vancomycin
  5. E
    Administer an intravenous bolus of sodium bicarbonate

Answer

Initiate a continuous intravenous infusion of norepinephrine
This patient is experiencing septic shock secondary to community-acquired pneumonia. He has remained hypotensive with a mean arterial pressure (MAP) around 58 mm Hg despite an adequate initial fluid challenge of 3 L of crystalloid (which exceeds the recommended 30 mL/kg for a typical adult). When septic shock is fluid-refractory, the immediate next step is the initiation of a vasopressor to restore adequate tissue perfusion (target MAP ≥\ge 65 mm Hg). Norepinephrine is the first-line vasoactive agent due to its strong α1\alpha_1-adrenergic effects (increasing systemic vascular resistance) and modest β1\beta_1-adrenergic effects (helping maintain cardiac output without causing excessive tachycardia).

Step-by-Step Solution

1
Identify the primary clinical presentation.
The patient has septic shock secondary to a right lower lobe pneumonia, evidenced by fever, consolidation, elevated lactate, and profound hypotension.
Establishing the etiology of shock dictates the resuscitation algorithm.
2
Evaluate the response to initial fluid resuscitation.
After receiving 3 L of normal saline (a sufficient initial crystalloid bolus of at least 30 mL/kg), the patient's mean arterial pressure (MAP) remains approximately 58 mm Hg.
A MAP below 65 mm Hg after adequate fluid challenge defines fluid-refractory septic shock.
3
Assess the arterial blood gas to rule out impending respiratory failure requiring airway intervention.
Using Winter's formula, the expected PaCO2 is 26 +/- 2 mm Hg. The measured PaCO2 is 25 mm Hg, indicating perfect respiratory compensation.
Misinterpreting the low PaCO2 as primary respiratory failure could lead to catastrophic unnecessary intubation.
4
Determine the next best pharmacological intervention.
Norepinephrine infusion is selected as the first-line vasoactive agent.
Guidelines mandate starting vasopressors when fluid resuscitation fails to restore a MAP of at least 65 mm Hg.

Key Concept

Management of fluid-refractory septic shock requires the prompt initiation of vasopressors, with norepinephrine being the first-line agent, to maintain a mean arterial pressure of at least 65 mm Hg.
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Topics

Pulmonary and Critical Care

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