A 42-year-old woman with severe asthma is undergoing emergency appendicectomy under general anesthesia. Five minutes after induction with thiopental and intubation, the SpO₂ drops from 98% to 82%, peak airway pressure rises to 45 cm H₂O, and the patient develops diffuse wheezing. Blood pressure remains 110/70 mmHg. What is the most appropriate immediate next step?

Explanation

## Clinical Presentation The patient has acute **intraoperative bronchospasm** triggered by thiopental (a known histamine releaser) in a patient with severe asthma. Key features: - Acute hypoxemia (SpO₂ 82%) - Elevated peak airway pressure (45 cm H₂O) — indicates airway obstruction - Diffuse wheezing — confirms bronchospasm - Stable blood pressure — rules out anaphylaxis or sepsis ## Differential Diagnosis of Intraoperative Hypoxia + Wheezing | Diagnosis | Key Finding | Management | |-----------|-------------|------------| | **Bronchospasm** | Wheezing, ↑ PIP, normal BP | O₂, hand-ventilate, β₂-agonist, magnesium | | Anaphylaxis | Wheezing + hypotension + rash/angioedema | Epinephrine IM/IV 0.3–0.5 mg | | Aspiration | Wheezing + sudden onset, frothy secretions | Suction, PEEP, supportive care | | Tension pneumothorax | Unilateral breath sounds, hypotension, tracheal deviation | Emergency needle decompression | | Pulmonary edema | Bilateral crackles, pink frothy sputum | Diuretics, PEEP, treat cause | ## Rationale for Correct Answer **Key Point:** Intraoperative bronchospasm is a **medical emergency** requiring immediate pharmacological intervention to prevent severe hypoxemia and cardiovascular collapse. ### Step-by-Step Management: 1. **100% Oxygen** — increases alveolar oxygen tension and compensates for ventilation-perfusion mismatch from airway obstruction. 2. **Hand-ventilation with LOW tidal volumes** — mechanical ventilation at high pressures worsens air trapping and barotrauma. Gentle hand-ventilation allows time for exhalation and reduces peak airway pressure. 3. **IV Salbutamol 5 mg** — β₂-agonist causes bronchial smooth muscle relaxation. IV route is faster than nebulized in acute crisis. - Alternative: Salbutamol 100 μg IV bolus repeated every 5–10 minutes. 4. **IV Magnesium Sulfate 2 g** — acts as a smooth muscle relaxant; synergizes with β₂-agonists. Particularly effective in asthma. - Infuse over 10–20 minutes. **High-Yield:** Thiopental is a **histamine releaser** and is contraindicated in asthmatic patients. Propofol or etomidate are safer induction agents. **Mnemonic for Bronchospasm Management: "SALVO"** - **S**albutamol (IV or nebulized) - **A**void triggering agents (histamine-releasing drugs) - **L**ow tidal volumes, hand-ventilate - **V**entilate gently (allow exhalation time) - **O**xygen 100% **Clinical Pearl:** Peak airway pressure >40 cm H₂O in a patient with wheezing indicates severe airway obstruction. Increasing tidal volumes or respiratory rate will worsen air trapping and hypoxemia — the opposite of what you might do for simple hypoventilation.