Intraoperative bronchospasm

Why examiners ask this

High airway pressure with wheeze is a classic intraoperative event, and the examiner wants to know if I treat bronchospasm only after excluding the mechanical problems that mimic it. It tests organization (differential while treating) and application of knowledge about bronchodilator delivery through a tube, and it often turns into anaphylaxis.

The 60-second answer

Decision points and the "why"

• Exclude the mimics — kinked tube, mainstem or esophageal intubation, secretions, cuff herniation and the circuit cause high pressure without bronchoconstriction;² a suction catheter that will not pass tells me the tube is obstructed, not the bronchi.
• Deepen first — airway stimulation under light anesthesia causes most bronchospasm; propofol 0.5–1 mg/kg acts in seconds, and sevoflurane works if I can still ventilate.
• Albuterol by inline adapter — the first-line drug,² 8–12 puffs repeated, because only a small fraction reaches the lungs through the tube; I time actuation with inspiration.
• Epinephrine — 10–100 mcg slow IV and escalate, or 0.5 mg IM;² it is the most effective bronchodilator and the drug for anaphylaxis, so I move to it early when the pressure falls.
• Ventilation pattern — a low rate and long expiratory time, accept high peak pressure if plateau pressure is acceptable, and permit hypercapnia;² I watch for auto-PEEP because trapping causes hypotension.
• Adjuncts — ketamine in small boluses (about 20 mg in an adult) or 1–3 mg/kg/h, magnesium 50 mg/kg to 2 g IV over 20 minutes, IV salbutamol 250 mcg slowly, and hydrocortisone 200 mg, knowing steroids take hours.²
• Who is at risk — recent URI, active wheeze, poorly controlled asthma, heavy smoking and instrumentation under light anesthesia; in these patients I pretreat with albuterol, induce with propofol or ketamine, and choose a supraglottic airway when the surgery allows, because prevention is easier than rescue.
• Plateau versus peak — a high peak with a normal plateau points to airway resistance, which fits bronchospasm or an obstructed tube; a high plateau points to reduced compliance, which fits pneumothorax, edema, mainstem intubation or abdominal pressure.
• Extubation — I extubate deep or with lidocaine to avoid reflex bronchospasm, and only after the wheeze has resolved.

The complication they will inject

Five minutes after the antibiotic, the patient has a peak pressure of 45 cmH2O, an SpO2 of 88%, a blood pressure of 65/30 and an erythematous chest. This is anaphylaxis with bronchospasm, not simple reactive airway. I call for help, stop the suspected drug, give epinephrine 50 mcg IV and repeat, starting an infusion after about three boluses,³ give fluid rapidly, and go to 100% oxygen. I tell the surgeon to finish quickly. Antihistamines and steroids are no longer part of acute treatment, only for refractory or ongoing symptoms.³ I send tryptase once the patient is stable, again at 1–2 hours and after 24 hours, and refer for allergy testing.³ If epinephrine fails, I add vasopressin 1–2 units, and glucagon 1–2 mg IV every 5 minutes if the patient takes a beta-blocker.¹

Pitfalls that cost points

• Treating with albuterol before excluding a kinked tube or mainstem intubation.
• Giving only two puffs of albuterol through the tube.
• Withholding epinephrine in a hypotensive bronchospastic patient.
• Hyperventilating and causing auto-PEEP.
• Forgetting anaphylaxis, aspiration and tension pneumothorax in the differential.

Rapid-why

Q: Why does the capnograph look like a shark fin? A: Uneven emptying of obstructed alveoli prolongs the expiratory upstroke; the plateau slopes and does not flatten.

Q: Why is desflurane avoided? A: It is pungent and irritant to the airway, increasing resistance, especially in smokers and at high concentrations; isoflurane is also best avoided.²

Q: Why does a beta-blocked patient need glucagon? A: Glucagon raises cyclic AMP independent of beta receptors, so it works when epinephrine is blunted.

Q: When do you use heliox or ECMO? A: Heliox lowers turbulent resistance in refractory cases but limits FiO2; ECMO is the rescue for life-threatening, refractory bronchospasm.

Numbers to know

Links

• COPD and reactive airway disease, anaphylaxis, aspiration, Pneumothorax and tension pneumothorax, laryngospasm
• Atlas: Capnography: waveforms and sudden loss of ETCO2; Monitor atlas: perioperative respiratory events
• GINA Global Strategy for Asthma Management and Prevention