Common ICU approach

• 20% solution: 3 mL nebulized every 4-6 hours, or
• 10% solution: 6 mL nebulized every 4-6 hours

For a mechanically ventilated patient

• Deliver through an in-line nebulizer in the ventilator circuit, per ventilator and respiratory-therapy protocol.
• Give a bronchodilator first or concurrently, such as salbutamol/albuterol, especially in asthma, COPD, or previous wheeze.
• Ensure adequate humidification, chest physiotherapy/positioning when appropriate, and suction after treatment. NAC can rapidly liquefy a large secretion burden, which may transiently worsen airway obstruction if clearance is inadequate.
• Monitor peak pressures, wheeze, oxygenation, heart rate, and tolerance during and after delivery.

Important cautions

• Bronchospasm is the main concern. Stop the nebulization and treat promptly with bronchodilator if wheeze, rising airway pressure, desaturation, or bronchospasm develops.
• Avoid or use only with close supervision in active severe bronchospasm/status asthmaticus.
• It has a strong sulfur/"rotten egg" odor and can cause cough, nausea, rhinorrhea, and airway irritation.
• Do not confuse inhaled NAC with the IV NAC regimen used for acetaminophen poisoning. They are different products and dosing strategies.
• NAC should not delay bronchoscopy when there is suspected major mucus plugging, lobar collapse, or an obstructed endotracheal tube.

Current position

Why routine NAC is not recommended

• Routine NAC plus salbutamol every 6 hours, versus
• On-demand NAC or salbutamol only when clinically indicated

Suggested ICU policy

1. No standing, preventive NAC nebulization for intubated patients.
2. Use only after clinical assessment, for example:
   • thick, adherent airway secretions impairing suctioning
   • recurrent mucus plugging or secretion-related atelectasis
   • inadequate secretion clearance despite adequate humidification and suction
3. Do not use NAC as treatment for ARDS, VAP prevention, or routine COPD secretion management in the ICU.
4. Give through the ventilator circuit according to local respiratory-therapy and pharmacy procedure.
5. Ensure ability to clear loosened secretions with suctioning. Escalate to bronchoscopy when there is lobar collapse, suspected endotracheal-tube obstruction, or persistent mucus plugging.
6. Monitor for bronchospasm, wheeze, rising peak airway pressures, desaturation, and intolerance. NAC may provoke bronchospasm, especially in asthma or COPD. A bronchodilator may be used if bronchospasm occurs, but should not automatically justify routine combined nebulization.

Important exception: smoke inhalation injury

Bottom line

Nebulized NAC should be PRN, not routine.
Reserve it for selected patients with problematic, viscous secretions after basic airway-clearance measures are optimized. Do not expect proven improvements in ventilator duration, mortality, or prevention of VAP.

When to consider it

• Tenacious secretions difficult to clear by suction
• Suspected mucus plugging or secretion-related atelectasis
• Selected smoke-inhalation injury protocols, usually alongside bronchodilator and sometimes nebulized heparin

Not for routine use

Typical regimen

• NAC 20%: 3 mL via nebulizer every 4-6 hours as needed, or
• NAC 10%: 6 mL every 4-6 hours as needed

Safety and monitoring

• Bronchospasm/wheeze is the key adverse effect. Stop if wheeze, desaturation, or rising airway pressures occur.
• Consider salbutamol/albuterol before or with NAC for patients with reactive airways, but avoid making the bronchodilator combination routine unless indicated.
• Ensure effective humidification and suctioning after administration. Liquefied secretions can briefly increase airway obstruction if not cleared.
• If there is persistent lobar collapse, severe plugging, or concern for endotracheal-tube obstruction, assess for bronchoscopy rather than repeatedly nebulizing NAC.