What are the guidelines for using nebulized lidocaine (local anesthetic) for awake intubation in patients with varying medical histories, including those with cardiac or respiratory disease?

Nebulized Lidocaine for Awake Intubation

Nebulized lidocaine is an effective and safe topical anesthetic for awake intubation when used at doses not exceeding 9 mg/kg lean body weight, with onset in 5 minutes and duration of 30-60 minutes. 1

Dosing and Administration

The maximum total dose of lidocaine from all sources (nebulized, spray, gel) must not exceed 9 mg/kg of lean body weight to prevent systemic toxicity. 1, 2, 3

Practical Dosing Guidelines:

• Lidocaine concentrations of 1-10% can be used for topical airway anesthesia 1
• 1 ml of 1% lidocaine = 10 mg; 1 spray of 10% = 10 mg 1
• Onset of action: 5 minutes 1
• Duration of action: 30-60 minutes 1
• Terminal half-life: 1.5-2 hours 1

Administration Technique:

• Nebulized 2% lidocaine (4 ml) can be administered via face mask with patient in anti-Trendelenburg position 4
• Additional topical application with 10% lidocaine spray to base of tongue, nasal cavity, and lower throat may be combined with nebulization 4
• Total lidocaine dose from all routes must be calculated to stay within the 9 mg/kg limit 1, 2

Contraindications and High-Risk Populations

Absolute Contraindications:

• Patients weighing less than 40 kg 2
• Active cardiac disease 2
• Electrolyte disturbances 2
• Seizure disorders 2
• Renal or hepatic insufficiency 2
• Pregnancy/lactation 2
• Neurological disorders 2

Special Precautions:

• In patients with deep neck infections, pharyngolaryngeal hyperemia, or edema, reduce the total dose or concentration significantly as transmucosal absorption is enhanced 5
• Elderly, debilitated, or acutely ill patients require reduced doses 6
• Patients with severe hepatic disease cannot metabolize lidocaine normally and are at higher risk for toxic plasma concentrations 6
• Patients with cardiovascular compromise may be less able to compensate for A-V conduction prolongation 6
• Older patients and those with cardiac disease require particular caution with any local anesthetic 1

Toxicity Recognition and Management

Plasma Concentration-Related Toxicity:

• 5-10 μg/ml: Dizziness, tinnitus, tongue/lip numbness 2
• 10-15 μg/ml: Myocardial depression 2
• 15-25 μg/ml: Seizures, cardiac arrhythmias 2
• >25 μg/ml: Ventricular arrest 2

Early Warning Signs:

Restlessness, anxiety, tinnitus, dizziness, blurred vision, tremors, depression, or drowsiness may be early signs of CNS toxicity and require immediate intervention. 6

Emergency Management:

• Maintain patent airway and provide assisted/controlled ventilation with oxygen immediately 6
• For persistent seizures: small increments of ultra-short acting barbiturate (thiopental) or benzodiazepine (diazepam) IV 6
• Circulatory support with IV fluids and vasopressors (e.g., ephedrine) as needed 6
• Standard cardiopulmonary resuscitation if cardiac arrest occurs 6
• Resuscitative equipment, oxygen, and emergency drugs must be immediately available 6

Monitoring Requirements

Continuous ECG and pulse oximetry monitoring with regular non-invasive blood pressure measurements during initial administration and for at least 15 minutes after completion. 2, 3

Adjunctive Medications

Antisialagogue Premedication:

• Glycopyrronium bromide 0.2-0.4 mg IM or 0.1-0.2 mg IV administered 30-60 minutes pre-procedure 1
• This reduces secretions that can interfere with topical anesthetic effectiveness and visualization 1

Sedation (if needed):

• Midazolam 0.5-1 mg IV bolus, titrated to effect with peak effect at 5-10 minutes 1
• Fentanyl 0.5-1 μg/kg IV bolus 1
• Minimal sedation is recommended to maintain patient cooperation and spontaneous ventilation 4

Clinical Efficacy and Safety Data

Despite large topical lidocaine doses (mean 5.3 mg/kg), mean peak arterial plasma concentrations remain low (0.6 μg/ml), well below toxic levels. 7

Awake intubation with nebulized lidocaine produces no significant elevation in blood pressure or heart rate during topical application or after intubation. 7

The method is well-tolerated with minimal patient discomfort when properly administered, and is rarely associated with serious desaturation episodes. 7, 4

Important Caveats

• Do not administer simultaneous nerve blocks or infiltrate surgical sites when using nebulized lidocaine—calculate total lidocaine dose from all sources 2
• Wait at least 4 hours after completing any IV lidocaine infusion before performing nerve blocks 2
• Conditions such as hypercarbia, dysphagia, or hepatic disease facilitate lidocaine toxicity at lower serum concentrations than normal 5
• In the presence of mucosal inflammation or infection, either reduce total dose or concentration significantly 5