Difficulty: Intermediate | Prerequisites: Part 1 (Anatomy and Foundations), basic pharmacology of local anaesthetics and IV agents.
This second set of notes covers the pharmacological and procedural toolkit for ENT anaesthesia. It picks up where Part 1 (anatomy, shared airway, positioning, specialised tubes) left off and walks through topical local anaesthetics, vasoactive and antiemetic agents, deliberate controlled hypotension, laser surgery and fire safety, endoscopy, jet ventilation, THRIVE, and the management of foreign-body aspiration. Part 3 covers procedure-specific anaesthesia (middle ear, tonsillectomy, thyroid, cleft palate, trauma, radical neck dissection).
ENT pharmacology centres on topical local anaesthetics (cocaine is unique for its built-in vasoconstriction), careful epinephrine dosing, glycopyrrolate as the preferred antisialagogue, and multimodal PONV prophylaxis. Controlled hypotension, laser safety (the fire triad of O₂ + fuel + ignition), jet ventilation, and THRIVE are procedure-enabling techniques you are expected to know for exams.
Cocaine (topical, 4% solution)
The only local anaesthetic with intrinsic vasoconstriction. It blocks norepinephrine and epinephrine reuptake. Maximum dose 3 mg/kg. Duration about 45 minutes. Used in over 50% of rhinolaryngology procedures.
In simple terms, cocaine numbs the tissue and shrinks the blood vessels at the same time, which is why it is so useful in the highly vascular nose.
Methemoglobinaemia
A condition in which haemoglobin is oxidised to a form that cannot carry oxygen effectively. Benzocaine is a well-known cause.
Think of it as haemoglobin that has been chemically locked so it can no longer pick up oxygen.
Glycopyrrolate
An anticholinergic preferred over atropine for ENT work. It produces less tachycardia and does not cross the blood-brain barrier (so no sedation). Useful as an antisialagogue to dry intraoral secretions.
In simple terms, it dries the mouth without speeding up the heart or making the patient drowsy.
Deliberate controlled hypotension
An intentional reduction of mean arterial pressure (MAP) toward autoregulation limits to reduce surgical bleeding. The recommended floor is MAP no lower than 50 to 60 mmHg, or no more than 20% below baseline. An arterial line is required.
Think of it as gently turning down the blood pressure dial so the surgeon gets a drier field, while staying above the level that keeps the brain and kidneys safe.
Fire triad (airway fire)
The three elements required for an airway fire: an oxidiser (O₂ or N₂O), a fuel source (ETT, drapes, tissue), and an ignition source (laser, electrosurgery). Removing any one element prevents fire.
In simple terms, oxygen plus something that can burn plus a spark equals fire inside the airway.
High-frequency jet ventilation (HFJV)
A ventilation technique using low tidal volumes at a high rate, delivered through a needle on a high-pressure hose (up to 60 psi). Inspiration is active; expiration is passive. Expiratory adequacy must be assessed constantly.
Think of it as tiny, rapid puffs of air through a narrow jet. The lungs fill a little with each puff, but they must be given time to empty.
THRIVE
Transnasal humidified rapid-insufflation ventilatory exchange. A noninvasive, high-flow (10 to 12 L/min), humidified, warmed nasal cannula technique for passive apnoeic oxygenation. Extends safe apnoea times with a more balanced risk profile than jet ventilation.
In simple terms, warm, moist, high-flow oxygen through the nose that keeps the patient oxygenated even when they are not breathing.
Apnoeic oxygenation
The delivery of oxygen to the lungs during apnoea, relying on the difference between the rate of oxygen absorption into the blood and the rate of CO₂ excretion. Oxygen continues to flow down into the alveoli by mass flow even without ventilation.
Think of it as topping up the oxygen tank while the patient is not breathing, buying time before desaturation.
Amide-based drugs are the most common. Many ENT procedures use topical or local anaesthesia alone, or combined with IV sedation, monitored anaesthesia care, or general anaesthesia. When agents are combined, doses must be carefully calculated to avoid toxicity.
Cocaine (4% solution): 3 mg/kg max. The only local anaesthetic with intrinsic vasoconstriction (blocks catecholamine reuptake). Duration about 45 minutes.
Lidocaine: 4 mg/kg plain, 7 mg/kg with epinephrine. Rapid onset. Suitable for the entire tracheobronchial tree.
Benzocaine: 250 to 300 mg max. Very short duration (about 10 minutes). Can cause methemoglobinaemia.
Bupivacaine: 2.5 mg/kg plain. Slow hepatic clearance, long duration.
Mepivacaine: 300 mg max. Intermediate potency, rapid onset.
Concentrations: 1:200,000 (5 mcg/mL), 1:100,000 (10 mcg/mL), 1:50,000 (20 mcg/mL).
Produces vasoconstriction, reduces systemic absorption, extends the block, and lowers toxicity.
Duration of the block is proportional to how long the drug stays in contact with the nerve.
Epinephrine injected shortly after cocaine produces combined sympathetic stimulation that can reach toxic levels.
Symptoms: headache, hypertension, tachycardia, dysrhythmias.
Rule: omit cocaine in patients with cardiac disease or cardiac risk. Use oxymetazoline instead.
Anticholinergics: routine preoperative use has diminished, but the antisialagogue effect remains useful intraorally. Glycopyrrolate is preferred over atropine (less tachycardia, does not cross the blood-brain barrier, no sedation).
Corticosteroids: decrease laryngeal oedema, reduce nausea and vomiting, and prolong local-anaesthetic analgesia by inhibiting prostaglandins. Give early so the drug peaks before surgery begins. Be aware of immunosuppression (can mask infection and inflammation).
All ENT patients are at risk. Middle-ear surgery has a particularly high incidence.
PONV can delay PACU discharge or force unscheduled admission.
Blood pooling in the posterior oropharynx (e.g. after tonsillectomy) drains into the stomach and is a major trigger. Pack the throat during surgery, ensure packs are removed, and suction before extubation.
Use a multimodal antiemetic approach (combining agents from different classes).
Head and neck tumour dissections can run over 12 hours with major fluid and blood loss. The surgeon may request controlled hypotension to reduce bleeding.
Reduce MAP toward autoregulation limits. Authors' recommended floor: MAP no lower than 50 to 60 mmHg, or no more than 20% below baseline. Chronic hypertensives need a higher floor.
An arterial line is required. Monitor urine output, MAP, cerebral and cardiac perfusion, and arterial blood gases.
Better surgical fields are achieved with beta-blockers, calcium-channel blockers, or remifentanil than with vasodilators alone.
Sodium nitroprusside (1 to 5 mcg/kg/min adults, 6 to 8 in children): potent, rapid on/off, preserves cardiac output. Risks include reflex tachycardia, rebound hypertension, pulmonary shunting, and cyanide toxicity.
Dexmedetomidine (1 mcg/kg loading over 10 min, then 0.2 to 0.7 mcg/kg/hr): dose-dependent sedation and analgesia, lowers anaesthetic requirements, smooth emergence. Risks include bradycardia, hypotension (especially with bolus), and heart block.
Esmolol (200 mcg/kg/min): particularly useful for controlling tachycardia. Risk of significant cardiac depression.
Nitroglycerin (125 to 500 mcg/kg/min in adults): preserves myocardial blood flow, reduces preload, preserves tissue oxygenation. Risks include raised intracranial pressure and highly variable dosing.
Nicardipine (5 mcg/kg/min): calcium-channel blocker that preserves cerebral blood flow.
Remifentanil plus propofol: remifentanil reduces middle-ear blood flow (dry field for tympanoplasty); propofol reduces PONV. Downside: no analgesia once remifentanil stops, and potential secondary hyperalgesia.
Monochromatic (one wavelength), coherent (same phase and direction), collimated (parallel beam).
CO₂ laser: long wavelength absorbed almost entirely by surface water. Vaporises cellular water, producing a shallow burn with extreme precision. Favoured around the larynx. A helium-neon low-energy laser is used to aim it.
Nd:YAG laser (neodymium-doped yttrium-aluminum-garnet): shorter wavelength, less water absorption, deeper penetration. Passes through the cornea, so green-lensed goggles are mandatory for everyone in the room.
Ho:YAG laser (holmium): pulsed infrared at 2.1 mm, excellent water absorption. Used for nasal surgery and tonsillectomy.
CO₂: any clear glass or plastic wraparound.
Nd:YAG: green goggles.
KTP (potassium titanyl-phosphate): orange-red goggles.
Argon: orange goggles.
Smoke and vapour from laser use are potentially toxic and may transmit viral particles (low but real risk). Use smoke evacuators.
Uncommon (about 0.4%), typically caused by the laser penetrating the ETT in an oxygen-rich field.
N₂O supports combustion.
Positive-pressure ventilation during combustion creates a blowtorch effect.
Post "WARNING: LASER IN USE" signs. Protect eyes. Use matte-finish (black) instruments to reduce reflection.
Keep delivered O₂ as low as possible (no more than 30%). Avoid N₂O. Place the laser in STANDBY when not firing. Shield adjacent tissue with wet gauze. Suction the plume.
Use a laser-specific ETT. Inflate the cuff with methylene-blue-dyed saline.
When open O₂ exceeds 30%: deliver 5 to 10 L/min air under drapes to wash out O₂; stop supplemental O₂ at least 1 minute before electrosurgery or laser use when possible; use bipolar (not monopolar) for coagulation.
Tonsillectomy: scavenge deep with a metal suction cannula; keep gauze and sponges moist.
Tracheostomy: do not use electrosurgery to incise the trachea.
Bronchoscopy: keep delivered O₂ below 30%.
Includes panendoscopy, laryngoscopy, microlaryngoscopy (with operating microscope), oesophagoscopy, and bronchoscopy. Instruments may be rigid or flexible. A rigid laryngoscope may be suspended from an arch anchored to the chest/abdomen or a Mayo stand.
One of the most common ENT procedures (over 250,000 per year in the US), often linked to recurrent or seasonal allergies causing polyps.
Other indications: hoarseness, stridor, haemoptysis, foreign body, papillomas, trauma, tracheal stenosis, tumours, vocal-cord dysfunction.
Complications: eye trauma, epistaxis, laryngospasm, bronchospasm, excessive plasma levels of local anaesthetic or epinephrine.
Anxiolytics may cause respiratory depression or worsen obstruction in patients with airway pathology. Protect from aspiration. Use an antisialagogue and acid-aspiration prophylaxis if the patient is aspiration-prone.
Awake oral or nasal intubation with minimal sedation plus topical anaesthesia is common. Awake tracheostomy is rare.
Succinylcholine for brief cases.
Intermediate agents (vecuronium, cisatracurium, rocuronium) for procedures lasting 30 minutes or more.
Remifentanil if vocal-cord immobility is needed without relaxants.
At emergence: oropharyngeal suctioning, humidified O₂, watch for laryngospasm, croup, and stridor.
Small cuffed ETT / microlaryngeal tube (MET), size 5.0 to 6.0: the MET cuff is larger than a small standard tube's, giving wider tracheal pressure distribution. Advantages include a secure airway, controlled ventilation, lower-airway protection, end-tidal CO₂ monitoring, and inhalational agent delivery. Disadvantages include extubation and airway-loss risk, laser complications, and field obstruction.
Intermittent apnoea: remove the ETT, operate during brief apnoea, then reintubate. No special equipment needed, but carries risks of reintubation difficulty, desaturation, an unprotected airway, and wide vital-sign swings. Mitigate the sympathetic response with lidocaine, alfentanil, remifentanil, sufentanil, fentanyl, esmolol, or dexmedetomidine.
Setup: a metal needle placed in the operating laryngoscope or passed through the cords. Operated by a manual hand valve or mechanical device. Use the lowest O₂ concentration possible (many patients tolerate FiO₂ of 30% or less).
High-frequency jet ventilation (HFJV): low tidal volume at a high rate. The needle sits on a high-pressure hose (up to 60 psi) that entrains room air. Inspiration is active; expiration is passive. You must assess exhalation constantly and may need pauses to allow it.
Types: supraglottic, infraglottic, transtracheal, or via rigid bronchoscope.
Risks and contraindications: air trapping leading to raised airway pressure, subcutaneous emphysema, and pneumothorax (especially in patients with bullae). A misaimed jet can cause hypoxia, gastric distention, or barotrauma. High-risk patients include those with morbid obesity, stiff thorax, restrictive or obstructive lung disease, fibrosis, or pulmonary oedema. Avoid jet ventilation with an unprotected airway (full stomach, hiatal hernia, trauma). Use total IV anaesthesia (volatile agents would leak out).
A noninvasive nasal cannula technique for passive apnoeic oxygenation using high flow (10 to 12 L/min), humidified and warmed to protect the mucosa.
Extends safe apnoea times with a more balanced risk profile than jet ventilation.
High morbidity and mortality. Leading cause of accidental death in children under 4 years. Common items: peanuts, popcorn, jellybeans, coins, meat, hot dogs. Nuts and seeds are the most common.
Most common site: right bronchus. Right upper lobe if supine, right lower lobe if standing.
Wheezing, choking, coughing, tachycardia, aphonia, cyanosis (air trapping from swelling).
Rigid bronchoscopy is the traditional gold standard. CT, virtual bronchoscopy, and flexible bronchoscopy are increasingly used. Bronchoscopy mortality is about 0.42%.
Severe laryngeal oedema or bronchospasm needing tracheotomy or reintubation, pneumothorax, pneumomediastinum, cardiac arrest, tracheal or bronchial laceration, hypoxic brain damage.
Object at larynx level: laryngoscopy plus Magill forceps. Do not dislodge it deeper.
Object in distal larynx or trachea: inhalation induction maintaining spontaneous respiration. Use a gentle mask. No cricoid pressure and no positive pressure (either could push the object deeper or occlude the airway).
Sitting position gives the least adverse airway effect.
Premedicate with an antisialagogue, H1 antagonist, and metoclopramide.
Use a rigid bronchoscope for retrieval (ventilate via the side port).
Best overall technique: total IV anaesthesia (cardiovascular stability, relaxation, 100% O₂ for longer hypoventilation tolerance). If the patient has a full stomach, use rapid-sequence induction and be prepared for complete airway occlusion.
Rigid bronchoscopy complications: dental, gum, or lip damage; vagal stimulation from head extension; tracheal tears; hypoxaemia; hypercarbia; barotrauma; dysrhythmias. The surgeon must be ready for emergency tracheotomy or cricothyrotomy.
After retrieval: extubate awake and normocapnic with reflexes intact. Laryngeal and subglottic oedema can develop up to 24 hours post-procedure. Check for oedema by deflating the cuff and occluding the lumen to listen for a leak. Racemic epinephrine, bronchodilators, and steroids are helpful.
"Cocaine and epinephrine can be safely combined in ENT." They should not be combined in most cases. The combined sympathetic stimulation can produce dangerous hypertension, tachycardia, and dysrhythmias. Omit cocaine entirely in patients with cardiac disease or risk.
"Wrapping a standard tube with reflective tape is adequate for laser cases." It is not. The tape dries out and becomes more flammable. Use a purpose-built laser tube.
"Jet ventilation is safe in patients with obstructive lung disease." It is high-risk. Air trapping, raised airway pressure, and pneumothorax are real dangers, especially in patients with bullae.
"Positive pressure during foreign-body aspiration helps ventilate the patient." It can push the object deeper or completely occlude the airway. Maintain spontaneous respiration.
The fire triad is the basis of every operating-room fire-prevention protocol, not just in ENT. Understanding it is what lets you quickly identify and eliminate the ignition, fuel, or oxidiser element. Deliberate controlled hypotension is used beyond ENT in procedures such as spinal surgery and major orthopaedic work. THRIVE has become increasingly popular in difficult-airway management outside the ENT theatre, including in emergency departments and intensive care units, precisely because it extends safe apnoea time without the barotrauma risks of jet ventilation.
⚠️ Cocaine is the only local anaesthetic with intrinsic vasoconstriction. Max dose 3 mg/kg. Do not combine with epinephrine in patients with cardiac disease.
⚠️ Benzocaine can cause methemoglobinaemia. This is a favourite exam question.
⚠️ The fire triad: O₂ + fuel + ignition. Keep O₂ at 30% or below, avoid N₂O, and use a laser tube with a methylene-blue saline cuff.
⚠️ During HFJV, expiration is passive. You must assess exhalation constantly and may need pauses. Failure to do so leads to air trapping, raised airway pressure, and barotrauma.
⚠️ Foreign bodies most commonly lodge in the right bronchus. Maintain spontaneous respiration during inhalation induction; no positive pressure, no cricoid pressure.
⚠️ Glycopyrrolate is preferred over atropine as an antisialagogue in ENT (less tachycardia, no sedation).
⚠️ For controlled hypotension, do not let MAP fall below 50 to 60 mmHg or more than 20% below baseline. Chronic hypertensives need a higher floor.
True or false: Cocaine is the only local anaesthetic that produces vasoconstriction on its own.
Fill in the blank: The three elements of the fire triad are __________, __________, and __________.
True or false: During high-frequency jet ventilation, both inspiration and expiration are active processes.
Fill in the blank: Foreign bodies in children most commonly lodge in the __________ bronchus.
True or false: Positive-pressure ventilation should be applied during inhalation induction for foreign-body aspiration.
Answers: 1. True. 2. Oxidiser (O₂/N₂O), fuel, ignition source. 3. False (inspiration is active, expiration is passive). 4. Right. 5. False (it can push the object deeper or occlude the airway).
Q: Why is glycopyrrolate preferred over atropine as an antisialagogue in ENT?
A: It produces less tachycardia and does not cross the blood-brain barrier, so it causes no sedation.
Q: What is the maximum dose of topical cocaine (4% solution), and what makes it pharmacologically unique among local anaesthetics?
A: 3 mg/kg. It is the only local anaesthetic with intrinsic vasoconstriction, because it blocks norepinephrine and epinephrine reuptake.
Q: Name three measures to prevent airway fire during laser surgery.
A: Keep FiO₂ at 30% or below, avoid N₂O, and use a laser-specific ETT with the cuff inflated with methylene-blue-dyed saline.
Q: What is the recommended lower limit for MAP during deliberate controlled hypotension, and which patient group needs a higher floor?
A: MAP should not fall below 50 to 60 mmHg or more than 20% below baseline. Chronic hypertensives need a higher floor.
Q: A child presents with a foreign body in the distal trachea. Describe the preferred induction technique and two things you must avoid.
A: Use inhalation induction maintaining spontaneous respiration with a gentle mask. Avoid cricoid pressure and positive-pressure ventilation, as either could push the object deeper or occlude the airway.
Q: Why is positive-pressure ventilation during an active airway fire described as a "blowtorch effect"?
A: Positive pressure forces oxygen-rich gas through the site of combustion, dramatically accelerating and worsening the fire.
Local-anaesthetic pharmacology (doses, toxicity, methemoglobinaemia) connects to the regional anaesthesia and pharmacology chapters of any anaesthesia curriculum.
The fire triad applies across all surgical specialities, not only ENT, and is a core topic in operating-room safety curricula.
Foreign-body aspiration in children links to paediatric emergency medicine and the paediatric airway chapter.
topical local anaesthetics, cocaine vasoconstriction, lidocaine, benzocaine, methemoglobinaemia, bupivacaine, epinephrine concentration, glycopyrrolate, antisialagogue, PONV, antiemetic, deliberate hypotension, controlled hypotension, sodium nitroprusside, dexmedetomidine, esmolol, nicardipine, remifentanil, laser surgery, CO₂ laser, Nd:YAG laser, Ho:YAG laser, airway fire, fire triad, laser tube, methylene blue saline cuff, endoscopy, microlaryngoscopy, jet ventilation, HFJV, high-frequency jet ventilation, THRIVE, apnoeic oxygenation, foreign-body aspiration, right bronchus, rigid bronchoscopy, Chapter 43, ENT anaesthesia