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ANAESTHETIC DRUGS IN ENT SURGERY

(RGUHS 20-Mark Long Essay Answer)

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INTRODUCTION

• Adequate depth of anaesthesia and analgesia
• Hemodynamic stability (often with controlled hypotension)
• Rapid, smooth emergence with minimal PONV
• Protection against laryngospasm and bronchospasm
• Preservation of airway reflexes at the right time

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FLOWCHART 1: OVERVIEW OF ANAESTHETIC DRUGS IN ENT

ANAESTHETIC DRUGS IN ENT
         │
┌────────┴────────┐
│                 │
LOCAL         GENERAL
ANAESTHESIA   ANAESTHESIA
│                 │
├─ Topical        ├─ PREMEDICATION
├─ Infiltration   ├─ INDUCTION
├─ Nerve block    ├─ MAINTENANCE
└─ Regional       └─ MUSCLE RELAXATION +
                     REVERSAL + ANALGESICS

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SECTION A: LOCAL ANAESTHETIC DRUGS IN ENT

1. COCAINE (4–10%)

• Only local anaesthetic with intrinsic vasoconstrictive property
• Used topically in nasal surgery, rhinoscopy, and fiberoptic nasotracheal intubation
• Acts by blocking Na+ channels AND inhibiting noradrenaline reuptake (vasoconstriction)
• Maximum safe dose: 3 mg/kg (never exceed 200 mg in adults)
• Applied as:
  • 4% solution on ribbon gauze for nasal packing
  • 10% solution for nasal mucosa (up to 4 mL) with adrenaline 1:1000 (up to 1 mL) for better vasoconstriction
• Systemic toxicity: hypertension, arrhythmias, CNS stimulation → seizures
• Never combine with adrenaline in patients on MAO inhibitors or beta-blockers

2. LIGNOCAINE (LIDOCAINE) (1–4%)

• Most widely used local anaesthetic in ENT
• Forms used:
  • 2% spray - topical for pharynx, larynx (before laryngoscopy/bronchoscopy)
  • 4% solution - superior laryngeal nerve block; transtracheal block
  • 1–2% infiltration - post-auricular, septoplasty, FESS
  • 10% spray - oropharynx, nasal cavity before instrumentation
• Maximum dose: 3 mg/kg (plain); 7 mg/kg (with adrenaline)
• Onset: 2–5 min; Duration: 1–2 hours
• Antidote for toxicity: IV lipid emulsion 20%

3. ADRENALINE (EPINEPHRINE) with Local Anaesthetics

• Added as 1:80,000 to 1:200,000 concentration
• Benefits in ENT:
  • Reduces surgical bleeding (bloodless field in FESS, septoplasty)
  • Prolongs duration of local anaesthetic
  • Reduces systemic absorption
• Avoid in patients with: hypertension, arrhythmias, thyrotoxicosis
• Halothane sensitises myocardium to adrenaline - use sevoflurane/isoflurane instead

4. BUPIVACAINE (0.25–0.5%)

• Used for post-operative analgesia in ENT: tonsillectomy, parotidectomy, mastoidectomy
• Peritonsillar infiltration with 0.5% bupivacaine reduces post-tonsillectomy pain
• Long duration: 4–8 hours
• Most cardiotoxic of all local anaesthetics

5. ROPIVACAINE (0.2–0.75%)

• Safer alternative to bupivacaine
• Less cardiotoxic, less motor block
• Used in peritonsillar and post-auricular blocks

FLOWCHART 2: LOCAL ANAESTHESIA IN NASAL SURGERY

NASAL SURGERY (FESS / SEPTOPLASTY)
              │
   ┌──────────┴──────────┐
   │                     │
TOPICAL                INFILTRATION
COCAINE 4-10%          Lignocaine 2%
+/- Adrenaline         + Adrenaline
(nasal packing)        1:80,000
                       (submucous)
              │
   ┌──────────┴──────────┐
   │                     │
SPG BLOCK           INFRAORBITAL
(Sphenopalatine       NERVE BLOCK
 Ganglion Block)    (Lignocaine 2%)
   │
Lignocaine 4%
trans-nasal

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SECTION B: GENERAL ANAESTHETIC DRUGS IN ENT

FLOWCHART 3: SEQUENCE OF GENERAL ANAESTHESIA IN ENT

PREOPERATIVE
ASSESSMENT
     │
PREMEDICATION
     │
     ↓
INDUCTION AGENTS
(IV / Inhalational)
     │
     ↓
AIRWAY MANAGEMENT
(ETT / LMA / Jet ventilation)
     │
     ↓
MAINTENANCE
(Volatile / TIVA)
     │
     ↓
MUSCLE RELAXANTS
+ REVERSAL
     │
     ↓
EMERGENCE &
EXTUBATION
     │
     ↓
POSTOPERATIVE
ANALGESIA + ANTIEMETICS

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I. PREMEDICATION DRUGS

• Antisialagogues are essential before microlaryngoscopy, bronchoscopy - wet field impairs visualization
• Premedication with dexamethasone (0.15 mg/kg) is standard before tonsillectomy to reduce swelling and PONV
• Avoid heavy premedication in patients with obstructive sleep apnoea (OSA) and upper airway obstruction

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II. INDUCTION AGENTS

A. PROPOFOL (2,6-diisopropylphenol)

• Gold standard induction agent in ENT surgery
• Dose: 1.5–2.5 mg/kg IV (1 mg/kg in elderly)
• Advantages in ENT:
  • Smooth, rapid induction (30–45 seconds)
  • Suppresses laryngeal reflexes - reduces laryngospasm
  • Antiemetic properties (reduces PONV - critical for ENT day surgery)
  • Produces excellent conditions for LMA insertion without muscle relaxants
  • Short context-sensitive half-life - rapid emergence
• Disadvantages:
  • Pain on injection (reduce with lignocaine 40 mg IV prior)
  • Hypotension, apnoea on induction
  • No analgesic property
• Used for both induction and maintenance (TIVA) in ENT

B. THIOPENTONE (THIOPENTAL)

• Dose: 3–7 mg/kg IV
• Classical induction agent (now largely replaced by propofol)
• Still used in status epilepticus, neurosurgery
• Disadvantages in ENT:
  • Precipitates laryngospasm more than propofol
  • Pro-emetic, no antiemetic effect
  • Prolonged hangover effect

C. KETAMINE

• Dose: 1–2 mg/kg IV or 5–10 mg/kg IM
• Dissociative anaesthetic - produces analgesia + anaesthesia
• Unique features relevant to ENT:
  • Maintains airway reflexes and muscle tone (NOT truly protective)
  • Increases secretions - MUST give glycopyrrolate/atropine before
  • Increases blood pressure and heart rate (useful in shocked patients)
  • Hallucinations, emergence delirium - co-administer midazolam
  • Useful in compromised/obstructed airway cases where spontaneous breathing must be maintained
  • Risk of laryngospasm due to excess secretions
• Used in pediatric ENT (IM route), dressing changes, emergency tracheostomy under LA+sedation

D. ETOMIDATE

• Dose: 0.2–0.3 mg/kg IV
• Hemodynamically stable - ideal for cardiovascular-compromised patients
• Adrenocortical suppression on repeat dosing (avoid infusion)
• Pain on injection, myoclonus; high incidence of PONV

E. DEXMEDETOMIDINE

• Alpha-2 agonist - emerging induction/sedation agent in ENT
• Produces sedation without respiratory depression
• Ideal for awake fiberoptic intubation in difficult airway cases
• Dose: 0.5–1 mcg/kg IV over 10 min loading, then 0.2–0.7 mcg/kg/hr
• Provides cooperative sedation - patient follows commands while deeply sedated
• Reduces opioid requirements (opioid-sparing effect)
• Controls hemodynamic stress response to laryngoscopy
• Recent evidence (2024): reduces emergence agitation in pediatric ENT

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III. INHALATIONAL MAINTENANCE AGENTS

FLOWCHART 4: INHALATIONAL ANAESTHETICS IN ENT

INHALATIONAL AGENTS
        │
┌───────┼───────────┐
│       │           │
HALOTHANE  ISOFLURANE  SEVOFLURANE  DESFLURANE
(Historical) (Less use)  (Preferred)  (Rapid emergence)
        │
   ENT SPECIFIC CONCERNS:
   ─ Halothane: sensitises myocardium to adrenaline
     (AVOID with adrenaline infiltration)
   ─ Sevoflurane: safe with adrenaline
   ─ Laser surgery: use O2/air, NOT N2O (flammable)
   ─ N2O: avoid in middle ear surgery
     (expands gas-filled cavities → tympanic membrane displacement)

SEVOFLURANE

• Preferred volatile agent in ENT, especially pediatric ENT
• Non-pungent - ideal for inhalational induction in children (no IV access)
• Rapid onset and offset (low blood:gas coefficient = 0.65)
• Smooth laryngeal mask insertion without muscle relaxants
• Minimal airway irritation - does not trigger coughing/bronchospasm
• Can be used for maintenance in FESS, tympanoplasty, tonsillectomy
• Combine with remifentanil to suppress coughing during extubation (Miller's Anesthesia 10e)
• Emergence agitation in children - pretreat with dexmedetomidine or midazolam

ISOFLURANE

• More pungent than sevoflurane - not ideal for inhalational induction
• Produces controlled hypotension (reduces bleeding in nasal surgery)
• MAC = 1.2%

DESFLURANE

• Most rapid emergence - ideal for day surgery ENT
• Highly pungent - NEVER use for mask induction
• Airway irritant - increases secretions, coughing, laryngospasm
• Avoid for laryngeal surgery

NITROUS OXIDE (N2O) - Specific ENT Concern

• CONTRAINDICATED in middle ear surgery (tympanoplasty, ossiculoplasty, myringoplasty)
  • Diffuses into air-filled middle ear cavity 35x faster than N2 leaves
  • Middle ear pressure rises from 0 to +300 mmH2O in 30 min
  • Can displace tympanic membrane graft, disarticulate ossicular chain
  • After N2O cessation, pressure reverses → serous otitis
• Controversial in mastoidectomy - avoid if possible
• Safe to use in most other ENT procedures (rhinology, laryngology)

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IV. OPIOID ANALGESICS IN ENT

• Metabolised by non-specific plasma esterases (not hepatic/renal)
• Context-sensitive half-life = 3–4 min regardless of infusion duration
• Ideal for microlaryngoscopy, laser laryngeal surgery, FESS (precise titration, rapid offset)
• Blunts cough reflex on extubation when combined with propofol or sevoflurane
• Provide post-operative analgesia with paracetamol/NSAIDs before stopping remifentanil infusion (no residual analgesia!)

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V. MUSCLE RELAXANTS IN ENT

FLOWCHART 5: MUSCLE RELAXANTS IN ENT

MUSCLE RELAXANTS IN ENT
          │
  ┌───────┴───────────┐
  │                   │
DEPOLARISING        NON-DEPOLARISING
SUCCINYLCHOLINE     (Competitive)
│                   │
RSI, emergency      Elective relaxation
Dose: 1–2 mg/kg    │
Side effects:      ├── VECURONIUM (0.1 mg/kg)
- Raised IOP       │   - Intermediate; cardiovascularly stable
- Hyperkalemia     ├── ROCURONIUM (0.6–1.2 mg/kg)
- Myalgia          │   - Rapid onset; RSI alternative
- Masseter spasm   ├── ATRACURIUM (0.5 mg/kg)
- Malignant        │   - Hoffman elimination (renal/hepatic failure)
  hyperthermia     └── CISATRACURIUM (0.15 mg/kg)
                       - Less histamine release vs atracurium

• In microlaryngoscopy: deep relaxation required for operating in the larynx
• In tonsillectomy: short-duration relaxation adequate
• In laser surgery: deep relaxation prevents unexpected movement
• Succinylcholine raises intraocular pressure - avoid in concurrent eye procedures
• Rocuronium (1.2 mg/kg) + Sugammadex - preferred RSI in difficult airway cases (rapid reversal available)

REVERSAL AGENTS

• Neostigmine (0.05 mg/kg) + Glycopyrrolate (0.01 mg/kg): reversal of non-depolarising NMBs
• Sugammadex (2–4 mg/kg): selective reversal of rocuronium/vecuronium (no muscarinic side effects, faster, more complete reversal)
  • Preferred in ENT: reduces residual NMB-related airway complications

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VI. TOTAL INTRAVENOUS ANAESTHESIA (TIVA) IN ENT

Advantages over inhalational techniques:

1. Markedly reduced PONV (propofol antiemetic effect)
2. Rapid, smooth emergence - ideal for day surgery
3. No airway pollution with volatile gases (important in shared airway)
4. Reduced emergence agitation in children
5. Better hemodynamic control - controlled hypotension in FESS/rhinology
6. Reduced postoperative respiratory complications in OSA patients

TIVA Protocol (ENT):

Propofol: Induction 1.5–2.5 mg/kg, Maintenance 4–10 mg/kg/hr (TCI: Cp 3–6 mcg/mL)
Remifentanil: 0.1–0.5 mcg/kg/min infusion (TCI: Ce 2–4 ng/mL)
Target-controlled infusion (TCI) using Marsh/Schnider model (Propofol)
                                       Minto model (Remifentanil)

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VII. SPECIAL ANAESTHETIC SITUATIONS IN ENT

A. TONSILLECTOMY

• Standard: Propofol induction + Sevoflurane/TIVA maintenance
• Oral Ring-Adair-Elwyn (RAE) tube or south-facing preformed ETT
• Dexamethasone 0.15 mg/kg reduces edema, PONV
• Paracetamol + ibuprofen + peritonsillar bupivacaine (0.5%) for analgesia
• Avoid codeine in children (risk of fatal respiratory depression)
• Post-operative haemorrhage (re-bleed patient): treat as full stomach + hypovolemia - RSI with cricoid pressure

B. MICROLARYNGOSCOPY / BRONCHOSCOPY

• Short, potent anaesthesia
• Spontaneous or apnoeic/jet ventilation techniques
• TIVA: propofol + remifentanil infusion
• Neuromuscular blockade for rigid laryngoscopy
• Topical lignocaine spray (4%) to larynx/trachea before instrumentation
• Glycopyrrolate essential for dry field
• Ventilation via:
  • Microlaryngoscopy tube (MLT - 4–5 mm ID, long)
  • Sanders injector jet ventilation (high-pressure O2)
  • High-frequency jet ventilation (HFJV)

C. LASER SURGERY OF LARYNX

• CRITICAL - risk of airway fire
• Avoid nitrous oxide (supports combustion)
• Use oxygen/air mixture (FiO2 < 0.3 to reduce fire risk, or helium-oxygen)
• Use laser-resistant ETT (Laser-Flex, Sheridan laser guard tube)
• Cuff inflated with saline + methylene blue (leak detection if burned)
• Keep FiO2 as low as possible to maintain SpO2 > 95%

D. NASAL SURGERY (FESS, SEPTOPLASTY)

• Controlled hypotension: MAP 55–65 mmHg for bloodless field
  • Propofol + remifentanil TIVA
  • Labetalol / esmolol / nitroglycerine as adjuncts
• Topical cocaine 4–10% + infiltration lignocaine/adrenaline
• Throat pack mandatory (prevents blood swallowing)
• Head-up 15–20° tilt

E. MIDDLE EAR SURGERY (TYMPANOPLASTY, MASTOIDECTOMY)

• Avoid nitrous oxide (expands middle ear gas → graft displacement)
• TIVA preferred
• Deep anaesthesia to avoid sudden movement during ossicular chain surgery
• Facial nerve monitoring - avoid or use minimal muscle relaxants

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VIII. POSTOPERATIVE NAUSEA AND VOMITING (PONV) PREVENTION

• Female sex
• Non-smoker
• History of PONV/motion sickness
• Postoperative opioid use

• Propofol-based TIVA (versus inhalational)
• Ondansetron 4 mg IV
• Dexamethasone 8 mg IV at induction
• Scopolamine transdermal patch
• Avoid N2O
• Minimize opioids (use NSAIDs + paracetamol + regional techniques)

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SECTION C: RECENT ADVANCES (2022–2025)

1. REMIMAZOLAM

• New ultra-short-acting benzodiazepine (ester-linked, metabolised by tissue esterases)
• Onset: 1–3 min; Duration: 10–15 min; Reversible with flumazenil
• Approved for procedural sedation and induction
• Studies (2024) show superior hemodynamic stability versus propofol
• Particularly useful in ambulatory ENT and short otolaryngology procedures
• Evidence: Cheng et al., BMC Anesthesiology 2024 - efficacy and safety in short ENT surgery confirmed

2. TARGET-CONTROLLED INFUSION (TCI) WITH PROCESSED EEG MONITORING

• BIS (Bispectral Index) / Entropy monitoring for depth of anaesthesia
• Reduces drug overdose, speeds emergence, reduces awareness
• Prevents emergence agitation in pediatric ENT
• TCI of propofol (Marsh/Schnider model) + remifentanil (Minto model) is current standard

3. DEXMEDETOMIDINE - EXPANDED ROLE

• Reduces emergence agitation in pediatric ENT (tonsillectomy/adenoidectomy)
• Provides opioid-sparing analgesia
• Ideal for awake fiberoptic intubation in obstructed airway (head and neck cancer, Ludwig's angina)
• Intranasal dexmedetomidine (1–2 mcg/kg) as premedication in children - avoids IV cannulation distress

4. MULTIMODAL ANALGESIA (OPIOID-FREE/OPIOID-SPARING)

• Pregabalin premedication reduces postoperative analgesic needs in ENT surgery
• Combination: Paracetamol + NSAIDs + Regional block + Dexamethasone
• Reduces opioid-related adverse events, particularly in OSA patients

5. SUGAMMADEX FOR REVERSAL

• Selective reversal of rocuronium/vecuronium
• No cholinergic side effects (no need for anticholinergic co-administration)
• Rapidly reversing deep neuromuscular block - critical in ENT emergency airway situations

6. BIPHASIC CUIRASS VENTILATION (BCV)

• Non-invasive ventilatory support during shared airway surgeries
• Reduces need for endotracheal intubation in selected patients
• Evidence: Bodhey et al., Cureus 2024 - comprehensive review of BCV for airway surgeries (PMID: 39791051)

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DIAGRAM 1: THE SHARED AIRWAY CONCEPT IN ENT

┌─────────────────────────────────────────┐
│           SHARED AIRWAY IN ENT          │
│                                         │
│   ANAESTHESIOLOGIST       SURGEON       │
│         │                    │          │
│    [ANAESTHESIA]         [SURGERY]      │
│         │                    │          │
│         └─────────┬──────────┘          │
│                   │                     │
│              [AIRWAY]                   │
│                   │                     │
│    ┌──────────────┴──────────────┐      │
│    │        CHALLENGES           │      │
│    ├─────────────────────────────┤      │
│    │ - Limited access to airway  │      │
│    │ - Risk of laryngospasm      │      │
│    │ - Fire hazard (laser)       │      │
│    │ - Shared O2 circuit         │      │
│    │ - Tube displacement risk    │      │
│    │ - Bleeding into airway      │      │
│    └─────────────────────────────┘      │
└─────────────────────────────────────────┘

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DIAGRAM 2: DRUG INTERACTIONS IN ENT ANAESTHESIA

AVOID COMBINATIONS IN ENT:
──────────────────────────────────────────
Halothane  ───×───  Adrenaline
(Ventricular arrhythmias)

N2O  ───×───  Middle Ear Surgery
(Cavity expansion → graft failure)

Succinylcholine ───×──  Open eye injury / burns / hyperkalemia states
                       (Raised K+ → cardiac arrest)

Ketamine ───×─── ENT if secretions uncontrolled
(Without prior glycopyrrolate)

Codeine ───×─── Children post-tonsillectomy
(CYP2D6 ultra-metabolisers → respiratory arrest)
──────────────────────────────────────────

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SUMMARY TABLE: DRUG CHOICES FOR COMMON ENT PROCEDURES

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KEY POINTS FOR EXAM (RGUHS)

1. Cocaine is the only local anaesthetic with vasoconstrictive property - used topically in nasal surgery (max 3 mg/kg, never exceed 200 mg)
2. N2O is contraindicated in middle ear surgery - causes pressure rise in the middle ear cavity, displacing tympanic membrane grafts
3. Halothane sensitises the myocardium to adrenaline - avoid combination (use sevoflurane instead)
4. Propofol + Remifentanil TIVA = gold standard for ENT anaesthesia (reduced PONV, rapid emergence, controlled hypotension)
5. Dexamethasone is given at induction for tonsillectomy - reduces edema AND prevents PONV
6. Codeine is absolutely contraindicated in children post-tonsillectomy (Black box FDA warning - CYP2D6 ultra-rapid metabolisers)
7. Antisialagogues (glycopyrrolate/atropine) are mandatory before microlaryngoscopy
8. In laser surgery - use air/O2 mixture, never N2O, laser-resistant ETT with saline-filled cuff
9. Sugammadex is preferred reversal agent in ENT - complete, predictable, no muscarinic side effects
10. Remimazolam - newest agent (2024) approved for ENT sedation/short procedures with flumazenil reversal

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• Scott-Brown's Otorhinolaryngology Head & Neck Surgery, 8e (Chapter on Anaesthesia in ENT)
• Cummings Otolaryngology: Head and Neck Surgery, 7e
• Stell & Maran's Head and Neck Surgery, 4e
• Dhingra PL: Diseases of Ear, Nose and Throat, 8e
• Hazarika P: ENT Head and Neck Surgery
• Zakir Hussain: Textbook of ENT
• Miller's Anesthesia, 10e (2023)
• Morgan & Mikhail's Clinical Anesthesiology, 7e
• Bodhey A et al. Biphasic Cuirass Ventilation for Airway Surgeries. Cureus 2024 (PMID: 39791051)
• Cheng W et al. Efficacy and safety of remimazolam tosilate in short otolaryngology surgery. BMC Anesthesiol 2024;24:407
• Jprevepi.com - Anesthesia for ambulatory and office-based ENT surgery, 2024 review