Anaesthesia
Final Professional MBBS — Anaesthesiology. Explanation-first answers covering the principles and conduct of anaesthesia, the anaesthesia machine, airway, drugs, regional techniques, monitoring, fluids, complications and resuscitation, with classifications, comparison tables, drug doses, clinical pearls and key-point recaps from Morgan & Mikhail and Miller's Anesthesia.
Definition & Indications
Endotracheal (tracheal) intubation is the placement of a cuffed tube through the larynx into the trachea to secure and control the airway. It provides a definitive, protected airway. Indications include the need to protect the airway from aspiration (full stomach), to provide controlled ventilation (with muscle relaxation, major or long surgery), a shared or inaccessible airway (head/neck surgery, prone position), the need for positive-pressure ventilation (thoracic, laparoscopic), and resuscitation.
Indication Example Airway protection Full stomach, risk of aspiration Controlled ventilation Muscle relaxation, major/long surgery, thoracic Access / position Head & neck surgery, prone, shared airway Maintain patency Difficult mask airway, airway obstruction Resuscitation / ICU Cardiac arrest, respiratory failure Technique
After preoxygenation, anaesthesia is induced and (usually) a muscle relaxant given. The patient is positioned in the ‘sniffing’ position (neck flexed, head extended) to align the oral, pharyngeal and laryngeal axes. A laryngoscope is introduced to expose the glottis, and the tracheal tube is passed between the vocal cords; the cuff is inflated and placement confirmed before securing the tube and connecting the breathing system.
Confirmation of Placement
Correct tracheal placement must be confirmed: the gold standard is a sustained capnograph (end-tidal CO₂) trace over several breaths, supported by bilateral chest movement and breath sounds, absence of sounds over the epigastrium, misting of the tube, and maintained oxygen saturation. Persistent end-tidal CO₂ is the most reliable sign that the tube is in the trachea.
💡‘No trace = wrong place’: a sustained end-tidal CO₂ waveform is the single most reliable confirmation of tracheal intubation. An oesophageal intubation may briefly show a trace but it is not sustained.⚠️An unrecognised oesophageal intubation is rapidly fatal. Always confirm with capnography; if there is any doubt about tube position and it cannot be confirmed, remove the tube and ventilate with a bag and mask (‘if in doubt, take it out’) rather than persisting.Complications
During intubation: trauma to lips, teeth, pharynx and larynx; oesophageal or endobronchial (usually right main bronchus) intubation; the pressor response (hypertension, tachycardia); laryngospasm and hypoxia if difficult. While in place: tube obstruction/kinking, displacement, cuff problems. After extubation: sore throat, hoarseness, and — rarely — laryngeal oedema or, late, subglottic stenosis.
The Pressor Response & Its Attenuation
Laryngoscopy and intubation are powerfully stimulating, and in a lightly anaesthetised patient they provoke a pressor (sympathetic) response — a surge of hypertension and tachycardia, and sometimes arrhythmia and a rise in intracranial and intraocular pressure. In most healthy patients this is transient and harmless, but in those with ischaemic heart disease, hypertension, cerebral aneurysm or a penetrating eye injury it can be dangerous, so it is deliberately blunted by ensuring adequate depth of anaesthesia and analgesia and, where indicated, by opioids, intravenous lignocaine, beta-blockers or vasodilators before laryngoscopy. Recognising which patients need this attenuation is an important part of planning the intubation.
💡Two intubation rules save lives: confirm every tube with a sustained capnograph trace (‘no trace = wrong place’), and if you cannot confirm tracheal placement, take the tube out and ventilate by mask rather than leaving a possibly oesophageal tube in situ.Capnography is the definitive confirmation of tracheal placement. 🔑KEY POINTS TO REMEMBER- Tracheal intubation = cuffed tube through the larynx → a definitive, protected airway.
- Indications: airway protection, controlled ventilation, access/position, patency, resuscitation.
- Technique: preoxygenate, induce + relaxant, sniffing position, laryngoscopy, tube through cords, inflate cuff.
- Confirm with sustained capnography (‘no trace = wrong place’) + bilateral air entry.
- Complications: dental/airway trauma, oesophageal/endobronchial placement, pressor response, sore throat.
📚SOURCES: Morgan & Mikhail’s Clinical Anesthesiology; Miller’s Anesthesia; Ajay Yadav’s Short Textbook of Anaesthesia.Definition & Importance
A difficult airway is a situation in which a trained anaesthetist has difficulty with face-mask ventilation, laryngoscopy, tracheal intubation, or all of these. Failure to manage the airway — and the resulting hypoxia — is one of the leading causes of anaesthetic death and brain injury, so prediction, preparation and a clear plan are fundamental.
Prediction
Difficulty is anticipated by airway assessment: a high Mallampati class, reduced mouth opening, short thyromental distance, limited neck movement/jaw protrusion, receding mandible, large tongue or neck, and conditions distorting the airway (tumours, infection, trauma, rheumatoid arthritis, previous surgery/radiotherapy). A history of previous difficult intubation is highly significant. No single test is reliable, so several are combined.
A simplified failed-intubation plan: escalate stepwise (A→D) only as each step fails, call for help early, and keep the patient oxygenated throughout. Management — the Difficult Airway Algorithm
Management follows a stepwise plan (e.g. the Difficult Airway Society algorithm) with the overriding priority of maintaining oxygenation. Plan A: optimise intubation (position, adjuncts such as a bougie or videolaryngoscope) — limit attempts to avoid trauma. Plan B: insert a supraglottic airway (LMA) to oxygenate. Plan C: revert to face-mask ventilation, and if the situation allows, wake the patient. Plan D: the ‘can’t intubate, can’t oxygenate’ (CICO) emergency — perform front-of-neck access (cricothyroidotomy).
💡The guiding principle throughout a difficult airway is ‘oxygenation, not intubation’ — the patient comes to harm from hypoxia, not from being unintubated. Call for help early, limit intubation attempts, and escalate the plan rather than repeatedly trying to intubate.The Anticipated vs Unanticipated Difficult Airway
If difficulty is anticipated, options include an awake fibreoptic intubation (securing the airway before inducing anaesthesia), videolaryngoscopy, or regional anaesthesia — with everything prepared and skilled help present. The unanticipated difficult airway is managed by the failed-intubation algorithm above. Preparation — equipment, assistance and a shared plan — is the key to both.
⚠️Repeated intubation attempts cause airway trauma, bleeding and oedema that can turn a ‘can’t intubate’ into a ‘can’t oxygenate’ situation. Limit attempts, maintain oxygenation between them, and move down the algorithm decisively rather than persisting.Predictor Concerning finding Mallampati Class III or IV Thyromental distance Less than 6.5 cm Mouth opening (interincisor) Less than 3 cm Neck movement Less than 90 degrees Upper lip bite test Cannot bite upper lip Other Obesity, short neck, buck teeth, previous difficulty 🔑KEY POINTS TO REMEMBER- Difficult airway = difficulty with mask ventilation, laryngoscopy and/or intubation; hypoxia kills.
- Predict by airway assessment (Mallampati, mouth opening, thyromental distance, neck, previous difficulty).
- Algorithm: A optimise intubation → B supraglottic airway → C mask/wake → D CICO → front-of-neck access.
- Priority is OXYGENATION, not intubation; call for help early; limit attempts.
- Anticipated difficulty → awake fibreoptic/videolaryngoscopy with full preparation.
📚SOURCES: Morgan & Mikhail’s Clinical Anesthesiology; Miller’s Anesthesia; Ajay Yadav’s Short Textbook of Anaesthesia.Basic Airway Management
Before any advanced device, the airway is opened and maintained by basic manoeuvres: correct positioning, a head-tilt/chin-lift or, where cervical injury is a concern, a jaw thrust, and face-mask ventilation with a good seal. These simple measures relieve the commonest cause of obstruction — the tongue falling back against the pharynx in the unconscious patient — and are the foundation on which airway rescue rests.
Airway Adjuncts
Simple adjuncts hold the airway open: the oropharyngeal (Guedel) airway sits over the tongue (used in the unconscious patient, as it stimulates gag reflexes if too light), and the nasopharyngeal airway passes through the nose (better tolerated in the semi-conscious). They are used with a face mask to maintain a patent airway and aid ventilation.
Supraglottic Airway Devices
Supraglottic airway devices (SADs), chiefly the laryngeal mask airway (LMA), sit above the larynx and form a seal around the laryngeal inlet without entering the trachea. They provide a hands-free airway for suitable spontaneously breathing patients and are a key rescue device in the difficult-airway algorithm. Second-generation devices add a gastric drain channel for some protection against aspiration and allow higher ventilating pressures.
💡Match the device to the situation: face mask + adjunct for brief/rescue ventilation, supraglottic airway for suitable elective cases and airway rescue, and a tracheal tube when the airway must be protected or high pressures/relaxation are needed.⚠️Supraglottic airways do not reliably protect against aspiration — avoid them in full-stomach/high-risk patients and where high airway pressures are required. If ventilation through a SAD is inadequate, do not persist — escalate the airway plan.Choosing & Escalating
Airway management is a ladder: begin with basic manoeuvres and a mask, add adjuncts, use a supraglottic device, and progress to intubation or front-of-neck access as needed. The skill is in recognising failure of one step early and moving to the next while keeping the patient oxygenated.
Face-Mask Ventilation as the Core Skill
For all the emphasis on tubes and devices, effective face-mask ventilation remains the fundamental airway skill and the fallback when everything else fails, so it is worth doing well: a correctly sized mask is held with a good seal using the ‘C–E’ grip, the airway is opened with head-tilt/chin-lift or jaw thrust, an oropharyngeal or nasopharyngeal adjunct is added if needed, and a two-person technique is used when a single operator cannot achieve a seal. Predictors of difficult mask ventilation — a beard, obesity, edentulousness, age and a history of snoring (remembered by mnemonics such as ‘BONES’) — are sought in advance, because difficult mask ventilation combined with difficult intubation is the truly dangerous combination.
When Each Device Is Appropriate
Choosing an airway is a matter of matching the device to the patient and operation. A face mask alone suits only very short procedures with a low aspiration risk; a supraglottic airway is ideal for many routine, spontaneously-breathing cases in fasted patients at low risk of reflux; and a tracheal tube is chosen whenever the airway must be protected (full stomach, shared airway, prone or head-down positioning), when muscle relaxation and controlled ventilation are required, or when high airway pressures are anticipated. The decision also considers the length of surgery, the patient’s body habitus and comorbidity, and the anaesthetist’s ability to rescue the airway if the first choice fails.
💡Remember the escalation ladder — manoeuvres → adjuncts → mask → supraglottic airway → tracheal tube → front-of-neck access — and that the golden rule at every rung is to keep the patient oxygenated while deciding whether to step up.Simple manoeuvres relieve most airway obstruction. 🔑KEY POINTS TO REMEMBER- Basic manoeuvres first: positioning, head-tilt/chin-lift or jaw thrust, mask ventilation (tongue is the usual obstruction).
- Adjuncts: oropharyngeal (Guedel, unconscious) & nasopharyngeal (semi-conscious) airways.
- Supraglottic airways (LMA) seal above the larynx; hands-free & key rescue device.
- Second-generation SADs add a gastric drain & allow higher pressures but don’t fully prevent aspiration.
- Airway management is a ladder — escalate early while maintaining oxygenation.
📚SOURCES: Morgan & Mikhail’s Clinical Anesthesiology; Miller’s Anesthesia; Ajay Yadav’s Short Textbook of Anaesthesia.Laryngoscopy
Laryngoscopy is the visualisation of the larynx to enable intubation. The traditional direct laryngoscope (e.g. the curved Macintosh blade, whose tip sits in the vallecula, or the straight Miller blade, which lifts the epiglottis) provides a direct line of sight to the glottis. Videolaryngoscopes use a camera at the blade tip to give an indirect view — improving the view in many difficult airways.
Cormack–Lehane grades of the laryngoscopic view: grade 1 (full glottis) to grade 4 (neither glottis nor epiglottis) — higher grades indicate a more difficult intubation. Grading the View (Cormack–Lehane)
The laryngoscopic view is graded by the Cormack–Lehane classification: Grade 1 — most of the glottis visible; Grade 2 — only the posterior glottis/arytenoids; Grade 3 — only the epiglottis; Grade 4 — neither glottis nor epiglottis. Grades 3–4 indicate a difficult intubation.
Equipment
The intubation set includes: laryngoscopes (with a range of blades) and a videolaryngoscope; a range of tracheal tubes (with a checked cuff); a bougie/stylet to aid tube placement (especially with a poor view); a syringe to inflate the cuff; suction; a capnograph and monitoring; and supraglottic airways and front-of-neck equipment for rescue. All equipment is checked before induction.
💡A bougie is a simple, life-saving aid: when only the epiglottis is seen (Cormack–Lehane grade 3), the bougie is passed blindly beneath it into the trachea (feeling tracheal-ring ‘clicks’) and the tube railroaded over it.⚠️Prepare and check all airway equipment before inducing anaesthesia, including alternatives for a difficult airway (bougie, supraglottic airways, videolaryngoscope, front-of-neck kit). Discovering missing or faulty equipment during a crisis costs vital time.Videolaryngoscopy
The widespread adoption of videolaryngoscopes has changed difficult-airway practice. By placing a camera at the blade tip, they provide a view ‘around the corner’ that does not require the oral, pharyngeal and laryngeal axes to be aligned, so they frequently convert a poor direct view (Cormack–Lehane grade 3–4) into a good indirect one and improve first-pass success in many difficult airways. They are increasingly used as a first-line device and are a key tool in the difficult-airway algorithm, though a good view on the screen does not always make tube delivery easy, and skill with a bougie or stylet remains necessary.
🔑KEY POINTS TO REMEMBER- Direct laryngoscopy: Macintosh (curved, vallecula) & Miller (straight, lifts epiglottis) blades; videolaryngoscopy for indirect view.
- Cormack–Lehane grade 1 (full glottis) → 4 (neither); grades 3–4 = difficult.
- Equipment: laryngoscopes, tubes + checked cuff, bougie/stylet, suction, capnograph, rescue devices.
- Bougie rescues a grade-3 view (feel tracheal clicks, railroad the tube).
- Check all airway equipment (incl. difficult-airway kit) before induction.
📚SOURCES: Morgan & Mikhail’s Clinical Anesthesiology; Miller’s Anesthesia; Ajay Yadav’s Short Textbook of Anaesthesia.Overview
Complications of airway management range from minor and transient to immediately life-threatening. They can be grouped by timing — during airway instrumentation, while the airway device is in place, and around extubation — and the most dangerous share a final common pathway of hypoxia.
Laryngospasm
Laryngospasm is a reflex, sustained closure of the vocal cords, usually triggered by airway stimulation (secretions, blood, or airway manipulation) during light anaesthesia (classically at induction or emergence, in ‘stage II’). It causes stridor or complete airway obstruction and, if unrelieved, hypoxia and bradycardia. Treatment: remove the stimulus, 100% oxygen with continuous positive airway pressure and jaw thrust, deepen anaesthesia, and if it persists give a small dose of suxamethonium to relax the cords.
Aspiration & Trauma
Aspiration of gastric contents (Mendelson’s syndrome) occurs when the airway is unprotected in an at-risk patient. Trauma from instrumentation includes damage to lips, teeth (dislodged/broken), the pharynx, larynx and vocal cords, and, rarely, oesophageal or airway perforation.
Malposition & Post-extubation Problems
Malposition: oesophageal intubation (fatal if unrecognised) and endobronchial intubation (usually right main bronchus → one-lung ventilation, hypoxia, collapse). Post-extubation: laryngospasm, airway oedema (especially in children — croup), sore throat and hoarseness, and, rarely, negative-pressure pulmonary oedema (from forced inspiration against a closed glottis).
⚠️Two airway complications are immediately lethal and must be recognised instantly: unrecognised oesophageal intubation (confirm every tube with capnography) and ‘can’t intubate, can’t oxygenate’ (proceed without delay to front-of-neck access). Both kill through hypoxia within minutes.💡Laryngospasm is the classic emergence/induction emergency: treat with 100% oxygen, CPAP and jaw thrust, deepen anaesthesia, and use a small dose of suxamethonium if it persists. Avoid stimulating the airway during the light ‘stage II’ plane.Dental & Airway Trauma
Damage to the teeth is one of the commonest reasons for medico-legal claims in anaesthesia, so the dentition is examined and documented before laryngoscopy, loose or capped teeth and dental work are noted, and care is taken not to lever the laryngoscope against the upper incisors. Soft-tissue trauma to the lips, tongue, pharynx and larynx, and rarer but serious injuries such as arytenoid dislocation or perforation, are minimised by gentle technique, an appropriately sized tube, and limiting the number and force of attempts — again underlining why repeated forceful laryngoscopy is harmful.
Airway Oedema & Post-obstruction Pulmonary Oedema
Two swelling-related complications deserve emphasis. Airway oedema after prolonged or traumatic intubation, or after airway surgery, can narrow the airway dangerously on extubation — in small children even a little subglottic oedema (post-extubation ‘croup’) markedly increases resistance because their airways are so narrow — and it is managed with humidified oxygen, nebulised adrenaline and steroids, with reintubation held in reserve. Negative-pressure (post-obstruction) pulmonary oedema follows a vigorous inspiratory effort against a closed glottis, as in laryngospasm, when the resulting very negative intrathoracic pressure draws fluid into the alveoli; it presents with desaturation and pink frothy secretions shortly after the obstruction is relieved and usually responds to oxygen and positive-pressure support.
💡Group airway complications by when they strike — during instrumentation (trauma, oesophageal or bronchial misplacement, the pressor response), while the device is in place (obstruction, displacement, cuff problems), and around extubation (laryngospasm, oedema, aspiration) — but treat them all with the same first priority: restore oxygenation.Unrecognised oesophageal intubation is the lethal complication. 🔑KEY POINTS TO REMEMBER- Group by timing: during instrumentation, device in place, and around extubation; hypoxia is the common danger.
- Laryngospasm (light anaesthesia): O₂ + CPAP + jaw thrust, deepen, suxamethonium if persistent.
- Aspiration; trauma to teeth/lips/larynx; oesophageal (fatal) & endobronchial malposition.
- Post-extubation: laryngospasm, airway oedema/croup, sore throat, negative-pressure pulmonary oedema.
- Instantly lethal: unrecognised oesophageal intubation & CICO — confirm tubes; get front-of-neck access.
📚SOURCES: Morgan & Mikhail’s Clinical Anesthesiology; Miller’s Anesthesia; Ajay Yadav’s Short Textbook of Anaesthesia.Definition & Cause
Laryngospasm is a reflex, involuntary sustained closure of the vocal cords (spasm of the laryngeal muscles) that partially or completely obstructs the airway. It is provoked by stimulation of the airway — by secretions, blood, vomit, an airway device or surgical stimulus — while anaesthesia is too light, classically at induction or emergence (stage II).
Features & Management
It presents with stridor (partial) or complete airway obstruction with paradoxical (see-saw) chest/abdominal movement and falling oxygen saturation; if unrelieved it causes hypoxia, bradycardia and cardiac arrest. Management, in order: remove the stimulus and any secretions (suction), apply 100% oxygen with continuous positive airway pressure and a firm jaw thrust, deepen anaesthesia (e.g. propofol), and if spasm persists give a small dose of suxamethonium (± atropine for bradycardia) and ventilate.
💡The classic first-line for laryngospasm is 100% O₂, CPAP and jaw thrust (‘Larson’s point’ pressure behind the ear lobes may help), progressing to deepening anaesthesia and then suxamethonium if it does not break.⚠️Watch for negative-pressure pulmonary oedema after a severe laryngospasm — forced inspiration against a closed glottis generates very negative intrathoracic pressure that draws fluid into the alveoli, causing post-obstruction pulmonary oedema.Prevention
Because laryngospasm is triggered by airway stimulation during light anaesthesia, prevention centres on avoiding such stimulation at vulnerable moments: clearing secretions and blood before they reach the cords, not inserting airways or extubating in the light ‘stage II’ plane, and either keeping the patient adequately deep or waiting until they are fully awake. It is commoner in children, in smokers and after upper-airway surgery, so extra vigilance is warranted in these groups.
💡The stepwise treatment to memorise is 100% oxygen, CPAP and jaw thrust → deepen anaesthesia → suxamethonium if it persists — and prevention lies in not stimulating the airway during the light stage-II plane.100% oxygen, jaw thrust, deepen anaesthesia; suxamethonium if persistent. 🔑KEY POINTS TO REMEMBER- Reflex sustained vocal-cord closure from airway stimulation during light anaesthesia (stage II).
- Stridor/obstruction, see-saw breathing, desaturation → hypoxia & bradycardia if unrelieved.
- Treat: remove stimulus/suction, 100% O₂ + CPAP + jaw thrust, deepen, suxamethonium if persistent.
- Beware negative-pressure pulmonary oedema afterwards.
📚SOURCES: Morgan & Mikhail’s Clinical Anesthesiology; Miller’s Anesthesia; Ajay Yadav’s Short Textbook of Anaesthesia.Definition
The Cormack–Lehane classification grades the view of the larynx obtained at direct laryngoscopy. Unlike the Mallampati score (a bedside prediction), Cormack–Lehane describes what is actually seen during laryngoscopy, and is used to document the airway and predict/record difficulty.
Grades
Grade 1: most of the glottis (vocal cords) is visible. Grade 2: only the posterior part of the glottis/arytenoids is seen. Grade 3: only the epiglottis is visible (no glottis). Grade 4: neither the glottis nor the epiglottis is seen. Grade 2 is often subdivided into 2a and 2b. Grades 3 and 4 signify a difficult intubation.
💡Distinguish the two scores: Mallampati is a pre-operative prediction (mouth open, tongue out), whereas Cormack–Lehane is the actual view at laryngoscopy. A grade-3 view (epiglottis only) is the classic indication for a bougie.Improving the View
When the initial Cormack–Lehane view is poor, several manoeuvres can improve it before abandoning the attempt: optimising the head position, external laryngeal manipulation (the ‘BURP’ manoeuvre — backward, upward, rightward pressure on the thyroid cartilage), using a different or longer blade, and switching to a videolaryngoscope. Documenting the best view achieved, and how it was obtained, is valuable information for anyone anaesthetising the patient in future.
Why It Matters & Its Limitations
The Cormack–Lehane grade is valuable because it records the reality of the laryngoscopy rather than a prediction, guiding the immediate choice of aid (a bougie for a grade-3 view, escalation to videolaryngoscopy or a supraglottic airway for grade 4) and warning future anaesthetists of difficulty. Its limitations are that it depends on the operator, the blade and the manoeuvres used (external laryngeal pressure or a different position can improve the grade), and that it describes only the view, not the ease of actually passing the tube — so it is always documented together with how the view was obtained and how intubation was ultimately achieved.
⚠️Do not treat a poor Cormack–Lehane view as a reason for repeated forceful attempts: optimise the view once (position, external laryngeal manipulation, videolaryngoscope, bougie) and, if intubation still fails, move on through the difficult-airway algorithm while keeping the patient oxygenated, because repeated laryngoscopy causes the trauma that turns difficulty into disaster.Graded at laryngoscopy — unlike Mallampati which is a bedside predictor. Grade View at laryngoscopy Difficulty 1 Full glottis visible Easy 2 Posterior glottis / arytenoids only Usually easy 3 Epiglottis only Difficult 4 No glottic structures; soft palate only Very difficult 🔑KEY POINTS TO REMEMBER- Cormack–Lehane = the actual laryngoscopic view (not a bedside prediction).
- 1 full glottis → 2 posterior glottis → 3 epiglottis only → 4 neither.
- Grades 3–4 = difficult intubation; grade 3 is the classic bougie situation.
- Complements Mallampati (which predicts before laryngoscopy).
📚SOURCES: Morgan & Mikhail’s Clinical Anesthesiology; Miller’s Anesthesia; Ajay Yadav’s Short Textbook of Anaesthesia.Description
The endotracheal (tracheal) tube is a curved tube, usually of PVC, passed through the larynx into the trachea. It has a bevelled tip, a Murphy eye (a side hole near the tip to allow ventilation if the end is occluded), an inflatable cuff with a pilot balloon (in adult tubes) to seal the trachea, and a 15 mm connector for the breathing system.
Sizes & Cuff
Tubes are sized by internal diameter (mm): roughly 7.0–8.0 for women and 8.0–9.0 for men; in children, size ≈ age/4 + 4 (uncuffed) as a guide. The cuff seals the airway (allowing positive-pressure ventilation and protecting against aspiration); it should be a high-volume, low-pressure cuff and inflated to just seal without excessive pressure. Traditionally uncuffed tubes were used in young children.
💡Cuff pressure matters: an over-inflated cuff (> ~30 cmH₂O) can cause tracheal mucosal ischaemia and later stenosis, so use the minimum pressure that seals and monitor it during long cases.Special Tubes
Variants include reinforced (armoured) tubes (resist kinking — head/neck surgery, prone), RAE preformed tubes (for oral/nasal head-and-neck surgery), double-lumen tubes (one-lung ventilation in thoracic surgery), and microlaryngeal tubes.
Checking & Securing the Tube
Before use, the tube’s cuff is checked for leaks and the connector seated firmly; after placement it is secured at the appropriate depth (around 21–23 cm at the teeth in adults) and its position confirmed, since a tube advanced too far enters a bronchus and one withdrawn too far may slip out of the larynx. During the case the cuff pressure and tube position are rechecked, particularly after any change in the patient’s position, because flexion and extension of the neck move the tube tip within the trachea.
💡Size and secure the tube with care: internal diameter roughly 7–8 mm in women and 8–9 mm in men (child ≈ age/4 + 4), a high-volume low-pressure cuff inflated only until it seals, and depth checked after any change in head position, since neck flexion advances the tube tip.Excess cuff pressure causes mucosal ischaemia and stenosis. Parameter Formula (child over 1 year) Internal diameter (uncuffed) Age ÷ 4 + 4 mm Internal diameter (cuffed) Age ÷ 4 + 3.5 mm Oral length Age ÷ 2 + 12 cm Nasal length Age ÷ 2 + 15 cm Cuff pressure Keep below 25 cmH₂O 🔑KEY POINTS TO REMEMBER- Tracheal tube: bevel, Murphy eye, inflatable cuff + pilot balloon, 15 mm connector.
- Sized by internal diameter: ~7–8 (women), 8–9 (men); child ≈ age/4 + 4.
- High-volume low-pressure cuff seals airway; avoid over-inflation (mucosal ischaemia/stenosis).
- Special tubes: reinforced (anti-kink), RAE (preformed), double-lumen (one-lung ventilation).
📚SOURCES: Morgan & Mikhail’s Clinical Anesthesiology; Miller’s Anesthesia; Ajay Yadav’s Short Textbook of Anaesthesia.Purpose
Oropharyngeal and nasopharyngeal airways are simple airway adjuncts that hold the upper airway open by preventing the tongue falling back against the posterior pharyngeal wall — the commonest cause of airway obstruction in the unconscious patient. They are used with a face mask to aid ventilation.
Oropharyngeal (Guedel) Airway
A rigid, curved plastic device inserted over the tongue into the oropharynx. It is sized from the incisors to the angle of the mandible. Because it stimulates the gag reflex, it is only tolerated in the deeply unconscious patient — in a lightly anaesthetised or semi-conscious patient it can provoke gagging, vomiting or laryngospasm.
Nasopharyngeal Airway
A soft tube passed through the nostril into the nasopharynx, sized from the nostril to the tragus of the ear. It is better tolerated in the semi-conscious patient than an oral airway. It is avoided in base-of-skull fracture (risk of intracranial placement) and used cautiously where there is coagulopathy (epistaxis).
💡Choose by conscious level: the rigid oropharyngeal (Guedel) airway for the deeply unconscious (it triggers the gag reflex), and the soft nasopharyngeal airway for the semi-conscious — but avoid the nasal route with a suspected base-of-skull fracture.Complications of Adjuncts
Although simple, these adjuncts have hazards: an oropharyngeal airway that is too large can push the epiglottis down and worsen obstruction or provoke laryngospasm, while one that is too small is ineffective; a nasopharyngeal airway can cause epistaxis and, in the presence of a base-of-skull fracture, has been reported to pass intracranially. They are therefore correctly sized, inserted gently, and chosen with the patient’s conscious level and injuries in mind, and they never substitute for proper positioning and jaw support.
💡Pick the adjunct by conscious level — Guedel for the deeply unconscious, nasopharyngeal for the semi-conscious — size it correctly, and never pass a nasal airway when a base-of-skull fracture is suspected.⚠️An incorrectly sized oropharyngeal airway is worse than none: too long it can reach the larynx and provoke laryngospasm or push the epiglottis over the glottis, too short it folds the tongue back and worsens obstruction — so it is always measured (incisors to the angle of the mandible) before insertion.Oropharyngeal airway in a semi-conscious patient provokes laryngospasm. 🔑KEY POINTS TO REMEMBER- Adjuncts hold the airway open by preventing the tongue obstructing the pharynx.
- Oropharyngeal (Guedel): sized incisors–mandibular angle; only for the deeply unconscious (gag reflex).
- Nasopharyngeal: sized nostril–tragus; better tolerated when semi-conscious.
- Avoid nasopharyngeal airway in base-of-skull fracture; caution with coagulopathy.
📚SOURCES: Morgan & Mikhail’s Clinical Anesthesiology; Miller’s Anesthesia; Ajay Yadav’s Short Textbook of Anaesthesia.Definition & Indication
Cricothyroidotomy (front-of-neck access) is an emergency surgical airway created through the cricothyroid membrane (between the thyroid and cricoid cartilages). It is the final, life-saving step in the ‘can’t intubate, can’t oxygenate’ (CICO) emergency — when a patient cannot be intubated and cannot be oxygenated by mask or supraglottic airway.
Technique
The cricothyroid membrane is identified, and access gained by a surgical (scalpel–bougie–tube) technique or a cannula technique, to deliver oxygen to the trachea below the obstruction. The scalpel technique (a stab incision through the membrane, a bougie passed, and a small tracheal/tracheostomy tube railroaded) is now the recommended definitive emergency method in adults. It is a temporary measure to restore oxygenation until a definitive airway is secured.
⚠️Cricothyroidotomy is a last-resort, time-critical procedure — in a CICO emergency it must be performed without delay once other options have failed, as the patient is profoundly hypoxic. Hesitation is the main cause of a bad outcome.💡Locate the cricothyroid membrane in the midline just below the thyroid cartilage (‘Adam’s apple’); it is relatively avascular and superficial, which is why it — rather than a formal tracheostomy — is used for emergency front-of-neck access.Complications & Aftercare
Even when successful, an emergency cricothyroidotomy is associated with complications — bleeding, misplacement, injury to the larynx or oesophagus, and later subglottic stenosis — which is why it is a bridge to a definitive airway (formal tracheostomy or intubation) arranged as soon as the patient is oxygenated and stabilised. Regular training on manikins is emphasised because the procedure is rare, stressful and time-critical, and familiarity with the equipment and landmarks is what allows it to be done quickly when it is needed.
💡In a can’t-intubate-can’t-oxygenate crisis the decision to cut the neck must be made early and without hesitation: find the cricothyroid membrane in the midline below the thyroid cartilage and use the scalpel–bougie–tube technique to restore oxygen.The final step of the difficult airway algorithm — do not delay. 🔑KEY POINTS TO REMEMBER- Emergency surgical airway through the cricothyroid membrane for the CICO situation.
- Final step of the difficult-airway algorithm when intubation AND oxygenation both fail.
- Scalpel–bougie–tube technique is the recommended adult method; a temporary rescue.
- Time-critical — perform without hesitation; convert to a definitive airway later.
📚SOURCES: Morgan & Mikhail’s Clinical Anesthesiology; Miller’s Anesthesia; Ajay Yadav’s Short Textbook of Anaesthesia.Definition & Criteria
Extubation is the removal of the tracheal tube at the end of anaesthesia. It is a high-risk period (comparable to induction) and is performed only when the patient can protect and maintain their own airway. Criteria include adequate reversal of muscle relaxation (sustained head-lift, adequate tidal volume), return of protective airway reflexes, adequate oxygenation and spontaneous ventilation, and the patient being either fully awake or (in a planned ‘deep’ extubation) adequately deep.
Technique & Complications
The airway is suctioned, the patient pre-oxygenated, the cuff deflated and the tube removed, usually with the patient awake (safer where aspiration is a risk). Complications include laryngospasm, airway obstruction, aspiration, coughing/hypertension, desaturation, and — in children — post-extubation croup (subglottic oedema).
💡Extubation is safest when the patient is either fully awake or adequately deep — extubating in the intermediate light (stage II) plane invites laryngospasm. In aspiration-risk patients, extubate awake with airway reflexes restored.Awake versus Deep Extubation
The choice between an awake and a deep extubation balances competing risks: awake extubation, once protective reflexes have returned, is safest where aspiration is a concern and is the rule for the full-stomach or difficult airway, but it is associated with more coughing and haemodynamic disturbance; deep extubation, performed while the patient is still adequately anaesthetised, produces a smoother emergence and is sometimes chosen (for example where coughing is undesirable) but leaves the airway unprotected until reflexes return. Whichever is chosen, the intermediate light plane is avoided, and equipment for reintubation is kept ready.
💡Extubate awake or deep, never in between; in any patient at risk of aspiration, wait until fully awake with airway reflexes restored, and keep reintubation equipment to hand.⚠️The commonest serious extubation problems — laryngospasm, obstruction and aspiration — all cluster in the light plane and in the unprotected airway, so the safe habits are to extubate awake in the at-risk patient, to have suction and reintubation equipment ready, and to continue oxygen and close observation into the recovery room.Extubation carries risks comparable to intubation. 🔑KEY POINTS TO REMEMBER- Extubation = removing the tube; a high-risk period like induction.
- Criteria: reversed relaxation (head-lift, tidal volume), airway reflexes, adequate oxygenation/ventilation.
- Suction, preoxygenate, deflate cuff, remove — awake in aspiration-risk patients.
- Complications: laryngospasm, obstruction, aspiration, desaturation, paediatric croup.
📚SOURCES: Morgan & Mikhail’s Clinical Anesthesiology; Miller’s Anesthesia; Ajay Yadav’s Short Textbook of Anaesthesia.Importance
Confirming tracheal tube placement immediately after intubation is essential, because an unrecognised oesophageal intubation is rapidly fatal. Confirmation uses a combination of signs, of which capnography is the most reliable.
Methods
The gold standard is capnography — a sustained end-tidal CO₂ waveform over several breaths confirms tracheal placement (an oesophageal tube shows no, or only a brief, trace). Supporting signs: bilateral chest rise and equal breath sounds in both axillae, absence of sounds/gurgling over the epigastrium, misting of the tube, a normal reservoir-bag movement, and maintained oxygen saturation. Direct visualisation of the tube passing through the cords and, if needed, a fibreoptic check also confirm placement.
💡‘No trace = wrong place.’ A sustained capnograph trace is the definitive confirmation; pulse oximetry falls only late (after preoxygenation is exhausted), so it is not an early sign of oesophageal intubation.⚠️Auscultation and chest movement can mislead (e.g. in obesity or with an oesophageal tube), so never rely on clinical signs alone — capnography must be used, and if a trace cannot be obtained and oesophageal placement cannot be excluded, remove the tube.Continuous Monitoring, Not a Single Check
Confirmation of placement is not a one-off event at intubation but a continuous process: capnography monitors the tube throughout the case, and a sudden loss of the waveform demands immediate evaluation for displacement, disconnection, obstruction or a fall in cardiac output. This is why continuous waveform capnography is now regarded as a minimum standard whenever a tracheal tube or supraglottic airway is used, both in the operating theatre and in the intensive care unit and during transfer.
💡Trust the waveform, not the stethoscope: a sustained end-tidal CO₂ trace is the definitive proof of tracheal placement, oximetry falls only late, and continuous capnography then guards the tube for the rest of the case.⚠️Clinical signs can deceive — chest movement and breath sounds may seem present with an oesophageal tube, especially in the obese — so capnography is mandatory, and a flat trace that cannot be explained means the tube is presumed misplaced and removed rather than left in on the strength of auscultation.Sustained capnograph trace over several breaths is the gold standard. 🔑KEY POINTS TO REMEMBER- Confirm every tube — unrecognised oesophageal intubation is fatal.
- Capnography (sustained end-tidal CO₂) is the gold standard: ‘no trace = wrong place’.
- Support: bilateral chest rise/breath sounds, no epigastric sounds, tube misting, maintained SpO₂.
- Don’t rely on clinical signs alone; SpO₂ falls late; if in doubt, take it out.
📚SOURCES: Morgan & Mikhail’s Clinical Anesthesiology; Miller’s Anesthesia; Ajay Yadav’s Short Textbook of Anaesthesia.