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Viva Questions on Laryngoscope — Comprehensive Guide

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1. What is a laryngoscope? What are its components?

• Handle — holds the power source (batteries); held in the left hand during use
• Blade — inserted into the mouth; comes in curved (Macintosh) and straight (Miller) designs
• Light source — either a conventional bulb at the tip of the blade or a fibre-optic system transmitting light from the handle
• Flange — along the left side of the blade; used to sweep the tongue to the left
• Hook/locking mechanism — connects blade to handle at a right angle (when engaged, activates the light)

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2. What are the types of laryngoscope blades?

Curved Blades

Straight Blades

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3. What is the difference between Macintosh and Miller blades?

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4. What is the technique of direct laryngoscopy?

1. Patient in "sniffing position" (head extended, neck flexed) — aligns oral, pharyngeal, and laryngeal axes
2. Laryngoscope held in the left hand
3. Blade inserted from the right side of the mouth, avoiding teeth and lips
4. Tongue swept to the left and compressed into the mandibular space
5. Macintosh: advance tip into the vallecula → lift in an anterior-caudad direction
6. Miller: advance tip under the epiglottis → directly lift
7. Lift is directed at 45° toward the junction of the opposite wall and ceiling — never lever on the teeth
8. Vocal cords visualized → ETT passed under direct vision

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5. What is the "sniffing position"? Why is it important?

• Oral axis
• Pharyngeal axis
• Laryngeal axis

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6. What are the blade sizes?

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7. What are video laryngoscopes? Name types.

• GlideScope (Verathon) — hyperangulated blade; most studied
• C-MAC (Karl Storz) — blade similar to Macintosh; allows both direct and video laryngoscopy; instructors can see the operator's view
• McGrath Series 5 (Teleflex)
• Airtraq — optical laryngoscope with channel for ETT

• Higher first-pass success in difficult airways
• No strict axis alignment needed
• Teaching tool (assistants can view simultaneously)

• May fail if lens obscured by blood/vomitus — avoid in cases with copious emesis
• Device failure possible
• Skill set slightly different from DL

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8. What are the indications and contraindications of direct laryngoscopy?

• Any situation requiring a definitive emergency airway
• Routine and difficult elective intubations
• RSI (rapid sequence intubation)

• Limited mouth opening (trismus, TMJ ankylosis)
• Upper airway distortion or swelling (epiglottitis, angioedema, abscess)
• Severe kyphosis/cervical spine instability
• Copious blood or secretions (consider video laryngoscopy or awake fibreoptic instead)

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9. What is the BURP maneuver? What is ELM?

• BURP (Backward, Upward, Rightward Pressure) — applied externally on the thyroid cartilage; improves glottic visualization during laryngoscopy
• ELM (External Laryngeal Manipulation) — operator's own right hand applies external pressure on the larynx to optimize the view, then an assistant maintains that pressure
• Cricoid pressure (Sellick's maneuver) — backward pressure on cricoid ring to compress oesophagus; used to prevent regurgitation during RSI (its routine use is now debated)

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10. What is the light source in a laryngoscope?

• Conventional/Standard: Small bulb at the tip of the blade; can be replaced; may slightly hamper vision
• Fibre-optic: Light transmitted via optical fibres from the handle; provides brighter, shadow-free illumination; no bulb at tip; easier sterilization
• LED: Modern option; brighter, longer lasting
• Studies (Levitan) show that blade brightness is frequently inadequate — only 24% of Macintosh blades in one ED survey met the brightness needed for fine inspection. The G-Mac (German design) provides the best brightness; A-Mac (American) the least.

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11. What nerve is at risk with straight blade laryngoscopy?

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12. What is the Cormack-Lehane grading?

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13. What are common errors during laryngoscopy?

• Blade placed under the middle of the tongue (tongue not swept left)
• Tongue not pushed far enough to the left, obscuring glottis
• Levering on upper teeth (risk of dental damage)
• Advancing Miller blade into the oesophagus
• Insufficient blade brightness
• Incorrect patient positioning

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14. What is a McCoy laryngoscope?

• Anterior airways
• Patients with limited cervical spine movement
• When Cormack-Lehane grade III is encountered with standard Macintosh

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15. Macintosh blade — preferred in which situations?

• Uncomplicated adult intubations (standard of care)
• Small mouth (less room needed for ETT passage)
• Patients with prominent upper teeth (less dental trauma)
• When more space is needed to pass the ETT through the oropharynx

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16. Miller blade — preferred in which situations?

• Pediatric patients (especially < 2–6 years; superior POGO scores vs Macintosh)
• Anterior larynx
• Long, floppy epiglottis
• Small mandibular space
• Large incisors
• Larynx fixed by scar tissue

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17. What material are laryngoscope blades made of?

• Stainless steel — durable, corrosion-resistant, most common for reusable blades
• Chrome-plated brass — smooth finish, cost-effective
• Plastic (disposable) — single-use; reduces cross-contamination; higher long-term cost

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18. Disposable vs reusable blades — what are the considerations?

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Summary Mnemonic: "MAC MILKS"

• Macintosh — curved, vallecula, indirect epiglottis lift
• Adult preferred for uncomplicated airways
• C-MAC / GlideScope — video laryngoscopes
• Miller — straight, under epiglottis, direct lift
• Infants/pediatric — use straight (Miller)
• Laryngospasm risk — with straight blade (SLN stimulation)
• Keys: sniffing position, left hand, sweep tongue left, 45° lift
• Sizes: Mac 1–4, Miller 0–3

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Goal-Directed Fluid Therapy (GDFT) in the Perioperative Period

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1. Definition and Concept

"GDFT aims to avoid both hypovolemia and fluid excess, and it is the optimal approach for fluid administration in high-risk surgical patients." — Morgan & Mikhail's Clinical Anesthesiology, 7e

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2. Physiological Basis — The Frank-Starling Curve

• Increasing preload (ventricular filling) increases stroke volume — up to a plateau
• On the steep ascending limb: patients are fluid-responsive (a bolus will increase stroke volume)
• On the flat portion: additional fluid will not increase stroke volume but will cause fluid overload

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3. Why Conventional Fixed-Volume Strategies Are Inadequate

• AKI occurred more frequently in the restrictive group
• Despite more fluid in the liberal group, 24-hour weight gain was < 2 kg with no worse outcomes
• Target: positive fluid balance of 1–2 L at end of surgery using isotonic balanced crystalloid

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4. Parameters Used in GDFT

A. Dynamic Parameters (Preferred — predict fluid responsiveness)

"As volume is administered, pulse pressure variation decreases. Variation greater than 12–13% is suggestive of fluid responsiveness." — Morgan & Mikhail's Clinical Anesthesiology, 7e

B. Static Parameters (Less Reliable)

C. Limitations of Dynamic Parameters

• Patient is mechanically ventilated with controlled PPV (not spontaneously breathing)
• Sinus rhythm is present (atrial fibrillation/ectopy artificially elevates variation)
• Tidal volume ≥ 8 mL/kg (low tidal volumes reduce reliability)
• Abdomen is closed (open chest abolishes predictive value)
• Deep sedation/paralysis present (patient not breathing out of sync with ventilator)

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5. Monitoring Devices Used in GDFT

"Studies of esophageal Doppler-guided strategies found no difference in intraoperative fluid or vasopressor totals, but beneficial effects were attributed to fluid administration at the right time." — Perioperative Fluid Management Review, BINASSS 2025

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6. GDFT Protocol — Step-by-Step Algorithm

Baseline: IV balanced crystalloid 3 mL/kg/h
            ↓
   Assess fluid responsiveness
   (SVV/PPV > 12–13%? or SV < optimum?)
            ↓
        YES                    NO
         ↓                      ↓
Fluid bolus 250–500 mL      No additional fluid
(colloid or balanced         Consider vasopressor
 crystalloid)                 if MAP < 65 mmHg
         ↓
Re-assess: SV increase ≥ 10%?
    YES → repeat bolus        NO → stop fluids
                                   Add vasopressor/
                                   inotrope if needed

• Vasopressors (norepinephrine): correct anaesthesia-induced vasodilatation and prevent excess fluid administration
• Inotropes: improve cardiac contractility when preload is optimised but CO remains low
• Secondary goal: MAP ≥ 65 mmHg; Indexed oxygen delivery (DO₂I) > 600 mL/min/m²

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7. Fluid Types Used in GDFT

• Crystalloid: 1.5:1 (crystalloid : blood lost)
• Colloid: 1:1

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8. GDFT in the Context of ERAS (Enhanced Recovery After Surgery)

• In a well-implemented ERAS pathway, GDFT does not confer additional benefit over conventional management in low-moderate risk patients
• This is because ERAS already minimises fluid shifts (minimally invasive surgery, encouraged oral hydration during fasting, early postoperative oral intake)
• GDFT guided by cardiac output monitoring is reserved for:
  • High-risk patients
  • Major surgical procedures
  • Expected blood loss > 1000 mL

"The use of goal-directed fluid therapy guided by cardiac output monitoring is appropriate in high-risk patients undergoing major surgical procedures in whom the expected blood loss is greater than 1000 mL." — Current Surgical Therapy, 14e

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9. Perioperative Phases of GDFT

Preoperative

• Identify high-risk patients (ASA ≥ 3, cardiac/renal comorbidities, major surgery)
• Optimise fluid status (encourage oral fluids up to 2 h before surgery per enhanced fasting)
• Establish baseline hemodynamics

Intraoperative

• Baseline crystalloid infusion: 3–5 mL/kg/h
• Guide boluses by dynamic parameters (SVV, PPV, SV response)
• Replace blood loss per 1:1.5 (crystalloid) or 1:1 (colloid) ratios
• Maintain MAP ≥ 65 mmHg; add vasopressors for vasodilatory hypotension
• Target zero-to-slightly-positive fluid balance in ERAS cases

Postoperative

• Continue hemodynamic monitoring in high-risk patients (ICU/HDU)
• De-escalate monitoring as patient stabilises
• Early oral intake encouraged in ERAS pathways
• The "four-phase approach" (Resuscitation → Optimisation → Stabilisation → De-escalation) emphasises that fluid therapy is dynamic and must be frequently reassessed

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10. Benefits of GDFT (Evidence Summary)

"Results of multiple meta-analyses suggest the benefits of GDFT may be less in optimisation of fluid responsiveness but more in optimising tissue and organ perfusion." — Perioperative Fluid Management Review, 2025

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11. Limitations and Controversies

• Evidence is inconsistent across trials — heterogeneous protocols, variable patient populations
• Less benefit in laparoscopic/robotic procedures with minimal physiological trespass
• Dynamic parameters require specific conditions to be valid (see Section 4C)
• Not all patients benefit — risk stratification is essential
• Resource-intensive: requires advanced monitoring equipment and trained personnel
• PVI (non-invasive pleth variability index) shows promise but evidence is still evolving (Felippe et al., 2025 — Meta-analysis, PMID 40778974)

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12. Summary Table

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