High-Yield Topics for DNB Anesthesia Theory - June 2026

10 Highest-Yield Topics (Based on Actual Past Papers)

1. Neuromuscular Blockade - Reversal & Monitoring

2. Obstetric Emergencies (PIH / Emergency LSCS / Labour Analgesia)

• Emergency LSCS in a PIH patient with fetal distress (spinal vs. GA)
• Labour analgesia (epidural, CSE, remifentanil PCA)
• Anesthesia for antepartum hemorrhage / placenta previa

3. Cardiac Patient for Non-Cardiac Surgery

4. Pediatric / Neonatal Anesthesia - TEF / Pyloric Stenosis

5. One-Lung Ventilation (OLV) & Thoracic Anesthesia (VATS)

6. Fluid Therapy - Goal-Directed, Fluid Responsiveness, Ultrasound

7. Neuroanesthesia - ICP Management / Awake Craniotomy / Prone Position Surgery

8. Pacemakers & ICDs - Perioperative Management

9. Airway Management - Difficult Airway / Supraglottic Airways (2nd Generation)

10. Regional Anesthesia - Ultrasound-Guided Nerve Blocks + PDPH Management

Bonus Topics (Very High Frequency)

How DNB Theory Papers Are Structured

1. Clinical scenarios - A patient with comorbidity posted for surgery (assess + plan)
2. Short notes (a + b) - Two short topics per question (4+6 or 5+5 marks)

Preparation Strategy

• Get actual papers from NBE website - they are publicly available
• Study the May 2024, Oct 2024, and Dec 2025 papers in detail
• Use Miller's Anesthesia + Morgan & Mikhail for core content
• For each topic: pathophysiology (2 lines) → preop assessment → intraop management → postop care

Post-Extubation Stridor

Definition

Pathophysiology

• Mucosal ischemia from cuff pressure
• Local inflammation and edema
• Increased airway resistance

Risk Factors

• Female sex (narrower subglottis)
• Obesity
• Prolonged intubation (>7 days in ICU patients)
• Previous episode of PES
• History of difficult or traumatic intubation / multiple intubation attempts
• Head and neck surgery or trauma
• Rheumatoid arthritis (cricoarytenoid involvement)
• Prone positioning / steep Trendelenburg with large volume fluid resuscitation (causes pharyngolaryngeal edema)

• Large ETT relative to the patient's size (tube-to-trachea ratio too high)
• Excessively high cuff pressure
• Cuff positioned too close to the vocal cords
• Excessive patient movement while intubated (tracheal injury from tube movement)

Causes of Post-Extubation Airway Obstruction (Differential)

Cuff Leak Test (CLT)

1. Suction the oral cavity and trachea
2. Deflate the ETT cuff
3. A cuff leak = air audibly or measurably escapes around the tube during positive pressure ventilation

• Absent cuff leak = ~30% risk of PES (Harrison's)
• A failed CLT is the trigger for pre-emptive dexamethasone therapy
• Quantitative CLT: cuff leak volume <110 mL (measured by spirometry) predicts PES with reasonable accuracy
• Limitations: does not reliably rule out significant laryngeal edema in non-ICU, intraoperative patients (Barash)

Prevention

• Multi-dose protocol is effective - e.g., dexamethasone 0.1-0.2 mg/kg IV q8h for 24 hours before extubation in high-risk patients who have failed CLT
• A single dose given 1 hour before extubation alone does not reduce reintubation rates (Barash, RCT evidence)
• Pediatric protocol (Harriet Lane): dexamethasone for 24 hours when cuff leak is absent at <30 cmH2O delivered pressure

• Use the appropriate ETT size (7.0 for most adult females, 7.5-8.0 for males as a rough guide; smaller in children by age-based formula)
• Maintain cuff pressure 20-30 cmH2O
• Minimize duration of intubation
• Careful technique on intubation - avoid multiple attempts

Treatment

Step-by-step management:

• Humidified oxygen via face mask or nasal cannula
• Sit the patient up (reduces venous pooling, edema)

• Mechanism: alpha-1 agonist causes local mucosal vasoconstriction → reduced edema
• Onset: rapid (minutes)
• Duration: 30-60 minutes - monitor for rebound edema (observe for at least 2-4 hours after administration)
• L-epinephrine (1:1000, 5 mL) is equally effective if racemic form not available

• Dexamethasone 0.1 mg/kg IV (or 4-8 mg in adults)
• Mechanism: reduces vascular permeability and inflammatory response
• Onset: delayed (hours) compared to epinephrine
• Used alongside epinephrine for more sustained effect

• Helium is less dense than nitrogen → reduces turbulent flow resistance in the narrowed airway
• Provides symptomatic relief and buys time for definitive treatment
• Does NOT treat the underlying edema - strictly a temporizing measure
• Works best when FiO2 requirement is low (needs at least 70% helium to be effective)

• Useful when IV access is unavailable or patient is vomiting
• Especially used in pediatric croup settings

• If the above measures fail or if the patient is deteriorating (SpO2 falling, increasing work of breathing, fatigue)
• Use a tube 0.5-1 size smaller than previously used
• Extubation over an airway exchange catheter (AEC) is advisable when reintubation is anticipated to be difficult - allows railroading

Special Populations

• More vulnerable due to smaller airway radius (Poiseuille effect)
• Differential includes croup, epiglottitis, foreign body, bacterial tracheitis
• Racemic epinephrine + dexamethasone is the mainstay
• Observe for minimum 2-4 hours after racemic epinephrine before discharge

• High risk for pharyngolaryngeal edema from positional venous congestion + large volume fluids
• Sit patient up during emergence
• Low threshold for CLT and keeping intubated postoperatively

• Rule out hematoma (expanding neck, tracheal deviation)
• Hematoma requires urgent wound opening at bedside if airway is compromised

• Failed CLT after >7 days intubation warrants methylprednisolone 20-40 mg IV q4h for 12 hours before extubation (protocol varies)

Summary Algorithm

Post-extubation stridor
        |
Assess severity
        |
   Mild-moderate                          Severe / deteriorating
(audible, SpO2 preserved)            (SpO2 falling, fatigue, distress)
        |                                         |
Sit up + Humidified O2                     Call for help
Nebulized racemic epinephrine              Prepare for reintubation
IV Dexamethasone                           Racemic epi + Heliox as bridge
Heliox if available                        Intubate (smaller ETT)
        |                                  (consider AEC or surgical airway)
Monitor 2-4 hours
Reassess

• PES manifests within 30 minutes of extubation
• Most common cause: subglottic/laryngeal edema
• Cuff leak absent = ~30% risk of PES
• Racemic epinephrine works by local vasoconstriction - beware rebound edema
• Multi-dose dexamethasone pre-emptively works; single-dose alone does not reduce reintubation
• Heliox = density reduction - temporizing, not curative
• Resistance ∝ 1/r⁴ (laminar flow) and 1/r⁵ (turbulent flow in children)

Pneumoperitoneum: Systemic Changes in Laparoscopic Cholecystectomy

Introduction

1. Mechanical effects - raised intra-abdominal pressure (IAP)
2. Biochemical effects - systemic CO2 absorption

1. Cardiovascular System

Mechanism Summary Table (Barash Clinical Anesthesia 9e)

What actually happens:

• At IAP <10 mmHg: IVC compression initially reduces venous return and CO
• Splanchnic organ compression pushes blood centrally, initially raising venous return
• Net effect: biphasic - brief initial rise then fall in venous return
• Reverse Trendelenburg in lap chol (unlike head-down in pelvic laparoscopy) further reduces preload because blood pools in the lower limbs

• Initial ~30% decrease in CO with pneumoperitoneum
• Recovers toward baseline over the next 10 minutes as neurohumoral compensation kicks in
• IAP >20 mmHg: severe IVC compression, CO falls sharply

• IAP compresses the aorta → direct mechanical increase in SVR
• CO2 absorption → sympathetic activation, catecholamine release, vasopressin release → further ↑ SVR
• Renin-angiotensin system activated → angiotensin II → vasoconstriction
• Net result: ↑ SVR, ↑ MAP, ↑ myocardial oxygen demand
• Despite falling CO, BP often remains normal or rises due to ↑ SVR - a deceptive compensation

• Peritoneal stretch/irritation activates autonomic nerve fibers
• Sympathetic activation → noradrenaline release → ↑ HR, ↑ SVR, ↑ MAP
• Vasopressin (ADH) release → intense vasoconstriction, ↑ LV afterload, ↑ LV wall tension
• Renin-angiotensin activation → aldosterone → sodium/water retention

• Bradycardia and even asystole from vagal reflexes during peritoneal stretching (especially at insufflation)
• Hypercapnia sensitizes the myocardium to catecholamines → ventricular ectopics, tachyarrhythmias
• Severe hypercapnia (PaCO2 >55-70 mmHg) → myocardial depression + dysrhythmias

• Reduces venous return (pooling in legs) → reduces preload
• Contrast with pelvi-laparoscopy (Trendelenburg position) where venous return and CO may increase

2. Respiratory System

• CO2 is highly soluble - absorbed rapidly across the peritoneal membrane into the systemic circulation
• Initial rapid absorption in first 30-60 minutes, then plateau
• VCO2 (CO2 production) increases by 30-50% above baseline
• Absorbed CO2 must be eliminated by increasing minute ventilation (↑ RR or TV by ~25-30%)
• If ventilation cannot keep up: hypercapnia → respiratory acidosis

• Diaphragm pushed cephalad → reduced FRC and vital capacity
• ↓ Lung compliance (reduced chest wall expansion)
• ↑ Peak airway pressure (may rise 40-60% above baseline)
• Ventilation-perfusion mismatch and atelectasis, especially in obese patients
• ETT can migrate into right main bronchus due to cephalad diaphragm shift - check bilateral air entry after position change
• IAP >15 mmHg can precipitate pulmonary edema and congestion

• Keep IAP ≤ 15 mmHg for lap chol (standard)
• IAP >20 mmHg: severe respiratory and cardiovascular compromise

3. Renal System

• ↓ Renal blood flow (direct parenchymal compression + renal vein compression)
• ↑ Renin → ↑ angiotensin II → renal vasoconstriction → ↓ GFR
• ↑ ADH → water retention → oliguria
• Ureteral compression (at high IAP)
• IAP >15 mmHg associated with postoperative AKI
• Oliguria is expected during pneumoperitoneum - not necessarily a sign of hypovolemia
• Monitor: urine output >0.5 mL/kg/hr is acceptable intraoperatively

4. Central Nervous System

• ↑ Intracranial pressure (ICP) - immediate effect of pneumoperitoneum
• Mechanism: ↑ PaCO2 → cerebral vasodilation → ↑ cerebral blood flow → ↑ ICP
• Also: ↑ IAP → ↑ thoracic pressure → impairs venous drainage from brain (via raised CVP)
• ↑ Intraocular pressure (IOP)
• Important: avoid laparoscopy or use with extreme caution in patients with raised ICP
• Catecholamine release during peritoneal stimulation

5. Portal / Hepatic / Splanchnic Circulation

• ↓ Portal venous blood flow (direct compression)
• ↓ Hepatic artery flow (neurohormonal vasoconstriction)
• ↓ Mesenteric blood flow to intestines, pancreas, spleen, stomach
• Usually clinically insignificant for brief procedures
• Rarely: mesenteric thrombosis (catastrophic, delayed presentation)
• Less postoperative ileus compared to open surgery (proposed mechanism: hypercarbia effect)

6. Acid-Base Changes

• CO2 absorption → hypercapnia
• PaCO2 rises steadily unless ventilation is increased
• ETCO2 closely tracks PaCO2 in healthy patients (difference usually 3-5 mmHg)
• Respiratory acidosis if ventilation is inadequate
• In COPD patients: ETCO2 may significantly underestimate PaCO2 - arterial blood gas monitoring is mandatory for procedures >60 minutes
• After deflation: residual CO2 continues to be mobilized from tissues for 30-60 minutes → risk of post-extubation hypercapnia in COPD

7. Thromboembolic / Venous Effects

• Reverse Trendelenburg → venous pooling in lower limbs
• Femoral vein compression by raised IAP
• ↑ DVT risk (venous stasis + hypercoagulable state)
• Rare but serious: CO2 gas embolism - high index of suspicion if sudden hypotension, ↓ ETCO2, mill-wheel murmur on auscultation, CVP rise

Organ System Summary Table (Barash Table 50-5)

Anesthetic Implications

Key Exam Points

• CO decreases by ~30% initially, then recovers over 10 minutes
• SVR and MAP increase despite falling CO
• ETCO2 underestimates PaCO2 especially in COPD - always get ABG
• IAP should not exceed 15 mmHg (>20 mmHg: IVC compression, ↓ CO severely)
• Reverse Trendelenburg (lap chol position) reduces preload, unlike Trendelenburg
• Oliguria during pneumoperitoneum is expected and multifactorial (ADH, angiotensin, renal compression) - treat the cause, not the oliguria
• Shoulder tip pain = referred phrenic pain from CO2 under diaphragm
• Vagal bradycardia/asystole can occur at the start of insufflation