Q Myocardial Ischemia Under Anaesthesia 1. Diagnosis and management under GA 2. Ischemia monitoring during anaesthesia Q Cardiac Pt for Non cardiac surgery 1. DES patient for TKR 2. CAD patient for THR 3. IHD patient for laparoscopic cholecystectomy 4. Frail elderly with prior coronary stenting 5. Risk stratification in ischemic heart disease Core areas repeatedly asked • Risk assessment • Timing after stent • Antiplatelets • Beta blockers/statins • Functional capacity • Intraoperative goals Q Mitral Stenosis → Combined from 1. MS pathophysiology 2. Severe MS for LSCS 3. Severe MS for emergency appendicectomy 4. Rheumatic heart disease in pregnancy High-yield focus • Avoid tachycardia • Maintain preload • Avoid pulmonary hypertension • Sinus rhythm importance Q Non-invasive Cardiac Output Monitoring QArrhythmias + ACLS + Cardioversion → Included topics 1. Ventricular tachycardia 2. Ventricular fibrillation ACLS 3. Atrial fibrillation 4. Cardioversion 5. CCLS guidelines + good-quality CPR Q Post-cardiac Arrest Care / CPR Included 1. Post-cardiac arrest care 2. Temperature management after cardiac arrest 3. Infant vs adult CPR Q Pacemaker / ICD → Combined from 1. Permanent pacemaker for TURP 2. Classification + perioperative management of pacemaker/ICD Q ECMO → Included 1. ECMO basics 2. Role in COVID 3. General indications Q Venous Air Embolism → 2 repetitions Included 1. VAE causes/diagnosis/management 2. Air embolism + paradoxical embolism + capnography Q Hypertension / Blood Pressure → Included 1. BP definition and measurement 2. Types of hypertension 3. Hypertensive patient for surgery Q Cardiac Risk Stratification / Preoperative Evaluation → Combined from 1. Chronic smoker + HTN for THR 2. Elderly frail patient with CAD 3. CAD with DES 4. IHD for laparoscopic surgery Q Coronary Circulation / MVO₂ Included 1. Coronary circulation + ischemia monitoring 2. Regulation of coronary blood flow + determinants of myocardial oxygen consumption Answer these question for dnb practical exam from millers and latest guidelines of cpr provide consise and scoring answer for 10 marks question

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You are helping prepare DNB Anaesthesia practical exam answers. Search the medical textbook library database for content on the following topics, then write concise high-scoring 10-mark exam answers: 1. **Myocardial Ischemia Under Anaesthesia** - Diagnosis and management under GA, ischemia monitoring during anaesthesia 2. **Non-invasive Cardiac Output Monitoring** - all methods, principles, clinical use 3. **Coronary Circulation and MVO2** - coronary blood flow regulation, determinants of myocardial oxygen consumption, ischemia monitoring SEARCH INSTRUCTIONS: - First read /skills/readonly/medical-library/SKILL.md (limit=1000) - Use query_library_db with headings_fts and paragraphs_fts to find relevant sections - Search terms to use: "myocardial ischemia anaesthesia", "ischemia monitoring", "ST segment monitoring", "coronary circulation", "myocardial oxygen consumption", "cardiac output monitoring", "non-invasive cardiac output" - Read the relevant file sections using read_file with the paths returned - Also search paragraphs_fts for: "ischemia perioperative", "coronary blood flow", "MVO2", "esophageal Doppler", "pulse contour", "bioimpedance cardiac output" FORMAT REQUIRED: For each question, write a DNB exam answer structured as: - Brief intro (1-2 lines) - Numbered/bulleted points covering all key areas - Tables where appropriate - Each answer should be self-contained and score-worthy for 10 marks Return the complete text of all 3 answers.

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The subagent returned a summary but not the full answer text. I'll now directly query the library and write all answers using my knowledge from Miller's + current guidelines.

Finding Sources

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Searching PubMed

"noncardiac surgery" AND "coronary stent" AND "antiplatelet"

Searching the Web

2024 AHA ACC guidelines perioperative cardiac risk assessment noncardiac surgery DES timing antiplatelet

I now have sufficient material from Miller's Anesthesia (10e) and clinical knowledge to write all comprehensive answers. Let me compile them all.Here are all the comprehensive DNB Practical Exam answers, structured for 10-mark scoring:

DNB ANAESTHESIA — CARDIAC QUESTIONS: HIGH-YIELD EXAM ANSWERS

Q1. MYOCARDIAL ISCHEMIA UNDER ANAESTHESIA

A. DIAGNOSIS UNDER GENERAL ANAESTHESIA

Definition: Imbalance between myocardial O₂ supply and demand. Under GA, the classic symptom (chest pain) is absent — diagnosis relies entirely on monitoring.

ECG Monitoring (Primary Tool)

Lead	Sensitivity
V5 alone	75%
II alone	33%
II + V5	80%
V4 + V5	90%
II + V4 + V5	98% ← Gold standard (London et al.)

ECG Changes Diagnostic of Ischemia:

ST depression ≥1 mm (horizontal/downsloping) in ≥2 contiguous leads → subendocardial ischemia
ST elevation ≥2 mm in ≥2 contiguous leads → transmural ischemia / STEMI
New LBBB
T-wave inversion / peaked T-waves (hyperacute)
New Q waves (late, infarction)

Sequence of Ischemic Events (WCMD rule):

Wall motion abnormality → Compliance change → Metabolic → Diastolic dysfunction → ECG changes → Symptoms

TEE (most sensitive): New segmental wall motion abnormalities (SWMA) — precede ECG changes by 1-2 minutes. Regional wall motion score index used.

Other indicators:

Sudden hemodynamic deterioration (↑PCWP, ↓CO, ↑PAP)
New V-waves on PCWP tracing (papillary muscle ischemia → MR)
Troponin I/T elevation (postoperative, not intraoperative)

B. ISCHEMIA MONITORING DURING ANAESTHESIA

Monitor	Sensitivity	Notes
5-lead ECG (II + V5)	80%	Standard intraoperative monitoring
12-lead ECG	98%	High-risk cases; continuous 12-lead preferred
TEE	Highest	Gold standard for immediate ischemia detection; SWMA appears earliest
PA catheter	Moderate	↑PCWP, V waves suggest ischemia
ST-segment trend analysis	Automated; routine in high-risk

High-risk features requiring continuous ST monitoring:

Known CAD, DM, hypertension
High-risk surgery (vascular, cardiac, prolonged)
Previous MI, stent, CABG

C. MANAGEMENT OF INTRAOPERATIVE ISCHEMIA

Immediate (ABCDE):

A — Alert surgeon: Consider stopping/pausing procedure
B — Optimize O₂ supply: Increase FiO₂ to 1.0; correct anaemia (transfuse if Hb <7-8 g/dL)
C — Correct hemodynamics:
- Tachycardia → IV metoprolol 1–5 mg (target HR <70 bpm)
- Hypertension → Nitroglycerin (GTN) infusion 0.5–5 μg/kg/min
- Hypotension → Phenylephrine (preserves diastolic pressure + coronary perfusion)
- Volume status: optimize preload
D — Drugs:
- GTN: reduces preload, relieves coronary vasospasm, dilates large epicardial vessels
- Beta-blockers: reduce HR, prolong diastole, ↓MVO₂
- Volatile agents: ischemic preconditioning via KATP channels (isoflurane, sevoflurane preferred)
E — Evaluate: Continuous TEE, 12-lead ECG, obtain troponin level postop

Hemodynamic Goals (Box 29.2, Miller's):

Parameter	Target
Heart rate	50–70 bpm
MAP	70–90 mmHg
Hematocrit	>28%
PCWP	10–15 mmHg
Avoid	Tachycardia, hypertension, hypotension, hypovolemia

Post-ischemic event:

Rule out STEMI: 12-lead ECG stat
If STEMI under GA: emergent cardiology consult → consider PCI
ICU/HDU postoperatively for monitoring; serial troponins at 6h, 12h, 24h

Q2. CARDIAC PATIENT FOR NON-CARDIAC SURGERY

A. RISK STRATIFICATION — ACC/AHA 2014 (Updated 2024 Focused Update)

Step-wise Approach:

Step 1 — Emergency surgery? → Proceed, risk stratify postoperatively.

Step 2 — Active cardiac conditions? (Unstable angina, decompensated HF, severe arrhythmia, severe valvular disease) → Postpone, treat first.

Step 3 — Low-risk surgery? (Minor: cataract, endoscopy, superficial) → Proceed without testing.

Step 4 — Functional Capacity ≥4 METs without symptoms?

Activity	METs
Self-care, dressing	1
Walking on level ground	2–3
Climbing one flight of stairs	4 ← threshold
Running, strenuous sports	>10

→ ≥4 METs without symptoms: proceed to surgery → <4 METs or unknown: assess surgical risk + RCRI

Step 5 — Revised Cardiac Risk Index (RCRI / Lee Index):

Risk Factor	Score
High-risk surgery	1
Ischaemic heart disease	1
Congestive heart failure	1
Cerebrovascular disease	1
Diabetes on insulin	1
Creatinine >2 mg/dL	1

0–1: <1% MACE risk → Proceed
2: ~2.4% MACE → Consider stress testing if it will change management
≥3: >5.4% MACE → Consider cardiology referral; pharmacological stress testing

Surgical Risk Categories:

Risk	Examples	MACE risk
Low (<1%)	Laparoscopic cholecystectomy, ophthalmic	<1%
Intermediate (1–5%)	Intraabdominal, thoracic, orthopaedic (TKR/THR)	1–5%
High (>5%)	Aortic/vascular, emergency surgery	>5%

B. SPECIFIC CLINICAL SCENARIOS

1. DES Patient for TKR

Core Issue: Timing of surgery after DES

Stent Type	Minimum Wait	Preferred Wait
Bare Metal Stent (BMS)	30 days	3 months
Drug-Eluting Stent (DES) — old gen	12 months	12 months
DES — new gen (everolimus/zotarolimus)	6 months	6 months (ACC/AHA 2024)
Balloon angioplasty (no stent)	14 days	14 days

Why? Risk of in-stent thrombosis if DAPT stopped prematurely.

Antiplatelet Management for TKR (elective):

TKR = intermediate bleeding risk
If within mandatory window: defer surgery if possible
If surgery cannot wait (urgent): continue aspirin throughout; stop clopidogrel/ticagrelor 5–7 days before; bridge with short-acting antiplatelet (e.g. cangrelor/tirofiban) NOT heparin
Restart DAPT within 24–48 h postoperatively
Consult cardiology + surgeon jointly

Intraoperative Targets:

Avoid tachycardia, hypotension, hypoxaemia
Tourniquet use → careful monitoring for ischemia on release
Regional anaesthesia preferred (GA acceptable)

2. CAD Patient for THR

Assessment: RCRI scoring + functional capacity

THR = intermediate-risk surgery (1–5% MACE)
If well-controlled, stable CAD + functional capacity ≥4 METs → proceed
Optimize: beta-blockers (continue perioperatively), statins (continue, do not stop)

Perioperative Beta-blocker Strategy (POISE trial caveats):

If already on beta-blocker: continue (abrupt cessation → rebound tachycardia → ischemia)
New initiation: only if ≥3 RCRI risk factors; start >24 h before surgery; do not start on day of surgery (POISE trial: ↑stroke risk)
Statins: Continue perioperatively; pleiotropic stabilisation of plaques

Intraoperative:

Spinal/epidural preferred for THR (reduces DVT, blood loss, PE)
Maintain MAP > 65 mmHg (coronary perfusion)
Avoid: hypotension on cement insertion (cement implantation syndrome — vasodilation)
Phenylephrine or ephedrine for hypotension

3. IHD Patient for Laparoscopic Cholecystectomy

Risk: Laparoscopic cholecystectomy = low–intermediate risk. IHD does not contraindicate laparoscopy.

Specific Laparoscopy Concerns in IHD:

Factor	Effect	Management
CO₂ pneumoperitoneum	↑Afterload, ↑SVR, ↑PaCO₂ → ↑HR	IAP <12 mmHg; hyperventilate
Head-up tilt (reverse Trendelenburg)	↓Venous return, ↓preload	Volume loading
CO₂ absorption	Hypercapnia → tachycardia, arrhythmia	EtCO₂ monitoring, adjust ventilation
Vagal stimulation (gallbladder manipulation)	Bradycardia	Atropine ready

Intraoperative monitoring: 5-lead ECG, ST analysis, NIBP every 3–5 min, SpO₂, EtCO₂

Specific Goals:

IAP ≤12 mmHg (reduce hemodynamic impact)
Maintain normocarbia (EtCO₂ 35–40)
Avoid excessive Trendelenburg/head-up
Consider arterial line if severe IHD

4. Frail Elderly with Prior Coronary Stenting

Frailty Assessment (Clinical Frailty Scale / FRAIL score):

Frailty independently predicts 30-day MACE and postoperative morbidity beyond RCRI
Use: CFS (Clinical Frailty Scale) — score ≥5 = frail
Tools: grip strength, gait speed, Fried criteria

Perioperative Plan:

Preoperative: Cardiology review; confirm DAPT compliance; echocardiography if not recent; nutritional optimisation; physiotherapy prehabilitation
Anaesthetic technique: Favour regional/neuraxial; avoid deep anaesthesia (BIS 40–60); minimal polypharmacy
Intraoperative: Careful haemodynamic management; warming; avoid unnecessary fluid excess; lower dose anaesthetic agents (reduced pharmacokinetic reserve)
Postoperative: HDU/ICU; early mobilisation; multimodal analgesia (avoid NSAIDs); cognition monitoring (delirium prevention)

5. Risk Stratification Summary Table

Tool	Components	Use
RCRI (Lee Index)	6 variables	Predicts MACE in noncardiac surgery
NSQIP MICA Calculator	5 variables	Predicts MACE + cardiac arrest
Duke Activity Status Index	Activities → METs	Functional capacity
AHA Surgical Risk Classification	Surgery type	Risk categories
CFS	Frailty assessment	Elderly patients

Q3. MITRAL STENOSIS

A. PATHOPHYSIOLOGY

Normal MVA: 4–6 cm²

Severity	MVA	Mean Gradient
Mild	>1.5 cm²	<5 mmHg
Moderate	1.0–1.5 cm²	5–10 mmHg
Severe	<1.0 cm²	>10 mmHg
Critical	<0.6 cm²	>20 mmHg

Haemodynamic Consequences:

Obstruction at mitral valve → ↑LA pressure
↑LA pressure → pulmonary venous hypertension → pulmonary oedema
Chronic → pulmonary arterial hypertension (PAH) → RV failure
Fixed cardiac output — CO cannot increase with demand
LA enlargement → atrial fibrillation (30–40%) → loss of 25% CO (atrial kick)
Tachycardia shortens diastole → ↑transmitral gradient → acute pulmonary oedema

The "deadly quartet" in severe MS:

Tachycardia | AF | ↑Preload | ↑Pulmonary pressure

B. ANAESTHETIC GOALS (ALL SCENARIOS)

Parameter	Goal	Rationale
Heart rate	60–80 bpm (SLOW)	Slow HR = longer diastole = better LV filling
Rhythm	Sinus rhythm	Maintain atrial kick; AF → 25% ↓CO
Preload	Maintain/High-normal	Fixed cardiac output; avoid hypovolaemia
Afterload	Maintain/High	Avoid SVR drop → hypotension
PVR	Minimize	Avoid hypoxia, hypercarbia, acidosis, hypothermia
Contractility	Maintain	RV function critical

C. SEVERE MS FOR LSCS

Risk: Highest maternal mortality valve lesion in pregnancy. Haemodynamic challenge because:

Pregnancy physiological changes: ↑HR, ↑CO (+50%), ↑blood volume (+50%), ↓SVR → exacerbate MS
Labour: HR surges, contractions → acute pulmonary oedema
Delivery/postpartum: sudden autotransfusion → ↑LA pressure → flash pulmonary oedema

Pre-LSCS Assessment:

Echo: MVA, gradient, LA size, PAH, LV/RV function
MVA <1.5 cm² in pregnancy: consider balloon mitral valvuloplasty (BMV) before delivery if severe symptoms
Cardiology + obstetric + anaesthesia multidisciplinary planning

Anaesthetic Technique for LSCS:

	Spinal	Epidural	GA
MS suitability	Avoid (sudden↓SVR)	Preferred (slow titration)	If contraindicated
Why	Rapid↓SVR → tachycardia + collapse	Gradual hemodynamic changes	Risk of intubation tachycardia

Epidural (Preferred) Protocol:

Slow incremental dosing — avoid bolus hypotension
Phenylephrine as vasopressor (avoids reflex tachycardia vs. ephedrine)
Avoid:
- Tachycardia (oxytocin bolus — use slow infusion)
- Hypovolaemia (pre-load, not aggressive; LA cannot accommodate excess)
- Ergometrine (causes severe pulmonary hypertension)

Monitoring: Arterial line, CVP, pulse oximetry, ECG. Consider PA catheter in severe PAH.

Labour analgesia: Early epidural (reduces pain-induced tachycardia).

D. SEVERE MS FOR EMERGENCY APPENDICECTOMY

Challenge: No time for optimization; GA usually required.

Key Steps:

Emergency echo if not done
Rate control before induction: IV metoprolol/esmolol; target HR <80
If in AF: consider DC cardioversion if haemodynamically unstable
Induction: Modified RSI (aspiration risk + emergency)
- Etomidate (haemodynamically stable) preferred over propofol
- Avoid ketamine (↑HR) and suxamethonium succinylcholine alone (vagolytic tachycardia risk → avoid); modified RSI with rocuronium preferred
Maintenance: Volatile agent (isoflurane/sevoflurane) with caution; low-dose opioid
Vasopressors: Phenylephrine for hypotension
Ventilation: Mild hyperventilation (prevent hypercapnia → ↑PVR)
Extubation: Only when awake, normothermic, haemodynamically stable
Postoperative: HDU/ICU monitoring; continue rate control; anticoagulate if AF

E. RHEUMATIC HEART DISEASE IN PREGNANCY

Most common cardiac complication of pregnancy in developing countries
MS (most common) + MR + TR + AR
Penicillin prophylaxis throughout pregnancy (secondary prevention of rheumatic fever)
Anticoagulation: if AF or prosthetic valve (LMWH preferred in first trimester; warfarin 2nd trimester if valve; LMWH peri-delivery)
Increased risk of: pulmonary oedema (especially peripartum), AF, thromboembolism, maternal death
Delivery mode: vaginal preferred (if haemodynamically stable); LSCS for obstetric indications

Q4. ARRHYTHMIAS + ACLS + POST-CARDIAC ARREST CARE

A. VENTRICULAR TACHYCARDIA (VT) — ACLS 2020 (AHA)

Classification:

Type	Duration	Haemodynamic
Sustained VT	>30 sec	Stable or unstable
Non-sustained VT	<30 sec	Usually stable
Monomorphic VT	Single QRS morphology
Polymorphic VT (TdP)	Changing QRS morphology	Often degenerates to VF

Management — Stable Sustained Monomorphic VT:

IV amiodarone 150 mg over 10 min → infusion 1 mg/min × 6h → 0.5 mg/min × 18h
Alternative: IV lidocaine 1–1.5 mg/kg
Synchronised DC cardioversion if pharmacotherapy fails or deteriorates
Correct precipitants: ischemia, hypokalaemia, hypomagnesaemia

Management — Unstable VT (Pulseless VT) → Same as VF → ACLS protocol

Torsades de Pointes (TdP):

Stop precipitating drug; correct hypokalaemia/hypomagnesaemia
IV MgSO₄ 2g bolus (first-line)
Overdrive pacing if recurrent

B. VENTRICULAR FIBRILLATION (VF) — ACLS 2020

Immediate (within seconds):

Unresponsive/No breathing/No pulse
    ↓
Activate emergency response + get defibrillator
    ↓
Start HIGH-QUALITY CPR (30:2)
    ↓
Attach defibrillator — Confirm VF/pulseless VT
    ↓
SHOCK: 200J biphasic (120-200J device-dependent)
    ↓
Immediately resume CPR ×2 min (NO pulse check after shock)
    ↓
IV/IO access + Adrenaline 1mg every 3-5 min
    ↓
Shock after 2 min CPR; if persistent VF/pVT → Amiodarone 300mg IV
    ↓
Continue 2-min CPR cycles
    ↓
Second amiodarone dose: 150mg; Lidocaine alternative: 1-1.5 mg/kg

High-Quality CPR (AHA 2020):

Parameter	Target
Rate	100–120/min
Depth	≥5 cm (≤6 cm) adults
Recoil	Complete chest recoil — lift off chest
Interruptions	<10 sec per pause
Ventilation	1 breath per 6 sec (30:2 until advanced airway)
Compressions	Switch compressor every 2 min

Medications in ACLS:

Adrenaline 1mg IV every 3–5 min (non-shockable: as soon as possible; shockable: after 3rd shock)
Amiodarone 300mg (1st dose) + 150mg (2nd dose) — for VF/pVT
Lidocaine alternative if amiodarone unavailable: 1–1.5 mg/kg
Sodium bicarbonate: if known hyperkalemia or TCA overdose
MgSO₄: TdP, hypomagnesaemia

C. ATRIAL FIBRILLATION

Rate vs Rhythm Control:

Strategy	Indication	Drugs
Rate control	Most stable AF	Metoprolol, diltiazem, digoxin
Rhythm control	New onset <48h, haemodynamically unstable	Amiodarone, flecainide, DCCV

Perioperative AF:

New onset intraoperative AF: if unstable → synchronised DCCV 120-200J biphasic
Stable: rate control with IV metoprolol or diltiazem
Anticoagulation: if AF >48h or unknown duration → anticoagulate before cardioversion (or TOE to exclude LA thrombus)

Synchronised DC Cardioversion:

Synchronise to R wave (avoids R-on-T → VF)
Sedation required (propofol/midazolam)
AF: 120–200J biphasic; Flutter: 50–100J biphasic
Defibrillation pads antero-lateral or antero-posterior

D. POST-CARDIAC ARREST CARE (AHA 2020)

Targeted Temperature Management (TTM) — Now "Temperature Control":

Current AHA 2023 update: Prevent fever (>37.7°C) is minimum standard
Active TTM at 32–36°C for 24h for unconscious ROSC patients (comatose post-arrest)
Previous evidence (TTM trial, TTM-2 trial 2021): 33°C vs 36°C no survival difference → 36°C acceptable
Avoid fever (>38°C) strictly for 72h post-arrest

Post-ROSC Bundle (ABCDE):

Target	Goal
SaO₂	94–98% (avoid hyperoxia → free radical injury)
PaCO₂	35–45 mmHg (avoid hypercapnia → cerebral vasodilation; avoid hypocapnia → cerebral ischemia)
MAP	≥65 mmHg (consider 80–100 in post-cardiac arrest)
Blood glucose	7.8–10 mmol/L (avoid hypoglycaemia)
Seizure control	EEG monitoring; treat subclinical seizures
Coronary angiography	If shockable rhythm with suspected cardiac cause → emergent cath lab
Temperature	32–36°C × 24h → prevent fever × 72h

Neurological prognostication: Not before 72h post-arrest; multimodal approach (clinical exam, EEG, SSEP, MRI, biomarkers).

E. INFANT vs ADULT CPR

Feature	Adult	Child (1–8 yrs)	Infant (<1 yr)
Compression depth	≥5 cm	≥5 cm (1/3 chest AP)	4 cm (1/3 AP)
Rate	100–120/min	100–120/min	100–120/min
Compression:ventilation	30:2 (1 rescuer)	30:2 (1 rescuer); 15:2 (2 rescuers)	30:2 (1 rescuer); 15:2 (2 rescuers)
Technique	2 hands	1 or 2 hands	2 fingers / 2-thumb encircling
Defibrillation	200J	2 J/kg → 4 J/kg	2 J/kg → 4 J/kg
Adrenaline	1mg IV	0.01 mg/kg IV	0.01 mg/kg IV
Airway	Head-tilt chin-lift	Head-tilt chin-lift	Neutral position (sniffing)

Most common cause of arrest:

Adult: Cardiac (VF/VT) → rhythm-first (shock early)
Child/Infant: Respiratory/Asphyxia → ventilation-first emphasis (2 rescue breaths before compressions in witnessed collapse)

Q5. PACEMAKER / ICD — PERIOPERATIVE MANAGEMENT

A. PACEMAKER CLASSIFICATION (NBG/NASPE Code)

Position	Meaning	Common Letters
I — Chamber paced	A=atrial, V=ventricle, D=dual
II — Chamber sensed	A, V, D, 0
III — Response to sensing	I=inhibit, T=trigger, D=dual
IV — Rate modulation	R=rate responsive
V — Multisite pacing	A, V, D

Common modes:

VVI: Demand pacing — VF patients, pacemaker-dependent
DDD: Dual chamber, physiological pacing — most modern
DOO/VOO/AOO: Asynchronous (fixed rate) — used perioperatively to prevent EMI inhibition

B. PERMANENT PACEMAKER FOR TURP

Key Concern: Monopolar diathermy (electrosurgery) → electromagnetic interference (EMI) → inhibits pacemaker or triggers inappropriate shocks

Preoperative Steps:

Identify device type (pacemaker vs ICD), manufacturer, model
Check if pacemaker-dependent (underlying rhythm <40 or asystole without pacing)
Device interrogation by cardiologist/physiologist
Programme to DOO or VOO (asynchronous) mode before surgery if pacemaker-dependent

TURP-Specific:

Use bipolar diathermy wherever possible (no current through body — minimal EMI)
If monopolar unavoidable: keep current path away from device; short bursts
Place return electrode (diathermy plate) to direct current away from device
Have external pacemaker/defibrillator available in theatre
Magnet application: places most devices in asynchronous mode (VOO/DOO) — but check device response

ICD Management:

Suspend ICD therapy perioperatively (ICD may misinterpret diathermy artifact as VF → inappropriate shock)
Programme to monitor-only mode OR apply device magnet (suspends shock therapy while in place)
External defibrillation pads must be placed before suspending ICD

Postoperative: Restore original pacemaker settings; re-interrogate device.

Q6. ECMO — BASICS AND ROLE

A. TYPES OF ECMO

Type	Circuit	Indication
VV-ECMO (veno-venous)	Venous → oxygenator → venous	Respiratory failure (ARDS); cardiac function intact
VA-ECMO (veno-arterial)	Venous → oxygenator → arterial	Cardiorespiratory failure; cardiogenic shock; cardiac arrest (ECPR)

B. COMPONENTS

Cannulae (drainage + return)
Centrifugal pump (continuous flow)
Membrane oxygenator (gas exchange + CO₂ removal)
Heat exchanger

C. INDICATIONS

VV-ECMO:

Severe ARDS (PaO₂/FiO₂ <80 despite optimal ventilation — Murray score ≥3)
Bridge to lung transplant
Status asthmaticus refractory

VA-ECMO:

Cardiogenic shock refractory to pharmacotherapy
Massive PE with haemodynamic collapse
Refractory VT/VF (ECPR)
Post-cardiotomy syndrome (failure to wean from CPB)
Myocarditis, fulminant cardiac failure

ECPR (CPR + ECMO):

Refractory cardiac arrest (<60 min CPR, witnessed, reversible cause, age <75, no comorbidities)

D. ROLE IN COVID-19

VV-ECMO used in severe COVID ARDS when ventilator strategies fail
ELSO guidelines recommended: PaO₂/FiO₂ <80 on FiO₂ 1.0 + PEEP ≥10 for >6h
ECMO Centre referral criteria followed
RECOVERY-RS and EOLIA trial data informed practice

E. COMPLICATIONS

Complication	Mechanism
Bleeding	Anticoagulation (heparin) + consumption coagulopathy
Thromboembolism	Circuit clot
Haemolysis	Pump trauma
Infection	Line-related
Limb ischaemia	VA-ECMO arterial cannula
North-south syndrome	VA-ECMO: differential oxygenation of upper/lower body

Q7. VENOUS AIR EMBOLISM (VAE)

A. CAUSES / RISK FACTORS

Surgical positions at risk:

Sitting/beach chair position (neurosurgery) — highest risk
Posterior fossa surgery
Shoulder surgery, cervical spine, ENT procedures

Other causes: Central line insertion/removal, laparoscopy, liver transplant, obstetric delivery, TURP, joint replacement

Pathophysiology: Air enters venous system → obstructs RV outflow → ↓CO → cardiovascular collapse; CO₂ in capnograph falls (↑dead space); "Mill wheel" murmur.

B. DIAGNOSIS

Monitor	Sign	Sensitivity
Precordial/Oesophageal Doppler	Change in pitch	Most sensitive (0.05 mL/kg)
EtCO₂ (capnograph)	Sudden ↓EtCO₂	High; most practical intraoperative
PA catheter	↑PAP, ↓EtCO₂, PCWP changes	Sensitive + diagnostic
ECG	Sinus tachycardia, RV strain, S₁Q₃T₃	Late
Haemodynamics	↓BP, ↑HR, ↓SpO₂	Late/severe
TEE	Air in RA/RV	Highly sensitive and specific

EtCO₂ is the most practical intraoperative monitor for VAE.

C. MANAGEMENT

Immediate:

Stop air entry: flood surgical field with saline; compress jugular veins/pack wound
Inform surgeon — lower surgical site if possible
FiO₂ to 1.0 (100% O₂ — displaces N₂O if in use; N₂O must be discontinued immediately as it expands air)
Lower surgical field below heart level
Aspiration of air from CVP line (multi-orifice catheter at RA-SVC junction ideally)
Left lateral decubitus + head-down position (Durant manoeuvre — traps air in RV apex, prevents PA obstruction)
Vasopressors for hypotension (noradrenaline/dopamine)
If cardiac arrest: CPR + ACLS

N₂O must be stopped immediately (expands air bubble by ×2-3).

D. PARADOXICAL AIR EMBOLISM

Occurs in patients with PFO (patent foramen ovale) — 25% population
Air crosses from right to left → systemic arterial embolism → stroke, coronary embolism
Sitting position + ↑ICP → ↑RA pressure → opens PFO → paradoxical embolism
Diagnosed by: new neurological deficit + echocardiographic air in left heart
Prevention: avoid sitting position in PFO patients; maintain positive PEEP; use SSEP/MEP monitoring

Q8. HYPERTENSION — PERIOPERATIVE MANAGEMENT

A. DEFINITIONS

Category	SBP	DBP
Normal	<120	<80
Elevated	120–129	<80
Stage 1 HTN	130–139	80–89
Stage 2 HTN	≥140	≥90
Hypertensive urgency	>180	>120 (no organ damage)
Hypertensive emergency	>180/120 + end-organ damage

B. HYPERTENSIVE PATIENT FOR SURGERY

When to postpone?

BP >180/110 mmHg at preoperative assessment → consider elective postponement to optimize
End-organ damage (renal failure, LVH, retinopathy) → optimise
Emergency surgery: Proceed regardless; control BP perioperatively

Preoperative:

Continue all antihypertensives perioperatively except ACE inhibitors/ARBs (associated with refractory intraoperative hypotension — hold morning of surgery or continue per anaesthesiologist discretion)
Beta-blockers: continue (do not stop)
Diuretics: consider holding if volume-depleted
Ensure RAAS blockade decision made (controversial — many centres continue)

Intraoperative:

Phase	Risk	Management
Laryngoscopy/intubation	↑↑BP, tachycardia	Lignocaine IV 1.5 mg/kg pre-intubation; esmolol; deep anaesthesia
Maintenance	Usually well-controlled
Emergence/extubation	↑BP, tachycardia	Labetalol, hydralazine, GTN, dexmedetomidine

Treatment of Intraoperative Hypertension:

GTN infusion (vasodilation)
Labetalol (alpha + beta block)
Hydralazine (direct vasodilator — slow onset)
Clevidipine/nicardipine (IV CCB — titratable)
Sodium nitroprusside (SNP) for hypertensive emergencies (rapid, titratable; cyanide toxicity >10 mcg/kg/min)

Rebound hypertension post-clonidine withdrawal: Treat with IV clonidine or alpha-agonist.

Q9. NON-INVASIVE CARDIAC OUTPUT MONITORING

A. CLASSIFICATION

Category	Methods
Non-invasive	Echocardiography, Bioreactance, Thoracic bioimpedance, Photoplethysmography (esCCO)
Minimally invasive	Oesophageal Doppler, Pulse contour analysis (FloTrac, PiCCO), Partial CO₂ rebreathing (NICO)

B. INDIVIDUAL METHODS

1. Oesophageal Doppler Monitor (ODM) — CardioQ

Principle: Doppler probe in oesophagus measures aortic blood flow velocity → calculates aortic cross-sectional area → CO = flow velocity × aortic CSA

Waveform analysis:

FTc (corrected flow time): Preload indicator (normal 330–360 ms); low FTc → hypovolaemia
Peak velocity (PV): Contractility marker
Mean acceleration (MA): Contractility
Stroke distance: SV surrogate

Indications: GI surgery, cardiac surgery, critical care. Guides fluid management (SVV-guided).

Limitations: Requires sedation/GA; probe movement; aortic regurgitation invalidates.

2. Pulse Contour Analysis — FloTrac/Vigileo, PiCCO

Principle: Arterial waveform analysis → SV derived from pulse pressure waveform morphology

FloTrac: Uncalibrated; uses radial artery; continuous CO
PiCCO: Calibrated by transpulmonary thermodilution; requires central + arterial line; also measures EVLW (extravascular lung water) and GEDV

SVV (Stroke Volume Variation) and PPV (Pulse Pressure Variation):

SVV >13% or PPV >13% → fluid responsive (mechanically ventilated, sinus rhythm, Vt ≥8 mL/kg required)
Limitations: spontaneous breathing, arrhythmia, open chest, low Vt → invalid

3. Thoracic Bioimpedance / Bioreactance

Principle: High-frequency AC current through chest → measures changes in electrical impedance with cardiac cycle → calculates SV and CO

Bioreactance (NICOM): Phase-shift analysis (more accurate than impedance)
Completely non-invasive; simple electrode placement
Limitations: accuracy reduced in obesity, pleural effusion, arrhythmia, pacemakers

4. Partial CO₂ Rebreathing — NICO

Principle: Modified Fick equation using CO₂; partial rebreathing circuit adds dead space → measures CO₂ kinetics → calculates CO

Non-invasive; useful in ventilated patients
Limitations: requires intubation; inaccurate in high shunt states (ARDS)

5. Echocardiography (TTE/TEE)

Principle: LVOT diameter + VTI (velocity-time integral) by PW Doppler → CO = LVOT CSA × VTI × HR

TEE: Semi-invasive; most comprehensive; continuous monitoring in GA
TTE/POCUS: Point-of-care; assess filling, SWMA, valves, pericardial effusion

Clinical Uses of POCUS CO:

Assess fluid responsiveness (IVC collapsibility index)
Detect cardiac cause of haemodynamic instability
Guide vasopressor/inotrope use

6. Summary Comparison Table

Method	Invasiveness	Continuous	Calibration	Best Use
Oesophageal Doppler	Semi	Yes	No	ICU, OR fluid management
FloTrac	Minimal (arterial)	Yes	No	General OR
PiCCO	Moderate	Yes	Yes (thermodilution)	ICU complex cases
NICOM (bioreactance)	None	Yes	No	Non-invasive monitoring
NICO	Airway only	Yes	CO₂ rebreathing	Ventilated ICU
TEE	Semi	Yes	No	Cardiac OR, hemodynamic instability
TTE/POCUS	None	Intermittent	No	Emergency, ICU, ward

Q10. CORONARY CIRCULATION AND MYOCARDIAL O₂ CONSUMPTION (MVO₂)

A. CORONARY ANATOMY

Left Main Coronary Artery (LMCA) → LAD + LCx
- LAD: Anterior LV wall, anterior septum, apex, bundle branches (diagonal + septal branches)
- LCx: Lateral LV wall, posterior LV (in left-dominant); OM branches
RCA: Right ventricle, posterior LV (right-dominant 85%), SA node (55%), AV node (85%)

Right dominant (85%): RCA gives posterior descending artery (PDA) Left dominant (15%): LCx gives PDA

B. CORONARY BLOOD FLOW CHARACTERISTICS

Normal CBF: 250 mL/min (~5% of CO)
70–80% of LV perfusion occurs in diastole (systolic compression impedes subendocardial flow)
Subendocardium is most vulnerable to ischemia (lowest perfusion pressure, highest wall tension)

Coronary Perfusion Pressure (CPP):

CPP = Aortic DBP − LVEDP

Autoregulation: Maintains CBF constant between MAP 50–120 mmHg. Fails in atherosclerosis → pressure-dependent flow.

Regulation of Coronary Blood Flow:

Mechanism	Factor	Effect
Metabolic (dominant)	↓O₂, ↑CO₂, ↑adenosine, ↑H⁺, ↑K⁺	Vasodilation (adenosine primary mediator)
Endothelial	NO, prostacyclin	Vasodilation
Endothelial	Endothelin	Vasoconstriction
Neural (minor)	α₁ stimulation (sympathetic)	Vasoconstriction
Neural	β₂ stimulation	Vasodilation
Autoregulation	Myogenic response	Flow maintained 50–120 mmHg

Coronary reserve: Ability to increase CBF 4–5× above resting level (lost in critical stenosis).

C. DETERMINANTS OF MYOCARDIAL O₂ CONSUMPTION (MVO₂)

MVO₂ Components (at rest):

Component	% of Total MVO₂
Pressure work (wall tension × SBP)	~64%
Volume work (ejecting blood)	~15%
Basal metabolic work	~20%
Electrical activation	~1%

Wall tension (LaPlace's Law):

T = P × r / 2h (T = tension; P = ventricular pressure; r = radius; h = wall thickness)

→ Ventricular dilation ↑wall tension → ↑MVO₂ → LVH (↑wall thickness) → ↓wall tension → ↓MVO₂ per unit

Clinical Determinants — The "3 H's":

Heart Rate (major; tachycardia → ↑MVO₂ + ↓diastolic time → double jeopardy)
Wall Tension = Preload (EDV) × Afterload (SBP/SVR)
Contractility (inotropy)

Rate-Pressure Product (RPP) = Double Product:

RPP = HR × SBP

Normal at rest: ~8,000–10,000
Ischemic threshold: usually >12,000–13,000
Clinical use: reflect MVO₂; avoid RPP >12,000 perioperatively in CAD patients

D. SUPPLY vs DEMAND IMBALANCE → ISCHEMIA

↑ MVO₂ (Demand) — Pro-ischemic:

Tachycardia, hypertension, increased contractility, LV dilation, pain, light anaesthesia

↓ O₂ Supply — Pro-ischemic:

Tachycardia (↓diastolic time), hypotension (↓CPP), hypoxaemia (↓CaO₂), anaemia, coronary stenosis, vasospasm, ↑LVEDP

Effects of Anaesthetic Agents on Coronary Circulation:

Agent	HR	Contractility	SVR	Coronary effect
Volatile agents (isoflurane/sevoflurane)	↑/-	↓	↓	Vasodilate; ischemic preconditioning
Propofol	↓	↓	↓↓	May ↓CPP
Ketamine	↑↑	↑	↑	↑MVO₂ — use cautiously
Opioids (fentanyl)	↓	-	-	Minimal; favourable in CAD
Pancuronium	↑	↑	-	Vagolytic — avoid in CAD

E. ISCHEMIC PRECONDITIONING

Brief episodes of ischemia/reperfusion protect myocardium against subsequent sustained ischemia
Volatile anaesthetics (isoflurane, sevoflurane, desflurane): Mimic ischemic preconditioning via K_ATP channel activation and protein kinase C → preferred in cardiac/high-risk cases
Mechanism: adenosine → G-protein → PKC → K_ATP channel opening → mitochondrial protection

Sources: Miller's Anesthesia 10e (Chapters 29, 50, 13); Barash Clinical Anesthesia 9e; AHA/ACC 2024 Perioperative Guidelines; AHA ACLS 2020; AHA BLS/ACLS 2023 Update; ESC/ESA 2022 Non-cardiac Surgery Guidelines

---All 10 questions are now answered. Here's a quick navigation guide to what's above:

EXAM ANSWER NAVIGATOR

Q	Topic	Key Scoring Points
Q1	Myocardial Ischemia Under GA	ECG lead sensitivity table (II+V4+V5=98%), TEE most sensitive, hemodynamic goals table, GTN/beta-blocker/volatile agents
Q2	Cardiac Pt for Non-Cardiac Surgery	ACC/AHA stepwise algorithm, RCRI 6-point table, DES timing (new-gen 6 months), antiplatelet bridging, each scenario covered
Q3	Mitral Stenosis	MVA severity table, "avoid tachycardia" goals table, epidural preferred for LSCS, modified RSI for emergency, avoid ergometrine
Q4	Arrhythmias + ACLS + CPR	AHA 2020 VF algorithm, high-quality CPR parameters, amiodarone 300+150 mg, TTM at 32–36°C, infant vs adult CPR comparison table
Q5	Pacemaker/ICD for TURP	NBG code, VOO/DOO programming, bipolar diathermy preference, magnet effect, ICD suspension protocol
Q6	ECMO	VV vs VA table, indications, ECPR, COVID role, ELSO criteria
Q7	Venous Air Embolism	Monitoring sensitivity table (Doppler most sensitive, EtCO₂ most practical), Durant manoeuvre, N₂O must stop, paradoxical embolism via PFO
Q8	Hypertension	BP classification, ACEi/ARB morning-of decision, laryngoscopy response management, SNP for emergencies
Q9	Non-invasive CO Monitoring	6 methods, oesophageal Doppler (FTc/PV), FloTrac/PiCCO, SVV >13% = fluid responsive, bioreactance, comparison table
Q10	Coronary Circulation + MVO₂	CPP formula, 70-80% diastolic flow, LaPlace's law, MVO₂ components (pressure work 64%), RPP threshold >12,000, ischemic preconditioning via KATP

Exam tips:

Always open with a crisp definition/intro (2 lines)
Include at least one table per answer — examiners reward structured organisation
End with "anaesthetic goals" or "monitoring targets" — ties everything together
For scenario questions (DES/MS/frail elderly), explicitly state what you would avoid — this demonstrates depth

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