Michael stenosis anaesthesia management for anaesthesia residency 10 marks

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mitral stenosis pressure volume loop anesthesia hemodynamics

This diagnostic image is a transthoracic echocardiogram utilizing Color Flow Doppler to evaluate cardiac hemodynamics. The image primarily demonstrates severe mitral valve stenosis and its associated secondary anatomical changes. A red arrow identifies a severely dilated left atrium, indicating chronic pressure and volume overload. A blue arrow points to the stenotic mitral valve orifice. The Color Doppler signal illustrates the characteristic flow disturbances of stenosis: proximal to the mitral valve, there is a large area of red-coded flow representing blood moving toward the transducer; as blood passes through the narrowed valve, it transitions into a high-velocity, turbulent jet distal to the valve, characterized by a mosaic of blue, yellow, and green colors indicating aliasing and flow acceleration. This visual confirms the restricted valvular opening and significant obstructive gradient across the bioprosthetic mitral valve, consistent with a clinical diagnosis of prosthetic valve stenosis in a patient presenting with cardiogenic shock.

This diagnostic image shows a split-screen echocardiogram used to determine the Mitral Valve Area (MVA) via the pressure half-time (PHT) method. The upper section contains a 2D transesophageal echocardiography (TEE) view in a mid-esophageal aortic valve long-axis orientation, showing the placement of the Doppler sample volume. The lower section displays a Pulsed-Wave (PW) spectral Doppler signal of mitral inflow. The Doppler waveforms appear below the baseline, indicating flow away from the transducer, and exhibit a characteristic E-wave with a measured deceleration slope. Annotations on the right display quantitative hemodynamics: a maximum velocity (Vmax) of 155 cm/s, a deceleration slope of 458 cm/s², and a pressure half-time (P½t) of 99 ms. Based on these values, the calculated Mitral Valve Area (MVA P½t) is 2.22 cm². This imaging is critical for assessing mitral valve function and stenosis severity in a clinical or intra-operative setting.

This composite figure illustrates the multimodal assessment of moderate mitral stenosis using invasive hemodynamics and 4D Flow Cardiovascular Magnetic Resonance (CMR). Panel (a) shows an invasive pressure tracing comparing pulmonary artery wedge pressure (PAWP) and left ventricular pressure (LVP), demonstrating a mean diastolic gradient of 6 mmHg. Panels (b-d) display anatomical CMR images in the left ventricular outflow tract (LVOT), 4-chamber, and vertical long axis views, revealing morphological hallmarks of mitral stenosis: thickened mitral valve leaflets, restricted leaflet opening (doming), and secondary left atrial dilatation. Panels (f-h) provide 4D flow velocity overlays (color-coded from 0 cm/sec in blue to 150 cm/sec in red) superimposed on the anatomical views. These overlays demonstrate high-velocity flow jets (red/orange) accelerating through the stenotic mitral orifice during diastole. Panel (e) shows the corresponding quantification of peak velocity derived from the 4D flow data, aligning with the invasive mean pressure drop. The figure serves as an educational comparison between gold-standard invasive manometry and non-invasive advanced cardiac imaging for valvular heart disease evaluation.

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Mitral Stenosis - Anaesthesia Management (10 Marks)

Quick Overview

Mitral stenosis (MS) is characterised by obstruction to left ventricular inflow. The normal mitral valve area (MVA) of 4-6 cm² must be reduced to <2.5 cm² before symptoms appear, and <1.5 cm² denotes severe disease. Anaesthetic management is directed entirely by the underlying pathophysiology.

1. Pathophysiology (Foundation for Management)

The stenotic valve creates a fixed obstruction to diastolic LV inflow, producing a transvalvular pressure gradient. This drives all downstream consequences:

Consequence	Mechanism
Left atrial dilation	Chronic pressure overload, predisposes to AF
Pulmonary venous hypertension	LA pressure transmitted backward
Pulmonary arterial hypertension	Reactive PVR rise (reversible initially, then fixed)
RV dilation and failure	Chronic RV afterload
Tricuspid regurgitation	Functional, from RV dilation
LV underloading	Restricted inflow - LVEDV and LVEDP are LOW
AF (30-40%)	LA dilation - loss of atrial kick (20-30% of CO)
Systemic emboli	Stasis in LA appendage

The gradient across the valve is flow-dependent: ΔP = 4v² (modified Bernoulli). Any increase in heart rate or CO dramatically worsens the gradient and raises LA pressure.

The LV pressure-volume loop in MS is shifted leftward - smaller volume, maintained systolic pressure, reduced stroke volume.

PV loops in valvular heart disease. B = mitral stenosis (small, leftward loop). A = normal; C = aortic stenosis; D = mitral regurgitation; E = aortic regurgitation.

2. Preoperative Assessment

History: Dyspnoea on exertion, orthopnoea, PND, haemoptysis, palpitations, embolic events, hoarseness (Ortner's syndrome - recurrent laryngeal nerve compression by enlarged LA).

Examination:

Loud S1, opening snap, mid-diastolic rumble with presystolic accentuation
Signs of pulmonary hypertension: loud P2, right parasternal heave

Investigations:

ECG: P mitrale (bifid P wave), right axis deviation, RVH in pulmonary hypertension; AF if present
CXR: LA enlargement (double shadow at right heart border), pulmonary venous congestion, Kerley B lines
Echocardiography (mandatory): MVA (normal 4-6 cm²), mean gradient, LA size, pulmonary artery pressure, LV/RV function, presence of LA thrombus
Cardiac catheterisation: if echo-clinical discrepancy or suspected CAD

Severity Classification (by MVA and mean gradient):

Severity	MVA (cm²)	Mean Gradient (mmHg)
Mild	>1.5	<5
Moderate	1.0-1.5	5-10
Severe	<1.0	>10

Medical optimisation:

Rate control: beta-blockers or digoxin (target HR 60-80 bpm)
Diuretics for pulmonary congestion
Anticoagulation if AF present or prior embolic event (therapeutic INR 2-3)
Continue antiplatelets, statins
Patients undergoing elective non-cardiac surgery should have MS corrected first if severe

3. Haemodynamic Goals (The Core of Management)

The mnemonic to remember is: "Slow, Full, Tight"

Parameter	Goal	Rationale
Heart Rate	LOW-NORMAL (60-80 bpm)	Tachycardia shortens diastole - reduces LV filling time, raises gradient dramatically
Rhythm	Sinus rhythm (maintain if present)	Loss of atrial kick in AF removes 20-30% of CO
Preload	HIGH-NORMAL (judicious)	LV is underloaded and depends on preload; but avoid overload - fine margin
Afterload (SVR)	NORMAL to HIGH	Vasodilation reduces preload; use vasopressors to maintain
Contractility	Maintain	LV function is usually preserved
PVR	MINIMISE	Avoid hypoxia, hypercapnia, acidosis, N₂O, light anesthesia

"Vasodilation that occurs following both neural axial and general anesthesia can lead to peripheral venous blood pooling and inadequate volume delivery to the left ventricle. This can precipitate haemodynamic collapse." - Morgan & Mikhail's Clinical Anaesthesiology, 7e

4. Intraoperative Monitoring

Standard ASA monitors (mandatory)
Invasive arterial line (for major surgery - beat-to-beat BP, frequent ABGs)
Central venous catheter: prominent 'a' wave in sinus rhythm; prominent 'cv' wave suggests secondary tricuspid regurgitation
Pulmonary artery catheter: PCWP reflects transvalvular gradient, NOT LVEDP; useful in severe MS but risk of PA rupture in pulmonary hypertension
Transoesophageal echocardiography (TEE): gold standard for intraoperative haemodynamic assessment; evaluates LV/RV function, filling, valve morphology, LA thrombus
ECG: continuous monitoring - detect AF or rate changes immediately

Key monitoring point: PCWP overestimates LVEDP in MS because LA-LV gradient exists throughout diastole. Prominent 'a' wave and decreased 'y' descent on PCWP waveform is characteristic of sinus rhythm MS.

5. Choice of Anaesthetic Technique

Regional Anaesthesia

Spinal anaesthesia: Use with extreme caution - rapid sympathetic blockade causes vasodilation and severe hypotension; generally avoided in moderate-severe MS
Epidural anaesthesia: Preferred regional technique - slow titration of sympathetic block is more controllable; can be used for labour analgesia and lower limb surgeries
Vasopressors must be immediately available

General Anaesthesia

Induction:

Aim: haemodynamically stable induction, avoid tachycardia and vasodilation
Etomidate (0.3 mg/kg): preferred - minimal haemodynamic effects, maintains SVR
High-dose opioid technique (fentanyl/sufentanil): blunts sympathetic response, avoids tachycardia
Ketamine: relatively avoided - causes tachycardia and increases pulmonary vascular resistance
Propofol: use reduced doses carefully - causes vasodilation; titrate slowly
Thiopentone: causes vasodilation - avoid in haemodynamically compromised patients
Pre-oxygenation mandatory; gentle mask ventilation to avoid hypoxia/hypercapnia

Laryngoscopy and intubation:

Opioid supplementation before laryngoscopy to blunt response
Short-acting beta-blocker (esmolol IV) may be given prophylactically

Maintenance:

Opioid-based technique is ideal (morphine, fentanyl, remifentanil) - heart rate control
Volatile agents (isoflurane, sevoflurane): use at low-moderate concentrations; may cause vasodilation at higher concentrations
Avoid nitrous oxide: increases PVR - worsens pulmonary hypertension
Avoid tachycardia-prone agents: pancuronium (causes tachycardia), meperidine/pethidine (atropine-like effect)
Neuromuscular blockade: vecuronium, rocuronium, or cisatracurium preferred (minimal haemodynamic effects)

Ventilation:

Avoid hypoxia (raises PVR)
Avoid hypercapnia (raises PVR)
Moderate tidal volumes, PEEP with caution (worsens RV afterload in pulmonary hypertension)
Target: normocapnia or mild hypocapnia (PCO₂ 35-40 mmHg)

6. Management of Specific Intraoperative Problems

Tachycardia

Identify and treat cause (pain, light anaesthesia, hypovolaemia, fever)
Deepen anaesthesia with opioid (fentanyl bolus)
IV esmolol (0.5 mg/kg bolus, then 50-200 mcg/kg/min) - preferred beta-blocker
IV metoprolol (1-5 mg increments)
Avoid meperidine (pethidine) - causes tachycardia

Atrial Fibrillation with fast ventricular rate

Rate control: digoxin, beta-blockers, amiodarone
DC cardioversion if haemodynamic collapse (synchronised cardioversion at 100-200 J)
Check anticoagulation status before cardioversion

Hypotension

Phenylephrine (pure alpha-agonist, 50-100 mcg IV): drug of choice - increases SVR without tachycardia
Vasopressin or norepinephrine if severe
Avoid ephedrine - its beta-agonist activity causes tachycardia, worsening MS haemodynamics

Pulmonary Hypertension/RV Failure

Optimise acid-base (correct acidosis)
Hyperoxia (FiO₂ 1.0)
Hypocapnia (mild)
Inhaled nitric oxide (iNO): 10-40 ppm - selective pulmonary vasodilator
Milrinone (0.375-0.75 mcg/kg/min): phosphodiesterase inhibitor - reduces PVR, inotropic support for RV
Epinephrine for RV inotropic support

Pulmonary Oedema

Diuretics (furosemide 20-40 mg IV)
Positive pressure ventilation (PEEP)
Consider nitrates with careful BP monitoring

7. Labour and Delivery (Obstetric Anaesthesia)

MS is the most common rheumatic valvular lesion encountered in pregnancy. Haemodynamic stresses of pregnancy (increased CO by 40-50%, increased HR, fluid retention) can critically worsen MS.

Labour analgesia: Carefully titrated epidural is the technique of choice - reduces pain-induced tachycardia, controls haemodynamics
Caesarean section: Epidural preferred over spinal (avoids sudden vasodilation); general anaesthesia when regional is contraindicated
Invasive monitoring (arterial line, CVP) for moderate-severe MS
Avoid ergometrine (causes coronary and pulmonary vasoconstriction)
Syntocinon (oxytocin): give slowly as IV infusion, not bolus (causes vasodilation and tachycardia as bolus)

8. Postoperative Management

Continue invasive monitoring in HDU/ICU for moderate-severe MS
Rate control is paramount postoperatively - pain and catecholamine surge cause tachycardia
Adequate analgesia (multimodal, opioids, nerve blocks) to prevent sympathetic tachycardia
Fluid management: meticulous - avoid overload (pulmonary oedema) and underload (cardiac output compromise)
DVT prophylaxis (high embolic risk)
Maintain anticoagulation if in AF
Watch for postoperative AF and treat promptly

Summary Table: Haemodynamic Goals at a Glance

Parameter	Desired	Avoid
Heart rate	60-80 bpm (slow)	Tachycardia (worst enemy)
Rhythm	Sinus (if present)	SVT, new AF
Preload	Maintain	Hypovolaemia AND hypervolaemia
SVR	Normal-high	Vasodilation
PVR	Low	Hypoxia, hypercapnia, N₂O
Contractility	Preserve	Myocardial depressants

Vasopressor of choice: Phenylephrine (no tachycardia) Beta-blocker of choice: Esmolol (short-acting, titratable) Avoid: Ketamine, meperidine, pancuronium, rapid spinal, nitrous oxide

Sources: Miller's Anesthesia, 10e (Ch. 50, Anesthetic Management - Mitral Stenosis); Morgan & Mikhail's Clinical Anaesthesiology, 7e (Ch. 21, Mitral Stenosis - Preoperative Considerations, Pathophysiology, Anesthetic Management); Barash, Cullen & Stoelting's Clinical Anaesthesia, 9e (Ch. 41, Valvular Heart Disease)

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