XENON

Xenon [Ref: Morgan’s Anaesthesia 4/e p 781, 166, 167; Miller’s Anaesthesia p 626, 6491

• Xenon seems to be the best answer because all other inhalational anaesthetics mentioned in the question produce some cardiovascular effects that may harm the patient with mitral stenosis.
• Mitral stenosis is a disorder where cardiac output remains relatively fixed. Decrease in cardiac output should he avoided at any cost.

– An^y drug that increases the heart rate will reduce the cardiac output in patient with M.S.

• All the inhalational agents mentioned in the question decrease systemic vascular resistance and also increase the heart rate.
• Decrease in systemic vascular resistance leads to fall in blood pressure.
• Moreover, they may also decrease B.P. by their cardiodepressant action on myocardium.

Therefore these drugs should not be used in patients with M.S.

“Xenon has no effects on cardiac output or cardiac rhythum and is not thought to have significant effect on systemic vascular resistance It also does not affect pulmonary function and is not known to have any renal or hepatic toxicity”.

• The main drawback of Xenon is its high cost and insufficient availability.

–Xenon is an inert gas which is quite difficult to obtain and hence extremely expensive.

– Xenon has received considerable interest in the last few years because it has many characteristics approaching those of an “ideal” inhaled anaesthetics.

Mitral stenosis

• Due to mitral stenosis less blood _.flows through the mitral valve to left ventricle.
• Left ventricle functions normally but is small and poorly.filled.
• Initially the left ventricle dilates keeping the pulmonary artery pressure low. As disease progresses pulmonary artery pressure increases and medial hypertrophy develops resulting in chronic reactive pulmonary hypertension.
• The right heart hypertrophies to pump against a pressure overload, then.fails.
• The pressure gradient across the narrow mitral orifice increase with the square of cardial output.
• Rapid heart rates, especially with atrial fibrillation decreases diastolic _.filling time and markedly decreases cardiac output.
• Li / .filling is optimized by slow heart rate.

Hemodynamic goals

• Low normal heart rate 50-70/min, treat tachycardia aggressively with _/8 blockers.
• Maintain sinus rhythmus if possible.
• Maintain adequate preload
• Maintain high normal systemic vascular resistance
• Avoid hypercarbia, acidosis and hypoxia which may exacerbate pulmonary hypertension.
• The cardiac output is relatively fixed, maintain adequate afterload, slow the heart rate and avoid hypovolemia.
• Measure CVP and PAOP and maintain high preload.
• Avoid rapid decrease in afterload.

Xenon is 4.5 times heavier than air. It is an inert gas.

Blood gas partition coefficient is 0.14. It has low blood solubility.

Xenon exhibits minimal cardiovascular and hemodynamic side effects and

is not known to be metabolized in the liver or kidney.

Hence Xenon will be ideal inhalational anaesthetic agent in this patient.

Advantages of Xenon:

• It is not toxic

• It does not trigger malignant hyperthermia

• It has very low blood gas solubility coefficient

• Very rapid induction and recovery

• Non explosive

• Environment friendly
   

Disadvantages of Xenon:
 

• Very high cost

• Low potency
   

Ref: Textbook of Anesthesia for Postgraduates By T. K. Agasti, 2011, Page 424; Miller’s Anesthesia: … edited by Ronald D. Miller, 2009, Page 640.

C i.e. Slow induction and recovery

A i.e. Rapid induction and recovery

Xenon is inert/ nobel, colourless, odorless, nonirritating, nonflammable and non explosive gas that is heavier than air (4 times), more dense/viscous than N2 & N20, more potent than N₂0, is very blood insolubleQ (B/G coefficienct 0.14) most ideal inhaled anesthetic agent with very rapid induction & recoveryQ. It is neuro & cardioprotective, non teratogenic, and safe (to liver & kidney) anesthetic which is environmental friendly.

At 0.115, Xenons’ B/G partition coefficient is the lowest coefficient of all available agents, resulting in rapid induction and recoveryQ.

Ans. is ‘a’ i.e., Xenon

Xenon

• It exerts anaesthetic action by non competitive blockade of NMDA receptors.
• Xenon has been used as a general anesthetic.
• Xenon interacts with many different receptors and ion channels and like many theoretically