Inhalational anaesthetics

INHALATIONAL ANAESTHETICSMCQS

Q1. Index of potency of general anesthesia isa. Minimum alveolar concentrationb. Diffusion coefficientc. Dead space coefficientd. Alveolar blood concentration Ans: A)Minimum alveolar

concentration

Minimum alveolar concentration

It is the alveolar concentration of inhaled anesthetic that prevents movement in 50 percent of patients in response to standard stimulus (eg standard stimulus)

Best measure of anesthetic potency

primarily mediated by anaesthetic action in spinal cord

Q2. Potency of inhalational anaesthetic depends ona. Blood gas partition coefficientb. Oil gas partition coefficientc. Gas pressured. Blood pressure

Ans B)Oil gas partition coefficient

Partition coefficient

The relative solubilities of an anesthetic in air, blood & tissues are expressed partial coefficient

Blood gas partition coefficient measures solubility of GA .Most important factor in determining the uptake agent and so the speed of induction and recovery.

Oil-gas partition coefficient (lipid solubility) measures anesthetic potency.

Q3. Which one of the following is the fastest acting agent?a. Halothaneb. Isofluranec. Etherd. Sevoflurane

Ans D)Sevoflurane

Blood gas partition coefficient measures solubility of GA .Most important factor in determining the uptake agent and so the speed of induction and recovery.

Agents in increasing order of B/G coefficients

Xe(0.14) > Desflurane(0.42) > Cyclopropane (0.44) > N2O (0.47) >

Sevoflurane(0.69) > Isoflurane(1.38) > Enflurane(1.8) > Halothane(2.4) > Chloroform(8) > Trilene(9) >Ether(12) > Methoxyflurane(15)

Q4. All of the following factors decrease the minimum alveolar concentration (MAC) of an inhalational anaesthetic agent excepta. Hypothermiab. Hyponatremiac. Hypocalcemiad. Anaemia

Ans C)Hypocalcemia

Factors affecting increase on MAC

Young Chronic abuse of alcohol Hypernatremia Acute Amphetamine toxication Cocaine, Ephedrine

Factors affecting decrease on MAC

Hypothermia, Hyperthermia Elderly Anemia Pregnancy PaO2<40mmHg,PaCO2>95mmHg Drugs: Local anesthetics, Opiods,Ketamine,Barbiturates, Verampil, Lithium,Symptholytics. Chronic use of Amphetamine

Q5. True about xenon anaesthesiaa. Rapid induction and recoveryb. Low potencyc. High blood solubilityd. Non explosivee. Heavier than air

Ans)A,D,E

Xenon

is inert, colorless, odorless, non irritating, non inflammable and environmental friendly

more potent than N2O

It is neuro and cardioprotective

non teratogenic and safe(to liver and kidney)anesthetic

Xenon's B/G partition coefficient is the lowest, resulting in rapid induction and recovery.

Q6. Pungent volatile anaesthetic isa. Halothaneb. Isofluranec. Sevofluraned. Desfluranee. Nitrous oxide

Ans) B and D

Pungent volatile anaesthetic agents are

Desflurane Isoflurane Enflurane Ether

Q7. Which of the following inhaled gas is used to decrease pulmonary artery in adults and infants?a. Nitrous oxideb. Nitrogen dioxidec. Nitric oxided. Nitrogen

Ans C Nitric oxide

Nitric oxide or endothelium derived relaxing factor is synthesised from L-arginine by nitric oxide synthase (NOS) enzyme in endothelium of blood vessels.

Physiologically it causes vasodilation and decreases vascular resistance throughout the body.

Inhaled NO is a selective pulmonary –vasodilator decreases pulmonary artery pressure in infants and adults and improves V/P ratio..So it is used in treatment of pulmonary artery pressure

Q8. Diffusion hypoxia is seen duringa. Induction of anaesthesiab. Recovering anaesthesiac. Pre operativelyd. Post operatively

Ans B) Recovering anesthesia

Diffusion hypoxia is seen during recovery phase after discontinuation of prolonged N2O anaesthesia .

It can be prevented by continuing 100 % O2 inhalation for few minutes after discontinuing N2O

Q9. Use of nitrous oxide is contraindicated in all of the following surgeries excepta. Cochlear implantb. Microlaryngeal surgeryc. Vitreoretinal surgeryd. Exentration surgery

Ans D)Exentration surgery

Excentration is enclueation + wide dissection of periorbital tissue.In it there is no closed space formation so N2O can be used.

In microlaryngeal lesser surgery,N2O is contradicated due to risk of airway fire.

Q10. Soda lime circuit is not used with a. Enfluraneb. Isofluranec. Methoxyfluraned. Trilene

Ans D) Trilene

Sodalime with trilene forms phosgene (neurotoxic) gas.

It should not be used with: Chloroform Trilene Sevoflurane

Q11. Stages of anaesthesia was established bya. Etherb. N2Oc. Halothaned. Chloroform

Ans A) Ether

Guedel’s staging of anesthesia was given for ether

Stage I -Analgesia

Stage II-Delirium or Excitement Partially dilated pupil

Stage III- has 4 planes 1 moving eye to fixed eye 2 corneal or laryngeal reflex lost 3 light reflex lost 4Intercostal paralysis

Abdominal respiration Pupils fully dilated

Stage IV-Medullary Paralysis

Q12. Anaesthesia agent with least analgesic propertya. N2Ob. Halothanec. Etherd. Propane

Ans B)Halothane

Halothane

is a potent,non inflammable ,non toxic,colourless liquid with relatively non pungent vapour

Anesthesia agent with least analgesic agent

It’s a bronchodilator,uterine relaxant and vasodilator

Anesthesia of choice for uterine contraction and inversion

Q13. Which of them are the following contraindications for halothane use?a. Middle ageb. Recent halothane usec. Associated liver pathologyd. Obesity Ans-B and C

Contraindications of halothane

Liver dysfunction

Halothane use with in 3 months

Hypovolemia & severe cardiac disease

Pheochromocytoma and exogenous catecholamines administration

Q14. In increased ICT, agent used for anaesthesiaa. Isofluraneb. N2Oc. Trilened. Ether

Ans A) Isoflurane

Isoflurane

is anesthesia of choice for neurosurgical procedures ,renal failure and myasthenia gravis

Avoided in ischaemic heart disease

Cause coronary steal syndrome

used in daycare anesthesia

Q15. Which of the following is/are false?a. Enflurane interacts with sodalimeb. Sevoflurane causes seizuresc. Ketamine acts through GABA-A

receptorsd. MAC indicates potency of

inhalational agents

Ans B,A

Sevoflurane ,isoflurane and desflurane have anticonvulsant properties.

Enflurane causes epileptiform changes (more commonly during hypocapnia)hence should be avoided in epilepsy.

Enflurane interacts with sodalime but produce clinically insignificant amount of carbonmonoxide

Ketamine is a noncompetitive NMDA (glutamate) receptor antagonist

Propofol has smooth and rapid induction and rapid recovery.

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