CNS Drugs MCQs

1. The minimal alveolar concentration of an inhalational anaesthetic is a measure of its:

A. Potency

B. Therapeutic index

C. Diffusibility

D. Oil: water partition coefficient

ANSWER:  [  A  ]


2. The primary mechanism by which general anaesthetics produce their action is:

A. Affecting receptor operated ion channels in cerebral neurones

B. Blocking voltage sensitive Na+ channels in neuronal membrane

C. Depressing metabolic activity of cerebral neurones

D. Blocking production of high energy phosphates in the brain

ANSWER:  [  A  ]


3. General anaesthetics produce immobility in response to painful surgical stimuli by acting primarily at the:

A. Motor cortex

B. Basal ganglia

C. Thalamus

D. Spinal cord

ANSWER:  [  D  ]


4. Which general anaesthetic selectively inhibits excitatory NMDA receptors:

A. Thiopentone

B. Halothane

C. Desflurane

D. Ketamine

ANSWER:  [  D  ]


5. If a patient being anaesthetised with ether is unconscious, has regular respiration, blood pressure and heart rate are normal, corneal reflex is present and eyeballs are roving, the patient is in:

A. Stage II

B. Stage III plane 1

C. Stage III plane 2

D. Stage III plane 3

ANSWER:  [  B  ]


6. No surgical operation should be performed during the following stage of anaesthesia:

A. Stage I

B. Stage II

C. Stage III, plane 1

D. Stage III, plane 3

ANSWER:  [  B  ]


7. Which of the following is a sign of deep anaesthesia:

A. Appearance of tears in eyes

B. Resistance to passive inflation of lungs

C. Fall in blood pressure

D. Patient makes swallowing movements

ANSWER:  [  C  ]


8. The following factor delays induction with an inhaled general anaesthetic:

A. Alveolar perfusion-ventilation mismatch

B. Hyperventilation

C. Low blood:gas partition coefficient of the anaesthetic

D. Inclusion of 5% carbon dioxide in the inhaled gas mixture

ANSWER:  [  A  ]


9. ‘Second gas effect’ is exerted by the following gas when coadministered with halothane:

A. Nitrous oxide

B. Cyclopropane

C. Nitrogen

D. Helium

ANSWER:  [  A  ]


10. ‘Diffusion hypoxia’ is likely to occur only after use of nitrous oxide because it:

A. Is a respiratory depressant

B. Has low blood solubility and is used in high concentration

C. Is a very potent anaesthetic

D. Interferes with diffusion of oxygen into the tissues

ANSWER:  [  B  ]


11. Select the inhalational general anaesthetic which is metabolized in the body to a significant extent:

A. Sevoflurane

B. Isoflurane

C. Ether

D. Halothane

ANSWER:  [  D  ]


12. The following anaesthetic can be used by the open drop method:

A. Ether

B. Desflurane

C. Halothane

D. Isoflurane

ANSWER:  [  A  ]


13. The minimal alveolar concentration (MAC) of halothane is:

A. 75%

B. 25%

C. 7.5%

D. 0.75%

ANSWER:  [  D  ]


14. The following general anaesthetic has poor muscle relaxant action:

A. Ether

B. Nitrous oxide

C. Halothane

D. Isoflurane

ANSWER:  [  B  ]


15. Select the correct statement about nitrous oxide:

A. It irritates the respiratory mucosa

B. It has poor analgesic action

C. It is primarily used as a carrier and adjuvant to other anaesthetics

D. It frequently induces post anaesthetic nausea and retching

ANSWER:  [  C  ]