Review of Pharmacology - 9E (2015)

Review of Pharmacology
10. Ans. (a) Esmolol; (b) Sotalol; (e) Diazepam (Ref: Ajay yadav 2/e p110)
• Bupivacaine is most cardiotoxic local anaesthetic.
• At toxic doses, local anaesthetics can result in CNS (convulsions) or CVS (hypotension, bradycardia, arrhythmias)
symptoms.
• Diazepam is used to treat convulsions. If not responding, thiopentone may be used.
• Arrhythmias should be promptly treated using bretylium, amiodarone, disopyramide, magnesium sulphate,
esmolol or sotalol.
• Lignocaine should be avoided as anti-arrhythmic because it can exacerbate the CNS toxicity.
• In refractory arrhythmias, intravenous lipid emulsion (like intralipid) has been found to be extremly useful.
• Bupivacaine induced cardiotoxicity is enhanced by acidosis, hypercarbia and hypoxemia.
Anaesthesia
11. Ans. (c) The local anaesthetic binds to its receptor mainly when the Na + channel is in the resting state (Ref: KDT 6/e p352, 353)
• All LAs are weak bases.
• LAs act by blocking Na + channels from inside the neuron (intraneuronal face).
• These can cross the membrane only in unionized (lipid soluble) form. Sodium bicarbonate is therefore added to make
the LA rapid acting.
• Once inside the neuron, LAs again gets ionized and bind to Na + channels.
• Binding to Na + channels is more in repetitively firing neurons than in resting neurons.
12. Ans. (a) Cocaine (Ref: KDT 6/e p356, 357)
• All LAs cause hypotension except cocaine.
• Cocaine increases blood pressure by inhibiting the reuptake of catecholamines.
13. Ans. (d) Dibucaine (Ref: KDT 6/e p358)
• Longest acting, most potent and most toxic LA is dibucaine.
• Chlorprocaine is the shortest acting LA.
14. Ans. (b) By surface application, it can anaesthetize unbroken skin (Ref: KDT 6/e p357)
• Lignocaine or prilocaine cannot anaesthetize intact skin.
• Eutectic mixture is the combination of equal proportions of lignocaine and prilocaine at 25 °C. This mixture has a
lower melting point than any of the two ingredients. It helps to make the preparation oily that can be applied on the
intact skin.
• Eutectic mixture can be used to anaesthetize intact skin.
15. Ans. (d) All of the above (Ref: KDT 6/e p359, 360)
• Factors affecting the height of block
––
Volume of drug
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Baricity (Ratio of specific gravity of an agent to that of CSF).
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Position of the patient
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Intra-abdominal pressure
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Curvature of spine
• Factors affecting duration of block
––
Dose
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Concentration
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Drug (LA used)
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Added vasoconstrictors
16. Ans. (b) Sympathetic block is higher than the sensory block (Ref: KDT 6/e p360)
Spinal anaesthesia creates a zone of differential blockade in which sympathetic fibres are blocked two segments higher and
motor fibres are blocked two segments lower than the level of sensory block.
17. Ans. (c) Posture of the patient (Ref: KDT 6/e p360)
Posture of the patient determines the height of block, not the duration.
18. Ans. (a) Orthopedic manipulation on the upper limb (Ref: KDT 6/e p361)
IVRA is indicated for procedures on upper limb or lower limb of less than one hour duration.
19. Ans. (b) Bupivacaine (Ref: KDT 6/e p357, 358)
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