local anesthetics

Question 1

Amino esters - ester link

Answer 1

cocaine, procaine, 2 chloroprocaine, tetracaine

ester type - broken down by cholinesterase in plasma

Question 2

amino amides - amide link

Answer 2

lignocaine, mepivvacaine, bupivacaine, ropivacaine, prilocaine, etidocaine

amino amides - metabolised in the liver and excreted in kidney

Question 3

How to LA’s work

Answer 3

bind to sodium channels and increase sodium influx

-starts off blocking sensory, then can cause muscular blockade

Question 4

duration of action

potency

Answer 4

• duration of action is degree of protein binding in sodium channel
• potency - depends on lipid solubility

Question 5

why is adrenaline added?

Answer 5

LAs are vasodilators, adrenaline can decrease the rate of vascular absorption by causing vasoconstriction

Question 6

allergic reaction?

Answer 6

rare

Question 7

symptoms of CNS toxicity

Answer 7

numbness of tonuge, lightheadedess, visual and auditory disturbances, muscular twitching, unconsciousness, convlusions, coma, resp arrest

signs - shivering, muscular twitching, tremors, generalised tonic clonic seizure

Question 8

CVS toxicity

Answer 8

can direclty affect cardiac and vascular smooth muscles
LAs - also depress myocardial contractility in a dose dependant fashion
-dysarthmias - VT (bupivacaine)
-high conc = SA node fucntion - bradycardia and arrest

Question 9

what increases sensitivity to bupivacaine

what can potentiate the negative chronotrpic and inotropic affeects of LAs

Answer 9

pregnancy

-acidosis, hypoxia, hypercapnia

Question 10

prilocaine side effect

Answer 10

can cause metaemoglobin made in liver to o-toludine, which can cause oxidation of HV to MtHb - resolves but can be treated with methyl blue