GA

Question 1

what does GA aim to do

Answer 1

unconsciousness

amnesia

analgesia

relaxation of skeletal muscle

loss of autonomic NS reflex

Question 2

What are the stages of anesthesia

Answer 2

1. analgesia
2. excitement
3. surgical anesthesia
4. medullary depression

Question 3

What happens during the surgical anesthesia stage of anesthesia

Answer 3

loss of eye movement, eye reflexes, regular respiration recurs followed by apnea

Question 4

What are the types of anesthetic

Answer 4

Inhaled, IV

for Inhaled, there are gas and liquid

for IV, there are inducing agents, dissociative anesthesia, and neurolept analgesia

Question 5

When would inhaled analgesic be considered effective in terms of absorption

Answer 5

need to achieve a brain concentration of inhaled anesthetic

Question 6

what affects the rate at which therapeutic brain concentration is achieved

Answer 6

• solubility ( low solubility in blood, can transfer into brain faster), reach high arterial tension rapidly
• anesthetic concentration in inspired air
• rate and depth of pulmonary ventilation
• pulmonary blood flow( higher blood flow, rate of rise of anesthetic tension in blood and brain decreases)
• arteriovenous concentration gradient( concentration gradient depend on uptake of anesthetic by tissue, which is high. high concentration gradient increases time to achieve equilibrium with brain)

Question 7

What is the rate of metabolism of GA dependent on

Answer 7

a.solubility in blood
b. duration of exposure

Question 8

What is the pharmacokinetics of the inhaled anesthetics

Answer 8

• modify ion channels by direct interactions with multiple members of the ligand-gated ion channel family

for eg GABAa, nicotinic, glycine receptors

also act on the sensitivty of specific neurons and pathway like the spino-thalamic tract and reticular activating system

Question 9

Which inhaled GA causes a decrease in systemic resistance

Answer 9

isoflurane , sevoflurane

Question 10

List examples of inhaled liquid GA

Answer 10

isoflurane sevoflurane, ester, halothane, enflurane, desflurane, methoxyflurane

Question 11

What inhaled GA causes a reduction in cardiac output

Answer 11

halothane and enflurane

Question 12

what are the action of inhaled GA on the organ system

Answer 12

1. CVS decreases mean arterial pressure, depression of the myocardial function
2. Respiratory, decrease in minute ventilation, reduced response to hypercapnia, increase apnoeic threshold, depression of mucociliary function, bronchodilation
3. brain, increased cerebral blood flow by decreasing cerebral vascular resistance
4. renal, reduced renal blood flow
5. Liver
6. Uterus, halogenated anesthetics are potent uterine muscle relaxants

Question 13

What inhaled GA causes bronchodilation

Answer 13

halothane and sevoflurane

Question 14

What are some toxic effects of inhaled GA

Answer 14

1. hepatic ( some exposed to halothane may develop hepatitis), may initiate immune mediated response
2. Renal–> renal dysfunction following methoxyflurane due to release of fluoride during metabolism
3. Malignant hyperthermia
   an autosomal dominant skeletal muscle disorder. GA in suceptible individuals trigger hypertension, tachycardia, severe muscle rigidity, hyperthermia, acidosis. Increase muscle cell calcium.

Question 15

What is malignant hyperthermia treated with

Answer 15

dantrolene to reduce release calcium and supportive measure

Question 16

what does halothane do

Answer 16

used to maintain anesthesia and also can be used for induction most commonly in children

• relaxes skeletal muscle and potentiate skeletal muscle relaxants
• decrease blood pressure due to depression of cardiac output with little change in systemic vascular resistance. may cause bradycardia and arrythmia
• may rarely cause halothane hepatitis, sudden and sever liver necrosis, usually develop several days after anesthesia

Question 17

What is the limitation of Nitrous oxide

Answer 17

even at maximum dose nitrous oxide cannot give complete unconciousness or surgical anesthesia. Used as an adjunct with other inhaled anesthetics. Analgesic agent for labour pain

Question 18

What is the difference between IV anesthetics and inhaled anesthetics

Answer 18

onset of action is faster and hence commonly used for induction.

most IV lack analgesic properties, can be supplemented with local or inhaled anesthetics

Question 19

What are some examples of IV GA

Answer 19

• inducing agents
  thiopentone,propofol, etomidate
• dissociative anesthesia like ketamine
• neurolept analgesia like fentanyl+Droperidol

Question 20

how does barbiturates act to achieve anesthesia

Answer 20

Binds to Gabaa receptors, facilitate action of GABA by increasing duration of GABA gated chloride channel opening.

Act on AMPA receptor to depress glutamate mediated excitation, non synaptic membrane efect

Question 21

Why is thiopental commonly used for induction

Answer 21

• rapidly distributes out of blood and brain to muscle and fat due to high lipid solubility
• rapidly crosses blood brain barrier, produces loss of consciousness quickly when sufficient doses given

Question 22

What is the benzodiazepine antagonist, whats the dose required

Answer 22

flumazenil, short duration of action (<90mins), may require multiple doses

Question 23

How does benzodiazepine compare with barbiturates

Answer 23

Benzodiazepine have a slower onset of CNS depressant effects, it also reaches a plateau inadequate for surgical anesthesia

Question 24

How does propofol potentiates its action of anesthetic

Answer 24

it potentiates GABAa receptor activity, slowing the channel closing time; sodium channel blocker; endocannabinoid system activity

Question 25

What is the most popular IV anesthetic and why

Answer 25

Propofol; has a rapid rate of onset of action and also recovery is more rapid than barbiturates. Also used for induction and maintenance of anesthesia as a part of total IV or balance anesthesia

Question 26

how does propofol decrease BP

Answer 26

Decrease peripheral arterial resistance, venodilation, negative inotrope

Question 27

What kind of IV GA is ketamine, how does it work

Answer 27

produces dissociative amnesia( no loss of consciousness) . It is a lipophilic drug that is rapidly distributed to the brain. Metabolised by liver, excreted by kidney and in the bile. It is the only IV with both anesthetic and analgesic properties stimulates Central sympathetic NS and inhibit reuptake of noradrenaline, useful in those with cardiogenic or septic shock. Increase cerebral blood flow, oxygen consumptio and intracranial pressure

Question 28

WHat is the side effect of ketamine

Answer 28

associated with post operative disorientation, illusions and dreams

Question 29

What kind of alternative to GA are there

Answer 29

balanced anesthesia, monitored anesthesia, conscious sedation

Question 30

what does balanced anesthesia entail

Answer 30

1. use both iv and inhaled anesthesia, IV for induction, inhalation for maintenance. Can also use LA to provide pre or peri operative analgesia, CvS drugs to control transient autonomic responses to noxious surgical stimuli