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pharmaco > GA > Flashcards

GA Flashcards

1
Q

what does GA aim to do

A

unconsciousness

amnesia

analgesia

relaxation of skeletal muscle

loss of autonomic NS reflex

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2
Q

What are the stages of anesthesia

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

What happens during the surgical anesthesia stage of anesthesia

A

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

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4
Q

What are the types of anesthetic

A

Inhaled, IV

for Inhaled, there are gas and liquid

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

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5
Q

When would inhaled analgesic be considered effective in terms of absorption

A

need to achieve a brain concentration of inhaled anesthetic

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6
Q

what affects the rate at which therapeutic brain concentration is achieved

A
  • 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)
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7
Q

What is the rate of metabolism of GA dependent on

A

a.solubility in blood
b. duration of exposure

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8
Q

What is the pharmacokinetics of the inhaled anesthetics

A
  • 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

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9
Q

Which inhaled GA causes a decrease in systemic resistance

A

isoflurane , sevoflurane

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10
Q

List examples of inhaled liquid GA

A

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

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11
Q

What inhaled GA causes a reduction in cardiac output

A

halothane and enflurane

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12
Q

what are the action of inhaled GA on the organ system

A
  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
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13
Q

What inhaled GA causes bronchodilation

A

halothane and sevoflurane

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14
Q

What are some toxic effects of inhaled GA

A
  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.
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15
Q

What is malignant hyperthermia treated with

A

dantrolene to reduce release calcium and supportive measure

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16
Q

what does halothane do

A

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
17
Q

What is the limitation of Nitrous oxide

A

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

18
Q

What is the difference between IV anesthetics and inhaled anesthetics

A

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

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

19
Q

What are some examples of IV GA

A
  • inducing agents
    thiopentone,propofol, etomidate
  • dissociative anesthesia like ketamine
  • neurolept analgesia like fentanyl+Droperidol
20
Q

how does barbiturates act to achieve anesthesia

A

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

21
Q

Why is thiopental commonly used for induction

A
  • 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
22
Q

What is the benzodiazepine antagonist, whats the dose required

A

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

23
Q

How does benzodiazepine compare with barbiturates

A

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

24
Q

How does propofol potentiates its action of anesthetic

A

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

25
Q

What is the most popular IV anesthetic and why

A

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

26
Q

how does propofol decrease BP

A

Decrease peripheral arterial resistance, venodilation, negative inotrope

27
Q

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

A

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

28
Q

WHat is the side effect of ketamine

A

associated with post operative disorientation, illusions and dreams

29
Q

What kind of alternative to GA are there

A

balanced anesthesia, monitored anesthesia, conscious sedation

30
Q

what does balanced anesthesia entail

A
  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

pharmaco (19 decks)

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