CONSIOUSNESS (WEEK 4) Flashcards Preview

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Flashcards in CONSIOUSNESS (WEEK 4) Deck (14)
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1
Q

What are the 3-5 main components of anesthesia?

A
  • analgesia = pain relief
  • amnesia = loss of memory
  • immobilization
  • hypnosis = loss of consciousness “sleep” (not in all sources)
  • muscle relaxation (optional)
2
Q

How is anesthesia administered?

A

vaporizer machine -> breathing circuit -> patient’s trachea -> lungs -> pulmonary blood -> brain

IV anesthesia is another route

3
Q

Factors affecting anesthetic uptake?

A
  • anesthetic solubility in blood (if anesthetic too soluble in blood, has high concentration in blood at the start and low concentration in the brain at the start - > takes longer to equilibrate the two b/c brain concentration has to also be higher to reflect high blood solubility (and it takes a while for blood to be filled to its maximum capacity) -> takes a while to reach that; so high blood solubility increases t for brain to uptake)
  • partial pressure difference between alveoli and pulmonary venous blood (bigger difference, more drug uptake)
  • alveolar ventillation -> better diffusion -> better brain transport
4
Q

how is solubility of inhaled anesthetic expressed?

A

via partition coefficient - the higher the blood/gas solubility the higher the blood/gas partition coefficient -> the longer it takes for equilibrium to be reached between alveoli and blood -> slower rate of induction (introduction)
NO/desflurane - lowest partition coefficient - fastest
isoflurane/halothane - highest partition coefficient - longest to reach equilibrium in brain

5
Q

What is the general idea of how anesthetics work?

A

Facilitation of inhibition
↑ GABA A receptor-mediated transmission (Cl- in, hyperpolarizes cell)
↑ Background (“leak”) K+ conductance
— Inhibition of excitation
↓ Glutamate & ACh receptor-mediated transmission

6
Q

what are some S/E of anesthetic metabolism (inhaled), how is toxicity related to blood solubility?

A

higher blood solubility -> higher metabolism -> higher potential of organ damage when metabolized and eliminated - > hepatotoxicity and nephrotoxicity (double whammy - less availability to brain and higher toxicity (think higher concentration in the blood - more chances to hurt kidneys and liver)

7
Q

How is concentration of inhaled anesthetics measured?

A

MAC = minimal alveolar concentration = concentration of an inhaled anesthetic IN THE ALVEOLI at 1 atm that prevents movement in response to painful stimulus in 50% of patients

1 MAC not enough, usually 1.2 MAC prevent movement in 95% of patients

but… low therapeutic index LD50/ED50 = 2-3 (twice the therapeutic dose can be fatal)

8
Q

What are factors that decrease anesthetic’s MAC (minimal alveolar concentration)?

A

age (as age decreases, need less anesthetic)
pregnancy (progesterone increase is a natural anesthetic)
decrease in core temperature (hypothermia is anesthetic)
opioids (likewise)

9
Q
What are organ effects of inhaled anesthetics?
 CNS
 CV
 Resp
 Kidneys
 MSK
 Uterus
A

remember vasodilation in most systems…
CNS - decrease in cerebral metabolic rate (decreased oxygen consumption)
cerebral vasodilation

CV - decrease in arterial blood pressure, halothane can cause ventricular arrhythmias

Resp - respiratory depression
but also decreases airway resistance (last resort treatment for asthmatics)

Kidneys - reduction in renal blood flow (vasodilation, so less blood to kidneys) -> decreased GFR and urinary output

MSK - skeletal muscle relaxation

Uterus - uterine relaxation (think that it is also a muscle), can lead severe blood loss at birth due to prolonged relaxation - general anesthesia not recommended, spinal done

10
Q

examples of inhaled anesthetics?

A

halothane, sevoflurane, isoflurane, desflurane, NO (nitrious oxide)

11
Q

examples of Iv anesthetics?

A

propofol, ketamine, etomidate

12
Q

Propofol: MOA and S/E

A

Propofol: sedation, maintenance of anesthesia; smooth, pleasant dreams, head clear on awakening
Propofol: facilitates inhibition via GABAA receptors
Propofol: metabolized in liver
Propofol: no analgesic potential
Propofol: risk of hypotension, respiratory depression and apnea (stop of breathing), potential for sepsis b/c bacteria love its formulation -> must be used fast

13
Q

Ketamine: MOA and S/E

A

Ketamine = PCP: dissociative anesthesia - patient conscious but unable to process or respond to sensory input (+ amnesia +analgesia)
Ketamine: minimal resp depression and airway reflexes maintained
Ketamine: still bronchodilator
Ketamine: unpleasant dreams
Good for trauma or shock b/c no change in pressure of battlefield surgery

works by blocking glutamate

14
Q

Etomidate (imidazole derivative): S/E & MOA?

A

etomidate: minimal effects on hemodynamics - good for unstable patients
etomidate: no analgesia
etomidate: MOA similar to proposal