Why is Analgesia needed in anaesthesia

[Danyy361991]

Hi guys I know this question was addressed a few times, still I can't grasp the concept and I would appreciate greatly your help.

Anaesthesia definition:
1. Loss of consciousness
2. Analgesia
3. Amnesia
4. Muscle relaxation

Now, loss of consciousness means the patient does not feel nothing, even though the pain reach the CNS.
Therefore why do we need analgesia?

If we give Thiopental to induce anaesthesia we already have a state of not feeling pain, going to the micro-level the gaba receptors are open and the cell is so negative there is no stimulation of the CNS.
In that case why do we adjunct it with Fentanyl for example which will use G-inhibiotry mechanisms to also lower the negativity of the cell.

Same question regarding Amnesia, if the person is not conscious and he does not perceive any senses, why do I need to prevent memories from happening?

thank you so much for your help!

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[MackandBlues]

Because when you wake up from surgery everything is going to freaking hurt! Lol just because during the surgery you don't feel anything doesn't mean you won't afterwards. Think about the last time you cut yourself - did it only hurt during the initial cut? No it hurt for several days afterwards if it was significant enough of an injury


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[Transposony]

 

[Danyy361991]

Because when you wake up from surgery everything is going to freaking hurt! Lol just because during the surgery you don't feel anything doesn't mean you won't afterwards. Think about the last time you cut yourself - did it only hurt during the initial cut? No it hurt for several days afterwards if it was significant enough of an injury


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In that case we would give Morphine/ fentanyl after the surgery
Why do we give Fentanyl during the surgery.
to be more "MACRO" on this subject:
Why do we give Analgesia in surgery, if we already have the patient unconscious.

Remember that the definition of unconscious embedding in herself 'unawareness".
Which mean they guy doesn't know that the pain is there (in the surgery itself).

 

[ortnakas]

There's a difference between "not aware of pain" and "no pain."

 

[SKaminski]

There's a difference between "not aware of pain" and "no pain."

Is such a distinguishment clinically relevant? Why?

 

[slz1900]

Loss of consciousness does not prevent transmission of nociceptive stimuli to the cns. Pain will cause autonomic changes even if a patient is unconscious, so while a patient might not feel pain in the sense that they have a conscious perception of it, their body can still react (increase in hr, bp, etc). On top of that, there is a synergistic effect between some opioids and other anesthetics.

Specific to the mechanism, a lot of anesthetics will be better at one thing vs another, so propofol might be more sedating and less analgesic. Thiopentals effect on gaba vs an opioids effect on mu receptors isn't something that you are going to be able to reason out mechanistically since it isn't understood well enough (probably true for all cns drugs) so best to remember that all 4 components of anesthesia are required and that a combination of drugs is used to achieve that balance, even if on a cellular level there seems to be redundancy.

 

[Mad Jack]

Loss of consciousness does not prevent transmission of nociceptive stimuli to the cns. Pain will cause autonomic changes even if a patient is unconscious, so while a patient might not feel pain in the sense that they have a conscious perception of it, their body can still react (increase in hr, bp, etc). On top of that, there is a synergistic effect between some opioids and other anesthetics.

Specific to the mechanism, a lot of anesthetics will be better at one thing vs another, so propofol might be more sedating and less analgesic. Thiopentals effect on gaba vs an opioids effect on mu receptors isn't something that you are going to be able to reason out mechanistically since it isn't understood well enough (probably true for all cns drugs) so best to remember that all 4 components of anesthesia are required and that a combination of drugs is used to achieve that balance, even if on a cellular level there seems to be redundancy.

Pretty much this. You don't need to be consciously aware of pain to have autonomic responses to it. Those responses can cause life-threatening changes in blood pressure, heart rate, etc. You also reflexively react to things even when unconscious- it is the analgesia that dulls these responses if I'm not mistaken, thus making sure the patient isn't twitching all over the place while the surgeon is trying to do his thing. Patients often ride a fine border of unconsciousness that would be more difficult to maintain if their sense of pain was intact, thus requiring more sedation (and thus greater risk of complications) to keep them out. Overall this just adds up to anesthesia without analgesia being a stupid idea.

 

[lymphocyte]

Is such a distinguishment clinically relevant? Why?

Very much yes. Look up autonomic dysreflexia and T6 spinal cord lesions. There may or may not have been a question on this topic on my Step 1/2CK.