First and Last muscle to relax after administering anesthesia?

[630670]

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Does anyone know what is the first muscle to relax and the last muscle to relax after administering an inducing agent?

 

[Jeff05]

i'm pretty sure that all the central muscles - oo, pharyngeal, diaphragm are the first to be blocked and the first to return.

ulnar is last to be blocked and last to return.

 

[dfk]

you can also think of it as first to go are the pharyngeal (vocal cords) down to diaphragm... and then diaphragm to vocal cords first to last in reverse order.
orbicularis oculi for induction (vocal cords) and ulnar nerve for reversal (diaphragm) are, IMO, the sites for reversal check.

 

[dhb]

you can also think of it as first to go are the pharyngeal (vocal cords) down to diaphragm... and then diaphragm to vocal cords first to last in reverse order.
orbicularis oculi for induction (vocal cords) and ulnar nerve for reversal (diaphragm) are, IMO, the sites for reversal check.

If you are a med student or resident somewhat new to this forum i advise you that the above poster is most often wrong as he is in this post.

The diaphragm is monitored with the orbicularis oculi ,although it is fully paralyzed at much higher doses, since this is the first mucle to recover.
The pharyngeal muscle behave in a similar way as the orbicularis oculi but the abductor pollicis should be checked for reversal since it is more sensitive to neuromuscular blockade 9last to recover).

http://www.anesthesia-analgesia.org...873c278a399258f82fd7a592&keytype2=tf_ipsecsha


Potency of Pancuronium at the Diaphragm and the Adductor Pollicis Muscle in Humans:

"The mean dose (+/-SEM) required to depress adductor pollicis and diaphragm responses to first twitch stimulation (ED50) was 29.5 +/- 3.5 [mu]g/kg and 59.5 +/- 7.0 [mu]g/kg, respectively. Corresponding values for ED90 were 45 +/- 5 [mu]g/kg and 95 +/- 11 [mu]g/kg, respectively, indicating that the diaphragm required approximately twice as much pancuronium as the adductor pollicis for an identical block. At 90% adductor pollicis block, the diaphragm was only 24 +/- 4% blocked. It is concluded that the adductor pollicis response might underestimate the degree of diaphragmatic relaxation."

 

[RabbMD]

Of course an induction agent generally does not paralyze any muscles. Induction agent techically = propofol/ketamine/pentothal/etomidate ect... Muscle paralytics do the paralyzing 🙂....

 

[behindthadeuce]

It's easier to remember these things if you understand the physiology behind them. Muscles that receive higher blood flow are blocked 1st and recover 1st from paralysis (ie diaphragm). Muscles receiving less blood flow, like orbicularis and ulnar n muscles, take longer to paralyze and longer to recover. The pharyngeal muscles generally are comparable to ulnar n muscles.

Muscles that have more fibers, ie in the hand, have a more profound blockade than muscles w/ less fibers (ie on the face).


👍

 

[BLADEMDA]

i'm pretty sure that all the central muscles - oo, pharyngeal, diaphragm are the first to be blocked and the first to return.

ulnar is last to be blocked and last to return.

Jeff has the expected Board Answer.

OO is a beter predictor of the onset of NMB at the vocal cords than AP.
Laryngeal adductor muscles and OO block have similar onset times.

The onset time at the OO is shorter than the AP. The OO is thought to better reflect the diaghram and laryngeal muscles than AP.


http://www.anesthesia-analgesia.org/cgi/reprint/80/2/360?ck=nck

Here is a "tricky" Board question: Which site is best for neuromuscular monitoring of Myasthenia Gravis? OO or AP?

 

[BLADEMDA]

The relation of blockade between these two muscles was not the same in healthy patients and myasthenic patients: in healthy patients, the maximum neuromuscular blockade with 0.025 mg/kg vecuronium was less in the orbicularis oculi than in the adductor pollicis (median 72%vs. 91%;P < 0.05); in contrast, in myasthenic patients, the blockade with 0.01 mg/kg vecuronium was greater in the orbicularis oculi than in the adductor pollicis (median 96%vs. 62%;P < 0.05).
Conclusion: Neuromuscular monitoring at the orbicularis oculi may overestimate blockade in myasthenic patients. Extubation must be performed when the muscle most sensitive to neuromuscular blocking agents is recovered. Therefore, neuromuscular monitoring at the orbicularis oculi is recommended to avoid persistent neuromuscular blockade in patients with myasthenia gravis.


(In Healthy patients the adductor Pollicis is the most "sensitive" muscle and recovers LAST.)

 

[ozzie20]

The relation of blockade between these two muscles was not the same in healthy patients and myasthenic patients: in healthy patients, the maximum neuromuscular blockade with 0.025 mg/kg vecuronium was less in the orbicularis oculi than in the adductor pollicis (median 72%vs. 91%;P < 0.05); in contrast, in myasthenic patients, the blockade with 0.01 mg/kg vecuronium was greater in the orbicularis oculi than in the adductor pollicis (median 96%vs. 62%;P < 0.05).
Conclusion: Neuromuscular monitoring at the orbicularis oculi may overestimate blockade in myasthenic patients. Extubation must be performed when the muscle most sensitive to neuromuscular blocking agents is recovered. Therefore, neuromuscular monitoring at the orbicularis oculi is recommended to avoid persistent neuromuscular blockade in patients with myasthenia gravis.


(In Healthy patients the adductor Pollicis is the most "sensitive" muscle and recovers LAST.)

I'm probably not following here, something for me isn't adding up.

In myasthenic patients we follow the most sensitive muscle to paralytics in this case the OO, but in normal patients the most sensitive muscle is the AP, we don't follow that one because it overestimates the degree of blockade.

You'd think that we'd follow the AP in myasthenic patients because its less sensitive to the paralytics than the OO and therefore in closer relation to the degree of diaphragmatic relaxation?

 

[ReefTiger]

For purposes of the board:
Diaphragm is the most resistant to paralyzation, reason unclear.
Obicularis oculi approximates pharyngeal muscle blockade
Distal extremities/abd muscles are least resistant to blockade

 

[fakin' the funk]

For purposes of the board:
Diaphragm is the most resistant to paralyzation, reason unclear.
Obicularis oculi approximates pharyngeal muscle blockade
Distal extremities/abd muscles are least resistant to blockade

Doesn't this directly contradict what Jeff05 said?

 

[ReefTiger]

If we are to get specific for board purposes I should have been a bit more clear.
The adductor pollicis is slower to onset of blockade compared with laryngeal muscles with lower dose NMB, but is blocked completely at a faster rate with higher dosing as compared to laryngeal muscles (0.8-1mg/kg roc).

The ap muscle is slower to recover than diaphragm, laryngeal adductors, and rectus abdominis.

Monitoring OO muscle approximates laryngeal conditions for intubation.

The above is from Barash 4th ed. p 436

Diaphragm is most resistant according to the board based on past questions.

Take it for what it's worth. I know what my choice will be if the question is on the board exam.