RE5: Chapter 12: Neuromuscular Blocking Agents, Reversal Agents, and Their Monitoring Flashcards
(125 cards)
Describe neuromuscular depolarization blockade (phase 1 blockade).
- The motor end plate cannot repolarize until the agent leaves the nicotinic receptor
- Because the motor end plate cannot repolarize, it cannot respond to subsequent Ach release
- The agent binds to the nicotinic receptor on the motor end plate and causes depolarization
What is the difference between qualitative vs. quantitative neuromuscular blockade monitoring?
Qualitative monitoring involves visual or tactile response to evoked electrical stimulus as assessed by the clinician. (MOST COMMON METHOD)
Quantitative monitoring is where the stimulator is coupled with a displacement transducer as a movement measuring device and number value is displayed. (PREFERRED BUT LESS COMMON)
Describe neuromuscular non-depolarizing blockade (phase II blockade).
- Agent binds to the nicotinic receptor on the motor end plate, but it does NOT cause a conformation change in the receptor.
- It does, however, prevent Ach from binding to the receptor rendering the muscle effectively “paralyzed”
What is the preferred method of determining the level of neuromuscular blockade?
Contraction of the adductor muscle of the thumb via stimulation of the ulnar nerve.
Where are the electrodes placed to monitor the ulnar nerve?
The electrodes are applied over the ulnar nerve. The distal electrode is placed over the proximal flexor crease of the wrist, and the other electrode is placed over and parallel to the carpi ulnaris tendon.
What muscle groups are the most sensitive to neuromuscular blockers?
Eye muscles are the most sensitive and are the first group to be affected followed by the extremities, trunk, abdominal muscles and finally the diaphragm.
During recovery, which muscle group recovers first?
Diaphragm recovers the first and the eye muscles last!
OPPOSITE DIRECTION!
Which monitoring site is best to measure the onset of neuromuscular blockade? What is the response?
Facial nerve - eyelid movement
Which monitoring site is the best to measure recovery from neuromuscular blockade? What is the response?
Ulnar nerve - thumb adduction
What does it mean if fade is present?
Sign of drug-induced muscle paralysis OR a clinically significant block remains
How does fade occur?
Because the nondepolarizing drugs block presynaptic Ach receptors in addition to their classic antagonist effect at postsynaptic Ach neuromuscular junction sites.
What is a single twitch?
A single supra-maximal electrical stimulus ranging from 0.1 to 1Hz for 0.1 to 0.2 milliseconds
What monitoring test requires a baseline before drug administration?
Single Twitch
What is TOF stimulation?
A series of 4 twitches at 2Hz every 1/2 second for 2sec.
Compares the first twitch to the 4th twitch
Which monitoring test reflects blockade from 70% - 100%
TOF stimulation
What does it mean if the fourth twitch (T4) disappears OR you have 3 twitches?
Disappearance of the third twitch (T4 and T3 absent)? OR you have 2 twitches?
Disappearance of the second twitch (T4, T3, & T2 absent) OR you have 1 twitch?
A block of more than 75%-80%
80%-85%
90%-95%
What is the ideal degree of paralysis?
The ideal degree of paralysis necessary for any procedure with sufficient anesthetic depth is 85% to 95%. That correlates with 1 to 2 twitch responses present on TOF stimulation.
What is double-burst simulation?
Two short bursts of 50Hz tetanus separated by 0.75 sec
Which is easier to detect fade - TOF or double-burst?
Double-burst due to evaluating two twitches rather than four twitches
What indicates significant paralysis with double-burst?
Fade of the second impulse is comparable to TOFR of less than 0.6
What is tetanus?
Generally consists of rapid delivery of a 30-, 50-, or 100Hz stimulus for 5 seconds
Which degree of hertz is more reliable for detecting fade, but is not always specific?
100Hz
What is Posttetanic Count (PTC)?
50-Hz tetanus for 5 seconds, a 3 second pause, then single twitch for 1-Hz
A count less than _____ indicates a deep block, and prolonged recovery is likely
Eight!
**Used only when TOF and Double-burst stimulation is absent