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16 Cards in this Set

  • Front
  • Back
Neuromuscular blockers- Depolarizers
Neuromuscular blockers- NonDepolarizers
Neuromuscular Blockers-Depolarizing (phase I) block
Muscle fasciculation precedes the onset of neruromuscular blockade
Sustained response to tetanic stimulation
Block is potentiated by anticholinesterase drugs
Neuromuscular Blockers- Nondepolarizing (phase II) block
No fasciculations
Reversal with anticholinesterase drugs
Onset time
Clinical duration
Total duration of action
Recovery index
Train-of-four ratio
Onset time: time from drug administration to maximum effect
Clinical duration: time from drug administration to 25% recovery of the twitch response
Total duration of action: time from drug administration to 90% recovery of twitch response
Recovery index: time from 25% to 75% recovery of the twitch response
Train-of-four ratio: compares the fourth twitch of a train of four with the first twitch; when the fourth twitch is 90% of the first, recovery is indicated
Neuromuscular Monitoring Modalities
Single twitch: A single supramaximal electrical stimulus ranging from .1-1 Hz
Train-of-four: A series of four twitches at 2 Hz every half-second for 2 seconds (most common)
Tetanus: Generally consists of rapid delivery of a 30, 50, or 100 Hz stimulus for 5 seconds
Post-tetanic count: 50 Hz tetanus for 5 seconds, a 3 second pause, then single twitches of 1 Hz
Double-burst stimulation: two short burst of 50 Hz tetanus separatated by .75 seconds
Why do we Monitor PNS & How
During surgery, we assess the level of neuromuscular blockade.
Individual responses my vary tremendously.
Surgeon needs to be confident before making incision.
The CRNA needs to be in control: intubation, degree of relaxation, additional doses of NMBA, time for reversal agent, extubation & possible residual paralysis.
PNS site placement
Primary site for monitoring is the ulnar nerve.
Stimulating electrodes are placed on the ulnar nerve which is located in the forearm and controls the movement of the thumb, fourth & fifth finger.
orbicularis occuli is the next common- next to the eye
Using a transducer, the force of contraction of the thumb is recorded.
This is the “Gold Standard” for scientific studies due to its accuracy & reliability.
Using electrodes on the hand and arm, a muscle’s action potential or electrical activity during a contraction is measured and recorded.
A transducer that measures the speed of the muscle contraction (acceleration) is placed on the tip of the thumb.
This is the method of the TOF watch.
Train of Four Fade
4/4 Twitches = 0£75% Receptors are blocked
3/4 Twitches = 75-80% Receptors are blocked
2/4 Twitches = 80-90% Receptors are blocked
1/4 Twitches = 90-95% Receptors are blocked
0/4 Twitches = 95-100% Receptors are blocked
we like “to live” at 1 twitch; we cannot reverse the drug if we do not have at least one twitch; if we try, it will prolong the twitch
Train of Four Fade #2
Normal (without a SMR): 4 responses of equal twitch height

Non-depolarizing: With a NDMR, each successive twitch height will be smaller than the previous one --> this is referred to as “fade”

Depolarizing: With a DMR, all twitch heights will be equal, “no fade”. This is because the mechanism of action of a depolarizing agent is similar to a “normal” Ach response. Both cause a depolarizing action.
Tetanic Stimulation
More reliable form of measuring neuromuscular blockade
Fully drains the muscle tissue of ACh
Single twitches are administered until there is no response
Quantity of twitches after tetanus determine the depth of the block
May also determine when a twitch will come back, showing at least some recovery
Recovery Tests
how to test if the nm blocker is worn off- in addition to the n stimulator
5 second head/leg lift –diff. if still too asleep
Strong hand grip
Cough- James doesn’t like
Respond to name – not good for nm offset testing
Adequate TV & RR
Unlabored respirations
NIF >25 cm H2O
Head lift: still approximately 30% blockade which is still tolerable for patient
Strong hand grip: maintaining a strong hand grip shows an ability to maintain muscle control
Cough: displays an ability to move diaphragm and push air. Movement of diaphragm enables patient to control breathing.
-we hesitate to reverse nm’s because the med has its own side effects
Recovery Tests #2
Sustained tetanic response to 50 Hz for 5 seconds
TOF ratio >.90 w/ no fade
No fade to double burst stimulation