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16 Cards in this Set
- Front
- Back
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Neuromuscular blockers- Depolarizers
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Succinylcholine/Anectine
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Neuromuscular blockers- NonDepolarizers
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Mivacron/Mivacuronium
Zemuron/Rocuronium Norcuron/Vecuronium Pavulon/Pancuronium Nimbex/Cisatracurium |
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Neuromuscular Blockers-Depolarizing (phase I) block
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Muscle fasciculation precedes the onset of neruromuscular blockade
Sustained response to tetanic stimulation Block is potentiated by anticholinesterase drugs |
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Neuromuscular Blockers- Nondepolarizing (phase II) block
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No fasciculations
Reversal with anticholinesterase drugs |
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Terminology
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 |
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Neuromuscular Monitoring Modalities
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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 |
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Why do we Monitor PNS & How
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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. |
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PNS site placement
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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 |
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Mechanomyography
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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. |
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Electromyography
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Using electrodes on the hand and arm, a muscle’s action potential or electrical activity during a contraction is measured and recorded.
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Acceleromyography
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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. |
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Train of Four Fade
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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 |
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Train of Four Fade #2
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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. |
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Tetanic Stimulation
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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 |
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Recovery Tests
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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 |
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Recovery Tests #2
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Sustained tetanic response to 50 Hz for 5 seconds
TOF ratio >.90 w/ no fade No fade to double burst stimulation |
