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29 Cards in this Set
- Front
- Back
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List 5 general uses for neuromuscular relaxants.
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1. Treatment of muscle spasms
2. Relaxation of tracheal muscles during intubation 3. Relaxation of muscles during ventilation 4. Relaxation of large muscle groups which must be retracted during surgery. 5. Relaxation of muscles during ECT |
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Outline neuromuscular transmission.
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-AP travels down axon
-AP triggers release of NT vesicles via Ca2+ release -NT binds to Na+ channels on muscle fiber to produce an EPP -If enough EPP's are present an AP is created which proplgates down the muscle. -Ca2+ is released from SR once AP travels down a T-tubule -Ca2+ triggers muscle contraction by exposing actin once it binds to troponin |
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What are the 2 types of neuromuscular relaxants?
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Non-depolarizing (competitive antagonists)
Depolarizing (agonists, Na2+ channels cant recover) |
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Selection of an appropriate muscle relaxant is often based on what parameter?
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Halflife
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Classify the big 4 NM relaxants into long, medium and, short halftimes
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Long (2 hours): Pancuronium
Medium (1 hour): Rocuronium, Vecuronium Short (minutes): Mivacuronium |
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Rank the speed of the different types of possible elimination for NM relaxants from highest to lowest.
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Plasma (AChE) > Hepatic > Renal
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The two medium speed NM relaxants differ in their elimination how?
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Rocuronium is primarily metabolized in the liver. While Vecuronium is metabolized by all 3 pathways (primarily plasma).
Meaning that in liver failure patients Vecuronium is a better choice. |
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NM blockade is unique in that drug concentrations must be high, why?
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Muscle tissue exhibits a large receptor reserve. Thus, a small release of Ach can cause contraction.
The result is that you need a lot of drug to make sure this doesn't happen. As an ascide, larger muscles (diaphragm) exhibit a larger reserve than smaller muscles (facial) |
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Suppose you want to comfortably intubate a patient, what are good NM relaxant choices?
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Mivacuronium or Rocuronium
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What are the side effects of NM relaxants
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Not analgesic, apnea, histamine release (mivacuronium only), tachycardia (pancuronium and rocuronium)
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What are some of the major drug interactions of non-depolarizing NM relaxants.
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They enhance the effects of gas anesthetics. They enhance the effects of antibiotics (aminoglycosides)
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Suppose you want to reverse a NM relaxant, what would you use and why?
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Neostigmine and glycopyrrolate.
Neostigmine is an AChE inhibitor, allowing you to overwhelm the relaxant. Glycopyrrolate is a muscarinic antagonist. This will reduce the unwanted effects that the Neostigmine would have on muscarinic receptors. |
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What is succinylcholine? How does a PT on it behave?
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It is a depolarizing NM relaxant. A patient will initially have muscle flickering followed by flaccid paralysis.
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Would you used succinylcholine for long or short use? Why?
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Short use. Long term it can lead to phase II block where the receptors are insensitive to Ach. This is hard to predict and control
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Succinylcholine has an advantage over non-depolarizing NM relaxants. What is it?
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Fast time to effect, fast time to release. Good for fast procedures such as intubation
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What are the side effects of succinylcholine?
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Non analgesic, apnea, muscle pain, tachycardia and HTN.
Hyperkalemia in burn (immediate) and crush injury (if used days later) patients due to K+ release from motor end plate |
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What are the contraindications of succinylcholine?
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History of malignant hyperthermia, early in burns, days after crush injury, skeletal muscle myopathies
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Spasmolytic drugs function by what mechanism?
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Inhibition of the Ia afferent fibers. This is done typically by GABAergic drugs
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What is Baclofen? What are its effects?
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It is a GABA b receptor agonist. It inhibits the stretch reflex by reducing Ca2+ influx at the presynaptic nerve terminal.
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What are the indications of Baclofen?
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MS, Spinal cord spasticity
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What are the toxicities of Baclofen?
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Altered mental state, drowsiness
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How do benzodiazapines work?
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They work by increasing the effect of endogenously stimulated GABA a channels.
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What is diazepam? What are its effects?
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It is a benzodiazapine, it is a spasmolitic drug that works by increasing GABA a activity.
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What are the indications of diazepam?
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Muscle spasms, MS
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What is the contraindication of diazepam?
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Glaucoma
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How to Tizanidine and Clonidine work as anti spasmolitics?
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They are both A2 agonists. They function by upregulating pre and post synaptic nerves in the spinal cord
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What is dantroline? What is its physiological effect?
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Dantroline is a spasmolitic drug. It functions rather uniquely by blocking Ca2+ release from the SR of skeletal muscle
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What is the predominant use of dantroline?
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To reverse malignant hyperthermia, a rare genetic side effect of Succinylcholine.
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What are the toxicities of dantroline?
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Muscle weakness, hepatitis, sedation
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