Neuromuscular block, Anesthesia Flashcards
2 groups of neuromuscular blocking drugs
- Neuromuscular blockers -Muscle paralysis
-work at the neuromuscular end plate, don’t act on CNS
-structurally resemble acetylcholine
Ex. Succinylcholine is a depolarizing agent
Pancuronium - nondepolarizing (steroid derivative) - Spasmolytics - Spasticity reducers
Neuromuscular blocking drugs: elimination by the plasma
Succinylcholine
Most potent neuromuscular blocking drugs
- Pancuronium (kidney elim) [6]
- Vecuronium (kidney and liver elim) [6]
Which NBD is the guide for potency
Tubocurarine* (Isoquinoline derivatives)
Pharmacokinetics of NBD
- Given IV
- Rapid distribution phase
- Slow elimination phase
- Kidney excreted drugs have the longer half-lives
- Liver eliminated drugs have shorter half-lives/durations of action
Succinylcholine
-Only depolarizing NBD
-agoninst at nicotinic acetylcholine receptors (may stimulate nicotinic ACh and cardiac muscarinic
Effect: transient contractions, followed by prolonged flaccid paralysis*
Uses: endotracheal tube placement
***Rapid metabolism in the plasma by plasma cholinesterase (duration ~5 min)
Succinylcholine: toxicities
- Arrhythmia
- Hyperkalemia
- Increased intraocular pressure
- postoperative muscle pain
Flaccid paralysis
patient is not breathing on their own
d-Tubocurarine (non-depolarizing)
- competitive antagonist at nACh receptors
- causes flaccid paralysis
- histamine release**
Non-depolarizing neuromuscular blocking agents
- d-Tubocurarine
- Cisatracurium
- Rocuronium
- Vecuronium
Uses: 1. intubation 2. maintain skeletal muscle relaxation during surgery
-small rapidly moving muscle in face, eyes are affected first, then fingers, toes, extremities, trunk, intercostals. Diaphragm last!* (sequence reverses coming out of paralysis)
What can be given to shorten duration of neuromuscular blockade?
cholinesterase inhibitors
ex. neostigmine, pyridostigmine
(these are given with atropine to void the cardiac slowing effect)
Non-depolarizing neuromuscular blockade
- Aminoglycoside
(ex. gentamicin, tobramycin)
- act synergistically to enhance neuromuscular blockade - CCB
(ex. Verapamil)
- enhance neuromuscular blocking effects of non-depolarizing agents
General anesthesia
state of unconsciousness, analgesia, and amnesia, with skeletal muscle relaxation and loss of reflexes
Stages of Anesthesia
- Analgesia
- Disinhibiition
- Surgical Anesthesia
- Medullary Depression
Stage 1: Analgesia
- decreased awareness of pain
- Consciousness impaired but not lost
Stage 2: Disinhibition
- delirious and excited
- Amnesia
- Enhanced reflexes
- Irregular respirations
- Retching
- May have incontinence
Stage 3: Surgical Anesthesia
- unconscious
- No pain reflexes
- regular respirations
- BP maintained
Stage 4: Medullary Depression
- Severe respiratory depression
- Severe cardiovascular depression
What are the 5 primary effects of general anesthetics
- Unconsciousness
- Amnesia
- Analgesia
- Inhibition of autonomic reflexes
- Skeletal muscle relaxation
Inhaled anesthetics
- Desflurane
- Enflurane
- Halothane
- Isoflurane
- Sevoflurane
- Nitrous oxide
Inhaled anesthetics: effects
- increase cerebral blood flow*
- Enlurane and halothane decrease CO
-ALL decrease respiratory functions
- concentration-dependent decrease in portal vein blood flow
- Lung irritation (desflurane)
rate of onset and recovery for inhaled anesthetics vary by what?
blood:gas partition coefficient
Drugs of choice in patient with underlying airway problems
- Halothane
- Sevoflurane
What is the preferred method of inducing rapid anesthesia in adults?
IV
but IV is not the preferred method in kids
IV anesthetics: Barbiturates
- High lipid solubility***
- fast onset
- short duration
IV anesthetics: Benzodiazepines (ex. Midozolam)
- slower onset than barbiturates
- longer duration than barbiturates
- post operative respiratory depression reversed by flumazenil
IV anesthetics: Dissociative (ex. Ketamine)
-blocks glutamate (excitatory)
-analgesia, amnesia, and catatonia - but- consciousness retained
-CV stimulation
ADE: increased ICP
IV anesthetics: Imidazole (ex. Etomidate)
- short duration
- no analgesia (painful injection)**
IV anesthetics: Opiods (ex. Fentanyl, Alfentanil, Remifentanil, Morphine)
- marked analgesia
- respiratory depression
IV anesthetics: Phenols (Ex. Propofol, Fospropofol)
-Fast onset
-Fast recovery
ADE: hypotension, cardiovascular depression
