Neuro muscular blockers
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Neuro muscular blockers

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    Neuro muscular blockers Neuro muscular blockers Presentation Transcript

    • Neuromuscular Blockers
      • Competitive Antagonists of the Nicotinic Receptor
      • e.g. curare (d-tubocurarine), vecuronium, pancuronium, atracurium, etc…
      • Depolarizing Blockers
      • e.g. succinylcholine, decamethonium
      www.freelivedoctor.com
    • www.freelivedoctor.com
    • www.freelivedoctor.com
    • D-tubocurarine pancuronium Vecuronium Decamethonium Succinylcholine Depolarizing Blockers Competitive Blockers www.freelivedoctor.com
    • Neuromuscular blockers differ from each other in:
      • Mechanism of action
      • Duration of action
      • Speed of onset and offset of action
      • Selectivity of action and safety margin
      • Adverse effects
      www.freelivedoctor.com
    • Classification of Blockers www.freelivedoctor.com Agent Pharmacological Properties Onset time (min) Duration (min) Elimination Succinylcholine Ultrashort acting; Depolarizing 1-1.5 6-8 Plasma cholinesterase D-tubocurarine Long duration; Competitive 4-6 80-120 Renal and liver Atracurium Intermediate duration; Competitive 2-4 30-40 Plasma cholinesterase Mivacurium Short duration; Competitive 2-4 12-18 Plasma cholinesterase Pancuronium Long duration; Competitive 4-6 4-6 Renal and liver Rocuronium Intermediate duration; competitive 1-2 1-2 Renal and liver
    • Muscle AP Nerve AP Left Leg Muscle Stimulation Right Leg Nerve Stimulation Right Leg Muscle Stimulation Site of Action of d-Tubocurarine www.freelivedoctor.com
    • G: gallamine; TC: tubocurarine; NEO: neostigmine; S: succinylcholine. Non-depolarizing Block www.freelivedoctor.com
    • Depolarizing Block C10: decamethonium TC: tubocurarine NEO: neostigmine S: succinylcholine www.freelivedoctor.com
    • Comparison of Competitive and Depolarizing Blocking Agents www.freelivedoctor.com Competitive Depolarizing Effect of previous d-tubocurarine Additive Antagonistic Effect of previous decamethonium None/antagonistic May be additive Efect of cholinesterase inhibitors Reverse No antagonism Effect on motor end plate Elevated threshold to Ach; no depolarization Partial, persisting depolarization Initial excitatory effect None Transient fasciculations Effect of KCl or tetatnus on block Transient reversal No antagonism
    • Dual Block by Depolarizing Agents C10: decamethonium; NEO: neostigmine; TC: tubocurarine NEO reversed the blockade by C10. www.freelivedoctor.com
    • Depolarizing Blocker Competitive Blockade Competitive Blocker Noncompetitive Blockade (desensitization) (electrogenic Na pump) (direct channel block) Changing Nature of Neuromuscular Blockade www.freelivedoctor.com
    • Sequence of Paralysis Fingers, orbit (small muscles) limbs Trunk neck Intercostals Diaphragm Recovery in Reverse www.freelivedoctor.com
    • Other Effects of Neuromuscular Blockers
      • Action at Autonomic Ganglia
      • e.g. d-tubocurarine blocks,
      • succinylcholine may stimulate
      • newer agents have less ganglionic effects
      • Histamine Release
      • e.g. d-tubocurarine
      • bronchospasm, bronchial and salivary secretions
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    • Adverse Effects/Toxicity
      • Hypotension
      • Decreased tone and motility in GI tract
      • Depolarizing agents can cause increased K efflux in patients with burns, trauma, or denervation and lead to hyperkalemia
      • Prolonged apnea (many reasons, check for pseudochlinesterase genetic polymorphism)
      • Malignant hyperthermia (succinylcholine + halothane especially)
      • Sinus bradycardia/junctional rhythm (with succinylcholine)
      www.freelivedoctor.com
    • Systolic BP Systolic BP % Change in Systolic BP with d-Tubocurarine as a Function of Dose and Depth of Anesthesia Increasing Dose of d-tubocurarine Increasing Depth (% Halothane) 0.25% 0.5% 0.75% 6 mg/m 2 12 mg/m 2 18 mg/m 2 www.freelivedoctor.com
    • Influence of Type of Anesthetic on Enhancement of Neuromuscular Blockade By d-Tubocurarine www.freelivedoctor.com
    • HR CO SVR MAP Hemodynamic Effects of d-Tubocurarine and Pancuronium www.freelivedoctor.com
    • www.freelivedoctor.com
    • Drug Interactions
      • Cholinesterase Inhibitors (antagonize competitive and enhance depolarizing)
      • Inhalational Anesthetics (synergistic)
      • Aminoglycoside Antibiotics (synergistic)
      • Calcium Channel Blockers (synergistic)
      www.freelivedoctor.com
    • Therapeutic Uses
      • Adjuvant in surgical anesthesia
      • Orthopedic procedures for alignment of fractures
      • To facilitate intubations – use one with a short duration of action
      • In electroshock treatment of psychiatric disorders
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