Action of scoline is potentiated by?
Correct Answer: Nitrous oxide
Description: Ans. A. Nitrous oxide. (Ref. Paul's anaesthesia 5th/pg. 427-428; Miller 7th/pg. 867)Paul's anaesthesia 5th/pg. 427-428 ..............'The mean dose of scoline producing 95% blockade (ED95) at the adductor pollicis is 0.30 to 0.35 mg/kg with opioid- nitrous oxide anesthesia. In the absence of nitrous oxide, the ED95 is increased to 0.5 mg/kg".DEPOLARIZING DRUGS: SUCCINYLCHOLINENeuromuscular Effects# depolarizes presynaptic, postsynaptic, and extrajunctional receptors.# Within 1 minute after succinylcholine injection and before paralysis is manifest, some disorganized muscular activity is observed frequently ("fasciculations") and is probably a result of depolarization of the nerve terminal produced by activation of presynaptic receptors.# In some muscles, like the masseter and to a lesser extent the adductor pollicis, a sustained increase in tension that may last for several minutes can be observed (spasm).Characteristics of Depolarizing Blockade# After injection of succinylcholine, single-twitch height is decreased. However, the response to high-frequency stimulation is sustained: minimal train-of-four and tetanic fade is observed. The block is antagonized by nondepolarizing agents so that the ED95 is increased by a factor two if a small dose of nondepolarizing drug is given before.# Succinylcholine blockade is potentiated by inhibitors of acetyl cholinesterase, such as neostigmine and edrophonium.# Phase II Block: After administration of 7 to 10 mg/kg, or 30 to 60 minutes of exposure to succinylcholine, train- of-four and tetanic fade become apparent. Neostigmine or edrophonium can antagonize this block, which has been termed "nondepolarizing," "dual," or "Phase II block." The onset of Phase II block coincides with tachyphylaxis, as more succinylcholine is required for the same effect.Pharmacology of Succinylcholine# Succinylcholine is rapidly hydrolyzed by plasma cholinesterase (also called pseudocholinesterase), with an elimination half-life of <1 minute in patients. Because of the rapid disappearance of succinylcholine from plasma, the maximum effect is reached quickly.# Plasma cholinesterase activity is reduced by some anticholinesterases (e.g., neostigmine) so that the duration of succinylcholine given after neostigmine, but not after edrophonium, is increased.Side Effects# Sinus bradycardia with nodal or ventricular escape beats.- Anaphylaxis# Fasciculations- Muscle Pains# increases intragastric pressure- Hyperkalemia# increases intraocular Pressure & ICP Clinical Uses# to facilitate tracheal intubation (adult dose of 1.0 mg/kg; Children are slightly more resistant to succinylcholine than adults, and doses of 1 to 2 mg/kg are required to facilitate intubation. In infants, 2 to 3 mg/kg may be required. Precurarization is not necessary in patients younger than 10 years).# "rapid sequence induction" ( patient with full stomach and possibility of aspiration).# Succinylcholine, at a dose of 4 mg/kg, is the only effective intramuscular neuromuscular blocking agent in children with difficult intravenous access and provides adequate intubating conditions in about 4 minutes. However, this route of administration should not be the method of choice.Additional Educational points:Sevoflurane:# Fast induction and emergence# Rapid changes in depth can be achieved.# Acceptability is good by pediatric patients (agent of choice for induction in children).# Hepatic blood flow is maintained.# Does not cause sympathetic stimulation and airway irritation even during rapid induction.# Amount of fluoride liberated is safe for kidney and liver.# Degraded by sodalime - hence not recommended for use in closed circuit.
Category:
Anaesthesia
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