ABSTRACT
BACKGROUND: Vecuronium and Pancuronium have been proven to be associated with nicotinic receptor of skeletal muscle. Generally, nondepolarizing muscle relaxant is associated with contraction of smooth tracheal muscle, but there have been few studies about effects of nondepolarizing muscle relaxant on the smooth tracheal muscle. METHODS: We studied the acetylcholine dose response curve of the tracheal smooth muscle contraction and effects of propranolol, L-NAME after pretreating with vecuronium and pancuronium. RESULTS: Vecuronium shifted the acetylcholine dose-response curve of the tracheal contraction to the left, and pancuronium shifted the curve to the right. Vecuronium and Pancuronium reduced the contraction of smooth tracheal muscle with the use carbachol. Propranolol and L-NAME had no effect on the contraction of smooth tracheal muscle after pretreating with vecuronium and pancuronium. CONCLUSION: We suggest that vecuronium has an anticholinergic effect, while pancuronium has some effect on the muscarinic receptor in addition to its anticholinergic effect.
Subject(s)
Animals , Rats , Acetylcholine , Carbachol , Muscle, Skeletal , Muscle, Smooth , NG-Nitroarginine Methyl Ester , Pancuronium , Propranolol , Receptors, Muscarinic , Receptors, Nicotinic , Trachea , Vecuronium BromideABSTRACT
BACKGROUND: Non-depolarizing muscle relaxants have their muscle relaxing effect by competing with acetylcholine (ACh) at the nicotinic receptor level. What are the effects of such muscle relaxants on the tracheal smooth muscle? This present study was set up to address the question as to how vecuronium and pancuronium influence the tracheal smooth muscle. METHODS: Sixty male Sprague-Dawley rat tracheal smooth muscles were isolated at optimal length for isometric force. The preparations were set up in an organ bath containing Tyrode's solution. And isometric force displacement transducer and physiograph were used to record the change in force. After the equilibration period the preparations were contracted with ACh 10(-5) M and carbachol 3x10(-7)M seperately. The preparations were washed with fresh tyrode's solution and allowed to return passively to resting tone. Then the cumulartive effect of ACh (from 3 10(-7) M through 10(-5) M) and carbachol (CCh, from 10(-8) M through 3 10(-6) M) were produced before and after pretreating the preparation with vecuronium (10(-5) M and 10(-6) M) and pancuronium (10(-5) M and 10(-6) M) respectively. Also, we studied the changes of contraction produced by neostigmine before and after pretreatment with vecuronium (10(-5) M and 3 10(-5) M) and pancuronium (3 10(-6) M and 3 10(-5) M). RESULTS: Vecuronium shifted the ACh dose-response curve of the tracheal contraction to the left (p0.05). CONCLUSIONS: Vecuronium inhibits the ACh hydrolyzing enzyme, especially acetylcholinesterase. Therefore it potentiates ACh contraction in the tracheal smooth muscle, but not the CCh contraction, while pancuronium has a different effect in comparison with vecuronium. That is, at a low concentration it reveals an antagonistic effect on the muscarinic M2 receptor and at a higher concentration it has an antagonistic effect on the muscarinic M3 receptor in the tracheal smooth muscle.
Subject(s)
Animals , Humans , Male , Rats , Acetylcholine , Acetylcholinesterase , Baths , Carbachol , Muscle, Smooth , Neostigmine , Neuromuscular Nondepolarizing Agents , Pancuronium , Rats, Sprague-Dawley , Receptor, Muscarinic M2 , Receptor, Muscarinic M3 , Receptors, Nicotinic , Transducers , Vecuronium BromideABSTRACT
BACKGROUND: High dose fentanyl for cardiac surgery in neonates, infants and children can cause severe bradycardia and chest wall rigidity that result in decreased cardiac output and oxygen desaturation due to fixed stroke volume in pediatric patients. To ameliorate the effects of fentanyl, it is common to administer neuromuscular blocking drugs with wanted cardiovascular side effects. This study was designed to compare the cardiovascular variables and oxygen saturation among different muscular relaxants in high dose fentanyl anesthesia. METHODS: Thirty pediatric cardiac patients were allocated randomly into three muscle relaxant groups treated with 0.2 mg/kg pancuronium (n=10), 0.2 mg/kg vecuronium (n=10) or 0.2 mg/kg pipecuronium (n=10) after receiving an initial bolus dose of 25 g/kg of fentanyl. Changes of heart rate (HR), mean arterial blood pressure (MAP), rate-pressure-product (RPP) and oxygen saturation (SpO2) were observed. The same cardiovascular variables were also observed 1 and 2 minutes after the second bolus dose of 25 g/kg fentanyl and compared to the results among muscle relaxants. RESULTS: HR, MAP and RPP decreased significantly (p<0.05) 1 and 2 minutes after injection of the 1st fentanyl, which returned to levels above the control value after administration of pancuronium, vecuronium or pipecuronium. Among muscle relaxants, pancuronium caused the most rapid and significantly high level compared to the control value in HR and MAP. Next was pipecuronium and then vecuronium. In clinical setting, SpO2 was decreased after the 1st fentanyl injection and increased after the injection of muscle relaxants, but not significant statistically. CONCLUSION: In view of hemodynamic changes, pancuronium is most efficient and rapid in returning the hemodynamic variables that was decreased after high dose fentanyl anesthesia in neonates, infants and children whose cardiac output was dependent on HR due to relatively fixed stroke volume.