Skeletal muscle relaxants nondepolarizing

Muscle contraction responses to different patterns of nerve stimulation used in monitoring skeletal muscle relaxation. The alterations produced by a nondepolarizing blocker and depolarizing and desensitizing blockade by succinylcholine are shown. In the train of four (TOF) pattern, four stimuli are applied at 2 Hz. The TOF ratio (TOF-R) is calculated from the strength of the fourth contraction divided by that of the first. In the double burst pattern, three stimuli are applied at 50 Hz, followed by a 700 ms rest period and then repeated. In the posttetanic potentiation pattern, several seconds of 50 Hz stimulation are applied, followed by several seconds of rest and then by single stimuli at a slow rate (eg, 0.5 Hz). The number of detectable posttetanic twitches is the posttetanic count (PTC)., first posttetanic contraction. 

Gallamine, a nondepolarizing neuromuscular blocking agent (1 mg/kg IV), is used as an adjunct to anesthesia to induce skeletal muscle relaxation, facilitate intubation and mechanical ventilation, reduce fractures and dislocations, and to weaken muscle contractions in pharmacologically or electrically induced convulsions (see also Figure 99). 

Anesthesia with halothane causes some relaxation by central depression in addition, the duration and magnitude of the muscular relaxation induced by nondepolarizing skeletal muscle relaxants such as tubocurarine or pancuronium are increased (see also Figure 99). 

Metocurine, a skeletal muscle relaxant, is indicated as an adjunct to anesthesia, to facilitate endotracheal intubation (0.2 to 0.4 mg/kg), and to reduce the intensity of muscle contraction in pharmacologically or electrically induced convulsions. Metocurine is a methyl analog of tubocurarine, which produces nondepolarizing (competitive) neuromuscular blockade. 

Mivacnrinm, a nondepolarizing nenromuscular-blocking agent (0.15 mg/kg IV pnsh in 5 to 15 seconds), is used as an adjnnct to general anesthesia to facilitate endotracheal intubation and to provide skeletal muscle relaxation during surgery or mechanical ventilation (see also Figure 99). 

Explain the mechanism of action of a nondepolarizing blocker in skeletal muscle relaxation. 

Muscle Enflurane produces significant skeletal muscle relaxation and noticeably enhances the effects of nondepolarizing muscle relaxants. As with other inhalational agents, enflurane relaxes uterine smooth muscle. 

De urane produces direct skeletal muscle relaxation and enhances the effects of nondepolarizing and depolarizing neuromuscular blocking agents. Consistent with its minimal metabolism, desflurane has no reported nephrotoxicity or hepatotoxicity. 

Muscle Sevoflurane produces skeletal muscle relaxation and enhances the effects of nondepolarizing and depolarizing neuromuscular blocking agents. 

The skeletal muscle relaxants provide muscle relaxation and/or immobility via N-receptor interactions. Most, including otubocurarine, atracurium, and mivacurium, are competitive and nondepolarizing and can be reversed by AQiE inhibitors. Sucdnylcholine is a depolarizing, noncompetitive agonist... 

Nondepolarizing blockers are used to relax skeletal muscle for surgical procedures, to prevent dislocations and fractures associated with electroconvulsive therapy, and to control muscle spasms in tetanus. They do not produce anesthesia or analgesia. 

Musck Halothane causes some relaxation of skeletal muscle via its central depressant effects and potentiates the actions of nondepolarizing muscle relaxants (curariform drugs see Chapter 9), increasing both their duration of action and the magnitude of their effect. Halothane and the other halogenated inhalational anesthetics can trigger malignant hyperthermia this syndrome frequently is fatal and is treated by immediate discontinuation of the anesthetic and administration of dantrolene. 

Muscle Isoflurane produces some relaxation of skeletal muscle via its central effects. It also enhances the effects of depolarizing and nondepolarizing muscle relaxants. Isoflurane is more potent than halothane in its potentiation of neuromuscular blocking agents. The drug relaxes uterine smooth muscle and is not recommended for analgesia or anesthesia for labor and vaginal delivery. 

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