Halothane Neuromuscular blockers

Isoflurane is a respiratory depressant (71). At concentrations which are associated with surgical levels of anesthesia, there is Htde or no depression of myocardial function. In experimental animals, isoflurane is the safest of the oral clinical agents (72). Cardiac output is maintained despite a decrease in stroke volume. This is usually because of an increase in heart rate. The decrease in blood pressure can be used to produce "deHberate hypotension" necessary for some intracranial procedures (73). This agent produces less sensitization of the human heart to epinephrine relative to the other inhaled anesthetics. Isoflurane potentiates the action of neuromuscular blockers and when used alone can produce sufficient muscle relaxation (74). Of all the inhaled agents currently in use, isoflurane is metabolized to the least extent (75). Unlike halothane, isoflurane does not appear to produce Hver injury and unlike methoxyflurane, isoflurane is not associated with renal toxicity. 

Halothane exerts a pronounced hypotensive effect, to which a negative inotropic effect contributes. Enflurane and isoflurane cause less circulatory depression. Halothane sensitizes the myocardium to catecholamines (caution serious tachyarrhythmias or ventricular fibrillation may accompany use of catecholamines as antihypotensives or toco-lytics). This effect is much less pronounced with enflurane and isoflurane. Unlike halothane, enflurane and isoflurane have a muscle-relaxant effect that is additive with that of nondepolarizing neuromuscular blockers. 

Isoflurane, an isomer of enflurane, together with sevoflurane are the most commonly used inhalation anesthetics in humans. Isoflurane does not sensitize the myocardium to catecholamines, has muscle relaxing action so less neuromuscular blocker is required and causes less hepatotoxicity and renal toxicity than halothane. 

Indications Neuromuscular blockade, endotracheal intubation Category Non-depolarizing neuromuscular blocker Half-life initial 2 minutes terminal 20 minutes Clinically important, potentially hazardous interactions with amikacin, aminoglycosides, anesthetics, antibiotics, gentamicin, halothane, kanamycin, neomycin, piperacillin, streptomycin, tobramycin... 

The effects of neuromuscular blockers are increased by inhalational anaesthetics, the greater the dosage of the anaesthetic the greater the increase in blockade. In broad terms desflurane, ether, enflurane, isoflurane, methoxyllurane and sevoflurane have a greater effect than halothane, which is more potent than cyclopropane, whereas nitrous oxide appears not to interact significantly with competitive blockers. " ... 

The dosage of the neuromuscular blocker may need to be adjusted according to the anaesthetic in use. For example, the dosage of atracurium can be reduced by 25 to 30% if, instead of balanced anaesthesia (with thiopental, fentanyl and nitrous oxide/oxygen)," enflurane is used, and by up to 50% if isoflurane or desflurane are used. Another study recommended reduced doses of neuromuscular blockers such as atracurium and tubocurarine in children undergoing anaesthesia with enflurane or isoflurane. In one study, enflurane and isoflurane reduced the vecuronium infusion rate requirements by as much as 70%, when compared with fentanyl anaesthesia. Another study demonstrated that although halothane and isoflurane could both increase the neuromuscular potency of vecuronium, only isoflurane prolonged the recovery from neuromuscular blockade. ... 

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