Inhalation anaesthetics halothane

A nonconventional synthesis of the known inhalation anaesthetic, 2-bromo-2 chloro-l,l,l-trifluoroethane (Halothane), based on the reaction of ethyl 1,2 di bromo-1,2-dicliloroethyl ether with anhydrous hydrogen fluoride and sulfur tetrafluoride, has been patented The reaction presumably involves cleavage of the ether linkage, followed by fluorination of the intermediate bromochloroacetyl halide with sulfur tetrafluoride, ethyl halides are the by-products [2] (equation 2)... 

While ionophore-stimulated 5-LO product release from neutrophils is often used as an indication of 5-LO inhibition, one must interpret these results cautiously. For example, halothane, an inhalation anaesthetic which may cause membrane perturbation [26], and colchicine, a microtubule disrupter [27], both were active, but presumably not because of 5-LO inhibition. A23187 is assumed to stimulate 5-LO by raising the intracellular calcium level, but this agent causes many other effects which may or may not be related to 5-LO activation, including changes in membrane potential, protein phosphorylation, phospholipid turnover, cyclic nucleotide levels, and DNA and protein synthesis [28]. Also, the effects of some putative 5-LO inhibitors on product release from neutrophils has been shown to vary with the stimulant used [29]. 

It is a clear, colourless liquid with a sweet and fruity odour. It is noninflammable and non-explosive in air or oxygen in anaesthetic concentrations. It is the most potent inhalational anaesthetic which has a good analgesic and muscle relaxant properties. Renal blood flow, glomerular filtration rate and urine flow are reduced as with the halothane. 

INHALATIONAL -HALOTHANE OXYTOCICS Report of arrhythmias and cardiovascular collapse when halothane was given to patients taking oxytocin Uncertain possibly additive effect. High-dose oxytocin may cause hypotension and arrhythmias Monitor PR, BP and ECG closely give oxytocin in the lowest possible dose. Otherwise consider using an alternative inhalational anaesthetic... 

Inhalation anaesthetics are either gases or volatile liquids. Apart from nitrous oxide, which is still widely used, earlier inhalation anaesthetics are no longer used. Ether is not suitable because it is explosive and irritant to the respiratory tract. Chloroform cannot be used because it is toxic to the liver. Inhalation anaesthetics currently in use are the volatile liquids halothane (since 1956) and more recently isoflurane, desflurane and sevoflurane and nitrous oxide gas. 

Antimuscarinic drugs are used as premedication to prevent salivation and bronchial secretions during an operation and to protect the heart from arrhythmias caused by inhalation anaesthetics such as halothane and propofol. They are less commonly used nowadays because modern anaesthetics are less irritant. 

What are the advantages of the inhalation anaesthetics isoflurane, desflurane and sevoflurane over the older ones ether, chloroform and halothane ... 

It is the weakest but the safest inhalation general anaesthetic. It is usually administered in con-jrmction with other potent inhalation anaesthetics, such as methoxyflurane and halothane. However,... 

In a study in 20 healthy patients the concurrent use of either halothane or isoflurane increased the serum concentrations of propofol by about 20% during the maintenance of general anaesthesia. The US manufacturer of propofol notes that inhalational anaesthetics (such as halothane or isoflurane) would be expected to increase the effects of propofol. The man-... 

It used to be thought that beta bloekers should be withdrawn from patients before surgery beeause of the risk that their cardiac depressant effects would be additive with those of inhalational anaesthetics, resulting in a reduction in cardiac output and blood pressure, but it seems that any effect depends on the anaesthetic used. It has been suggested that the ranking order of compatibility (from the least to the most compatible with beta blockers) is as follows methoxyflurane, ether, cyclopropane, trichloroethylene, enflurane, halothane, isoflurane. ... 

Patients anaesthetised with inhalational anaesthetics (particularly cyclopropane and halothane, and to a lesser extent desflurane, enflurane, ether, isoflurane, methoxyflurane, and sevoflurane) can develop cardiac arrhythmias if they are given adrenaline (epinephrine) or noradrenaline (norepinephrine), unless the dosages are very low. Children appear to be less susceptible to this interaction. file addition of adrenaline to intrathecal tetracaine enhances the sedative effects of propofol. 

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. " ... 

Phenylephrine is a sympathomimetic, and as such may carry some risk of potentiating arrhythmias if it is used with inhalational anaesthetics such as halothane -see Anaesthetics, general + Inotropes and Vasopressors , p.99. However, it is considered that it is much less likely than adrenaline (epinephrine) to have this effect, since it has primarily alpha-agonist activity. ... 

Metabolites possibly play a role in the pathogenesis of liver injury. The biotransfor-matioh of inhalation anaesthetics has recently been extensively reviewed (20 <). Another cause of liver damage after halothane exposure may be the slowing of the hepatic blood flow, which was demonstrated angiographically in 2 children (21 ). 

Two methods of anaesthesia are currently in use, the application of inhaled gaseous or volatile anaesthetics such as halothane, sevoflurane and isoflurane to maintain a level of anaesthesia. Older compounds in this category include nitrous oxide and chloroform. 

Inhalation general anaesthetics, such as halothane, stimulate CICR in a way similar to that of caffeine. Administration of these agents to patients with MH mutations in RyRl gene will cause the MH episodes. 

Halothane was introduced into clinical practice in 1956. It was not the first fluorinated anaesthetic— fluoroxene (Fluoromar) holds that distinction—but it was the first to achieve widespread acceptability. Halothane is a fluorinated alkane 1-bromo, 1-chloro -2,2,2-trifluoroethane (Figure 3.2). It has a characteristic odour, similar to chloroform, and requires a stabiliser, thymol (0.01%), to prevent degradation by light. Halothane has a blood/gas partition coefficient of 2.4 able 3.2) but its lack of irritant qualities makes possible the use of relatively high inspired concentrations (2-4%). For that reason, inhalation induction is characteristically smooth and rapid. Compared to sevoflurane, and possibly isoflurane, recovery from halothane anaesthesia is delayed. 

INHALATIONAL- HALOTHANE TERBUTALINE, THEOPHYLLINE Cases of arrhythmias when these bronchodilators are co-administered with halothane Possibly due to sensitization of the myocardium to circulating catecholamines by the volatile anaesthetics to varying degrees Risk of cardiac events is higher with halothane. Desflurane is irritant to the upper respiratory tract, and t secretions can occur and are best avoided in patients with bronchial asthma. Sevoflurane is non-irritant and unlikely to cause serious adverse effects... 

Isoflurane is a volatile colourless liquid, which is not flanamable at normal anaesthetic concentrations. It is relatively insoluble, and has a lower blood/gas coefficient than halothane or enflurane, which allows rapid adjustment of the depth of anaesthesia. It has a pungent odour and can cause bronchial irritation, which makes inhalational induction unpleasant. Isoflurane is minimally metabolised (0.2%), and none of the breakdown products has been related to anaesthetic toxicity. 

Halothane has the highest blood/gas partition coefficient of the volatile anaesthetic agents and recovery from halothane anaesthesia is comparatively slow. It is pleasant to breathe and is second choice to sevoflurane for inhalational induction of anaesthesia. Halothane reduces cardiac output more than any of the other volatile anaesthetics. It sensitises the heart to the arrhythmic effects of catecholamines and hypercapnia arrhythmias are common, in particular atrioventricular dissociation, nodal rhythm and ventricular extrasystoles. Halothane can trigger malignant hyperthermia in those who are genetically predisposed (see p. 363). 

GENERAL ANAESTHETICS are either inhaled or injected agents and produce insensibility, mostly to alleviate pain during surgical procedures (e.g. halothane, thiopentone sodium). 

Gases of interest are nitrous oxide and the inhalation vapours (or volatile halogenated anaesthetics) such as halothane (CF3CHBrCl), isoflurane (CHF2OCHCICF3) and enflurane (CHCIFCF2OCHF2). In this section electrochemical studies on nitrous oxide, halothane and isoflurane will be discussed. 

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