Anaesthetics, general inhalational

CALCIUM CHANNEL BLOCKERS ANAESTHETICS -GENERAL, INHALATIONAL t hypotensive effects of dihydropyridines, and hypotensive/bradycardic effects of diltiazem and verapamil Additive hypotensive and negative inotropic effects. General anaesthetics tend to be myocardial depressants and vasodilators they also 1 sinus automaticity and AV conduction Monitor BP and ECG closely... 

Most of the anticholinergic drugs which cause delirium have prominently antimuscarinic actions. However, nicotinic receptors are also present in the brain. Mecamylamine, a nicotinic receptor antagonist which penetrates the brain to some extent, has produced delirium (Paykel et al., 1982). Furthermore, general (inhalational) anaesthetics, which by definition decrease arousal, target nicotinic receptors among others (Chapter 9). Conversely, nicotine itself increases arousal and selective attention (Ashton, 1992b). 

AMIODARONE ANAESTHETICS - GENERAL Amiodarone may t the myocardial depressant effects of inhalational anaesthetics Additive effect Monitor PR, BP and ECG closely... 

DIRECT ANAESTHETICS-GENERAL 1. Risk of arrhythmias when inhalational anaesthetics are coadministered with epinephrine or norepinephrine 2. Case report of marked t BP when phenylephrine eye drops given during general anaesthesia... 

ANAESTHETICS-GENERAL INDIRECTLY ACTING SYMPATHOMIMETICS (e.g. methylphenidate) 1. Risk of arrhythmias when inhalational anaesthetics are co-administered with methylphenidate 2. Case report of 1 sedative effect of midazolam and ketamine by methylphenidate 1. Uncertain attributed by some to sensitization of the myocardium to sympathomimetics by inhalational anaesthetics 2. Uncertain at present possibly due to CNS stimulation caused by methylphenidate (hence its use in narcolepsy) Avoid giving methylphenidate on the day of elective surgery... 

OXYTOCICS ANAESTHETICS-GENERAL Report of arrhythmias and cardiovascular collapse when halothane was given to patients taking oxytocin Uncertain possibly an 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... 

In a double-blind study in 11 healthy subjects there were several instances when alcohol 0.25 to 5 g/kg (equivalent to 1 to 3 drinks) enhanced the effects of nitrous oxide 30% in oxygen, inhaled for 35 minutes. Some effects were seen with the drug combination, which were not seen with either drug alone these included subjective effects and delayed free recall. For mention of the effect of alcohol following anaesthesia, see Anaesthetics, general -I- Alcohol , p.92. 

Note that inhalation anaesthetics potentiate neuromuscular blockers, see Anaesthetics, general + Neuromuscular blockers , p.lOl. 

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. ... 

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. 

Inhalation (IH) The administration of volatile gases and vapours, followed by drug absorption in the lungs or nasal mucosa. Examples include general anaesthetics like nitrous oxide, nicotine from the tar droplets in tobacco smoke, cannabinoids from cannabis leaf smoke and various opiates from burning opium resin. 

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

Halsey. M.J. (1989) Physicochemical properties of inhalation anaesthetics, in General Anaesthesia, (eds J.F. Nunn eta/.). Butterworth. London. 

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