Propofol Inhalational anaesthetics

Operationally, anaesthetics can be classified as inhalational or intravenous. The most used compounds of this last group are thiopental, propofol and ketamine recently, new synthetic opioids related to phenylpiperidines (phentanyl and its congeners, sufentanil, alfentanil, remifentanil) are also used. 

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. 

Intravenous anaesthetics are used to induce general anaesthesia, followed by an inhalation anaesthetic for maintenance, and for short surgical procedures. Propofol is commonly used for both induction and maintenance anaesthesia. 

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-... 

An isolated report describes convulsions associated with the use of propofol with topical cocaine. Cocaine abuse may increase the risk of cardiovascular complications during inhalational anaesthesia. Abstinence from cocaine or the avoidance of anaesthetics with sympathomimetic properties has been suggested. 

The dosage of propofol may need to be reduced after the use of bupivacaine or lidocaine (e.g. during regional anaesthetic techniques). Similarly, epidural lidocaine reduces sevoflurane requirements, and is likely to have the same effect on other inhalational anaesthetics. 

Inhalation anaesthetics may impair the efficacy of anticholinesterases in reversing neuromuscular blockade. Propofol does not affect the reversal of rocuronium block by neostigmine. Physostigmine pre-treatment increased propofol requirements by 20% in one study. 

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 inhalational anaesthetics increase the effects of the neuromuscular blockers to differing extents, but nitrous oxide appears not to interact significantly. Ketamine has been reported to potentiate the effects of atracurium. Propofol does not appear to interact with mivacurium or vecuronium. Xenon is reported not to interact with mivacurium or rocuronium, and has less effect than sevoflurane on vecuronium neuromuscular blockade. Bradycardia has been seen in patients given vecuronium with eto-midate or thiopental. Propofol can cause serious bradycardia if it is given with suxamethonium (succinylcholine) without adequate antimuscarinic premedication, and asystole has been seen when fentanyl, propofol and suxamethonium were given sequentially. 

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