Anaesthesia/anaesthetic agents

Using Volatile Anaesthetic Agents. Dr. P. Fenton, Update in Anaesthesia, Practical Procedures, Issue 5,1995, http //www.nda.ox.ac.uk/wfsa/html/u05/u05 007.htm... 

A clinically useful action of a2-agonists is their ability to reduce the requirements for other anaesthetic agents during anaesthesia. In control mice, non-sedative doses of dexmedetomidine reduced the concentrations of the volatile anaesthetic, halothane, to induce anaesthesia by 30% (Lakhlani et al. 1997). This anaesthetic-sparing effect of a2-agonists was completely abolished in a2A-D79N mice. 

It is a new intravenous anaesthetic agent with poor analgesic property. It has a briefer duration of action than thiopentone. It produces little cardiovascular and respiratory depression. A single intravenous dose produces loss of consciousness within 10 seconds and a state of anaesthesia. 

It is indicated for preoperative sedation, conscious sedation prior to short diagnostic or endoscopic procedures, induction of general anaesthesia prior to administration of other anaesthetic agents. 

It is indicated as a narcotic analgesic supplement in general or regional anaesthesia, as an anaesthetic agent with oxygen and skeletal relaxant in selected high risk patients (e.g. open heart surgery). 

The ideal intravenous anaesthetic agent Mechanism(s) of intravenous anaesthesia Pharmacokinetics and metabolism Rapidly acting intravenous anaesthetics Non-barbiturate intravenous anaesthetics Slower-acting intravenous anaesthetics Other drugs INTRODUCTION... 

INTRAVENOUS ANAESTHETICS (e.g. thiopentone sodium, propofol) BETA-BLOCKERS Risk of severe hypotensive episodes during induction of anaesthesia (including patients taking timolol eye drops) Most intravenous anaesthetic agents are myocardial depressants and vasodilators, and additive 1 BP may occur Monitor BP closely, especially during induction of anaesthesia... 

Uses. Nitrous oxide is used to maintain surgical anaesthesia in combination with other anaesthetic agents, e.g., isoflurane or propofol, and, if required, muscle relaxants. Entonox provides analgesia for obstetric practice, for emergency management of injuries, and during postoperative physiotherapy. 

Desflurane has the lowest blood/gas partition coefficient of any inhaled anaesthetic agent and thus gives particularly rapid onset and offset of effect. As it undergoes negligible metabolism (0.03%), any release of free inorganic fluoride is minimised this characteristic favours its use for prolonged anaesthesia. Desflurane is extremely volatile and caimot be administered with conventional vaporisers. It has a very pimgent odour and causes airway irritation to an extent that limits its rate of induction of anaesthesia. 

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). 

Columb M O 2001 Local anaesthetic agents. Anaesthesia and Intensive Care Medicine 2 288-291... 

Gultekin S, Yilmaz N, Ceyhan A, Karamustafa I, Kilic R, Unal N. The effect of different anaesthetic agents in hearing loss following spinal anaesthesia. Eur J Anaesthesiol 1998 15(l) 61-3. 

It is a basal anaesthetic agent of choice which is administered through rectum in the form of its solution. The main advantage of such an anaesthesia being its pleasant induction amalgamated with lack of irritating vapours. 

A good deal of faetual information has been accumulated in connection with physical properties together with bioehemical and physiological processes of anaesthetic agents, but unfortunately not a single theory proved and substantiated by experimental facts of anaesthesia is known. 

An anaesthetic agent which has become virtually obsolete because it is explosive or highly inflammable in the concentration needed to cause anaesthesia. 

In fact, N2O is usually employed alone as an anaesthetic agent during some special localized dental procedures only. However, most frequently N2O is utilized with other volatile anaesthetics to cause a sufficient desirable depth of anaesthesia essentially required for various surgical procedures . 

It is a barbiturate of choice for rapid action, administered intravenously, for causing anaesthesia, supplementing general anaesthetic agents, short surgical trauma and induction of hypnosis. 

Uses cinchocaine is used as an anaesthetic agent for spinal anaesthesia a component in rectal medications used in inflammation of the anus and for the symptomatic treatment of hemorrhoids and fissures in the anus local anesthetic agent Cross lidocaine. PA A... 

A 77-year-old female underwent an elective right hemicolectomy for cancer. Preoperative investigations were unremarkable and previous medical history included hypertension and a previous general anaesthesia for uterine fibroid surgery (anaesthetic agent unknown). She had an uneventful general anaesthetic with thoracic epidural... 

Foetal depression during spinal and epidural obstetric anaesthesia occurs secondary to maternal hypotension or as a result of placental transfer of the local anaesthetic agent (8, 10 -, 13 ). In this respect, bupivacaine was found to have a low foeto-maternal drug concentration ratio (16 -). When caudal anaesthesia is used, direct injection of the local anaesthetic drug into the foetus is possible (13, Other causes... 

There have been many attempts to produce a unified theory detailing the mechanism of action of inhalation anaesthetics but no single theory has been accepted. Early theories on the mechanism of action of inhalation anaesthetics can by summarised by means of the Meyer-Overton theory, which indicated that the potency of anaesthetic action was related to the lipophilicity of an anaesthetic compound. The Meyer-Overton theory suggested that lipids within the brain could be dissolved by anaesthetic agents, thereby interfering with brain cell activity, leading to anaesthesia. 

Intravenous anaesthetics are mainly used for rapid induction of anaesthesia, which is then maintained by an inhalational agent. They also serve to reduce the amount of maintenance anaesthetics. 

Pre-anaesthetic medication These agents reduce the salivary and respiratory secretion and are administered half an hour before general anaesthesia. They also prevent laryngospasm. Atropine is given in combination with morphine as a preanaesthetic medication to antagonize the central depressant action of morphine on respiration. 

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