Anaesthesia is from the Greek and means 'loss of sensation'. Anaesthesia allows invasive and painful procedures to be performed with little distress to the patient. Show There are three main types of anaesthesia. General anaesthesiaThe patient is sedated, using either intravenous medications or gaseous substances, and occasionally muscles paralysed, requiring control of breathing by mechanical ventilation. This can be described as central where anaesthetic drugs are administered directly in or around the spinal cord, blocking the nerves of the spinal cord (eg, epidural or spinal anaesthesia). The main benefit of this method is that ventilation is not needed (provided the block is not too high). Regional anaesthesia can also be peripheral - for example:
Local anaesthesiaIn this method the anaesthetic is applied to one site, usually topically or subcutaneously. The practice of anaesthesia is fundamental to the practice of medicine. However, anaesthesia is not without its problems. It is difficult to determine exactly the incidence of deaths directly attributable to general anaesthetics, as the cause of death is often multifactorial and study methodology varies making comparisons difficult. Estimates of the number of deaths where general anaesthesia was the direct cause have been quoted in the range from 1:10,000 operations to 1:1,700 (study in 1982 by the Association of Anaesthetists of Great Britain and Ireland). Nonetheless, in 1987 a confidential enquiry into perioperative deaths revealed that very few deaths were actually as a direct result of general anaesthesia - incidence of 1 in 185,086 (first Confidential Enquiry into Perioperative Deaths (CEPOD))[1]. Figures of anaesthetic-related morbidity are more difficult to determine. Although general anaesthesia is not without risk, it should be remembered that it allows necessary procedures to be performed in a humane way - without which the patient might otherwise die. Along these lines, if a patient is high-risk for a general anaesthetic (eg, pre-existing comorbidities) then they should still be referred for surgery like any other patient. The decision to operate and which form of anaesthesia to use should then be decisions made by the surgeon and anaesthetist. Important complications of general anaesthesia
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It is now common practice to check the teeth in the anaesthetist's pre-operative assessment. Damage to teeth is actually the most common cause of claims made against anaesthetists. The tooth most commonly affected is the upper left incisor. EmbolismEmbolism is rare during an anaesthetic but is potentially fatal. Air embolism occurs more commonly during neurosurgical procedures or pelvic operations. Prophylaxis of thromboembolism is common and begins pre-operatively with thromboembolic deterrents (TEDS) and low molecular weight heparin (LMWH). Central regional anaesthesia was first used at the end of the 18th century. It provided a method of blocking afferent and efferent nerves by injecting anaesthetic agents in either the epidural space around the spinal cord (epidural anaesthesia) or directly in the cerebrospinal fluid surrounding the spinal cord (ie in the subarachnoid space called spinal anaesthesia). All nerves are blocked including motor nerves, sensory nerves and nerves of the autonomic system. Epidural anaesthesia takes slightly longer than spinal anaesthesia to take effect and provides predominantly analgesic properties. With both, the need for muscle paralysis and ventilation is not usually required but there is a risk that a high block will impair respiration, meaning that ventilation will be necessary. Cochrane systematic reviews (such as the cited reference) have shown that regional anaesthesia is associated with reduced mortality and reduction in serious complications in comparison with general anaesthesia[5]. Important complications of regional anaesthesia
Total spinal block can occur with the injection of large amounts of anaesthetic agents into the spinal cord. It is detected by a high sensory level and rapid muscle paralysis. The block moves up the spinal cord so that respiratory embarrassment may occur, as can unconsciousness. In these situations the patient needs prompt assessment and may need to be intubated and ventilated until the spinal block wears off. Hypotension
All forms of anaesthetics are invasive to a patient and therefore consent should be obtained as for other procedures. Ideally patients should be given a leaflet regarding anaesthesia and then counselled regarding the intended benefits and the risks of anaesthesia. In a general practice setting it will be the responsibility of the clinician who administers the local anaesthesia to ensure good, non-coercive consent is obtained.
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