General anaesthesia is a drug-induced state of unconciousness that is achieved by the anaesthetist through the administration of either gases or drugs injected into a vein. The state of unconciousness is maintained throughout the operation. The anaesthetist carefully and constantly monitors physiological variables according to the Australia and New Zealand College of Anaesthetists guidelines.
Epidurals and spinal anaesthesia are forms of local anaesthesia that numb a large part of the body and are called major regional techniques. Epidurals and spinals require the placement of a needle into the back in order to administer the local anaesthetic to the correct place to achieve the desired effect. Epidurals in particular can also be used as a method of pain relief.
Awareness under general anaesthesia is an uncommon, but potentially devastating complication. Surgical procedures under general anaesthesia which have traditionally been associated with a higher risk of awareness include cardiac, trauma and obstetric surgery, because patients may be unstable and a deep level of unconciousness may be unsafe.
Anaesthetists are very concerned to prevent awareness and continually seek ways to reduce the risk. Recently, the BIS monitor for awareness has become available in Australia, but it is not yet considered mandatory by the Australian and New Zealand College of Anaesthetists. The BIS monitor is connected to the patient via a metallic strip placed on the forehead which analyses brain activity and provides a numerical value between 0 and 99, which the anaesthetist is trained to interpret.
It is important to know that when using other kinds of anesthesia, such as local, sedation or regional anesthesia, it is expected that patients will have some recollection of the procedure.
For further information we recommend reading information at "Anesthesia awareness during surgery" from the America Society of Anesthesiologists.
The amount and type of analgesia required varies greatly depending on individual patient needs and the surgical procedure undertaken.
A variety of different types of drugs can be used, alone or in combination. These include drugs such as opioid analgesics, NSAIDs (anti-inflammatories), local anaesthetics, regional blockade (epidurals and spinals) and some novel agents (for example, ketamine).