Regional anaesthesia (or regional anesthesia) is anaesthesia affecting only a large part of the body, such as a limb or the lower half of the body. Regional anaesthetic techniques can be divided into central and peripheral techniques. The central techniques include so called neuraxial blocks (epidural anaesthesia, spinal anaesthesia). The peripheral techniques can be further divided into plexus blocks such as brachial plexus blocks, and single nerve blocks. Regional anaesthesia may be performed as a single shot or with a continuous catheter through which medication is given over a prolonged period of time, e.g. continuous peripheral nerve block. Regional anaesthesia can be provided by injecting local anaesthetics directly into the veins of an arm (provided the venous flow is impeded by a tourniquet.) This is called intravenous regional techniques (Bier block).
This differs from Local anaesthesia, which, in a strict sense, is anaesthesia of a small part of the body such as a tooth or an area of skin, and Conduction anaesthesia is a comprehensive term which encompasses a great variety of local and regional anaesthetic techniques.
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Regional anaesthesia may provide anaesthesia (absence of feeling, including pain) to allow a surgical operation, or provide post-operative pain relief. Various brachial plexus blocks exist for shoulder and arm procedures. Methods similar to routine regional anaesthetic techniques are also often used for treating chronic pain.
In labour and childbirth, epidural or combined spinal epidurals provide effective pain relief. Regional anaesthesia is now more common than general anaesthesia for Caesarean section procedures.
Nerve blocks are widely used in veterinary medicine to diagnose lameness. A very common application is the diagnosis of navicular disease in horses.
Unlike general anaesthesia, patients may remain awake during the procedure, resulting in reduced side-effects and enabling the surgeon to converse with the patient during the procedure if required. However, many patients prefer to receive sedation either during the block, the procedure, or both.
There is a spectrum of complexity between simple local anaesthetic infiltration and major regional blocks, such as the 'central neuraxial blocks' (spinal and epidural), with nerve blocks lying in the middle. Nerve blocks affecting major peripheral nerves such as the femoral nerve and sciatic nerve are also sometimes viewed as regional anaesthetic techniques.
Unlike a minor local anaesthetic infiltration to allow a wound to be sutured, or a skin lesion to be excised, regional anaesthesia may involve large doses of local anaesthetic, or administration of the local anaesthetic very close to, or directly into the central nervous system. Therefore there is a risk of complications from local anaesthetic toxicity (such as seizures and cardiac arrest) and for a syndrome similar to spinal shock.
Most regional anaesthetic techniques, even in expert hands, have a failure rate of 1–10%. Therefore, general anaesthesia may become necessary even when a procedure was initially planned to be conducted under a regional technique.
For these reasons, regional anaesthesia is only ever conducted in an environment that is fully equipped and staffed to provide safe general anaesthesia should this be needed.
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