Regional Anaesthesia and Pain Management

Regional anaesthesia, also known as nerve block, is used to block the sensation in a specific part of the body during and after surgery.

A reliable method to prevent pain from becoming chronic involves using a regional anaesthetic technique to block a pain stimulus near its origin, thereby eliminating acute pain as a post-operative risk factor. Regional anaesthetic techniques can be divided into two categories; central and peripheral techniques. The central techniques include neuraxial blockade (e.g. epidural anaesthesia, and spinal anaesthesia). The peripheral techniques can be further divided into brachial plexus blocks and single nerve blocks.

The aim of acute pain management is to achieve a comfortable, mobile patient with a sedation score of less than two. Patients often experience pain in the post-operative period which, if uncontrolled, can be associated with increased morbidity. Body systems which can be compromised by inadequate pain control include the respiratory, cardiovascular, neuroendocrine, musculoskeletal and gastrointestinal systems. The psychological effects of pain should also be considered. When left untreated, pain can lead to fear and psychological distress related to the patient’s concerns regarding disability, loss of income, and underlying illness.

Local anaesthetics are widely used for the management of acute pain resulting from surgical procedures and child birth. When local anaesthetics are injected or infused into specific sites, they provide a loss of sensation to that region by reversibly blocking the transfer of peripheral nerve stimulation in that part of the body. The effect may be gained from a local anaesthetic alone, or enhanced by combination with an analgesic (e.g. ropivacaine with fentanyl). Local anaesthetics may also be administered in a continuous infusion, over several days, for effective post-operative pain control.

Long-Acting Local Anaesthetics

Bupivacaine is a long-acting agent, but has a relatively high potential for cardiotoxicity. It is used for minor and major nerve blocks, spinal anaesthesia and epidurals.

Ropivacaine is a long-acting agent that is structurally related to bupivacaine and mepivacine. It was developed as a safer alternative to bupivacaine, and is less cardiotoxic when accidentally administered intravenously. It is used for minor (e.g. field blocks and infiltrations) and major (e.g. brachial plexus) nerve blocks, spinal anaesthesia, epidurals, continuous peripheral nerve blocks (e.g. knee arthroplasty) and wound infiltration. Ropivacaine is the only local anaesthetic indicated for continuous peripheral nerve blocks.

Levobupivacaine is used for minor and major nerve blocks, spinal anaesthesia, epidurals, and wound infiltration; and is also less cardiotoxic than bupivacaine.

Short-Acting Local Anaesthetics

Lignocaine is a short-acting local anaesthetic. It has inherent potency, rapid onset, and a medium duration of action. The addition of a vasoconstrictor agent (e.g. adrenaline) greatly extends the duration of its effect.

Prilocaine has a similar clinical profile to lignocaine in terms of speed of onset and duration of effect. However, it is absorbed more slowly due to its lesser vasodilation effect. It also has less central nervous system toxicity than lignocaine.

Topical Anaesthetics

For topical anaesthesia, a local anaesthetic is applied to an area of the body’s surface in the form of a spray, cream, gel or solution (with the aim of blocking activity in the pain receptors of the superficial nerves that lie immediately below the surface). The choice of local anaesthetic depends on the region which needs to be anaesthetised (refer to Table 1).

Table 1. Forms and Uses of Topical Lignocaine.

Regional anaesthesia offers numerous advantages over conventional general anaesthesia, including faster recovery time, fewer side effects (less nausea and vomiting and fewer thromboembolic events), minimal post-operative pain and no need for an airway device during surgery, or need for an anaesthetist during minor procedures. Hospital stays can be significantly reduced and the overall costs are also reduced.

The disadvantages of regional anaesthesia include a requirement for practice and skill in order to achieve the best results. Toxicity can occur if the local anaesthetic is given intravenously or if an overdose is injected. Some blocks require up to 30 minutes, or more, to be fully effective. Post-operative pain management may not always be effective, requiring the possible use of additional analgesia. There is also a risk of nerve damage, and the area where the nerve block was administered may be sore or tender for a few days.

Various types of regional block procedures are possible to achieve blockade of different regions of the body, for example:

Central blockade:

• Spinal: suitable for caesarean section and obstetric analgesia, hernia repair, hip and knee surgery, prostate surgery and most procedures on the foot or leg, and
• Epidural: suitable for labour pain, orthopaedic surgery, caesarean section, thoracic and breast surgery, gynaecological procedures and upper and lower abdominal procedures.

Upper extremities:

• Brachial Plexus Blockade: Interscalene block, Infraclavicular block, Supraclavicular block, Axillary block
• Wrist block, and
• Digital block.

Lower extremities:

• Sciatic nerve block, and
• Femoral nerve block.

Intravenous block:

• Bier’s block.

After the block, verbal communication with the patient will often assist in identifying early signs of local anaesthetic toxicity (e.g. speech disturbances). Cardiovascular signs should be monitored. Rapid tachycardia will be detectable immediately if a solution containing adrenaline is accidentally injected intravenously.

Regional anaesthesia should only ever be conducted in an environment which is fully equipped and adequately staffed to provide safe general anaesthesia, should the need arise.