Chapter 22: Cancer pain assessment and management
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Regional peripheral and plexus nerve blocks and infusions
Definition
The term ‘regional anaesthesia’ refers to the loss of sensation in a region of the body produced by application of an anaesthetic agent to all the nerves supplying that region. Regional analgesia includes peripheral nerve blocks to the arm, leg or head.
Regional analgesia can be used for patients with cancer‐related pain when the oral route is failing or cannot be escalated further due to severe side‐effects. It can either be a single injection (‘single shot’) or a continuous infusion such as a continuous peripheral nerve block (CPNB). CPNB can also be delivered as an ambulatory service where patients are discharged home with the infusion.
Anatomy and physiology and related theory
Regional analgesia blocks transmission of pain impulses through a nerve or a nerve plexus by depositing an analgesic drug (usually local anaesthetic with or without an opioid) close to the nerve, cutting off sensory innervation to the region it supplies. Pain impulses are inhibited but some sensation of touch and muscle functions are intact. Regional analgesia gives relief of pain on movement.
Specific regional analgesia nerve blocks
Specific types of regional analgesia nerve blocks can be used for different types of cancer pain. Table 22.3 lists examples of different regional nerve blocks and the procedures they can be used for.
Table 22.3 Examples of regional analgesia blocks
| Type of block | Remarks |
|---|---|
| Brachial plexus block | The brachial plexus is the major nerve bundle going to the shoulder and arm.
This block can be used to manage intractable cancer pain from tumours invading the brachial plexus such as those involving the breast and chest wall |
| Coeliac plexus block | For severe pain due to pancreatic cancers. This is a neurolytic block using an injection of alcohol or phenol into the coeliac plexus – this destroys the neural pathways that cause pain. It can be performed by two approaches: percutaneous and endoscopic |
| Hypogastric plexus block | For visceral pain from advanced cervical, bladder, rectal and prostate cancer |
| Saddle block | For uncontrolled pain of the perineum, scrotum, penis or anus |
Evidence‐based approaches
Rationale
Regional analgesia approaches can be used for several reasons. The ability to provide selective analgesia with minimal adverse effects can be beneficial, particularly in older patients who may have co‐existing conditions (Macintyre and Schug [128], Parizkova and George [164], [165]). By using a nerve block or a continuous infusion of local anaesthetic, pain relief can be superior to the use of opioids alone, and the use of opioids can be minimized in the post‐operative setting, resulting in fewer adverse effects such as nausea, vomiting, sedation and pruritus (D'Arcy [44], Le Wendling and Enneking [122], Richman et al. [186]). Pain relief and functionality may also be improved.
Contraindications for regional analgesia nerve blocks
There are few contraindications for the use of regional nerve blocks but consideration must be given to the risk of bleeding and infection, particularly if the patient is on anticoagulant therapy. The risk of haematoma and developing an infection should be carefully explained along with any other risks associated with the procedure. In patients with cancer these techniques may be more technically challenging due to the loss of traditional ‘landmarks’ to guide correct placement of the needle or catheter. These landmarks can be difficult to find due to oedema (palpation of pulses and bony prominences can be difficult or impossible) and neuro‐anatomy can be distorted by tumour or scarring near the nerves to be blocked (Peat et al. [171]).
Classes of drugs used in regional analgesia and mechanism of action
In peripheral nerve blocks the most common drug used is a local anaesthetic.
Commonly used local anaesthetic agents include bupivacaine, levobupivacaine and ropivacaine. Local anaesthetics bind directly within the intracellular portion of voltage‐gated sodium channels. The degree of block produced by local anaesthetics is dependent upon how the nerve has been stimulated and on its resting membrane potential. Local anaesthetics are only able to bind to sodium channels in their charged form and when the sodium channels are open. They will cause numbness and loss of sensation and there may also be some loss of muscle function depending on the purpose of the block.
The dose of a local anaesthetic agent will also determine which nerves are blocked. Low concentrations of bupivacaine (e.g. 0.100–0.125%) preferentially block nerve impulses in the smallest diameter nerve fibres, which include the pain and temperature sensory fibres. As the larger diameter motor fibres are less likely to be blocked with concentrations of 0.100–0.125% bupivacaine, the incidence of motor weakness is reduced and the patient is able to mobilize.
In certain blocks a steroid may be combined with the local anaesthetic to reduce inflammation and pain; an example of a steroid used is methylprednisolone.
Legal and professional issues
There should be formal induction courses and regular updates for doctors, nurses, theatre and recovery staff who will be responsible for supervising patients receiving CPNBs.
Staff competency
Nursing competencies for the nurse who monitors the patient with a CPNB should include knowledge of:
- anatomy and physiology of the spinal cord and column and neurological system
- purpose of the regional nerve block for pain management
- untoward reactions to medication and management of complications.
Nursing care responsibilities include:
- observation
- any necessary procedures (e.g. reinforcing dressing)
- documentation of care.
Pre‐procedural considerations
Prior to a CPNB procedure the following areas need to be considered:
- Does the patient have capacity to make an informed choice?
- Can the patient physically sustain a suitable position while the intervention is performed?
- Does the patient have an uncorrectable coagulopathy?
- Are there any considerations for aftercare?
Post‐procedural considerations
Immediate and ongoing care
Monitoring the patient
When caring for a patient receiving regional analgesia, it is important to monitor the patient for the following:
- drug‐related side‐effects
- pain intensity
- signs of complications due to the regional analgesia procedure.
Complications
Complications can:
- be drug related
- arise from the insertion of the needle or catheter
- arise from the indwelling catheter.
