Chapter 22: Cancer pain assessment and management
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Neuraxial (spinal) blocks: epidural and intrathecal analgesia
Definition
The term ‘spinal analgesia’ refers to both the epidural and intrathecal route (Day [48], Sloan [207]). The spinal cord rests in a medium of cerebrospinal fluid (CSF), which is contained by the protective membrane of the dura mater. Analgesics applied outside the dura mater are termed ‘epidural analgesia’, and medications given into the CSF are termed ‘intrathecal analgesia’ (Sloan [207]).
Anatomy and physiology
The spinal cord (Figure 22.9 and Figure 22.10) is covered by the meninges; the pia mater is closely applied to the cord and the arachnoid mater lies closely with the outer, tough covering of the dura mater (Behar et al. [10]). The epidural space lies outside all three membranes, encasing the spinal cord between the spinal dura and ligamentum flavum. The contents of the epidural space include a rich venous plexus, spinal arterioles, lymphatics and extradural fat.
Figure 22.9 Gross anatomy of the spinal cord. (a) Posterior view and transverse section through spinal cord. (b) Transverse section of the spinal cord within a cervical vertebra. Source: Tortora and Derrickson ([214]). Reproduced with permission from John Wiley & Sons.
Figure 22.10 Branches of a typical spinal nerve, shown in cross‐section through the thoracic portion of the spinal cord: transverse section. Source: Tortora and Derrickson ([214]). Reproduced with permission from John Wiley & Sons.
The intrathecal space (also termed the subarachnoid space) lies between the arachnoid mater and pia mater and contains the CSF (Chapman and Day [36]).
There are 31 pairs of spinal nerves of varying size which pass out through the intervertebral foramina between each vertebra (Chapman and Day [36]). There are two main groups of nerve fibres.
- Myelinated: myelin is a thin, fatty sheath that protects and insulates the nerve fibres and prevents impulses from being transmitted to adjacent fibres.
- Unmyelinated: delicate fibres, more susceptible to hypoxia and toxins than myelinated fibres.
The spinal nerves are composed of a posterior and anterior root, which join to form the nerve.
Specific skin surface areas are supplied/innervated by each of the spinal nerves. These skin areas are known as dermatomes (Figure 22.11).
Figure 22.11 Distribution of dermatomes. Source: Tortora and Derrickson ([214]). Reproduced with permission from John Wiley & Sons.
Evidence‐based approaches
Epidural analgesia is the administration of analgesics (local anaesthetics and opioids with or without adjuvants such as corticosteroids and clonidine) into the epidural space via an indwelling catheter (Macintyre et al. [129]). This technique enables analgesics to be injected close to the spinal cord and spinal nerves where they exert a powerful analgesic effect. It is one of the most effective techniques available for the management of acute pain (Macintyre and Schug [128], Wheatley et al. [232]).
Intrathecal (spinal) analgesia is the administration of analgesic drugs directly into the CSF in the intrathecal space (Gelinas and Arbour [84]). The intrathecal space is also referred to as the subarachnoid space. Analgesic drugs given via this route are 10 times as potent as those given into the epidural space so doses given are much smaller.
Spinal blocks are forms of anaesthesia that temporarily interrupt sensation from the chest, abdomen and legs by injection of local anaesthetic medication into the vertebral canal, which contains the spinal cord, spinal nerves and CSF. They are typically given as a single injection which will last for 2–6 hours depending on the type and volume of local anaesthetic given. If an opioid is given, such as morphine, this can produce analgesia lasting 12 hours (Macintyre et al. [129]).
In chronic pain, this method (intrathecal drug delivery – ITDD) can be utilized for the delivery of continuous infusions of analgesia in patients with:
- chronic non‐cancer pain unresponsive to other analgesics or when analgesia leads to intolerable side‐effects
- cancer pain that is uncontrolled with appropriate systemic opioids or when analgesia leads to intolerable side‐effects
- spasticity.
Several different types of drug delivery systems are available.
- Percutaneous catheters (tunnelled or not) used with an external pump, which are easy to place and may be appropriate if the patient has limited life expectancy.
- Fully implantable ITDD systems with an injection port to enable top‐up of the analgesic medication, and a programmable function to allow for adjustments in dose and rate settings from an external device.
Local anaesthetics, opioids and other drugs such as clonidine can be given via this route.
The use of drugs via either the epidural or the intrathecal route can cause both a loss of sensation (anaesthesia) and a loss of pain (analgesia).
Rationale
There are two main advantages to using epidural or intrathecal analgesia.
- It has the potential to provide effective dynamic pain relief for many patients (D'Arcy [44]).
- The combination of local anaesthetic agents with opioids has a synergistic action that allows the concentration of each drug to be reduced. This limits the unwanted side‐effects of each drug (Hurley et al. [104]).
Indications
- Provision of post‐operative analgesia in patients undergoing palliative surgery for cancer. Epidural analgesia has been used since the late 1940s as a method of controlling post‐operative pain (Chapman and Day [36]).
- Provision of analgesia for pain resulting from cancer invasion of local structures such as pathological fractures.
- Management of intractable pain in patients with cancer who experience the following:
- To relieve muscle spasm and pain resulting from lumbar cord pressure due to disc protrusion or local oedema and inflammation.
For cancer patients who do not obtain pain relief from treatment with opioids administered orally, rectally, by injection or continuous infusion, there is evidence that both epidural and intrathecal analgesia can be effective (Ballantyne and Carwood [6]). Intrathecal analgesia can either be delivered via an external infusion pump or can be part of a fully implantable reservoir system (Dickson [54]).
Contraindications
These may be absolute or relative.
Absolute
- Patients with coagulation defects, which may result in haematoma formation and spinal cord compression, for example iatrogenic (anticoagulated patient) or congenital (haemophiliacs), or thrombocytopenia due to disease or as the result of anticancer treatment (Horlocker et al. [102]).
- Local sepsis at the site of proposed epidural or intrathecal injection; the result might be meningitis or epidural abscess formation.
- Proven allergy to the intended drug.
- Unstable spinal fracture.
- Patient refusal to consent to the procedure.
Relative
- Unstable cardiovascular system.
- Spinal deformity.
- Raised intracranial pressure (risk of herniation if a dural tap occurs).
- Certain neurological conditions, for example multiple sclerosis, where an epidural may result in an exacerbation of the disease (Hall [88]).
- Unavailability of staff trained in the management of epidural or intrathecal analgesia (Macintyre and Schug [128]). Hall ([88]) notes that staff managing patients with epidural or intrathecal analgesia should have undertaken a period of formal training to care for patients safely and competently.
Methods of administration
Continuous infusion
Continuous infusions of intrathecal analgesic drugs have been shown to be effective in the management of chronic intractable cancer pain (Ballantyne and Carwood [6]).
Continuous infusions can be given by either a syringe pump or a designated infusion pump system. The effectiveness of this method of administering drugs is dependent on a number of factors including the combination of drugs used, the position of the catheter at a level appropriate to the site of pain (Weetman and Allison [231]) and the volume of the local anaesthetic agent infused (Chapman and Day [36], Hall [88]).
Patient‐controlled epidural analgesia
The use of patient‐controlled epidural analgesia (PCEA) has gained popularity in recent years because it enables patients to control their analgesia. For patients with persistent pain, PCEA is used more effectively in combination with a low‐dose background infusion (Wheatley et al. [232]). This ensures a baseline level of analgesia that can then be supplemented by the patient when required.
Bolus injections
Bolus injections of local anaesthetic agents and/or opioids are used infrequently but can be given to top up and re‐establish analgesia if pain is uncontrolled. This procedure is usually performed by the doctor or bolus doses of low‐dose concentrations may be given by nursing staff as part of an advanced practice role, according to local policy. This should follow an agreed period of education and supervised practice, which must be documented.
This is a clean aseptic procedure. Most epidural/intrathecal infusion pumps allow a bolus dose to be programmed and delivered from the pump. This prevents the administration line and bacterial filter being accessed and thus minimizes the risk of introducing infection. Intrathecal bolus doses are usually only given by the doctor.
Classes of epidural and intrathecal drugs and mechanism of action
Three classes of drugs are commonly used to provide epidural or intrathecal analgesia: opioids, local anaesthetic agents and adjuvant drugs such as corticosteroids and clonidine.
Opioids
A number of different opioids have been used for epidural and intrathecal analgesia; two of the most commonly used are diamorphine and fentanyl (Bannon et al. [7], Cook et al. [42], Romer and Russell [191]). When either of these opioids is injected into the epidural space, part of the opioid dose:
- crosses the dura and arachnoid membrane and enters the CSF. From the CSF, a proportion of the drug is taken up into the spinal cord and reaches the opioid receptors in the spinal cord. Once bound to the opioid receptors, this results in blocking of pain impulses
- enters the systemic circulation and contributes to analgesia
- binds to the epidural fat and does not contribute to analgesia.
When opioids are placed directly into the CSF in the intrathecal space, they attach directly to the opioid spinal cord receptor sites (Urdan et al. [223]).
Fentanyl differs from diamorphine in that it is more lipid soluble. This means that it passes more easily into the CSF, gaining faster access to the opioid receptors and having a more rapid onset of action. Fentanyl also has a shorter duration of action (1–4 hours) compared with diamorphine (6–12 hours) (Macintyre and Schug [128]).
Local anaesthetic drugs
Commonly used local anaesthetic agents include bupivacaine, levobupivacaine and ropivacaine. They inhibit pain transmission by blocking sodium ion channels that are involved in the propagation of electrical impulses along the spinal nerves. In epidural analgesia, these drugs gain access to the nerve roots and the spinal cord by crossing the dura and subarachnoid membranes (Macintyre and Schug [128]).
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 leg weakness is reduced and the patient is able to mobilize.
Adjuvant drugs
Corticosteroids
Corticosteroid ‘single shot’ injections are often used to relieve back pain caused by degenerative disc disease and radicular pain from inflammatory irritation of nerve roots from a ‘trapped nerve’ or a disc prolapse (Farquhar‐Smith [71]).
Clonidine
Adrenergic alpha‐2 receptors are found in the spinal cord and are thought to be activated by descending inhibitory pathways and release of endogenous agonists. Clonidine is a mixed adrenergic alpha‐2 agonist and is thought to be active at the spinal level (Farquhar‐Smith [71]).
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 continuous epidural analgesia (Royal College of Anaesthetists [196]). The acute pain service or a clearly designated consultant anaesthetist from the anaesthesia department will be responsible for the immediate supervision of patients receiving local anaesthetic infusions. The National Patient Safety Agency (NPSA [151]) recommends that in addition to routine training and regular updates, additional training occurs when changes are made to protocols, medicine products or medical devices. Routine training should include a programme to help healthcare staff gain competence and confidence in using infusion devices employed to deliver epidural/intrathecal analgesia, a theoretical understanding of how the drugs work, and the monitoring required to detect both drug‐ and procedure‐related side‐effects and complications (Table 22.4).
Table 22.4 Example of competency role development profile for epidural analgesia for pain. Intended learning outcomes and elements of practitioner competency
| Knowledge and understanding | Skills |
|---|---|
You are expected to possess knowledge and understanding of the following.
| You are expected to possess the following skills.
|
There have been reported fatal cases where epidural medicines have been administered by the intravenous route and intravenous medicines have been administered by the spinal route. In response to this, the NPSA ([152]) issued a Patient Safety Alert recommending that all epidural, spinal (intrathecal) and regional anaesthesia infusions and bolus doses should be given with devices with connectors that will not also connect with intravenous equipment – so‐called ‘safer connectors’. Non‐Luer connectors for devices used for epidural, spinal (intrathecal) procedures and regional blocks have now been introduced to avoid the accidental, but potentially fatal, connection of an intravenous infusion or injection. The new international standard (ISO 80369 [109]) for these connectors is now available and includes a dedicated connector for these devices known as NRFit™ (ISO 80369‐6 [110]) that is not compatible with Luer connectors.
Pre‐procedural considerations
Equipment
Epidural or intrathecal catheters are inserted using:
- a Tuohy needle (a bevelled curved‐tip needle to reduce the risk of accidental dural puncture, with 1 cm length markings, either 16 G or 18 G)
- an epidural/intrathecal catheter (a relatively stiff catheter made of polyamide, length 1000 mm with clear blue markings completely embedded in the catheter material)
- a bacterial filter (filters provide an additional degree of safety and control to prevent bacterial infections. Minimal dead space enables accurate dosing. A high‐pressure resistance up to 7 bar enhances safety during manual injection)
- connector (to ensure safe catheter fixation)
- loss of resistance device (to aid clear identification of the epidural space).
The equipment often comes in prepared sterile disposable epidural trays or packs (Parizkova and George [164], [165]).
Dressings
The dressing over the epidural/intrathecal exit site needs to fulfil the following three functions:
- to help secure the epidural/intrathecal catheter
- to minimize the risk of infection
- to allow observation of the site without disturbing the dressing.
A transparent moisture‐responsive occlusive dressing fulfils these functions. The dressing needs to be waterproof, adhesive and breathable, so that it allows exchange of oxygen and moisture while protecting the skin from outside contamination. The epidural/intrathecal site should be inspected daily and the dressing changed at least once weekly or more frequently if there is any serous discharge from the site (see Procedure guideline 22.3: Epidural/intrathecal exit site dressing change).
Pharmacological support
Combination of drugs used
Epidural or intrathecal infusions of local anaesthetic and opioid combinations are commonly used in the UK (Baker et al. [5], Wheatley et al. [232]). The rationale behind their combined use is based on the observation that better analgesia is achieved with lower doses of each drug, therefore minimizing drug‐related side‐effects produced by higher concentrations (Curatolo et al. [43], Fotiadis et al. [77]). Although the solutions used will vary with the clinical situation, combinations of fentanyl and a local anaesthetic such as levobupivacaine are often used. The use of premixed bags is recommended to minimize medication errors involving the epidural/intrathecal route (NPSA [151]).
Specific patient preparation
Patients undergoing epidural/intrathecal analgesia should always have a venous access device in situ before the procedure. This is because, although rare, a reaction to the opioid or local anaesthetic solution (e.g. respiratory depression or sympathetic blockade) may require immediate access to the venous system. The procedure should be performed in a clinical area with access to full resuscitation equipment.
Patient information and consent prior to using epidural/intrathecal analgesia for intractable chronic or cancer pain
The following issues should be addressed with the patient, family and primary healthcare team prior to using epidural/intrathecal analgesia for intractable chronic or cancer pain.
- Drug‐related side‐effects. The concentration of analgesics needed to provide sufficient analgesia for patients with chronic cancer pain is often higher than the concentrations used post‐operatively. As a result, drug‐related side‐effects such as motor weakness and urinary retention can occur. Some patients find these side‐effects unacceptable and may prefer to avoid epidural/intrathecal analgesia altogether. Therefore, a discussion must take place with the patient and family to ensure that they are aware of these potential side‐effects and are willing to continue with epidural/intrathecal analgesia (Wallace [230]).
- Increased time in hospital. The patient should also be informed that they will need to spend a period of time in hospital following insertion of the catheter, to allow for dose adjustment and ensure that side‐effects are minimized and optimum pain management achieved.
Position of epidural or intrathecal catheter
Local anaesthetic drugs block nerve fibres at spinal segments adjacent to their site of administration. To ensure the local anaesthetic agent spreads to the dermatomes or nerves supplying the area of pain (e.g. the surgical site or the pain location caused by a tumour), the tip of the spinal catheter should be placed within the mid‐dermatomal distribution of the pain site (Table 22.5). This achieves optimal analgesia using the least amount of drugs. If the catheter is placed below the dermatomes supplying the pain site then analgesia is likely to be inadequate (Macintyre and Schug [128]).
Table 22.5 Optimal catheter location for different anatomical sites
| Anatomical site | Catheter location |
|---|---|
| Thoracic | T6–T9 |
| Upper abdominal | T7–T10 |
| Lower abdominal | T9–L1 |
| Hip/knee | L1–L4 |
Procedure guideline 22.2
Epidural/intrathecal sensory blockade: assessment
Procedure guideline 22.3
Epidural/intrathecal exit site dressing change
Procedure guideline 22.4
Epidural/intrathecal catheter removal
| Problem | Cause | Prevention | Suggested action |
|---|---|---|---|
| Headache. | Dural puncture. | Expertise of practitioner inserting the epidural. | Bedrest: headache will be less severe if patient lies flat. Replacement fluids either intravenously or orally to encourage formation of CSF. Administer analgesics for headache. If headache does not settle, contact the anaesthetic team who may consider an epidural blood patch to seal the puncture (Gaiser [81]). |
Sedation and respiratory depression (opioid toxicity).
Circumoral tingling and numbness, twitching, convulsions and apnoea (local anaesthetic toxicity). | If catheter migrates into a blood vessel, signs of opioid or local anaesthetic toxicity can occur. | Expertise of practitioner inserting the epidural.
Careful monitoring of the patient to detect early symptoms. | Stop epidural infusion.
Contact pain/anaesthetic team or summon emergency assistance. Treat the patient for complications of opioid or local anaesthetic overdose (Chapman and Day [36]). |
| Apnoea, profound hypotension and unconsciousness. | If an epidural catheter migrates from the epidural space into the intrathecal space to the CSF, the analgesic solution may reach as high as the cranial subarachnoid space. If this occurs the respiratory muscles are paralysed together with the cranial nerves, resulting in apnoea, profound hypotension and unconsciousness. This is because intrathecal doses are calculated as one‐tenth of the epidural dose and migration from the epidural space to the intrathecal space leads to a drug overdose. | Expertise of practitioner inserting the epidural.
Careful monitoring of the patient to detect early symptoms. | Stop epidural infusion.
Summon emergency assistance.
Prepare emergency equipment to support respiration and ventilate lungs.
Prepare emergency drugs and intravenous fluids and administer as directed.
Above actions to be discussed with medical team and to be undertaken if symptoms are thought to be acute and due to epidural/ intrathecal infusion rather than deterioration in condition due to underlying disease. |
| Back pain and tenderness and nerve root pain with sensory and motor weakness. | Epidural haematoma. | Assessment of coagulation status before insertion and removal of the epidural/intrathecal catheter. | Urgent neurological assessment.
Computed tomography (CT) or magnetic resonance imaging (MRI) scan may be performed to diagnose if there is nerve or spinal cord compression. If a haematoma is diagnosed patient may be referred for urgent surgery (Chapman and Day [36]).
To avoid haematoma on removal of epidural in patients treated with prophylactic anticoagulants, see guidelines for timing of removal. |
Back pain and tenderness.
May have redness and purulent discharge from catheter exit site.
May also develop nerve root signs with neuropathic pain and sensory/motor weakness. | Epidural abscess. | Maintain aseptic technique when accessing the epidural/intrathecal analgesic system.
Monitor temperature regularly and check insertion site for evidence of infection. | Treat with antibiotics.
CT or MRI scan may be performed and patient may be referred for urgent neurosurgery to prevent paraplegia dependent on their current prognosis.
Discussion with all of team, patient and family on risks/benefits of stopping and removing epidural/intrathecal catheter. Infection does not always require removal of the catheter (O'Neill [160]). |
| Headaches, fever, neck stiffness, photophobia. | Meningitis. | Maintain aseptic technique when accessing the epidural/intrathecal analgesic system.
Monitor temperature regularly. | Assist anaesthetist/doctor to obtain CSF sample for microbiology analysis. Initiate antibiotic therapy as per hospital policy.
Non‐pharmacological measures for symptom management, for example dim lights.
If the infection does not respond to antibiotics it may be necessary to remove the catheter and convert back to systemic analgesia until meningitis has resolved (Mercadante [146]). |
| Pain, paraesthesia, numbness in lower extremities that may progress to paresis. | Intrathecal catheter granuloma (an inflammatory mass that forms around the catheter tip). | In long‐term therapy intrathecal may be preferable to epidural to minimize the development of a granuloma due to the presence of the CSF. | MRI scan to diagnose the problem. Stop infusion (granulomas may resolve on their own once the infusion is stopped) (Du Pen [59]). |
Post‐procedural considerations
Immediate care
Volume of infusion
The medication ‘spread’ within the epidural space is determined by the site of the epidural catheter, the patient's age and the volume of the drug being infused (Rockford and DeRuyter [190]). It is therefore important to maintain the hourly infusion rate at a volume that keeps the appropriate nerves blocked.
Effectiveness of blockade
The spinal nerves supply specific areas of skin known as dermatomes (see Figure 22.11). Sensitivity to changes in temperature (such as the cold of ice) along the sensory dermatome can be used to assess the level of epidural/intrathecal block (see Procedure guideline 22.2: Epidural/intrathecal sensory blockade: assessment). This level should be checked to ensure that the epidural/intrathecal block is providing pain relief by covering the area of the site of pain, but is also necessary to maintain safety during the administration of epidural/intrathecal infusions. If the sensory block is too high (above T4) then there is an increased risk of respiratory and cardiac symptoms as a result of the local anaesthetic effects on nerves at this level, and if it is too dense it will cause unnecessary motor blockade.
Ongoing care
When caring for a patient receiving epidural or intrathecal analgesia, it is important to monitor the patient for the following:
Drug‐related side‐effects
There are a number of drug‐related side‐effects associated with epidural/intrathecal opioids and local anaesthetic agents.
Opioids
- Respiratory depression. This is due to the action of opioids on the respiratory centre. Potential respiratory depression may occur at two different time intervals.
- Early: usually within 2 hours of the opioid injection. This may occur if high blood levels of the opioid follow absorption from the epidural space into the systemic circulation (Macintyre and Schug [128]).
- Late: this may not be seen for 6–12 hours after an opioid is given. It results from rostral migration of the drug in the CSF to the brainstem and respiratory centre (Macintyre and Schug [128]). This is less likely to occur with lipid‐soluble opioids such as fentanyl.
- Patients referred for epidural/intrathecal infusions for intractable pain are not opioid naïve and have often been taking adjuvant medications that can include sedation.
- Sedation. Although there may be many different causes of sedation, epidural/intrathecal opioids can cause sedation owing to their effect on the CNS. Opioid‐induced sedation is often an early warning sign of respiratory depression.
- Nausea and vomiting. Nausea and vomiting is caused by the action of opioids on the vomiting centre in the brainstem and stimulation of the chemoreceptor trigger zone in the fourth ventricle of the brain.
- Pruritus. Although the exact mechanism is unknown, pruritus is presumed to be centrally mediated via an itch centre in the medulla and as a consequence of disinhibition of itch neurones in the dorsal horn of the spinal cord (Macintyre and Schug [128]).
- Urinary retention. This is due to opioid inhibition of the micturition reflex which is evoked by increases in bladder volume.
Local anaesthetic agents
- Hypotension. This can be caused by two mechanisms. First, local anaesthetic agents can spread outside the epidural/intrathecal space, blocking the sympathetic nerves. This results in peripheral vasodilation and hypotension. It is most likely to occur if a bolus dose of local anaesthetic agent (e.g. 10 mL of 0.25% bupivacaine) is given to improve pain control (Macintyre and Schug [128]). Second, if the local anaesthetic agent spreads above the T4 dermatome (nipple line), the cardio‐accelerator nerves may become blocked, leading to bradycardia and hypotension (Macintyre and Schug [128]).
- Motor blockade. This will depend on the concentration and total dose of local anaesthetic agent used and the position of the epidural/intrathecal catheter (Hall [88]). Motor blockade occurs when the local anaesthetic agent blocks the larger diameter motor nerves. Leg weakness will occur if the motor nerves supplying the legs are blocked.
- Urinary retention. As with epidural/intrathecal opioids, blockade of the nerves supplying the bladder sphincter can cause urinary retention.
Routine monitoring of the patient for these side‐effects must be carried out to facilitate early management. The patient's pulse, blood pressure, respiratory rate and peripheral tissue oxygenation and temperature should be recorded regularly and then according to local policy and as the patient's condition dictates (O'Neill [160]).
For guidance on managing the side‐effects associated with epidural/intrathecal opioids and local anaesthetic agents, see Table 22.7.
Table 22.7 Epidural/intrathecal infusions of local anaesthetic agents and opioids: management of side‐effects
| Problem | Cause | Suggested action |
|---|---|---|
| Respiratory depression | Increasing age
Elderly patients are more susceptible to the side‐effects of opioids due to age‐related alterations in the distribution, metabolism and excretion of drugs | If respiratory rate falls to 8 breaths a minute or below:
|
Concurrent use of systemic opioids or sedatives
Patients receiving opioids by epidural/intrathecal infusion should not be given opioids by any other route unless given in the palliative care setting for breakthrough pain |
| |
Sedation:
Mild: patient drowsy but easy to rouse
Severe: patient difficult to rouse | See Respiratory depression |
|
| Hypotension | Patients with hypovolaemia
Patients with a high thoracic epidural in whom the concentration of local anaesthetic agent and volume of infusion cause blockade of the cardio‐accelerator nerves | If blood pressure falls suddenly:
|
| Motor blockade | More likely to occur when higher concentrations of local anaesthetic agents are given by continuous infusion
If a high concentration of a local anaesthetic agent is administered via a low lumbar epidural/intrathecal catheter then the lumbar motor nerves are likely to be blocked, causing leg weakness | Do not attempt to mobilize patient if leg weakness is evident
Contact pain or anaesthetic team for advice: reducing the concentration of the local anaesthetic agent or the rate of the epidural/intrathecal infusion may help to resolve this problem (Pasero and McCaffrey [169]) |
| Nausea and vomiting | Previous episodes of nausea and vomiting with opioids
Exacerbated by low blood pressure | Regular administration of antiemetics
Treat other causes, for example low blood pressure
Consider use of non‐pharmacological methods (e.g. stimulation of the P6 acupressure point) |
| Pruritus (usually more marked over the face, chest and abdomen) | Previous pruritus with opioids | Administer an antihistamine such as chlorphenamine (may be contraindicated in patients who are becoming increasingly sedated) or a small dose of naloxone (administer with caution as this can easily reverse analgesia)
If pruritus does not resolve, consider switching to another opioid or removing the opioid from the infusion (Macintyre and Schug [128]) |
| Urinary retention | More likely to occur if opioids and local anaesthetic agents are infused in combination | Catheterize patient |
Assessment of pain for patients with epidural analgesia
Pain should be assessed (at rest and on movement) at the same time that the patient's routine observations are carried out. Simple numerical (e.g. 0–10 where 0 is no pain and 10 is the worst pain imaginable) or verbal rating scales (e.g. none, mild, moderate, severe or very severe) can be used.
When used for intractable cancer pain management, the aim of epidural/intrathecal analgesia is to improve the overall quality of life of the patient. Although it is acceptable to use simple pain assessment rating scales, a more in‐depth pain assessment scale may also be used such as the BPI (Tan et al. [210]).
Equipment and prescription safety checks
When a patient is receiving a continuous infusion of epidural/intrathecal analgesia, it is advisable to carry out the safety checks given in Table 22.8 at least once per shift.
Table 22.8 Epidural/intrathecal analgesia: safety checklist
| Checklist | Rationale |
|---|---|
| Check the prescription and rate of the epidural/intrathecal infusion | To ensure epidural/intrathecal drugs are being administered correctly |
| Check the epidural/intrathecal infusion/syringe pump extension set is connected to the epidural catheter and not to any other access device | To ensure drugs are administered via the correct route |
| Check the bacterial filter is securely attached to the epidural/intrathecal catheter | To prevent accidental disconnection of the catheter from the filter |
| Check that the dressing over the epidural/intrathecal catheter exit site is secure | To prevent catheter dislodgement and minimize the risk of contamination of the catheter site |
Removal of epidural/intrathecal catheter
Before an epidural/intrathecal catheter is removed, it is essential to consider the clotting status of the patient's blood. If the patient is fully anticoagulated, a clotting profile must be performed and advice sought from the anaesthetic/pain management/medical staff as to when the catheter can be safely removed. If the patient is receiving a prophylactic anticoagulant, the following guidelines are recommended (Gogarten et al. [86], Harrop‐Griffiths et al. [91], Horlocker et al. [102], Horlocker [101]).
Low‐dose low molecular weight heparin
If this is given once daily, the epidural/intrathecal catheter should be removed at least 12 hours after the last injection and several hours prior to the next dose. The timing will depend on the manufacturer's recommended guidelines but it is recommended that epidural or intrathecal catheters are removed and the next dose should not be given for minimum of 4 hours after removal.
Unfractionated heparin
The epidural/intrathecal catheter should be removed following local guidelines and the advice of the anaesthetic/pain management team.
Discharge planning
If it is anticipated that the patient will go home with a continuous epidural or intrathecal infusion, the patient's general practitioner and community nursing team should be consulted at the outset to determine whether they are willing to be involved and/or trained in the management of epidural/intrathecal analgesia care.
Arrangements should also be made with the primary healthcare team for the provision of a suitable epidural/intrathecal pump and the supply of reconstituted syringes/infusion bags. Primary care teams, patients and their families will need to be trained and supplied with the appropriate equipment, drugs, catheter filters, information about the infusion pump, how to identify a catheter‐related or systemic infection and what to do if pain occurs or complications arise. For implanted ITDD devices, the patient must be provided with all information to manage the system at home, when they will need to return for the pump to be refilled and who to contact in an emergency.
Contact numbers must be provided in case specialist advice is needed.
Complications
Pain
If pain is not controlled and the infusion has already been titrated according to hospital guidelines, the pain/anaesthetic team should be contacted for advice after checking the following.
- The catheter is still in situ.
- The catheter is still connected to the bacterial filter.
- There are no leaks within the system.
- The height of the epidural/intrathecal block. This will indicate whether the block has fallen below the upper limit of the incision or pain site. To check the height of the block, use a small piece of ice or cold solution (ethyl alcohol). Start at the top of the chest above the patient's incision or pain site. Gently dab the ice (or apply the cold solution) down each side of the patient's body (one side and then the other). Use a dermatome map to assess the upper and lower limits of where the sensation changes (see Figure 22.11).
If the height of the block has fallen below the upper limit of the incision or pain site, the pain/anaesthetic team may undertake the following: give the patient a bolus dose of local anaesthetic agent to re‐establish the block, and reposition the epidural catheter. If either of these fails, other methods of analgesia need to be considered.
Haematoma
An epidural haematoma can arise from trauma to an epidural blood vessel during catheter insertion or removal. Although the incidence of a haematoma occurring is extremely low, particular care must be taken in patients receiving thromboprophylaxis. Initial symptoms include back pain and tenderness. As the haematoma expands to compress the nerve roots or the spinal cord, this proceeds to sensorimotor weakness (Chapman and Day [36]).
Abscess formation
Infection can be introduced into the epidural/intrathecal space from an exogenous source such as contaminated equipment or drugs or breaches of aseptic technique during insertion and maintenance of spinal catheters (including management of disconnections) or from an endogenous source during episodes of bacteraemia or migration of bacteria through the insertion site (Macintyre and Schug [128]). Alternatively, the catheter can act as a wick through which the infection tracks down from the entry site on the skin to the epidural/intrathecal space (Wheatley et al. [232]). The risk of infection is increased in patients with a malignancy or diabetes or those who are immunocompromised or intravenous drug users. Symptoms include increasing and persistent back pain and tenderness accompanied by signs of infection (redness and/or discharge from the catheter exit site) (Day [48], Macintyre and Schug [128]).
Complications specific to epidural analgesia
Dural puncture
This occurs when the dura mater is inadvertently punctured during the placement of the epidural catheter. The main symptom is a headache, which arises from leakage of CSF through the dura.
Catheter migration
Catheter migration is extremely rare, occurring in less than 0.2% of patients (Wheatley et al. [232]). The catheter may migrate into either a blood vessel or the CSF. If it migrates into a blood vessel, opioid or local anaesthetic toxicity will occur. Opioid toxicity results in sedation and respiratory depression. Local anaesthetic toxicity results in circumoral tingling, numbness, twitching, convulsions and apnoea (D'Arcy [44]). If the catheter migrates into the CSF, the epidural opioids and local anaesthetic agents may reach as high as the cranial subarachnoid space. If this occurs the respiratory muscles are paralysed together with the cranial nerves, resulting in apnoea, profound hypotension and unconsciousness (Macintyre and Schug [128]).
Complications specific to intrathecal analgesia
Meningitis
Meningitis is a rare complication of intrathecal analgesia. The epidural route is often considered safer as the intact dura serves as an effective barrier to the spread of infection to the subarachnoid space. In fact, similar infection rates are reported with both intrathecal and epidural administration (Mercadante [146]). The incidence of major infections varies widely but is reported by Ballantyne and Carwood ([6]) as zero and as approximately 5% by Sloan ([207]) for epidural and intrathecal therapy with external pump systems. If the patient presents with headaches, fever, neck stiffness or photophobia, they must be reviewed as a matter of urgency by the medical/anaesthetic team. If meningitis is suspected, CSF samples can be obtained and sent to microbiology for analysis, and antibiotic therapy initiated promptly (Baker et al. [5], Day [48]).
