Chapter 10: Pain assessment and management
Skip chapter table of contents and go to main content
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 (Macintyre and Schug [99]). It is therefore important to maintain the hourly infusion rate at a volume that keeps the appropriate nerves blocked.
If the sensory block is too low, it may not provide sufficient pain relief or blockade of the intended site (e.g. surgical site). 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 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 opioids and local anaesthetic agents.
Opioids
For opioids, the side‐effects include the following:
-
Respiratory depression: this is due to the action of opioids on the respiratory centre. 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 [99]).
- 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 [99]). This is less likely to occur with lipid‐soluble opioids such as fentanyl.
- Sedation: although there may be many different causes of sedation, epidural opioids can cause sedation owing to their effect on the central nervous system. Opioid‐induced sedation is often an early warning sign of respiratory depression.
- Nausea and vomiting: nausea and vomiting are 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 and a consequence of activation of opioid receptors in the spinal cord (Schug et al. [166]).
- Urinary retention: this is due to opioid inhibition of the micturition reflex, which is evoked by increases in bladder volume (Schug et al. [166]).
Local anaesthetic agents
For local anaesthetic agents, the side‐effects include the following:
- Hypotension: this can be caused by two mechanisms. Firstly, local anaesthetic agents can spread outside the epidural 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 [99]). Secondly, 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 [99]).
- Motor blockade: this will depend on the concentration and total dose of local anaesthetic agent used and the position of the epidural or intrathecal catheter (Schug et al. [166]). 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 opioids, blockade of the nerves supplying the bladder sphincter can cause urinary retention.
Patient monitoring
Routine monitoring of patients for these side‐effects must be carried out to facilitate early management. The patient's blood pressure, respiratory rate and peripheral tissue oxygenation should be monitored continuously initially and then according to local policy and as the patient's condition dictates.
For guidance on managing the side‐effects associated with epidural opioids and local anaesthetic agents, see Table 10.8.
Table 10.8 Epidural 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 eight breaths a minute or below:
|
| Concurrent use of systemic opioids or sedatives: patients receiving opioids by epidural infusion should not be given opioids by any other route unless given in the palliative care setting for breakthrough pain. | Take the following steps:
| |
Sedation:
| See ‘Respiratory depression’ above. | Take the following steps according to the patient's level of sedation:
|
| Hypotension |
Patients with hypovolaemia.
Patients with a high thoracic epidural in whom the concentration of local anaesthetic agent and volume of infusion causes blockade of the cardio‐accelerator nerves. | If blood pressure falls suddenly:
|
| Motor blockade | This is 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 catheter then the lumbar motor nerves are likely to be blocked, causing leg weakness. | Do not attempt to mobilize the patient if leg weakness is evident. Contact the pain or anaesthetic team for advice: reducing the concentration of the local anaesthetic agent or the rate of the epidural infusion may help to resolve this problem ( Schug et al. [166]). |
| Nausea and vomiting | Previous episodes of nausea and vomiting with opioids. Exacerbated by low blood pressure. | Consider the following: |
| 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 ( Schug et al. [166]). |
| Urinary retention | More likely to occur if opioids and local anaesthetic agents are infused in combination. | If the patient is in retention, they may require an indwelling urinary catheter. Patients should return to normal bladder function once the epidural has been discontinued ( Macintyre and Schug [99]). |
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. Refer to Procedure guideline 10.1: Pain assessment.
Equipment and prescription safety checks
When a patient is receiving a continuous infusion of epidural analgesia, it is advisable to carry out the safety checks listed in Table 10.9 at least once per shift.
Table 10.9 Epidural: safety checklist
| Check | Rationale |
|---|---|
| Check the prescription and rate of the epidural infusion | To ensure epidural drugs are being administered correctly |
| Check the epidural extension set is connected to the NRFit 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 catheter | To prevent accidental disconnection of the catheter from the filter |
| Check that the dressing over the epidural catheter exit site is secure | To prevent catheter dislodgement and minimize the risk of contamination of the catheter site |
Discharge planning
In rare circumstances, patients with intractable cancer pain can be considered to go home with a continuous epidural infusion. See The Royal Marsden Manual of Cancer Nursing Procedures (Lister et al. [97]) for further detail about discharge planning with an epidural.
