Chapter 10: Pain assessment and management
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Pre‐procedural considerations
Equipment
Epidural catheters are inserted using:
- a spinal (Tuohy) needle (a bevelled, curved‐tip needle to reduce the risk of accidental dural puncture, with 1 cm length markings), either 16 or 18 G
- an epidural or 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)
- a connector (to ensure safe catheter fixation)
- a loss‐of‐resistance device (to aid clear identification of the epidural space).
This equipment often comes in prepared sterile disposable epidural trays or packs (McClymont and Celnick [107]) (Figure 10.11).
Figure 10.11 Epidural insertion kit. Source: Reproduced with permission of Vygon.
Dressings
The dressing over the epidural exit site needs to fulfil the following three functions:
- help secure the epidural catheter
- minimize the risk of infection
- allow observation of the site without disturbing the dressing.
A transparent moisture‐responsive occlusive dressing (e.g. Tegaderm, OPSITE or IV3000) fulfils these functions. The epidural site should be inspected daily and the dressing changed at least once per week or more frequently if there is any serous discharge from the site (see Procedure guideline 10.4: Epidural exit site dressing change).
Pharmacological support
Combination of drugs used
Epidural infusions of local anaesthetic and opioid combinations are commonly used (McClymont and Celnick [107], Tosounidis et al. [178]). The rationale behind their combined use is based on the observation that better analgesia is achieved with lower doses of each drug, as this minimizes the drug‐related side‐effects produced by higher concentrations (Duncan et al. [51]). 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 and intrathecal routes (Grissinger [71], NPSA [131]).
Specific patient preparation
Patients undergoing an epidural 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 a full set of resuscitation equipment.
Position of the epidural 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 (i.e. the surgical site), the tip of the spinal catheter should be placed within the mid‐dermatomal distribution of the pain site (Table 10.7). This achieves optimal analgesia using the smallest possible amount of drugs (FPM [58]). If the catheter is placed below the dermatomes supplying the pain site, then analgesia is likely to be inadequate (Macintyre and Schug [99]).
Table 10.7 Optimal catheter locations for different surgical sites
| Surgical site | Catheter location |
|---|---|
| Thoracic | T6–T9 |
| Upper abdominal | T7–T10 |
| Lower abdominal | T9–L1 |
| Hip or knee | L1–L4 |
Effectiveness of the blockade
The spinal nerves supply specific areas of skin known as dermatomes (see Figure 10.10). Sensitivity to changes in temperature (ethyl chloride spray) along the sensory dermatome can be used to assess the level of epidural block (see Procedure guideline 10.3: Epidural sensory blockade: assessment). This level should be checked to ensure that the epidural is providing pain relief by covering the area of the site of pain, but it is also necessary to maintain safety during the administration of epidural infusions.
Procedure guideline 10.3
Epidural sensory blockade: assessment
Procedure guideline 10.4
