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Acute Pain | Chronic Pain | General

Effectiveness of acute postoperative pain management

Clinical bottom line

An extensive review of postoperative pain and pain relief after major surgery indicates that about 1 in 5 patients experiences severe pain, or poor or fair pain relief, after surgery. Moderate or severe pain at rest or on movement is common.


Reference

S Dolin et al. Effectiveness of acute postoperative pain management: I. Evidence from published data. British Journal of Anaesthesia 2002 89: 409-423.

Systematic review

The review sought studies that characterised the incidence of moderate to severe and severe pain after major surgery with three analgesic techniques - intramuscular analgesia, patient controlled analgesia and epidural analgesia. Studies of any architecture were looked for using MEDLINE, reference lists, and hand searching four major journals. Unpublished audit data were also included.

Studies had to have pain or pain relief as an outcome, be in abdominal, major gynaecological, orthopaedic or thoracic surgery. Pain had to be assessed using visual analogue scales or verbal rating scales, and give proportions of patients with pain or pain relief of particular intensity.The outcome sought was the incidence of analgesic failure, and is reported in various ways. For pain intensity it was moderate or severe, or severe pain. For pain relief it was poor, or poor to fair pain relief. For epidural studies, premature catheter dislodgement was also used as a marker of analgesic failure.

The shortest period of observation was 24 hours. Paediatric, day stay, and minor surgery, and where observations were for less than 24 hours were excluded. Intrathecal opioids were also excluded, as were combined spinal and epidural analgesia or regional blocks.

Results were pooled by weighting by the number of patients in each study.

Results

Pain intensity results were obtained from 123 papers with 19,909 patients, pain relief results from 53 papers with 9,068 patients and epidural catheter displacement from 32 papers with 13,629 patients. Most studies were published since 1985. The surgical disciplines were mixed, and differed somewhat between techniques; for instance, epidural analgesia was more often used with thoracic surgery.

Pain intensity

Moderate to severe pain at rest was reported by two thirds of patients receiving intramuscular analgesia (Figure 1, Table 1), 36% with patient controlled analgesia and 21% of those with epidural analgesia. Moderate to severe pain at rest fell by an average of 1.9% a year between studies from 1973 and 1999.

Figure 1: Moderate to severe pain at rest (IM= intramuscular, PCA = patient controlled analgesia)

Moderate to severe pain on movement was reported by 78% of patients receiving intramuscular analgesia (Figure 2, Table 1), 25% with patient controlled analgesia and 38% of those with epidural analgesia.

Figure 2: Moderate to severe pain on movement

Severe pain on movement was reported by 29% of patients receiving intramuscular analgesia (Figure 3, Table 1), 10% with patient controlled analgesia and 8% of those with epidural analgesia.

Figure 3: Severe pain

Pain relief

Poor pain relief was reported by 2-5% of patients, and poor or fair pain relief by 17-21% of patients (Figure 4, Table 1).

Figure 4: Pain relief with different techniques


Table 1: Summary of 95% confidence interval for pain intensity and pain relief results

Pain outcome

95% confidence interval of percentage

Moderate - severe pain at rest
IM

58-76

PCA

31-40

Epidural

18-24

Moderate-severe pain on movement
IM

too little data

PCA

8.4-42

Epidural

30-45

Severe pain
IM

19-39

PCA

12-21

Epidural

15-23

Poor pain relief
IM

too little data

PCA

1.8-5.4

Epidural

3.7-6.8

Poor or fair pain relief
IM

14-29

PCA

12-21

Epidural

15-24

Epidural catheter dislodgement

The overall mean incidence of premature catheter dislodgement was 5.7% (95% confidence interval 4.0 to 7.4%).

Comment

There are two ways of looking at this remarkable study. One is to examine it for systematic differences between techniques, and the other is to look at the results overall for the effectiveness of pain management.

This is perhaps not the place to look at differences between techniques in too much depth. The broad categories combine all sorts of different varieties, and look at them in different surgical conditions. They are not directly compared. Those comments aside there appeared to be little difference in terms of pain relief, though on pain intensity scales intramuscular analgesics tended to fare less well than PCA or epidurals. It is not clear, though, how much the technical failure of catheter dislodgement contributed to lower analgesic efficacy.

More important is the simple fact that severe pain, and poor or fair pain relief, was experienced by almost 1 in five patients. The audit commission in the UK has proposed a standard that less than 20% of patients should experience severe pain after surgery by 1997, falling to 5% by 2002. This review suggests that achieving that standard will be difficult.