Patient controlled opioid analgesia versus non‐patient controlled opioid analgesia for postoperative pain
This is an updated version of the original Cochrane review published in Issue 4, 2006. Patients may control postoperative pain by self administration of intravenous opioids using devices designed for this purpose (patient controlled analgesia or PCA). A 1992 meta‐analysis by Ballantyne et al found a strong patient preference for PCA over non‐patient controlled analgesia, but disclosed no differences in analgesic consumption or length of postoperative hospital stay. Although Ballantyne's meta‐analysis found that PCA did have a small but statistically significant benefit upon pain intensity, a 2001 review by Walder et al did not find statistically significant differences in pain intensity or pain relief between PCA and groups treated with non‐patient controlled analgesia.
To evaluate the efficacy and safety of patient controlled intravenous opioid analgesia (termed PCA in this review) versus non‐patient controlled opioid analgesia of as‐needed opioid analgesia for postoperative pain relief.
We ran the search for the previous review in November 2004. For this update, we searched the Cochrane Central Register of Controlled Trials (CENTRAL 2014, Issue 12), MEDLINE (1966 to 28 January 2015), and EMBASE (1980 to 28 January 2015) for randomized controlled trials (RCTs) in any language, and reference lists of reviews and retrieved articles.
We selected RCTs that assessed pain intensity as a primary or secondary outcome. These studies compared PCA without a continuous background infusion with non‐patient controlled opioid analgesic regimens. We excluded studies that explicitly stated they involved patients with chronic pain.
Data collection and analysis
Two review authors independently extracted data, which included demographic variables, type of surgery, interventions, efficacy, and adverse events. We graded each included study for methodological quality by assessing risk of bias and employed the GRADE approach to assess the overall quality of the evidence. We performed meta‐analysis of outcomes that included pain intensity assessed by a 0 to 100 visual analog scale (VAS), opioid consumption, patient satisfaction, length of stay, and adverse events.
Forty‐nine studies with 1725 participants receiving PCA and 1687 participants assigned to a control group met the inclusion criteria. The original review included 55 studies with 2023 patients receiving PCA and 1838 patients assigned to a control group. There were fewer included studies in our updated review due to the revised exclusion criteria. For the primary outcome, participants receiving PCA had lower VAS pain intensity scores versus non‐patient controlled analgesia over most time intervals, e.g., scores over 0 to 24 hours were nine points lower (95% confidence interval (CI) ‐13 to ‐5, moderate quality evidence) and over 0 to 48 hours were 10 points lower (95% CI ‐12 to ‐7, low quality evidence). Among the secondary outcomes, participants were more satisfied with PCA (81% versus 61%, P value = 0.002) and consumed higher amounts of opioids than controls (0 to 24 hours, 7 mg more of intravenous morphine equivalents, 95% CI 1 mg to 13 mg). Those receiving PCA had a higher incidence of pruritus (15% versus 8%, P value = 0.01) but had a similar incidence of other adverse events. There was no difference in the length of hospital stay.
Since the last version of this review, we have found new studies providing additional information. We reanalyzed the data but the results did not substantially alter any of our previously published conclusions. This review provides moderate to low quality evidence that PCA is an efficacious alternative to non‐patient controlled systemic analgesia for postoperative pain control.
Ewan D McNicol, McKenzie C Ferguson, Jana Hudcova
Plain language summary
Patient controlled opioid analgesia versus non‐patient controlled opioid analgesia for controlling postoperative pain
Patients may control pain after surgery by self administration of analgesics (pain killers) using devices designed for this purpose (patient controlled analgesia or PCA). PCA involves self administration (by pushing a button) of small doses of opioids (such as morphine) intravenously by means of a programmable pump. Previous studies have shown that often patients prefer PCA to traditional methods of pain management, such as a nurse administering an analgesic upon a patient's request. This review demonstrated moderate to low quality evidence that PCA provided slightly better pain control and increased patient satisfaction when compared with non‐patient controlled methods. Patients tended to use slightly higher doses of medication with PCA and suffered a higher occurrence of itching, but otherwise side effects were similar between groups.
Ewan D McNicol, McKenzie C Ferguson, Jana Hudcova
Implications for practice
A limited amount of additional data were identified for this update, reinforcing the conclusions of our previous review. The fact that patient controlled analgesia (PCA) is now standard practice may account for the scarcity of new randomized controlled trials (RCTs) assessing its efficacy.
For people with postoperative pain
PCA has gained acceptance among patients despite the lack of evidence supporting clinical advantages from this review or previous reviews. Low quality evidence demonstrates that patients report greater satisfaction with, and in general prefer, PCA. While the reasons for this preference are unclear, they may be a function of increased patient autonomy and absence of delay in opioid administration. Patients should expect pain relief to be marginally superior to that achieved with nurse‐administered analgesia and a similar degree of side effects.
Our meta‐analysis provides moderate to very low quality evidence that PCA provides superior analgesia in comparison to non‐patient controlled regimens. Length of stay was similar in both groups. Despite slightly higher opioid consumption in participants using PCA, we found no increase in the occurrence of opioid‐induced adverse effects. Where available and appropriate, PCA should be offered to patients.
For policy makers
PCA for postoperative pain control continues to be commonly used in many hospitals in the western world, and in the absence of new evidence or advances in technology, is likely to remain so in the near future.
Very limited evidence suggests that PCA may be more costly than nurse‐administered analgesia. Our review does not demonstrate the potential for savings through reduced time to discharge. However, given that hospital reimbursement is, in part, contingent on patient satisfaction data in countries such as the United States, increases in direct costs may be offset by such policies.
Implications for research
While intravenous administration remains the most commonly used mode of PCA, several alternative modes have been applied in the clinical setting or in controlled clinical trials. Alternative routes of administration include oral, transdermal, inhaled, intranasal, and epidural, each with their own potential benefits and disadvantages. Oral, transdermal, inhaled, and intranasal administration modalities offer the potential advantage of reductions in cost, labor, and required expertise of staff, and increased patient mobility when compared to intravenous PCA. There are currently insufficient RCTs available to determine whether any of the above modes of PCA will prove more safe or effective than intravenous PCA.
While further trials investigating different surgeries may be helpful, the number of trials currently available for assessing overall efficacy of intravenous PCA is already extensive. More studies enrolling geriatric or pediatric populations, and those patients with risk factors such as chronic pain and substance abuse disorders, should be conducted. If possible, the quality of the future trials could be improved by introducing double‐blinding and by clearly defining criteria for inclusion.
The safety profile of PCA has not been fully established in this review. Further research from large epidemiological studies that include high‐risk patients and that assess programming error and device malfunction data are needed to provide a more complete picture of the risks associated with PCA.
Most studies used standard validated pain intensity scales and widely accepted opioid conversion values. However, mean differences in pain scores or opioid consumption may not accurately reflect differences between PCA and nurse‐administered analgesia. The use of dichotomous outcomes, such as the number of participants administering less than a predetermined cumulative amount of opioid may have greater validity.
Comparison between active treatments
There is a lack of either indirect or head‐to‐head comparisons of different opioids administered via PCA. While head‐to‐head studies were not considered for this analysis, evidence supporting the superiority of one opioid versus others or, conversely, a class effect would be helpful.