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effect of one opioid dose before another dose can be delivered. However, if it is too long the
effectiveness of PCA could be reduced. There were no differences in pain relief, side effects or
anxiety when lockout intervals of 7 or 11 minutes for morphine and 5 or 8 minutes for fentanyl
were used (Ginsberg et al, 1995 Level II).
Concurrent background (continuous) infusions
There is no good evidence to show that the addition of a background infusion to IV PCA
improves pain relief or sleep, or reduces the number of demands (Owen, Szekely et al, 1989
Level II; Parker et al, 1991 Level II; Parker et al, 1992 Level II; Dal et al, 2003 Level II). Large audits of
adult patients have also shown that the risk of respiratory depression is increased when a
background infusion is added (Notcutt & Morgan, 1990 Level IV; Fleming & Coombs, 1992 Level IV;
Schug & Torrie, 1993 Level III‐2; Sidebotham et al, 1997 Level IV). In adults, the routine use of a
background infusion is therefore not recommended, although it may be useful in opioid‐
tolerant patients (see Section 11.7).
Dose limits
Limits to the maximum amount of opioid that can be delivered over a certain period
(commonly 1 or 4 hours) can be programmed into most PCA machines. There is no good
evidence of any benefit that can be attributed to these limits.
Loading dose
There is enormous variation in the amount of opioid a patient may need as a ‘loading dose’
and there is no good evidence of any benefit that can be attributed to the use of the loading
dose feature that can be programmed into PCA machines. PCA is essentially a maintenance
therapy, therefore a patient’s pain should be controlled before PCA is started by
administration of individually titrated loading doses (Macintyre & Schug, 2007; Macintyre &
Coldrey, 2008). IV opioid loading improved the analgesic efficacy of subsequent oral and
CHAPTER 7 7.1.4 Efficacy of PCA using other systemic routes of administration
PCA opioid therapy in the treatment of acute sickle cell pain (Rees et al, 2003 Level II).

Subcutaneous PCA
Data on the effectiveness of SC PCA compared with IV PCA are variable and inconsistent. Both
similar (Urquhart et al, 1988 Level II; White, 1990 Level II; Munro et al, 1998 Level II; Bell et al, 2007
Level II) and significantly better (Dawson et al, 1999 Level II; Keita et al, 2003 Level II) pain relief has
been reported, as well as the same (Urquhart et al, 1988 Level II; Munro et al, 1998 Level II; Dawson
et al, 1999 Level II; Keita et al, 2003 Level II) and a higher incidence of nausea and vomiting (White,
1990 Level II) or pruritus (Bell et al, 2007 Level II). Compared with IV PCA, SC PCA may (Urquhart et
al, 1988 Level II; White, 1990 Level II; Dawson et al, 1999 Level II; Bell et al, 2007 Level II) or may not
(Munro et al, 1998 Level II) result in higher opioid use.
Oral PCA
Oral PCA, using a modified IV PCA system, is as effective as IV PCA (Striebel et al, 1998 Level II).
An oral PCA device has been developed that uses radiofrequency identification technology to
allow patients in an oncology ward access (subject to a lockout interval) to a medication‐
dispensing system at the bedside (Rosati et al, 2007 Level IV).
Intranasal PCA
Patient‐controlled intranasal analgesia (PCINA) fentanyl can be as effective as IV PCA (Striebel
et al, 1996 Level II; Toussaint et al, 2000 Level II; Manjushree et al, 2002 Level II; Paech et al, 2003
Level II), as is butorphanol (Abboud et al, 1991 Level II). As would be expected from the data on
IN bioavailability of opioids (see Section 6.6.1), higher doses are needed via the IN route

176 Acute Pain Management: Scientific Evidence