Page 240 Acute Pain Management

Pruritus is common after intrathecal morphine, being reported in up to 37% of patients
(Gwirtz et al, 1999 Level IV), although the number requiring treatment was lower (5.1%).
This rate was significantly higher than that for patients receiving IV PCA morphine (OR 3.85;
95% CI 2.40 to 6.15) (Meylan et al, 2009 Level I). Pruritus can be difficult to treat and a variety
of agents have been used including low dose naloxone, nalbuphine, ondansetron, propofol
and antihistamines. The itch is thought to be caused by stimulation of spinal and supraspinal
mu‐opioid receptors. Nalbuphine (Charuluxananan et al, 2003 Level II) and ondansetron
(Charuluxananan et al, 2003 Level II; Tzeng et al, 2003 Level II; Pirat et al, 2005 Level II) were effective
in reducing spinal opioid‐induced pruritus, although this has not been consistently reported
(Sarvela et al, 2006 Level II; Siddik‐Sayyid et al, 2007 Level II).
Postoperative nausea and vomiting (PONV) is also common after intrathecal morphine with
incidences reported at 30% and 24% respectively, although this rate was similar to IV PCA
morphine (Meylan et al, 2009 Level I). Ondansetron or scopolamine was equally effective in
reducing emesis with intrathecal morphine analgesia for Caesarean section, although
scopolamine use was associated with more anticholinergic side effects (Harnett et al, 2007
Level II). The combination of ondansetron with either dexamethasone or droperidol had
a better antiemetic effect after gynaecological surgery compared with droperidol plus
dexamethasone (Sanchez‐Ledesma et al, 2002 Level II); although dexamethasone plus droperidol
was superior to either alone (Wu et al, 2007 Level II).
In parturients, reactivation of oral herpes simplex labialis was more frequent (38%) following
intrathecal morphine for labour analgesia than IV PCA morphine (16.6%) (Davies et al, 2005
Level II).
Adjuvant drugs
A variety of adjuvant drugs has been used with intrathecal analgesia, including clonidine,
ketamine, neostigmine and midazolam. Many drugs are not licensed for use as spinal analgesic
CHAPTER 7 agents; however adequate evidence from the literature may make their use acceptable.

For more detail see Section 5.3.
Combined spinal-epidural versus epidural analgesia in labour
7.3.2
Combined spinal epidural (CSE) analgesia provided faster onset of analgesia compared with
epidural analgesia. However, as CSE did not improve satisfaction or mobilisation, and
increased the risk of pruritus, clinical advantages over epidural analgesia (either traditional or
low dose) are limited (Simmons et al, 2007 Level I) (see Section 11.1). Traditional (higher‐dose)
epidural analgesia, unlike low‐dose epidurals, was associated with increased urinary retention
compared with CSE (Simmons et al, 2007 Level I).

Key messages
1. Intrathecal morphine offers improved analgesia and opioid‐sparing for up to 24 hours
especially following abdominal surgery (S) (Level I).
2. Intrathecal morphine doses of 300 mcg or more increase the risk of respiratory depression
(N) (Level I).
3. After major surgery, the incidence of respiratory depression and pruritus is higher with
intrathecal morphine compared with IV PCA opioids, but there is no difference in the
incidence of nausea and vomiting (N) (Level I).

192 Acute Pain Management: Scientific Evidence