Page 406 Acute Pain Management

Opioid and non‐opioid adjuvants have been added to caudal local anaesthetic with the aim
of improving the efficacy or duration of analgesia. Addition of morphine to caudal local
anaesthetic prolonged analgesia, but dose‐related side effects were relatively common
(Bozkurt et al, 1997 Level IV; Cesur et al, 2007 Level II). Clinically significant respiratory depression
has been reported, particularly with higher doses and in younger patients (de Beer & Thomas,
2003). Side effects are potentially less with lipid soluble opioids, but while fentanyl may
prolong caudal analgesia slightly (Constant et al, 1998 Level II), others have shown no benefit
(Kawaraguchi et al, 2006 Level II). Supplementing general anaesthesia with caudal blockade
(bupivacaine with morphine) reduced time to extubation and the period of mechanical
ventilation following cardiac surgery, but there was no difference in hospital stay or pain
relief (Leyvi et al, 2005 Level III‐2).
Addition of clonidine (1 to 2 mcg/kg) to caudal local anaesthetic prolonged analgesia
(Ansermino et al, 2003 Level I). Effects on analgesic efficacy could not be assessed by meta‐
analysis due to variability in study design and outcome measures. Clinically important sedation
occurred with higher doses (5 mcg/kg) (Ansermino et al, 2003 Level I). Clonidine 1 mcg/kg with
ropivacaine 0.2% has been shown to have a longer duration than either ketamine 0.5% with
ropivacaine or plain ropivacaine (Akbas et al, 2005 Level II).
Preservative‐free ketamine 0.25 to 0.5 mg/kg prolonged analgesia without significant side
effects, but higher doses (1 mg/kg) increased behavioural side effects (Ansermino et al, 2003
Level I). Levobupivacaine 0.175% with ketamine 0.5 mg/kg appears more effective than
levobupivacaine 0.2% alone (Locatelli et al, 2008 Level II). Other adjuncts such as neostigmine
and midazolam, while extending block duration offered little if any advantage over clonidine
or preservative‐free ketamine (Kumar et al, 2005 Level II). In addition, neostigmine was
associated with a high incidence of dose‐related vomiting when used as an adjunct (Batra et al,
2003 Level II).
The neurotoxicity of non‐opioid spinal additives has not been systematically evaluated in
neonates and children (Howard et al, 2008).
Epidural analgesia
As the epidural space is relatively large with loosely packed fat in neonates, catheters can be
threaded from the sacral hiatus to lumbar and thoracic levels (Tsui, 2004 Level IV). In older
infants, various techniques have been suggested to improve correct placement including
CHAPTER 10 Level IV; Willschke et al, 2006 Level IV). Insertion of epidural catheters at the segmental level
ultrasound, nerve stimulation and ECG guidance (Tsui & Finucane, 2002 Level IV; Tsui, 2004
required for surgery was more reliable in older children, and has been shown to be safe in
experienced hands with appropriate size equipment (Giaufre et al, 1996 Level IV; Llewellyn &
Moriarty, 2007 Level IV).
Continuous epidural infusions of bupivacaine are effective and safe in children (Llewellyn &
Moriarty, 2007 Level IV) and can provide similar levels of analgesia to systemic opioids (Wolf &
Hughes, 1993 Level II). In children 7 to 12 years of age, PCEA provided analgesia similar to a
continuous infusion. Total local anaesthetic dose was reduced with PCEA but no differences in
side effects were detected (Antok et al, 2003 Level III‐1). Due to reduced clearance and the
potential for accumulation of bupivacaine, the hourly dose should be reduced and the
duration of therapy limited to 24 to 48 hours in neonates (Larsson et al, 1997 Level IV).
Postnatal age and weight influence the pharmacokinetic profile of levobupivacaine, with
slower absorption and clearance in neonates and infants (Chalkiadis & Anderson, 2006 Level IV).
Although plasma concentrations increased, they remained low after 24 hours of epidural
levobupivacaine infusion in children aged over 6 months (Lerman et al, 2003 Level II). Epidural

358 Acute Pain Management: Scientific Evidence