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5.3.3 Ketamine

Neuraxial
Some commercially available preparations of ketamine contain an untested preservative
(benzethonium chloride) and a low pH (pH 3.5 to 5.5) and so cannot be recommended for
intrathecal use in humans (Hodgson et al, 1999).
The addition of intrathecal ketamine to bupivacaine did not prolong postoperative analgesia
or reduce analgesic requirements, but did lead to significantly more nausea and vomiting,
sedation, dizziness, nystagmus and ‘strange feelings’ (Kathirvel et al, 2000 Level II).
Early postoperative analgesia was improved by the use of epidural racemic ketamine with
bupivacaine for lower limb amputations, although pain at 1 year was not different;
perioperative opioids were not used (Wilson et al, 2008 Level II). The combination of ketamine
with opioid‐based (+/‐ local anaesthetic) solutions for epidural analgesia improved pain relief
(Subramaniam et al, 2004 Level I) and may reduce overall opioid requirements (Walker et al, 2002
Level I) without increasing the incidence of adverse effects (Walker et al, 2002 Level I;
Subramaniam et al, 2004 Level I).
A combination of bupivacaine, ketamine and midazolam administered intrathecally prolonged
the analgesic time following lower limb surgery compared with bupivacaine alone or
bupivacaine with ketamine; however the authors cautioned that the safety of such
combinations has not yet been established (Murali Krishna et al, 2008 Level II).
Use of intrathecal S(+) ketamine with bupivacaine for Caesarean section decreased time to
onset and increased spread of the block, but did not prolong the duration compared with
fentanyl (Unlugenc et al, 2006 Level II). CHAPTER 5
Caudal epidural ketamine 0.25 to 0.5 mg/kg in children, in combination with local anaesthetic
prolonged analgesia with few side effects (Ansermino et al, 2003 Level I; Tsui & Berde, 2005) (see
also Section 10.7.2).
Peripheral sites
Most studies on the use of ketamine alone or with local anaesthesia, show no analgesic
benefit for peripheral neural blockade, such as brachial plexus block for arm surgery, (Lee et al,
2002 Level II), intra‐articular injection (Rosseland et al, 2003 Level II) or wound infiltration such as
following Caesarean section (Zohar et al, 2002 Level II) or inguinal hernia repair (Clerc et al, 2005
Level II), although pain scores were lower with preincisional ketamine versus saline in
circumcision (Tan et al, 2007 Level II). Adding ketamine to lignocaine IVRA did not result in better
pain relief compared with ketamine given intravenously (Viscomi et al, 2009 Level II).
Topical
Topical administration of ketamine might result in effective systemic plasma concentrations
making it difficult to interpret any local effects (Poyhia & Vainio, 2006). A transdermal ketamine
patch (delivering 25 mg over 24 hours) reduced analgesic consumption after gynaecological
surgery (Azevedo et al, 2000 Level II) but analgesic effects from topical ketamine (3 mL 0.3%)
applied to the tonsillar fossa after tonsillectomy, although superior to placebo, added no
benefit to topical morphine (Canbay et al, 2008 Level II).
Topical ketamine as a mouthwash has been reported to be effective in reducing pain and
opioid consumption from oral mucositis at rest and with eating (Slatkin & Rhiner, 2003).

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