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prehospital environment, but this is not encouraged because of the unpredictable impact
upon the pharmacokinetics in a poorly perfused patient.
Both morphine and fentanyl are commonly used for prehospital analgesia. Morphine (Bruns et
al, 1992 Level IV; Fullerton‐Gleason et al, 2002 Level IV) and fentanyl (Kanowitz et al, 2006 Level IV),
as well as tramadol (Ward et al, 1997 Level IV) have been shown to provide effective and safe
pain relief in patients being transported by road. Fentanyl was also safe and effective when
given to patients during helicopter transfers (Thomas et al, 2005 Level IV; Krauss et al, 2009
Level IV).
Morphine doses of 0.1 mg/kg IV followed by 0.05 mg/kg every 5 mins as needed provided
more rapid pain relief and patient satisfaction than doses that were 50% lower (Bounes et al,
2008 Level II).
In a comparison of IV fentanyl and morphine bolus doses given every 5 minutes as needed
for prehospital analgesia, no difference was found in pain relief or incidence of side effects
(Galinski et al, 2005 Level II). Similarly, there was no difference in pain relief or adverse effects
reported in a comparison of IV tramadol and morphine (Vergnion et al, 2001 Level II).
When used to treat acute cardiac chest pain during prehospital transfer, IV alfentanil provided
more rapid relief than IV morphine (Silfvast & Saarnivaara, 2001 Level II). IN fentanyl and
IV morphine were equally effective for patients with cardiac and non‐cardiac acute pain
(Rickard et al, 2007 Level II).
A comparison of 5 mg and 10 mg nalbuphine doses given IV and repeated at 3‐minute
intervals to a total of 20 mg, showed that use of the larger dose led to better pain relief but
higher patient‐reported drowsiness; over half the patients in both groups still had significant
pain on arrival at the hospital (Woollard et al, 2004 Level II).
Inhalational agents
Inhalational analgesics can provide early pain relief in the prehospital environment and are
used before opioids in many situations. However, variations in the availability of different
agents have a marked impact on regional practices. In one series, patients with extremity
fractures were more likely to receive N 2O than morphine (White et al, 2000), whereas in
another series N 2O was not used (Rogovik & Goldman, 2007). Methoxyflurane is not available in
CHAPTER 9 many countries, but in Australia it has replaced N 2O in most prehospital settings. Provision of
N 2O in ambulances is hampered by difficulties providing a scavenger system that minimises
occupational exposure and the bulk/logistical issues associated with managing cylinders of
oxygen and nitrous oxide (Entonox® cylinders are a mixture of 50% N 2O and 50% oxygen) that
separate at low temperatures. The demand valves are costly and require maintenance, and
the inability to activate the valve and effectively use Entonox® equipment has been rated as a
major factor limiting use in children under 5 year (Watkins, 2006). There have been no RCTs of
methoxyflurane (Grindlay & Babl, 2009) or N 2O (Faddy & Garlick, 2005), and no large case series
comparing efficacy with other analgesic agents in the prehospital setting.
Methoxyflurane reduced pain scores (mean 2.47±0.24 on NRS 0 to 10) in adults, the majority
of whom had musculoskeletal pain. The incidence of nausea was 8%, and 11% had increased
drowsiness (Buntine et al, 2007 Level IV). When graded by the paramedic, methoxyflurane also
reduced pain scores in children (Babl et al, 2006 Level IV). The overall incidence of drowsiness
was 27%, but the risk of deep sedation was significantly higher in younger children. In both of
these studies, methoxyflurane was delivered by a Penthrox® inhaler which contains 3 mL of
methoxyflurane and lasts for 25 to 30 minutes (Medical Developments International, 2001). There
have been no reports of toxicity with analgesic use if doses are limited to 3 mL repeated once
with a maximum of 15 mL per week, or a maximum of 0.5% for one hour (Grindlay & Babl, 2009)
(see also Section 4.3.1).
296 Acute Pain Management: Scientific Evidence