Healthcare and Medicine Reference
In-Depth Information
Table 4.3 Patient factors indicating the need for expert assistance.
Anatomy
Short neck
Morbid obesity, especially central
Receding jaw
Macroglossia
Facial or airway trauma
Inhalational injury to airway or oropharynx
Physiology
Daily symptoms from:
pulmonary disease
cardiovascular disease
cerebrovascular disease
Hiatus hernia (symptomatic)
Obstructive sleep apnoea
Poorly controlled hypertension
Hepatic or renal failure (delayed excretion)
General
Full stomach (risk of aspiration; delay procedure if possible for 2 hours
following clear fl uids and 6 hours following food)
Previous hypersensitivity to sedative/anaesthetic agents
Nauseated or vomiting
Figure 4.4 Propofol infused into peripheral cannula.
transient 'jerky' limb movements. The most common side-effect is
of pain on injection, which can be reduced by adding 1 mL of 0.5%
lidocaine to a 20-mL syringe.
There is no antagonist to propofol, but the clinical duration of
action is brief - of the order of 20 minutes.
Ketamine
Ketamine and its active metabolite norketamine are non-compet-
itive antagonists of the N -methyl- D -aspartate (NMDA) receptor,
normally acted upon by the excitatory neurotransmitter glutamate.
Ketamine has potent analgesic effects in addition to sedative and,
in high dose, hypnotic effects. Its use is limited by emergence phe-
nomena in adults including vivid hallucinations and nightmares.
Ketamine has a relatively wide therapeutic window, causing less
hypotension (in fact it may cause hypertension and tachycardia)
than other sedatives. It may be a suitable choice of agent in remote
areas, particularly in children and the very elderly and in trauma
and burns patients.
Since January 2006, ketamine has been a Class C controlled drug.
If a practical procedure is to be performed for a patient already in
pain (for example, a central venous catheter for a trauma patient),
then analgesia should be addressed fi rst. Opiates and any adjuncts
should be administered to satisfactorily control the pain before any
attempt at sedation. Morphine remains the most appropriate and
effective opioid analgesic for the vast majority of situations, and
should be titrated intravenously in the acute setting.
Entonox ®
This mixture of 50% nitrous oxide and 50% oxygen can provide
moderate analgesia of very brief duration for some procedures.
Particular applications include labour, changes of dressings and
manipulations of fractures. Benefi t may be derived for some other
practical procedures. Apart from the very brief duration of action,
use is limited by euphoria and nausea.
Dose
Ketamine is available in three strengths: 10 mg/mL, 50 mg/mL and
100 mg/mL. This wide range of strength demands vigilance. It is
good practice to dilute any strength to 10 mg/mL for use in seda-
tion. A suitable initial dose is 25-70 mg (or 0.5-1 mg/kg), with
further doses of 15-35 mg (or 0.25-0.5 mg/kg) as required. The
clinically effective duration of action is around 10-20 minutes.
Step-by-step guide: safe sedation
Assess the patient for any risk factors that may indicate the need
1
for the presence of an experienced anaesthetist (Table 4.3).
Ensure that the patient has given their informed consent to both
2
the procedure and the sedation.
Ensure that all equipment including monitoring and emer-
3
gency equipment, and all drugs including emergency drugs, are
checked and immediately to hand. Clarify lines of communica-
tion should complications occur (e.g. obtain contact details for
on-call anaesthetist).
Identify the individual responsible for monitoring and recording
Side-effects
As stated above, emergence phenomena are the most troublesome
side-effect. Loss of airway is rare, and tachycardia and hypertension
may result. Caution should be exercised in patients with potentially
raised intracranial or intraocular pressures.
There is no antagonist to ketamine.
4
observations, not the person administering sedation.
Wear non-sterile gloves and a disposable plastic apron, and con-
5
Opioid analgesics
These agents are used where an intervention is expected to cause
moderate to severe pain. With the appropriate use of local anaes-
thesia, reassurance and sedation they should not be indicated for
any of the procedures described in this topic.
sider personal protective equipment.
Establish and secure a peripheral venous cannula (Chapter 10).
6
7
Prepare the agent to be used. If not prediluted, dilute to a suitable
volume (10-20 mL) to allow titration of dose, according to
manufacturer's instructions.
 
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