C H A P T E R 2 7
General and local anaesthetic agents
423
should be used with caution in any individual at high
risk for developing it
to avoid development of malig-
nant hyperthermia.
Dantrolene, the preferred treatment
for malignant hyperthermia, should be readily available
whenever any of these drugs is used. These drugs should
be avoided in pregnancy and breastfeeding unless the
benefit clearly outweighs the risk to the fetus or baby
because of the CNS depressive effects of the drugs.
Adverse effects
Desflurane is associated with a collection of respiratory
reactions, including cough, increased secretions and
laryngospasm. Isoflurane is associated with hypoten-
sion, hypercapnoea, muscle soreness and a bad taste in
the mouth, but it does not cause cardiac arrhythmias or
respiratory irritation as do some other volatile liquids.
Clinically important drug–drug interactions
Caution should be used when any of these drugs is
combined with other CNS suppressants.
Prototype summary: Isoflurane
Indications:
Induction and maintenance of general
anaesthesia.
Actions:
Depresses the CNS, causing anaesthesia;
relaxes muscles; sensitises the myocardium to the
effects of noradrenaline and adrenaline.
Pharmacokinetics:
Route Onset
Peak Duration
Inhaled Rapid
Rapid End of inhalation
T
1/2
:
Unknown; minimally metabolised in the liver,
excreted in the urine.
Adverse effects:
Disorientation, restlessness,
bradycardia, tachycardia, hypoxia, acidosis,
malignant hyperthermia, hyperkalaemia,
respiratory depression, apnoea, dyspnoea,
arrhythmias, hepatic injury, ileus, shivering.
Volatile liquid anaesthetics can trigger malignant
hyperthermia and are contra-indicated in those
susceptible to malignant hyperthermia. They can
increase cerebrospinal pressure and should be
used with caution in those with raised intracranial
pressure. They can also cause hepatotoxicity in those
sensitised to halogenated anaesthetics. In children with
neuromuscular disease, inhalational anaesthetics are
very rarely associated with hyperkalaemia, resulting
in cardiac arrhythmias and death. Cardiorespiratory
depression, hypotension and arrhythmias are common
adverse effects of volatile liquid anaesthetics.
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BOX 27.2
Adverse reactions
Care considerations for
people receiving general anaesthetic agents
Assessment: History and examination
■
■
Assess for contraindications or cautions: any
known allergies to general anaesthetics
to avoid
hypersensitivity reactions
; impaired liver or
kidney function,
which might interfere with drug
metabolism and excretion
; myasthenia gravis
or cardiac or respiratory disease,
which may
be exacerbated by the depressive effects of the
drug
; personal or family history of malignant
hyperthermia,
which may be triggered by the use
of general anaesthetics.
■
■
Perform a physical assessment, including weighing
the person,
to determine the appropriate dosing of
the drug and to establish a baseline status before
beginning therapy and evaluate for any potential
adverse effects.
■
■
Assess the person’s neurological status, including
level of consciousness, affect, reflexes and pupil
size and reaction, and evaluate muscle tone and
response,
to monitor CNS depression and provide
appropriate support as needed.
■
■
Monitor vital signs, including temperature, pulse
and blood pressure, for changes, and auscultate
lung and heart sounds
to monitor for adverse
effects of the drugs.
■
■
Obtain an electrocardiogram (ECG)
to evaluate
for underlying cardiac problems that may be
exacerbated by the drug.
■
■
Assess skin colour and lesions
to monitor for
potential skin breakdown resulting from paralysis
and immobility while under anaesthesia.
■
■
Auscultate abdomen for bowel sounds
to evaluate
GI motility.
■
■
Monitor the results of laboratory tests, including
renal and liver function tests,
to determine the
possible need for a reduction in dose and evaluate
for possible toxicity.
Implementation with rationale
■
■
Keep in mind that the drug must be administered
by trained personnel (usually an anaesthetist)
because of the potential risks associated with its
use.
■
■
Have emergency equipment to maintain airway and
provide mechanical ventilation readily available
when person is not able to maintain respiration
because of CNS depression.
■
■
Monitor temperature
for prompt detection and
treatment of malignant hyperthermia.
Maintain
dantrolene on standby.
