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136 P R I N C I P L E S A N D P R A C T I C E O F C R I T I C A L C A R E

TABLE 7.4 Anxiety drug therapy

Drug group Drug/dose range Action Side effects Comment
Benzodiazepine Diazepam ● Long-acting metabolites 34 ● Most widely used despite being
sedative 5–10 mg bolus ● Hypotension no longer advocated for regular
● Respiratory depression 35 use in critical care 34
Block encoding on GABA ● No analgesia properties 35
Midazolam receptors 33 ● Less likely to have above ● Useful as continuous infusion
0.5–10 mg/h (infusion) side effects 35 ● Rapid onset
1–2 mg (bolus) ● No analgesia properties
● Amnesic effect 35
Sedative hypnotic Propofol General anaesthetic agent ● Hypotension ● Dedicated intravenous line
agent 25–100 µg/kg/min ● Myocardial depression ● Infusions recommended
(infusion) when given as bolus ● High metabolic clearance
● Reported to affect ● Patients wake quickly once drug
memory is ceased 34
● May cause dreams ● Expensive
Non-benzodiazepine Dexmedetomidine Highly selective alpha 2 - ● Initial hypertension may ● Sedative and analgesic 36
sedative 0.2–1 µg/kg/h adrenoceptor agonist 36 be experienced ● Minimal respiratory depression 38
(infusion) ● Bradycardia may persist 37 ● No amnesic effect 39
● Rapid onset 40
● Infusions preferred 40

incorporation of non-pharmacological interventions, voltage electroencephalography pattern present during
pharmacological treatment with relevant agents may delirium in which slow wave activity is evident even
be initiated. Table 7.4 gives a brief overview of these during wakefulness. 54
medications in the treatment of unrelieved anxiety.
Lethargy, slow quiet speech and reduced alertness are
52
typical behaviours of hypoactive delirium. It is hypo-
DELIRIUM thesised that clinicians may not recognise the ‘quietly’
55
confused patient so the condition may be untreated
Delirium is a significant concern for critically ill patients 56
41
and the clinicians who care for them. It is a category or misdiagnosed as depression. Behaviours evident in
52
42
of central nervous dysfunction where behaviours and hyperactive delirium such as hyperactivity and agitation
physiological responses are not conducive to healing cannot go unnoticed by clinicians and present overt
and recovery. Early detection and treatment of delirium risks of self harm such as unintentional extubation/
is vital, as it is associated with adverse clinical outcomes decannulation and intravenous/arterial device removal.
such as prolonged duration of ventilation, length of Combined delirium is characterised by fluctuations in
ICU and hospital stay and higher rates of morbidity activity and attention levels including the behaviours of
52
and mortality. 43-48 Furthermore increased duration of both hyperactive and hypoactive subtypes.
delirium has been associated with long-term cognitive Reports in the healthcare literature about the prevalence
49
impairment. Arguably the condition has been under- of delirium in ICU vary widely from 15–70%; 57,58 an
50
recognised and under-treated and has only recently unsurprising finding given that it is notoriously difficult
received the attention it deserves. 46,51 Under-recognition to diagnose in patients who are unable to communicate
59
is probably related to a number of factors including the verbally. Rates of delirium in Australian and New
high incidence of the hypoactive subtype as well as lack Zealand ICUs have fallen within this range, with 45% of
of use of formal screening instruments (without which the patients who were in the ICU for longer than 36 hours
exists a high degree of subjectivity when assessing reported to have delirium, while 21% of 56 patients in
60
61
delirium). a smaller study had delirium. The prevalence in other
critical care areas such as emergency departments is
There are three subtypes of delirium: hypoactive, hyper- 62
52
active or combined (a combination of both). A sudden thought to be lower.
reversible reduction in cognitive ability (e.g. inattention, The exact pathophysiology of delirium is not yet fully
reduced problem-solving ability and disorientation) and understood, however, imbalances in brain cholinergic
onset of perceptual disturbances (e.g. hallucinations) and dopaminergic neurotransmitter systems are thought
over hours or days are characteristic of all subtypes of to be responsible. Many predisposing and precipitating
42
delirium. This is in contrast to dementia in which cogni- risk factors have been identified and current opinion sug-
tive decline occurs over months and years. Cognitive and gests that there is an additive effect; patients with more
perceptive ability often fluctuates through the day wors- than one predisposing factor will require less noxious
ening at night. Sleep–wake cycle disturbance is also a precipitating factors to develop delirium than patients
feature of delirium. In addition there is a unique low who have none. Predisposing factors include:
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