• Richmond Agitation Sedation Scale (RASS):
examines cognition
• Sedation Agitation Scale (SAS) and Motor
Activity Assessment Scale (MAAS): monitor
sedation and arousal.
Their use can reduce the amount of sedatives
given to achieve a specific sedation target,
decreasing the number of days on mechanical
ventilation and cost of hospital stay; however,
no validation is available in the neuro-ICU
environment. 2 The Nociception Coma Scale has
emerged as a valid tool to assess pain in patients
with disorders of consciousness. 9
When it is not possible to use these scales,
for example, in patients who require muscular
relaxation, then an electrophysiological endpoint
must be used instead. One example is bispectral
index (BIS) monitoring, 10 which has made
adjustments of sedation possible. A study showed
that BIS values significantly correlated with RASS
and SAS scores in patients with acute brain
injury. 11 In another study, the BIS reliably assessed
sedation levels during continuous propofol
infusion in the same type of patients. 12
BIS was initially developed for monitoring the
depth of general anaesthesia in patients without
brain pathology. It is thought that the ABI (acute
brain injury) may influence the BIS algorithm
because of EEG changes related to the pathology
itself rather than to the sedative state. 1
The approach to sedation should first consider
the severity of acute brain injury and the cerebral
physiological state, mainly ICP. Figure 1 shows
a possible algorithm for the management of
sedation in neurointensive care units. 1
The first things to consider are appropriate
control of pain, control of agitation and
promoting ventilator synchrony. In patients with
intracranial hypertension, the targets for sedation
and analgesia should be titrated to control ICP
and brain tissue oxygen pressure. 1
Need to wake up
For the clinical assessment of neurocritical
patients, interruption of continuous sedation (IS)
is therefore necessary. This is usually short-term,
aimed at evaluating the patients and planning
further management strategies, including the
definitive sedation interruption once the clinical
concern and IS does not provoke patients’ distress
and metabolic imbalance. 2 Withdrawal of
sedation and IS by daily wake-up tests might
appear beneficial to these patients by allowing
clinical neuro-monitoring and timely detection of
warning neurological signs. 13 Daily IS trials have
the potential to reduce mechanical ventilation
duration and the need for tracheostomy. 14 These
potential benefits, however, must be balanced
against the risk of further cerebral
haemodynamic deterioration when sedation is
stopped abruptly. 15 Cerebral hypoperfusion and
raised ICP might result in an imbalance of energy
supply and demand, especially for the injured
brain and, therefore, aggravate the risk for
metabolic distress and brain tissue hypoxia. 16–22
IS might lead to significant ICP elevation and CPP
reduction, which are more relevant in the first
days after ABI than after 4–5 days. 23
Avoidance of IS is recommended in all patients
at risk of, or having, elevated ICP. In these
patients, sedation should never be stopped
abruptly but withdrawn progressively, titrating
the sedation dose to ICP targets. In all other ABI
patients, withdrawal should proceed as in the
general ICU and daily IS in not contraindicated. 1
Given that little knowledge is available about
the benefits of IS in ABI, it is important to
implement multi-modal monitoring in
neurocritical care in order to omit IS in those
patients who will potentially be harmed by the
procedure. 2
Sedative drugs available
The ideal drug for sedation should have a rapid
onset and rapid recovery, in order to evaluate
the neurological state, as well as a predictable
clearance independent of end-organ function
(avoiding accumulation). It should be easy to
achieve adequate levels of sedation and it would
have to reduce ICP by reducing cerebral blood and
cerebral vasoconstriction. As it reduces cerebral
blood flow, it should decrease the metabolic rate
of oxygen consumption at the same time. In
addition, cerebral autoregulation should also be
maintained, while having minimal cardiovascular
depressant effects. 24
The ideal
sedative drug
should be able
to decrease ICP
and maintain
an appropriate
cerebral
perfusion
without
interfering
with its
autoregulation
Propofol
Propofol has a rapid onset and cessation of
sedation. However, it also can unpredictably
accumulate after long-term use and cause
prolonged sedation. 25 Cerebral blood flow and
ICP are decreased. 26–28 Standard- and high-dose
propofol infusion (2mg/kg induction bolus
followed by 150–200mg/kg/min infusion) can be
used as an anticonvulsivant. 29–32 Propofol infusion
syndrome should be detected promptly in order
to start adequate treatment. The hypotension
related to propofol is multifactoral, and severe
propofol-associated hypotension occurred in
26.2% of patients in some studies. 33–36 Weaning
from mechanical ventilation occurs earlier than
with midazolam. 37
Opioids
In general, opioids decrease the cerebral
metabolic rate of oxygen, cerebral blood flow
and ICP, as long as normocapnia is maintained
by mechanical ventilation. 2 However, Roberts et al
found that morphine, fentanyl, sufentanil and
alfentanil significantly increased ICP and decreased
CPP and MAP after bolus administration. 38
Remifentanil
Remifentanil is a mu-opioid agonist with
analgesic effects and a rapid onset and a short
duration of action. It can cause decreases in both
cerebral metabolic rate and ICP, with minimal
changes in CPP and cerebral blood flow. 39 It can
facilitate frequent awakening to evaluate
neurological and respiratory parameters. 40
Benzodiazepines
Use of benzodiazepines increases the incidence of
delirium significantly. Midazolam is an appealing
sedative option for its rapid onset and short
duration of effect with bolus administration,
making it ideal for procedural sedation. It is also
a very important drug in refractory status
epilepticus. Benzodiazepines increase the seizure
threshold and are useful antivonvulsivants. 41,42
Midazolam accumulates in adipose tissue
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