Induced Moderate Hypothermia After Cardiac Arrest - American ...

MCKEAN
AACN Advanced Critical Care
is beneficial only if the health care team knows
how to care for this patient population. Nursing
care and support is crucial. Patient management
and the vital nursing care needed for this
patient population are described below.
Table 1: The Bedside Shivering
Assessment Scale a
Score
Definition
0 None: no shivering noted on palpation of
the masseter, neck, or chest wall
1 Mild: shivering localized to the neck
and/or thorax only
2 Moderate: shivering involves gross
movement of the upper extremities (in
addition to neck and thorax)
3 Severe: shivering involves gross
movements of the trunk and upper and
lower extremities
a Used with permission from Badjatia et al, “Metabolic Impact of
Shivering During Therapeutic Temperature Modulation: The Bedside
Shivering Assessment Scale,” Stroke, 2008, vol. 39, pp. 3242--3247. 21
Prevention of Shivering
Shivering is a natural body response to
hypothermia. If this natural response is allowed
to occur while inducing hypothermia, there
may be difficulty in achieving the target temperature.
Shivering increases metabolic rate and
oxygen consumption. Most protocols use a
combination of sedation and paralytic agents to
prevent shivering especially during induction. 20
Shivering is less likely to occur during the maintenance
and warming phases. The paralytic
may be stopped during the warming phase. 13,20
Patients should be monitored for signs and
symptoms of shivering, including a drop in
mixed venous oxygen saturation, increase in
respiratory rate, facial tensing, static tracing
on the electrocardiogram, and palpation of
muscle fasciculations on the face or chest. 13
The Bedside Shivering Assessment Scale (Table 1)
may be used by nurses to provide a universal
assessment tool for shivering. 21 The nurse must
ensure that analgesia and sedation are optimized
and that the patient is intubated with
the ventilator set to proper parameters to provide
adequate ventilation prior to the start of
the paralytic treatment. A train of 4 should be
established prior to initiation of continuous
paralytics and continued to be monitored for a
goal of 1 out 4. 13,20 It may be difficult to obtain
train of 4 assessments due to peripheral vasoconstriction
during hypothermia. 13 The nurse
might need to rely on clinical indicators such
as overbreathing on the ventilator and spontaneous
movement to know if the paralytic
agent is optimized.
Sedation and analgesic drugs, such as midazolam,
fentanyl, and propofol, have a 30% to
50% decrease in systemic clearance during
hypothermia. For neuromuscular-blocking
agents, such as vecuronium and atracurium,
clearance is decreased 10% for every 1C
below 37C. Their duration of action is also
increased. 20 The least amount of drug should
be used to provide the needed effect. During
hypothermia, the amount of drug required
may be less than what is typically used. 13 The
health care team must be mindful that the
patient may take longer to wake up after treatment.
20 The paralytic and sedation medications
should be stopped as soon as possible
after the completion of induced hypothermia
treatment.
Vital Sign Monitoring
A patient’s normal response to hypothermia is
to increase the heart rate and vasoconstrict in
an attempt to conserve heat. The use of sedation
and paralytic agents prevents this normal
response to hypothermia. Bradycardia and
increased systemic vascular resistance will be
seen in the absence of shivering and with a continued
decrease in temperature. The bradycardia
is usually not hemodynamically significant
and usually refractory to atropine. It is not
always necessary to terminate treatment for
patients who are bradycardic. Blood pressure is
usually maintained without the use of vasopressors
secondary to the increased systemic vascular
resistance. Vasopressors may be used to
maintain systolic blood pressure greater than
90 mm Hg or mean arterial pressure greater
than 60 mm Hg. The patient may be pale, and
peripheral pulses may be difficult to obtain
because of the vasoconstriction. The greatest
risk for hypotension is during the warming
phase secondary to vasodilation. It is critical at
the start of warming that vital signs are monitored
closely. 2,5,20 Ideally, an arterial catheter will
be inserted for continuous blood pressure measurement.
However, if one is not available, then
noninvasive measurements should be obtained
at least every 30 minutes and more often during
induction of warming. 6,20
Continuous electrocardiogram monitoring
is imperative. Dysrhythmias are rare in mild
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