Induced Moderate Hypothermia After Cardiac Arrest - American ...

MCKEAN
AACN Advanced Critical Care
terminal illness prior to arrest. Patients who
require thrombolytic therapy are not to be
excluded from treatment. 11
BUMC-Induced
Hypothermia Protocol
The AHA recommends cooling these patients
to 32C to 34C for 12 to 24 hours. 1 This facility
uses devices that automatically control the
temperature. The target temperature for
hypothermia is set at 33C and is maintained at
33C for 18 hours once the target temperature
is achieved. If it takes 4 to 5 hours to reach the
target temperature, then the cooling process
will take approximately 23 to 24 hours as recommended
by the AHA. 1 The patient is then
warmed at 0.5C per hour. The target temperature
for warming is set to 36.5C to avoid poor
neurological outcomes associated with temperatures
above 37C. 20
The goal is to begin induction of hypothermia
and achieve target temperature as soon as
possible after ROSC. However, hypothermia
may still be beneficial if induction is delayed
for 4 to 6 hours after ROSC. 5 The physician
should be notified if the target temperature is
not achieved within a reasonable time.
Bernard and colleagues’ goal of achieving the
target temperature was 2 hours. 7 The median
time to target temperature in the study conducted
by Oddo and colleagues 10 was 5 hours. 10
BUMC decided to consider patients for the
hypothermia protocol when it had been less
than 6 hours since the ROSC, with 4 hours as
the goal to achieve the target temperature once
cooling is started.
Shivering should be considered as a possible
reason for not achieving target temperature
within a reasonable time frame. Sedation and/or
paralytic agents should be considered to help
prevent shivering. The nurse should verify that
both are optimized. 13 If the patient is receiving
dialysis, it should be verified that the blood
warmer is switched off. 20 The physician may
also consider infusing iced sodium chloride to
achieve target temperature more rapidly. 16,17
The patient’s temperature should be monitored
continuously during the entire treatment.
Most automatic temperature control modules
require continuous temperature monitoring of
the patient in adjusting the water temperature
to maintain the target temperature. Studies
have not indicated the best method for monitoring
temperatures continuously. Bladder temperature
is the primary method used at BUMC,
because the patients already require a urinary
catheter for strict input and output monitoring.
The equipment was also already available in the
hospital. However, studies have indicated that
bladder temperatures may be inaccurate when
there is decreased urine output. 24 The nursing
staff members have also found that obtaining
temperature readings with the temperaturesensing
urinary catheter is difficult when the
patient is anuric or has decreased urine output.
As a result, the team decided that rectal temperature
monitoring would be used for these
patients.
The literature indicates different intervals for
how often to monitor vital signs including
blood pressure if an arterial catheter is not present.
We decided to check vital signs every 30
minutes, which is within the recommendations
found in the literature. 5,6 Vital signs assessment
is then performed every 15 minutes for 2 hours
during the warming phase due to the increased
risk of hypotension related to vasodilation.
Recommendations for laboratory tests such
as basic metabolic panel, complete blood cell
count, magnesium, ionic calcium, partial thromboplastin
time, prothrombin time, and international
normalized ratio exist for patients
receiving induced hypothermia. 6 A recommendation
for frequency of serial laboratory studies
could not be found. Laboratory test results
should be obtained to determine baseline values
prior to induction of hypothermia. We choose to
perform the laboratory tests listed above at
induction and then every 6 hours through the
course of treatment. This is to allow time for
treatment between laboratory draws if needed.
Once the patient is normothermic, laboratory
assessments are changed to daily for 48 hours.
Potassium replacement should be considered
in the protocol. Potassium is held for 4
hours prior to the start of warming because of
the risk of hyperkalemia as potassium shifts
out of the cell. 6 The physician is contacted during
this time if the potassium is less than
3.4 mEq/L or if arrhythmias are noted. The
potassium replacement protocol is restarted
once the patient is normothermic.
The sedation, analgesic, and paralytic protocols
already used in the ICUs were incorporated
into this protocol. These were used to decrease
confusion and reduce the risk of medication
administration errors because there is familiarity
with these protocols. Questions occurred
with use of the initial protocol regarding when
to stop the paralytic and sedation treatments.
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