POST-CARDIAC ARREST HYPOTHERMIA PROTOCOL FOR
CRITICAL CARE PATIENTS AT WALTER REED NATIONAL
MILITARY MEDICAL CENTER
SUBJECT: Poor neurological outcome is common after cardiac arrest. Experimental
and animal studies indicate that therapeutic hypothermia may inhibit many of the
damaging chemical reactions that follow cerebral anoxia. Multiple studies have
demonstrated improved neurological outcomes with the use of induced, mild
hypothermia following out-of-hospital cardiac arrest from ventricular fibrillation. Further
data suggests other patients with cardiac arrest, such as in-hospital asystolic or PEA
arrests, may also derive benefit from induction of mild hypothermia.
REFERENCES:
1. Nolan JP, et al. Therapeutic Hypothermia After Cardiac Arrest.
ILCOR Advisory Statement. Circulation 2003; 108: 118-121.
2. 2005 American Heart Association Guidelines for CPR and Emergency
Cardiovascular Care.
3. Bernard SA, et al. Treatment of comatose survivors of out-of-hospital
cardiac arrest with induced hypothermia. NEJM 2002; 346: 557-563.
4. The Hypothermia After Cardiac Arrest Study Group. Mild therapeutic
hypothermia to improve the neurologic outcome after cardiac arrest.
NEJM 2002; 346: 549-556.
5. Cheung, KW, et al. Systematic review of randomized controlled trials
of therapeutic hypothermia as a neuroprotectant in post cardiac arrest
patients. CJEM 2006; 8: 329-337.
6. Polderman, KH. Application of therapeutic hypothermia in the ICU:
opportunities and pitfalls of a promising treatment modality. Part I:
Indications and evidence. Intensive Care Med 2004;30:556-575
7. Polderman, KH. Application of therapeutic hypothermia in the ICU:
opportunities and pitfalls of a promising treatment modality. Part 2:
Practical aspects and side effects. Intensive Care Med 2004;30:757769
PURPOSE: This SOP outlines the criteria for appropriate selection of patients for
mild therapeutic hypothermia and the procedure for induction of mild therapeutic
hypothermia. By following this protocol, appropriate patients will be selected for therapy
and achieve the target temperature for therapeutic hypothermia. Therefore, the number of
patients with good neurological outcome following cardiac arrest should increase.
SCOPE: This SOP applies to all physicians and nurses working with comatose
patients with return of spontaneous circulation following cardiac arrest in the critical care
units of Walter Reed National Military Medical Center.
INDICATIONS:
1. Patients with cardiac arrest and return of spontaneous circulation who
remain comatose, particularly if initial rhythm was ventricular
fibrillation. For purposes of this protocol, comatose is defined as GCS
< 9 (either does not follow commands OR does not open eyes to pain)
immediately after ROSC.
2. Patients with cardiac arrest of other etiologies should be considered on
a case by case basis.
3. Hemodynamic stability with MAP > 60. Use of vasoactive medication
is acceptable.
4. Known time of cardiac arrest.
CONTRAINDICATIONS:
1.
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5.
6.
7.
8.
Hemodynamic instability (SBP < 90) despite vasoactive medications
Coma of other etiology (ie drug overdose)
Clinically significant bleeding
Pregnancy
Hypoxemia (O2 sat < 85%) despite maximal ventilatory support
Known terminal illness
Thrombocytopenia with platelet count < 30k, until corrected.
Major head trauma or irreversible neurologic injury
PROCEDURE:
1. Target temperature is 32-34 degrees Celsius. Temperature should be
measured continuously by bladder, esophageal, or rectal probes.
Temperatures obtained from a pulmonary artery catheter are also
acceptable. Typmpanic membrane temperatures are inaccurate in
hypothermia and should be avoided.
2. Initial evaluation should include EKG, CXR, CMP, CBC, Coags, abg,
and for females < 60 hcg.
3. The goal of cooling should be to obtain the target temperature within 4
hours of ROSC. Cooling should not be delayed for other
diagnositic/therapeutic interventions.
4. Cooling should be initiated as soon as possible after ROSC, however
patients cooled up to 6 hours after ROSC may still benefit.
5. Therapeutic hypothermia with temperature 32-34 deg C should be
continued for 12-24 hours.
6. Acceptable methods of cooling include:
a. Commercially available cooling devices (vests and blankets), ie
Artic Sun. Intravascular cooling catheters are also
commercially available and considered acceptable, but are not
currently available at Walter Reed National Military Medical
Center.
b. Ice packs applied to the head, neck, axilla, torso and groin. If
ice packs are used, they should be removed once target
temperature is obtained, and replaced as needed to maintain
target temperature.
c. Decrease temperature of room
d. Use of HME instead of heated humidifier on ventilator
e. Patients should be adequately sedated per the Walter Reed
National Military Medical Center sedation protocol. Primary
agents are midazolam, propofol, and fentanyl.
7. Shivering is associated with increased metabolic demand and must be
avoided.
a. Shivering is most profound during induction of hypothermia.
Deeper sedation may be required during this time period to
prevent shivering. Rapid cooling will minimize shivering
during induction.
b. Shivering can be mild (localized to the neck and/or thorax, may
be palpable only, may visualize on ECG), moderate (involves
gross movement of extremities), or severe (gross movement of
trunk, upper and lower extremities
c. Warming of distal extremities (hands and feet only) may be
effective in preventing shivering. Use of heat packs, blankets,
or “bear hugger” (to hands and feet only) are acceptable.
d. Meperidine 50-100 mg iv bolus then 12.5 to 50 mg/hr may
prevent shivering. Avoid meperidine in renal failure or with
documented seizure.
e. Neuromuscular blockers (ie vecuronium 0.1 mg/kg, then 1
microgram/kg/min titrated to train of fours per protocol) should
be used as needed to prevent shivering. Sedation is required
with the use of neuromuscular blockade.
8. Other complications of cooling.
a. Hypotension
i. Ensure adequate volume status and utilize vasopressors
as indicated
ii. Diuresis may occur with hypothermia
b. Hyperglycemia. Blood glucose should be monitored q6 hrs,
with goal blood glucose < 150.
c. Electrolyte abnormalities
i. Monitor electrolytes q 4 hrs. Goal serum K is 3.5 to
4.0. Avoid over-aggressive repletion as rebound
hyperkalemia is common during rewarming. Stop
infusions during rewarming.
ii. Replace phos and Mg per routine.
d. Arrythmias
e. Coagulopathy. Discontinue cooling for clinically significant
bleeding.
f. Immunosuprression. Aggressive monitoring for infection is
indicated.
9. Rewarming. After the determined period of therapeutic hypothermia
(24 hrs), the patient should be allowed to passively return to
normothermia. Rate of rewarming should not exceed 0.3 deg C per
hour.
a. Turn off artic sun device.
b. Return room temperature to normal
c. Resume use of heated humidifier on ventilator, if applicable.
d. Discontinue electrolyte drips.
e. Regular blankets may be used. Heating blankets should be
avoided unless temperature is <36 degrees after 12 hours of
passive rewarming. Avoid rebound hyperthermia.
f. Ensure adequate volume status as rewarming will cause
vasodilation.
g. If using neuromuscular blockers, stop when Temp reaches 36
deg Celsius.
h. Complications of rewarming include hyperkalemia,
hypoglycemia, hypotension, shivering.
10. Protocol discontinuation. Certain clinical circumstances reflect
severe neurologic devastation following cardiac arrest and may be
difficult to recognize during resuscitation and induction of therapeutic
hypothermia. If present, consider discontinuation of this protocol and
consider withdrawal of life support or limiting further interventions.
a. Myoclonus
b. Refractory hypotension in the setting of rising vasopressor
requirements and stress dose steroids
c. Recurrent cardiac arrest
Protocol reviewed and accepted by members of the protocol committee.
Robert Browning, MD
CDR, MC, USN
Chief, Department of Critical Care
WRNMMC
Jessica Bunin, MD
MAJ, MC, USA
Chair, Protocol Committee
Induced Hypothermia After Cardiac Arrest
Supplemental Data
Algorithm 1: Criteria, Cautions, and Preparation
Rationale: Use of hypothermia treatment in patients following cardiac arrest lessens the
chance of ischemic brain damage and leads to improved neurological outcomes at 6
months.
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GOALS / TIMELINE
Initiate hypothermia within 6 hours of cardiac arrest.
Sustain hypothermia for 24 hours from time of initiation of cooling to a body
temperature of 32-34° C(89.6-93.2° F)
After 24 hours of cooling, begin rewarming at a rate of 0.3–0.5° C (0.5–0.9° F)
every hour up to a target of 36° C (96.8° F)
Criteria for Induced Hypothermia
Cardiac arrest out of hospital, with initial arrest heart rhythm of ventricular
fibrillation or pulseless ventricular tachycardia.
Cardiac arrest within past 6 hours.
Patient intubated with mechanical ventilation.
Presence of spontaneous circulation, with or without vasopressor agent use.
Coma at time of cooling (coma defined here as no purposeful movement to
verbal command).
- Brainstem reflexes and pathological posturing movements permissible.
- Patients with Glasgow Coma Scale (GCS) <9 are eligible
Cautions
Use caution in patients with these conditions:
 Intracranial hemorrhage.
 Major surgery within 14 days.
 Systemic infection / sepsis.
 Known bleeding diathesis or active ongoing bleeding.
 Temperature less than 30 C after cardiac arrest
Preparation
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Avoid initial rewarming.
- Do not actively warm patients who are spontaneously hypothermic following
cardiac arrest.
 Continue other therapies as indicated.
 Begin treatment early.
- Confirm eligibility and gather materials.
- Start cooling as early as possible for maximum effectiveness.
- Initiate therapy in the ED when possible.
- Continue treatment in the cath lab or ICU.
 Monitor temperature to prevent “overcooling.”
- Continuous Temperature Monitoring: Use an esophageal or bladder
temperature probe or pulmonary artery temperature probe.
- Secondary Temperature Monitoring: Use a secondary temperature device as
a safety monitor. Use routine techniques in ICU every 30 minutes during
cooling and rewarming, and every hour during maintenance.
Algorithm 2: Cooling Methods
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Provide Continuous Sedation
Maintain continuous medication infusion for patient’s comfort and sedation.
(Follow ICU Guidelines)
Prevent Shivering
 Sedate the patient during the cooling phase. Consider paralytics if necessary.
(Follow interventions for shivering on protocol)
- The train-of four method of monitoring neuromuscular blockade is unreliable
when the patient is hypothermic, and it is not recommended.
- Discontinue paralytic agent infusion once temperature is less than 34º C
(93.2º F). If shivering occurs, resume neuromuscular blockade.)
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Consider Cold Fluids
Consider cold saline infusion via a peripheral line or femoral venous
catheter to assist in achieving goal temperature. (Cold saline is stored in the
emergency department.)
- The infusion is 30 ml/kg of 4º C (39.2° F) normal saline over 30 minutes (2 L
for a normal-size adult).
- Do NOT give cold fluids if there is clinical evidence of CHF or CVP greater
than 20.
- DO NOT give cold fluid via a jugular or subclavian line.
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Provide External Cooling with Arctic Sun and Ice
Obtain Ice packs
Obtain ArcticGel Pads, cables, and one Arctic Sun machine to envelope the
patient.
Prior to using/setting up electronic cooling device, pack patient in ice (groin,
chest, axillae, side of neck) to bring temperature between 32-34º C (89.6-93.2º F).
Avoid packing ice on top of the chest, as this may impair chest-wall motion.
Once temperature is less than 34º C (93.2º F) and cooling device is ready for use,
remove ice bags to prevent excessive drop in patient’s core temperature.
Arctic Sun is the electronic external cooling device used at WRAMC
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Monitor Arterial Pressure
Ensure an arterial line is placed for arterial pressure monitoring.
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Algorithm 3: Supportive Therapy and Controlled Rewarming
Supportive Therapy
To optimize cerebral perfusion, a mean arterial pressure (MAP) goal of 80-100
mm Hg is preferred.
- If MAP less than 80 mm Hg, norepinephrine may be used beginning at 0.1
mcg/kg/min to titrate MAP above 80 mm Hg.
- Determine MAP goal by balancing the cardiac safety with the theoretical
advantage of higher cerebral perfusion pressure.
- Because of peripheral vasoconstriction, BP often remains elevated during
hypothermia.
- Hypotension (MAP less than 80 mm Hg) from vasodilation is a concern during
warming phase.
Monitor patient for arrhythmia associated with hypothermia. If persistent, lifethreatening dysrhythmias, hemodynamic instability, or bleeding develop,
discontinue cooling, and ensure that the patient is actively re-warmed.
- Heart rates less than 40 are frequent and are not alone a cause for concern in the
absence of other evidence of hemodynamic instability.
Obtain Chem 7 and blood gas at time 0. Obtain glucose, K+, and blood gas at
hours 6, 12, 18, and 24.
Treat potassium values less than 4.0 mEq/L with IV or nasogastric
administration of K+ while the patient is being cooled. Stop potassium
administration once rewarming begins.
Hyperglycemia (> 150) should be avoided. Treat with insulin if elevated. (See
IV Insulin Protocols.)
Maintain PCO2 in the normal range (35-45 mm Hg).
Check skin every two hours for injury caused by ice or cold blankets.
Do not provide enteral nutrition during the initiation, maintenance, or rewarming phases of therapy.
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Controlled Rewarming
Begin rewarming 24 hours after initiating cooling.
Rewarm at a rate of 0.3–0.5º C (0.5-0.9° F) every hour.
Most patients require about eight hours to rewarm.
The goal after rewarming is normothermia.
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Medications During Rewarming
Maintain sedation until a temperature of 35° C (95° F) is reached.
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- If a neuromuscular blocking agent is infusing solely to prevent shivering,
discontinue the neuromuscular blocking agent before the sedative/analgesic
agents.
- Do not discontinue the sedative/analgesic until the
patient is moving or until the neuromuscular blocking
agent has been discontinued for at least 3 to 5
half lives of the paralytic.
Monitor patient for hypotension (secondary to vasodilatation)
induced by rewarming.
Discontinue potassium infusions.
Acetaminophen and external cooling p.r.n. to keep
temperature less than 37.5° C (99.5° F) for 48 hours after
admission
Rewarming with the Arctic Sun Device
The goal is to have the patient warm at about 0.3° C
(0.5° F) per hour, up to a target of 36°C (96.8° F).
Increase water temp by 0.5°C (0.9° F) every 1 to 2
hours.
Remove the Arctic Sun Gel pads and blankets after a stable
temperature of 36°C (96.8° F) for 1 hour has been
reached.
Order Set: