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Induced Hypothermia. How EMS can improve the long term outcomes for resuscitated patients. Wake EMS Induced Hypothermia Team. J. Brent Myers, MD, MPH Medical Director Paul R. Hinchey, MD, MBA, EMT-P Assistant Medical Director Joseph Zalkin, EMT-P Assistant Chief Professional Development

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induced hypothermia

Induced Hypothermia

How EMS can improve the long term outcomes for resuscitated patients

wake ems induced hypothermia team
Wake EMS Induced Hypothermia Team

J. Brent Myers, MD, MPH

Medical Director

Paul R. Hinchey, MD, MBA, EMT-P

Assistant Medical Director

Joseph Zalkin, EMT-P

Assistant Chief Professional Development

Jon Olson, MBA, MHA, EMT-P

District Chief Operations

Ryan Lewis, EMT-P

District Chief Quality Assurance

Donald Garner, EMT-P

District Chief Training

induced hypothermia ih
Induced Hypothermia(IH)
  • What is Induced Hypothermia?
  • Why IH at Wake EMS?
  • How does it work?
  • When is it indicated?
  • How will it be applied?
what is hypothermia
What is Hypothermia?

Mild Hypothermia

89.6-95°F (32-35°C)

Moderate hypothermia

82.4-89.5°F (28-32°C)

Severe Hypothermia


what is induced hypothermia
What is Induced Hypothermia?

Active cooling of the body to below normal levels

so why would you intentionally induce hypothermia
So why would you intentionally induce hypothermia?

……a little history will help…..

In March of 2005, nine months prior to the November 2005 release of the AHA resuscitation guidelines, Wake County EMS System implemented new CPR protocols using the latest in resuscitation techniques and available technology.
the technique
The Technique
  • Changed CPR:
    • Emphasis on effective uninterrupted compression
    • Decreased emphasis on importance of ventilation
    • Slower ventilatory rates
the technology
The Technology
  • Use of ETCO2:
    • As confirmation of ETT placement
    • Goal directed respiratory rate
the technology10
The Technology
  • EZ IO drill:
    • Rapid IV access if initial IV attempt fails
dramatic improvement
Dramatic Improvement?
  • Impact on Pre-hospital ROSC1
    • From 22% to 37% of all cardiac arrests
    • From 38% to 45% of v-fib arrests
    • From 40% to 53% of witnessed v-fib arrests
  • Impact on discharge from hospital1
    • From 10% to 12%

Not really what we expected…

so why the disparity
So why the disparity?
  • Post Resuscitation Deaths3
    • Refractory dysrhythmias (10%)
    • Low cardiac output states (30%)
    • Post Resuscitation Encephalopathy (40%)
Post Resuscitation Encephalopathy (PRE) is the single largest contributor to post resuscitation deaths and poor neurologic outcomes.

PRE is caused by a series of events that begin immediately following reperfusion of the brain with ROSC………

  • Initial hypoperfusion insult followed by period of hyperperfusion with ROSC3
  • Cell injury8,11
    • Oxygen free radical formation
    • Inflammatory cascade
    • Glutamate mediated cell death
  • Loss of Autoregulation3,8,11
    • Patchy intracerebral vasoconstriction
    • Intravascular sludging and hypoperfusion
    • Perfusion/demand mismatch

Luxuriant Hyperperfusion


Unregulated blood flow leads to oxygen free radical formation and cell injury. It triggers inflammation, glutamatemediated cell death and edema.

Initial restoration of blood flow results in unregulated perfusion of the brain. This period is referred to as the luxuriant hyperperfusion period and can last from 10-30 minutes.

Vasoconstriction leads to supply demand mismatch which leads to hypoperfusion and cell damage which perpetuates the inflamatory response.

The post resuscitation brain develops diffuse, patchy vasoconstriction and intravascular sludging.

Supply Demand Mismatch

Inflammatory Response

Loss of Autoregulation

factors in pre
Factors in PRE
  • Inflammation and Edema
  • Vasoconstriction and Sludging
  • Supply Demand Mismatch
optimizing neurologic resuscitation
Optimizing Neurologic Resuscitation

Mild Induced Hypothermia (IH)

  • Inhibits inflammatory cascade12,14,15
  • IH is time sensitive8,11,14,15
    • Animal studies demonstrate time dependent benefit
  • Decrease metabolic demand4,5,6,7
    • 5-7% decrease in metabolic demand for each degree Celsius
optimizing neurologic resuscitation23
Optimizing Neurologic Resuscitation

Hypertensive reperfusion12,13,14,15

  • Forced perfusion despite vasoconstriction
  • Vasopressors to target MAP of 90-100mmHg


  • Normal saline dilution as part of hypertensive reperfusion strategy
  • Reduces vascular sludging
  • Cold saline as a rapid cooling technique
summary of studies
Summary of Studies


50% vs 14%


23% vs 7%


50% vs 23%


54% vs 33%


49% vs 26%


55% vs 39%


48% vs 32%


59% vs 45%

metaanalysis 21
  • Short-term Benefit Ratio
    • 1.68;95% CI 1.29-2.07
  • 6 Month Benefit Ratio
    • 1.44 95% CI 1.11-1.76
  • Number needed to treat (NNT)
    • 6 patients CI (4-13)
some familiar nnt
Some familiar NNT

The analysis of the studies and the limited side effect profile led to several organizations making recommendations on post resuscitation hypothermia

Cath capable facility versus thrombolytics

Aspirin therapy for MI

Beta Blocker therapy for MI




ilcor advisory statement
ILCOR Advisory Statement
  • Unconscious adult patients with ROSC after out-of-hospital VF cardiac arrest should be cooled to 32°C - 34°C for 12 - 24 hrs.
  • Possible benefit for other rhythms or in-hospital cardiac arrest
aha statement
Aha statement

Post Resuscitation Treatment

  • Induced hypothermia
  • Prevention of hyperthermia
  • Tight glucose control
  • Prevent hypocapnia
  • Maintain elevated MAP

As part of the effort to reduce the disparity between our resuscitation rates and hospital discharge rates, Wake County EMS System began looking at the use of induced hypothermia in August of 2005.

First we had to look at the effects of hypothermia…..

effects of ih
Effects of IH
  • Holzer &Bernard4,21
    • No statistically significant difference in complication rates in normothermic and hypothermic cohorts
  • Potassium shifts
    • Intracellular shift with induction
    • Extracellular shift with warming
    • Managed with replacement and gradual rewarming
  • Fluid status
    • Cooling causes diuresis
    • Warming causes hypovolemia
    • Requires careful monitoring of urine output and fluid status
effects of ih33
Effects of IH
  • Respiratory Alkalosis
    • Temperature corrected ABG allows changes in minute ventilation to support normal PaCO2
  • Hyperglycemia
    • HACA group and Bernard found that high blood glucose after cardiac arrest is associated with poor neurologic outcomes but did not find any improvement with tight glucose controls. 4,5
complications of ih in other applications
Complications of IH in Other Applications
  • Neutropenia
    • Neutropenia and increased incidence of pneumonia seen in patients exposed to prolonged hypothermia (>24hrs) in other applications
  • Coagulopathy18,19,20
    • May alter clotting cascade, platelet function
  • Cardiac dysrhythmias
    • Little risk for clinically significant dysrhythmias if temperatures are maintained >30°C17
After finding limited side effects we developed a comprehensive protocol from field implementation to hospital discharge.
wake county plan
Wake County Plan

Objective is cost effective, prehospital initiation of induced hypothermia in patients with ROSC.

wake county plan38
Wake County Plan

Criteria for Induced Hypothermia

Return of Spontaneous Circulation

Remains Comatose

Confirmed Intubation

wake county plan39
Wake County Plan

Criteria for Induced Hypothermia

Return of Spontaneous Circulation

  • Palpable Pulses
  • Auscultatable Blood Pressure
  • Non-Traumatic Event
wake county plan40
Wake County Plan

Criteria for Induced Hypothermia

Return of Spontaneous Circulation

Remains Comatose

  • No purposeful movements
wake county plan41
Wake County Plan

Criteria for Induced Hypothermia

Return of Spontaneous Circulation

Remains Comatose

Confirmed Intubation

  • Auscultated Breath Sounds
  • Tube Check Device
  • ETCO2 Reading
wake county plan42
Wake County Plan

Criteria for Induced Hypothermia

Return of Spontaneous Circulation

Remains Comatose

Confirmed Intubation

wake county plan43
Wake County Plan

Protocol for Induced Hypothermia

Expose the Patient

wake county plan44
Wake County Plan

Protocol for Induced Hypothermia

Slowly administer Versed 0.15mg/kg up to 10mg

wake county plan45
Wake County Plan

Protocol for Induced Hypothermia

Administer Vecuronium 0.1mg/kg to max of 10mg

wake county plan46
Wake County Plan

Protocol for Induced Hypothermia

Apply Ice Packs




wake county plan47
Wake County Plan

Protocol for Induced Hypothermia

Cold Saline Infusion


to max of 2 Liters

wake county plan48
Wake County Plan

Protocol for Induced Hypothermia

Administer Dopamine 10-20 mcg/kg/min

Attain a MAP of 90-100

wake county plan49
Wake County Plan

Pearls of Induced Hypothermia

  • Be mindful when exposing the patient
  • Do not delay transport to cool
  • Constantly reassess airway patency
  • Do not hyperventilate the patient
  • If loss of ROSC, discontinue cooling and treat per appropriate protocol
protocol review

NOTE: If the patient does not meet criteria for IH or if the patient can not be intubated with an endotracheal tube, a LMA is placed and the patient is managed by standard post-resuscitation protocols.

Protocol Review
  • Arrest not due to hemorrhage or trauma
  • Age > 16
  • Remains comatose with no purposeful response to pain
  • Patient is intubated


Initial tympanic temperature criteria is used to avoid potential overshoot of the target range



Criteria for Induced Hypothermia

and Initial Temp of >34C


ETCO2 > 20mmHg is used both to confirm tube placement and as an additional measure of successful ROSC. It is unlikely that an appropriately ventilated patient with ROSC will have an ETCO2 < 20mmHg.


Neuro exam consists of basic evaluation of pupil response and motor response to pain



ET Tube Placed and

ETCO2 >20mmHg




Perform Neuro Exam and Document

Start Hypothermia Procedure

protocol review51
Protocol Review

Perform Neuro Exam and Document

Start Hypothermia Procedure

Vecuronium is used as a long acting paralytic to prevent shivering. It is NOT used to facilitate intubation. If the patient can not be intubated they are excluded from pre-hospital hypothermia therapy.

Versed is used as a sedative in conjunction with the paralytic.

Expose patient

Apply Ice Packs to Axilla and Groin

Versed 0.15mg/kg up to 10mg max dose

Chemical ice packs are used for external cooling. Misting or wetting the patient can be used in conjunction with ice packs to expedite the cooling process.

Vecuronium 0.1mg/kg up to 10mg max dose

protocol review52
Protocol Review

Cold Saline Bolus 30ml/kg up to 2 Liters

Dopamine 10-20mcg/kg/min to achieve

MAP of 90 to 100

Cold saline (2-4°C) is infused as part of the internal cooling process. While this may seem like a large fluid bolus studies have shown that the core temperature can be reduced 1-2°Cwithout adverse side effects from the fluid. This fluid volume is also necessary for the hypertensive reperfusion component of the therapy and to compensate for the diuresis that occurs with cooling.

Dopamine is used as needed to maintain mean arterial pressures (MAP) sufficient to perfuse the brain. Fortunately most new monitors calculate the MAP for you.

(MAP = DBP + 1/3[SBP – DBP])

seem like a lot to remember
Seem like a lot to remember?

So Ryan Lewis created checklists to reduce errors and expedite initiation…

We thought so…

managing cold saline
Managing Cold Saline

Keeping it cold enough to be effective

managing cold saline57
Managing Cold Saline

36-39°F (2-4 °C)

is the target temperature

The big question was...

…how to keep it there?

managing cold saline58
Managing Cold Saline

Model 15 Freezer

14qt Capacity

27 pounds

0 – 40 Degrees Fahrenheit

3.9 Amp Draw on 12V System

Fits neatly in floorboard of SUV

Approx $400 retail

managing cold saline59
Managing Cold Saline

which respond to all cardiac arrests

Initial Deployment on EMS District Chief Vehicles

managing cold saline60
Managing Cold Saline

Reduces initial start up costs

Initial Deployment on EMS District Chief Vehicles

managing cold saline61
Managing Cold Saline
  • Maintaining stock in refrigerator in Station at 45 degrees
  • 6 Liters in 12V freezer units on select response units
  • Add 12V freezers to all system ambulances as budget permits
maintaining hypothermia

…once at the hospital

Maintaining Hypothermia

Thermal regulationwith an endovascular cooling device

reduces workload and maintains tight temperature control.

endovascular device
Endovascular Device

Placed directly into the Inferior Vena Cava

Circulates temperature controlled saline through the catheter module

Monitors temperature to within 0.1-0.3 C of pulmonary artery temp

Used for both cooling and rewarming

is this research
Is this Research?
  • Current AHA resuscitation guidelines are based on prospective randomized trials
  • We felt it was unethical to conduct a randomized trial with a treatment that is now recommended care
  • Current Wake EMS IH protocol represents a change in therapy to meet the new standard of care.
future research
Future Research?
  • Will evaluate efficacy with historical case control based on prior resuscitation and discharge rates.
  • Currently there is no data on pre-hospital application of IH therapy:
    • Evaluate effectiveness of saline induced cooling process
    • Evaluate prehospital application
How do you track patient outcomes from pre-hospital care through to discharge without losing them in follow-up?
ems banding system
EMS Banding System
  • Developed by Joseph Zalkin the system provides unique EMS ID #
  • ID is scanned into EMS electronic call report AND hospital electronic chart
  • Provides unique tracking number throughout admission to discharge
what other steps are we taking to improve survival
What other steps are we taking to improve survival?
  • Introduction of endotracheal introducer (Bougie)
  • Res-Q-Pod
why do we do all this
Why do we do all this?
  • EMS is unique medical practice environment whose impact extends beyond arrival at the ED doors
  • In cardiac arrest our goal is discharge to home
  • Less than 50% of ROSC are sent home
  • Hospitals currently utilizing IH
  • IH improves long term outcome
  • IH is time dependent
  • IH is cost effective
  • EMS drives hospital implementation
  • IH is part of multifaceted AHA recommended strategy to improve neurologic outcomes in CA
  • It requires limited training, minimal cost of implementation and has few significant complications
  • IH is ideally suited to EMS because it:
    • Impacts outcomes
    • Is time sensitive
    • Is cost effective

109 out of hospital cardiac arrest from all rhythms

  • Retrospective study using historical controls
  • 55 induced hypothermia and 54 controls
  • Hypothermia to 33deg C with external device for 24 hrs
  • Patients treated with versed, fentanyl and vecuronium
  • MAP were maintained 90-100mmHg

Survey of 2,248 physicians in UK, US and Finland

  • Emergency, Cardiology, and Critical Care Physicians
  • 74% of US and 64% of Non-US never used hypothermia
  • 16% of US ED physicians and 34% of US Intensivists
  • Reasons cited
    • Not enough data
    • Not a part of ACLS guidelines
    • Too technically difficult to use
  • Wake County EMS Database
  • Edgren, E et al Assessment of neurological prognosis of comatose survivors of cardiac arrest. Lancet 1994; 343:1055-59.
  • Myerburg, R et al. Clinical, electrophysiologic and hemodynamic profile of patients resuscitated from prehospital cardiac arrest. Am J Med. 1980; 68:568-76.
  • Hypothermia After Cardiac Arrest (HACA) Study Group. Mild therapeutic hypothermia to improve the neurologic outcome after cardiac arrest. N Engl J Med. 2002; 346:549-56.
  • Bernard, SA et al. Treatment of comatose survivors of out of hospital cardiac arrest with induced hypothermia. N Engl J Med. 2002; 346:557-63.
  • Yanagawa, Y, et al. Preliminary clinical outcome study of mild resuscitative hypothermia after out of hospital cardiopulmonary arrest. Resuscitation 1998; 36:61-66.
  • Bernard, SA, et al. Clinical trial of induced hypothermia in comatose survivors of out of hospital cardiac arrest. Ann Emerg Med. 1997;30:146-53.
  • Persse, DE et al. Managing the post-resuscitation patient in the field. PEC 2002;6:114-22.
  • Part 7.5: Postresuscitation Support. Circulation 2005;112:84-88.
  • Kollmar, R. Early effects of acid-base management during hypothermia on cerebral infarct volume, edema, and cerebral blood flow in acure focal cerebral ischemia in rats. Anesthesiology 2002;97:868-74.
  • Persse, D. Et al. Managing the post resuscitation patient in the field. PEC 2002;6:114-122
  • Leonov Y, et al. Hypertension with hemodilution prevents multifocal cerebral hypoperfusion after cardiac arrest in dogs. Stroke. 1992;23:45-53.
  • Sterz F, et al. Hypertension with or without hemodilution after cardiac arrest in dogs. Stroke. 1990;21:1178-84.
  • Kuboyama K, et al. Delay in cooling negates beneficial effects of mild resuscitative hypothermia after cardiac arrest in dogs. Crit Care Med. 1993;21:1348-58.
  • Markarian GZ, et al. Mild hypothermia:therapeutic window after experimental cerebral ischemia. Neurosurgery 1996, 38:542-551.
  • Nolan, JP. Therapeutic hypothermia after cardiac arrest: An advisory statement by the advanced life support task force of the international liaison committee on resuscitation. Circulation 2003;108:118-121.
  • Danzl DF. Accidental hypothermia. N Engl J Med. 1994;331:1756-60.
  • Patt, A. Effect of hypothermia induced coagulopathies in trauma. Surg Lcin North Am. 1988;68:775-85.
  • Roher MJ. Effect of hypothermia on the coagulation cascade. Crit Care Med. 1992; 20: 1402-05.
  • Valerie CR. Hypothermia induced platelet dysfunction Ann Surg. 1987;205:175-81.
  • Holzer M. Hypothermia for neuroprotection after cardiac arrest: Systematic review and individual patient data meta-analysis. Crit Care Med 2005; 33:414-18.
for more information
For More Information

Paul Hinchey

Jonathan Olson