How to cool: devices

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How to cool devices

• Neeraj Badjatia, MD MSc
• Columbia University,
• College of Physicians and Surgeons
• nbadjatia_at_neuro.columbia.edu

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Historical hypothermia
Baltimore, 1955
Philadelphia, July 1936
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Radiation Transfer of heat between the separated
surfaces of two objects via electromagnetic
(infrared) radiation. Accounts for 5070 of
heat loss in awake patients
Evaporation Heat loss derived from the
evaporation of water from skin lungs Accounts
for 15 of heat loss (5 from the skin, 10 from
the lungs)
Conduction Direct transfer of between
surfaces Amount of heat loss is closely related
to contact surface Increases in the sitting or
lying position
Convection Transfer of heat from a surface to
the surrounding air. Accounts for 2030 of heat
loss
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Thermal compartments and cooling

• Peripheral compartment
• skin and extremities
• Peripheral cooling
• Convection
• Fans, air cooling blankets
• Conduction
• Ice pack, water cooling blankets, immersion
• Evaporation
• Alcohol baths
• Radiation
• Exposure (Operating Room)

• Core compartment
• trunk and head (excluding the skin)
• Core cooling
• Conduction
• Intravascular catheters
• Cooling blanket (Arctic Sun)
• Ice-cold crystalloid/colloid infusions
• Extracorporeal circulation

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Neuromuscular blockade

• Traditionally most efficient method by which to
  induce and maintain hypothermia
• Eliminates thermoregulatory defense mechanisms
  that try to prevent hypothermia
• Promotes cooling by convection (primary)
• Eliminates ability to follow neurological exam
• Tolerable for 24 hours in this disease model

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Neuromuscular blockade

• Concerns/Precautions
• Difficult to regulate temperature if used in
  isolation (overshoot)
• Monitoring (ie TOF) problematic in hypothermia
• Rely on continued clinical exam, changes in
  ETCO2/ventilatory patterns
• Association with Critical Illness Polyneuropathy
  (CIP)?
• Prolonged use and multi-organ disease
• Risk outweighed by potential for considerable
  benefit

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Induction of hypothermia

• Peripheral techniques with paralysis utilized in
  two NEJM studies
• Time to target
• HACA 8 hours (4 16)
• Bernard 0.9 C/hr
• TIME IS BRAIN
• More rapid induction needed
• Target core cooling

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Advances in Temperature Management

• Technological advancements
• Several new, FDA approved devices
• Target core temperature via conductive heat loss
  in a controlled feedback mechanism
• Feedback loops allow for tighter control of the
  rate and depth of hypothermia
• Less time to goal temperature
• Easier maintenance of temperature
• Range of temperature reduction 1.5 6.0 ºC / hr
• Markedly diminished nursing time

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Overshoot (Temp below 32C)
Overshoot more common with the Blanketrol II
device P0.016
Proceed Amer Thor Soc 2007 A392
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Innercool Celsius Control System

• Intravascular Cooling Catheters (9F,10.5F)
  Surface Vest system

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Medivance Arctic Sun
Pads connected to a bedside cooling unit that
circulates cold, sterile water 40 body surface
covered Pads may be left in place for three days
(72 hours)
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Cincinnati Sub Zero

• Update of previous blanketrol II device
• Covers more surface area
• Bedside unit allows for more programmable options
  for depth/rate of cooling
• Actual rates of cooling?

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ALSIUS CoolGard System

• Triple lumen subclavian catheter (9.3 F)
• Standard central catheter length (22 cm)
• Three lumens for infusion
• Two lumens connect to bedside unit for
  circulation of sterile saline through
  micro-balloons (closed-loop)

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Life Recovery Systems Thermosuit

• Extremely rapid cooling by ice water immersion
• Esophageal temperature probe
• Await more extensive clinical experience

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Induction with cold fluids

• Baumgardner et al. (Anesth Analg 89163169)
• Infusion of 5 mL/kg of refrigerated albumin 5
• Neurosurgical patients who had already been
  cooled to 34C
• Average temperature reductions of 0.6 0.1C
• Rajek et al (Anesthesiology 93(3)629 637)
• Infusion of 40 mL/kg of 4 C saline
• Induction of nine healthy volunteers
• Average temperature reductions of 2.5 0.4C
• Bernard et al. (Resuscitation 56(1)9-13)
• Infusion of 30 mL/kg of ice-cold Ringers lactate
  ice packs
• Induction in 22 patients following cardiac arrest
• Average temperature decrease was 1.7C
• Virkkunen et al. (Resuscitation 62(3)299-302)
• Infusion of 30 mL/kg Ringers lactate
• 13 cardiac arrest patients
• Average temperature reduction of 1.8C

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Cold crystalloid and colloid solutions

• Overall average cooling rates of 0.8C - 1.2C
  per liter infused
• None reported serious adverse effects
• None on use with established maintenance
  techniques
• Combined approach better?

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Induction with cold crystalloid and colloid
solutions

• Polderman et al (Crit Care Med 2005
  3327442751)
• Infusion of cold saline and albumin with cooling
  blankets (Arctic Sun and Blanketrol)
• 134 patients with various types of neurologic
  injury (postanoxic encephalopathy, subarachnoid
  hemorrhage, traumatic brain injury)
• Core temperatures decreased 36.9 1.9C to 34.6
  1.5C at 30 mins and to 32.9 0.9C at 60 mins
  (target temperature 32C33C
• No patient developed pulmonary edema
• Combined approach faster than either in isolation

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• 50 patients
• Indications for mild hypothermia or strict
  euthermia
• Randomized to 5 groups
• Conventional 30cc/kg cold IVF ice/cold
  packs
• Water circulating blankets (Blanketrol II,
  Cincinnati Subzero)
• Air circulating blankets
• Arctic Sun
• Intravascular balloon device
• Endpoints speed of cooling, time above or
  below temperature range

Crit Care 200711R91
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Cooling efficacy
Maintenance of target temperature. Depicted as
the percentage of time the patient's temperature
was 0.2C below or above the target temperature.
Induction of hypo- and normothermia. Pace of
cooling expressed asC/h
Crit Care 200711R91
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Cooling efficacy

• Water-circulating blankets, gel-coated water
  circulating pads and intravascular cooling were
  equally efficient in inducing hypothermia and
  normothermia
• Intravascular cooling with heat-exchange balloons
  was the most effective way to maintain goal
  temperature

Mean temperature deviation from target
temperature.
Crit Care 200711R91
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Devices Cooling safety

• Endovascular
• Benefits
• excellent temperature modulation
• cooling speed
• feedback loop
• Risks
• Infection, thrombosis, bleeding
• positioning issues / comfort
• shivering

• Surface
• Benefits
• safe and easy to use
• good temperature modulation
• feedback loop
• Risks
• slower cooling
• mild temperature flux
• shivering

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What does the future hold?
Peritoneal cooling (Velomedix)
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Summary

• Adequate therapeutic hypothermia can be performed
  by a combination of methods.
• Cold fluids, surface and endovascular
  alternatives
• Commercial cooling devices with feedback
  mechanisms
• improve the rate of cooling
• increase the percentage of time at goal
  temperature
• decrease overshoot
• Therapeutic hypothermia is nursing-intensive, and
  requires time, close attention, and training.
• Appropriate cooling device depends on your needs,
  specific safety concerns, and finances.