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					     Neeraj Badjatia, MD MSc

       Columbia University,
College of Physicians and Surgeons

  nbadjatia@neuro.columbia.edu
Historical hypothermia




   Baltimore, 1955


                     Philadelphia, July 1936
Radiation                                     Evaporation
Transfer of heat between the separated        Heat loss derived from the evaporation of
surfaces of two objects via electromagnetic   water from skin & lungs
(infrared) radiation.                         Accounts for ±15% of heat loss (5% from
Accounts for 50–70% of heat loss in awake     the skin, 10% from the lungs)
patients




Convection                                    Conduction
                                              Direct transfer of between surfaces
 Transfer of heat from a surface to the
                                              Amount of heat loss is closely related to
surrounding air.
                                              contact surface
Accounts for 20–30% of heat loss
                                              Increases in the sitting or lying position
      Thermal compartments and cooling
Peripheral compartment Core compartment
     skin and extremities                trunk and head (excluding the
   Peripheral cooling                     skin)
                                        Core cooling
     Convection
                                          Conduction
      ○ Fans, air cooling blankets
                                           ○ Intravascular catheters
     Conduction
                                           ○ Cooling blanket (Arctic Sun)
      ○ Ice pack, water cooling
        blankets, immersion                ○ Ice-cold crystalloid/colloid
                                             infusions
     Evaporation
                                           ○ Extracorporeal circulation
      ○ Alcohol baths
     Radiation
      ○ Exposure (Operating Room)
        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
       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
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
  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
Overshoot (Temp below 32°C)
90
                                            “Overshoot” more
80                                          common with the
70                                          Blanketrol II device

60                                          P=0.016

50
                                              Blanketrol II
40                                            (overall 77%)
30
                                              Arctic Sun
20                                            (overall 14%)

10
0    none     mild     moderate    severe
            (31-32C)    (30-31C)   (<30C)


                                   Proceed Amer Thor Soc 2007; A392
Innercool: Celsius Control System

  Intravascular Cooling Catheters (9F,10.5F) & Surface
     Vest system
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)
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?
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)
Life Recovery Systems:
Thermosuit
 Extremely rapid
  cooling by ice water
  immersion
 Esophageal
  temperature probe
 Await more extensive
  clinical experience
Induction with cold fluids
 Baumgardner et al. (Anesth Analg 89:163–169)
     Infusion of 5 mL/kg of refrigerated albumin 5%
     Neurosurgical patients who had already been cooled to 34°C
     Average temperature reductions of 0.6 ± 0.1°C
 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 ± 0.4°C
 Bernard et al. (Resuscitation 56(1):9-13)
     Infusion of 30 mL/kg of ice-cold Ringer’s lactate & ice packs
     Induction in 22 patients following cardiac arrest
     Average temperature decrease was 1.7°C
 Virkkunen et al. (Resuscitation 62(3):299-302)
     Infusion of 30 mL/kg Ringer’s lactate
     13 cardiac arrest patients
     Average temperature reduction of 1.8°C
Cold crystalloid and colloid solutions

   Overall average cooling rates of 0.8°C -
    1.2°C per liter infused

   None reported serious adverse effects

   None on use with established
    maintenance techniques

   Combined approach better?
Induction with cold crystalloid and colloid
solutions
    Polderman et al (Crit Care Med 2005; 33:2744–2751)
      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 ±1.9°C to 34.6 ±
       1.5°C at 30 mins and to 32.9 ± 0.9°C at 60 mins (target
       temperature: 32°C–33°C
      No patient developed pulmonary edema


    Combined approach faster than either in isolation
   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 2007;11:R91
 Cooling efficacy




Induction of hypo- and normothermia.   Maintenance of target temperature.
Pace of cooling expressed as°C/h       Depicted as the percentage of time the
                                       patient's temperature was 0.2°C below
                                       or above the target temperature.



                                                      Crit Care 2007;11:R91
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
Mean temperature deviation from
target temperature.                   was the most effective
                                      way to maintain goal
                                      temperature


                                              Crit Care 2007;11:R91
Devices: Cooling safety
Endovascular:                  Surface:
Benefits:                      Benefits:
     excellent temperature       safe and easy to use
      modulation                  good temperature
     cooling speed                modulation
     feedback loop               feedback loop
Risks:                         Risks:
     Infection, thrombosis,        slower cooling
      bleeding                      mild temperature flux
     positioning issues /          shivering
      comfort
     shivering
What does the future hold?




                      Peritoneal cooling (Velomedix)
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.

				
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