Therapeutic Hypothermia

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Therapeutic Hypothermia
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• They said I had ice on me for more than a day
  but I dont remember. I dont remember anything
  but the nurses voice telling me I was gonna be OK
  and I believed her. I think my family was there
  for awhile the nurse was always there.. Male
  patient 47 years old, treated with fentanyl,
  versed, propofol and pancuronium

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2005 ILCOR

• There seems to be good evidence (level 1) to
  recommend the use of induced mild hypothermia in
  comatose survivors of-out-hospital cardiac arrest
  caused by VF.
• Level 1 evidence indicates one or more randomized
  clinical trials in which benefit was shown

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Evidence

• Two randomized control trials Hypothermia after
  cardiac arrest (HACA) and the Bernard trial.
• These studies both enrolled comatose patients
  following resuscitation from VF or pulseless VT
• All were sedated, chemically paralyzed and
  ventilated.
• Induction occurred within 6 hours and continued
  for 12-24 hours

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Evidence
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• NNT of 7 to prevent 1 death with TH
• NNT of 6 to reduce neurologic impairment with TH
• DefinitionThe NNT is the number of patients who
  need to be treated in order to prevent one
  additional bad outcome

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Adverse Events

• Bleeding, pneumonia, sepsis, pancreatitis, renal
  failure, pulmonary edema, seizures, arrhythmias
  and pressure sores were recorded in both trials
  with no significant adverse events.
• Sepsis was more likely to develop in the
  patients with hypothermia than those in
  normothermia, although this difference was not
  statistically significant (HACA study group,
  2002)

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What is the purpose of TH?

• Aimed at minimizing the effects of anoxic
  neurologic injury following cardiac arrest
• Other than supportive care TH it is the only
  identified measure to improve quality of life
  post resuscitation

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So why is TH not done more often?
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Suggested Inclusion Criteria

• TH is indicated if the patient meets all of the
  following criteria
• Witnessed arrest
• Initial rhythm VF or pulseless VT. But
• Time to ACLS was less than 15 minutes and total
  of ACLS time less than 60 minutes
• GCS of 8 or below
• SBP of gt 90 with or without vasopressors
• Less than 8 hours have elapsed since return of
  spontaneous circulation (ROSC)

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Suggested Exclusion Criteria

• Pregnancy
• GCS 10 and improving
• Down time of gt 30 minutes
• ACLS preformed for gt 60 minutes
• Known terminal illness
• Comatose state prior to cardiac arrest
• Prolonged hypotension (ie MAP lt 60 for gt30
  minutes)
• Evidence of hypoxemia for gt 15 min following ROSC
• Known coagulopathy that cannot be reversed

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• The doctor came in after it was all overNow I
  gutta have a box put in my heart so that wont
  happen againthat doctor sure is hard to
  understand but the nurse tells me what he said
  after he leaves.

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Lets get started on cooling

• Neuro exam including pupillary reaction to
  light, corneal reflex, gag/cough and GCS
• Send routine cardiac bloods and coagulation
  studies
• Obtain order for TH from ER/attending physician
  and begin cooling in the ER
• Do NOT forget analgesia, sedation and paralytic
  agent if shivering occurs. Obtain orders before
  the physician leaves

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Suggestions for Analgesia and Sedation

• Fentanyl infusion 0.7 10 mcg/kg/hour
• Midazolam 0.04 0.2 mg/kg/hour
• Propofol 1-5 mg/kg/hour
• Paralytic Agents when shivering is detected
• Pancuronium 0.1 mg/kg for 2 hours
• Rocuronium 0.6 1.0 mg/kg for 1 hour
• Note both physicians who have offered these
  recommendations are from Eastern Canada!

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Use of a nerve stimulator will assist you in
providing the appropriate amount of paralytic
agent
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Target Temp 32-34 Celsius

• PA catheter
• Esophageal thermometer
• Bladder thermometer
• Rectal thermometer
• Try to avoid oral if possible and never use
  axilla
• Most common is a continuous rectal thermometer
  incorrect measurement can occur if the colon is
  full of stool or the groin ice packs touch the
  connection cable

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Achieving the temperature

• Ice gel packs to head, groin, axilla and torso
  may require up to 30 packs (15 on and 15 in
  freezer)
• Damp sheet on top with fan directed
• Cooling blanket below and above the patient if
  available
• If target temp not achieved in 4 hours then
  refrigerated IV solution can be administered at a
  rate of 100ml/hr
• Some facilities have a cooling helmet (Halifax)
• Note the time you started the process, 24 hours
  from this time cooling stops.

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Pack Placement

• Apply cotton wrapped ice packs for 20-30 minutes
  and then provide a 10 minute rest. During the
  rest period the skin is inspected thoroughly for
  signs of frostbite (white skin, darkened skin,
  blisters)
• Once the temp hits 33 stop the ice packs and
  monitor for further drop, less than 32 degrees
  can cause dysrythmias and coagulopathies

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Shivering

• Shivering is the bodies way of rewarming itself
  and will interfere with the cooling process. It
  will also cause your CO2 to rise leading to
  respiratory acidosis
• Treated with a neuromuscular blocking agent such
  as pancuronium

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Transferring to the Cath Lab

• Stop the cooling process, transfer to the lab and
  upon return continue with the process. Do not
  reset the timer (24 hours in total)

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Defibrillation

• Wipe off the chest area where the pads will be
  placed. Ensure there is no water laying on the
  chest and finally ensure you are not standing in
  water
• The use of packs is preferred as there is minimal
  water in the bed
• It is OK if the sheet under the patient is wet,
  make sure you are clear, just as you would in a
  normal defibrillation

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Passive Rewarming

• Done passively discontinue the cooling measures
  and place a blanket on the patient
• The goal is normothermia in 8 hours
• Shivering during the rewarming stage can be
  treated with 10-20 mg of IV demerol
• If normothermia has not been achieved in 8 hours
  then active rewarming is started

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Active Rewarming

• Warm blankets, more bedding
• Active rewarming is stopped when temp reaches 36
  degrees
• Monitor for rebound hyperthermia

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Additional Monitoring

• Monitor glucose q2hr
• Monitor serum potassium q4hr
• ABG q4hr is also indicated
• An arterial line is preferred as cooling shuts
  the patient down peripherally

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• Im not sure where I am or what happened my wife
  said I died. the nurse knows what happened

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Physiology of Hypothermia
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Neurological System

• Increase oxygen delivery to ischemic brain tissue
• Decrease ICP due to vasoconstriction
• Minimizes production of free radicals and
  excitory neurotransmitters that occur during
  ischemia and with reperfusion. May also reduce
  risk of seizures

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Cardiovascular

• Initially shivering increases HR and SV then as
  shivering subsides the HR often drops to lt 60 and
  is sometimes refractory to atropine
• Vasoconstriction increases SVR
• Peripheral pulses are faint due to
  vasoconstriction
• If temp falls below 27 degrees VF or asystole may
  occur

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ECG changes Osborn Waves
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ECG changes

• Widened QRS
• ST segment elevation or depression (always
  consider ischemia/infarction first)
• QT interval may be prolonged hours or days after
  warming

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Pulmonary Effects

• Increase RR initially but changes with paralysis
• PVR increases and bronchials dilate causing a V/Q
  mismatch

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Renal

• Cold induced diuresis occurs due to a decrease in
  absorption in the nephron
• Resistance to vasopressin and ADH leading to
  further diuresis
• Hypothermia causes K to shift into the cells
  resulting in hypothermia, as rewarming occurs
  potassium shifts back in to the plasma leading to
  hyperkalemia

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Hematologic System

• Hemoconcentration occurs due to cold diuresis and
  third spacing of fluid related to increased
  vascular permeability and leads to an increase in
  blood viscosity
• Decrease in and function of WBCs leading to
  increased of infection
• Decrease in and function of platelets
  predisposing to bleeding
• Coagulopathies occur due to disruption of enzyme
  reactions in clotting cascade

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• Nurses never left his sidethey even eat their
  lunch thereshe let me hold his hand and talk to
  himat first I felt stupid talking to him but she
  made me feel so comfortable.

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• Discussion question Who are the change agents
  that can make this a standard of care in your
  hospital?
• Does anyone see a great nursing research project
  (or 2) in this area of resuscitation?