Induction of Hypothermia After Intraoperative Hypoxic Brain Insult

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Induction of Hypothermia After Intraoperative
Hypoxic Brain Insult

• Anesth Analg, vol. 103 July 2006 180 1, David
  L. McDonagh, MD et al.

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CASE REPORT

• Age 57 y/o
• Gender female
• BW 87 Kg
• Dx Failed back surgery syndrome

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CASE REPORT

• OP Epidural spinal cord stimulator implantation
  through a laminotomy
• Pre-anes assessment
• No significant Px
• Lab WNL
• Anes spinal anesthesia
• Isobaric bupivacaine 15 mg
• Level T4
• Remifentanil IV infusion
• Stimulator placement was successful

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CASE REPORT

• 2 hrs later, block regressed
• ? ?remifentanil infusion rate
• ? still painful
• ? remifentanil IV bolus 100 µg
• Loss of consciousness apnea
• ? establish ventilation but in vain
• ? emergently turned supine
• ? bag-mask ventilation and resuscitation

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CASE REPORT

• Vital sign
• SpO2 30
• HR 20 / min
• SBP 40 mmHg
• Bradycardia and hypotension responded to
  oxygenation and Atrpine
• Hypoxemia period 7 mins

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CASE REPORT

• Suspected hypoxic brain injury
• Did not awaken 20 mins after last remi.
• Naloxone 400 µg IV incrementally in vain
• Decerebrate posturing to pain stimuli

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CASE REPORT

• Decided to induce moderate hypothermia (target 32
  ?) in the OP room
• Sedated with propofol infusion
• On BIS and keep bispectral index 40-60
• Cisatracurium
• Ice packs around the head
• IV infusion of 6L of refrigerated N/S
  nasopharyngeal temperature decreased from 36C to
  33C over 60 min.
• On ICY catheter with Coolgard (Alsius Corp.,
  Irvine, CA)

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CASE REPORT

• Transported the pt to neurointensive care unit
  and maintained 32 ? for 20 hrs
• Hyperglycemia required IV insulin infusion only
  therapeutic complication

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CASE REPORT

• Passive rewarming the next morning
• neurologically normal on awakening
• MBD the next day
• 2-wk and 3-mo F/U
• fuzziness of her memory for events over the
  preceding 2 mo before the op

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• DISCUSSION

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• Morbidity and mortality in patients successfully
  resuscitated from cardiac arrest primarily
  depends on neurological outcome
• Clinical trials of therapies directed toward
  reducing the extent of neuronal damage by means
  of pharmacological agents have been disappointing
  
• To date, the only clinically effective tool for
  amelioration of brain damage by ischemia and
  reperfusion is mild to moderate induced
  hypothermia
• Rincon, Fred M.D. et al. Therapeutic Hypothermia
  for Brain Injury after Cardiac Arrest. Seminars
  in Neurology. 26(4)387-395, September 2006.

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• Treatment of hypoxic brain injury with moderate
  hypothermia was investigated more than 45 years
  ago
• Benson DW, Williams GR, Spencer FC, Yates A. The
  use of hypothermia after cardiac arrest. Anesth
  Analg 1959384238.

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• Prospective randomized, multicenter trial (275)
• Out-of-hospital patients resuscitated after
  cardiac arrest due to VF
• Hypothermia (32-34? within 4 hr, maintain 24 hr)
• Normothermia
• The Hypothermia After Cardiac Arrest Study Group.
  Mild therapeutic hypothermia to improve the
  neurologic outcome after cardiac arrest. N Engl J
  Med 200234654956.

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• Randomized controlled , multicenter trial (77)
• Out-of-hospital cardiac arrest
• Remained unconscious after return of spont.
  circulation
• Hypothermia (33 ?, 12 hr)
• Normothermia
• Bernard SA, et al. Treatment of comatose
  survivors of out-of-hospital cardiac arrest with
  induced hypothermia. N Engl J Med 200234655763.

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• Randomized , multicenter trial (239)
• Hypothermia (whole-body cooling to an esophageal
  temperature of 33.5C for 72 hours)
• Normothermia
• Shankaran S, et al. Whole-body hypothermia for
  neonates with hypoxic-ischemic encephalopathy. N
  Engl J Med 2005353157484.

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Possible mechanism of protection effect of
hypothermia

• In the normal brain, hypothermia reduces the
  cerebral metabolic rate for oxygen (CMRO2) by 6
  for every 1C reduction in brain temperature
  gt28C
• Steen PA, et al. Hypothermia and barbiturates
  individual and combined effects on canine
  cerebral oxygen consumption. Anesthesiology.
  1983 58 527532
• After cardiac arrest in dogs, CMRO2 is not
  significantly reduced by mild hypothermia
• Oku K, Sterz F, Safar P, et al. Mild hypothermia
  after cardiac arrest in dogs does not affect
  postarrest multifocal cerebral hypoperfusion.
  Stroke. 1993 24 15901597

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Possible mechanism of protection effect of
hypothermia

• Mild hypothermia?reperfusion injury by
• ?free radical production
• ?excitatory amino acid release
• ?calcium shifts ? mitochondrial damage and
  apoptosis
• Colbourne F, et al. Postischemic hypothermia a
  critical appraisal with implications for clinical
  treatment. Mol Neurobiol. 1997 14 171201
• Ginsberg MD, et al. Therapeutic modulation of
  brain temperature relevance to ischemic brain
  injury. Cerebrovasc Brain Metab Rev. 1992 4
  189225

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Weak points

• Exclude up to 92 of patients with
  out-of-hospital cardiac arrest
• Caregivers could not be blinded
• Normothermia group gt38C, as is often seen after
  cardiac arrest
• Adverse events occurred more in the hypothermia
  groups
• Lower cardiac index
• Higher systemic vascular resistance
• Hyperglycemia
• Pneumonia (non-significant)
• Sepsis (non-significant)
• Bleeding (non-significant)

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Further Problems

• Selection of patients
• Comatose after cardiac arrest from
• Any rhythm ?
• Any cause ?
• After in-hospital cardiac arrest ?
• Pregnant patients
• Patients with primary coagulopathy

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Further Problems

• Timing of cooling
• ASAP after ROSC
• Golden hours ?
• Optimal -
• Cooling rate ?
• Target ?
• Duration ?

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Further Problems

• Cooling Techniques and Monitoring
• Intravenous
• Chilled crystalloid IV infusion
• Intravascular heat exchange device
• External
• External cooling blankets
• Ice pack to groin, neck, axilla
• Wet towels, fanning, cooling helmet
• Monitoring
• Bladder temperature probe
• Pulmonary artery catheter

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ILCOR Recommendations

• Unconscious adult patients with spontaneous
  circulation after out-of-hospital cardiac arrest
  should be cooled to 32C to 34C for 12 to 24
  hours when the initial rhythm was VF
• Such cooling may also be beneficial for other
  rhythms or in-hospital cardiac arrest
• Nolan JP, et al. Therapeutic hypothermia after
  cardiac arrest an advisory statement by the
  advanced life support task force of the
  International Liaison Committee on Resuscitation.
  Circulation 200310811821

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Take - home message

• Definitely
• Adult
• Out-of-hospital
• Cardiac arrest due to VF
• ROSC
• Ischemic brain insult
• Neonate
• Birth asphyxia, severe acidosis, perinatal
  complications
• Resuscitation at birth
• ROSC
• Moderate to severe encephalopathy
• Be careful of IVG with prone-positioned pt
• Consider therapeutic hypothermia if ischemic
  brain insult occurs perioperatively

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• Thanks for your attention.