Cerebral ischemia: deep hypothermia
Last updated: 03/04/2015
Used in cardiac surgery, thoracic surgery, neurosurgery. Temperature reduced to 15-22 degrees C, after which circulation is stopped. Note that because you cannot actually measure brain temperature, full flow CPB is maintained 20-30 minutes after reaching 15-22C, to ensure adequate cerebral cooling. If BIS or EEG is available, verify isoelectricity before cessation of circulation. The most important factor during DHCA is operative time (45 to 60 minutes or less). Modalities such as ice packs, steroids, propofol/barbiturates, which are intended to improve outcomes, are not supported by good evidence.
Cerebral ischemia can occur hours after DHCA, because CBF and CVR are deranged for several hours after temperatures return to normal.
Circulate cold blood 5-10 minutes prior to rewarming (wash out metabolites) and consider selective cerebral perfusion if more than one hour of operative time is needed. Anterograde perfusion is thought to be superior to retrograde perfusion but this has not been proven definitively.
Deep Hypothermic Circulatory Arrest
- 15-22 degrees Celsius (maintain for ~ 30 mins prior to stopping circulation
- Verify isoelectric brain prior to stopping circulation
- Rapid surgery is beneficial, nothing else has been shown to help
- 45 to 60 minutes is upper limit of safe time period
- Circulate cold blood 5-10 minutes prior to rewarming (wash out metabolites) and consider selective cerebral perfusion (may extend safety margin to 90 minutes)
- Cerebral ischemia can occur several hours after DHCA
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