What is the difference between mild hypothermia and deep hypothermic circulatory arrest (DHCA) in CPB?

• A. Mild hypothermia uses no cooling; DHCA uses mild warming.
• B. Mild hypothermia lowers metabolic demand; DHCA involves deep cooling with planned circulatory arrest to protect organs during surgery.
• C. Mild hypothermia is for adults; DHCA is for pediatrics only.
• D. Mild hypothermia includes circulatory arrest; DHCA does not.

Answer: (B)

Cooling level on CPB changes how the body and organs are protected during surgery. Mild hypothermia cools the patient just enough to reduce tissue oxygen use, but continuous blood flow is maintained with the pump. This lowers metabolic demand so tissues are less vulnerable to brief periods of stress during the run of the circuit.

Deep hypothermic circulatory arrest takes cooling to a deeper level and deliberately stops blood flow for a planned period. The extreme cooling substantially lowers metabolic needs, enabling surgeons to work in a still, bloodless field while protecting organs despite the halt in perfusion.

So the difference is that mild hypothermia reduces metabolism while keeping circulation, whereas DHCA combines deep cooling with a controlled pause in circulation to allow complex surgical work to proceed with organ protection in mind.