Many parents wonder how the cooling process works and how therapeutic hypothermia halts the spread and severity of brain damage. The science behind hypothermia therapy is complicated. Simply put, infant cooling therapy is a process where your infant is cooled and then gradually warmed up again. A specially-made blanket, mattress, or head cap will be used to cool the newborn in a controlled way. There are 2 different approaches to therapeutic hypothermia: Passive cooling techniques involve removing external heat sources from the newborn, such as blankets and heating lamps. This method is commonly used by remote hospitals and facilities with limited infrastructure that may be unable to transport newborns to a hypothermia center for active cooling within 6 hours. Active cooling is the preferred method. One study found that "the use of active cooling during neonatal transfer achieves target temperature in a shorter period and maintains better temperature stability." While the newborn cooling protocol and processes can vary depending on the hospital, it typically involves placing the baby on a waterproof blanket or putting a cooling cap on their head that contains cool circulating water until the cooling baby's body temperature is reduced to as low as 33.5 degrees Celsius or about 92.3 degrees Fahrenheit—below homeostasis—for around 72 hours. This reduced body temperature helps slow the newborn's metabolic rate, which allows their cells to heal and prevents the further spread of brain damage. When the baby’s body temperature is cooled, it slows the baby’s metabolism or metabolic rate. Metabolism is a set of chemical reactions that happen in all of our cells in which food is converted to fuel to run our cells, organs and bodies. Those chemical reactions require oxygen. If oxygen is removed from the chemical reaction, the reaction still happens but it produces a harmful byproduct—lactic acid—that damages or kills cells. When there is enough oxygen, the brain cells produce energy in a normal chemical reaction causing aerobic respiration. The chemical reaction produces energy for the cells to function and harmless byproducts. But, when the blood flow and oxygen to the brain is disrupted, the chemical reaction changes to anaerobic respiration which produces lactic acid as a byproduct. Lactic acid build ups and triggers release of several harmful chemicals, including highly reactive free radicals. Meanwhile, cell walls break down causing swelling or “edema.” As the brain cells die, the cooling baby’s immune system sends neutrophils and macrophages to clean up dead cells, which starts a chain reaction by producing free radicals that further damage cells, deepen the inflammatory response, aggravate cerebral swelling and cause further neurological injury. When the baby is resuscitated and the blood and oxygen return, this can further damage the cells and tissues that are already weak from the initial injury. The damaged cells are leaky and the newly returned blood flow can make the cerebral edema (the swelling) worse, causing more inflammation and more free radical release. Cooling or therapeutic hypothermia helps shut down this process. Cooling the newborn is believed to minimize damage to the baby’s brain by: Reducing energy depletion Reducing the metabolism Decreasing excitatory transmitter action in their brain Reducing ion flux alterations Reducing edema (swelling) Reducing vascular permeability Reducing blood-brain barrier disruptions