Head and Body Cooling

When a baby is deprived of oxygen before birth or during the labor and delivery process, a condition known as hypoxic-ischemic encephalopathy (HIE) may occur. A hypoxic-ischemic encephalopathy birth injury is considered a devastating complication in newborns, occurring in about 6 babies per 100 live births. Hypoxic-ischemic injury can happen in the perinatal period (before birth), in the late preterm period (between 34-37 weeks of pregnancy), and in full-term infants. Depending on the severity of the injury, serious physical and mental disabilities, and even death, may occur.

Birth asphyxia (when the cells in the body are deprived of oxygen) results from the inability of the placenta to deliver oxygen to the baby and remove waste products from the baby. The cells of the human body need oxygen, sugar, and water to burn fuel for energy. When these resources are not available, however, the body will use other forms of fuel, such as muscle and fat. These forms of fuel can cause organ damage and may result in encephalopathy (injury to the brain), multi-organ dysfunction (such as the kidneys, gut, lungs, and liver), seizures, and cell death. What follows is known as the “initial phase” of tissue injury, involving direct cellular injury (death) related to a lack of oxygen. The length of the initial phase is directly correlated to the length of time the body was deprived of oxygen, but usually lasts a maximum of three days.

During the period of secondary injury, or the “latent phase,” the brain’s metabolism returns to usual speed as oxygen and blood flow also become normal. With the metabolism returning to normalcy, by-products of the initial injury (such as excitatory neurotransmitters, cell death by-products, and inflammatory materials) are recirculated, causing additional injury. Hypothermia will slow down the metabolism in the brain if applied during this latent period, and helps protect the cells not injured in the initial phase of hypoxic damage.

Since the 1960’s, physicians have determined that cooling a baby’s head or body (hypothermia) during the latent phase of the tissue injury could reduce the damage caused by hypoxic-ischemic injury. This cooling method slows the metabolic processes that cause secondary cell death: When the body temperature is lowered, the demand for oxygen is also lowered. Further, since the brain is the organ that requires the most oxygen for proper functioning, it is the most susceptible to injury. Therapeutic hypothermia is now recognized as the standard of care, owing to a comprehensive study in 2005, for helping decrease brain injury in term infants with perinatal hypoxic-ischemic encephalopathy born at or after 36 weeks of pregnancy. The standard requires medical professionals to assess infants born after at least 36 weeks of pregnancy who were depressed (not vigorous) at birth to determine whether they meet the criteria for brain cooling. A mild reduction in brain temperature can slow down or stop the advancement of HIE—decreasing mortality rates and severe disabilities, as well as improving neurodevelopmental outcomes.

Brain hypothermia (cooling) is achieved by placing a water-filled cooling cap fitted around the infant’s head. Total body cooling is achieved by placing fluid-filled blankets or cool packs around the newborn in order to reduce the baby’s body temperature to between 89.6 and 95 degrees and maintaining this temperature without interruption for 72 hours. When the baby’s temperature is brought back up, it is done so very slowly until normal body temperature is achieved. Since some hospitals do not have the ability to practice this head and body cooling standard of care yet, babies in need of the treatment are typically quickly transferred to a hospital that can provide a higher level of care.