Elevation of body temperature to greater than 38°C was observed in several noncooled infants in the NICHD and CoolCap trials and
was associated with a worse outcome in the CoolCap trial. A rectal temperature of more than 38°C was also noted in some noncooled infants in TOBY. Experimental data showing that pyrexia may adversely affect neurodevelopment support the possibility that increased temperatures may contribute to the poorer outcomes seen in the noncooled groups; however, it is also possible that the relationship between higher elevation of body temperature and poor outcome reflects reverse causation (i.e., as- phyxia resulting in impairment of temperature regulation).