Therapeutic hypothermia (TH) improves the outcome of neonates with moderate-to-severe hypoxic-ischemic encephalopathy resulting from perinatal asphyxia, but this is associated with a reduced glomerular filtration rate. Mannitol clearance reflects the glomerular filtration rate.

Mannitol clearance of a typical asphyxiated neonate (39.5 weeks, birthweight 3.25 kg, no TH) was estimated at 0.15 L/h, lower than the reported mannitol clearance of a healthy neonate (0.33 L/h) of similar age and weight.

Mannitol clearance is further decreased by approximately 60% in neonates who undergo TH, but this is likely confounded with asphyxia severity, as TH is applied only to newborns with moderate or severe asphyxia.