Children in sauna: cardiovascular adjustment.

Children's circulatory adjustment to a 10-minute heat stress in a climatic chamber was studied in 61 children and 20 adolescents and young adults. The thermal conditions corresponded to those of an ordinary Finnish sauna bath. In all subjects the rectal temperature and heart rate increased during the heat exposure (P less than .001). Systolic and diastolic blood pressures remained unchanged in sauna, but the systolic and especially the diastolic blood pressure decreased (P less than .001) in children less than 10 years of age immediately after the heat exposure; two vasovagal collapses developed. Cardiac output increased in all but the less than 5-year-old children (P less than .001). This was due to a significant decrease in stroke volume (32.9%) (P less than .001) in children less than 5 years old. Stroke volume declined slightly even in the older subjects. These changes indicate that the Finnish sauna bath puts great demands on a child's circulatory regulation. To avoid possible cardiovascular side effects, particularly small children should be supervised carefully during sauna bathing.