High work output combined with high ambient temperatures caused heat exhaustion in a wildland firefighter despite high fluid intake

The purpose of this case study is to examine the physiological/behavioral factors leading up to heat exhaustion in a male wildland firefighter during wildland fire suppression. The participant (24 years old, 173 cm, 70 kg, and 3 years firefighting experience) experienced heat exhaustion following 7 hours of high ambient temperatures and arduous work on the fire line during the month of August. At the time of the heat-related incident (HRI), core temperature was 40.1°C (104.2°F) and skin temperature was 34.4°C (93.9°F). His work output averaged 1067 counts·min^-1 (arbitrary units for measuring activity) for the 7 hours prior to the HRI, a very high rate of work over an extended time period during wildfire suppression. In the 2.5 hours leading up to the heat incident, he was exposed to a mean ambient temperature of 44.6°C (112.3°F), with a maximum temperature of 59.7°C (139.5°F). He consumed an average of 840 mL · h^-1 in the 7 hours leading up to the incident and took an average of 24 ± 11 drinks · h^-1 (total of 170 drinks). The combined effects of a high work rate and high ambient temperatures resulted in an elevated core temperature and a higher volume and frequency of drinking than typically seen in this population, ultimately ending in heat exhaustion and removal from the fire line. The data demonstrate that heat-related incidents can occur even with aggressive fluid intake during wildland fire suppression.