Hypothermia is a condition in which the core body temperature drops below 35.0 C

Question

Hypothermia is a condition in which the core body temperature drops below 35.0 C. A person suffering from hypothermia is usually treated with warm (approximately 43.0 C) humidified air and intravenous (IV) fluids.

(a)Basal heat production is 1850 kcal/day at 37.0 C and increases to three times higher at 33.0 C. The rate of heat production between these two temperature can be assumed to be linear. Assuming that the heat capacity of the body is approximately equal to that of water, how long would it take to warm the body without any outside heating?

(b)How much IV fluid would be needed to rewarm the blood in the body if basal heat production was ignored? Considering that the total volume of blood in the body is approximately 5.0 L, how approximate is this method as a warming technique?

(c)The breathing rate is approximately 6.0 L/min. If the heat capacity of air over our range of interest is 29.1J/(mol · C), how long would it take to rewarm the body if the only heat source was the warm humidified air?

(d)Your answers should indicate that the warm IV fluid and humidified air do not play a significant role in rewarming a hypothermic person. Instead, they are generally used to prevent further heat loss. For example, the body usually loses heat during breathing. Using the warm humidified air prevents this heat loss. The warm IV and humidified air treatments are especially important in preventing the overcooling of vital organs, such as the brain and heart. Generally they require administration by paramedics or doctors with the proper equipment. Propose a method to warm a hypothermic person if paramedics and hospitals are not available. Explain its advantages and disadvantages.

Explanation / Answer

The total heat required by the body is as follows:

Assume the weight of the body is 60 kg = 60 x 103 g3

The amount of heat required (Q) = m X delta C x delta T

delta C = specific heat

delta T = final temperature - initial temperature = the change in temperature required = 37 - 33 = 4o C.

Q = (60 x 103) (4.184)(4) = 1003 x 103 joule or 1003 kJ = 239.8 kcal or 240 kcal

At 33o C, the heat production of the body increases thrice, that is 1850 x 3 = 5550 kcal/day = 15 kcal/min.

The time required to heat the body at this rate, to 37 C is 240/15 = 16 min

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