Hypothermia means low body temperature, clinically defined as a core temperature below 95F (35C). (Your body core is basically your entire body minus your arms and legs.) It takes about thirty minutes for an adult of average size to develop hypothermia – even in freezing water. You have to survive both cold shock and incapacitation before hypothermia becomes an issue.
As body temperature falls below 95F (35C), both mental ability and consciousness suffer, and like cold shock and incapacitation, the primary danger is drowning.
Badly Chilled vs Hypothermic
It can be very difficult to tell the difference between someone who is badly chilled from someone who has hypothermia. Because of the physical and mental effects of cold shock and physical incapacitation, many hypothermia symptoms can be present in people who have a normal body temperature. In other words, it’s quite possible for a badly chilled person to have difficulty thinking and speaking clearly, and to also be physically incapacitated, shivering violently, and unable to use their hands.
The only sure way to determine if someone has hypothermia is to measure their core body temperature, something that can’t be done orally. Trying to obtain a rectal temperature in the field is both difficult and a bad idea because it’s tough on the victim and a poor use of your time. From a practical standpoint, all you’ll to have to guide you are the environmental circumstances and the appearance and behavior of the victim.
Regardless of whether the person is chilled or hypothermic, you’re going to have a very big problem on your hands because neither situation is easy to deal with in the outdoors. Your first objective should be to stop the person from losing any more heat and getting even colder.
Not Just an Immersion Issue
You can become badly chilled or hypothermic even if you never enter the water. Whenever body heat is lost to the environment faster than you can replace it, incapacitation will be followed by hypothermia. In cold, windy, rainy weather, a person exposed to the elements can quickly become incapacitated while paddling or making camp. Again, the first things to go are your hands.