Facts and definition

Hypothermia — lowering of the body core temperature below the normal level (98.6⁰F), at which normal body functions are impaired.

Recreational activities, including kayaking — major source of immersion accidents. Hypothermia claims much more lives than drowning.

1. Respiratory system
- initial reflex gasp, followed by fast and deep breathing (hyperventilation) — 5’
- implications — aspiration of water, drowning, confusion, muscle tetany
- significant reduction of under-water breath-holding times — decreased survival

- slowing and eventually stopping of breathing

2. Cardio-vascular system — release of adrenaline

- peripheral vasoconstriction — blood flow to skin and muscles, core
insulation
- increase in heart rate and blood pressure — first few minutes
- irregular heart beat — extrasystole, ventricular fibrillation, sudden cardiac
death (remember, the lower the body temperature, the more likely the arrhythmias
and especially sensitivity of the heart muscle to mechanical stimulation)
- increased urine production — up to 350%, risk of hypovolemia, dehydration
- slowing and eventually stopping of the heart

Central nervous system

Tolerance to low oxygen levels and metabolic demands of the body

- progressive depression of mental statu
- moderate hypothermia — hallucinations, impaired judgment, disorganized
mental activity — panic, fear, loss of will to live
- loss of consciousness at core T < 80-86⁰F (27-30⁰C)

4. Musculo — skeletal system
- decreased blood supply to limbs, declining temperature of limbs
- impaired muscle performance - - limb strength, coordination, response time
- inability to swim, stay afloat, pull out of the water, use of signaling devices

• high rate of heat transfer - 100X higher than between skin and air with same T
• highest heat loss - groin, trunk and neck
• cooling rate-balance between heat production and heat transfer to water.