HEAT INJURIES

• Too Much Heat
• Too Little Water

Preparation for Deployment

• Physical Fitness
• Acclimatization
• Avoid De-Training Enroute or On-Site
• Logistical Planning
  • Personal
  • Unit

Personal Supplies

• Sunscreen
• Hats
• Scarves/Bandannas
• Canteens

Unit Planning

• Water Containers
• Water Purification
• Field Sanitation Teams
• Sunscreen
• Work-Rest Schedules
• Buddy System
• Secure Water Resources
• Shade, Cool, and Insulate Water Containers
• Water Flavoring
• Fans, Air Conditioning
• Weather Intel

PHYSIOLOGY

Environment

• Heat Stress
  • Air Temperature
  • Humidity
  • Air Movement
  • Heat Radiation

Mechanisms of Heat Gain

• Radiation
  • Direct Sunlight
  • Engines
  • Asphalt Surfaces
  • Sand
• Convection= Warm Air
• Conduction= Direct Contact

Mechanisms of Heat Loss

• Conduction
• Convection
• Evaporation= The only mechansim when air temperature is > Skin Temperature (92° F)
• Radiation

WBGT Index
70% Wet Bulb Temperature- affected by air temperature and humidity
20% Black Globe Temperature- affected by radiant heat and air movement
10% Dry Bulb Temperature- air temperature (and some radiant heat)

Water Requirements Increased by:

• Heat
• Wind
• Dry Air
• Physical Activity

Heat Stress in Aviation Operations
Heat Stress occurs during:

• Maintenance
• Preflight
• Engine Start
• Taxi
• Standby for Takeoff

Effects of Dehydration

• Increases Risk of Heat Injury
• Reduced Work Capacity
• Reduced G-Tolerance
• Reduced Alertness and Mental Status
• Reduced Appetite
• Thirst
• Darker Urine

Soldiers in the desert exhibit "voluntary dehydration": They maintain themselves at 2% of bodyweight (@ 1.5 Liters) below their ideal hydration staus without any sense of thirst.

Chronic Dehydration

• Constipation
• Kidney Stones
• Hemorrhoids
• Urinary Tract Infections

RISK OF HEAT INJURY IS INCREASED BY:

• Poor physical fitness
• Dehydration
• Alcohol
• Smoking
• Medications
• Sunburn
• Sleep Deprivation
• Skin Disease
• Age
• Obesity
• Chronic Medical Conditions
• Illness
• Fever
• Caffeine
• Missed Meals
• Pregnancy
• Poor Hygiene
• History of Heat Stroke
• Poor Morale
• Poor Leadership
• Stupidity

Medications that Can Increase Risk of Heatstroke

• Antihistamines
• Decongestants
• Blood Pressure Medications
• Antidepressants
• Anti-nausea medications
• Aspirin
• Laxatives

CLINICAL SYNDROMES

• Heat Cramps
• Heat Edema
• Prickly Heat
• Heat Exhaustion
• Heat Stroke

WORK-REST CYCLES
Apply to:
Hydrated, Acclimatized, Rested Soldiers


Maximum Sweating Rate = 2.1 Quarts/Hour
Maximum Rate of Water Absorption from the Gut = 1.5 Quarts/Hour

THEREFORE:

• REST (to reduce sweating)
• CONTINUE TO DRINK DURING REST CYCLES
• Enforce mandatory drinking schedules

WEAK LINK RULE
One heat casualty is usually followed by others

ACCLIMATIZATION

• Day 1-2
  • Light Activities: Calisthenics, Volleyball
• Day 3
  • 2 mile unit runs at the pace of the slowest participants
• Day 10
  • Normal physical training schedule (adapted for the environment)

Water requirements ARE NOT REDUCED; they may increase.

Consume Rations; Don't Need Salt Tablets


Individual Discipline

• Carry Water
• Drink before work
• Eat
• Check Your Buddy
• Check Your Pulse
• Wear Your Clothes (to avoid direct sunlight)
• Wear Sunscreen
• Seek Cool Areas
• Check Your Urine
• Sleep

Looking Out for Symptoms in Your Buddy

• Slowing of Thought Processes
• Sluggishness
• Sleepiness
• Irritability
• Rapid Breathing

THREE LEVELS OF HEAT ILLNESS

• Heat Stroke
• Heat Injury
• Heat Exhaustion
  
  
  
  
  
  Heat Stroke
• Collapse of Thermoregulatory System
• Neurologic Injury
  • Coma
  • Obtundation
• Organ Damage
  • Kidneys
  • Liver
  • Lungs
  • Muscle Breakdown

Heat Injury: Similar to Heatstroke, but no coma or obtundation

Heat Exhaustion: Inability of the circulatory system to meet demands, No Organ Damage

Evaluating

• Questions
  • Orientation
  • Memory (short term)
  • Simple Math
• Pulse
• Temperature (Rectal)
• Breathing Rate
• Rate of Sweating
• Urine Color
• Weight
• Orthostatic Blood Pressure

TREATING A HEAT INJURY

• SHADE
• Remove heavy clothing
• If Alert: Start them drinking---- 3 quarts cool water
• Lower Body Temperature

Spray water on skin and T-Shirt
Fan
Cold water immersion until Temp < 102°

If Unconscious or Confused:
EVAC

If Confused and Very Hot:
EVAC
Immerse in Cool Water or Ice


FLUIDS
1/2 Strength Gatorade
Quart Canteen, with 1/4 tsp salt

HEAT CRAMPS

• Due to Salt Depletion
• Prevent by Eating
• Do Not Use Salt Tablets

Minor Syndromes (not Heat Injuries)

• Heat Rash
• Heat Edema
• Parade Syncope
• Sunburn

REFERENCES

• FM 21-20
• FM 21-10-1 Unit Field Santiation Team Oct 89
• AR 40-5 Preventive Medicine Aug 86
• USARIEM Technical Note 91-2
• Sustaining Health and Performance in the Desert (pocket guide)
• FM 34-81 Weather Support for Army Tactical Operations, Aug 1989
• TB MED 507 Prevention, Treatment and Control of Heat Injury Jul 80
• GTA 8-5-45
• FM 10-52-1 Commander's Guidebook for Water Usage in Desert Operations, May 83