Environmental Considerations Flashcards
What regulates thermoregulation?
The integumentary system, CNS, and CVS all help regulate this. The hypothalamus is the thermoregulation center. It receives information from the blood and the skin and then sends signals to the skin for vasoconstriction or vasodilation. It also regulates sweat production.
How is heat transferred?
- Convection (transferred through air; if no wind then this is reduced)
- Conduction (through physical touch; through water)
- Radiation (via electromagnetic radiation from higher to lower energy surfaces, i.e. sun or higher/lower temperature)
- Evaporation (vaporization of sweat; most efficient for athlete)
Risk factors for heat illness?
- High temperature
- Humidity (can’t evaporate sweat)
- Sports equipment (helmet/hat…lots of heat released from head)
- Cumulative effect (being in the heat multiple days in a row)
- Dehydration
- Medication (alcohol, stimulants)
- Prepubescent
- Obesity (heat production is proportional to body weight, heat loss proportional to body surface area. Fatties have a worse ratio)
- Poor fitness
- Sleep deprivation
Wet Bulb Globe Temperature
This is the lowest temperature a surface can reach through evaporative cooling. Your skin has to stay at 95 or below to maintain normal internal temperature. Looks at temperature, humidity, wind speed, sun angle, and cloud cover.
WBGT=0.7TW+0.2TG+0.1TD
Tw is the wet bulb temperature, which indicates humidity
Tg is the globe temperature, which indicates radiant heat
Td is the ambient air (dry) temperature
Dangerous Wet Bulb Globe Temperatures
80-88 degrees Farenheit (30-45 minutes in sun puts body in serious stress).
>88 you can only work/exercise 20 minutes before danger
Above 90 can only be active for 15 min. “
Risk Levels of Heat Illness:
<65 = low risk
65-75 = moderate risk
73-82 = high risk
>82 = very high risk
Recommend cancelling event c WBGT > 82.4
Categories of exertional heat illness?
- Exercise-associated muscle cramps
- Heat syncope
- Heat exhaustion
- Exertional heat injury
- Exertional heat stroke
Exercise-associated muscle cramps
Most common heat-related condition. Thought to be due to hydration and sodium loss but not always. Can be due to overzealous effort though. Most common in 2 joint muscles.
Educate the athlete to talk to you when they feel fasciculations prior to the cramp. Have them stretch (you stretch them) until it calms, give them a break/get out of heat, massage the area, and give them water or some sports drink (with sodium and carbs). The fluid/electrolytes will prevent subsequent cramping but not effective for acute treatment. In severe cases or when symptoms rebound, intravenous hydration with 0.9% normal saline is indicated, this is often rapidly curative.
Heat syncope?
Happens often with people on their feet prolonged periods in heat. Often happens when athlete stops exercising and stands still (loss of muscular contraction reduces venous return). There is orthostatic hypotension and venous pooling (CV method to increase heat loss). Early signs are feeling dizzy, fatigued, hot/clammy. Sometimes they may collapse. Need to differentiate this from heat stroke or heat exhaustion (to differentiate, these athletes will have little or no elevation in body temperature). Treat with shade, elevate legs, cool them, rehydrate.
Heat Exhaustion?
Athlete has increased body temperature (stays below 104 mark where heat stroke occurs). Demonstrate signs of severe fatigue (performance decreased) and maybe:
Dizziness, malaise, nausea, vomiting, headache.
Associated signs: flushed, profuse sweating, cold clammy skin
No signs of CNS dysfunction (irritability, consciousness, attitude, psychological issues). Exhaustion is a great word for it, they can no longer perform as they were. Treatment: take their temperature (rectally is the only way to check internal temperature accurately). Need to get them cooled off to 100.9, drink cool fluids, fan them. No harm to cool them down faster with total body immersion. Aggressive cooling continues until temperature reaches normal.
Exertional Heat Injury
Core body temperature goes above the 104/105 mark but not showing signs/symptoms of any CNS dysfunction. You can start to see organ failure and tissue damage.
Acute Exertional Rhabdomyolysis
Destruction of skeletal muscle with leakage of myoglobin and muscle enzymes into the vascular system. Can happens during intense exercise in hot/humid environments. Will see very dark colored urine with this, if that’s the case they need to get to the ER immediately. These proteins have to be handled somewhere and they’re filtered by the kidney and if there is too much of it it blocks the filters in the kidney and the fluid can’t get through. You’re not able to make urine and you’re accumulating waste products. Aggressive hydration and simultaneous diuresis needs to be performed to support renal function.
Exertional Heat Stroke
Thought to be number 1 cause of death of athletes in summer. Usually these individuals will collapse but if they haven’t then you’ll see CNS changes (personality, irritability, agitated, decreased consciousness, trouble formulating sentences). Temperature over 104/105. Need to get them cooled, ice water/bath (even with their equipment on). Need to lower temperature to 102 within 30 minutes. If not available, can coat them with towels (ice water soaked), fan then, dump water on them. Skin may be dry/hot but sometimes there still may be some sweat from earlier times or from equipment (usually you’ll see dry/hot skin during classic heat stroke vs exertional heat stroke).
Return to Sport After Heat Stroke?
Need to be medically cleared. May be able to begin moderate activity in about a month. Will likely have residual symptoms. Must be asymptomatic with blood work.
Risk factors for heat illness?
- Have they had it in the past
- Were they doing some offseason workouts and exercising
- Ease them into the heat
- Need water breaks (coaches shouldn’t restrict this)
- Not resting/recovering/hydrating/eating between multi-day practices
How do you rule out cardiac causes with symptoms of heat illness?
Rule out cardiac causes (increased respiration, increased HR, chest pain, pain going down arm).
Human physiology in cold conditions?
- Exercise increases metabolism and increases heat
- As we get fatigued we produce less heat
- Shivering then occurs with small decrease in body temperature (can increase heat production up to 5x normal)
- Shivering stops when our body temperature goes below 90 degrees
- Death becomes imminent if body temperature goes below 85
Hypothermia?
Decrease in core body temperature.
Mild Hypothermia
- 89.6 -95
- Lethargic / amnesia
- Shivering (leads to impaired fine motor)
- Pale
- Runny nose
Moderate Hypothermia
- 82.4-89.6 degrees body temperature
- Shivering now stops
- Skin gets very cold (maybe hard)
- Cyanosis
- Decreased respiration and pulse
- Impaired gross motor
- Impaired mental function
Severe Hypothermia
- Below 82 degrees
- May have passed out at this point
- May go into cardiac arrest
- Bradycardia, decreased respirations
- Very low blood pressure
How To Respond To Hypothermia
Primary: Assess cardiac Risks
Secondary: Assess core temperature and monitor vital signs
Rewarming: If you start to warm them, you have to ensure you keep them warm (don’t start if they’re going get cold again because they’ll be at immediate risk of cardiac arrest). Remove any cold or wet clothes, replace with dry. Use heaters, blankets, warm drinks. Don’t use immersion (could cause after drop). Need to warm their core first (to prevent afterdrop).
What is afterdrop
Your body will shunt off it’s extremities first (vasoconstriction) to maintain its core body temperature first. So if you rewarm the extremities first you force vasodilation so that cold blood in the extremities is going to make its way back to the heart. That can then further drop the core body temperature and cause cardiac arrhythmias and even death. Don’t want to do warm-water immersion because remarking the vasoconstricted skin could lead to afterdrop.
Freezing Injuries
Categorized by depth of injury. Ice crystals form in the cells of the body. Usually starts in the extremities and progresses proximally. Once again, once they warm up they shouldn’t go back out that same day.
1. Frostnip
2. Mild frostbite
3. Severe frostbite
Frostnip
Most superficial layer of skin effected. Skin can get very red and burns.
Mild Frostbite
Freezing of the skin and adjacent subcutaneous tissue. Skin appears pale and hard, cold to touch. When pressing harder it should yield (deeper layers not frozen). Patient has hard time moving area. DO NOT RUB THE AREA (can further damage the area). Take off cold clothing, try to rewarm the area. Can use warm immersion, don’t use hot.
Severe Frostbite
Frozen skin/subcutaneous tissue and even tissues below (muscle, tendon, or bone). Skin is hard and cold and won’t yield to pressure. They won’t be able to move the area. Blisters will often be present and skin may be gray, black, or purple. Likely going to have muscle, tendon, and joint damage. Can do immersion in warm water but they will have a lot of pain when the area rewarms. May develop gangrene.
Non-Freezing Injuries
Usually the tissue is cold and wet for multiple hours or days. Usually requires longer periods than freezing injuries. Chilblain or trench foot.
Chilblain
Usually in the fingers and toes. Exposed to wet, cold environment for multiple hours. Skin gets red, swollen, tingly, painful.
Trench Foot
Requires up to 12 hours to days of cold, wet exposure. Skin will look wrinkly, blistered. May effect nerves and blood vessels as well.
Treating Non-Freezing Injuries
Remove anything cold/wet. Get them to a warm area. Use heaters or blankets. Rewarm in warm water. Keep thawing until tissue feels normal/pliable.
