Exertional Heat Illness, Sickling, & Hyponatremia

causes of HEAT CRAMPS (not a medical emergency but common)

large losses of water and sodium via sweat in addition to copious consumption of water and/or neuromuscular (NM) fatigue

s/sx of HEAT CRAMPS

involuntary spasms of skeletal muscles, usually during or after exercise

tx of HEAT CRAMPS

consumption of salty foods (EX:electrolyte drinks if cause is from sweat), stretching (if cause is from NM fatigue)

causes of HEAT SYNCOPE (not a medical emergency but common)

standing in a hot environment for a long period of time and/or immediately upon cessation of exercise

* most common environments = military cadets, sports that require heavy equipment

s/sx of HEAT SYNCOPE

fainting caused by postural pooling of blood in legs/loss of vascular resistance

tx of HEAT SYNCOPE

place pt in supine position with legs elevated at least 12 in. above heart to promote venous return in a cool environment and provide fluids if needed

* important to keep walking, dynamic stretching to continue blood flow and avoid decrease of venous return and blood pressure
* RTP can occur when vital signs are restored

causes of HEAT EXHAUSTION (not a medical emergency but common)

fluid-electrolyte imbalance leading to CV insufficiency

s/sx of HEAT EXHAUSTION

inability to continue to work/exercise in the heat, nausea, vomiting, dizziness, difficulty catching breath, headache, fatigue

tx of HEAT EXHAUSTION

rest and restoration of fluids and electrolytes

* RTP timeline AT LEAST a 24-48 hour period

What are the top three causes of sudden death in sport during JULY-SEPTEMBER?

1. sudden cardiac death
2. exertional heat stroke
3. exertional sickling

what sport population is commonly plagued by EHS and exertional sickling

collegiate conditioning sessions, high school football pre-season practice

Exertional Heat Stroke

occurs when core body temperature is elevated to a dangerous level, usually above 105 F (40.5 C), with concomitant signs of organ failure due to hyperthermia

* death can occur if not treated immediately and effectively

pathophysiology of EHS

occurs when thermoregulatory mechanisms are unable to dissipate the heat being gained and produced by the body

Heat Balance Equation

S = M - (±Work) + E ± R ± C ± K

How can conduction (K) affect the heat balance equation?

HEAT GAIN: equipment, feet in contact with ground

How can radiation (R) affect the heat balance equation?

HEAT GAIN: outside in 85 F while sunny

convection (C) in heat balance equation

most effect; air movement, works together with evaporation

HEAT LOSS IN BALANCE EQUATION: windy weather VS no wind in 90 F weather

evaporation (E) in the heat balance equation

most effect; works together with convection

HEAT GAIN: if sweat is just dripping off the body, there will be NO heat loss.

* sweat MUST be EVAPORATED off the body by surrounding air (convection) to lose heat

Why are athletes more at risk for EHS in high humidity?

the air is super saturated with water which means sweat can't evaporate

pre-optic area of anterior hypothalamus (PO/AH)

very specific part of the brain responsible for temperature regulation

* activates heating and cooling mechanisms when body is hot or cold
* hot = vasodilation and sweating
* cold = vasoconstriction and shivering

set point for temp. regulation (Tc)

98\.6 F / 37 C

when Tc is above 37 C, which response is initiated by the PO/AH?

HEAT LOSS responses initiated

when Tc is below 37 C, which response is initiated by the PO/AH?

HEAT GAIN responses initiated

thermoregulatory physiology during maximal exercise in the heat

body mitigates hyperthermia = increased skin blood flow and sweat rate

muscular physiology during maximal exercise in the heat

body rises to the metabolic challenge = increased blood flow to muscles

* blood flow competing between skin and muscles to fuel exercise

cardiovascular system during maximal exercise in the heat

increased cardiac output (Q) to meet demands of exercise

* can NOT meet maximal demands of all systems = BP maintained at expense of other vital signs as long as everything else is ‘fine’

intrinsic risk factors of EHS

high intensity of exercise, dehydration, inadequate heat acclimatization, current illness, intensity unmatched to athlete’s current fitness status, etc.

extrinsic risk factors of EHS

exercise intensity, high environmental conditions (= hotter temp = more predisposed but does NOT have to be hot outside for someone to get heat stroke), work to rest ratio, uniform/equipment, hydration, no EAP, delay in recognition

intensity of exercise with respect to EHS

greatest influence on rate of core body temperature increase

heat acclimatization with respect to EHS

method of minimizing the physiological strain associated with exercise in the heat

* complex series of adaptations occurring in a controlled environment over the course of 7-14 days
* reductions in: HR/general CV system, core and skin response, RPE, NaCl losses in sweat and urine, body will learn to retain some sodium
* increases in: sweat rate and onset, stroke volume, exercise performance in heat, plasma volume

heat acclimation

going through process in a non-natural environment

* EX: heat lab with controls that can be set

heat acclimatization

process in the natural environment, outside in the elements

dehydration and it’s effects on thermoregulation

DECREASE

* sweat rate at given core temp
* skin blood flow at given core temp
* max. sweat rate and max. skin blood flow

\
INCREASE

* core temp at which sweating begins
* core temp at which skin blood flow begins
* core temp at given exercise intensity

clinical dehydration is defined as…

as little as 2% body mass loss (BML)

mild dehydration is defined as…

less than 2% BML

moderate dehydration is defined as…

between 2-4% BML

* results in CV and thermoregulatory compromises and decrease in performance

severe dehydration is defined as…

above 4% BML

s/sx of dehydration

thirst, headache, dizziness, lethargy, irritability, cramping

* FLUID INTAKE SHOULD = FLUID LOSS

immediate post collapse symptoms of EHS

\*\*must be present to be diagnosed as EHS

* core body temp > 105 F taken via RECTAL THERMOMETER
* CNS dysfunction = disorientation, irrational, aggressive, loss of balance or motor function, loss of consciousness

assessment of body temperature for EHS

RECTAL IS THE MOST ACCURATE AND ONLY WAY TO ASSESS FOR EHS

tx for EHS

ICE WATER IMMERSION = GOLD STANDARD

* victim should be cooled to 102 F within FIRST THIRTY MINUTES after collapse
* water should be 50-60 F
* continuously monitor core body and water temp, vital signs (BP & HR), keep water moving (affects temp. gradient thru convection)
* COOL FIRST, TRANSPORT SECOND

sickle cell trait

considered generally benign; condition from inheriting one gene for normal hemoglobin (A) and one gene for sickle hemoglobin (S)

* CONDITION not a disease

Exertional Sickling

medical emergency that occurs when an athlete with SCT experiences the sickling of red blood cells

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sickling can begin w/i a few minutes of sustained, intense exertion or successive bouts of maximal exertion with little or no rest. RBCs then logjam/block blood vessels, not allowing for oxygen to pass throughout the body from the blockage point

potential controversy with being able to defer SCT testing at the NCAA level

athlete may defer SCT testing at the intercollegiate level bc they feel they may be discriminated against by situations like coaches not wanting to be responsible for athlete so don’t give game time

s/sx of Exertional Sickling

pain in muscle groups associated with ischemica, inspection and palpation will show NO abnormalities to muscles, tight chest muscles/”can’t catch my breath”/increased HR in INITIAL vital sign check

how is Exertional Sickling CRAMPING different from Heat CRAMPS?

In EXERTIONAL SICKLING CRAMPING, quads, hamstrings, glutes, and low back most commonly affected. Leg WEAKNESS, cramps that “spread up my body”

how is heat cramps different from Exertional Sickling cramps?

gastrocs and abdomen most commonly affected, usually described as a sharp, shooting pain. cramps will be observation and palpable

when are Exertional Sickling symptoms likely to occur?

during intense workouts, altitude and in the heat

what is the #1 predisposing factor of exertional sickling?

exercise intensity