Assessment of the collapsed runner

ABCDEFGH

Airway

Breathing

Circulation

Disability (Mental Status)

Environment (Rectal Temperature)

Fluid status including change in body weight

Blood Glucose and Sodium

History including site of collapse

Collapse during exercise (Common medical causes)

• Cardiac arrest

• Hypoglycaemia

• Anaphylaxis

• Other medical conditions

• Trauma/Orthopaedic injuries

Collapse during exercise (exercise related causes)

• Heatstroke

• Hypothermia

• Exercise-associated hyponatraemia

• Exercise-associated postural hypotension

Most common cause of collapse Presents after the finish

Exercise-associated postural hypotension

Exercise-associated postural hypotension definition

“The inability to stand or walk unaided as the result of light headedness, faintness, dizziness or syncope”

• Postural hypotension related to cessation of activity

EAPH field management

• Place runner supine and head-down
• Oral fluids

Hyperthermia

Hyperthermia is high rectal temperature (usually >40oC) in an

athlete who, other than feeling exhausted, is usually well.

Exertional Heatstroke

• Symptoms or signs of organ dysfunction
• And a core body temperature >40oC

39-40oC is considered ...

is a normal physiological response to intense exercise or physical activity

Heat gain in exercise

Endogenous heat production: muscle activity and metabolism

+

Exogenous heat absorbtion: environmental

Heat loss in exercise

In low environmental temperatures, heat is lost through:

Convection + Radiation + (Small contribution from conduction)

Increasing environmental temperatures:

sweating = effective heat loss through evaporation

In Humid conditions:

evaporation is reduced > ineffective cooling

Athlete is unable to lose heat > begins to overheat

Heatstorke effects

Cerebral hyperthermia:

• hypothalamic failure and loss of thermoregulatory control
• Rhabdomyolysis
• renal failure
• hyperkalaemia

Intense inflammatory response:

Inflammatory cytokines trigger a systemic inflammatory response (SIRS):

• tissue hypoxia
• metabolic acidosis
• Acute kidney injury
• Acute liver failure
• Acute hypotensive shock
• Multi-system organ failure

third leading cause of death in athletes

• EHS
• Mortality and prognosis is largely dependent on early recognition and prompt management

Heatstroke: Field management

• Cold water immersion is the most effective cooling modality
• Shade, strip, spray and fan (S3F) is recommended where CWI is contraindicated or not possible

What is Exertional Heat Illness (EHI)

Pathophysiological continuum from mild symptoms (fatigue, headache) to collapse, coma and death because of a rise in core temperature

What is “Heat Exhaustion”

a physiological response to inadequate acclimatisation

What is “Heat cramps”

a physiological response to inadequate training

What is Exercise-associated hyponatraemia

[Na+] <135 mmol/L1

dilutional hyponatraemia occurring during or <24hr after exercise

EAH: pathophysiology

Relative hyponatraemia in the vascular compartment causes an osmotic fluid shift into adjacent tissues

EAH symptoms

Cerebral edema

• agitation
• LOC
• confusion
• Drowsiness
• stupor

GI symotoms

• nausea
• vomiting
• diarrhea

Other

• Headach

EAH causes

Excessive fluid intake

• Excessive consumption irrespective of fluid type

Reduced fluid output (Altered renal function)

• Exercise ( RBF and GFR fall by 40% after exercise)
• ADH (0.5 pg/mL) in 43 % of cases
• NSAIDs ( Indomethacin, and celecoxib significantly reduced free water clearance)

EAH: who is at risk?

• Females
• slower runers
• >4hrs exercise time

EAH: Field management (Asymptomatic)

● Observe closely

● Salty snacks or salty broth

● No oral fluids until onset of urination

● No iv fluids

EAH: Field management (Symptomatic)

● Oxygen

● 100ml bolus iv 3% Hypertonic Saline

● May require hospital admission

EAH: Hospital management (Symptomatic)

● Check and treat [Na+] before imaging

● Use 2.7% or 3% Hypertonic Saline

● AVOID Normal Saline

EAH: Prevention

1. Drink according to thirst: ad libitum

2. Avoid excessive drinking during and after exercise

3. Sports drinks do not prevent EAH

4. Sodium supplementation does not prevent EAH

Variation in human water turnover associated with environmental and lifestyle factors.

• age
• sex
• FFM
• Body weight
• PAL
• athletes
• HDI
• Air temprature
• Humidity
• Altitiude

EAH: drinking myths

1. We need to drink 2 liters of water a day

2. Sports drinks prevent EAH

3. Thirst is imperfect

Metabolic water

• The energy cost of running a marathon for an average

70 kg male is roughly 12,000 kJ (4.18 kJ·kg−1·min−1).

• Estimates of carbohydrate oxidation indicate that an

elite male runner would utilise 400 g of glycogen

• given the accepted value of 3 g of water per gram of

oxidised glycogen, this would result in a 1200 mL

endogenous water release