Exertional, which is a more common occurrence among young, healthy,
fit athletes exercising in hot and humid environments. RUGBY AND HEATSTROKE
PRESENTATION
Players may complain of non-specific symptoms such as
rapid pulse rate, shortness of breath, weakness, headache, nausea and vomiting.
More often the condition presents abruptly with abnormal behaviour, muscular pains
or even seizures or coma.
Unlike people with classical heatstroke, exertional
heatstroke victims are almost always still sweating.
In South Africa the potential
for developing Heatstroke during certain times of the year is great. During the
summer months in most parts of this country temperatures are above 28° C and in
some areas humidity reaches over 70% setting the scene for this potentially fatal
but preventable catastrophe.
There are certain aspects of Heatstroke applicable
to rugby that need to be considered:
1. The metabolic rate rather than the
level of dehydration determines the rectal temperature during exercise.
2.
The metabolic rate of the player is determined by his body mass and exercise intensity.
3. The players at greatest risk of developing heat stroke during rugby matches
are the heaviest players who expend energy at high rates. This would mean the
five tight forwards.
4. The converse therefore holds for the back line players.
They are at a lesser risk.
5. A progressive rise in body temperature is detrimental
to performance during rugby matches and is most likely to occur in the five tight
forwards. As a result, a drop in their performance under hot conditions should
not necessarily be attributed to their level of fitness but could be an elevated
body temperature.
6. The taking in of fluids plays a relatively small role
in the prevention of heat stroke but a much larger role in improving sports performance.
ENVIRONMENTAL FACTORS
There are 4 measurable factors, which determine
the level of heat stress imposed by the environment: air temperature; radiant
temperature of the surroundings; humidity; and the amount of air movement. It
is essential that all these be considered in any assessment of the environmental
conditions.
The black bulb, dry bulb and wet bulb thermometers are used to
measure radiant temperature, air temperature and humidity respectively One useful
scale to measure these variables is the WBGT. In a single value it combines the
effects of solar and ground radiation, air temperature, humidity and wind speed.
In rugby it is recommended that caution should be exercised when the WBGT reaches
25°C and that activity be considered unsafe for the poorly conditioned and unacclimatised
when it exceeds 28°C. The American College of Sports Medicines recommends that
no matches be played when WBGT exceeds 28°C.
During the warmer months (February,
March, April and October in the Southern hemisphere) we should schedule our matches
in the evening or late afternoon rather than mid-afternoon. Cancellation of matches
will not be a practical idea. Instead we should be alerted to the dangers of developing
heatstroke when air temperatures reach 28°C and the humidity 70% since obtaining
WBGT readings in certain areas may not be practical.
FLUID INTAKE
The
taking in of fluids plays a relatively small role in the prevention of heat stroke
but a much larger role in improving sports performance. It is documented that
the five tight forwards may lose up to 2litres/hour of fluid during a match, yet
would not be able to replace fluid as quickly by oral ingestion.
The ingestion
of between 500 and 800 mls of fluid per hour by rugby players will suffice to
ensure optimum performance and this should be the goal for a 70 to 90 kg player.
Heavier players may require more.
Fluid absorption into the body is accelerated
if the stomach is kept partially filled during exercise This can be achieved by
drinking 400 to 500mls of fluid immediately before one runs on to the rugby field
and then adding an extra 100mls every ten minutes during the match. In this way,
rugby players could ingest approximately 600mls/hour.
Carbohydrates should
be included in the drink because they increase the palatability of the drink,
as does a small amount of salt and a flavourant. Players will therefore tend to
drink more than they would if they were offered plain water. Thus water is not
the ideal drink for ingestion by rugby players during a match. An appropriate
sports drink as provided by the sponsors would be more acceptable.
MANAGEMENT
All measures must be taken to ensure that the five tight forwards are
kept as cool as possible during matches that are played in hot conditions. This
might be achieved by actively cooling them during the half time break and by substituting
them in the middle of the second half.
Immediate recognition and management
of heatstroke is crucial in view of the high mortality rate. Whenever heatstroke
is suspected and the diagnosis made, the player must immediately be transferred
to a cooler location and cooling methods instituted:
§ Take off clothing after
removing player from the hot environment including direct sunlight.
§ Moisten
skin and fan or alternatively cover with cool wet sheets and keep out of direct
sun. Immersion in cold water is the most effective cooling method but is not often
practical.
§ Apply ice packs to the entire body if no cold bath is available.
This is the optimum form of treatment under most conditions.
The following
points need to be borne in mind when heatstroke has been diagnosed:
§ As always
when a player has collapsed, the on-site attendant should first proceed to ascertain
the presence of a pulse, breathing and a clear airway before instituting cooling
methods.
§ Remember that dehydration is not the cause of heatstroke, it is
a contributing factor. Therefore do not uncontrollably infuse large volumes of
fluid intravenously. If dehydration is suspected rather opt for oral rehydration
§
Cease cooling procedures when rectal temperature reaches 38°C to avoid rebound
hypothermia
DIAGNOSIS
The following criteria must be met before
a clinical diagnosis of heatstroke can be made:
§ Rectal temperature of 40°C
or more.
§ Change in behavioural pattern (from confusion to collapse to unconsciousness)
§
History of intense physical activity
§ Exposure to high temperatures
The
abnormal behaviour could present as irritability, aggression, violence, withdrawal,
confusion and coma. The increased body temperature is as a result of a failure
of one's normal thermo-regulatory mechanisms in the presence of a very high environmental
temperature.
Heatstroke has a high mortality rate. This becomes even greater
in cases that are not diagnosed early or treated promptly in which the mortality
rate should be about 5%.
PREDISPOSING FACTORS:
1. Intensive physical
activity in extremely hot and humid areas
2. Previous episodes of heatstroke
3.
No acclimatization or inadequate acclimatization.
4. Underlying illness e.g.
influenza
5. Drugs e.g. alcohol, stimulants including amphetamines, ephedrine
and cocaine.
6. Overweight
7. Dehydration
8. Lack of fitness
PROPHYLAXIS
1. Acclimatization of 10 to 14 days
2. Adjust physical activity according
to environmental factors (WBGT-Wet Bulb Globe Temperature system)
3. Adequate
fluid intake
4. Apparel should be thin, light coloured garments made of materials
that permit free evaporation and should fit loosely
5. Dietary adjustments
for warm environments
6. Early identification of predisposing factors
7.
Education of players/athletes. Present them with a plan of action should they
be confronted with such a problem
8. All medications to be cleared by team
doctor
9. Vitamin C in doses of 250 to 500mg daily in the area in question
is recommended
2. HEAT EXHAUSTION
Heat exhaustion is usually considered
as the first step towards the development of a fully-fledged case of heatstroke.
But there is no consensus on this view. Like heatstroke, it occurs as a result
of exertion in a hot and humid environment with most of the other factors predisposing
to heatstroke being present. It is often considered to be a case of “cardio-vascular
collapse” The main cause appears to be pooling of blood in the lower limbs causing
postural hypotension.
The body core temperature rises to over 38°C but never
exceeds 40°. These players can often be described as simply not being able to
continue playing any further. They present with a feeling of listlessness, weakness,
headache, nausea, vomiting, dizziness and a rapid pulse. Unlike heatstroke there
is no change in the mental status of these players and their behavioural pattern
remains unaffected.
Management
Treatment consists primarily of removing
the player from the field of play, laying him on his back and elevating the legs.
Often this may be all that is required. Cooling procedures are sometimes necessary
and the giving of fluids should be indicated by the hydration status. Recovery
is often rapid and uncomplicated. However, in more severe cases admission to hospital
for intravenous rehydration is advised.
