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Human body when working at a fully functional level has the capacity to maintain a balance between heat gain and heat loss, to keep the core body temperature within the range of 36.1 to 37.8 °C(Golsling et al .2010).During marathon Jenny's body temperature changed because of deflected balance between metabolic heat production and exchange with environment. When body's thermal balance disturb, body temperature in the core or skin will change. Peripheral (skin) and brain spinal column thermal receptors provide alternative signals to hypothalamic thermoregulatory center where this information continue until the sufficient heat balance is achieved and prevent further change in body temperature (Kenific et al. 2007).In normal thermoregulation process, body temperature increase the thermostat in hypothalamus activate cooling system and due to this vasodilatation occur then the capillaries fill up with the warm blood and heat radiate from skin surface as well as activate sweat gland to enhance evaporation cooling so body temperature reduce.
Heat loss mainly from the human body through conduction (the amount of heat through a substance directly that have differing temperature), convention (heat energy is transferred by the circulation of the air) Evaporation (The process that the heat loss occurs by sweating and water loss (Wendit et al.2007) Radiation(receives heat from objects around it via radiation from object are warmer: exposure to the sun during exercise. Jenny's thermoregulatory mechanism failed because of increased heat loss (Bouchan et al. 2007).Conduction, convention and radiation failed because the thermal grade of the surrounding environment and Jenny's body temperature was same. During the high hot and humid evaporation failed and if the humidity is high evaporation of the sweat cannot happen because the vasodilatation and sweating which take place due to loss of heat.
Q2. Look at Jenny's signs and symptoms.What is happening to her normal physiological processes to produce these ie why is her BP low and heart rate high?Why are her respirations rapid and shallow? Why did she feel dizzy and nauseous?
Jenny got the hyperthermia because of the failure of heat loss mechanism such as convection, radiation conduction, evaporation and peripheral vasodilatation. The skin become hot due to the increased vasodilatation that caused increased blood supply to skin and sweat gland .In Jenny condition heat production take more because of the increased physical activity, increased metabolic rate and increased heat gain from surrounding(Casa et al.2000).Excessive heat production and decreased heat loss causes for the increased temperature in body. High body temperature leads to increased peripheral vasodilatation in an attempt to loose the heat that causing for the reduced peripheral resistance due to this decrease the venous return. As a result of decreased venous return decline the amount of cardiac out put and it causing for the hypotension. Moreover, reduced cardiac out put leading to low blood flow to the lung and finally patient get hypoxia, due to hypoxia stimulation of the chemo receptors happened and it stimulate the sympathetic nervous system .Stimulation of the sympathetic nervous system will lead to release of the adrenaline and nor adrenaline, it combines with β cells in heart which will stimulate the SA node which cause tachycardia.
Heat stress provoke thermoregulatory and heat shock reaction. Active coetaneous vasodilatation and vasoconstriction allow the shift of heated blood from central organs to the periphery, from which heat is then degenerated to the environment . Heat stroke increases the blood temperature and initiates thermal sweating. Thermal sweating resulting from excesses temperature that is preserved by the body(Doyle et al.2005) .Blood is shunted from the central circulation to the muscles and skin to assist heat dissipation. Generous salt supplementation facilitate the thermoregulation because through the sweating Jenny loosing salt and water from the body (Buchanan et al.2002) . Maximal sweat rate during exercise in hot condition ranged from 900ml/h to2000ml/hr it is depending upon the heat acclimatization with typical rate between 1000ml/h and 1800ml/h. Sweat contains Nacl(Sodium chloride)Urea, Aminoacid, Water, Proteins(Godek et al. 2008).
The drop in thermoregulatory function that accompanies function dehydration clearly increase the risk of heat related problems.The least resource of this disease is heat syncope which is likely related to acute cutaneous vasodilatation and related drop in central venous pressure, it lead Nausea and vomiting to Jenny(Verstappen et al .2007).
Q3.What step Jenny have taken to avoid heat stroke?
The most important objectives in the heat stroke is prevention, therefore maintenance of body temperature within a normal range is very important. For the deterrence of the heat stroke Jenny should have taken certain steps.
Jenny should have gone for physical examination to check her body's fitness for participation in marathon (casa et al.2000). During exercise, Dehydration is related with an increase in core body temperature and cardiovascular strain and a decrease in stroke volume and serum sodium levels. These imbalances can increase the risk of heat syncope, heat exhaustion, and, most seriously, heat stroke. Through the proper hydration and fluid replacement Jenny can perform optimally and maintain overall health.(Volpe et al .2009).
Jenny lost water through sweating so plenty of fluids can help in maintaining fluid and electrolyte balance and can help to prevent the stage of dehydration (Volpe et al .2009).
She should wear light colored clothes as light color absorbs less amount of heat. Use only loose clothing for the free air entry to the body to some extent it assists to cool the body by convection method (Danial et al .2008). Jenny can acclimatize herself by coming at least one or two week earlier at New Delhi and practice out door activities before for some time to acclimatized her body in that hot and humid environment(Smith et al. 2005) .Acclimatization is the reversible process by which a person becomes adapted to a change in the environment . Acclimatization helps Jenny's to prevent decreased blood circulation during exercise, reduction of plasma volume, lower sweat rate and her body gets the resistens in New Delhi environmental condition. (Smith et al. 2005).
Q4.What treatment Jenny would require?
Effective heat dissipation depends on the rapid transfer of heat from the skin to the external environment. There are various types of cooling method can use for reduce the heat strocke.
Use of water cooled garments.
Wet towel and ice pack application.
Air cooling or the fanning of the body
Ice and cold water immersion.
At the first step, shift Jenny to dark cool shelter because this can be helpful in losing heat from body to environment through convention and radiation method Conduction is the transfer of heat from one molecule to another through a substance. Heat energy transferred between a surface and a moving fluid at different temperatures is known as convection. (Beinkly et al. 2002).
Allow her to lie down in on cold surfaces this will help to reduce hyperthermia by conduction and it refers to the transfer of the heat from one surface to the another surface in different temperature with the direct contact. The heat is transferred from the hot body to the cold body moderately through this method ( Carla et al. 2006). Loose her clothing and give enough air circulation by fans and rotating towels as it help to reduce temperature by convection ( Mc Dermott et al. 2009). Immersion of cold water is another commonly used method for reducing body temperature but there are conflicting suggestions regarding this as cold may lead to vasoconstriction that can limit heat loss ( Smith et al. 2005).But in Jenny case she is unconscious so after further treatment this method can use. Jenny body would need to replace the electrolyte such as sodium and sports drink. Hydration during prolonged activity will also maintain circulation of blood volume to promote heat exchange and sweating.(Roberts.2008).
Jenny had profuse sweating during marathon through this, dehydration occur so I.V. fluids should be started with cold saline to hydrate her, as she is not capable of taking water orally .When she starts tolerating oral replacement, provide lots of cold water or sport drinks. This will decreases the chance of dehydration and supply electrolytes which loss through sweat and prevents hypovolemia, hyponatremia and hyperkalemia (Bouchama et al.2007).