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Turning down the heat (Heatstroke (Body temp greater than 40C, Heat…
Turning down the heat
Heatstroke
Body temp greater than 40C
Heat exhausution is precursor to heatstroke
Avoidable by drinking water and avoiding excessive heat and humidity
Main cause of heat exhaustion is dehydration
Heat exhaustion symptoms: tiredness, dizzinness, faintness, drop in blood pressure, headache, muscle cramps, nausea, heavy sweating, intense thirst, fast pulse, dark urine
Thermoreg being overwhelmed by heat prduction, environmental heat and lack of heat loss
Two types of heatstroke: exertional and non-exertional *e.g. ecstasy and alcohol
;Cures: lie down in cool place, remove clothing, water and fanning, drinking water, immersion in ice bath
Symptoms for heatstroke: confusion, dizziness, disorientation, seizures and loss of consciousness
Pathophysiology: concentration of IL-6 positively correlated with the severity of heatstroke. Excessive heat results in proteins being denatured, phospholipids and lipoproteins are destabilised. Membrane lipids liquefied.
Dehydration
Net water loss and dysfunction of mineral balance
:Early symptoms: thiirst, lightheadedness, dry mouth, tiredness, dark -coloured, strong-smelling urine. At this point it is reversible by drinking more fluids
2 types: one involves only water loss, other water and salt loss
Later symptoms: thirst, dizziness, headache, lethargy, dry mouth/lips/eyes
Treatment: water or lemon juice (stimulates salivation) and oral rehydration solutions if mild. IV or nasal tube
Thirst and dark urine is to increase water intake and reduce water loss
Drinking alcohol increases water loss
Major cause of heat exhaustion and hypernatremia
WHO classification of dehydration
No dehydration: not enough signs to classify as either other
Sme dehydration, 2+ from: restlessness, irritability, sunken eyes, drinking eagerly, thirst, skin pinch goes back slowly
Severe dehydration, 2+ of: lethargy, unconsciousness, sunken eyes, unable to drink/drinks poorly, skin pinch goes back very slowly, more than 2 seconds
Chronic dehydration can decrease kidney function, increasing risk of stones. Also leads to muscle damage and constipation
Fluid regulation
Blood volume proportional to blood pressure, which can be measured by baroreceptors in aorta. HBP leads to vasodilatiton, espec in glomeruli, resulting in increased water in urine
Water intake regulated b thirst. triggered by receptors in anterolateral hypothalamus that react to increase in plasma osmolality or decreased body fluid volume
Main players are ADh, aldosterone and angiotension II
Angiotensin II made by conversion of angiotensin by ACE> it si a vasoconstrictor, activating Na+/H+ antiports in proximal tubule to increase Na+, Cl- and H20
RAAS system involved in electrolyte reabsorption and ADH system for water reabsoprtion
Stretch receptors in aorta and carotid, stimulated when BP falls and stimulate ADH secretion, as do special receptors in hypothalamus, sensitive to increasing plasma osmolarity. Stretch receptors in atria are activated by larger than normal volume of blood returning to heart inhibit ADH secretion.
ADH increases water permeability of principal cells in last part of collecting duct and distal tubule. Does this by inserting proteins that function as water channels in apical membrane. Basement membrane is relatively permeable to water anyway.
ADH also regulates facultative transport of water
Atrial natriuretic peptide (ANP) synthesised in atria, and released in response to atrial distension. Increases GFR and decreases sodium reabsorption. Opposes RAAS, suppresses aldosterone
Thermoregulation
Humans lose heat by conduction, convection, radiation and evaporation
Keeps body temperature around 37C
Cooling down: sweat which cools when it evaporates (not during penguin effect), arrector pilli, relax to crate thin layer of insulation, vasodilation. Glands stop secreting adrenaline and thyroxine
Alcohol and drugs themselves have a cooling effect
Controlled by hypothalamus
Thermoreceptors are free nerve endings with receptive fields in the skin. Different receptors for hot and cold
Alcohol, drugs and dehydration
Alcohol decreases ADH production, reducing reabsorption of water. Also causes vomiting, which decreases fluid volume and electrolyte levels
Festival drugs
Cocaine
Speed (amphetamines)
All 3 are stimulants, which can raise body temperature and cause overheating/dehydration
Ecstasy
The less you weigh, the less alcohol it takes to cause dehydration. Recommended people do not drink more than 4 drinks on any occasion
As blood alcohol levels decrease, ADH levels decrease. unknown why
Conditions affecting electrolyte balance
Main electrolytes are Ca2+, Cl-, Mg2+, phosphate, Na+ and K+
Can cause irregular heartbeat, fatigue, headaches and tiredness.
Hypernatremia (over 145mmol/L) is most likely. Can be caused by sweating
Relevant causes: lack of water, sweating, vomiting and consumption of diuertics e.g. alcohol and stimulants
