HeatstrokeSun StrokeAcute Management and Prevention

Dr. Aidah Abu El Soud AlkaissiBSc Law, RN, BSc, MSc, PhD

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HeatstrokeSun Stroke

Caused by overexposure to sun and extremely high temperatures occurs when the brain fails to control its own "thermostat". Its a life-threatening condition which can cause a casualty to become unconscious within minutes. As well as an unusually high temperature, a casualty may show signs of restlessness, headaches and hot, flushed skin. *

HeatstrokeSun Stroke

The underlying cause of heat stroke is connected to the sometimes sudden inability to dissipate (To drive away) body heat through perspiration, especially after strenuous physical activity *

HeatstrokeSun Stroke

This accounts for the excessive rise in body temperature.

It is the high fever which can cause permanent damage to internal organs, and can result in death if not treated immediately.

Recovery depends on heat duration and intensity. The goal of emergency treatment is to maintain circulation and lower body temperature as quickly as possible. *

Definition

core temperature > 41 C OR - core temp > 40.5 C with anhidrosis (absence or severe deficiency of sweating), altered mental status or both*

Classification

exertional: typically seen in healthy young adults who overexert themselves in high ambient (Surrounding) temperatures or in a hot environment to which they are not acclimatized (To adapt).

Patients sweat normally. - non-exertional (classic): usually affects elderly and debilitated patients with chronic underlying disease. Result of impaired thermoregulation combined with high ambient temperatures. Often due to impaired sweating*

Pathophysiology

Substantial fluid shift from central compartment to periphery. Reversible on cooling - cardiac output increased +++ (3 l/min per C increase in rectal temperature). May fail in patients with limited cardiac reserve - mediators such as endotoxin and cytokines are implicated in the pathogenesis of organ damage in heat stroke - intractable Disseminated Intravascular Coagulation (DIC) is usual mode of death in fatal cases*

Predisposing factors

Increased heat production - hyperthyroidism - exercise - sepsis

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Impaired heat loss -Impaired sweatingDrugs - anticholinergics, anti-Parkinsonian drugs, anti-histamines, butyrophenones, phenothiazines, tricyclics Abnormal sweat glands - sweat gland injury following acute heat stroke, barbiturate poisoning - cystic fibrosis - healed thermal burn salt and water depletion - diuretic induced Hypokalemia

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Impaired voluntary mechanismscoma physical disability mental illness

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Impaired delivery of blood to peripheral circulationcardiovascular disease hypokalemia (decreased muscle blood flow) dehydration

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Others - elderly - high ambient temperature and humidity, poor ventilation - lack of acclimatization - obesity - fatigue - DM - malnutrition - alcoholism

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Clinical features

often little in the way of warning prodrome (An early symptom indicating the onset of an attack or a diseas) prior to development of non-exertional heat stroke (classic heat stroke).

As thermoregulatory mechanisms fail body temperature rises rapidly and patient can deteriorate rapidly from apparent baseline health to coma or an obtunded state *

Clinical features

3 cardinal signs are:CNS dysfunction hyperpyrexia (core temperature >40 C) hot dry skin. Pink or ashen depending on circulatory state. However may be clammy and sweat

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CNS

Direct thermal toxicity causes cell death, cerebral oedema and local haemorrhage - irritability or irrational behaviour may precede the development of either form of heatstroke - confusion, aggressive behaviour, delirium, convulsions and pupillary abnormalities may progress rapidly to coma - decorticate posturing, faecal incontinence, flaccidity or hemiplegia (however focal signs are unusual) *

cerebellar signs, including ataxia and dysarthria (Speech that is characteristically slurred, slow, and difficult to produce (difficult to understand). may be permanent in a few patients. Cerebellum particularly sensitive to heat - hypothalamic damage may exacerbate heat stroke by further impairing sweating and heat loss - LP may show increased protein, xanthochromia (is the yellow discoloration indicating the presence of bilirubin in the cerebrospinal fluid (CSF) and slight increase in lymphocytes*

CVS

- tachycardia - hypotension or normotension with wide pulse pressure - hyperdynamic haemodynamic profile - myocardial pump failure. Myocardial damage and frank infarction frequent even in patients with normal coronaries due to the effect of heat on myocytes and coronary hypoperfusion secondary to hypovolaemia*

ECG of a patient with a core temperature of 40C

dysrhythmias*

Same patient after cooling*

RS

- extreme tachypnoea with RR up to 60/min - crackles and cyanosis late signs of pulmonary oedema - direct thermal injury to pulmonary vascular endothelium may lead to cor pulmonale or Acute respiratory distress syndrome (ARDS)

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Metabolic

Dehydration leading to raised urea and creatinine, and haemoconcentration - sweating leading to low levels of Na, Mg, K, early in the illness. Hypokalaemia decreases sweat secretion and therefore exacerbates the condition - rhabdomyolysis resulting in hyperkalaemia, hypocalcaemia and renal failure - metabolic acidosis and respiratory alkalosis common.*

RhabdomyolysisA condition in which skeletal muscle cells break down, releasing myoglobin (the oxygen-carrying pigment in muscle) together with enzymes and electrolytes from inside the muscle cells. The risks with rhabdomyolysis include muscle breakdown and kidney failure since myoglobin is toxic to the kidneys.*

Hyperthermia alone can cause primary hyperventilation and respiratory alkalosis, while hypoperfusion, tissue hypoxia, and anaerobic metabolism may lead to lactic acidosis with respiratory compensation. Former less common. *

RenalSome renal damage occurs in nearly all patients as a direct result of heat potentiated by dehydration and Rhabdomyolysis acute renal failure 5-6 times more common in patients with exertional heat stroke in whom it occurs in 30-35%

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Splanchnic

Ischaemic intestinal ulceration common. May lead to haemorrhage

Hepatic damage common. In 5-10% hepatic necrosis may be severe enough to cause death

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Haematological

Anaemia and bleeding. Result from: direct inactivation of platelets and clotting factors by heat liver failure unexplained decrease in platelets and megakaryocytes (The source of blood platelets)platelet aggregation due to heat DIC. Due to activation of clotting cascade by damaged vascular endothelium. Latter may be damaged as a direct result of heat

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Investigations

temperature - electrolytes, urea, creatinine, calcium - LFTs - CPK - ABG: note that Paco2 and Pao2 will be falsely low and pH falsely elevated if results are not corrected for temperature - ECG and ECG monitoring - urine output - FBC, clotting, fibrinogen, FDP, D-dimer. Anaemia frequent. Platelets low/normal. Lymphocytosis - test urine for myoglobin*

Symptoms of Heatstroke or Sunstroke

Headache, nausea, dizziness Red, dry, very hot skin (sweating has ceased) Pulse-strong & rapid Small pupils Very high fever May become extremely disoriented Unconsciousness and possible convulsions

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If exposure to heat continues, the body temperature rises and heatstroke may develop, causing symptoms such as:1.Cessation of sweating 2. Body temperature of 105 degree Fahrenheit or higher 3. Rapid and shallow breathing 4. Rapid heartbeat 5. Elevated or lowered blood pressure 6. Confusion and disorientation 7. Seizure 8. Fainting, which may be the first sign in older adults*

Left untreated, heat stroke may progress to coma. Death may result due to kidney failure, acute heart failure, or direct heat induced damage to the brain.

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First Aid for Heatstroke or Sunstroke

HEATSROKE IS LIFE THREATENING! Remove victim to cooler location, out of the sun Loosen or remove clothing and immerse victim in very cool water if possible If immersion isn't possible, cool victim with water, or wrap in wet sheets and fan for quick evaporation Use cold compresses-especially to the head & neck area, also to armpits and groin *

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First Aid for Heatstroke or Sunstroke

Seek medical attention immediately--continue first aid to lower temp. until medical help takes over

Do NOT give any medication to lower fever--it will not be effective and may cause further harm

Do NOT use an alcohol rub

It is not advisable to give the victim anything by mouth (even water) until the condition has been stabilized.

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Once in the hospital, an examination is done, and blood tests are carried out to assess the level of salts in the blood.

Treatment of heat stroke is usually carried out in a critical care unit.

The body temperature is lowered by sponging the body with tepid water or loosely wrapping the person in a wet sheet and placing him or her near a fan.

Intravenous fluids are given.*

Once the body temperature has been reduced to 100 degree F(38 degree), these cooling procedures are stopped to prevent hypothermia (below) from developing.

Monitoring is still carried out continuously to make sure that the body temperature returns to normal level and that the vital organs are functioning normally*

In some severe cases, mechanical ventilation may be required to help breathing.*

when temperature approaches 39 active cooling should be terminated as the body temperature will continue to fall 1-2 C - chlorpromazine 10-50 mg IV 6hrly may be useful in preventing shivering - use of dantrolene controversial. Probably should not be used routinely at present.*

DantroleneA skeletal muscle relaxant, used as the sodium salt in the treatment of chronic spasticity and the treatment and prophylaxis of malignant hyperthermia (Malignant hyperthermia is an inherited disease that causes a rapid rise in body temperature (fever) and severe muscle contractions when the affected person receives general anesthesia *

Some medicines can put the patient in danger of heatstroke.

Allergy medicines (antihistamines) Cough and cold medicines (anticholinergics) Blood pressure and heart medicines Alpha andrenergics such as midodrine (one brand: ProAmatine) or pseudoephedrine (one brand: Sudafed) Beta blockers Calcium channel blockers Diet pills (amphetamines) Irritable bladder and irritable bowel medicines (anticholinergics)

Laxatives

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Some medicines can putthe patient in danger of heatstroke.

Mental health medicines Benzodiazepines such as clonazepam (one brand: Klonopin), diazepam (one brand: Valium), chlordiazepoxide (one brand: Librium) Neuroleptics Tricyclic antidepressants

Seizure medicines (anticonvulsants) Thyroid pills Water pills

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SupportiveIV volume replacement. Note that many of these patients only require 1-1.2 l of replacement fluid - if inotrope required dobutmine probably drug of choice - urgent treatment of hyperkalaemia - do not treat hypocalcaemia per se; only give calcium if ECG changes of severe hyperkalemia occur as calcium may exacerbate rhabdomyolysis - small dose of mannitol may benefit patients with rhabdomyolysis*

Preventing heat-related illness

Dress for the heat Wear lightweight, light-coloured clothing. Light colours will reflect away some of the suns energy. It is also a good idea to wear hats or to use an umbrella. Drink water Carry water or juice with you and drink continuously even if you do not feel thirsty. Avoid alcohol and caffeine, which dehydrate the body. Avoid foods that are high in protein, which increase metabolic heat. Stay indoors when possible. Take regular breaks when engaged in physical activity on warm days. Take time out to find a cool place.

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