Environmental Flashcards
What is the pathophysiology of hypothermia?
- hypothermia occurs when the bodys temperature falls below 35 degrees
- exposure to decrease in temp
- peripheral (skin, mucous membranes) and central thermo receptors provide feedback to trigger involuntary and voluntary mechanisms (autonomic and neurohormonal) to control temperature
What is the pathophysiology of hyperthermia?
- Skin receptors (and blood) sense an increase in temperature that signals the hypothalamic thermostat.
Involuntary responses: - Hypothalamus inhibits adrenergic activity of the sympathetic nervous system. This results in vasodilatation (increase heat loss through the skin) and a decrease in basal metabolic rate.
- Cholinergic sympathetic fibres stimulate sweat production.
Voluntary responses: - Decreasing activity, Lying with limbs spread, Wearing loose/less clothing, Cool drinks, Fanning
What are the different stages of hypothermia?
- Mild 32-35 degrees
- Moderate 28-32 degrees
- Severe < 28 degrees
What are the implications of hypothermia associated with cardiac arrest?
- defibrillation and cardio active drygs may not be effective at temps below 30 degrees.
- VF may resolve spontaneously upon rewarming
- the onset and duration of drugs is prolonged in hypothermia and the interval between doses is therefore doubles when the temp is < 30 degrees
- doses of adrenaline become 8 minutely
What are the signs and symptoms of hyperthermia?
Essentially Heat exhaustion is a pre-cursor to heat stroke.
This presents initially with the following:
* Profound sweating
* Signs of dehydration
* Headache
* Nausea
* Dizzyness
* Thirst
* Irritability
As the patient progresses to heat stroke you will see:
* Sweating stops
* Alteration to conscious state
* Rapid increase in temp
* Altered perfusion
What is the prehospital management for hyperthermia?
- During cooling, the patient should be monitored for the onset of shivering. Shivering may increase heat production and cooling measures should be adjusted to avoid its onset
- Gentle handling of the patient is essential. Position flat or lateral and avoid head up position (to avoid causing arrhythmias)
Cooling techniques:
* Shelter / remove from heat source
* Ensure airflow over Pt
* Remove all clothing except underwear
* Apply tepid water using spray bottle or wet towels.
* Ice packs
* Provide cold oral hydration if tolerated
* Consider ice-bath/cold shower for fit healthy patients with environmental/exertional heat illness.
- Provide initial Normal Saline 20ml/kg IV and reassess VSS and temp.
- Continue to administer Normal Saline if pt remains poorly perfused or significantly dehydrated.
- Consider early transport (need for intubation)
- Consider psychostimulant overdose guideline and intervention with Midazolam.
- Aim for temp <40 degrees within 30min of symptom onset.
What is mild hypothermia and what are the associated symptoms?
temp 32-35
- these are all physiological responses to preserve/generate heat
- SNS excitation occurs
Sx
- shivering
- hypertension
- tachycardia
- tachypnoea
- pallor
- cold diuresis, mental confusion as well as hepatic dysfunction
What is moderate hypothermia and what are the associated symptoms?
28-32 degrees
- low body temp results in shivering becoming more violent
- lack of muscle coordination becomes apparent
- movements are slow and laboured, accompanied by a stumbling pace and mild confusion, although the victim may appear alert
- surface blood vessels contract further as the body focuses its remaining resources on keeping the vital organs warm
- skin becomes pale. Lips, ears, fingers and toes may become blue
- this carries a 21% mortality rate at this temp
What is severe hypothermia and what are the associated symptoms?
- difficulty in speaking, sluggish thinking, amnesia may start to apepar
- inability to use hadns adn stumbling
- cellular metabolic processes shut down, shivering stops
- Below 30 degrees the exposed skin becomes blue and puffy, muscle coordiantion becomes poor, incoherent/irrational behaviour including terminal burrowing
- HR and resp rates decrease significantly, but VT and VF can occur
Why can arrythmias occur in hypothermia?
- hypothermia causes decreased depolarisation of cardiac pace maker cells resulting in bradycardia
- asystole and VF have been observed to occur spontaneously at core body temps < 28 degrees
What are some general symptoms of hypothermia?
- Cool, pale skin
- Shivering
- Loss of concentration, poor judgment
- Loss of fine motor coordination
- Drowsiness
- Lethargy
- Confusion, irritability
- Dizziness
- Difficulty breathing
- Loss of physical coordination, unsteady on feet
- Stops shivering eventually
- Slurred speech, speech difficulty
- Slowed breathing
- Dilated pupils
What are some age related changed with thermoregulation
- paeds (young) experience greater heat loss than adutls as they cannot adequately shiver to maintain body heat
- the elderly - have reduced resistance to extremes of temperatures. e.g. shiver response may be greatly diminished or even absent.
What are some ECG changes that can be expected in hypothermia?
- J wave
What are key points when treating hypothermic patients?
- Primary goal of severe hypothermia- to prevent further heat loss to ROSC or transport.
- Prehospital management is unlikely to result in significant improvement in temperature.
- Consider alteration to Cardiac Arrest management
- Important to ensure major trauma patients have temp >35 degrees
- Utilise basic warming measures (hood, heater, thermal blankets)
- Remove wet clothing
What is hyperthermia?
- Hyperthermia is an elevated body temperature due to failed thermoregulation (>38.5°C)
- Hyperthermia occurs when the body produces or absorbs more heat than it can dissipate.
- When the elevated body temperatures are sufficiently high, hyperthermia is a medical emergency and requires immediate treatment to prevent disability or death
