Hypothermia Flashcards
What is the definition of hypothermia?
unintentional reduction of core body temperature below the normal physiological limits
What is the initial physiological response to hypothermia?
- thermoreceptors in the skin and subcutaneous tissues sense the low temperature and cause a regional vasoconstriction
- therefore hypothalamus stimulates the release of TSH and ACTH
- stimulates heat production by promoting shivering
What are 2 hormones released by the hypothalamus in response to hypothermia?
TSGH
ACTH
What is the definition of mild hypothermia?
32-35 oC
What is the definition of moderate hypothermia?
28-32oC
Which demographic is particularly susceptible to hypothermia?
elderly, most commonly during winter
What are 4 causes of hypothermia?
- Exposure to cold in the environment
- Inadequate insulation in the operating room (surgery)
- Cardiopulmonary bypass
- Newborn babies
What are 6 risk factors for hypothermia?
- General anaesthesia
- Substance abuse
- Hypothyroidism
- Impaired mental status
- Homelessness
- Extremes of age
What are 6 signs of hypothermia?
- Shivering
- Cold and pale skin
- Slurred speech
- Tachypnoea, tachycardia and hypertension (if mild)
- Respiratory depression, bradycardia and hypotension (if moderate)
- Confusion/ impaired mental state
What will vital signs be like in mild vs moderate hypothermia?
- mild: tachypnoea, tachycadia, hypertension
- moderate: respiratory depression, bradycardia, hypotension
How might a baby with hypothermia present?
may look healthy, but by limp, unusually quiet and refuse to feed
What is done in newborns to prevent hypothermia?
hat and clothing/blankets are applied soon after birth
What are 7 investigations that may be performed in hypothermia?
- Temperature
- 12 lead ECG
- FBC, U+Es
- Blood glucose
- ABG
- Coagulation factors
- CXR
What are 2 ways that core temperature can be measured to assess hypothermia?
- Low-reading rectal thermometer
- Thermistor probe
When should a patient’s temperature be measured in suspected hypothermia and why?
should be tracked over time, to check for improvement
What are 3 signs on an ECG that may occur as core temperature approaches 32oC?
- Acute ST-elevation
- J waves
- Osborn waves
What changes may occur to the FBC in hypothermia?
- haemoglobin and haematocrit can be elevated due to haemoconcentration
- platelets and WBCs are low due to sequestration in the spleen
Why should U+Es be measured in hypothermia?
monitoring potassium advised, as hypokalaemia can occur in hypothermia due to a shift into the intracellular space
Why should blood glucose be measured in hypothermia?
stress hormones are increased (hypothalamic release of ACTH) and body an have more peripheral resistance to insulin
What are 4 aspects of the initial management of hypothermia?
- Removing the patient from the cold environment + remove any wet/cold clothing
- Warm body with blankets
- Secure airway and monitor breathing
- If patient not responding well to passive warming, consider maintaining circulation using warm IV fluids or applying forced warm air (using Bair-Hugger) directly to the patient’s body
What is the risk of rapid re-warming in hypothermia?
can lead to peripheral vasodilation and shock - should be prepared to conduct CPR
What type of drug administration should be avoided if possible in hypothermia and why?
IV drugs, as patient is more likely to have a drastic response to the drug
What are 4 things that the NHS adivses the public not to do when a person has hypotherima, and why?
- Don’t put person in a hot bath
- Don’t massage their limbs
- Don’t use heating lamps
- Don’t give them alcohol to drink
- due to risk of cardiac arrest
What is the definition of severe hypothermia?
<28oC
What are 4 signs of severe (<28 degrees) hypothermia?
- Markedly reduced consciousness/coma
- Apnoea
- Arrhythmia
- Fixed and dilated pupils
What are 6 ECG changes which may be seen in hypothermia?
- Bradyarrhythmias e.g. sinus bradycardia, AF with slow ventricular response, slow junctional rhythms and varying degrees of AV block
- Osborne waves (=J waves)
- Prolonged PR, QRS and QT intervals
- Shivering artefact
- Ventricular ectopics
- Cardiac arrest (VT, VF or asystole)
What are 4 types of bradyarrhythmias which may be seen in hypothermia?
- Sinus bradycardia
- Atrial fibrillation with slow ventricular response
- Slow junctional rhythms
- Varying degrees of AV block
What are Obsorne (or J) waves?
positive deflection at the J point between the end of the QRS and beginning of the ST segment
