Hypothermia Flashcards
Define hypothermia
Body temperature <35oC
mild: 32-35°C
moderate: 28-32°C
severe: < 28°C
Aetiology of hypothermia
Either increased (1) heat loss (2) decreased thermogenesis (3) impaired thermogenesis
age (elderly and infants at risk)
environmental – exposure, drowning, alpine environment, poverty (lack of heating or shelter)
drugs/ tox – alcohol, sedatives, vasodilators
Sepsis
CNS disorders e.g. hypothalamic lesions, hypopituitarism
Endocrine/ metabolic – hypothyroidism, adrenal insufficiency, hypothermia, malnutrition
Trauma — burns, spinal cord injury
Shock
Skin disorders — psoriasis, exfoliating conditions
Iatrogenic — cold fluid administration, intra-operative, therapeutic hypothermia
Psychiatric (may lead to exposure)
Signs and symptoms of hypothermia
CVS: bradycardia is normal; decreased Q and MAP, vasoconstriction
RESP: decreased CO2 production, decreased PAO2 and PaCO2 due to increased gas solubility, increased dead space, diaphragmatic fatigue, metabolic acidosis -> pulmonary hypertension
GI: decreased hepatic metabolism and blood flow, decreased splanchnic circulation
METABOLIC: decreased BMR, shivering, left shifted oxy-Hb dissociation curve, hyperglycaemia, decreased drug metabolism
CNS: neuroprotection, fixed dilated pupils at < 30 C (mimics brain death)
HAEM: increased bleeding time, PT and APTT, VTE risk, decreased platelet and WCC
RENAL: decreased GFR and RBF, cold-induced diuresis
Investigations for hypothermia
1st: axillary/oral temperature – if less than 36.5 C →
2nd: low-temperature PR probe / infra-red ear thermometer
ECG: broad complex bradycardia | prolonged PR/QT | J waves | shivering artefacts
FBC
U&Es
TFTs
Glucose
Amylase
ABG
Management for hypothermia
- Resuscitation
- pulse check – palpate for up to 1 minute (consider Echo / Doppler as hard to find – do not delay CPR)
- move patient gently if <32 degrees due to risk of triggering VF
- no adrenaline or other drugs until >30C
- between 30-35C double the dose intervals of ACLS drugs
- shock VF up to 3 times if necessary, then no further shocks until T>30C
- ‘not dead until warm and dead’ (30-32C)
Warming: passive, peripheral active, central active
Supportive:
- use esophageal probe preferentially (core temperature, minimal lag time)
- use low reading thermometer
- ABG measurements at 37C (temperature uncorrected values) to allow serial monitoring
- Antibiotics to cover for pneumonia
- Catheter
- Cardiac monitoring
Describe passive warming
For Patients who are able to shiver (1.5° C/hr)
Keep dry
Warm environment
Insulation with blankets e.g. aluminium foil
Hat
Allow to mobilise if conscious
Describe peripheral active warming
Chemical heat pads
Radiation methods
Forced air warming blankets (1-2C/h)
Describe central active warming
warmed (40-46C) humidified inspired gases (1 C/h; 1.5°C/h ET tube)
warm IV fluids (42C) (only give if need fluids, prevents cooling rather than promotes warming) – use Level 1 fluid warmer
body cavity lavage with 40C fluid e.g. peritoneal (3C/h), gastric, bladder, right-sided thoracic lavage (3-6C/h – use 2 ICCs for continuous flow)
RRT
ECMO/ bypass (9-18C/h)
Complications of hypothermia
Cardiac arrhythmias
Hypoglycaemia
Hyperkalaemia
Rhabdomyolysis
GI disorders
Bleeding diathesis
Bladder atony
Local injuries
Afterdrop, a drop in core body temperature during rewarming may occur a consequence of peripheral vasodilation and release of cold peripheral blood to the body core. It is not usually significant.
Prognosis for hypothermia
Generally, patients with mild hypothermia will recover without any residual effects
If the core temperature was between 26°C and 32°C (78.8°F to 89.6°F) and the patient received acute resuscitation, recovery is likely but with lasting morbidity
Most patients with a core temperature <26°C (<78.8°F) do not survive
The triad of coagulopathy, acidosis, and hypothermia is also associated with increased mortality.
