Hypothermia Flashcards
Define and classify hypothermia:
Core temp below 35
Down to 32 = mild
Down to 28 = mod
Below 28 = severe
Causes of secondary hypothermia:
Don’t forget to consider/ check for these after stabilised
Psychiatric (behavioural)
Sepsis
Multi trauma/ burns/ desquamation (exposed flesh)
Malnutrition/ cachexia (low fat)
CNS: CVA, TBI, infection, mass, Wernicke, (thalamic dysfunction)
Spinal cord injury
Endocrine (hypothyroid/adrenal, hypoglycaemia)
Drugs (sedatives)
Iatrogenic (fluid resus, exposure, GA)
Discuss methods of temp monitoring in hypothermia:
Must be CORE measurement
Oesophageal probe in lower third of oesophagus- prob best. Accurate, minimal lag, can stay there during cavity lavages.
Bladder probe. Will need to move if bladder lavage done. Minor lag.
Rectal probe. 15cm in. Problematic lag during rewarming due to cold faeces.
X Probe directly against tympanic membrane very accurate, but impractical.
X Pulmonary artery is gold standard generally, but dangerous in hypothermia re irritable myocardium.
ECG in hypothermia:
Shivering artefact
Prolonged PR, QRS and QT
Bradycardia and Bradyarrythmia
- Slow AF most common
- Slow junctional
- AV block 1-3deg
Osborn/ J waves
- In mod/ severe
- Wave magnitude directly proportional to degree of hypothermia
- Most specific ECG finding but not pathognomic
- Not prognostic
Ventricular ectopics
VF, VT or Asystole
Non-hypothermia causes of an Osborn/J wave:
Hypercalcaemia
AMI
Takotsubo
LVH
Neurological
Brugada
Normal variant/ BER
Clinical/OE signs at various stages of hypothermia:
MILD
Shivering, ataxia, dysarthria
Tachycardia, tachypnoea, hypertension
Apathy/ disorientation
Cold diuresis
MODERATE
Bradycardia, decreased CO
Hypoventilation, loss of airway reflexes
Paradoxical undressing, hallucinations, ALOC, reduced shivering
Sluggish pupils, hyporeflexia
SEVERE
Stiff and cold with no signs of life
Ventricular arrythmia, asystole
Paradoxical vasodilation
Apnoea
Unconscious, fixed dilated pupils
No shivering, no reflexes, rigid
+ SWISS STAGING
Biochemical findings at various stages of hypothermia:
MILD
HypoK
Met and resp alkalosis
Mildly deranged coags
MODERATE
Haemoconcentration due to
3rd spacing
Deranged coags- bleedy OR clotty
HYPERK
HYPERglycaemia
Met and resp acidosis
Liver failure, pancreatitis
SEVERE
Bleedy, DIC, thrombocytopaenia
Rhabdo, renal failure
HYPERglycaemia
Swiss staging for hypothermia
For when core temp not available (ie. wilderness):
1- Conscious , shivering (mild)
2- ALOC, no shivering (mod)
3- Unconscious (severe)
4- Apnoeic
5- Death (considered irreversible)
Rewarming methods:
PASSIVE - mild, primary
0.5 - 2deg/hr, requires shivering
Dry clothes
Cover head
Warm room
Blanket
Calories
ACTIVE EXTERNAL- mild to mod, stable
Radiant heaters
Warming blankets (air/electric/water) 0.5 - 3
Warm water immersion 2 - 4
ACTIVE INTERNAL- mod to sev, unstable or arrested
NONINVASIVE:
Warmed IV fluids + O2 @40deg
PREVENT COOLING/ MAINTAIN not truly ‘active’
INVASIVE:
Cavity Lavage:
- Stomach, bladder, colon-insignificant
- Peritoneum 1-4
- Thoracic (closed) 1-6
- Thoracic (open) 8
Endovascular:
- Femoral catheter 1-3
Extracorporeal:
- Haemodialysis 3
- VA ECMO 4.5
- Bypass 9.5
Complication phenomena of rewarming:
CORE AFTERDROP
Decline in body temp with rewarming, due to cold blood from extremities circulating again
Probably not significant.
REWARMING SHOCK
Return of acid and metabolic products (lactate, K etc.).
—> hypotension, decreased output, arrest.
When to call off efforts in hypothermia:
30mins above 32 deg and still ‘warm and dead’
Early if:
Arrest was BEFORE hypothermia- eg. SUBmersion
Temp <6
K >12
Chest or airways frozen solid
Large cardiac thrombus
APPROACH TO HYPOTHERMIA
Handle carefully (VF)
Core temp (oesophageal, rectal or bladder)
Establish severity:
- Swiss
- Core temp
Rewarm
Bloods:
- Gas, FBC, UEC, LFT, CMP, coags incl fibrinogen, CK, lipase
Pulse check for full minute (+- US, Doppler)
If arrest:
- No drugs until 30
- Double interval until 34
- 3x initial stacked shocks then not until 30
- Go until 30mins above 32
Replace fluids (cold diuresis)
Don’t correct electrolytes/ acidosis/ coags (unless hypoglyc, or active bleed)
Early NGT
Early fluid balance
Seek and treat secondary causes:
- CTB
- Septic screen (empirical antis neonate, elderly, immunosuppressed)
- Thyroid function, cortisol, pituitary
- Tox screen
Differentiate cold-induced tissue injuries:
Frostnip
- Pale, painful or numb extremities
- Resolves within 30mins
Chilblains
- Repeated cold exposure
- Red, swollen, itchy and burning sensation
- Sometimes purple bullae
Immersion Foot
- AKA trench foot
- Wet
- Red, swollen, painful ++
Frostbite
- Soft tissue damage 2 to below-freezing temp
-1st to 4th degrees
Frostbite classification and features:
Treatment of Frostbite:
Admit to specialist unit
Avoid thaw/refreeze (bad prognosis)
Rapid rewarming by immersion in 40-42deg water until red and pliable-usually 30mins
—> Use thermometer, must stay in narrow range for effect/ avoid injury
Regular NSAIDS to prevent thrombosis
Elevate
Debride clear blisters, leave haemorrhagic ones intact
ADT, BenPen
Await true depth to declare (weeks) then OT PRN
