HYPOTHERMIA

 

Etiology:

  • Environmental
     
  • Metabolic  (Addisons  crisis, DKA, hypoglycemia , hypoTSH)
     
  • CNS  (Wernicke, CVA)
     
  • Drugs  (ETOH, Narcotics, Benzo)
     
  • Sepsis
     
  • Dermal disease

S & S:

  • These depend on the temperature degree:
     
    • 35° C = mild hypothermia .  Pt  retains  capacity   to  generate   heat. VS are generally  wnl  or elevated (hyperdynamic state).
       
    • 32° C  = moderate hypothermia. Decrease  metabolism and utilization  of  O2 and L shift of oxyhemoglobin  curve. BP and H.R.  are  decreased
       
    • 30 ° -32° C = severe hypothermia. Shivering   capacity  is  lost.  Pt is at risk of arrhythmias.
       
  • Following organs can be affected:
     
    • CV - ¯ BP, ¯HR, TW  inversion, PR, QRS , QT prolongation, J ( Osborn ) wave. Once  temp  is  < 30° C, we  notice sinus  brady, A . fib  with  slow  ventricular  response, V. fib,  EMD, asystole. V. tach is not common.
       
    • Pulmonary ­ Increase RR. OxyHgb  curve shift  to  L - thus  decrease O2  delivery  and   need  for  supplemental  O2. ABG  requires  correction  for  given  temp  to be  accurate ,  but practical  approach  is  to  use  the  non  corrected  values.
       
    • GI  - decrease peristalsis  and  consequent  bowel  distention   and  ileus. Pancreatitis has been reported. Decrease in  hepatic  function occurs. This  affects  conjugation  and  ability  to  detoxify  meds Þ ­ in therapeutic drug levels ( e.g. Lidocaine  accumulates to toxic levels).
       
    • Renal - Cold  diuresis  2ry  to  impaired  renal  ability  to  concentrate  urine. Rhabdomyalisis is another complication that can occur during hypothermia.
    • CNS  - confusion ÞlethargyÞ coma with areflexia. Pupils may be dilated and not responsive to light.
       

DX:

  1. No specific blood test to diagnose hypothermia but but lab abnormalities must be corrected. Thus we advise the following blood test: Tox screen (ASA, APAP, ETOH), CPK (r/o MI, r/o rhabdomyalisis), LFT, PT/PTT,  Amylase, SMA, CBC.
     
  2. CT and C-spine as suggested by exam and history.
  3. EKG at low temperatures will show Osborn waves (J wave)

Treatment:

  1. Rewarming  techniques are multiple and used according  to clinical severity:
     
    1. Passive  rewarming
       
      • removal  from  cold
         
    2. Active  external  rewarming
       
      • heating  blankets can cause dangerous paradoxical  drop in body temperature induced via return of cold  blood from the peripheral vasodilatation and worsening acidosis.
         
    3. Active  core  rewarming
             :
      • humidified  warm  O2 (42° - 46°C)
      • warm  IVF at  43°C
      • GI  lavage  with  warm  NS
      • bladder  irrigation   with  warm  fluids  via  Foley
      • peritoneal  lavage
      • chest  tube lavage
      • Bypass  machine
         
  2. In  case  of  hypothermic cardiac  arrest    the  protocol is :
    1. Start  CPR  in  all  monitored  pts
       
    2. If  pt   is  unmonitored ,  he  should  be  examined   for  1 full  minute before  pronouncing him/her pulse less  and  starting  CPR  since  the "cold"  heart  is  susceptible  to  V.fib when     stimulated. This  principle  also  applies  to  invasive  procedures  such  as  central  line    placement.
       
    3. Sinus  bradycardia and  A. fib usually  revert  with  rewarming  without medical therapy     needed . Furthermore, the  "cold"  heart  is  resistant  to  Atropine.
       
    4. V.Fib  is also  unresponsive  to  drug  therapy   if  pt  has not been rewarmed  first. If  Lidocaineis  given it can accumulate to toxic level since the "detoxifying" effect of liver is malfunctioning.
       
    5. Only  1 - 2  defibrillation's should  be  attempted  if  temp  is  < 30°C as the hypothermic heart is unresponsive to electrical stimuli
       
    6. Bretylium  is considered drug of choice in  hypothermic V. fib
        
    7. Finally , no one is pronounced dead  unless  warm  and  dead,  warm being  90 ° F  or  32° C of body temperature.

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