Gold Standards Hypothermic CA

Question 1

Define accidental hypothermia

Answer 1

Below 35 degrees

Question 2

Primary vs Secondary CA

Answer 2

Primary - cardiac arrest due to severe hypothermia. Better outcome - esp if no asphyxia.
Secondary - hypothermic after arrest due to other cause

Question 3

4 methods of environmental heat loss?

Answer 3

Radiation, conduction, convection and evaporation

Question 4

Survival in 15 and 5 degrees water?

Answer 4

1. 4.5 hours

2. Less than 2 hours

Question 5

Temperature classifications for hypothermia

Answer 5

Mild: 35-32 (shivering, conscious)
Moderate: 32-28 (Reduced consciousness, not shivering)
Severe: 28-24 (LOC, present vital signs)
Cardiac arrest/low flow state: <24 (No or minimal vital signs)
Irreversible: <13.7

Question 6

Cardiovascular effects of cold (haemodynamic)

Answer 6

Initial: sympathetic response, increased catecholamines -> ^CO

Question 7

Cardiovascular effects of cold (electrical)

Answer 7

Moderate hypothermia: e.g. 28-32:

SA node spontaneously depolarises less frequently as neural conduction is decreased ->prolonged conduction intervals -> bradycardia -> Decreased CO

Question 8

At 20 degrees what is CO at?

Answer 8

20% of normal

Question 9

Why do cold conditions lead to arrhythmias?

Answer 9

Purkinje fibres and myocardium are sensitised and increasingly irritable, especially below 30 degrees.

(AF->VF->Asystole)

Question 10

What ECG changes might see?

Answer 10

Osbourne/ J waves - positive reflection at the J point - proportional to hypothermic extent.
Seen below 32 degrees, not pathognomonic.

Question 11

Where else see J/Osbourne waves?

Answer 11

Hypercalcaemia, raised ICP, SAH, iodpathic VF - Le syndrome d’haissaguerre

Question 12

Respiratory system response?

Answer 12

Increased drive initially.
Reduced metabolism -> slowing of RR.

Also: increased secretions, decreased ciliary motility, impaired cough reflex - aspiration likely. Also when recovering - infection/ARDS

Question 13

Resp in relation to degree of hypothermia?

Answer 13

Mild: increased RR, alkalosis
Moderate: Low RR, acidosis, cough loss/ciliary dysfn/bronchorrhea
Severe: reduced VO2, pulmonary oedema

Question 14

On O2 delivery graph, what way does hypothermia shift the graph?

Answer 14

Left (reduced oxygen delivery)

Question 15

Longest ‘no flow’ with no adverse neuro outcome?

Answer 15

6.5 hours

Question 16

Temperature -> cerebral requirement drop?

Answer 16

Below 35, 6%/degree.
So - 28: 50%
22: 75% etc

Question 17

Hypothermia categories and expect to see neuro-wise?

Answer 17

Mild: ataxia, apathy, amnesia
Moderate: pupillary dilatation, paradoxical undressing, LOC.
Severe: no corneal reflex, no pain response

Question 18

Cold diuresis?

Answer 18

Impaired Na/K pump causes K retenion ->hyperkalaemia -> acidaemia (decreased rest drive/lactic acidosis)
Central functional hypervolaemia: due to peripheral vasoconstriction

Question 19

Why would chronic alcohol use contribute to hypothermia?

Answer 19

Impaired shiver response, thermogenesis and hypothalmic degeneration

Question 20

Alcohol and hypothermia - interactions?

Answer 20

Peripheral vasodilation: worsens hypothermia.
Decreased metabolic rate: decreased clearance
LOC/failure to seek shelter

Question 21

Signs of futility in hypothermia?

Answer 21

Ice in pharynx, inability to compress the chest or if cause of arrest is: lethal injury, fatal illness or prolonged asphyxia.
Remote area - practicality of rewarming.

Question 22

What can precipitate VF when in hypothermic cardiac arrest?

Answer 22

Rough handling, intubation, etc

Question 23

Intubation in hypothermic c/a?

Answer 23

Early! Beware reduced compliance of soft tissues.

Question 24

Why is hyperventilation a risk in CPR?

Answer 24

Cerebral hypoxia due to reduced cerebral blood flow.

Question 25

What used to measure temperature?

Answer 25

Tympanic thermometers - accurate to 20 degrees.

Question 26

Why are rectal temperatures not accurate?

Answer 26

Faecal loading. | Also - rectal temperature lags by several degrees which can escalate care with hyperthermia.

Question 27

How is defibrillation adapted in hypothermia?

Answer 27

VF/VT: try three times, but not again until temp reaches 30 degrees (myocardial damage risk) No pacing for bradycardia until normothermic (may be physiological)

Question 28

How are drug doses/administration of adapted in hypothermia?

Answer 28

Less effective due to reduced BMR. Toxic levels can arise with same dose. Reasonable to withhold until 30 degrees. Same doses in ALS, but doubled intervals until reach 35 degrees. NB - Adrenaline increases CPP, but not survival

Question 29

Prehospital re-warming procedure - mild?

Answer 29

Passive rewarming. Insulate with blankets/foil/cap and move to warm environment.

Question 30

Prehospital re-warming procedure - moderate-severe?

Answer 30

Active rewarming - apply chemical heat packs to trunk. If unconscious, and airway unsecure, arrange the insulation around the patient in a recovery position. Reheating with warm IV and warm humidified air will not be feasible. Intensive active rewarming must not delay transport to hospital where advanced rewarming techniques and monitoring are available.

Question 31

Signs of cardiac instability in Stage II-IV? Action?

Answer 31

SBP <90, centricular arrhythmias, core temp <28 etc Action: Transfer to ECLS centre

Question 32

Difficult extrication rules?

Answer 32

Intermittent CPR if not possible for continuous. Below 28 degrees: 5 mins with, 5 mins without. Below 20 degrees: 5 mins with, 10 mins without.

Question 33

Not dead until you're?

Answer 33

Warm and dead

Question 34

ECMO location?

Answer 34

Femoro-femoral: easier, reduces heat loss compared to aortic-right atrial.

Question 35

Internal re-warming if no ECMO?

Answer 35

Bair Hugger Warm IV fluids Warm inspired O2 Lavage - use warmed hartmanns solution; gastric, bladder, peritoneal or pleural. Warmed peritoneal dialysate (4L) via Peritoneal Catheter. Leave for 15 mins to exchange heat before draining. Pleural requires apical and basal chest drain on each side. “L of warmed hartmanss is infused into each hemithorax via apical drain and removed after 15 mins. High volume renal hemofilter

Question 36

Define slow rewarming

Answer 36

Increases temp by 0.3-1.2 degrees/hour. (17-30 kcal/hour)

Question 37

What temperature are IV solutions heated to?

Answer 37

45 degrees (17 kcal/hour)

Question 38

What temperature are inspired o2?

Answer 38

0.7 degrees/hour (30 kcal/hr)

Question 39

How quickly do warmed blankets rewarm?

Answer 39

0.9 degrees/hour

Question 40

Define moderate rewarming

Answer 40

3 degrees/hour Gastric lavage, 65 degree IV solutions and 45 degree peritoneal lavage

Question 41

Define rapid rewarming

Answer 41

Levels higher than 100 kcal/hour Thoracic lavage, cariodpulmonary bypass, ECMO and AV dialysis

Question 42

How quick is endogenous rewarming?

Answer 42

300 kcal/hour

Question 43

Problem with warm water baths?

Answer 43

Core temperature after drop and CV collapse - peripheral vasodilation

Question 44

How quickly should we rewarm?

Answer 44

Aggressively: rapid rewarming

Question 45

What do you do if you get ROSC?

Answer 45

Re-warm to mild hypothermia - avoid overshooting. | When CV stable - re-warm aggressively

Question 46

How can you avoid rewarming shock?

Answer 46

Volume load to maximise CO

Question 47

Criteria of futility if no ROSC at >32 degrees

Answer 47

- Potassium over 10mmol/l - Severe trauma - Prior cardiopulmonary, renal or neuro disorders

Question 48

Gold standard for rewarming?

Answer 48

ECMO/bypass

Question 49

Is defibrillation more or less effective in hypothermia?

Answer 49

Less

Question 50

What is the gold standard for temp reading?

Answer 50

oesophageal - closest to core