Resuscitation: Special circumstances part 1 of 2 (8 - 10 min read)

Drowning and Hypothermia

With the return of face to face exams coming up imminently, I wonder what resuscitation scenario’s the college will get you all to act out. I’ve created a 2 part series focusing on special circumstances in resuscitation so you don’t find yourselves caught out!

In this blog post we’ll cover the following:

1. Basic definitions

2. Key points

3. Causes of drowning

4. Pathophysiology of drowning

5. Management of drowning and hypothermia: Pre hospital —> hospital

6. Hypothermia

7. Hypothermia ALS guidance

8. Methods of rewarming

9. Management of drowning and hypothermia: In hospital goals

10. Summary

Let’s get cracking!

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1. Definitions:

• Drowning: Drowning is the process of experiencing respiratory impairment from submersion/immersion in liquid (WHO 2002 definition)

• Immersion: airway is ABOVE the surface of the liquid (e.g. having a bath, surfing)

• Submersion: airway is BELOW the surface of the liquid

• Hypothermia classification: (varies slightly from textbooks)

  • Mild 32 – 35 degrees centigrade

  • Mod 28 – 32 degrees centigrade

  • Severe <28 degrees centigrade

2. Key points:

·      Submersion duration is the strongest predictor of outcome 

·      Prognosis determined by severity and duration of cerebral hypoxia/anoxia and the amount of water than that has been aspirated 

·      Hypothermia and drowning is associated with a protective mechanism that potentially increases survival rate

o   How? – rate of CMRO2 reduced by approx. 5-7% for each reduction of 1°C in temperature within the range of 37°C to 20°C

·      These patients often require prolonged resuscitation attempts as per the hypothermia resuscitation guidance (see below)

3. Causes of drowning:

• Misadventure

• Inadequate supervision of small children

• Neurological event e.g. epilepsy, stroke

• Cardiac event e.g., MI, HCM, dysrhythmia, long QT, short QT

• Impaired judgement e.g. intoxication

• Trauma

• Overdose

• Foul play

4. Pathophysiology of drowning

Water enters the mouth —>

1.     First: voluntarily spat out or swallowed

2.     Second: Conscious response to hold breath, until no longer able to

3.     Then: 

a.     Water aspirated into airways —>coughing (reflex response)

b.     Continued aspiration à progressive hypoxaemia —> loss of consciousness and apnoea 

                                               i.     Laryngospasm may also occur 

c.     Hypoxaemia —> tachycardia —> bradycardia —> PEA —> Asystole 

Process usually occurs in seconds to minutes 
>1 hour in unusual cases of hypothermia

5. Management of drowning and hypothermia: Pre hospital —> hospital

NB: Only trained individuals should attempt in-water rescue. Otherwise…

Simultaneously assess and manage…

1. Lift patient out horizontal + attempt to rewarm/minimise heat loss + arrange fast transfer asap…

   1. Remove wet clothing

   2. Wrap in thick blankets

2. Assess consciousness 

   1. Conscious and/or breathing normally —> ABCDE assessment + aim to prevent cardiac arrest

      1. 100% oxygen until Spo2 can be measured reliably or ABG obtained 

      2. Targets: 94 – 95%, Pao2 10 – 13kpa 

      3.  Hypothermic + RF for imminent cardiac arrest —> ideally transfer to ECMO centre

   2. Unconscious and not breathing normally —> start resuscitation (ALS algorithm) 

      1. Initiate hypothermia algorithm if core temp <35

      2. 5 rescue breaths/ventilations with 100% o2 if available

      3. Remains unconscious? Start CPR 30:2 (adult ALS algorithm)

         1. Defibrillate if indicated and available

         2. Early intubation advised

         3. Consider ECPR

6. Hypothermia 

Key interventions:

1.     Pre-hospital insulation/rewarming

2.     Triage

3.     Fast transfer

RF for imminent cardiac arrest:

1.    Core temperature < 30°C

2.    Ventricular arrhythmia

3.     SBP < 90 mmHg

7. Hypothermia ALS guidance: Key points:

1.     REWARM – unlikely to respond to drugs before warmed 

2.   <30  - No drugs 

3.   30 – 35  - DOUBLE interval between drugs

4.     Defibrillation is less effective 

o    <30  Shockable rhythm? —> 3 stacked shocks, then delay further attempts until >30°C

Prehospital:

·      Individuals at risk of cardiac arrest/in cardiac arrest should ideally be directly transferred to an extracorporeal life support (ECLS) centre for rewarming.

8. Methods of rewarming:

• Passive rewarming:

  • Remove wet clothes

  • Insulate with blankets

• Active rewarming:

  • Peripheral (forced air warmer (bair hugger), hot water bottles)

  • Central (warmed humidified inspired gases, warmed IVF, lavage, intravascular thermal regulation via vascath, haemofiltration, cardiopulmonary bypass)

    • Non eCLS (extra-corporeal life support) rewarming should be initiated in peripheral hospital if an ECLS centre cannot be reached within 6 hours

• Hypothermic cardiac arrest - rewarming should be performed with ECLS, preferably with ECMO over CPB.

9. Management of drowning and hypothermia: In hospital goals

• Continue ABCDE management à likely will require ICU care

• Rewarm to 34 for 24 hrs

·      Management of organ injury – the following list is not exhaustive but is designed to highlight the key points of care…

• AIRWAY: intubate early if indicated

• RESP: lung protective ventilation. Risk of ALI and ARDS

• CARDIOVASCULAR: < 28 VF is common, SIRS, hypovolaemia from endothelial disruption/cold diuresis

• CNS: prevent secondary brain injury - neuroprotective strategies, manage seizures

• GI: NG to decompress stomach

• RENAL: Risk of rhabdomyolysis, AKI.

• METABOLIC: severe metabolic acidosis from raised lactate. Caution PaO2 in cold patient is much lower than the measured value

• INFECTION: consider antibiotics if patient submerged in grossly contaminated water

10. Summary

Hopefully by the end of reading this, you’re now able to recognise the links between drowning and hypothermia and appreciate the differences between hypothermic cardiac arrests and your standard ALS cardiac arrest algorithm. Comments welcomed below!

Stay tuned next week for more on resuscitation special circumstances…

Good luck with your study in the meantime!