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c_asystole

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choking / respiratory arrest / cardiac arrest / BLS / ALS / CPR

  • The main considerations in adult cardiac arrest are:
    • should the patient have aggressive CPR management - is there an advanced care directive, is resuscitation futile?
    • if aggressive CPR management:
      • cerebral perfusion pressure predicts neurologic outcome
        • maintaining a systolic BP > 60mmHg and head up position are important
        • the primary goal of cardiac compressions is to maintain cerebral perfusion during the compression phase
      • coronary perfusion pressure and degree of coronary artery stenosis predicts return of spontaneous circulation (ROSC) post-arrest
        • coronary perfusion pressure = Aortic Diastolic Pressure – Left Ventricular end-diastolic Pressure (LVEDP)
        • the secondary goal of cardiac compressions is to maintain coronary perfusion during the relaxation phase of CPR as it creates diastole-like conditions
        • perfusion of the heart is necessary for successful defibrillation (if the arrest type is shockable) and ROSC
        • a coronary perfusion pressure of at least 15 mmHg is thought to be necessary for ROSC
        • see cardiac physiology
        • delays to and interruptions of, plus duration of optimal cardiac compressions will significantly adversely impact coronary perfusion pressure
          • consider femoral artery US to monitor “pulse checks” looking for > 20cm/sec flow peaks as manual pulse checks interrupt compressions longer and have poor sensitivity
          • consider early art line to monitor BP
          • if refractory or recurrent VT / VF see electric storm for Mx options

introduction

  • mortality from in-hospital VF arrest:
    • “30%” if VF occurs and immediate defibrillation is perfomed
    • >95% if defibrillation delayed by > 12 minutes
  • mortality from Out-of-Hospital cardiac arrest (OHCA):
    • VF arrest - 66-96%
      • depending on bystander CPR, availability of early defibrillator use
      • likelihood of survival largely determined by return of spontaneous output by the time patient arrives in ED.
    • asystole - >99%
  • thus prevention is far better than the cure!
    • in-hospital Medical Emergency Team (MET) to attend and manage critically ill ward patients ASAP
    • timely assessment and Mx of patients presenting to ED with early senior doctor input to detect at risk patients.
    • community awareness of chest pain and need for ambulance transfers ASAP

Mx of choking victim

  • call for help
  • if effective cough:
    • implied mild airway obstruction thus encourage coughing and get help, remain with victim
  • ineffectual coughing:
    • implies severe airway obstruction
    • conscious:
      • call for help
      • give up to 5 back blows
      • if not effective, give up to 5 chest thrusts
      • if no relief but remains conscious, repeat above
    • unconscious:
      • call for help
      • commence CPR as below

Mx of primary respiratory arrest due to anaphylaxis or asthma

  • hypoxic brain injury is likely to commence within 4 minutes of PaO2 < 29mmHg or SaO2 < 40% and this will generally then progress to bradycardia then asystole
  • mouth to mouth ventilation, bag valve mask or LMA airway are very UNLIKELY to be of benefit as airway pressures are too high and it will only result in inflating stomach
  • IMMEDIATE intubation with rapid progression to surgical airway if 1st intubation attempt fails should be done if patient is in extremis, very agitated with hypoxia or unconscious
  • seizures are likely to be due to hypoxia - Rx the hypoxia not the seizures!
  • aggressive EARLY Rx with repeated epinephrine - 5 minutely IM or IV infusion if readily available if persistent wheeze, SOB or hypoxia in a patient with presumed anaphylaxis
  • aggressive EARLY Rx with inhaled salbutamol (and/or inhaled epinephrine if upper airway obstruction causing stridor such as in croup or anaphylaxis)
  • NIV may have a role whilst patient is awake
  • IV fluid bolus if also hypotense from anaphylaxis
  • immediate intubation by the most expert operator available WITHOUT waiting for sedatives to be used BUT with a muscle relaxant to help intubation if in extremis or unconscious
  • have an operator READY to perform surgical airway if intubation fails within 2 minutes or so of profound hypoxia - every SECOND COUNTS to avoid brain death!
  • ventilate at a low respiratory rate to allow sufficient time for air to be exhaled, consider squeezing chest to assist
  • consider pneumothoraces, especially if CPR has been used.

summary of Basic Life Support (BLS) for cardiac arrest

The Zombie CPR instructional video


7 components of BLS:

  • D: remove from danger
  • R: assess patient responsiveness
  • S: send for help
  • A: clear airway
    • head tilt-chin lift if non-trauma, or jaw thrust if trauma
    • remove vomitus using suction if possible
    • recognition and relief of foreign body airway obstruction
  • B: restore breathing although no longer the priority in adult out-of-hospital arrest
    • cardiac compressions alone (no ventilations) recommended for adult, out-of-hospital primary cardiac arrest (not respiratory) if witnessed, and with shockable rhythm or short period (<4 minutes) of untreated arrest
    • cardiac compressions alone also recommended if bystander not trained in CPR, or not confident in their ability
    • breaths (in hospital or those trained in CPR):
      • bag and mask if available (and oxygen at 15L/min to deliver 85% oxygen if available)
      • 2 effective breaths every 30 compressions with a 1 second inspiratory time (except neonates, give 40-60 breaths/min)
        • if unprotected airway, pause compressions during breaths
        • if protected airway (eg. ETT in situ), don't pause compressions, and rate should 1 breath every 15 compressions (2 breaths in children every 15 compressions)
      • bag size:
        • > 18kg or > 5yrs old, use a 1600ml adult bag
        • infant, use a 500ml bag
        • neonate, use a 240ml bag or neonatal circuit
  • C: establish circulation:
    • checking for pulses is unreliable, instead start compressions if no signs of life, for instance:
      • unresponsive or unconscious
      • not breathing or the occasional gasping breath
      • not moving
    • cardiac compressions over mid-sternum to a depth of 1/3rd chest (eg. 4-5cm in an adult) at a rate of 100 per minute for all ages, stopping to allow 2 breaths every 30 compressions if unprotected airway
    • early cardiac compressions may:
      • prevent VF deteriorating into asystole
      • increase the chance of successful defibrillation in VF
      • add to the preservation of brain and cardiac function
  • D: availability of semi-automatic external defibrillators:
    • defibrillation as soon as possible provides the best chance of survival in victims with VF or pulseless VT
    • see Mx of pulseless VT or VF
    • C/I to SAED (await ALS team instead):
      • children < 8yrs age or < 25kg
      • unsafe environment
      • conscious and breathing normally
  • if cardiac arrest occurs in the obviously pregnant woman, place in a left lateral tilt by placing a pillow or wedge under the right buttock - this will reduce compression of IVC and aid venous return.

summary of Advanced Life Support (ALS) for cardiac arrest

  • consider and correct:
    • hypoxia (eg. see above under Mx of respiratory arrest)
    • hypovolaemia
    • hyperkalaemia, hypokalaemia and other metabolic disorders
    • tension pneumothorax
    • tamponade
    • toxins
    • thrombosis (PE/AMI)

further airway management if still unconscious

  • intubation should not interrupt chest compressions for more than 20 seconds
  • avoid hyperventilation as risk of complications from increased intrathoracic pressure, and decreased coronary and cerebral perfusion.
  • ventilation rate once intubated should usually be 8-10 breaths/minute, without pausing for chest compressions (rate 15:1)
  • confirmation of correct endotracheal tubbe placement - eg. end-tital CO2

references and other resources

and for fun

Mr Bean - CPR at the bus stop

1)
Clin. Toxicol. (Phila.) 2010; 48(1):1-27
c_asystole.txt · Last modified: 2023/10/18 06:18 by gary1
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