Peri-intubation life threats

OVERVIEW

• VAPOURS is a mnemonic that can be used to ensure that life threats during the emergency peri-intubation period are addressed (a Levitanism, but with anglicised spelling!)
• In emergency situations, although A for airway comes at the start of the alphabet (ABC approach), definitive management does not necessarily need to be instituted immediately
• The ABC (or cABC) approach is useful as a cognitive aid to the systematic assessment of potential life-threats and what to treat, however, interventions should be ‘resequenced’ to allow pathophysiology to be optimised prior to definitive interventions (where possible) so that adverse effects will not leave the patient compromised.
• Useful mantras to consider:
  • Think of RSI as ‘resuscitation sequenced intubation’ (another Levitanism) rather than ‘rapid sequence intubation’
  • ‘Optimise (and customise) before you compromise’
  • ‘Oxygenate (and ventilate) before you intubate’

PHASES OF INTUBATION

Pre-induction

• preoxygenation fills up lungs
• sympathetic outflow due to pain and compensatory mechanisms (peripheral vasoconstriction)

Induction

• negative inotropy
• vasodilation
• decreased level of consciousness

Laryngoscopic/ intubation stimulus

• typically pressor effect due to sympathetic outflow
• may be blunted in coma
  • typically persists in traumatic brain injury (TBI), for instance, when there can be wild swings in blood pressure
• may be blunted by (pre)induction agents (e.g. fentanyl, lignociane)

Effect of apnea

• oxygen consumption
• hypercapnea
• Respiratory acidosis

Post-induction/ intubation phase

• persisting effect of induction agents
• positive pressure ventilation, in certain circumstances, can contribute to clinically significant:
  • Decrease in venous return
  • Increase in pulmonary artery pressure and afterload on the right ventricle
  • Dynamic hyperinflation

EXPLANATION OF “VAPOURS”

VAPOURS is a mnemonic categorising the types of (often inter-related) life threats that occur peri-intubation and the measures that can be taken during the:

• Pre-induction phase
• Post-induction phase (“apnea phase”)
• Post-intubation phase

Ventilation

• match patient’s minute ventilation if metabolic acidaemia (see below)
• correct severe hypoventilation prior to intubation to allow preoxygenation
• correct respiratory acidaemia and prevent excess cerebral vasodilation in at-risk patients
• ventilate gently to avoid respiratory alkalosis, gastric distention and baro/volutrauma

Acidaemia

• correct acidaemia and avoid respiratory acidosis (e.g. ventilate during “apnoie phase”)

Pressures

• A – alveolar
  • protective lung ventilation with open lung approach to prevent VALI and avoid hypoxaemia
• B – brain
  • in the setting of TBI or raised intracranial pressure, avoid excessive PEEP to prevent further increases in ICP and maintain adequate MAP to maintain CPP
• C – circulatory pressures (systemic and pulmonary)
  • avoid systemic hypotension (start inopressor agents prior to intubation in at-risk patients
  • avoid exacerbating pulmonary hypertension/ right heart failure in ‘at risk’ patients (e.g. avoid hypoxia, avoid acidaemia/ CO2 rise, avoid excessive PEEP and PPV)
• D – dynamic hyperinflation
  • avoid by providing an obstructive airways apporach to ventilation; disconnect from ventilator/ BVM if hypotension
• E – (o)esophageal/ gastric pressures
  • aim to ventilate with positive airway pressure (PAP) <15 cmH20 prior to intubation to prevent gastric distention
  • some patients may benefit from a nasogastric tube (NGT) to decompress the stomach prior to or immediately after intubation (e.g. small children, small bowel obstruction, etc), however, this must be weighed against the risk of delay, distraction, discomfort, and deleterious adverse effects.

Oxygenation

• optimise preoxygenation, apnoeic oxygenation and post-intubation oxygenation (i.e. peroxygenation, the term used by the Difficult Airway Society (DAS) to describe all three phases)
• Consider ventilation during the “apnoeic phase” (weighed against the risk of regurgitation and aspiration), especially in patients who cannot be adequately preoxygenation due to “shunt” physiology

Underlying disease

• seek and treat underlying disease and complications prior to intubation if it addresses an immediate life-threat or makes airway management safer

Regurgitation/ Fluids

• perform “rapid sequence intubation” if high risk of aspiration and no other life threats
• control upper airway bleeding, suction secretions, consider prokinetics and/or NGT to reduce risk of regurgitation

Shock Index

• shock index >1 predicts high risk of life-threatening hypotension
• Shock index = heart rate (/min)/ systolic blood pressure (mmHg)
• address by treating the underlying cause, appropriate fluid resuscitation and use of inotropes/ vasopressors

Resources and links

LITFL

• LITFL CCC — Intubation, hypotension, and shock

Journal articles

• Green RS, Fergusson DA, Turgeon AF, et al. Resuscitation Prior to Emergency Endotracheal Intubation: Results of a National Survey. West J Emerg Med. 2016;17(5):542-8. [article]
• Jaber S, Jung B, Corne P, et al. An intervention to decrease complications related to endotracheal intubation in the intensive care unit: a prospective, multiple-center study. Intensive Care Med. 2010;36(2):248-55. [pubmed]

FOAM and web resources

• ACEP Now — Timing Resuscitation Sequence Intubation for Critically Ill Patients by Richard Levitan (2015)
• St Mungos — Resuscitation Sequence Intubation