Brain Impact Apnoea
OVERVIEW
- brain impact apneoa is an under-appreciated cause of morbidity and mortality in traumatic brain injury (TBI)
- hypoxia can markedly worsens outcome in TBI
- aka ‘impact brain apnoea’
- rapid correction (e.g. by bystanders) of brain impact apnoea may facilitate full neurological recovery
PATHOPHYSIOLOGY
The first 10 minutes following TBI has been described as ‘the critical phase’ (it is followed by exponential, plateau and resolution phases) and is thought to involve 2 key components:
- apnoea
- catecholamine surge
Apnoea
- Always occurs with concussive head injury
- greater the energy delivered to the brain, the longer the subsequent apnea and the poorer the respiratory recovery
- In severe forms respiratory recovery does not occur spontaneously, leading to death without resuscitation at the scene
- Prolonged apnoea causes:
- hypoxia over a period of minutes leading to direct neuronal injury and cell death
- hypercapnia resulting in cerebral vasodilation and increased cerebral blood volume
- the end result can be massive, early cerebral oedema resulting in death or poor neurological outcomes
- in addition to centrally driven apnoea, obstructive apnoea resultant from loss of airway patency may also occur
Catecholamine surge
- massive sympathetic discharge occurs resulting in hypertension
- hypertension compounds hypercapnia-induced cerebral vasodilatation resulting in early vasogenic edema, endothelial injury, and blood-brain barrier disruption
- intracranial pressure (ICP) progressively increases depending on the magnitude of the adrenergic surge and hypercapnia
- other vascular beds may develop sustained vasoconstriction, resulting on complications such as ischemic gastric mucosal ulceration and neurogenic pulmonary oedema
- direct catecholamine tissue injury can occur, such as myocardial necrosis
ASSESSMENT
Clinical features
- history of traumatic brain injury
- apnoeic since time of impact
- respiratory failure may progress to lethal cardiac arrest unless there is appropriate intervention
Imaging
- CT Head (may be normal, underlying severe anatomical injury may or may not be present)
MANAGEMENT
- requires prompt prehospital intervention (e.g. by bystanders, may be facilitated by innovations such as the GoodSam app)
- open airway (with cervical spine protection if appropriate)
- correct hypoxia and hypoventilation
- if cardiac arrest has not supervened some patients will spontaneously rouse or be extubated neurologically intact after further investigation (sometimes with a normal CT head)
- start usual severe TBI management if required (see TBI Management)
References and Links
CCC Neurocritical Care Series
Emergencies: Brain Herniation, Eclampsia, Elevated ICP, Status Epilepticus, Status Epilepticus in Paeds
DDx: Acute Non-Traumatic Weakness, Bulbar Dysfunction, Coma, Coma-like Syndromes, Delayed Awakening, Hearing Loss in ICU, ICU acquired Weakness, Post-Op Confusion, Pseudocoma, Pupillary Abnormalities
Neurology: Anti-NMDA Encephalitis, Basilar Artery Occlusion, Central Diabetes Insipidus, Cerebral Oedema, Cerebral Venous Sinus Thrombosis, Cervical (Carotid / Vertebral) Artery Dissections, Delirium, GBS vs CIP, GBS vs MG vs MND, Guillain-Barre Syndrome, Horner’s Syndrome, Hypoxic Brain Injury, Intracerebral Haemorrhage (ICH), Myasthenia Gravis, Non-convulsive Status Epilepticus, Post-Hypoxic Myoclonus, PRES, Stroke Thrombolysis, Transverse Myelitis, Watershed Infarcts, Wernicke’s Encephalopathy
Neurosurgery: Cerebral Salt Wasting, Decompressive Craniectomy, Decompressive Craniectomy for Malignant MCA Syndrome, Intracerebral Haemorrhage (ICH)
— SCI: Anatomy and Syndromes, Acute Traumatic Spinal Cord Injury, C-Spine Assessment, C-Spine Fractures, Spinal Cord Infarction, Syndomes,
— SAH: Acute management, Coiling vs Clipping, Complications, Grading Systems, Literature Summaries, ICU Management, Monitoring, Overview, Prognostication, Vasospasm
— TBI: Assessment, Base of skull fracture, Brain Impact Apnoea, Cerebral Perfusion Pressure (CPP), DI in TBI, Elevated ICP, Limitations of CT, Lund Concept, Management, Moderate Head Injury, Monitoring, Overview, Paediatric TBI, Polyuria incl. CSW, Prognosis, Seizures, Temperature
ID in NeuroCrit. Care: Aseptic Meningitis, Bacterial Meningitis, Botulism, Cryptococcosis, Encephalitis, HSV Encephalitis, Meningococcaemia, Spinal Epidural Abscess
Equipment/Investigations: BIS Monitoring, Codman ICP Monitor, Continuous EEG, CSF Analysis, CT Head, CT Head Interpretation, EEG, Extradural ICP Monitors, External Ventricular Drain (EVD), Evoked Potentials, Jugular Bulb Oxygen Saturation, MRI Head, MRI and the Critically Ill, Train of Four (TOF), Transcranial Doppler
Pharmacology: Desmopressin, Hypertonic Saline, Levetiracetam (Keppra), Mannitol, Midazolam, Sedation in ICU, Thiopentone
MISC: Brainstem Rules of 4, Cognitive Impairment in Critically Ill, Eye Movements in Coma, Examination of the Unconscious Patient, Glasgow Coma Scale (GCS), Hiccoughs, Myopathy vs Neuropathy, Neurology Literature Summaries, NSx Literature Summaries, Occulocephalic and occulovestibular reflexes, Prognosis after Cardiac Arrest, SIADH vs Cerebral Salt Wasting, Sleep in ICU
Journal articles
- Atkinson JL. The neglected prehospital phase of head injury: apnea and catecholamine surge. Mayo Clin Proc. 2000 Jan;75(1):37-47. Review. PubMed PMID: 10630756. [Free Full Text]
- Wilson MH, Hinds J, Grier G, Burns B, Carley S, Davies G. Impact Brain Apnoea–a forgotten cause of cardiovascular collapse in trauma. Resuscitation. 2016. [article]
FOAM and web resources
- St.Emlyn’s — Impact Brain Apnoea with Gareth Davies from London HEMS (2015; podcast)
- Spanos A. Impact brain apnoea: a critical phase of head injury. 2021
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.
After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.
His one great achievement is being the father of three amazing children.
On Twitter, he is @precordialthump.
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