Head and Brain trauma

Section: Trauma Curriculum: Curriculum, page 77

Classification

TBI Severity

	Mild	Moderate	Severe
LOC	Brief (sec - min)	< 24hrs	> 24hrs
PTA (Amnesia)	< 1hr	1 - 24hrs	> 24hrs
Imaging	Normal	Abnormal	Abnormal
GCS	13-15	9-12	3-8

• Severe Traumatic Brain Injury
  • LOC and post traumatic amnesia > 24hrs with abnormal imaging and GCS 8 or less (tubed)
• Pathological Classification
  • Focal
  • Diffuse → DAI
  • Blunt vs penetrating

Pathophysiology Raised ICP

• Measuring Physiological Parameters in TBI
  • MAP - SBP + 2xDBP/3
  • ICP
    • Normal: 7-15mmHg

    • 20mmHg - Mass lesion (haematoma/oedema) → Decompress

    • Affected by - CSF Volume, brain water, CBV, Cerebral VR
    • Broadly affected inflow, outflow, cerebral oedema, CSF fluid volume
  • Cerebral perfusion pressure (CPP)
    • Net pressure gradient driving cerebral blood supply
    • MAP-ICP = CPP - normal is 60-70mmHg (supine)
  • Cerebral blood flow (CBF)
    • Normal - 50-55ml/min/100g brain tissue (15% CO)
    • Tightly autoregulated
    • BP, PaO2, PaCO2
  • Pathophysiology of TBI
    • Direct tissue damage and impaired CBF regulation
    • Lactic acid build up via anaerobic respiration
    • Cerebral oedema via increase membrane permeability
• Cerebral Perfusion Pressure (CPP) = MAP - ICP
  • Increased ICP causes reduced CPP
  • Leads to cerebral ischaemia and brain injury
• CPP of 60-70mmHg recommended after severe traumatic brain trauma
• Cerebral autoregulation controls CPP normally but after trauma it can function abnormally
  • When autoregulation mechanism is intact
    • Raised ICP causes lower CPP
    • Vasodilation occurs to increase CBF and CPP (increased compliance)

Management of TBI

• In TBI, the normal tight autoregulation of CBF is compromised
• Principles of Management
  • Maintenance of BP and oxygenation
    • Administer oxygen and usual resuscitation with target MAP 90-100
  • Reducing secondary hits
    • Treat and prevent
      • Anaemia
      • Hypo/hyperglycaemia
      • Hyponatremia
      • Fever
  • Adjuncts
    • ICP monitoring
    • ICP treatment
      • Mannitol - causes hypovolaemia
      • Hypertonic saline
      • Barbiturates if refractory
      • Hyperventilation

Surgery - Burr hole and Craniectomy

• Indications for rural neurosurgical intervention
  • Neurologically deteriorating pt and can’t do CT head
  • T/F to nearest N/S unit is > 2 hours away
  • Sizable intracranial haematoma
• Indications for Burr hole
  • GCS 8 or less with imaging showing epidural haematoma causing midline shift and unequal pupils
  • High clinical suspicion with palpable #, ipsilateral fixed dilated pupil and deteriorating neurology without imaging
• Burr Hole technique
  • Confirm side and position → Shave and prep
  • LA and 3cm incision to bone
  • Periosteal elevation and self-retainer
  • Hudson brace manual burr used perpendicular to skull with saline being applied for bone dust
  • Stop when resistance gives
  • Perforator for conical opening widened by cylinder burr
  • Epidural clot should evacuate now
  • If it doesn’t = Subdural → Open dura with knife
  • If no blood - confirm side/scan and if bleeding on-going DO NOT TAMPONADE
  • Transfer patient
• Locations:
  • Temporal - 1cm above Posterior Zygomatic Arch
  • Frontal - 10cm above pupil - over the Coronal Suture approx 10cm cephalad and in line with the Mid-Pupillary line
  • Parietal - 5cm above ear - over the Parietal Eminence
• Emergency Frontotemporal Craniectomy
  • Scalp incision from ant to ear curving up and anteriorly to follow temporal plane
  • Raise flap
  • Serial burr holes include edge of # and combine with Gigli saw
  • Elevate bone flap
  • Don’t dig out bone fragments from bone parenchyma - causes more injury
• Death occurs due to on-going bleeding → High ICP → Brain shift and herniation causing brain stem damage