Head Trauma, Brain Death, and Transplant Donations

Introduction to Neurocritical Care for MCCQE1

For the MCCQE1, understanding the continuum of care from acute traumatic brain injury (TBI) to the determination of death and subsequent organ donation is vital. This topic integrates the CanMEDS roles of Medical Expert (acute management), Communicator (breaking bad news), and Health Advocate (facilitating organ donation).

This guide focuses on the Canadian approach to neurotrauma, the specific legal and medical criteria for Neurological Determination of Death (NDD), and the protocols regarding transplant donations managed by organizations such as Canadian Blood Services.

Head Trauma (Traumatic Brain Injury)

Traumatic Brain Injury (TBI) is a leading cause of death and disability in Canada, particularly among young adults (MVCs) and the elderly (falls).

Initial Assessment and Stabilization

The management of TBI follows the ATLS (Advanced Trauma Life Support) principles. The primary goal is to prevent secondary brain injury caused by hypotension and hypoxia.

Critical Concept: The Monro-Kellie Doctrine

The cranial vault is a fixed volume containing brain, blood, and CSF. An increase in one component must be compensated by a decrease in another, or Intracranial Pressure (ICP) will rise, leading to decreased Cerebral Perfusion Pressure (CPP) and herniation.

CPP = MAP - ICP

Glasgow Coma Scale (GCS)

The GCS is the standard for documenting level of consciousness. You must memorize this for the MCCQE1.

Score	Eye Opening (E)	Verbal Response (V)	Motor Response (M)
6	N/A	N/A	Obeys commands
5	N/A	Oriented	Localizes pain
4	Spontaneous	Confused	Withdraws from pain
3	To speech	Inappropriate words	Abnormal flexion (Decorticate)
2	To pain	Incomprehensible sounds	Abnormal extension (Decerebrate)
1	None	None	None

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MCCQE1 Tip: A GCS score of 8 or less generally defines a severe TBI and is an indication for intubation to protect the airway. “GCS 8, Intubate.”

Canadian CT Head Rule

This is a highly specific Canadian guideline used to determine the need for CT imaging in patients with minor head injury (GCS 13–15).

🇨🇦 Canadian CT Head Rule

CT is required if ANY of the following are present:

High Risk (for Neurosurgical Intervention):
GCS < 15 at 2 hours after injury
Suspected open or depressed skull fracture
Sign of basal skull fracture (e.g., hemotympanum, raccoon eyes, Battle’s sign, CSF leak)
Vomiting ≥ 2 episodes
Age ≥ 65 years
Medium Risk (for Brain Injury on CT):
Amnesia before impact > 30 minutes
Dangerous mechanism (e.g., pedestrian struck, ejection from vehicle, fall from >3 feet/5 stairs)

Types of Intracranial Hemorrhage

Epidural Hematoma

Source: Rupture of the Middle Meningeal Artery. Clinical Picture: Often associated with a temporal bone fracture. Classic “Lucid Interval” (knocked out $\rightarrow$ wakes up/fine $\rightarrow$ rapid deterioration). CT Appearance: Biconvex (lens-shaped) hyperdensity that does not cross suture lines.

Management of Elevated ICP

If signs of herniation are present (unilateral dilated pupil, posturing, Cushing’s Triad: Hypertension, Bradycardia, Irregular respirations), immediate action is required.

Task List for Acute ICP Management:

Elevate head of bed to 30 degrees.
Hyperventilate (Target $PCO_2$ 30–35 mmHg) only as a temporizing measure.
Osmotic therapy: Mannitol (0.25–1 g/kg) or Hypertonic Saline (3%).
Sedation and analgesia to decrease metabolic demand.
Neurosurgical consultation for decompressive craniectomy or EVD (External Ventricular Drain).

Neurological Determination of Death (NDD)

In Canada, “Brain Death” is legally and medically termed Neurological Determination of Death (NDD). It is defined as the irreversible loss of the capacity for consciousness combined with the irreversible loss of all brainstem functions, including the capacity to breathe.

Prerequisites for NDD Testing

Before testing, confounding factors must be ruled out.

Etiology: A known, proximate cause of brain injury compatible with NDD must be established (e.g., massive hemorrhage, severe anoxic injury).
Deep Unresponsive Coma: No motor response to pain in all extremities (spinal reflexes may persist).
Absence of Confounders:
- No severe hypothermia (Core temp must be $\ge$ 34°C; usually warmed to $\ge$ 36°C for testing).
- No hypotension (Systolic BP $\ge$ 90 mmHg or MAP $\ge$ 60 mmHg).
- No severe metabolic/electrolyte abnormalities.
- Crucial: Clearance of sedatives, analgesics, and neuromuscular blockers (check peripheral nerve stimulator).

The Clinical Examination

Step 1: Assessment of Brainstem Reflexes

The following must be absent bilaterally:

Pupillary response: Pupils fixed and dilated (or mid-position, but non-reactive).
Corneal reflex: No blink to touch.
Vestibulo-ocular reflex: No eye movement with caloric testing (Ice water caloric test).
Gag reflex: No response to posterior pharyngeal stimulation.
Cough reflex: No response to deep tracheal suctioning.
Motor response: No motor response to pain in cranial nerve distribution (e.g., supraorbital pressure).

Step 2: The Apnea Test

This is the definitive test to prove the absence of respiratory drive.

Pre-oxygenate with 100% $O_2$ for 10-20 minutes.
Draw baseline ABG ( $PCO_2$ should be normal range 35-45 mmHg).
Disconnect ventilator while delivering passive $O_2$ via tracheal cannula.
Observe for respiratory effort for 8–10 minutes.
Draw repeat ABG.
Positive Apnea Test (Confirms NDD): No respiratory effort AND $PaCO_2 \ge 60$ mmHg AND an increase of $\ge 20$ mmHg from baseline.

Step 3: Ancillary Testing (If needed)

If the clinical exam cannot be completed (e.g., severe facial trauma preventing eye exam) or apnea test is unsafe, ancillary tests are used.

Standard in Canada: Radionuclide cerebral blood flow study (demonstrates no blood flow to the brain).
CT Angiography or 4-vessel Angiography.

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Canadian Guideline: In Canada, NDD is a clinical diagnosis. Usually, two physicians are required to certify death, though specific provincial laws may vary. They must not be associated with the transplant team.

Organ Donation and Transplantation

Organ donation is a critical component of end-of-life care. In Canada, donation is typically managed by provincial organizations (e.g., Trillium Gift of Life in Ontario) under the umbrella of Canadian Blood Services.

Types of Donation

NDD (Neurological Determination of Death):
- Heart beating, ventilated donor.
- Allows for donation of heart, lungs, liver, kidneys, pancreas, bowel, tissues.
- Better graft survival rates generally.
DCD (Donation after Circulatory Death):
- Patient does not meet NDD criteria but has a non-recoverable injury.
- Life-sustaining therapy (ventilator) is withdrawn with family consent.
- Death is declared after circulatory arrest (usually 5 minutes of pulselessness).
- Organs typically donated: Kidneys, Liver, Lungs (Heart is possible but complex).

Donor Management (The “Rule of 100s”)

Once NDD is declared, the focus shifts from cerebral protection to somatic support to preserve organs for transplant.

Systolic BP: > 100 mmHg (Use fluids, Vasopressin is preferred pressor).
Urine Output: > 100 mL/hr (Treat Diabetes Insipidus with Desmopressin).
PO2: > 100 mmHg.
Hemoglobin: > 100 g/L (approx, or Hct > 30%).

Contraindications to Donation

Absolute contraindications are few but include:

Active metastatic cancer (some primary CNS tumors are exempt).
Uncontrolled sepsis (bacterial/fungal) - relative.
Prion diseases (CJD).
HIV/Hepatitis are not absolute contraindications (can donate to positive recipients or with specific protocols).

Key Points to Remember for MCCQE1

GCS Calculation: Be fast and accurate.
Cushing’s Triad: Hypertension, Bradycardia, Irregular Respiration = Impending Herniation.
Canadian CT Head Rule: Know the high-risk vs. medium-risk criteria.
Epidural vs. Subdural: Know the vessel (Middle meningeal vs. Bridging veins) and CT shape (Lens vs. Crescent).
NDD Criteria: Coma + Absence of Brainstem Reflexes + Apnea.
Apnea Test Threshold: $PaCO_2 \ge 60$ mmHg and $\ge 20$ mmHg rise.
Confounders: Never declare NDD if the patient is hypothermic or on sedatives.

Sample Question

Case Presentation

A 24-year-old male is brought to the emergency department following a high-speed motorcycle collision. He was intubated at the scene. On arrival, his blood pressure is 110/70 mmHg, heart rate is 95 bpm, and temperature is 36.5°C. A CT scan of the head reveals diffuse cerebral edema and subarachnoid hemorrhage.

24 hours later, despite maximal medical therapy, the patient’s condition deteriorates. The nurse notes that his pupils are fixed and dilated (6mm) bilaterally. He has no motor response to deep pain. The intensivist performs a clinical exam: corneal, gag, and cough reflexes are absent. Cold caloric testing shows no eye movement.

The team proceeds to the apnea test. Baseline ABG shows $PaCO_2$ of 40 mmHg. The patient is disconnected from the ventilator with oxygen supplied via tracheal cannula. After 8 minutes, no respiratory effort is observed. The repeat ABG shows a $PaCO_2$ of 62 mmHg.

Which of the following is the most appropriate next step in the management of this patient?

A. Perform a radionuclide cerebral blood flow study to confirm the diagnosis.
B. Declare death based on neurological criteria and approach the family regarding organ donation.
C. Continue observation for another 24 hours and repeat the clinical examination.
D. Administer IV mannitol and hyperventilate to lower intracranial pressure.
E. Consult neurosurgery for immediate decompressive craniectomy.

Explanation

The correct answer is:

B. Declare death based on neurological criteria and approach the family regarding organ donation.

Detailed Analysis

Diagnosis of NDD: This patient meets all the clinical criteria for Neurological Determination of Death (NDD) in Canada.
- Prerequisites: Known cause (TBI), normothermic (36.5°C), normotensive.
- Clinical Exam: Deep coma (no motor response), absent brainstem reflexes (pupils, corneal, gag, cough, vestibulo-ocular).
- Apnea Test: The test was positive. There was no respiratory effort, the $PaCO_2$ was $\ge 60$ mmHg (62 mmHg), and the rise was $\ge 20$ mmHg (40 to 62 mmHg).
Option A: Ancillary testing (radionuclide flow study) is only indicated if the clinical exam or apnea test cannot be safely or fully performed. Since the clinical criteria and apnea test were successfully completed and confirmatory, ancillary testing is unnecessary and delays the process.
Option C: Once NDD criteria are met, the patient is dead. There is no requirement in adult Canadian guidelines to wait an arbitrary amount of time to repeat the exam if the first exam is definitive and prerequisites are met.
Option D & E: These are interventions for a living patient with elevated ICP. Once NDD is declared, the patient is deceased; treatment shifts to donor management if consent is obtained, or withdrawal of support.

References

Shemie, S. D., et al. (2006). Severe brain injury to neurological determination of death: Canadian forum recommendations. Canadian Medical Association Journal (CMAJ).
Stiell, I. G., et al. (2001). The Canadian CT Head Rule for patients with minor head injury. The Lancet.
Teasdale, G., & Jennett, B. (1974). Assessment of coma and impaired consciousness. A practical scale. The Lancet.
Canadian Blood Services. (2023). Clinical Guide to Organ Donation.
Medical Council of Canada. (2023). MCCQE Part I Clinical Decision-Making and Multiple-Choice Question Guidelines.