GC175 A Bus Hit A Train Multiple Trauma; Disaster Management
A mass casualty incident involving a bus-train collision requiring activation of disaster management protocols to triage, prioritize, and treat multiple trauma victims with coordinated prehospital and hospital resource allocation.
Disaster Management & Multiple Trauma
This lecture (GC 175) is delivered by Dr Dai Wing Chiu, Director of Trauma Service & Consultant Surgeon at Queen Mary Hospital. It covers two intertwined domains: disaster management (pre-hospital, system-level response to mass casualty incidents) and multiple trauma (clinical approach to the severely injured individual). The lecture uses real-world case studies — a Hong Kong bus-train collision (2013), Boston Marathon Bombing (2013), and the Beirut Explosion (2020) — to illustrate principles.
Why this matters for exams: Disaster management and triage appear as MCQs testing the correct first action, the difference between field and hospital triage, and the ABCDE approach. Past papers have directly tested on-site triage methods, incident command, crush syndrome in disasters, and the widened mediastinum in trauma. The lecture also bridges to GC 207 (TEAM), GC 208 (Head Injury), GC 188 (Abdominal Injury), and GC 231 (High Energy Trauma), so understanding this framework is foundational.
Learning Objectives (from the lecture) [1]:
- What is a disaster
- The classification of disasters
- Principles of mass casualty management
- Principles of resuscitation of mass casualties
"A sudden event, such as an accident or a natural catastrophe, that causes great damage or loss of life. An event or fact that has unfortunate consequences." [1]
Key Distinction: Disaster vs MCI
A disaster is the event itself. A Mass Casualty Incident (MCI) is defined by the functional mismatch between needs and resources: "Event(s) causing a number of casualties large enough to disrupt the health care services of the affected community." The defining formula is Needs >>> Resources. [1]
This means the same event (e.g., a bus crash with 20 casualties) might be an MCI in a rural area but not in a major urban centre with multiple trauma centres. Context determines whether it's an MCI.
The Disaster Environment [1]
The disaster environment is:
- Complicated
- Stressful
- Situational uncertainty
- Time compression
- High demand of qualified cares
Understanding this is important because it explains why we need pre-planned protocols, incident command systems, and simplified triage algorithms — you cannot rely on ad-hoc decision-making under these conditions.
| Category | Examples | Lecture-Specific Data [1] |
|---|---|---|
| Natural disasters | Typhoons, earthquakes, floods, landslides, forest/hill fire | 1976 Tangshan: 240,000–700,000 deaths; 2004 Tsunami: 230,000; 2008 Sichuan: 69,000; 2010 Haiti: 316,000 |
| Man-made disasters | War, Transportation, Industrial accidents, Terrorism, Technological disasters | Hong Kong 2013 bus-train: 62 injured; Boston Marathon 2013; Beirut 2020 |
| Disease outbreaks | Epidemics/pandemics (WHO list) | Referenced via WHO emergency diseases page |
Classification of Disasters: Natural disasters — Typhoons, earthquakes, floods, landslides, forest/hill fire. Man-made disasters — War, Transportation, Industrial accidents, Terrorism, Technological disasters. Disease. [1]
Why classify? Because the type of disaster predicts the pattern of injuries (e.g., blast injuries in terrorism, crush injuries in earthquakes, burns in industrial accidents), the contamination risk (chemical/radiological in industrial/terrorism), and the scale/duration of the response needed.
This is a crucial conceptual shift that examiners love to test:
| Parameter | Civilian Urban | Civilian Rural | Disaster |
|---|---|---|---|
| Threat level | None | None | High |
| Resources | Readily available | May be limited | Severely limited |
| Personnel | Excess | Limited but expandable | Fixed and limited |
| Supplies/Equipment | Fully equipped, resupply readily available | Adequately equipped, delay to resupply | Limited supplies, resupply significantly delayed |
| Available expertise | Full subspecialty services | Limited specialties locally available | No subspecialty services immediately available |
| Transfer availability | Immediately available | Available but longer transport times | Highly variable, maybe no option for transfer |
The paradigm change: from the application of unlimited resources for the greatest good of each individual patient, to the allocation of limited resources for the greatest good of the greatest number of casualties. [1]
Exam Trap
Students often default to "treat the sickest patient first" (AED triage thinking). In a disaster/MCI setting, this is WRONG. The principle shifts to utilitarian triage — do the greatest good for the greatest number. A patient requiring 3 hours of OR time who might still die should be triaged below someone who can be saved with 30 minutes of intervention.
4. ABCs of MCI Response — Four Phases
ABCs of MCI Response — Four Phases: 1. Search and rescue; 2. Triage and initial stabilisation; 3. Definitive medical care; 4. Evacuation. [1]
- Getting to the victims and extricating them from the scene
- Safety of rescuers is the first priority (scene safety — fire, structural collapse, chemical hazard, secondary devices in terrorism)
Phase 2: Triage and Initial Stabilisation
| Peak | Timing | Causes | Intervention |
|---|---|---|---|
| Immediate deaths | Seconds to minutes | Massive brain injury, high spinal cord injury, cardiac/great vessel rupture | Generally not salvageable even with perfect care |
| Early deaths | Minutes to hours | Airway obstruction, tension pneumothorax, haemorrhage (splenic/liver laceration, pelvic fracture), epidural haematoma | "Golden hour" — this is where triage, BLS, ATLS saves lives |
| Late deaths | Days to weeks | Sepsis, multi-organ failure, secondary brain injury | ICU care, damage control surgery, infection prevention |
The trimodal death distribution shows immediate deaths (seconds-minutes), early deaths (minutes-hours), and late deaths (days-weeks). [1]
The entire rationale for triage and the ATLS system is to reduce the early death peak. That's where the biggest gains are.
- A — Airway
- B — Breathing
- C — Circulation
Safety is the first concern. To provide maximum outcome benefit for the majority. To identify, provide initial treatment, and transfer victims with life and limb threatening conditions to the appropriate hospital. [1]
| Triage Type | Principle | Priority | Context |
|---|---|---|---|
| Field Triage (Disaster/MCI) | Do the greatest good for the greatest number | Mildly injured may be treated first if it frees resources; unsalvageable patients deprioritised | Resource-limited |
| AED (Hospital) Triage | Most seriously injured has highest priority | Sickest patient first | Resources available |
| Military Triage | Mildly injured treated first so soldiers can return to battlefield ASAP | Return to duty | Maintain fighting force |
| Civilian Triage | Severely injured and high chance of survival treated first | Worst-but-salvageable first | Standard hospital practice |
High Yield — Field Triage vs AED Triage
This distinction is directly tested in MCQs. In the field (MCI), you sort — not treat. The goal is to move the walking wounded out of the way, identify the acute cases, and defer the unsalvageable. In the AED, you have resources, so the sickest salvageable patient comes first.
Victims designated as "acute" or "non-acute." Acute = Red. Non-acute = Green. [1]
This is the simplest, fastest sorting. Anyone who can walk to a designated area is "Green" (non-acute). Everyone else is "Red" (acute) and needs further assessment.
The ability to walk is the fastest discriminator at the scene. This is directly tested — see past paper Q3 (2022 MCQ) below.
Rapid categorisation of victims at casualty site by experienced medical personnel with a knowledge of various injuries (e.g., blast, crush, biological, radiological, chemical, burns). [1]
Uses the Cruciform Triage Tag — a physical tag attached to the patient with tear-off coloured strips:
- Red (Immediate/T1): Life-threatening injuries, salvageable with immediate treatment
- Yellow (Delayed/T2): Serious injuries but can wait hours
- Green (Minor/T3): Walking wounded, minor injuries
- Black/White (Expectant/Dead): Dead or unsalvageable
Easy visible for disaster victims. Big sign post. Convenient exit routes for air and land evacuation. [1]
This is where victims are gathered after initial triage, before evacuation. Practical point: if the collection site is hard to find or has poor access routes, the entire evacuation chain breaks down.
This is where ATLS principles apply — see Section 5 below.
Modes of evacuation:
- Ground transport
- Helicopters
- Small fixed-wing aircraft
- Large fixed-wing aircraft
Indications for Evacuation [1]:
- Decompress disaster area (reduce the burden on overwhelmed local facilities)
- Improve care for critical casualties
- Provide specialised care to specific casualties (burns, crush injuries)
Concepts of ATLS — Advanced Trauma Life Support: Treat the greatest threat to life first. Definitive diagnosis should not impede the application of an indicated treatment. A detailed history is not essential to begin the evaluation. "ABCDE" approach. [1]
High Yield
"Treat the greatest threat to life first" and "a detailed history is not essential to begin evaluation" — these are core ATLS axioms. In an exam, if a question asks what to do first for a crashing trauma patient, the answer is NEVER "take a full history" — it's always to start with Airway.
Primary Survey — ABCDE [1]
Primary Survey: Patients are assessed and treatment priorities established based on their injuries, vital signs, and injury mechanisms.
| Step | Component | Key Actions |
|---|---|---|
| A | Airway and C-spine protection | Jaw thrust (not head-tilt in trauma), suction, oropharyngeal/nasopharyngeal airway, intubation if needed. Always assume C-spine injury until cleared. Manual in-line stabilisation (MILS) during intubation. |
| B | Breathing and ventilation | Look, listen, feel. Identify and treat immediately life-threatening thoracic injuries: tension pneumothorax, open pneumothorax, massive haemothorax, flail chest with pulmonary contusion. Needle decompression → chest drain. |
| C | Circulation with haemorrhage control | Two large-bore IV cannulae (14G/16G), take bloods (CBC, T&S, coagulation, lactate), start crystalloid resuscitation. Direct pressure for external bleeding. Identify sources of occult haemorrhage: chest, abdomen, pelvis, long bones, "on the floor" (external). FAST scan. Pelvic binder if open-book fracture suspected. |
| D | Disability / Neurologic status | AVPU or GCS, pupil size and reactivity, lateralising signs. Glucose check (hypoglycaemia mimics head injury). |
| E | Exposure / Environmental control | Fully undress the patient (log roll to examine back), but prevent hypothermia with warm blankets and warm IV fluids. The trauma triad of death = hypothermia + acidosis + coagulopathy. |
Sequence matters: You do NOT move to B until A is secured. You do NOT move to C until B is addressed. This is because airway obstruction kills faster than breathing failure, which kills faster than haemorrhage.
After primary survey: Adjuncts include Foley catheter (unless urethral injury suspected), NG tube (orogastric if base of skull fracture suspected), ECG monitoring, and trauma imaging (CXR, pelvic XR, FAST) [2].
6. Primary Trauma Diversion
This is the HK-specific system for deciding which hospital a trauma patient should go to from the scene. The lecture lists both anatomical and physiological criteria [1]:
| Criterion | Why It Matters |
|---|---|
| Flail chest | Indicates severe thoracic trauma with likely underlying pulmonary contusion; ventilatory failure |
| Lower limb fracture involving two long bones | Massive blood loss potential (each femur fracture ~1–1.5L) |
| Amputation proximal to wrist or ankle | Major vascular injury, haemorrhage |
| All penetrating injuries to head, neck or torso | Risk of injury to vital structures (great vessels, heart, CNS, abdominal viscera) |
| Limb paralysis | Spinal cord injury |
| Pelvic fracture | Massive haemorrhage potential (retroperitoneal, up to several litres) |
| Combined trauma and burns ( > 2nd degree or > 20%) | Complex management, need burn unit |
| Criterion | Threshold | Significance |
|---|---|---|
| GCS | < 14 | Any reduction in consciousness suggests significant head injury |
| Systolic BP | < 90 mmHg | Haemorrhagic shock (Class III/IV) |
| Respiratory rate | < 10 or > 29/min | Impending respiratory failure or severe distress |
| Cardiac arrest or airway difficulties | Present | Immediately life-threatening |
Primary Trauma Diversion criteria determine whether a patient should be transported directly to a trauma centre rather than the nearest hospital. [1]
Exam Intelligence
These criteria are essentially the same as "Field Triage Decision Scheme" thresholds used in many jurisdictions. If a patient meets ANY one of these criteria, they should bypass local hospitals and go directly to a designated trauma centre.
7. Hong Kong-Specific Disaster Plans
CLK Airport has its own standalone contingency plan with a different preset diversion: Ambulance → PMH, YCH, CMC. Helicopter → PYNEH. Boat → TMH. MTR ± ambulance (green cases) → QEH, KWH. [1]
- Burn Units: PWH, QMH
- Burn Facilities: KWH, QEH, TMH
- Patients are distributed in a rotating sequence between PWH and QMH for the first patients, then to burn facilities, then repeating the cycle [1]
QMH Major Incident Response Plan / Disaster Plan activation considered when: QMH is informed of an accident on Hong Kong Island involving ≥ 8 victims, OR RH/PYNEH declares full disaster activation. [1]
Successful disaster response requires well-defined leadership role. Those in charge require: clinical expertise to treat the injured, an understanding of hospital triage principles, experience in caring for patients when resources are scarce. [1]
Incident Command System (ICS): Needs to start early before an incident gets out of control. Medical responder must adhere to the structure of ICS. A unified command is important. The structure of the ICS must be the same. The key personnel may be different. [1]
Why ICS matters: Without a command structure, chaos ensues — resources get wasted, patients fall through cracks, communication breaks down. The ICS is a standardised management hierarchy that can scale up or down. In Hong Kong, you report to the Medical Controlling Officer (MCO) at the scene — this is directly tested (see 2023 MCQ Q3 below).
Multidisciplinary Team [1]
Trauma management involves: Surgeons, AED doctors, Orthopaedic Surgeons, Neurosurgeons, Anaesthetists, Intensivists, Nurses, Other paramedics. [1]
9. Case Studies
A 23-year-old motorcyclist with:
- Pelvic fracture
- Open fracture femur
- Bilateral haemopneumothorax
- Proximal descending aortic rupture
- Left zygomatic arch fracture
- Transfused 40 units of packed cells
- Intra-operative CPR twice
Teaching point: This demonstrates the concept of damage control resuscitation — massive transfusion, permissive hypotension, addressing the "lethal triad" (hypothermia, acidosis, coagulopathy), and staged surgical intervention. The aortic rupture at the isthmus is the classic location for traumatic aortic injury (where the mobile aortic arch meets the fixed descending aorta) [4].
Facts:
- 26,893 runners, > 500,000 spectators
- 3 killed at scene
- No patients who arrived at a hospital died
- 66% had lower extremity soft tissue and bony injuries
- MGH: 907 beds, 61 ORs
- 14:50 — 2 IEDs detonated; 15:03 — Disaster declaration; 15:04 — First patient arrived; 15:24 — First severely injured patient in OR
- 32 patients at MGH, 7 emergent surgical patients, all underwent amputation
Why zero in-hospital mortality? [1]:
- Adequate preparation — years of MCI drills
- Rapid logistical response
- Short transport time — median 11 minutes from explosion to hospital
- Immediate access to operating rooms
- Multidisciplinary care delivery
- Luck
Pre-hospital factors [1]:
- Community had planned and drilled for MCI for many years
- Medical tent at finish line converted to emergency triage unit
- "Scoop and run" policy — get patients to trauma centres fast, don't spend time on scene
- Field tourniquets: 31 patients had exsanguinating haemorrhage, 26 had field tourniquets in place
"Luck" factors [1]:
- Open-air bombing (closed-space explosions cause much higher mortality due to reflected blast waves)
- Ground level, lower-grade explosives
- 5 adult Level 1 trauma centres + 4 paediatric trauma centres nearby
- Streets cordoned off for runners → easy evacuation routes
- Patriots' Day holiday → light OR schedules
- Hospital ICS and surgical teams already in place
- Bombing at shift change → double staffing
Challenges [1]:
- Cell phone towers shut down → communication disruption
- Patient identification problems
- Surgeons unfamiliar with some procedures (e.g., traumatic amputation management)
In-hospital data [1]:
- Median ED length of stay: 106 minutes (range 10–481)
- 45 (60%) admitted directly to ORs
- 9.5% required emergent airway control
- 11.8% required immediate PRBC transfusion in ED
- 25% required CT scan in ED
- Damage control surgery: arrest bleeding, completion of amputations, external fixators, soft tissue debridement, foreign body removal
- 12 patients underwent above/below knee amputation
Scale:
-
6,500 injuries
- 220 deaths
-
150,000 homeless
- 1/3 of Beirut with structural damage
-
$15 billion USD in damage
Healthcare system impact [1]:
- 3 major hospitals completely non-functional → immediate patient evacuation needed
- 3 other major hospitals substantially damaged
- 600 hospital beds instantaneously lost
American University of Beirut experience [1]:
- 350-bed academic hospital, < 2 miles from blast
- Partial structural damage, many staff injured, 4 staff died
- Influx of injured patients within 10 minutes
- First 24 hours: 500 patients treated, 68 emergent surgical procedures (17 within first 4 hours)
- First 4 hours: 8 craniotomies, 3 amputations, 2 laparotomies, 2 ophthalmologic, 1 ENT, 1 sternotomy
- Next 4–12 hours: 1 neurosurgery, 2 ophthalmology, 12 orthopaedics, 8 plastic surgery, 2 ENT, 1 vascular
Challenges [1]:
- Capacity and resources immediately overwhelmed
- Staff among injured
- Friends and relatives among injured
- Everyone in state of shock and fear
- Very few wearing masks during COVID pandemic
- Most patients without identification
- Morgue filled quickly
- "Every medical student and resident was put to immediate action"
"The key to succeeding in responding to a catastrophic event is to anticipate the event, plan the response and practise the plan." [1]
"Paradigm change from the application of unlimited resources for the greatest good of each individual patient, to the allocation of limited resources for the greatest good of the greatest number of casualties." [1]
"Physician must possess sufficient familiarity with the incident command system and the community resources." [1]
11. Integration with Related Lectures
The primary survey ABCDE framework from this lecture is expanded in GC 207. Key additions:
- Adjuncts to primary survey: ECG monitoring, urinary catheter, gastric tube, trauma imaging
- Secondary survey: Head-to-toe examination only after primary survey is complete and resuscitation is underway
- Tertiary survey: 24-hour re-evaluation to catch missed injuries
- GCS classification: Mild (13–15), Moderate (9–12), Severe (3–8)
- Primary vs secondary brain injury distinction
- Indications for CT brain (GCS < 15 at 2 hours, any LOC with risk factors, focal neurological deficit, suspected open/depressed skull fracture)
- FAST scan protocol: Morison's pouch, splenorenal space, pelvis (Pouch of Douglas), subxiphoid (pericardium) [2]
- Unstable + FAST positive → laparotomy; Stable → CT
- Combined trauma and burns ( > 2nd degree or > 20%) triggers primary trauma diversion [1]
- Fluid resuscitation: Parkland formula (4 mL × kg × %TBSA for first 24h, half in first 8h)
- Always assume C-spine injury until cleared — this is why "A" includes C-spine protection
- ASIA classification for spinal cord injury grading
- Neurogenic shock (bradycardia + hypotension) must be distinguished from hypovolaemic shock (tachycardia + hypotension)
- 80–85% occur at the aortic isthmus (where mobile arch meets fixed descending aorta)
- CXR: widened mediastinum — this is the most important diagnosis to consider (2025 MCQ Q42) [8]
- Definitive diagnosis: CT angiogram
12. Exam Intelligence
| Theme | What They Test | Typical Correct Answer |
|---|---|---|
| On-site triage first step | How to rapidly sort acute vs non-acute | Ask victims to walk (walking = Green/non-acute) |
| Field vs AED triage | Philosophy difference | Field = greatest good for greatest number; AED = sickest first |
| ICS reporting structure | Who to report to at scene | Medical Controlling Officer (MCO) |
| Primary survey order | What comes first | Airway with C-spine protection |
| Widened mediastinum in trauma | Most important diagnosis | Acute traumatic aortic injury |
| Primary trauma diversion | Physiological threshold for GCS | GCS < 14 |
| Disaster definition vs MCI | What defines an MCI | Needs >>> Resources |
| Crush syndrome in disaster | Cardiac arrest after extrication | Hyperkalaemia → give calcium gluconate + insulin/dextrose |
- "Treat the sickest first" in MCI — Wrong in field triage. Correct answer is utilitarian approach.
- "Take detailed history before examination" — ATLS says no, start ABCDE immediately.
- Confusing neurogenic shock with haemorrhagic shock — Neurogenic = bradycardia + hypotension + warm peripheries. Haemorrhagic = tachycardia + hypotension + cold peripheries.
- FAST negative = no abdominal injury — False. FAST can miss parenchymal injuries without free fluid. CT is gold standard [3].
- Supine CXR for pneumothorax — Look for deep sulcus sign, not the classic apical lucency (that's on erect CXR) [3].
Past Paper Questions
Stem: "You are a team member of an Emergency Medical Team who responds to a mass casualty event. It involves an overturn of a double decker bus with more than 100 passengers extricated. To start, how would you rapidly differentiate those requiring emergency treatment and those who do not at scene?"
Options:
- A. Check all victims for normal pulsations of limbs
- B. Check all victims for the ability to breathe normally
- C. Check all victims for the ability to speak their names
- D. Check all victims for the ability to walk to another area
Correct Answer: D
Rationale: On-site triage (Level 1) divides victims into "acute" (Red) and "non-acute" (Green). The fastest way to sort > 100 casualties is to ask everyone who can walk to move to a designated area. Those who can walk are Green/non-acute. This is directly from the lecture: On-site triage = Acute (Red) vs Non-acute (Green), and the walking test is the standard first step in START triage and the lecture's Level 1 sorting [1].
Discriminator: Option B (breathing) is used in the next step of START triage to identify immediate vs expectant. Option C (speaking) tests airway patency but isn't the first sorting step. Option A (pulses) is too time-consuming for 100+ casualties.
Stem: "You are a junior emergency physician who joins the Emergency Medical Team to respond to a landslide affecting a huge natural hillside near the HKU main campus. To whom should you report to immediately after arrival, to facilitate resource management and liaison with stakeholders at the scene?"
Options:
- A. Ambulance control officer (ACO)
- B. Ambulance loading officer (ALO)
- C. Chief of Service (COS) of receiving Accident and Emergency Department
- D. Medical Controlling officer (MCO)
Correct Answer: D
Rationale: The Incident Command System requires a unified command. At the scene, the Medical Controlling Officer (MCO) is the person in charge of all medical responders. The lecture emphasises: "Medical responder must adhere to the structure of ICS" and "A unified command is important" [1]. The MCO coordinates resource allocation, triage decisions, and liaison with fire/police services at the scene.
Discriminator: The ACO and ALO manage ambulance logistics, not overall medical command. The COS is at the hospital, not at the scene.
Stem: "The chest radiograph of the driver involved in a head-on collision road traffic accident showed widened mediastinum, what would be the MOST IMPORTANT diagnosis to consider?"
Options:
- A. Acute traumatic aortic injury
- B. Haemoperitoneum
- C. Haemothorax
- D. Tension pneumothorax
Correct Answer: A
Rationale: Widened mediastinum on CXR in a high-energy deceleration injury (head-on collision) is the hallmark of acute traumatic aortic injury until proven otherwise. 80–85% occur at the aortic isthmus. This is a potentially lethal injury that requires urgent CT angiogram and surgical/endovascular repair [4]. Haemothorax would show opacification of hemithorax, not mediastinal widening. Tension pneumothorax shows mediastinal shift and absent lung markings. Haemoperitoneum is intra-abdominal and not visible on CXR.
Stem: "A 40-year-old motorcyclist sustained injury to his pelvis in a road traffic accident. Despite resuscitation in the emergency room, the blood pressure remained unstable at 80/42 mmHg. Anteroposterior X-ray of the pelvis taken at the emergency room showed pelvic fracture. Which of the following is the MOST APPROPRIATE next step?"
Options:
- A. Arterial embolisation
- B. External fixation
- C. Open exploration and ligation of bleeding vessel
- D. Urgent computed tomography scan of the pelvis
Correct Answer: A (Arterial embolisation)
Rationale: In haemodynamically unstable pelvic fracture that does not respond to initial resuscitation (fluids + pelvic binder), angiographic embolisation is the most appropriate next step to control arterial bleeding. External fixation (B) helps reduce venous bleeding by reducing pelvic volume but is usually a temporising measure already applied (pelvic binder). CT (D) is inappropriate in an unstable patient. Open exploration (C) is generally not the first approach for pelvic haemorrhage — the bleeding is usually from small arteries/venous plexus in the retroperitoneum, which is difficult to control surgically and better managed by interventional radiology.
Stem: "A 28-year-old man is trapped under rubbles from waist down after an earthquake. When he is found by the rescue team, he has already been trapped for around six hours. He is alert and only complains of pain in the lower limbs. No open wounds are noted. Vitals: BP 130/90, pulse 80/min, RR 15/min."
(a) Apart from pain control, what treatment will you start during the extrication process? (1 mark) Answer: IV normal saline (aggressive fluid resuscitation) — to prevent acute kidney injury from rhabdomyolysis by maintaining renal perfusion and diluting myoglobin.
(b) Name four important signs of a limb-threatening injury when you examine the limbs after extrication. (4 marks) Answer: Pain out of proportion / pain on passive stretch (compartment syndrome), pallor, pulselessness, paraesthesia (± paralysis) — the 5 P's of limb ischaemia/compartment syndrome.
(c) If crush syndrome is suspected, what finding in urine test suggests the diagnosis? (1 mark) Answer: Myoglobinuria (dark/tea-coloured urine, positive for "blood" on dipstick but no RBCs on microscopy).
(d) If cardiac arrest occurs 5 minutes after extrication, what is the likely cause? What drug? (2 marks) Answer: Hyperkalaemia (from sudden release of intracellular potassium from crushed/necrotic muscle into systemic circulation). IV calcium gluconate (cardioprotective — stabilises cardiac membrane) + insulin with dextrose (drives K+ intracellularly).
(e) What can prevent acute renal failure in the pre-hospital phase? (2 marks) Answer: Aggressive IV fluid resuscitation (NS) before and during extrication; consider IV sodium bicarbonate to alkalinise urine and prevent myoglobin precipitation in renal tubules.
Stem: "Which of the following is the BEST imaging modality to look for intracranial haematoma in a patient with an acute head injury?"
Options:
- A. Computed Tomography (non-contrast)
- B. Magnetic Resonance Imaging
- C. Skull X-ray
- D. Ultrasound
Correct Answer: A
Rationale: Non-contrast CT brain is the gold standard for acute head injury imaging — fast (completed in seconds), readily available, and highly sensitive for acute blood (hyperdense on CT). MRI is more sensitive for diffuse axonal injury and subacute/chronic changes but takes too long and is less practical in acute trauma. Skull X-ray can show fractures but misses intracranial pathology. Ultrasound cannot penetrate the adult skull.
- "Walk me through the management of an MCI at the scene" — Describe the 4 phases, emphasise safety first, Level 1 triage (walk test), Level 2 medical triage (cruciform tag), evacuation
- "What is the difference between field triage and AED triage?" — Greatest good for greatest number vs sickest first
- "A patient arrives from an MCI — describe your primary survey" — ABCDE with specifics for each step
- "What are the primary trauma diversion criteria?" — List anatomical and physiological criteria
- "What lessons can we learn from the Boston Marathon bombing response?" — Preparation, drilling, short transport times, OR access, multidisciplinary care, damage control surgery, field tourniquets
- "What is crush syndrome and how do you manage it?" — Link to earthquake/disaster context, rhabdomyolysis, hyperkalaemia, aggressive fluids, monitor for AKI
High Yield Summary
Disaster/MCI: Needs >>> Resources. Paradigm shifts from individual best care to greatest good for greatest number.
Classification: Natural (earthquake, flood, typhoon) vs Man-made (war, transport, terrorism, industrial) vs Disease.
Four Phases of MCI Response: Search & Rescue → Triage & Stabilisation → Definitive Care → Evacuation.
On-Site Triage (Level 1): Walking test → Acute (Red) vs Non-acute (Green). Medical Triage (Level 2): Cruciform tag by experienced personnel.
Field Triage ≠ AED Triage: Field = utilitarian; AED = sickest first.
ATLS ABCDE: Airway + C-spine → Breathing → Circulation + haemorrhage control → Disability → Exposure. Treat greatest threat to life first; do not wait for history.
Primary Trauma Diversion (HK): GCS < 14, SBP < 90, RR < 10 or > 29, flail chest, pelvic fracture, penetrating injuries to head/neck/torso, limb paralysis, amputation proximal to wrist/ankle, two long bone fractures, combined burns > 2°/20%.
Trimodal death: Immediate (not salvageable) → Early (golden hour, ATLS saves lives) → Late (sepsis, MOF).
ICS: Start early, unified command, report to Medical Controlling Officer at scene.
Boston lessons: Preparation + drilling + short transport + field tourniquets + "scoop and run" + damage control surgery = zero in-hospital mortality.
Crush syndrome in disasters: Pre-hydrate before extrication, watch for hyperkalaemia on release, myoglobinuria, AKI.
Active Recall - Lecture Notes
[1] Lecture slides: GC 175. A bus hit a train Multiple trauma; Disaster management.pdf [2] Senior notes: Maksim Surgery Notes.pdf (Section 2.1 Trauma) [3] Senior notes: Ryan Ho Radiology.pdf (FAST and CT in trauma) [4] AOS material: AOS - Radiology.pdf (Acute Traumatic Aortic Injury) [5] Lecture slides: GC 207. Trauma Evaluation and Management (TEAM).pdf [6] Senior notes: MBBS Final MB (Surgery) (Felix PY Lai).pdf (Head Injury section) [7] Senior notes: Ryan Ho Neurology.pdf (Spinal Trauma section) [8] Past papers: 2025 Fourth Summative MCQ.pdf (Q42, Q45) [9] Past papers: 2022 Fourth Summative MCQ.pdf (Q3) [10] Past papers: 2023 Fourth Summative MCQ.pdf (Q3) [11] Past papers: 2017 Fourth Summative SAQ.pdf (Q9) [12] Past papers: 2020 Fourth Summative Assessment MCQ paper.pdf (Q1)
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