Disaster And Related Emergency Flashcards
Disaster
Serious disruption of functioning of community / society causing widespread human, material, economic / environmental losses which **exceed ability of affected community to cope using its **own resources
Most common disasters and location
Flood, China
***Types of disaster (WHO)
Natural:
- Geophysical
- Earthquake
- Volcano
- Mass movement (Dry) - Climate-related
- Hydrologic: Flood, Mass movement (Wet)
- Meterologic: Storm, Extreme temp, Wildfire - Biological
- Epidemic disease
- Pests infestations
Man-made:
- Technological
- Chemical substance
- Radiological agents
- Transport crashes - Societal
- Conflict / War
- Stampedes
- Terrorism
Other classifications:
1. Duration (Brief, Short, Intermediate, Prolonged) + Onset (Sudden / Gradual / Slow)
***Disaster management cycle
- ***Response
- Basic relief needs (water, food, sanitation, shelter)
- Healthcare needs (trauma care, mental health care, chronic illness care, remains handling) - ***Recovery
- Primary care
—> Children: nutrition, immunisation
—> Women: child birth
—> Chronic illnesses
- Public health
—> Mental health (Anxiety, Depression, PTSD)
—> Disease surveillance
—> Prevent / Control outbreak of infectious diseases - Mitigation
- Preparation
Disaster medical response
- Search + Rescue
- Triage + initial stabilisation
- Definitive medical care
- Evacuation
Communicable diseases associated with natural disaster
- Water-related
- Cholera
- Leptospirosis
- Hep A, E - Overcrowding-related
- Measles
- Chicken pox - Vector-borne
- Malaria
- Dengue - Other diseases
- Tetanus
- Fungal infections
- Pneumonia
- Encephalitis
Emergency Response System in HK
Tier 1: **Isolated events (e.g. simple car crash) —> FSD (Ambulance), Police, GFS, HA
Tier 2: **Many casualties (e.g. fire) —> Security bureau duty officer / Emergency support unit
Tier 3: Severe + ***widespread consequences (e.g. typhoon) —> Emergency monitoring + support centre (involving CE)
FSD (Ambulance): On-site rescue + transport of casualties
Police: establish Command post at scene + secret outer cordoned zone surrounding the site
HA: provision of hospital services, dispatch medical teams for on-site triage + treatment
HAD: coordinate relief items with Social welfare department, Housing department / other agencies
EMSC: update Government senior officials
4”C”s + 2”T”s:
- Coordination
- Command (Emergency Executive Committee (EEC), Central Command Committee (CCC), Major Incident Control Centre (MICC))
- Control
- Casualty diversion
- Triage
- On-scene treatment
Common injuries seen in victims trapped in collapsed structures
- Fractures
- Multiple trauma
- Closed head injury
- Hypothermia
- Dehydration
- ***Crush injury / syndrome
- Laceration / punctures
- Dust inhalation
- Hazardous material issues
Initial assessment of patient under rubble
Airway: assume airway compromised
Breathing: assume ventilation impaired secondary to dust / noxious gases inhalation and direct trauma
Circulation: assume hypovolaemia, crush injury
Disability: assume neurologic examination incomplete
Exposure: assume hypothermia, expose body parts only if deemed absolutely necessary for saving life
Crush injury
At risk:
- All patients crushed / immobilised for ***>=4 hours
Consequence of muscle injury: 1. Disintegration of striated muscles —> Swelling of muscles —> Pressure effect on surrounding structures —> ***Compartment syndrome —> Further ischaemia —> Further muscle damage —> Further muscle swelling —> Vicious cycle
- Rhabdomyolysis
—> Release of muscular cell contents into ECF
—> Systemic manifestations = ***Crush syndrome
- **Metabolic consequences:
1. HyperK
2. HyperPO4
3. HypoCa
4. Hyperuricaemia
5. Myoglobinaemia —> Red discolouration of urine
6. ↑ CK
7. ↑ Creatinine / Urea (∵ Acute kidney injury)
8. Metabolic lactate acidosis —> further deteriorate HyperK -
Systemic effects:
1. Hypovolaemia
2. Electrolyte imbalance
3. **Acute renal failure
4. **Arrhythmia
5. Sepsis (∵ wound)
6. **ARDS (prodrome for death)
7. **DIC (∵ massive bleeding / sepsis)
Acute renal failure
Causes:
- ***↓ Intravascular volume —> Acute tubular necrosis
- **Myoglobin + Uric acid (potentiated by acidosis + urine concentration) —> **Cast —> Tubular damage
- ***Microthrombi (∵ DIC) —> deposited in glomerular tufts
Prevention of Acute renal failure:
- ***Normal saline (1L / hour (a lot)) (10-15 ml/kg/hour)
- Monitor BP + urine output
- ***Never give K containing solution (∵ patient already HyperK)
- ***Forced alkaline diuresis
- NaHCO3
- Mannitol - Urine volume + pH maintenance
- volume **300 mL/hr
- pH **>6.5 - Dialysis
- 50% of crush syndrome develop ARF —> 50% of ARF require dialysis
“Rescue Death”
Metabolic causes:
- Influx of plasma into muscles
- Efflux of muscle breakdown products —> Acidosis, HyperK
- Influx of Ca into cells
Bleeding causes:
1. Tamponade effect removed in Pelvic fracture / Abdominal bleeding
***Causes of cardiac arrest
5H:
- Hypoxia
- Hypovolaemia
- HyperK
- Hydrogen (Acidosis)
- Hypothermia
5T:
- Tension pneumothorax
- Tamponade
- Thrombosis (Coronary)
- Thrombosis (Pulmonary)
- Toxin
HyperK treatment
Acute:
- ***CaCl
- counter adverse effect of HyperK on myocardium - ***Glucose insulin drip / Beta agonist (e.g. Ventolin) / NaHCO3
- shift K back to cell
Compartment syndrome
Compartment pressure > Filling pressures of arterioles of muscle
6P:
- Pain
- Pallor
- Paresthesia
- Paralysis
- Perishing cold
- Pulselessness
Treatment:
1. Fasciotomy
- if pressure ***>40 mmHg
—> NO need anaesthetic (∵ already numbed)
—> Stop until bleeding (i.e. indicate reperfusion)
- Amputation
- must for urgent life saving
—> difficult decision (life saving vs limb saving)
- depend on salvageability of the trapped limb
—> is vascular injury reparable?
—> can skeletal injury be reconstructed?
—> is the soft tissue viable / can adequate soft tissue coverage be achieved?
—> is innervation present / possible?
Physiological changes at high altitude
Altitude↓
—> Barometric pressure↓, Ambient PO2↓, PiO2↓
***PiO2 = (Pb - SVP) x FiO2
- PiO2: Partial Pressure of Inspired Oxygen
- Pb: Barometric pressure
- SVP: Saturated vapour pressure at body temp (47 mmHg)
- FiO2: Fraction of inspired oxygen (normal: 21%)
How body function with low SaO2 + PaO2?
**O2 delivery = O2 content x CO
- O2 content in 100ml blood
= O2 combined with Hb + O2 dissolved in plasma
= (Hb x 1.36 x SaO2) + (0.0031 x PaO2)
- O2 content can be maintained despite fall in SaO2 and PaO2 if **Hb is adequate
- Hb will ↑ as an adaptation
High altitude illness
High altitude:
- ***2500-3500m
- Arterial saturation ***>85-90%
High altitude sickness:
- common when individuals when ascend rapidly
- HACE: High altitude cerebral edema
- HAPE: High altitude pulmonary edema
- Cause: ***Hypobaric hypoxia
Early symptoms: - Headache (different from other causes of headache by giving O2) - Loss of appetite - Dizziness - Fatigue on minimal exertion —> ***Don’t go higher, ***Rest, ***Fluid —> Symptoms go away —> Continue go up —> Symptoms get worse —> Go down
Worsening symptoms: - Severe headache - Vomitting - Walking like a drunk - Increasing tiredness —> ***Descend with accompaniment
High altitude cerebral edema (HACE)
Pathophysiology: Hypoxia —> Hypoxaemia —> 1. ***↑ Cerebral blood flow —> ↑ Capillary pressure —> Brain swelling
- ***↑ Cerebral blood volume
—> Brain swelling - ***↑ Permeability of BBB
—> Brain swelling
—> Inadequate buffering by CSF
—> AMS (Acute mountain sickness i.e. mild)
—> HACE (severe)
Diagnosis of AMS:
- **Lake Louise AMS score
—> questionnaire on symptoms during ascent
—> scoring system to assess severity of illness
1. Headache
2. GI symptoms
3. Fatigue
4. Dizziness
5. AMS clinical functional score
- AMS = **Altitude gain + **Headache + **Total symptom score >=3
Diagnosis of HACE: - ***Lake Louise Criteria for HACE - HACE: >=2 of following: 1. AMS 2. ***Altered mental status 3. ***Ataxia (是但兩個)
Cautions: - need to assess whole situation: —> Altitude —> Ascent rate —> Alternative Dx (e.g. flu)
Management of HACE
Mild AMS:
- ***Descend >=500m
- Acclimatisation for 1-2 days
- Avoid ascent until S/S subsided
- ***Acetazolamide 125-250 mg BD
Moderate AMS:
- Descend
- ***O2 (1-2 L/min)
- ***Portable hyperbaric therapy (2-4 psi) x 6 hours
- Acetazolamide 125-250 mg BD
- ***Dexamethasone 4mg Q6H IM/PO (for cerebral edema)
HACE:
- Immediate descend / evacuation >=1000m
- O2 to keep SpO2 >=90%
- Dexamethasone 8mg STAT IV/IM/PO —> then 4mg Q6H
- Portable hyperbaric therapy if cannot descend
Hyperbaric therapy SE: Hyperbaric trauma (e.g. Pneumothorax, Pneumotympanum)
Acetazolamide
- Diamox
- Carbonic anhydrase inhibitor
- Induce renal excretion of HCO3 —> induce ***Metabolic acidosis —> trick body to hyperventilate —> speed up acclimatisation process to relieve symptoms
- Counter respiratory alkalosis due to hyperventilation
- SE: GI upset, Tingling in hands, Abnormal taste in tongue
(From SC008: Carbonic anhydrase inhibitor: Altitude sickness Prevent carbonic acid breakdown —> Accumulation of carbonic acid —> Lower blood pH —> Hyperventilation
Carbonic anhydrase: - in RBC, Proximal tubule —> reabsorb Na, Cl, HCO3, Ciliary body —> Aqueous production - when inhibited —> Na, Cl, HCO3 excreted —> diuresis —> excretion of excess water —> ↓ BP, ICP, IOP)
High altitude pulmonary edema (HAPE)
DDx of High altitude SOB:
- Asthma
- Bronchitis
- Heart failure
- Hyperventilation syndrome
- Mucus plugging
- MI
- Pneumonia
- PE
Pathophysiology: Rapid ascent —> Lack of acclimatisation —> Accentuated ***alveolar hypoxia —> Accentuated ***pulmonary HT (also induced by cold, exercise) —> Mechanical stress on endothelium —> Vulnerable endothelium / epithelium (also induced by viral infection) —> Fluid leak —> ***Interstitial and Alveolar edema —> ***HAPE —> Hypoxia —> Worsen pulmonary HT (+ potentially HACE) —> Vicious cycle
Inherent characteristics for pulmonary HT:
- Blunted hypoxic ventilatory response
- Brisk hypoxic pulmonary vascular response (i.e. vasoconstriction)
- Decreased NO synthesis
- Increased sympathetic tone
- Genetic determinants
Diagnosis of HAPE: ***Lake Louise Consensus Definition Symptoms (>=2): - SOB at rest - Cough - Weakness / Decreased exercise performance - Chest tightness / congestion
Signs (>=2):
- Crackles / wheezing in >=1 lung field
- Tachypnea
- Tachycardia
- Central cyanosis (desaturation)
Management of HAPE
- ***O2 (4-6 L/min until improved —> then 2-4 L/min to keep SpO2 >=90%)
- Minimise exertion
- Descend / Evacuation >=1000m
- ***Portable hyperbaric therapy if cannot descend
- ***Nifedipine 10mg PO (pulmonary artery vasodilation) —> then 30mg SR QD/BD
- ***Inhaled Beta agonist (e.g. Ventolin)
- EPAP mask
- Dexamethasone (only if HACE develops)
Hypothermia
Rule of 3 in survival:
- 3 mins without air
- 3 hours without shelter (Hypothermia)
- 3 days without water
- 3 weeks without food
Hypothermia:
- Core body temp ***<35oC (95oF)
- Mild: 32-35oC
- Moderate: 28-32oC
- Severe: <28oC
Environmental temp determined by:
- Ambient temp
- Wind speed (protected by shelter) —> Wind Chill Chart
Causes:
- Environmental
- Sepsis
- Hypothyroidism
- Alcohol (diuretic + vasodilation)
- Opioid (sedation)
Physiological response to cold
- Vasoconstriction
- Lateral Spinothalamic tract —> Hypothalamus
- Shivering
- Stress hormone release (ACTH, TSH, Insulin, Catecholamine) - Behavioural
- Put on more clothing
Pathophysiology of Hypothermia
All cells + tissues affected —> Organ dysfunctions
- CNS depression
- Cardiac depression / arrhythmia
- Respiratory depression
- Metabolic acidosis (∵ Inadequate perfusion)
- Volume depletion (∵ cold-induced diuresis)
(Cold-induced diuresis: - Peripheral vasoconstriction —> ↑ Central blood volume —> Inhibition of ADH release —> Diuresis)
***Diagnosis of Hypothermia
- Clinical S/S (***”Umbles”)
- Stumble (ataxia, unsteady gait)
- Grumble (dysarthria)
- Mumble (cannot express clearly)
- Fumble (clumsiness of hand)
- Marble (torso feels like cold marble)
35oC: **maximum shivering thermogenesis
34oC: **maximum respiratory stimulation
33oC: **ataxia + apathy
32oC: stupor
31oC: **extinguished shivering thermogenesis
30oC: ***dilated + less reactive pupil, arrhythmia (e.g. AF)
29oC: decrease in level of consciousness, paradoxical undressing
28oC: decreased VF threshold
27oC: loss of reflexes
26oC: major acid-base disturbance
25oC: cerebral blood flow 1/3 of normal, loss of cerebrovascular autoregulation, CO 45% of normal, pulmonary edema may develop
24oC: significant hypotension + bradycardia
- Low reading thermometer
- Rectal (time lag ~30 mins, but ***more accurate)
- Tympanic
- Mid-esophagus (real time but invasive)
Initial management of Hypothermia
- ABC resuscitation
- Monitoring CVS system, Deep rectal temp
- Prevent heat loss
- move patient to warm environment
- create good shelter to protect from wind
- insulate from ground
- insulate the patient
- remove wet clothing (to eliminate evaporative heat loss)
- cover with vapour barrier (e.g. garbage bag) - Rewarm
- ***Passive (for mild hypothermia)
—> wrap up patient for insulation
—> provide drink with glucose
-
**Active external (for moderate / severe hypothermia)
—> hot pad (beware of excessive heat causing burn)
—> lying by side of normothermic person in a sleeping bag
—> do **NOT rub / massage —> damage to skin —> worsen thermodamage - ***Active core
- Treat underlying problems
- e.g. sepsis, metabolic disorder, drug overdose - Consider evacuation
- all patients other than mild hypothermia (esp. those with trauma / other problems)
ED management of Hypothermia
Mild (32-35oC):
- Thermoregulatory mechanism intact
- Keep away from cold environment
- ***Passive rewarming
- May consider External rewarming
- Warm IV fluid replacement if prolonged exposure (X Dextrose solution ∵ bacterial growth in thawed solution)
Moderate / Severe:
- ***Active external rewarming (for moderate hypothermia)
- **Active core rewarming (necessary for **cardiovascular instability)
- Target >1oC / hour (depending on CVS status)
External + Core rewarming rate
External:
- Simple blanket: 0.5 oC/hr
- Space blanket: 0.6 oC/hr
- Warmed blanket: 0.9 oC/hr
- Whole body immersion: 2.2 oC/hr
- Forced air: 2.4 oC/hr
Core:
- Chest tube lavage (500 mL/min): 6.1 oC/hr
- Chest tube lavage (2 L/min): 19.7 oC/hr (SE: infection, organ bleeding, injury)
- Peritoneal lavage: 1-3 oC/hr
- Extracorporeal: 2.1 oC/hr
- Cardiopulmonary bypass: 6.9 oC/hr
- Heated O2 by mask: 0.7 oC/hr
- Heated O2 by ETT: 1.2 oC/hr
- Warmed IV fluid: 0.3 oC/hr
- Gastric lavage: 1-1.5 oC/hr
- Bladder lavage: 1-1.5 oC/hr
Complications of rewarming
- Rewarming ***shock (∵ marked vasodilatation by rewarming)
- Rewarming ***acidosis (∵ recirculation of pooled lactic acid)
- ***Afterdrop effect (∵ cold peripheral blood rapidly returns to heart —> minimised by core rewarming before external rewarming)
Pre-hospital management of apparent cardiac arrest
- Ventilate for ***3 mins if no pulse detected initially after 30-60s (long period pulse detection required ∵ profound bradycardia)
- Avoid hyperventilation (∵ alkalosis may precipitate VF) - Start CPR if no pulse detected ***after ventilation, optimal rate unknown
- do NOT start CPR immediately after no pulse detected ∵ CPR may precipitate VF / asystolic (∵ cardiac membrane sensitive to movement)
Frostbite
Cold exposure, particular temp ***< -15oC
—> Tissue hard, pale, anaesthetic
Grading:
- 1st degree: only outer part of skin, no lasting problems
- 2nd degree: clear blister
- 3rd degree: haemorrhagic blister
- 4th degree: full thickness skin damage —> no blister
Management:
- Treat hypothermia first
- Prevent further cold injury
- Maintain hydration
- Protect frostbitten tissue with ***dry, bulky dressing
- ***Ibuprofen (for anti inflammatory + analgesic effect)
-
Thawing
- circulate warm (37-39oC) water around frozen tissue in a bath for 30mins
- analgesic for pain during rewarming
Don’t:
- Rub frozen part
- Apply ice / snow
- Thaw frostbitten part in cold water
- Thaw frostbitten part with high temp (e.g. stoves)
- Break blister
- Alcohol / Tobacco
Prevention:
- Keep skin dry + warm
- Extremity at risk for frostbite (e.g. numb, poor dexterity, pale colour) —> warmed with adjacent body heat
