Disaster medicine - High altitude emergencies, Cold related emergencies, Crush syndrome Flashcards
Define ‘disaster’
WHO definition:
A serious disruption of the functioning of a
community or a society causing widespread
human, material, economic or environmental
losses , which exceed the ability of the affected
community or society to cope using its own
resources.
CRED definition:
“a situation or event, which overwhelms local capacity, necessitating a request to national or
international level for external assistance; an
unforeseen and often sudden event that
causes great damage, destruction and human
suffering”.
List types of disaster
Natural:
* Earthquake, landslide, tsunami, cyclones, flood or drought.
* Biological: epidemic disease, infestations of pests.
Man-made:
* Technological: chemical substance, radiological agents, transport crashes.
* Societal: conflict, stampedes, acts of terrorism.
Most prevalent reported disasters
Subtotal climato-, hydro-, meterological disasters
Floods
Transport accidents
Windstorms
Industrial accidents
Outline the disaster management cycle
Define the Sphere project minimum standard for basic disaster relief
Water, sanitation and hygiene promotion
- 2-4 gallons of portable water per person (including intake, hygiene and cooking needs)
- Maximum of 20 persons per toilet
- Handwashing and personal hygiene
- Avoiding mosquito exposure
- Solid waste management
Shelter
- Minimum space of 38 sqft per person
- Comfortable bedding
- Proper access for disabled
Define the sphere project minimum standard for medical relief
Health services
- Trauma care
- Mental health care
- Chronic illness care
- Handling remains of the dead
Outline the variation of needs and priority during acute phase of a disaster
List some communicable diseases associated with natural disasters
- Water-related communicable diseases
(diarrheal diseases, cholera, leptospirosis,
hepatitis A and E). - Diseases associated with overcrowding
(measles). - Vector-borne diseases (e.g., malaria, dengue).
- Other diseases (e.g., tetanus, fungal infections).
Healthcare provided at acute and recovery phase of disaster management
Disaster medical response in acute phase
- Search and rescue
- Triage and initial stabilization
- Definitive medical care
- Evacuation
Recovery phase:
Primary care
– Children: nutrition, immunization
– Women: child birth etc
– Chronic illnesses
Public Health
– Mental health
– Disease surveillance
– Prevent/Control outbreaks of infectious ds
Examples of mental health problems a/w disasters
Anxiety disorder/ Acute stress (ACU)
Moderate-severe Depression disorder (DEP)
PTSD
Psychosis
Epilepsy/Seizures
Intellectual disability
Suicide
Harmful substance abuse
Define the HK three tier emergency response system
- Tier 1: isolated events such as rescuing a
person from a car crash - Tier 2: an event with many casualties e.g. fire
in a high rise building - Tier 3: events having severe and widespread
consequences such as effects of a typhoon.
Parties involved in the rescue phase of HK emergency response system
- FSD (Ambulance): on-site rescue and transport of
casualties - The Police: establish a Command Post at the scene and
secure the outer cordoned zone surrounding the site. - Hospital Authority: provision of hospital services,
dispatch medical teams for on site triage and treatment - HAD: coordinate relief items with Social Welfare
Dept.(SWD), Housing Dept. and other agencies - EMSC: update Government senior officials
Structure within HA:
EEC = Emergency Executive Committee
CCC = Central Command Committee
MICC = Major Incident Control Centre
Is international support always needed for disaster relief
Issues with international response
- Depends on any unmet immediate needs after assessment
- The local population almost always covers immediate lifesaving needs
- Only medical personnel with skills not available in the affected country may be needed
e.g. foreign military support or resource support
Problems:
- Duplication of resource
- Fragmentation of support
- Inco-ordination
- Lack of relevant experience/ competence/ capacity
Foreign medical team (FMT) basic requirement
FMT trained using competency-based curriculum to provide care in austere environments
Sterilization: Basic steam autoclave or disposable equipment
Logistics: Self-sufficient team +/- OPD facility self sufficient
FMT size:
- At least 3 doctors specialists trained in emergency and primary care
- 1:3 doctor: nurse ratio
- Staff skilled in emergency and trauma care, maternal and child health, knowledge of endemic disease management
- FMT capacity: 100+ OP consultation per day for 2 weeks
Roles of foreign medical team
High altitude illness
Define high altitudes associated with altitude sickness
High: 2500-3500m, altitude sickness common when individual ascend rapidly
Very high: 3500-5800m, Altitude sickness common
Physiological changes at high altitude
- Hypobaric hypoxia (ambient PO2 decreases with lower barometric pressure at high altitude)
- Acute mountain sickness (AMS) S/S: Headache, Loss of appetite, Dizziness, Fatigue on minimal exertion, increasing tiredness, vomiting
- High altitude cerebral edema (HACE): Altered mental status (confusion, drowsiness, ataxia)
- High altitude pulmonary edema: Dyspnea at rest, moist
cough, rales, severe exercise limitation, cyanosis, tachypnea, tachycardia, desaturation
Diagnosis of acute mountain sickness
Treatment
Lake Louise AMS score: assesses severity of illness by questionnaire of symptoms during ascent
AMS Diagnosis:
- Altitude gain + Headache + Total symptoms score ≥ 3
Mild AMS:
* Descend ≥ 500m
* Acclimatization x 1-2/7
* Avoid ascent till s/s subsided
* Acetazolamide 125-250mg bd
Moderate AMS:
* Descend
* O2 (1-2L/min)
* Portable hyperbaric therapy (2-4psi) x 6hr
* Acetazolamide 125-250mg bd
* Dexamethasone 4mg Q6H IM/PO
Diagnosis of High Altitude Cerebral Edema (HACE)
Treatment
Lake Louise Criteria for HACE
- AMS + Altered mental status or Ataxis
or
- Altered mental status + Ataxia
Treatment
* Immediate descent/evacuation ≥ 1000m
* O2 to keep SpO2 ≥ 90%
* Dexamethasone 8mg stat IV/IM/PO, then 4mg Q6H
* Portable HBT if cannot descend
Acetazolamide/ Diamox
- MoA
- S/E
- Use
MoA:
* Carbonic anhydrase inhibitor
* Induce renal excretion of HCO3, causing metabolic acidosis
* Counter respiratory alkalosis due to hyperventilation
Side effects: GI upset, tingling in hands
Examples of protable hyperbaric therapy
MoA
Gamow Bag Inflation
MoA: Positive pressure inflation into sealed body bag, increasing local pressure and relieving hyperbaric hypoxaemia
Ddx High-altitude SOB
- High-altitude pulmonary edema
- Asthma
- Bronchitis
- Heart failure
- Hyperventilation syndrome
- Mucus plugging
- Myocardial infarction
- Pneumonia
- Pulmonary embolus
Pathophysiology of high altitude pulmonary edema
High Altitude Pulmonary Edema
Diagnostic criteria
Management
Symptoms: at least two of:
– SOB at rest
– Cough
– Weakness or decreased exercise performance
– Chest tightness or congestion
Signs: at least two of:
– Crackles or wheezing in at least one lung field
– Tachypnea
– Tachycardia
– Central cyanosis
Management:
* O2 (4-6L/min till improved, then 2-4L/min to keep SpO2 ≥ 90%)
* Minimize exertion
* Descent/evacuation ≥ 1000m
* Portable HBT if cannot descend
* Nifedipine 10mg PO then 30mg SR QD/BD
* Inhaled B-agoinist (ventolin®)
* EPAP mask
* Dexamethasone only if HACE develops
Define rules of 3 in survival
People can survive:
* 3 minutes without air
* 3 hours without shelter
* 3 days without water
* 3 weeks without food
Define hypothermia and severity grades
Method of diagnosis
S/S
Hypothermia: Core body temperature
< 35C (or 95F)
Method of diagnosis: Low reading thermometer, Rectal temperature, Clinical S/S
Mild 32-35: Tachypnea, Tachycardia, Dysarthria, Shivering
Moderate 28-32: Loss of shivering, diminished consciousness
Severe <28: Coma, Loss of reflexes, Ventricular fibrillation
Pathophysiology of hypothermia
All cells and tissues affected, resulting in different organ dysfunctions
* CNS depression
* Cardiac depression / arrhythmia
* Respiratory depression
* Metabolic acidosis
* Volume depletion due to cold-induced diuresis
S/S when body temperature is between 37 - 33/ Mild hypothermia
S/S when body temperature is between 32-29/ Moderate hypothermia
S/S when body temp is below 28/ Severe hypothermia
Management of hypothermia
Initial management:
- ABC resuscitation
- Monitoring: CVS, deep rectal temp
- Prevent heat loss: Move to warm environment, shelter from wind (wind-chill effect), Insulate from ground, Insulate patient (esp. head), Remove wet clothing, Cover with vapor barrier (e.g. plastic bag)
- Rewarming:
Passive rewarm with insulation (simple/ space/ warmed blanket) and glucose drink,
Active external rewarm with hot pad/ lying next to normothermic person in sleeping bag, forced hot air, whole body immersion …
Active core rewarm: e.g. chest tube lavage, peritoneal lavage, cardiopulmonary bypass, heated O2 mask…
- Treat underlying cause: e.g. sepsis, OD, metabolic disorder rewarm
- Consider evacuation (only except mild hypothermia)
*do no rub cold extremities for rewarming
Summarize management of mild, moderate and severe hypothermia
Mild: core temp > 32C
- Passive rewarming: insulation and glucose drink
- Consider external rewarming
- Prevent heat loss
- IV fluid replacement for prolonged exposure
Moderate and severe:
- Active External rewarming (hot pad, lie next to normothermic person)
- Active core rewarming for cardiovascular unstable
- Increase temp >1C/ hour
Methods of active external rewarming
Methods of active core rewarm
Complications of rewarming hypothermia patient
During rewarming, beware of peripheral vasodilatation causing
* rewarming shock
* rewarming acidosis
* afterdrop effect (decrease core temp.)
Frostbite
S/S
Management
S/S:
- cold exposure, particularly at temperatures below −15° C
- Tissue hard, pale, anesthetic
Management:
* Treat hypothermia first
* Prevent further cold injury
* Maintain hydration
* Protect the frostbitten tissue with dry, bulky dressing
* Give ibuprofen for anti-inflammatory and analgesic effect
Thawing: Circulate warm (37° to 39° C ) water around frozen tissue in a bath for 30 minutes + Analgesic for pain during rewarming
What to avoid when treating frostbites
- do not rub the frozen part;
- do not apply ice or snow;
- do not attempt to thaw the frostbitten part in cold water;
- do not attempt to thaw the frostbitten part with high temperatures e.g. by stoves,
- do not break blisters
- no alcohol or tobacco
Prevention of hypothermia
- Keep skin dry and warm
- An extremity at risk for frostbite (eg, numb, poor dexterity, pale color) should be warmed with adjacent body heat
Common injuries in victims trapped under collapsed structures
Initial assessment of patient trapped under rubble
- Scene safety first
- Airway: assume compromised
- Breathing: assume ventilation impaired secondary to dust/ noxious gas inhalation/ direct trauma
- Circulation: assume hypovolemia, crush injury
- Disability: assume imcomplete neurological exam
- Exposure: assume hypothermia, expose body parts only if necessary for saving life
Crush syndrome
Onset time
Pathophysiology
S/S
Onset time: all patients who are crushed or immobilized
for 4 hours or longer are at risk
Pathophysiology:
- Disintegration of striated muscles > swelling of muscles > pressure effects on surrounding structures
- Rhabdomyolysis > release of muscular cell
contents into the extracellular fluid > systemic manifestations = Crush Syndrome
S/S:
- Myoglobinuria (red urine)
- Hypovolemia S/S
- Electrolyte disturbances
- Acute renal failure: acute tubular necrosis, myoglobin and uriate casts, microthrombi deposit in glomeruli
- Arrhythmia
- Sepsis
- ARDS
- DIC/ massive hemorrhage
- Compartment syndrome
Biochemical disturbances a/w Crush syndrome
- Myoglobinemia
- Hyperkalemia
- Hyperphosphatemia
- Hypocalcemia
- Hyperuricemia
- ↑Creatine Kinase
- ↑Creatinine / Urea
- Acidosis
Crush syndrome
Management
ABCDE resuscitation
Avoid kidney injury:
- Normal saline 1L/hr (10-15mL/kg/hr), avoid all K+ containing solutions
- Forced alkaline diuresis with Sodium bicarbonate and Mannitol
- Aim for urine output 300ml/hr, urine pH > 6.5
- Dialysis
- Call Renal Disaster Relief Task Force
Manage electrolyte disturbance:
- Calcium chloride to counteract hyperK on myocardium
- Manage hyperK: Glucose insulin drip, Beta agonist (ventolin), Sodium bicarbonate
Determine need for field amputation
Causes of ‘rescue death’ (patient collapse after extrication)
Metabolic causes of “Rescue Death”
* Influx of plasma into the muscles
* Efflux of muscle breakdown products (acidosis,
hyperkalemia)
* Influx of calcium
Cause of limb pain and numbness after extrication
Management
Compartment syndrome: Compartment pressure >
Filling pressures of the arterioles of the muscle
6 Ps of compartment syndrome:
* Pain,
* Perishingly cold,
* Paresthesia,
* Paralysis,
* Pallor,
* Pulselessness
Fasciotomy usually if pressure is greater than
40 mmHg
Determinants of field amputation
2 main factors
* Must for urgent life saving
* Salvageability of the trapped limb
Salvageability:
1. Is the vascular injury reparable?
2. Can the skeletal injury be reconstructed?
3. Is the soft tissue viable, or can adequate soft
tissue coverage be achieved?
4. Is innervation present or possible?
