HYPOTHERMIA1 555 Effects of exposure to cold temperatures Impaired co-ordination Central nervous system Behavioral changes Reduced visual acuity Decreased alertness Slowed reflexes More frequent errors Impaired sensory intrepretation Hallucinations Shivering Muscular Increased risk of muscular injury Lowered angina threshold Cardiovascular Hypertension Asthma Respiratory Loss of manual dexterity Peripheral nervous system Reduced skin sensation Diagnosis An approximate indication of likely symptoms and signs as the body temperature fa lls is given in Table 9.1. It may be difficult to achieve an accurate temperature in the pr e-hospital environment and it is essential to stress that the temperature at which any part icular clinical feature is seen will vary dramatically from patient to patient. Therefore: A patient who feels cold should be treated for hypothermia Management The key to good management is effective rewarming with prevention of further hea t loss. - Administer high-flow oxygen during rewarming - Monitor pulse and BP (warming is a ssociated with increasing peripheral blood flow with consequent hypotension if there is trauma) Remove and replace cold wet clothing when safe to do so (in a warm place, out of the wind) Warm the patient (see below); warm drinks (NO ALCOHOL) may be given if the patient is conscious Manage associated injuries \200\224used pre-warmed fluids - Keep the patient flat whenever possible and remove from the cold environment. Handle with care: do not precipitate VF! CHAPTER 9 The hostile environment 556 Table 9.1 The effects of hypothermia Temperature Clinical features 37 Normal oral temperature 36 Respiratory rate and pulse increase 35 Shivering maximal Slow thinking, dysarthria 34 Patient still capable of functioning; blood pressure normal 33 \200\22331 Retrograde amnesia; conscious level clouded; pupils dilated BP difficult to measure; shivering largely stopped 30 \200\22328 Loss of consciousness; bradycardia; bradypnoea; muscular rigidity; VF may supervene seconda ry to stimulation 27 No voluntary motion 26 Consciousness very rare 25 Spontaneous appearance of VF 24 \200\22321 Pulmonary oedema 23 Apnoea 18 Asystole Spontaneous rewarming The surface of the victim \200\231s head and body are insulated (norm ally with a space blanket but polythene sheeting is effective) to prevent further heat loss . The hands and feet are kept cool (hands by the patient \200\231s side) since warm hands a nd feet inhibit heat production. Shelter from the wind is a key component of management. Surface rewarming - Body-to-body rewarming rarely effective and may put both the victim and rescuer at further risk. Hot water immersion at 40*C (elbow hot \200\224only for conscious, shivering, uninjured victims). Once warmed, remove from water, lie down and wrap in blanket s. Skin rubbing is contraindicated and hot water bottles are best avoided. Young fit victims m ay be warmed rapidly. Following admission to hospital, warming can be continued by: HYPOTHERMIA1 557 Central rewarming These procedures can only be carried out after arrival in hospital: - Air way warming - Cardiopulmonary bypass - Haemodialysis - Peritoneal and pleural irrigation wi th warmed fluids Note Elderly patients with hypothermia should be warmed slowly and carefully. A temperature rise of more than about 0.5* per hour runs the risk of cerebral and pulmonary oedema in th ese patients. The most appropriate place for ongoing rewarming is an ITU. Cardiopulmonary resuscitation in hypothermia - Once commenced, CPR should be continued unti l the patient recovers, reaches hospital, and is handed over for continued care or the rescuer becomes ex hausted. Follow the normal cardiorespiratory arrest protocols. - Defibrillation is usually unsuccess ful in the presence of VF if the core temperature is below 30 degrees. Adrenaline and other drugs, including amiodarone, should not be used until the temperature is above 30 degrees. Always check for hypoglycaemia. REMEMBER to rule out other treatable causes of cardiac arrest CHAPTER 9 The hostile environment 558 Cold injury Frost nip Is a minor form of frost bite where the skin becomes white and numb. These changes are completely reversible on rewarming, leaving short- term pain and hyperaem ia. Frost bite - Commonly affects the finger, toes, nose, and ears. - Is worsened on thawing by reperfusion injury and may produce tissue necrosis. Appears white when frozen and becomes blue or purple on thawing and is associated with swelling and severe pain. Causes blistering followed by a thick carapace which blackens and eventually separates (some times after several months) leaving healthy tissue underneath. I n some cases, auto-amputation of digits occurs. Management The key features are: - Protection from the environment if possible - No attempt to rewarm until it can be sustained Active rewarming can be achieved by placing the limb i n circulating water at 40 C. This is extremely painful and requires strong analgesia. This page intentionally left blank CHAPTER 9 The hostile environment 560 Heat-related illness Temperature regulation Heat gain results from basal metabolic activity , muscular exertion, heat absorption, and the breakdown of food. Heat is lost through radia tion, evaporation (of sweat), convection, conduction, and loss of body waste. The hypothala mus (which responds to core temperature receptors) balances heat production and loss to mai ntain a body temperature set within precise limits. When core temperature rises above 40oC, enzyme systems begin to break down. Normally, this temperature range is between 36.3 and 3 7.1oC. In hot weather, there may be a temperature difference of up to 1oC between core and peripheral temperatures. Adaptation to heat Acclimatization to heat is largely complete in 7 \200\22312 days but may continue for several weeks. Sweating leads to loss of water and sodium. Decreased circulat ing blood volume results in decreased renal blood flow. As a result of this (and secondary to increased aldosterone secre- tion), there is reduced secretion of sodium in sweat and ur ine. This results in re-expansion of the extracellular space. Cutaneous blood flow increase s and cardiac output rises to maintain blood pressure despite vasodilatation. Once blood pr essure can no longer be maintained, peripheral vasoconstriction occurs which has the advers e effect of preventing heat loss. Other effects of heat include a lower threshold for sweat ing, anorexia, and loss of interest in activity (both of which result in reduced heat produ ction). Risk factors Increased heat production - Physical activity - Drugs (cocaine, PCP, ecstasy, amphetamines, LSD, tricyclics) - Medical conditions such as hyperthyroidism, acute febrile illness. Reduced heat loss - Inappropriate clothing - Alcohol - Old age - Poor condition - Obesity. Dehydration - Prolonged exertion - Diarrhea and vomiting - Diabetes - Mental impairment - D rugs (diuretics) and alcohol. HEAT-RELATED ILLNESS1 561 Minor heat illness Oedema Oedema of the hands, feet, and ankles occurs in the first few day s of heat exposure. No specific treatment is required, although elevation and compression s tockings are effective. The problem usually resolves spontaneously. Cramp Painful muscular contractions, especially of the thighs, calves, upper arms, and abdo men usually occur when large amounts of sweat have been replaced by large volumes of unsalt ed water. The cramps usually occur during or following exercise. Oral or intravenous admini stration of salt solution (N saline intravenous) is effective. The condition is more common in unacclimatized individuals. Tetany Carpopedal spasm, hyperventilation, and paraesthesiae can be triggered by a change i n air temperature. Removal of the patient to a cooler envi- ronment and conventional treatm ent for hyperventilation (see p.138) are effective. Syncope Heat syncope results from peripheral venous pooling. It is more common in the unacc limatized and those standing stationary for long periods. Spontaneous recovery occurs once the patient is horizontal. Exhaustion Heat exhaustion may be a precursor of sunstroke. By definition, the core (rectal ) temperature is less than 40oC (see heat stroke, p.562 \200\2233). Gross changes in mental and neurological status do not occur. Symptoms include: - Weakness - Tiredness - Dizziness /lightheadedness - Headache - Palpitation Nausea and vomiting - Sweating - Cramps - Flushing - Pilo-erection It may be extremely difficult to distinguish heatstroke and heat exhaus- tion. A diagnosis of heat exhaustion is, therefore, no reason for compla- cency. Heat exhaustion results from the exposure of unacclimatized individuals to a heat load over longer periods (several day s) or following short periods of exertion. The elements of treatment are: - Removal to a co oler place - Cool oral and/or intravenous fluids - Fanning and lukewarm water spraying - Ot her methods of cooling (see heat stroke p.562 \200\2233) - Admission to hospital for observ ation CHAPTER 9 The hostile environment 562 Major heat illness \200\224heat stroke Heat stroke is the severe end of the heat-related il lness spectrum. Its mortality is approximately 10%. Presentation The features of heat strok e are those of heat exhaustion, together with a core temperature greater than 40oC and: - C onfusion - Irritability - Coma, decerebrate posturing (severe cases) - Fitting - Tachycardi a, hypotension, and tachypnoea - Rising core temperature. Inability to measure core tempera ture should not prevent the making of a diagnosis of heat stroke. The presence of sweating does not exclude heat stroke Management The key to management is rapid effective cooling. The victim of heat stroke shou ld, therefore, be managed as follows: - Remove to an area of shade (preferably an air-condi tioned room) - Follow ABC priorities; administer high-flow oxygen - Gain intravenous access and administer crystalloid 1 \200\2232l over the first hour (observe for fluid overload \200\224unlikely in young fit subjects) Undress the casualty - Cool by water spraying and fanning - Ice blocks (wrapped in cloth) m ay be placed in the armpits, groin, and neck Treat fits with intravenous (or rectal) diazepam (see p.322) - Transfer urgently to hospita l Complications of heat stroke Cardiovascular system - Tachycardia - ST changes - Hypotensi on - Myocardial infarction. Respiratory system - Aspiration - Hyperventilation syndrome - A RDS. Central nervous system - Cerebral oedema - Confusion, agitation, delirium - Convulsion s - Coma - Hemiplegia - Ataxia. Neurological abnormalities may persist following recovery. HEAT-RELATED ILLNESS1 563 Hepatic - Hepatic complications are not usually encountered in the pre-hospital setting Delays in diagnosis and treatment of heat stroke contribute to hepatocellular damage which may progress to hepatic failure. Renal - Most commonly seen after exertional heat stroke where dehydration and rhabdomylosis are more common. Prevention and preparedness The pre-hospital practitioner may be asked to advise about prev ention and preparedness. The risks of heat-related problems can be reduced by: - Acclimatiz ation - Maintaining good cardiac fitness - Adequate hydration - Wearing appropriate clothes - Appropriate provision of rest and water breaks - Identifying susceptible individuals \200\224the elderly, small children - Awareness of the heat stroke index (see Table 9.2). Table 9.2 Heat stroke index Ambient temperature (oC) Restriction on activity <24*C Activities may proceed but remain vigilant for early signs of heat illness 24.0 \200\22325.9*C Rest periods needed 26 \200\22329*C No activity for unacclimatized or at-risk individuals; others need to be carefully monitore d >29*C No unnecessary activities should take place CHAPTER 9 The hostile environment 564 Near drowning It is estimated there are over 500 deaths per annum from drowning in the UK a nd up to 8 \200\22310 times more near drownings, especially in children aged 1 \200\22314, adult non-swimmers, and patients with significant co-morbidity. Factors influencing near dr owning include: - Unconsciousness - Ability to swim - Exhaustion - Hypothermia Unconsciousness may be due to head injury with loss of consciousness (for example, diving i nto shallow water) or secondary to medical illness (for example, hypoglycaemia, epilepsy, C VA), alcohol, and drugs. Drowning usually follows a characteristic sequence in which the victim: Thrashes about in the water - Inspires under water - Ingests water - Suffers small-volume a spiration and intense bronchospasm Further attempts to inspire lead to further inhalation/ingestion, uncon- sciousness, and death. Exhaustion is commonly associated with long periods of time in the water or occurs acutely in cold water submersion due to onset of hypothermia. So called \200\230dry drowning \200 \231, in which no water is found in the lungs, is believed to be a reflex vagal response to sudden immersion. It is critical to appreciate the hydrostatic pressure effect on the body whilst submerged in water which serves to support the circulation. Hypothermia is common and when the core temperature falls below 35o the victim becomes conf used, unco-ordinated, ataxic, and may drown. In children, cold water immersion may provide cerebral protection. There is no significant difference in the pattern of events that occur s between salt water drowning and fresh water drowning and the princi- ples of treatment ar e the same for both. Assessment The assessment priorities are: - Is the scene safe? Are you safe? Don \200\231t become a victim! - Is the patient breathing? Is the depth of breathing adequate? Three clinical scenarios result (see below): 1. The patient is conscious and breathing 2. T he patient is unconscious, is not breathing, but has a pulse 3. Patient is in full cardiore spiratory arrest NEAR DROWNING1 565 Management General Successful treatment and outcome depends on minimizing the \200\230hypo xic gap \200\231 \200\224the time between submersion and relief of airway obstruction. - Th e patient should be removed from the water in a horizontal position to avoid catastrophic hypotension and cardiac arrest. Vomiting on recovery from near drowning is common and the rescuer should be prepared to tur n the patient or use suction as appropriate. No attempt should be made to remove water from the lungs other than simple postural drainage of the airway. The Victim MUST ALWAYS be removed from the water in a horizontal position Specific scenarios The patient is conscious and breathing - Clear the airway if necessary - Administer high-flow oxygen (10 \200\22315l/min) using a non-rebreathe mask and a reservoir bag If breathing is inadequate, consider bag-valve-mask assisted ventilation - Maintain the pat ient in a horizontal position - Consider siting an IVI and give 10ml per kg of isotonic cry stalloid depending on the cardiovascular status Transportation all victims of near drowning to hospital even if they have apparently recovered*. The patient is unconscious, not breathing, but has a pulse - Open the airway as a matter or urgency. Most patients have airway obstruction due to water, foreign body, or vomit. Consider the possibility of cervical spine injury depending on the mechanism of injury (for example, diving into shallow water). Maintain inline stabilization if required. In adults, consider a finger sweep to remove debris. In children, clear the airway if neces sary by postural positioning (recovery position) or by elevating the feet and pelvis to all ow drainage by gravity. When the airway is open, administer high-flow oxygen at 10 \200\22315l/min using an non-rebreath mask with a reservoir bag. Consider bag-valve-mask assisted ventilation. - Consider intubation. - Most patients will v omit on recovery \200\224suction should be available. - Consider cannulation and IV isotoni c fluids 10ml per kg. - Most near drowning victims are hypothermic; protect from further heat loss. Steroids and early antibiotics provide no evidence-based clinical benefit. Secondary drowning, typified by delayed tachycardia, delayed tachypnoea, cough and frothy s putum, and a risk of developing ARDS occurs in 2 \200\2233% of patients in this clinical ca tegory. CHAPTER 9 The hostile environment 566 The patient is in cardiorespiratory arrest The position may still be retrievable. Important factors influencing outcome include: - Time spent submerged - Temperature of the water - P resenting ECG rhythm Acute submersion in cold water offers cerebral protection. A two- year-old child has surviv ed 66 minutes \200\231 submersion in cold water and made a full recovery. CPR should follow conventional algorithms. Once started, it should be continued at least un til arrival in hospital. Therapeutic and electrical defibrillation is reported to be ineffe ctive in the presence of significant hypothermia. Intravenous access should be obtained and volume resusci- tation commenced with warmed isotonic fluid. Scrupulous airway management is essential: Open the airway as a matter or urgency. Most patients have airway obstruction due to water, foreign body, or vomit. Consider the possibility of cervical spine injury depending on the mechanism of injury (for example, diving into shallow water). Maintain inline stabilization if required. In adults, consider a finger sweep to remove debris. In children, clear the airway, if nece ssary by postural positioning (recovery position) or by elevating the feet and pelvis to al low drainage by gravity. Perform bag-valve-mask assisted ventilation with high-flow oxygen. - Consider intubation. Prognosis Prognosis is excellent in those victims who have not suffered cardio- respiratory arrest. Full recovery, usually without neurological conse- quences, commonly follows resus citation of patients who have been unconscious but maintained a pulse. Following cardioresp iratory arrest, the prognosis is not hopeless and full recovery has been recorded, espe- ci ally in children following cold water submersion. NEAR DROWNING1 567 Cardiac arrest Precordial thump if appropriate BLS algorithm if appropriate Attach Defibrillator/Monitor Assess rhythm Check pulse VF/VT Non-VF/VT During CPR Correct reversible causes If not already: - check electrodes, paddle position, and contact - attempt/verify: airway & O2 IV access - give epinephrine every 3 min. - Consider: amiodarone, atropine/pacing Buffe rs Defibrillate x3 as necessary CPR 3 min* * 1 min if immediately after defibrillation CPR 1 min Potential reversible causes: - Hypoxia - Hypovolaemia - Hyper/hypokalaemia & metabolicdisor ders - Hypothermia - Tension pneumothorax - Tamponade - Toxic/therapeutic disorders - Throm bo-embolic & mechanical obstruction. Fig. 9.1 Cardiac arrest algorithm. Reprinted with permission from Ramrakha P and Moore K (2 004). Oxford Handbook of Acute Medicine, 2nd edn. Oxford University Press, Oxford. CHAPTER 9 The hostile environment 568 Diving emergencies Pathophysiology Atmospheric air consists of oxygen (21%), nitrogen (79%) , and carbon dioxide (0.03%). Each exerts a partial pressure in proportion to their percent age concentration. At sea level, this equates to a pressure of 1 atmosphere (KPa). Water is more dense than air. Therefore at a depth of 10m, a diver is subjected to a greater pressu re of 2 atmospheres. Boyle \200\231s law states that volume (V) is inversely proportional t o pressure(P): V \210\236 1/P Therefore the volume of a gas will decrease with increasing depth and increase on returning to the surface. In practical terms, at a depth of 10m, the volume of air in the lungs has reduced by a half from that at the surface. Conversely, a diver breathing from a compressed air cylinder will need to exhale during ascent as the volume of air in the lungs doubles i n the ascent from 10m depth to the surface. In addition, because the diver is breathing air at a higher pressure, as per Henry \200\231 s law, the amount of nitrogen dissolved in blood and tissues increases as the pressure incr eases. As the diver ascends, the nitrogen will come out of solution as the pressure decreas es. The changes that occur are summarized in the box, where it can be seen that the greates t changes occur in the first 10m of descent: Surface 4 litres 10 meters 2 litres 20 meters 1 1/3 litres 30 meters 1 liter Diving-related illness: barotrauma Trauma related to pressure can occur on ascent and desce nt and commonly affects air-filled cavities (for example, the lungs, the gut, the middle ea r, facial sinuses, and tooth sockets). Descent - Most problems occur near to the surface where the greatest pressure changes occur Particularly affects the middle ear, where symptoms of pain can be relieved by swallowing or a valsalva maneuver May result in tympanic membrane perforation if the diver \200\231s eustachian tubes are blocked. Ascent - A slow ascent whilst slowly exhaling is essential - Rapid ascent risks ear perfora tion, and pulmonary complications (including frothy sputum, cough and pneumothorax, and air embolism, which includes cerebral air embolism resulting in CVA and coronary air embolism which may produce electromechanica l dissociation and death). DIVING EMERGENCIES1 569 Diving-related illness: acute decompression illness (ADI) ADI has previously been divided i nto: - mild (cutaneous and limb bends) - serious (neurological cardiac, respiratory, neurol ogical and gastrointestinal). Terms such as the bends, hits, and staggers reflect the layman \200 \231s description of clinical scenarios. On the basis that minor presentations may be follo wed by more significant problems, all patients with ADI should be referred to a hyperbaric facility. Symptoms commonly present early after ascent: 50% within 10 minutes - 85% within 1 hour - A small number present up to 36 hours after asc ent Predisposing factors include: - Poor physical fitness - Low water temperature - Increased p hysical exertion - Obesity - Increasing age Injuries - Dive profile - Recurrent dives - Dehydration - Alcohol. Pathophysiology Increased nitrogen is dissolved into blood on descent (Henry \200\231s Law) and is variably absorbed depending on blood flow and tissue composition. ADI results from a sudden release of nitrogen when the pressure is reduced on rapid ascent. If the ascent is slow, there is sufficient time for the nitrogen to be excreted by the lungs. Nitrogen excretion continues for hours after a dive. A reduction in atmospheric pressure su ch as, for example, during flying, may precipitate ADI. Nitrogen bubbles do not form on the arterial side of the circulation as this blood has just passed through the lungs where pre ssure equilibri- lation has occurred. Following a rapid, uncontrolled ascent, nitrogen bubbles develop in the venous system. Pass age into the arterial circulation is believed to be via a left-to-right shunt through a pat ent foramen ovale or, more commonly, an A \200\223V shunt in the lung vasculature. The bubble is eventually resorbed but may produce an acute comple- ment activation, inflamm atory response, and tissue damage. Hyperbaric oxygen therapy results in more oxygen in solu tion which will reach hypoxic areas by diffusion through the tissues. During repressurizati on in a hyperbaric chamber, the bubble reduces in size. The chokes Nitrogen bubbles forming in the pulmonary capillary bed produce decreased perfus ion and pulmonary oedema. This can progress to ARDS. The staggers Nitrogen bubbles in the spinal vasculature result in neurological signs and ma y cause permanent disability (spinal bends). The creeps Blockage of capillaries in the skin results in an itchy sensation. CHAPTER 9 The hostile environment 570 Clinical features of acute decompression illness Generalized - General lethargy, weakness - Apathy Cerebral - Multi-focal vascular lesions - Presentations may be similar to CVA (e.g. loss of motor function, sensation) May present with headaches and confusion Cerebellar - Unsteadiness - Loss of co-ordination - Dysarthria and/or nystagmus Spinal - Tingling - Numbness - Occasionally paralysis - Spinal pain - Girdle pain Musculoskeletal - May be single joint - Often a numb feeling progressing to constant pain The ear - Vertigo - Hearing deficit Peripheral nerves - Numbness - Tingling - Occasional motor weakness Skin - Pruritis - Rash DIVING EMERGENCIES1 571 Management - ABCDE approach High concentration oxygen via mask with a non-rebreathe valve and reservoir bag to relieve hypoxia and enhance nitrogen offloading Use water for ET tube cuff if intubation necessary - Consider possibility of pneumothorax i f ventilation becomes difficult or signs suggest the diagnosis Consider intravenous crystalloid Analgesia is contraindicated as it will mask developing physical signs - Nitrous oxide is a bsolutely contraindicated because of its rapid diffusion potential, therefore increasing the size of nitrogen bubbles Benzodiazepine iv for fits - Transfer to suitable hyperbaric unit - Most divers have a \200\230buddy \200\231 \200\224check the buddy for symptoms of ADI. ADI is unlikely to be seen in an isolated organ and should always be regarded as a multi-sy stem problem CHAPTER 9 The hostile environment 572 Electrocution injury Types of incident Industrial/occupational Often affecting workers on p ower lines and those in industry using electrical tools and machinery. Domestic Due to failure to earth appliances or using electrical equipment near water. 20% of electrocutions occur in children \200\224commonly toddlers playing with electrical appliances and adolescents during acts of bravado. Lightening - 75 \200\22385% occur in men - 30% involve people working out of doors - 25% in volve recreational activities Railroad incidents Electrical injuries involving railways are relatively common and many ar e suicide attempts. The common electrical systems in the UK are: - 25,000 volt overhead AC lines - 750 volt DC third rail system - 630 volt DC fourth rail system (used by the London Underground) Always ensure the electrical system is turned off. Be aware that over- head lines are often disabled by bird strikes and routinely turned back on after 20 minutes. Electrophysiology An electric current is a motion of electrical charge where the electrical driving force is known as the voltage and the magnitude of electric current is measured in amperes. Current flow is dependent on the voltage and the resistance of the tissues (for example, th e skin, nerve, and muscle) through which it is passing and is governed by Ohm \200\231s law where: V(voltage) I (current) = R(resistance) Current flows preferentially through tissues of least resistance (for example, nerve tissue ) and this, therefore, significantly influences the patterns of injury seen. Skin resistanc e depends on the skin \200\231s thickness and its moisture, which is why hands are commonly affected. The amount of damaging themal energy depends on: - The resistance of the tissue - The duration of contact - The square of the current Current, therefore, is the most criti cal factor. ELECTROCUTION INJURY1 573 Direct current (DC) implies unidirectional current flow (for example, a battery) whereas an alternating current (AC) refers to a changing flow. The latter forms the basis of the UK d omestic supply (240V AC current). Alternating current is much more damaging and, on contact , may produce tetanic skeletal muscle contractions preventing release of any electrical wir es. Direct current may produce a violent contraction but tends to throw the victim away fro m the source. Lightening Lightening strike may produce 20 \200\223200 million volts with a current of 50, 000 amps. However, its duration is usually less than 0.2 seconds. The current pathway defin es the injury pattern and, in the case of lightening strikes, the duration is insufficient to break the skin and reaches the earth by a \200\230flashover \200\231 effect, risking ca rdiac arrest. The flashover phenomenon may result in widespread skin burns. In other patien ts, respiratory arrest is common. Usually, those who do not suffer a cardiac arrest have an excellent prognosis. Patterns of injury Skin Electrothermal burns result from current flow through the skin gene rat- ing heat. Electrical burns commonly have points of entry and exit. AC burns tend to be associated with more tissue damage than DC burns. Nervous system Damage to the nervous system occurs in 70% of all electrical shock victims. This is because of the conduction potential of nervous tissue. Transient unconsciousness ma y result. Persistent alteration in conscious level suggests cerebral injury. Similarly, in very severe injury, the spinal cord and peripheral nerves may be damaged with paralysis. Cardiorespiratory Cardiac arrest is the principle cause of death following electrical injur y. AC currents tend to produce VF and DC high voltage is associated with asystole. Other ma nifestations include cardiac dysrhythmias including sinus tachycardia, atrial fibrillation, ventricular ectopics, and complete heart block. Respiratory arrest may occur due to a paralyzing effect following pro- longed tetanic muscl e contractions, therefore risking secondary hypoxic arrest. Cardiac output frequently retur ns spontaneously but respiratory arrest may persist. Early basic life support is frequently life-saving. Vascular May follow deep cutaneous burns, usually with high voltages (1000V). Limbs and joints Thermoelectric injury to muscle may produce muscle necrosis, compart- ment syndrome, rhabdomyolysis leading to renal failure, hyperkalaemia, and the risk of cardiac arrest. CHAPTER 9 The hostile environment 574 Management - Ensure that the current is switched off - Do not approach until it is safe to do so - A non-conductor such as a wooden pole can be used to move the victim or the electrical source In case of electric pylons, be wary of electrical reconnection \200\224unless informed, the electricity board will reconnect the supply after 20 minutes presuming it to be a bird strike Assess cardiorespiratory status and commence BLS if indicated - Excellent recovery has been documented from resuscitation of seemingly dead victims - Initiate ALS if indicated - Consider cannulation and fluid replace ment \200\224major electrical burns require aggressive volume resuscitation. Lightening str ike victims usually have limited burns and do not require fluid resuscitation. In lightening strike, seek cover as soon as practical/possible Consider the risk of seconda ry traumatic injury if the patient has been thrown to the ground at the time of electrocuti on. Chapter 10 575 Major incident management and triage Major incident management 576 The phases of a major incident 578 The scene of a major incid ent 584 Radio voice procedure 596 Sources of further information 600 Triage 602 Triage siev e 604 The triage sort 606 Triage in children 608 Triage labeling 612 Trauma scoring 614 CHAPTER 10 Major incident management and triage 576 Major incident management Definitions In health service terms, a major incident is defined as: \200\230Any incident where the location, number, severity or type of live casualties r equires extraordinary resources \200\231. Major incidents may be classified in three ways - Natural or manmade - Simple or compound - Compensated or uncompensated. The distinction between natural disasters (Tsunami, earthqua ke, flood, or forest fire) and manmade is self-explanatory. The most common causes of manma de disaster are industrial incidents, mass gathering incidents (such as football stadium di sasters), transportation incidents, and terrorism. Simple and compound incidents In a simple incident, the location \200\231s infrastructure r emains intact and effec- tive: communications are possible and the sick can be treated. Whe n an incident is compound, roads, electricity supply, railways, health services, and commun ications are disrupted. Compensated and uncompensated A compensated incident is one which can be dealed with by mob ilizing extra resources (for example, a major fire in a hotel or cinema). An uncompensated incident cannot be managed even when all available resources have been mobilized. Typical e xamples include natural disasters such as earthquakes and hurricanes. Disasters and catastrophes The terms \200\230disaster \200\231 and \200\230catastrophe \200\231 are usually used to refer to uncompensated major incidents (generally natural disa sters). MAJOR INCIDENT MANAGEMENT1 577 Table 10.1 Major incidents Date Place Incident Dead Injured Natural incidents 1931 China, Huang He River Flood 3.7 million Not known 1970 Peru, Yungay Landslide 17,500 Not known 1995 Japan, Kobe Earthquake 5502 Not known 2004 Pacific rim Tsunami >250,000 Not known 2005 Pakistan Earthquake 200,000 Not known Manmade incidents 1977 Tenerife Air crash 583 Not known 1985 UK, Bradford Stadium fire 55 200 1985 Belgium, Brussels Crowd crush 41 437 1987 Belgium, Zeebrugge Ferry capsize 137 402 1988 UK, Lockerbie Air crash 270 \200\223 1989 UK, Sheffield Crowd crush 96 200 1995 Japan, Tokyo Gas attack 12 5000 1998 Omagh Car bomb 29 200 2005 London Bombs 52 700 CHAPTER 10 Major incident management and triage 578 The phases of a major incident A major incident has three phases: - Preparation - Response - Recovery. Preparation The three components of preparation are: - Planning - Equipment - Training. Major incident planning Any site where there is a risk of a major incident (for example, ch emical plant, major sporting venue, or travel interchange) must have a major incident plan which is regularly updated and regularly practiced. Any agency which will have to respond to a major incident must have a service plan (once ag ain, regularly updated and practiced) which can be adapted for an individual incident wheth er it occurs at a high risk site (such as a chemical plant fire) or is random and unpredict able (for example, an intercity train crash). All hospitals must have a major incident plan and any health care pro- fessional who will b e called upon to respond must know his own role and how that role integrates into the overa ll response. All major incident plans must be multi-agency, reflecting the skills and responsibilities o f all those bodies which will be involved if an incident does happen. In order to facilitat e this, many agencies (and all official bodies) now use MIMMS \200\224Major Incident Medica l Management and Support as their template for a major incident response. Equipment Adequate equipment must be available and easily accessible. This will include per sonal protective equipment, medical equipment, communica- tions, and specialist equipment s uch as triage cards and major incident commanders \200\231 bags. MIMMS \200\224Major Incident Medical Management and Support The co-ordinated response to a medical incident is taught on the MIMMS course. This is a three-day course for health care professionals which covers the organization of the response to a major incident, communica- tions, equipment, and triage. Members of the other emergency services and the armed forces also attend. The course concludes with formal major incident exercises at chosen locations such as sports grounds or industrial sites. The MIMMS course is now accepted international ly. A one-day course is also available for those who may have to respond to an incident but who will not be called upon to assume a command role. (For details, see useful contact details p.600.) THE PHASES OF A MAJOR INCIDENT1 579 Successful completion of a MIMMS course should be considered essential for anyone who is li kely to have to respond to a major incident. Posses- sion of \200\230Major incident manage ment system \200\231 (Hodgetts and Porter, BMJ Books, 2nd edn., 2002) is recommended. Major incident management System is distributed to all MIMMS course candidates. Major incident response The response to a major incident is considered under the following headings: - Command - Safety - Communications - Assessment - Triage - Treatment - Transport ation Command Command is a vertical process; control a horizontal one: C CONTROL M M A N D Each emergency service will have a commander at the scene Control is enforced by means of c ordons (see p.584). Safety Safety of responders and victims alike is a key component of the major incident resp onse. The \200\2301 \200\2232 \200\2233 of safety \200\231 is: 1. SELF 2. SCENE 3. SURVIVO RS Command - Safety - Communications - Assessment - Triage - Treatment - Transportation Control Spells Calm And Time To Treat CHAPTER 10 Major incident management and triage 580 Communications Effective communications must be established between incident com- manders. Regular face-to-face communication is essential. Other methods include: - Radios - Runners - Whistles - Hand signals - Telephones (land lines) - Mobile phones. Health service communi cations are an ambulance service responsibility. Communications will be established from th e site to ambulance control. Radios Ambulance radio systems are usually VHF, allowing communication at the scene and wit h ambulance control. A radio net will be established with control and call signs. Single fr equency simplex allows all users to hear all messages (it is \200\230open \200\231) and of fers a broader \200\230picture \200\231 of the incident as it progresses. Two frequency si mplex means that call signs can only speak to and hear control. Control can hear all statio ns and can let stations hear each other ( \200\230talk through \200\231). Two frequency sim plex is the usual ambulance service system. A protected national frequency for doctors at major incidents is currently being trialed. Runners Runners are an effective method of communication, but ideally should carry written rather than verbal messages. They should be instructed to return in order to confirm that a message has been conveyed irrespec- tive of whether there is a reply. Whistles Repeated whistle blasts by the fire service indicate an immediate need to evacuate an area. Hand signals The military use a range of hand signals. These should not be used by civilian s unless they are thoroughly familiar with their use and meaning. Telephones (land lines) In prolonged incidents, it is possible to set up land lines at the scene of an incident. These can be provided by commercial companies or by the military. Mobile phones Mobile phones are an effective means of communication, but have two major pro blems. There is no central co-ordination of calls, so that confusion and duplication and ov erload of the system can occur with the result that no calls can be made. The latter is a p articular problem once the media have been notified. THE PHASES OF A MAJOR INCIDENT1 581 In order to prevent system overload and allow continued access to essential users, the ACCO LC (Access Overload Control) system can be activated. Once ACCOLC has been activated, only mobile phones which have been modified will remain in use. Requests for phones to be ACCOLC modified have to be approved at Cabinet Office level. Assessment Assessment of the number, severity, and types of injury is a key compo- nent of the major incident response. Triage Triage is the prioritizing of patients for treatment or transportation according to their severity of injury (p.602).