CHAPTER 6 Poisoning and substance abuse 398 Approach to the poisoned patient In many cases, the toxic agent will not be known and when it is, options for specific treatment are usually limited. Only a very few antidotes are av ailable for pre-hospital use (see pp.406 \200\2237). As a consequence, a generic approach t o the poisoned patient is essential. This will follow the ABCDE sequence: - Airway (with C spine control if there is any possibility of significant trauma) Breathing \200\224with high-flow oxygenation - Circulation Establish intravenous access - Monitor pulse, BP, SaO2, and ECG Disability \200\224establish and record the conscious level using AVPU and DON \200\231T FORGET TO CHECK THE PUPILS! Exposure \200\224as required to exclude other significant injury Airway A patent airway should be established and maintained at all tines. The technique use d will vary according to the patient \200\231s level of consciousness. If the conscious lev el is reduced, an oral or nasopharyngeal airway can be inserted. Intubation may be necessar y. Many patients will also have taken alcohol and will, therefore, be prone to vomit. Appro priate use should be made of the recovery position and working suction MUST be available. Breathing High-flow oxygen should be administered and respiration supported as required. Circulation Intravenous access should be obtained in all but the most trivial of poi- sonin gs. This must not delay transfer of the critical patient. Inadequate circulation may result from a wide range of mechanisms. Wherever possible, arrythmias should be treated in hospit al and rapid evacuation is essential. The arrythmias associated with tricyclic antidepressa nts respond to alkalinization with sodium bicarbonate. If there is no sign of arrythmia or heart failure, judicious administration of intravenous fluids can be used to raise the bloo d pressure. Pulse oximetry, ECG monitor- ing, and blood pressure monitoring should be routi ne. Disability Check AVPU (p.187) and pupils. Assessment of the pupils may provide vital information. Pin point pupils are characteristic of opiate poisoning but also occur in organo- phosphate poisoning (the context may aid in diagnosis). Dilated pupils occur in the anticholinergic syndrome a ssociated with overdose of atro- pine, tricyclic antidepressants and other agents. Assessme nt of the AVPU response will determine the depth of reduction of conscious level. APPROACH TO THE POISONED PATIENT1 399 Dilated pupils - Atropine - Tricyclic antidepressants - Phenothiazines. Constricted pupils - Opiates - Organophosphates. Exposure Exclude or identify injuries due to the overdose or alcohol. Complete exposure of the patient should be avoided in the pre- hospital environment and an exhaustive (and probably fruitless) search for clues should not delay transfer to hospital as long as appropriate attention has been paid to airway and breathing. Nevertheless, some clues such as needle marks from intravenous injection, sores around the mouth (from inhalat ion of chemicals) or burns from caustic substances may be identified. Further information In most cases, time need not be wasted seeking specialist advice. This can be done after arrival in hospital. If transfer is likely to be prolonged or delayed, or the poisoning appears trivial, advice can be sought from the UK National Poisons Advice Ce nter (see box). DON \200\231T EVER FORGET GLUCOSE UK National Poisons Advice Center 0870 600 6266 They will direct the call to the relevant l ocal center CHAPTER 6 Poisoning and substance abuse 400 Differential diagnosis of the poisoned patient In many cases, it will be obvious that a pat ient has been poisoned, and questioning the patient or witnesses, or scene assessment will rapidly confirm this. However, patients with serious suicidal intentions may go to consider able lengths to hide what they have done, or if the patient is unconscious, the clues may b e more subtle. A high index of suspicion is therefore essential. In addition, in some cases , the poison may be unknown or more than one substance may be involved. Mixed overdoses are far from uncommon, and industrial poisonings more often than not involve multiple chemical s which may further react with each other to complicate the clinical picture. Poisoning should be suspected if: The patient \200\231s conscious level is altered - Symptoms occur in an unusual age group - The context suggests prevalence of drug abuse - Bizarre symptom complexes or signs are pre sent - There is obvious reluctance to provide information. Because the symptoms and signs o f poisoning are so varied, and in the majority of cases non-specific, it is equally importa nt not to jump to the conclusion that a patient has been poisoned and to exclude other pote ntially treatable causes. Diagnoses which should be excluded include: Metabolic - Hypoxia - Hypoglycaemia - Electrolyte abnormality. Traumatic - Head injury - Hy potension due to hemorrhage. Neurological - Stroke - Subarachnoid hemorrhage - Post-ictal s tate. DIFFERENTIAL DIAGNOSIS OF THE POISONED PATIENT1 401 CHECK FOR - Pill bottles and medicine containers (take them to hospital) - Signs of alcohol consumption - Medic-Alert bracelet - Injection marks - Paraphernalia of drug abuse - Sig ns of previous self harm - Suicide note (rare). CHAPTER 6 Poisoning and substance abuse 402 Symptom complexes in poisoning There are a number of symptoms or groups of symptoms which t ogether provide useful clues to the likely causative agent. A list of drugs and common recognizable presentations is given below and in Table 6.1: Coma with stable vital signs - Benzodiazepines Hyperthermia - Anticholinergics - Neuroleptics (major tranquilizers/antipsychotics) - Sympa thomimetics - Phencyclidine and hallucinogens - Aspirin. Hypothermia - Sedatives, opiates, alcohol (reduce CNS activity) - Insulin and oral hypoglyc aemics. Hypotension with normal mental state - Calcium channel blockers. Tachypnoea - CNS stimulants - Aspirin - B agonists - Agents causing pulmonary oedema \200 \224including organophosphates, chlorine Agents causing hypoxia \200\224including cyanide, carbon monoxide - Agents causing metaboli c acidosis \200\224including methanol, ethylene glycol. Dilated pupils - Tricyclic antidepressants - Amphetamines (see p.463) - Phenothiazines. Constricted pupils - Opiates - Organophosphates. In many cases it will not be possible to i dentify the agent precisely, so: TREAT THE PATIENT, NOT THE DRUG Table 6.1 Common recognizable presentations Syndrome Causes Symptoms Signs Comments Opioid Opiates Confusion Reduced conscious level Pinpoint pupils Respiratory depression Hypotension Responds to naloxone Cholinergic Organophosphates Sweating, salivation, blurred vision, vomiting, wheeze, diarrhea, muscle cramp Tachycardia, hypo/hypertension, fasciculation, paralysis, respiratory failure, ataxia, fits , coma S Y M P T O M C O M P L E X E S Anticholinergic Atropine Tricyclic antidepressants Phenothiazines Lethargy, confusion, hallucinations, fits, blurred vision, urinary retention, dry mouth, fl ushing Ataxia, cardiac failure, respiratory failure, dry skin, dilated pupils, abdominal distensio n Sympathomimetic Aminophylline Cocaine Amphetamine, Caffeine Phencyclidine Excitation Fits Tachycardia Hypertension I N P O I S O N N G Diazepam Temazepam Coma Vital signs normally stable Hypotension and respiratory depression can occur Benzo diazepine I 1 4 0 3 CHAPTER 6 Poisoning and substance abuse 404 Decontamination Decontamination is only very rarely necessary in the pre-hospital environme nt but the following steps should always be followed: - Remove the patient from the contami nated area (or seek fire brigade assistance) Remove contaminated clothing - Use copious lavage to remove skin or eye contamination - Kee p the patient warm - Provide necessary resuscitation - DO NOT DELAY removal to hospital. Ga stric lavage should never be attempted pre-hospital. Similarly, there is no role for routin e use of emetics (ipecacuanha) either in children or adults. Where there is concern because of very prolonged transfer times or unavoidable delays, advice should be sought on a case- specific basis from the nearest poisons unit, A&E or receiving department. Activated charcoal (50g in an adult po) is appropriate in some over- doses or poisonings, a s indicated in the text. It is recognized, however, that many immediate care practitioners will not carry activated charcoal and that many patients will not tolerate drinking it. Nee dless to say, charcoal can only be given if the patient is able to protect their own airway . This page intentionally left blank CHAPTER 6 Poisoning and substance abuse 406 Antidotes The majority of specific antidotes are only available in hospital and, in some ca ses, from specialist centers. There are, however, a number which have a valuable pre-hospit al role. Flumazenil Flumazenil is a highly effective competitive antagonist to benzodiazepines. Howe ver, its use has been associated with serious complications includ- ing fits in those who h ave also taken drugs which cause fits (in whom the benzodiazepine is controlling epileptic activity). Flumazenil may also precipitate acute withdrawal in chronic benzodiazepine users . It cannot therefore be recommended for pre-hospital use. If respiratory depres- sion occu rs as a result of benzodiazepine overdose, the airway should be protected and ventilation s upported (with monitoring) and the patient transferred rapidly to hospital. Glucagon Glucagon is used in beta blocker overdose for those patients who do not respond to atropine. The initial dose is up to 5mg iv followed, if neces- sary, by an intravenous inf usion in hospital. It also has a role in insulin overdose. Calcium Calcium chloride (or gluconate) is used in the management of calcium channel blocke r overdose. Dextrose 10% dextrose is used in the management of hypoglycaemia in adults and children. Naloxone Naloxone (Narcan ) is a highly effective pure opiate antagonist. The initial dos e is 400 \200\223800mcg iv in adults (10mcg/kg in children). Considera- bly higher doses ma y be needed and can be given safely. If naloxone is being given to exclude opiate overdose as a cause of loss of conscious- ness, a dose of 2mg should be given. Failure to respond to this dose effectively excludes opiate overdose. If abruptly reversed, many intravenous drug abusers will become ver- bally (and physically) aggressive and leave the scene. Since naloxone has a shorter half life than many opiates, recurrence of symptoms may then occur unwitnessed. As a consequence, opiate-induced coma is best not reversed unless there is significant respiratory compromise. Even then, an altern ative is to support respiration until arrival in hospital. Administra- tion of a similar do se of naloxone (400 \200\223800mcg) intramuscularly may reduce the chances of further probl ems if non-cooperation seems likely, since it has a significantly slower onset. Atropine Atropine is used in the management of organophosphate poisoning and drug-related s ymptomatic bradycardia. ANTIDOTES1 407 Sodium bicarbonate Sodium bicarbonate is the antidote for tricyclic antidepressant (TCA) ov erdose and is effective against TCA-induced arrhythmias. Most pre-hospital care personnel d o not carry it, however, and critical patients are probably best transferred, as rapidly as possible, to hospital for further assessment and management. Table 6.2 Commonly available antidotes Poison Antidote Flumazenil (Anexate Initial adult dose Benzodiazepines ) NOT RECOMMENDED Beta blockers Glucagon 2 \200\2235mg Calcium channel blockers Calcium, glucagon 10ml 10ml Dextrose 50ml 50% Insulin/oral hypoglycaemics Naloxone (Narcan Opiates ) 400 \200\223800mcg Organophosphates Atropine 2mg Tricyclic antidepressants Sodium bicarbonate 1 \200\2233mmol/kg CHAPTER 6 Poisoning and substance abuse 408 Poisons Angiotensin converting enzyme (ACE) inhibitors Examples Captopril, cilazapril, enal april, fosinopril, imidapril, lisinopril, perindopril, ramipril. Clinical features - Drowsiness - Hypotension - Tachycardia. Management - Pre-hospital treatment is not usually required - Cautious fluid administration should be considered if the patient is hypotensive Activated charcoal 50g (if available) - Transfer to A&E. POISONS1 409 Adder bite (see also snake bite) The adder (Vipera berus) is the only native poisonous snak e in the UK. General features Adder bites are usually a feature of the summer since the adder hiber- nat es during the winter. Only about 50% of bites are associated with envenomation (painful swe lling at the bite is indicative of venom injec- tion, but systemic envenomation may occur w ithout it). Two puncture marks about one centimeter apart are usually found on the distal p art of a limb. There is usually immediate pain. Clinical features Local - Painful local swelling (within one hour) with bruising - Regional (tender) lymphadenopathy. Systemic (may occur without local signs) - Vomiting, abdominal pain, and diarrhea (may be o f very rapid onset) - Hypotension - Loss of consciousness - Oedema of the trunk face and li ps - Non-specific ECG changes may occur in severe poisonings. Management - Reassurance - Clean the area of the bite and apply a sterile dressing - If the hospital is more than 30 minutes away, place a bandage around the limb proximal to the bit e, tight enough to impede venous return but not tight enough to obstruct arterial flow. Where possible, avoid use of the bitten limb - Keep the bitten limb dependent - Warn the ho spital about the patient - If the snake is dead, take it to hospital with the patient - DO NOT waste time ( and risk being bitten) trying to capture the snake DO NOT incise or suck the wound. CHAPTER 6 Poisoning and substance abuse 410 Alcohol (see ethanol or methanol) Antibiotics General features Deliberate overdoses of anti biotics are rare, presumably because they are known to be relatively safe. Clinical features There are usually no ill effects. Nausea, vomiting, and diarrhea may occu r. Management - No pre-hospital treatment is required - Transfer to hospital is appropriate fo r symptomatic management and psychiatric assessment. POISONS1 411 Anticholinergic drugs and agents Examples - Atropine (and related drugs) - Antihistamines - Antipsychotics - Tricyclic antidepressants - Anti-Parkinsonian medications - Plants. Clinical features - Hallucinations - Confusion - Lethargy, coma - Fits - Cardiac and respir atory failure - Ataxia Dry skin and mouth - Dilated pupils, blurred vision - Tachycardia - Flushing - Urinary rete ntion. Management - Cardiac monitoring - Fits are usually transient and may be prevented by avoida nce of stimulation. They may also, however, suggest progression to cardiac arrest. Immediate treat ment is not usually necessary but, if required, the drug of choice is diazemuls. Sinus tachycardia - Dysrhythmias should not be treated unless VT is present and the hospita l transfer time prolonged, in which case lignocaine should be used. Urgent transfer to hospital is essential. CHAPTER 6 Poisoning and substance abuse 412 Anticoagulants Examples - Warfarin (acenocoumarol, phenindione). Warfarin and related compo unds (super warfarins) are the active ingredients in a range of proprietary rodent killers, although consumption of sufficient to cause serious symptoms is rare. Clinical features - Spontaneous bleeding Nose, gums, GI tract, and urinary - Haemoptysis - Skin (rare) - Brain (rare). The duration of onset of bleeding is sufficiently long that symptomatic presentations are very rare. Mos t patients present before symptoms develop. Management The management will depend on whether the patient is on long-term anticoagulatio n or not. Patients should be referred to hospital for assess- ment and fresh frozen plasma treatment, if required. Most accidental ingestions will not require treatment other than ob servation and serial clotting studies. Rapid complete reversal is clearly not appropriate i n those who are normally therapeutically anticoagulated. POISONS1 413 Antifreeze (see ethylene glycol) Antihistamines Examples Astemizole, terfenadine, loratadin e, chlorpheniramine, promethazine Clinical features - Flushing - Increased temperature - Anxiety/agitation - Dry mouth and mu cous membranes - Dilated pupils - Fits (rare) - Cardiac arrhythmias (rare) - Delerium/coma (rare). These are the features of acute anticholinergic syndrome. Severe anticholinergic sy ndrome is more common with older antihistamines such as chlorpheniramine and promethazine t han with newer ones such as astemizole. Antihistamines are also found in a range of proprietary cough medications. Management - Maintain and establish a patent airway - Monitor pulse, BP, ECG, and SpO2 - Di azemuls for persistent or repeated seizures - Bicarbonate 1 \200\2233mmol/kg (if available) for life-threatening arrhythmias - Urgent transfer to hospital. CHAPTER 6 Poisoning and substance abuse 414 Barbiturates Examples Amylobarbitone, butobarbitone, quinalbarbitone, phenobarbitone General features Barbiturate overdoses were once very common. With prescriptions now restri cted to long-term barbiturate users, they are rare. Clinical features - Drowsiness - Dizziness - Ataxia - Coma - Respiratory depression - Hypot ension - Hypothermia - Skin blistering occurs in a minority of patients. Management - Establish and maintain a clear airway (the gag reflex is lost in severe overdoses) Support respiration - Activated charcoal 50g (if available) with airway protection - Urgent transfer to hospital. POISONS1 415 Batteries General features Small children are at risk of swallowing \200\230button \200 \231 type batteries of the kind found in toys, watches, and a wide variety of everyday item s. Clinical features The majority of swallowers will not show any symptoms. When these are pre sent, they include: - Retrosternal discomfort - Nausea and vomiting - Cough - Difficulty in swallowing. Later symptoms (which may be life-threatening) relate to erosion of the batter y through the oesophageal wall, internal electrical burns, and the local and systemic effec ts of leaking chemicals. As a result, these ingestions must be taken seriously. Management ALL patients who are known or suspected to have swallowed a button type battery should be directed or taken to hospital for X-ray and further management. Where possible, a sample of the type of battery should accompany the patient. CHAPTER 6 Poisoning and substance abuse 416 Benzodiazepines Examples Nitrazepam, loprazolam, temazepam, diazepam. Clinical features - CNS depression (drowsiness to coma) - Respiratory depression - Hypotens ion (rare) - Ataxia (in children, rare) - Dysarthria. Management - Establish and maintain a secure airway (use the recovery position if necessary) Support respiration - Evacuate to hospital. FLUMAZENIL should NOT be used in the pre-hospit al environment. Its use can be complicated by convulsions, arrhythmias, and anxiety. Fatal reactions are recorded. In addition, its use may precipitate fitting in epileptics or those who have taken a mixed overdose which also includes epileptogenic substances. POISONS1 417 Beta blockers Examples Propranolol, acebutolol, atenolol, metoprolol, oxprenolol, sotalol Clinical features Beta blocker overdoses may be severe and regular fatalities occur. Cardiovascular - Bradycardia - Hypotension and circulatory Other - Airway constriction - Respiratory depression - Hypoglycaemia - Sedation or coma - F its. failure AV block/conduction abnormalities Ventricular arrythmias - Cardiac arrest. Depending on the beta blocker, symptoms may take u p to two hours to develop. Management - Careful management of airway and breathing - ECG monitoring - URGENT transfer to hospital - Give activated charcoal if transfer to hospital is likely to be delayed or prolonged For bradycardia: atropine 0.04mg/kg or 500 g iv (repeated if necessary) Glucagon 2 \200\2235mg iv stat for significantly symptomatic patients. Larger doses than th ose conventionally carried are often required, including continuous intravenous infusion af ter hospital arrival. CHAPTER 6 Poisoning and substance abuse 418 Bleach General comments The active constituent of most household bleaches is sodium hypochl orite in varying concentration. Bleaches are corrosive and give off chlorine when they reac t with gastric acid. Clinical features The majority of patients are young children, who rarely take enough to ca use serious problems, presumably because of the unpleasant taste and smell. Symptoms includ e: - Nausea and vomiting - Soreness in the mouth - Abdominal pain (rare). Late symptoms inc lude oesophageal perforation, hemorrhage, and shock. Management - Ensure a patent protected airway - Give milk - Transfer to A&E for assessment and monitoring. POISONS1 419 Calcium channel blockers Examples - Verapamil - Amlodipine, nifedipine, nimodipine, nicardi pine - Diltiazem. Clinical features Symptoms are normally apparent within 1 \200\2236 hours , but may be very delayed in overdose of sustained release preparations. Children are parti cularly at risk from ingestion of calcium channel blockers and deaths have been reported fo llowing ingestion of very small quantities. - Brady/tachycardias, sinus arrest, heart block - Cardiac arrest - Heart failure, cardiogenic shock - CNS depression/coma - Fits (rare \200\224more common in children) - Hyperglycaemia (rare). Management - Establish and maintain a patent airway (use recovery position if necessary) Give high-flow oxygen - ECG monitoring, oxygen saturation monitoring - Atropine (500 g ali quots) for bradycardia - Calcium iv (gluconate or chloride 10%, 10 \200\22320ml slowly) - U RGENT transfer to hospital. Intravenous fluid boluses may be used with care for hypotension , and external pacing may occasionally be necessary. CHAPTER 6 Poisoning and substance abuse 420 Carbamazepine Clinical features - Drowsiness - Confusion - Ataxia, loss of co-ordination - Dizziness - Nystagmus, pupillary dilatation Fits - Coma - AV block - Ventricular arrhythmias. (not always), strabismus Management Carbamazepine overdose is similar to tricyclic antidepressant overdose, although the complications are usually less severe. Supportive measures are usually all that are re quired. Significant arrythmias are treated with sodium bicarbonate by intravenous bolus usu ally after arrival in hospital. POISONS1 421 Carbon monoxide General comments Carbon monoxide is a colorless, odorless gas which is the product of incomplete combustion of carbon-containing compounds. Sources include: - Car exh aust fumes - Methane, coal, propane, butane, oil, kerosene, wood, and other fuels - Paint s tripper - Smoke from burning organic substances. In many cases, poisoning results from CO a ccumulation in a confined space where there is inadequate ventilation, ventilation has been blocked, or heating appliances are faulty. Mechanism of action CO binds to hemoglobin to form carboxyhaemoglobin, reducing its oxygen- carrying ability. The affinity of hemoglobin for CO is approximately 250 times that for oxy gen. Clinical features A high index of suspicion is essential. CO poisoning is more common in co ld weather and in the circumstances listed above. Early - Headache - Dizziness - Nausea - Vomiting (may be bloodstained). Later - Confusion - Lethargy - Nystagmus - Ataxia - Syncope - Shivering. Severe poisoning - Coma - Pulmonary oedema - Hypotension - Increased muscle tone, hyperrefl exia, clonus, abnormal plantar responses Myocardial infarction - Cardiac arrest. The classical \200\230cherry pink \200\231 skin color of CO poisoning is rare. CHAPTER 6 Poisoning and substance abuse 422 Management - Remove the patient AND YOURSELF from the toxic atmosphere - Establish and main tain a patent airway - ADMINISTER HIGH-FLOW OXYGEN - Rapid transfer to hospital with intens ive care facilities. CAUTION: pulse oximetry gives falsely high readings in CO poisoning and should not be used (see pp.80 \200\2231). POISONS1 423 Chlorine General comments Chlorine is widely used in industrial processes, including the ma nufacture of plastics, bleaches, and hydrochloric acid. It is also used in water purifi- ca tion and may result from the mixing of bleach and other household cleaners. Chlorine produc es patchy necrosis of respiratory mucosa and acute pulmonary oedema. It is a greenish yellow gas which is heavier than air and may accumulate in low or enclosed areas. Mechanism of action Reacts with water to form hydrochloric acid, resulting in tissue irritation and pain. Clinical features - Mucous membrane irritation - Coughing, choking, dyspnoea, bronchospasm, chest pain, hypoxia, and pulmonary oedema Respiratory arrest - Respiratory symptoms which are likely to be worse in those with pre-existing lung disease (for example, asthma) Nausea and vomiting. Management - Remove from further exposure and give high-flow oxygen - Check peak flow - Sal butamol for bronchospasm - Artificial ventilation, if required - Copious lavage of exposed skin with water - Eye exposure: copious lavage with water or N.saline followed by fluoresce in staining or ophthalmology referral for assessment. CHAPTER 6 Poisoning and substance abuse 424 Corrosive substances \200\224acids and alkalis Uses Widely used in the chemical industry; a lso used in some domestic cleaning products. Clinical features Skin - Burns, often to hands and face. Ingestion - Burning pain in lips, throat, chest, and epigastrium - Vomiting. Inhalation - Pulmonary oedema. Eyes - Corneal ulceration. Management - Establish and maintain a patent airway; administer high-flow oxygen - Give mil k (to help neutralize the corrosive) - Analgesia as required - Prolonged irrigation with wa ter for skin contamination - Immediate lavage of contaminated eyes with water (tap water is fine) at scene Transfer to hospital. Attempts to neutralize an acid with alkali or vise versa are CONTRA- INDICATED. POISONS1 425 CS gas General comments CS gas is used for riot control, control of violent or aggressive p ersonages by the police, and in exercises by the Armed Forces. Clinical features - Burning eyes with blepharospasm - Upper respiratory burning - Bronchosp asm and dyspnoea - Panic. Management - Remove from contaminated area - Remove clothing - Irrigate the eyes - Showerin g - Transfer to hospital for management and assessment of associated injuries. CS gas \200\230clings \200\231 to clothing and \200\230off-gassing \200\231 may continue for some time, causing distress to rescue personnel, especially in enclosed spaces such as the back of an ambulance. Patients who refuse to attend hospital should be advised to shower on arrival at home and to leave their clothes outside. CHAPTER 6 Poisoning and substance abuse 426 Cyanide General comments Cyanide is widely used in industry in processes including metal ex traction, laboratory analysis, electroplating, and photography. It may also result from the burning of a wide range of synthetic products such as plastics. There are also natural sou rces including apricot and cherry kernels and some nuts. Cyanide inhibits a wide range of e nzymes, most importantly, cytochrome oxidase. Clinical features Early neurological symptoms include: - Headache - Anxiety - Confusion - D izziness - Weakness - Patients may subsequently develop coma and convulsions. Cardio-respiratory symptoms include: - Dyspnoea - Tachypnoea - Pulmonary oedema - Tachy bra dycardia - Respiratory and cardiac arrest - Death may not occur for several hours. Management - Ensure the patient is removed from the toxic environment \200\224DO NOT ENTER HAZARDOUS AREAS Remove contaminated clothing \200\224DO NOT GET CONTAMINATED - Wash contaminated skin thoro ughly. There are a number of cyanide antidotes including dicobalt edetate (600mg iv followe d, if the response is unsatisfactory, by 300mg) or sodium nitrite and sodium thiosulphate. Both these regimes are poten- tially toxic in the absence of cyanide poisoning and the diag nosis should be reasonably likely before they are used. In some cases, transfer to hospital (with the kit) may be the most reasonable option. One or other antidote should be availabl e at sites where there is a risk of cyanide poisoning. POISONS1 427 Detergents and related substances Examples Soaps, detergents, fabric conditioners. General comments Usually consumed by toddlers and small children. Clinical features - Nausea, vomiting, and diarrhea - Other symptoms are rare but substances containing benzalkonium chloride are more toxic and may cause coma, convulsions, and respi ratory failure. Management - Encourage fluids - Administer milk - Discuss with poisons advice center (see p .399) in mild cases - Transfer to hospital in potentially serious cases. CHAPTER 6 Poisoning and substance abuse 428 Digoxin and related drugs (cardiac glycosides) Examples Digoxin, digitoxin. Clinical features Overdoses of cardiac glycosides are rare, the symptoms are: - Nausea, vom iting, diarrhea - Fatigue, confusion, lethargy, delirium (rarer) - Hyperkalaemia leading to arrhythmias - Sinus arrest, sinus bradycardia, AV block - Ventricular arrythmias (rarer). Management - Cardiac monitoring - Consider activated charcoal if transfer is delayed or lik ely to be prolonged Atropine for symptomatic bradycardia - Conventional management for other arrhythmias (isola ted ventricular ectopics do not need treatment) Transfer to hospital for further therapy, potentially including digoxin \200\223specific antibodies Calcium is contraindicated as it may worsen arrhythmias. POISONS1 429 Disinfectants Clinical features - Burns of lips, mouth, and upper GI tract - Hoarseness, st ridor, airway obstruction - Ataxia, CNS depression, coma (pine oil-containing disinfectants ) - Shock, hypothermia, respiratory failure, myocardial damage, shock (phenol-containing disinfectants). Management - Establish and maintain a patent airway - Give milk (in conscious patients) - T ransfer urgently to hospital. These overdoses should be taken seriously as a number of dete rgents still contain toxic substances such as phenol. Evacuation to hospital is, therefore, appropriate. CHAPTER 6 Poisoning and substance abuse 430 Ethanol General comments Although drunkenness is extremely common, severe alcohol poisoning is, fortunately, extremely rare. It occurs more commonly in young adults unused to habitua l alcohol excess. Probably the most common cause of alcohol-related death (apart from traum a) is airway obstruction, often secondary to vomiting. It should be remembered that ethanol potentiates the CNS depressant actions of a wide range of drugs. In addition, patients under the influence of alcohol fall, get assaulted, and of ten neglect themselves. The possibility of associated injuries and medical conditions shoul d not be forgotten. Clinical features - Confusion, aggression, disinhibition - CNS depression leading to coma - Hypotension - Hypothermia - Respiratory failure - Hypoglycaemia in children. There is usua lly the characteristic smell of alcohol on the breath. Hypoglycaemia is rare in adults but much more common in children. Management - Establish and maintain a patent airway (use the recovery position if there is no possibility of cervical spine injury); ensure working suction is available Assist ventilation (where necessary) and administer high-flow oxygen - Check a BM stix - In mild cases, the patient may be left in the care of a responsible adult - In serious cases (for example, where the airway is threatened), the patient should be admitted to hospital for observation. NOTE High concentrations of ethanol are also found in perfumes, aftershaves, mouthwashes, a nd over-the-counter cough and cold remedies. POISONS1 431 Ethylene glycol General comments Ethylene glycol is the active ingredient in antifreeze and motor coolant fluids. Cases of ethylene glycol poisoning have also resulted from deliber- ate contamination of alcoholic drinks such as wine. Clinical features - Ataxia - Slurred speech - Nausea and vomiting - Convulsions - Drowsines s and coma. Later symptoms (after 12 hours) are predominantly cardiorespiratory, including arrhythmias, bronchopneumonia, and cerebral oedema. These are unlikely to be encountered in the pre-hospital environment. Management - Establish and maintain a patent airway - Treat complications symptomatically - Transfer to hospital URGENTLY for investigation and management. The diagnosis of ethylene glycol poisoning is often far from obvious. If it can be established with reasonable certai nty that the patient has taken ethylene glycol, and they are capable of taking it, ethanol (as whisky, gin, or vodka containing 40g/l ethanol) can be given my mouth. Ethanol \200 \230mops up \200\231 alcohol dehydrogenase, reducing the metabolism of ethylene glycol into toxic metabolites. CHAPTER 6 Poisoning and substance abuse 432 Fungi \200\224poisonous Examples - Amanita phalloides ( \200\230death cap \200\231 mushroom ) \200\224the most common cause of fatalities from eating mushrooms Gyrometra spp - Psilocybe spp. Clinical features A wide range of symptoms is possible. Early nausea, vomiting, and diarrhe a may occur. Other symptoms include profuse sweating, salivation, abdominal pain, hallucina tions, headache, flushing, and blurred vision. Management Early management is supportive, with urgent evacuation to hospital. Wherever pos sible, a sample of the ingested fungus (fungi) should accompany the patient to hospital. In travenous fluids may be commenced and an antiemetic given. POISONS1 433 Hypoglycaemic agents Examples Tolbutamide, chlorpropramide, gliclazide, glipizide, tolazami de, glibencla- mide. These are sulphonylureas; metformin (a biguanide) does not cause hypog lycaemia in overdose. Clinical features - Reduced conscious level or coma - Pupillary dilatation (not always pres ent) - Neurological abnormalities including upgoing plantars and hyper-reflexia Fits. Hypoglycaemia due to sulphonylurea overdose can be extremely prolonged and recurrent, even after treatment. Careful monitoring and repeated BM stix readings are, therefore, ess ential. Management - Establish and maintain a secure airway - 10% dextrose by slow IV injection (IV glucagon is an alternative, initial dose 1mg) Fits may respond to correction of hypolycaemia; otherwise use diazemuls 2.5mg every 30 seconds until control is achieved Urgent transfer to hospital. NOTE: glucagon is ineffective in patients with inadequate glycogen stores such as alcoholic s. CHAPTER 6 Poisoning and substance abuse 434 Insulin Clinical features - Reduced conscious level or coma - Pupillary dilatation (not alw ays present) - Neurological abnormalities including upgoing plantars and hyper-reflexia Fits. Management - Establish and maintain a secure airway - 50% dextrose (50ml initially) by slow iv injection ( iv glucagon is an alternative, initial dose 1mg) Fits may respond to correction of hypoglycaemia; otherwise use diazemuls 2.5mg every 30 seconds until control is achieved Urgent transfer to hospital. Depending on the insulin injected, repeated doses of glucose o r a dex- trose infusion may be necessary to prevent recurrence of symptoms. Regular monitoring of BM stix is essential POISONS1 435 Iron Clinical features For such a widely prescribed ( and self-prescribed ) medication, iro n can be remarkably toxic in overdose or poisoning. Accidental ingestion of iron supplement s is not uncommon in children. - Vomiting (or haematemesis) and diarrhea (may be black or g ray) - Abdominal pain - Lethargy, drowsiness, coma - Fits - Shock - Later symptoms (after a bout 12 hours) include shock, acidosis, jaundice, and renal failure. Management - Establishment and maintenance of a patent airway - Symptomatic treatment of co mplications - URGENT referral to hospital. Where possible, the remaining medication or its container should accompany the patient to hospital so that an estimate of the amount of ele mental iron ingested can be made. CHAPTER 6 Poisoning and substance abuse 436 Lithium Clinical features - Nausea, vomiting, and diarrhea - Tremor, hyperreflexia, agitati on - Fits - Coma. Non-specific ST depression and T wave inversion may be found on the ECG. Malignant arrhythmias are rare. Management Pre-hospital management is supportive. A patent airway should be estab- lished a nd maintained. If transfer to hospital is likely to be delayed or prolonged, an intravenous infusion should be commenced. ECG monitoring is essential. POISONS1 437 Mefenamic acid Mechanism of action Mefenamic acid is a non-steroidal anti-inflammatory drug . General features Prescribed for menorrhagia and dysmenorrhoea, as well as arthritides and r elated conditions, mefenamic acid (Ponstan ) is relatively commonly taken in overdose. Clinical features - Muscle twitching - Fits - Diarrhea and vomiting. Management - Establish and maintain a protected airway - Diazemuls for prolonged or recurre nt seizures - Urgent evacuation to hospital - Give activated charcoal if transfer is likely to be delayed or prolonged. CHAPTER 6 Poisoning and substance abuse 438 Methanol General comments Methanol is used in windshield washer fluids, as a component of m ethy- lated spirits (not in significant levels), as a fuel antifreeze additive, and as an i ndustrial solvent. Methanol poisoning may result from the consump- tion of contaminated or adulterated wines. Clinical features - Nausea, vomiting - Abdominal pain and diarrhea, rigid Headache - Dizziness - Breathlessness - Sweating - Convulsions (rare) - Cardiorespiratory abdomen Visual abnormalities (including blurred vision, flashing lights, and decreased visual acuity). May progress to blindness. Photophobia failure. Management - Establish and maintain a patent airway (use the recovery position if there is no possibility of cervical spine injury) Assist ventilation (where necessary) and administer high-flow oxygen - Diazemuls for fittin g - If the patient is well enough and hospital transfer is likely to be prolonged or delayed, oral ethanol can be given in the form of whisky, gin, or vodka (40% p roof). - Urgent transfer to hospital. POISONS1 439 Metoclopramide Clinical features Overdosage or poisoning with metoclopramide does not appea r to be a problem. A minority of patients, however, suffer acute dystonic reactions. These include chewing movements, spasms of torticollis, and oculogyric crisis. These movements ca nnot be controlled by the patient, who remains fully conscious throughout. Management The treatment of acute dystonia is procyclidine 5 \200\22310mg im (adult dose) o r benztropine 1 \200\2232mg im or iv (adult dose). If one of these is not available, the pa tient should be reassured and transferred to A&E for treatment. CHAPTER 6 Poisoning and substance abuse 440 Monoamine oxidase inhibitors (MAOIs) Examples - Phenelzine, tranylcypromine, isocarboxazid, moclobemide - The anti-parkinsonian agent, selegiline, and the chemotherapeutic agent, procarbazine, are also MAO inhibitors. Clinical features - Headache - Agitation - Hallucinations - Flushing - Sweating - Muscular rigidity - Tachycardia - Tachypnoea - Hypotension, bradycardia, Abnormal muscular movements (writhing, grimacing) Coma - Nystagmus - Hyperpyrexia - Hypertension. and asystole Symptoms may initially be entirely absent, even in very serious over- doses.