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TOXICOLOGY WORKSHOP GENERAL APPROACH AND SPECIFIC AGENTS MASTERS FIJI 30/10/15 General approach RRSI DEAD Resus Risk assessment (medical and psych) Supportive cares/monitoring Investigations Decontamination charcoal & whole bowel irrigation Enhanced elimination MDAC, urinary alkalinsation, dialysis Antidotes Disposition Resuscitation ABC Detect and correct Hypoglycaemia Seizures Hypo/hyperthermia Emergency antidote Risk assessment Medical and psychiatric Who? What? Time since ingestion Where? Drug and dose; always ask about coingestants!!! When? Patient characteristics – age/gender/PMHx/psych Hx Likelihood of being found Why? Precipitants – financial/social/marital etc Ongoing suicidality/plans Supportive cares/monitoring Full non-invasive – monitoring for development/worsening of toxicity Visual – may attempt to leave; plan for detainment? Investigations ECG Na channel blocker tox Prolonged QTc tachycardia CBG/BSL SPIESVQ – salicylates, propranolol, insulin, ethanol, sulfonylureas, valproate, quinine BhCG Precipitant Child at risk (paracetamol levels) NB NAC 100% effective at preventing hepatotoxicity if administered within 8 hours of overdose Decontamination - 1 Charcoal 1g/kg to max 50g Indications for use Within 1 hr of toxic ingestion Benefits outweigh risks (eg aspiration) Toxin binds to charcoal Agents that don’t bind Hydrocarbons/alcohols – ethanol/methanol Metals – Li/Fe/Pb Corrosives – acids/alkalis Decontamination - 2 Whole bowel irrigation PEG via NGT at 2L/hr Indications Benefits outweigh risk Appropriate overdose S – slow release calcium channel blockers L – lead I – iron P – potassium tablets or packers Enhanced Elimination - 1 MDAC (multi dose activated charcoal) 1g/kg to max 50g initially then q2h (up to 6hrs ie max 4 doses) Interrupts enterohepatic circ; acts as GIT dialysis Amenable agents Quite Possibly Can’t Drink That Stuff Q - quinine P – phenobarbitone C – carbamazepine D – dapsone T – theophylline S – salicylates Enhanced Elimination - 2 Urinary alkalinsation 1-2mmol/kg NaHCO3 bolus then 100mmol NaHCO3 in 1L 5% dextrose @ 250ml/hr Traps acidic drug in renal tubules and increases excretion in urine Amenable drugs Salicylates Phenobarbitone (NB MDAC is superior) Enhanced Elimination - 3 Hemodialysis Consider in the following poisonings: Lithium – chronic with renal impairment Metformin induced lactic acidosis Potassium Valproate Alcohols Theophylline (treatment of choice in severe OD) Salicylates (treatment of choice in severe OD) Carbamazepine Barbiturates Toxidromes - overview Hypermetabolic Serotonin syndrome Neuroleptic malignant syndrome Anticholinergic syndrome Other Opiate Sympathomimetics Cholinergic Toxidromes - 1 Hypermetabolic (inc HR, BP, RR and temp) Serotonin syndrome Sweaty, increased tone/hyperreflexic/clonus, agitated -> coma Intro/inc serotonergic drug, inadequate washout, deliberate OD Eg fentanyl, TCAs, lithium, SSRIs (sertraline, fluoxetine) Neuroleptic malignant syndrome Sweaty, lead-pipe rigidity, bradyreflexia, mutism/staring RFs – high dose, recent inc dose, >2 neuroleptic agents, dehydration Eg haloperidol Anticholinergic syndrome Red, hot and dry; normal tone/reflexes; agitated delirium Eg antihistamines, TCAs Toxidromes - 2 Other Opiate Miosis, respiratory depression, reduced level of consciousness Naloxone 100mcg q30-60 sec until adequate spont resp Sympathomimetics CNS – agitation, euphoria, paranoid psychosis; CVS – inc HR/BP, ACS, APO, other – rhabdo, sweating, tremor Cholinergic CNS – agitation, coma, confusion, seizures; NM – fasciculation, muscle weakness; M receptors – DUMBBELS; N receptors – HTN, inc HR, sweating Organophosphates Specific agents Tried to identify most high yield for exam Commonly available Major toxicity Antidote available Decontamination/enhanced elimination important Toxic Alcohols – Ethylene Glycol Toxicity Glycolic acid & oxylate -> 1mL/kg = toxic Severe metabolic acidosis + calcium oxylate deposition (kidneys/myocardium/ muscles & brain) Rapid progression to symptoms to shock, coma, seizures and death – early renal failure Management DEA Antidote = ETOH; Haemodialysis Resus/Supportive Intubation/hyperventilation (severe acidosis) IV benzo’s for seizures Avoid hypoglycemia Correct hypocalcemia – oxylate calcium crystals (ECG prolonged QT) Toxic Alcohols - Methanol Toxicity > 0.5mL/kg = toxic Intoxication – then latent period (12-24hrs) Dizziness/vertigo, dyspnoea, blurred vision – progressive obtundation – coma & seizures Management DEA - Antidote = ETOH; Haemodialysis Resus/Supportive Intubation/hyperventilation (severe acidosis) IV benzo’s for seizures Avoid hypoglycemia Amphetamines Toxicity sympathomimetic effects Lethal complications – severe hyperthermia; Cardiac (ACS, aortic dissection, arrhythmias); CNS (ICH) Management DEA – None Titrated benzo’s Treat tachycardia/hypertension with Hydralazine/GTN (second line) B-BLOCKERS CONTRAINDICATED Resus/Supportive Agitation with IV benzo’s – may need to I&V for control CNS agitation Hyperthermia – active cooling Monitor for hyponatremia Monitor for Rhabdo/ renal failure B-blockers (propanolol/sotalol) Toxicity other b-blockers have minimal toxicity Propranolol – 1g = toxic CVS effects – hypotension/bradycardia; 1st – 3rd degree block. Propranolol – QRS prolongation & CNS depression Sotalol – QT prolongation – risk torsades Management DEA – none (charcoal if NOT propranolol- CNS) Antidote – NaHCO3 for propranolol Resus/Supportive – usual Propranolol – manage as TCA prompt intubation, ventilation and NAHCO3 for VT/VF Manage Hypotension & bradycardia – Fluids, inotropes, pacing Calcium channel blockers (verapamil/diltiazem) Toxicity – little as 2-3 x therapeutic dose (10 tabs = toxic) CVS – hypotension/ heart block; Metabolic hyperglycemia/lactic acidosis Management DEA Decontamination – Charcoal & WBI; Antidote = Calcium & HIET ( 25g Glucose; 1U/Kg bolus) Resus/Supportive Calcium – 20ml of 10% CaCl over 15mins – repeat x 3 Escalated approach – hypotension & bradycardia (atropine –upto 3mg) Carbamazepine Toxicity - 20-50mg/kg (mild-mod); > 50mg/kg CNS/anticholinergic – agitation/coma; CVS – hypotension;QRS VF/VT Management DEA – activated charcoal; MDAC (if intubated); Hemodialysis Resus/Supportive Arrhythmias – sodium bicarbonate; graded response to hypotension Seizures/agitaiton – IV benzo’s Carbon monoxide Toxicity(% CoHb) – Non-specific/mild headache, N&V – progress ot CNS disturbance, confusion/coma & syncope; > 50% - cardiovascular & respiratory collapse Management High flow O2 Hyperbaric oxygen if available (especially pregnant pt’s) Resus/specific As per usual Corrosives Toxicity – direct chemical injury to tissues – dependent on type; concentration & amount Alkaline agents = liquefactive corrosives Acidic agents = coagulative necrosis Management DEA – none Resus/Supportive Airway – high risk dysphonia/dyspnoea/stridor – secure early NO NGT until AFTER endoscopy S&S correlate poorly with extent of gastrooesophageal injury Steroids = no evidence Evidence of perforation = early surgical intervention (erect CXR) Digoxin Toxicity Acute 10mg (adult); > 4mg (child) – CVS collapse/dysrhythmias & severe hyperkalemia Chronic non-specific – N&V/GIT; headache; visual & CVS Management DEA – Antidote – digoxin immune Fab – formula to measure amount Resus/Supportive Cardiac arrest – standard measures futile without Antidote – prolonged resuscitation indicated if digoxin given Beware of IV calcium for hyperkalemia (controversial) Atropine for heart block IV lignocaine 1mg/kg for ventricular dysrhythmias Glyphosate Toxicity directly related to concentration (herbicide) Effects – GIT – N&V/oropharyngeal erosions; RESP – upper airway obstruction/burns; aspiration pneumonitis; CVS – myocardial depression (systemic acidosis) Management DEA – only hemodialysis (but rarely indicated – 4 severe met acidosis) Resus/Supportive Airway- intubate early if airway compromise CVS – escalated approach Hydrocarbons Toxicity – ingested or inhaled – cause rapid CNS depression; seizures & (rarely) cardiac dysrhythmias. Ingestion can be complicated by aspiration = aspiration pneumonitis Management DEA – decontamination (clothes) Resus/Supportive VT/VF – intubate & hyperventilate; Correct hypoxia Administer Metoprolol IV/ ?labetalol Correct hypokalemia/hypomagnesemia With-hold catecholamine inotropes if possible Hydrofluoric acid Toxicity – dermal/inhaled/ocular OR oral Fluoride ions bind directly to ca/mg+ and interfere with potassium channels Ventricular dysrhythmias n.g. can have severe dermal injury despite minimal signs (delayed presentation) Management DEA – decontaminate skin/irrigate with water; CALCIUM nb. Can administer calcium GLUCONATE via s/c OR IV arterial infusion Resus/Specific CARDIAC MONITORING – prolonged QT correlates to hypocalcemia Iron Toxicity – < 20mg/kg – Asymptomatic; 20- 60mg/kg – GI; Systemic > 60mg/kg; > 120mg/kg – potentially lethal Local GI and systemic effects =Direct GI toxicity and direct cellular toxicity systemically – CVS system & liver (CVS instability and metabolic derangements) Management DEA – WBI (if awake and toxic dose)- XRAY; Antidote – Desferroxamine (if shock; metabolic acidosis or altered mental state Resus/Supportive Circulation – emphasize fluid replacement (3rd spacing/GI loss) HCO3 = surrogate marker for lactate/systemic poisoning monitor CBG Seek & treat electrolyte abnormalities – fluid losses Lithium Toxicity – acute versus chronic Acute – GI toxicity – N&V/abdo pain etc Chronic – Neurotoxicity – particularly cerebellar effects NOTE: acute or chronic impairment of renal function, dehydration or sodium depletion impairs lithium excretion Management DEA – Elimination via dialysis (not usually required if normal RFT’s) Resus/Supportive CVS – fluid resuscitation; monitor fluids and electrolytes NB. Significant obtundation or seizure activity is an indicator of severe toxicity (chronic) carrying permanent neurological sequale Metformin Toxic effects > 10g OR therapeutic dose with ARF Alters cellular glucose metabolism– toxic component = lactate Patient has non-specific features of toxicity – altered sensorium, N&V, diarrhea, dyspnea, hypotension Management Haemodialysis – corrects acidosis & removes metformin Supportive seek and treat hypoglycemia Often precipitated by infection/sepsis if on therapeutic dose Organophosphates Toxicity Inhibit ACH-esterase inhibitors – symptoms due to Ach at nicotinic & muscarinic receptors Cholinergic – DUMBELS; Nicotinic – fasciculations, tremor, respiratory muscle paralysis; tachycardia and hypotension Management DEA – decontamination: remove clothes; wash skin etc; elimination: Atropine & Pralidoxime (re-activates Ache b4 ageing occurs Resus/Supportive Potential early life threats – COMA; Hypotension; seizures; Respiratory failure Atropine – 1.2g – double dose every 5 mins (drying of secretions) Electrolytes – monitor and replace; hypoglycemia – seek and treat Organophosphate induced delayed neuropathy (OPIDN) Paraquat Toxicity – mouthful only required – severe GI corrosive injury; pulmonary fibrosis and fulminating MOF & death Management DEA – administer food/soil on scene; In hospital give activated charcoal 50g asap Resus/Supportive Do NOT administer supplemental O2 unless <90% and aim for sats no greater than 91% Paracetamol Toxic effects NAPQ = toxic metabolite (>150mg/kg OR 10g in adult) Phase 1 (<24hrs) - Mild – N&V/none Phase 2 (1-3 days) – RUQ pain & hepatotoxicity Phase 3 (3-4 days) – fulminant hepatic failure – Coagulopathy/ jaundice/ encephalopathy Management Antidote =NAC – commence within 8 hrs Supportive Anti-emetics; anaphylactoid reactions to NAC Salicylates Toxicity > 300mg/kg – severe intoxication; > 500mg/kg – lethal Vomiting; tinnitus & hyperventilation – resp alkalosis & metabolic acidosis. Severe toxicity – seizures/coma Management DEA – Decontamination upto 8hrs post; Urinary alkalinisation & haemodialysis (rarely required if charcoal/urine alk. are used) Resus/Supportive I&V (for coma/respiratory insufficiency) – maintain hyperventilation Fluid – ensure replacement of losses Closely monitor glucose & potassium Sulfonylureas Toxicity- unpredictable metabolism (particularly in overdose); therapeutic dose if ARF results in hyper-insulinaemic state Management Decontamination – if given within 1hr & normal mental state Antidote – Octreotide Supportive may have prolonged effect for DAYS – needs v.close monitoring Theophylline Toxicity – both acute overdose & chronic toxicity can be lifethreatening; >10mg/kg – potential toxicity; > 50mg/kg – life threatening Effects – CVS – Tachyarrhythmias/Hypotension; Seizures; Metabolic – hypokalemia; hyperglycemia and metabolic acidosis Management DEA – Decontamination – charcoal; Hemodialysis – life-saving Resus/Supportive Seizures- IV benzos Tachyarrhythmias – SVT – control with b-blockade Hypotension – IV fluid bolus usually enough Seek & treat electrolyte abnormalities Tricyclic antidepressants Toxicity – sodium channel blockade > 10mg/kg = potential life threat Onset of toxicity within 2 hrs CNS – sedation/seizures/coma –needs early intubation CVS – ventricular dysrhythmias; Anthicholinergic features Management DEA – Charcoal if intubated (toxic dose); Antidote – NaHCO3 Resus/Supportive Immediate NaHCO3 – repeat doses & infusion (QRS <100msec) Early intubation - & hyperventilation – pH 7.55 IV benzos for seizures Monitor electrolytes; Catheter for fluid balance/urinary retention Warfarin Toxicity – BLEEDING. Management DEA – activated charcoal if within 1hr; Antidote – Vit K& FFP Resus/Supportive Dependent on bleeding & indication for warfarin n.b. can be managed on outpt basis if asymptomatic & INR < 9.0 Sea Snakes Toxicity – post-synaptic neurotoxins & myotoxins Rarely aggressive and most bites occur when handling to remove from fish nets Management DEA – pressure immobilization; sea snake antivenom OR tiger snake Resus/Supportive Unlikely to be needed as apparently their mouths are so small they can’t bite beyond webbing between fingers
