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Seizure after an overdose

HKCEM College Tutorial. Seizure after an overdose. AUTHOR Dr Chan Chi Keung August, 2013. Case. M/72 Known history of COAD Convulsion in street, and a partially emptied pack of unlabeled drug besides Vitals: GCS 7/15 BP 149/106 P 202/min T - 36.8 SpO2 98 H’stix 6.5mmol/L.

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Seizure after an overdose

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  1. HKCEM College Tutorial Seizure after an overdose AUTHOR Dr Chan Chi Keung August, 2013

  2. Case • M/72 • Known history of COAD • Convulsion in street, and a partially emptied pack of unlabeled drug besides • Vitals: • GCS 7/15 • BP 149/106 • P 202/min • T - 36.8 • SpO2 98 • H’stix 6.5mmol/L A&E initial management & investigations?

  3. ECG findings?

  4. Arterial blood gas (ABG) • pH 7.14 • CO2 5.5kPa • O2 39.5kPa • HCO3 14 mmol/L • BE -14.5 • Na 145 mmol/L • K 2.6 mmol/L • Cl 98 mmol/L How to interpret?

  5. Another episode of generalized tonic clonic convulsion in resuscitation room now… What to look for in cardiac monitor? What are the anticonvulsant(s) of choice?

  6. Anticonvulsants for drug induced seizures • First line: • Diazepam 0.2mg/kg IV or midazolam 0.1mg/kg IV • Second line: • Lorazepam 4mg in adult, 0.1mg/kg in child • Third line: • Phenobarbitone 10mg/kg IV at max. rate 100mg/min • Propofol 1-2mg/kg IV with airway protection • Phenytoin is NOT used in drug induced seizure

  7. Patient progress (1) • Seizure terminated with Valium 10mg IV • 3rd episode seizures now, no regain of consciousness in between. • Which drugs can cause status epilepticus upon overdose?

  8. Status Epilepticus List • Isoniazid • Theophylline • OHA (Hypoglycaemia) • Bupropion (antidepressant for smoking cessation) • Tetramine (banned rodenticide in China) • Carbon monoxide (CO) … and a much longer list for common drug induced seizure

  9. Drug induced seizure (OTIS CAMPBELL) • Organophosphate, OHA • Tricyclic antidepressant (TCA) • Isoniazid, Insulin • Sympathomimetic • Camphor, cocaine, Carbamazepine ,Cyanide ,CO • Amphetamine, alcohol withdrawal • Methylxanthines • Phencyclidine • Benzodiazepine withdrawal, Bupropion • Ethanol withdrawal • Lithium, lignocaine • Lead, lindane

  10. Patient progress (2) • Drug history from electronic patient record: • Using theophylline, Ventolin and Becotide puff for COAD • Drug identification by on-duty pharmacist: theophylline

  11. Methylxanthines • Theophylline • Aminophylline (the water soluble derivative of theophylline) • Caffeine • Theobromine(from cocoa and cholcolate) • All are structurally similar to adenosine

  12. Mechanism of toxicity: Adenosine antagonist • Adenosine is an inhibitory neurotransmittor responsible for terminating seizures. Adenosine antagonism accounts for refractory seizures in methylxanthines overdose. • Other effects of adenosine antagonism: • inhibit histamine release, bronchodilatation (therapeutic effect in COAD/asthma) • Release of endogenous catecholamines

  13. Theophylline overdose:Signs & symptoms Died from: refractory seizure, tachyarrhythmias, hypotension

  14. Investigation • Urgent serum theophylline conc. • Correlate well with clinical toxicity • However turnover time may take several hours • Look for hypokalaemia • Severe hypoK indicates severe theophylline poisoning

  15. Specific Treatment Antidote Decontamination Supportive Management Exposure Termination Management • Supportive • ABC • For seizures • For tachyarrhythmia • Decontamination • Specific: enhance elimination

  16. Supportive management • ABC • For seizure: 1st line is benzodiazepine • For tachyarrhythmia: • 1st line is also benzodiazepine  reduce CNS excitation  decrease endogenous catechalamines release. • 2nd line: diltiazem or esmolol • Antiemetic for repeated vomiting • Cautious IV potassium replacement

  17. GI decontamination • Consider gastric lavage if: • Toxic ingestion (ie: not taking several tablets only!) • Present within 1 hour • Multiple dose activated charcoal (MDAC) if presented early or clinically symptomatic: • Activated charcoal 50g, followed by repeated dose 25g Q2-4H for 4-6 doses. MDAC is useful in what overdose?

  18. MDAC with proven efficacy on Tx of following poisoning ( ABCDEQ ) • AAspirin, aminophylline (=theophylline) • B Barbiturate • C Carbamazepine • DDapsone, dilantin, digoxin • EEpilim, extended release preparation • Q Quinine

  19. MDAC • Mechanism: • GI decontamination • Enhanced elimination by breaking enterohepatic re-circulation • Enhanced elimination by gut dialysis • Contraindication: • Unprotected airway (e.g.: drowsy patient without intubation) • Intestinal obstruction

  20. Enhanced elimination • Charcoal haemoperfusion (HP) or haemodialysis (HD) are recommended for life-threatening poisoning • Recurrent seizures • Ventricular arrhythmia • Refractory hypotension • Bld theophylline >90mg/L • Use together with MDAC Clearance of Theophylline

  21. END

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