Toxicology for medical students and teachers

Toxicology for medical students and teachers

1. TOXICOLOGY

2. CASE 1

3. A 28 years old male, labourer and moderate drinker was admitted to the hospital with history of acute loss of vision after consumption of 200 ml of a liquid 3 days earlier. On questioning, the patient said that he had eye irritation and light headedness after the first few hours of the drink but considered these symptoms to be a minor annoyance. He also had nausea by the end of the first day but noted that this cleared overnight. During the second day of activity, he was again troubled by eye irritation, this time accompanied by vertigo, tinnitus, visual blurring, and photophobia.

4. Questions: A) From what type of poisoning is this patient suffering ? B) How will you manage this case?

5. Answers: A) Acute Methanol Poisoning B) Initial management should be focused on stabilizing the airway, breathing and circulation. Gastric Lavage. Methanol itself is of limited toxicity, but its metabolites produce toxicity. If methanol exposure is suspected, a stat blood level should be obtained.

6. Ethanol ( Competes Alcohol dehydrogenase) 10% in water- Administered through a nasogastric tube. Loading dose of 0.7 ml/kg is followed by 0.15 ml/kg/hour. Conc. Of 100mg/dl in blood is aimed. Fomepizole ( Inhibits alcohol dehydrogenase) 15 mg/kg IV loading dose over 30 minutes, followed by 10 mg/kg every 12h till serum methanol falls below 20 mg/ dL .

7. Sodium bicarbonate (10%) 100 ml, administered intravenously every two hourly. Calcium leucovorin 50mg injected 6 hourly to reduce blood Formate levels by enhancing its oxidation. Haemodialysis.

8. Case 2

9. A 27-year-old male was brought to the emergency department when he was found by his parents in his room and they found him confused and unable to recognise them. On arrival in the Emergency Department, the patient was alert and rational but had no recollection of the preceding events. On examination, the patient was drowsy. His heart rate was 142 beats per minute and respiratory rate was 12 per minute. His initial temperature was 35.5°C and the blood pressure was 130/82mmHg and remained stable throughout. The patient’s oxygen saturation on room air was 90%. The pupils were constricted bilaterally and reactive to light. He had tremors of both hands.

10. His neurologic examination was normal with normal deep tendon reflexes and no rigidity or clonus was noted . Laboratory investigations which included full blood count, urea and electrolytes, blood sugar level, liver function tests and thyroid function tests were normal . CT scan of the brain was done which was unremarkable.

11. Questions A) What is the most probable diagnosis? B) What is the specific antidote for this case ? C) Can the antidote be administered orally? D) How much time will it take for the antidote to act? E) What are the alternatives if the specific antidote is in short supply?

12. Answers A) Opioid Overdosage B) Naloxone – 0.4 – 0.8 mg i.v repeated every 2-3 min till respiration picks up. Can be repeated every 1-4 hrs according to the response.

13. C) No. Because, it undergoes extensive first pass metabolism. D) Less than 2 mins . E) Naltrexone, Nalmefene

14. Case 3

15. You are alerted that a 36-year-old, male agriculturist is being brought by ambulance to the Emergency Department where you are on duty. History reveals that, the patient suddenly developed headache, dizziness, weakness, nausea, vomiting, and diarrhoea. En route to the Emergency Department, he lost consciousness and experienced urinary and faecal incontinence. When the patient arrives at the Emergency Department, you note that his pupils were constricted and did not react to light.

16. He also had generalized paralysis, fasciculation, and is unresponsive to deep pain. Corneal and gag reflexes are absent. He has profuse salivation, diaphoresis, and excess lacrimation. Rales are noted during chest auscultation. He had tremors of both hands.

17. Questions: A) What is your most probable diagnosis ? B) How will you manage the case ? C ) What drug can be used as an adjunct to the antidote?

18. Answers: A) Organophosphorus compound Poisoning B) General measures – ABC Gastric Lavage Specific Antidote - Atropine 2 mg i.v every 10 minutes, till dryness of mouth, pupils dilate, and bradycardia is abolished. F requency of administration depends on the severity of poisoning .

19. C ) Pralidoxime ( Cholinesterase reactivator ) Initially I.V loading dose of 30 mg/kg, to be given over 20 minutes, followed by 8 mg/kg/hour continous infusion till recovery ; maximum 12 g per day

20. Case 4

21. A 27-year-old lady allegedly consumed a bottle of tablets used for Anemia . She was initially taken to a local hospital with abdominal pain, vomiting and gastric lavage given. After 48 h, she developed multiple episodes of hematemesis and melena and progressively became oliguric and drowsy. She was intubated and referred to our hospital 48 h after ingestion. At presentation, pulse and blood pressure were not recordable and resuscitated with colloids. CBC profile showed hemoglobin-2.8 g/dl, total WBC count-4,500/cu mm, platelet count-52,000/cu mm. LFT showed marked elevation in liver enzymes.

22. Questions: A) What is the most probable diagnosis? B) What is the management for this poisoning?

23. Answers: A) Iron Poisoning. B) Gastric lavage with sodium bicarbonate solution – to render iron insoluble. Egg yolk or milk – to complex iron. Iron chelating agent - Desferrioxamine

24. Desferrioxamine – injected i.m .(preferably) 0.5-1g repeated 4-12 hrly as required Injected i.v ( if shock is present) – 10-15mg/kg/hr. Max 75 mg/kg/day till serum iron falls below 300 mcg/dl. Alternatively – DTPA or Calcium edetate Diazepam i.v , if convulsions occur.

25. Case 5

26. A healthy male aged 30 years working in a jewellery factory was brought to the emergency department approximately 10 min after accidental ingestion of a liquid used to polish metal plates required for artificial jewellery. On admission, he was in severe shock but the skin was pink in colour. He was immediately resuscitated and put on mechanical ventilation. SpO 2  did not rise beyond 60% in spite of intermittent positive pressure ventilation with 100% oxygen.

27. Tremors and convulsions were also observed. Fundus examination revealed that retinal veins and arteries appear in similar red colour. Arterial blood gas (ABG) report revealed high anion gap metabolic acidosis. Electrocardiogram (ECG) showed global ST depression pattern with right bundle branch block (RBBB).

28. Questions: A) What is the most probable diagnosis? B) How will you manage this case ? C) What are the possible issues with the administration of antidote?

29. Answers: A) Cyanide Poisoning B) Sodium Nitrite – 10ml of 3% solution i.v is given – converts Haemoglobin to Methaemoglobin . Methaemoglobin combines with cyanide to form Cyanomethaemoglobin . Then, Sodium thiosulfate- 50ml of 25% solution i.v is given which converts Cyanomethaemoglobin to Methaemoglobin and Sodium thiocyanate which is excreted in urine.

30. C) The two major side effects of sodium nitrite from the antidote kit are excessive M ethemoglobinemia and hypotension. Methemoglobinemia is due to the oxidation of ferrous (+2) iron in hemoglobin to ferric (+3) by nitrite, and, therefore, care must be taken to avoid excessive nitrite doses. Hypotension results from the vasodilating action of nitrite.