Management of Zinc Phosphide Poisoning

Management of Zinc Phosphide Poisoning (oral/parenteral exposure):

A) MANAGEMENT OF MILD TO MODERATE TOXICITY

·      Supportive care

·      Do not induce emesis as this could cause off-gassing of phosphine and secondary contamination in enclosed areas

·      Circulatory and respiratory support PRN

B) MANAGEMENT OF SEVERE TOXICITY

·      Supportive care

·      Sodium bicarbonate for severe metabolic acidosis

·      Treat dysrhythmias

·      Seizures with benzodiazepines (barbiturates & propofol added PRN)

·      Provide oxygen for respiratory distress and/or acute lung injury

·      Treat hypotension with dopamine or norepinephrine.

C) DECONTAMINATION

·      Activated charcoal for ingestion less than one hour, for patients who are awake, alert, and cooperative.

·      Minimum of 240 ml water per 30 g charcoal.

·      Adults & adolescents: 25- 100 g

·      Children 1- 12 years old: 25- 50 g (0.5- 1 g/kg)

·      Infants up to 1 year old: 0.5- 1 g/ kg

D) AIRWAY MANAGEMENT

  ·      Bronchospasm: B2 agonist with oral/parenteral corticosteroids

E)  ANTIDOTE : Not Available

F)  OTHERS:

 ·      Severe symptoms like pulmonary oedema may be delayed for up to 72 h

 ·      Liver function tests abnormalities may be delayed up to 3 days

G) SEIZURE

·      Diazepam

·      Adult: initially 5- 10 mg IV or 0.15 mg/kg IV up to 10 mg per dose up to a rate of 5 mg/ min. May be repeated every 5-20 mins PRN.

·      Paeds: 0.1- 0.5 mg/kg IV over 2-5 mins up to a maximum of 10 mg/dose. May repeat dose every 5-20 mins PRN.

·      When no IV access, Diazepam PR: >12 years old: 0.2 mg/kg, 6-11 years old: 0.3 mg/kg, 2-5 years old: 0.5 mg/kg.

·      Other agents can be used: Midazolam, Lorazepam, Phenobarbital, Sodium Valproate, Levetiracetam.

·      Monitor for hypotension & respiratory depression

H) FLUIDS

·     Crystalloids can be administered judiciously

I)   HYPOTENSIVE EPISODES

·      Infuse 10 to 20 mL/kg of isotonic fluid and keep the patient supine. If hypotension persists, administer dopamine or norepinephrine. Consider central venous pressure monitoring to guide further fluid therapy.

·       DOPAMINE: Begin at 5 mcg/kg/min progressing in 5 mcgs/kg/min p increments PRN. If hypotension persists, dopamine may need to be discontinued and a more potent vasoconstrictor (eg, norepinephrine) should be considered

·       CAUTION: If ventricular dysrhythmias occur, decrease rate of administration. Extravasation may cause local tissue necrosis, administration through a central venous catheter is preferred.

·       NOREPINEPHRINE: 4 mg (1 amp) added to 1000 mL of diluent provides a concentration of 4 mcg/mL of norepinephrine base. Adult: 0.1 to 0.5 mcg/kg/min titrate to maintain adequate blood pressure. Child: 0.1 to 2 mcg/kg/min titrate to maintain adequate blood pressure.

·       CAUTION: Extravasation may cause local tissue ischemia, administration by central venous catheter is advised

J) VENTRICULAR ARRHYTHMIA

·      Evaluate for hypoxia, acidosis, and electrolyte disorders (particularly hypokalemia, hypocalcemia, and hypomagnesemia). Lidocaine and amiodarone are generally first line agents for stable monomorphic ventricular tachycardia, particularly in patients with underlying impaired cardiac function. Amiodarone should be used with caution if a substance that prolongs the QT interval and/or causes torsades de pointes is involved in the overdose. Unstable rhythms require immediate cardioversion. 

    ·    LIDOCAINE: Adult: 1- 1.5 mg/kg via intravenous push. For refractory VT/VF an  additional bolus of 0.5 to 0.75 mg/kg can be given at 5 to 10 minute intervals to a maximum dose of 3 mg/kg. Only bolus therapy is recommended during cardiac arrest. 

   ·      Once circulation has been restored begin a maintenance infusion of 1- 4 mg/min. If dysrhythmias recur during infusion repeat 0.5 mg/kg bolus and increase the infusion rate incrementally (maximal infusion rate is 4 mg/min)

   ·      Child: 1 mg/kg initial bolus IV/IO; followed by a continuous infusion of 20- 50 mcg/kg/min.

   ·     AMIODARONE: For ventricular fibrillation or pulseless VT unresponsive to CPR, defibrillation, and a vasopressor therapy give an initial dose of 300 mg IV followed by 1 dose of 150 mg IV. For stable ventricular tachycardias: Infuse 150 g over 10 mins, PRN. Follow by a 1 mg/min infusion for 6 h, then a 0.5 mg/min. Maximum total dose over 24 h is 2.2 g

   ·    Child: Infuse 5 mg/kg as a bolus for pulseless ventricular tachycardia or ventricular fibrillation; may repeat twice up to 15 mg/kg. Infuse 5 mg/kg over 20 to 60 mins for perfusing tachycardias. Maximum single dose is 300 mg. Routine use with other drugs that prolong the QT interval is NOT recommended.

 K) ACIDOSIS

 ·        Metabolic acidosis: Treat severe metabolic acidosis (pH less than 7.1) with sodium bicarbonate, 1 to 2 mEq/kg is a reasonable starting dose. Monitor serum electrolytes and arterial or venous blood gases to guide further therapy. 

References:
1. Micromedex
2. UpToDate. Available from: http://www.uptodate.com.ezp.imu.edu.my/contents/overview-of-rodenticide-poisoning?source=machineLearning&search=zinc+phosphide&selectedTitle=1%7E1&sectionRank=1&anchor=H352512775#H352516540
3. CDC. Available from: http://www.atsdr.cdc.gov/mmg/mmg.asp?id=1013&tid=214