What is the management approach for a 50-year-old male with zinc phosphate (rodenticide) poisoning who developed bradycardia and hypotension?

From the Guidelines

The management approach for a 50-year-old male with zinc phosphate poisoning who developed bradycardia and hypotension should prioritize hemodynamic stabilization with intravenous fluids and vasopressors, such as norepinephrine, as well as atropine administration for bradycardia. The patient's stable vitals initially, followed by the development of bradycardia and hypotension, indicate the need for close monitoring and aggressive intervention to prevent further deterioration.

Initial Management

• Intravenous fluids (normal saline bolus of 1-2 L) should be administered to ensure adequate circulation and help maintain blood pressure.
• Vasopressors, such as norepinephrine 0.1-0.5 mcg/kg/min titrated to effect, may be necessary to support blood pressure, as suggested by experts for managing shock in similar contexts 1.
• Atropine 0.5-1 mg IV should be administered for bradycardia and can be repeated every 3-5 minutes up to a maximum of 3 mg, based on recommendations for symptomatic bradycardia or conduction disturbances 1.

Specific Considerations

• Gastric decontamination with activated charcoal (50-100g) may be considered if the patient presents within 1-2 hours of ingestion, but gastric lavage should be avoided due to the risk of increasing phosphine gas release.
• Administration of magnesium sulfate (1-2g IV over 15 minutes) may help protect against cardiac arrhythmias.
• N-acetylcysteine may be used to combat oxidative stress, following a protocol such as a loading dose of 150 mg/kg over 1 hour, followed by 50 mg/kg over 4 hours, then 100 mg/kg over 16 hours.
• Sodium bicarbonate may be needed for metabolic acidosis, targeting a pH >7.2.

Ongoing Care

• Continuous cardiac monitoring is essential due to the potential for direct cardiac toxicity from phosphine gas, leading to myocardial depression, arrhythmias, and vascular collapse.
• The latest guidelines on managing patients with cardiac arrest or life-threatening toxicity due to poisoning emphasize the importance of timely and effective supportive care, including airway management, hemodynamic support, and correction of critical vital sign and metabolic derangements 1.

From the FDA Drug Label

ATROPINE SULFATE INJECTION, for intravenous use Initial U. S. Approval: 1960 INDICATIONS AND USAGE Atropine is a muscarinic antagonist indicated for temporary blockade of severe or life threatening muscarinic effects. DOSAGE AND ADMINISTRATION For intravenous administration. Titrate according to heart rate, PR interval, blood pressure and symptoms. Adult dosage Antisialagogue or for antivagal effects: Initial single dose of 0. 5 to 1 mg. Antidote for organophosphorus or muscarinic mushroom poisoning: Initial single dose of 2 to 3 mg, repeated every 20 to 30 minutes. Bradyasystolic cardiac arrest: 1 mg dose, repeated every 3 to 5 minutes if asystole persists.

The patient developed bradycardia which was responded to atropine, and hypotension that needs Noradrenaline.

• The management approach for this patient includes:
  • Atropine for bradycardia, as it is a muscarinic antagonist that can help increase the heart rate.
  • Noradrenaline for hypotension, as it is a vasopressor that can help increase blood pressure. The dosage of atropine should be titrated according to heart rate, PR interval, blood pressure, and symptoms, as stated in the drug label 2.

From the Research

Management Approach for Zinc Phosphate Poisoning

The management approach for a 50-year-old male with zinc phosphate (rodenticide) poisoning who developed bradycardia and hypotension involves:

• Monitoring of vital signs and cardiovascular symptoms, as zinc phosphide poisoning can cause fatalities, with most patients having mild symptoms, and gastrointestinal symptoms being the most common 3
• Administration of atropine for bradycardia, as seen in the patient's response to atropine 4
• Use of noradrenaline (norepinephrine) for hypotension, as patients with zinc phosphide poisoning may experience circulatory collapse, hypotension, and shock symptoms 5, 6
• Supportive care, including decontamination and antidotal therapy, as there is no antidote or specific treatment for zinc phosphide toxicity 7
• Close monitoring of blood pressure, cardiac rhythm, and electrolyte balances, as patients who present with abnormal vital signs or electrolytes may have more severe poisoning 3

Treatment of Bradycardia and Hypotension

• Atropine can be used to treat bradycardia, as it has been shown to be effective in patients with aconite poisoning presenting with hypotension and bradycardia 4
• Noradrenaline (norepinephrine) can be used to treat hypotension, as it is a common treatment for refractory cardiogenic shock caused by zinc phosphide toxicity 6
• Dopamine can also be used to treat hypotension, as it has been used in patients with aconite poisoning presenting with hypotension and bradycardia 4

Hospital Stay and Follow-up

• Patients with zinc phosphide poisoning should be observed in the hospital for at least 2 days, as the median hospital stay was 2 days in a retrospective cohort study 3
• Follow-up should include monitoring of cardiovascular and respiratory symptoms, electrolyte balances, kidney function, and blood glucose, as patients who survived and died showed significant differences in these parameters 3