POISONING (OPIOID, BENZODIAZEPINES AND TRICYCLIC ANTIDEPRESSANTS)

Recognition

Definition

• “Poisoning occurs when people drink, eat, breath, inject or touch enough of a hazardous substance (poison) to cause illness or death. Some poisons can cause illness or injury in very small amounts. Illness may occur very quickly after exposure to a poison, or it may develop over several years with long-term exposure” (World Health Organisation)

Risk Factors

• Past medical history of psychiatric disorders including depression and self-harm
• Children under 5

History

If possible, ascertain if patient has:

• Previous admissions with self-harm or overdose
• Any known cardiac conditions
• Any allergies

Signs and symptoms

• Opioid
  • Symptoms
    • Nausea and vomiting
    • Confusion
    • Reduced Glasgow Coma Scale (GCS)
  • Signs
    • Reduced respiratory rate
    • Bradycardia
    • Pin point pupils
• Benzodiazepines
  • Symptoms
    • Pale
    • Clammy
    • Cool peripheries
    • Confusion
    • Slurred speech
    • Unsteady gait
    • Impaired attention
    • Reduced Glasgow Coma Scale (GCS)
  • Signs
    • Reduced respiratory rate
• Tricyclic antidepressants
  • Symptoms
    • Mydriasis
    • Fever
    • Dry skin
    • Confusion
    • Urinary retention
  • Signs
    • Tachycardia
    • Hypotension

Initial Assessment and Investigations

• ABCDE assessment
• Sit patient up if able to tolerate
• Assess patient’s airway– call an anaesthetist if airway compromised
• Monitor oxygen saturations and respiratory rate
  • If patient is hypoxic give Oxygen (O₂) to achieve target saturations. Initially give 15 L/min via a reservoir mask if the patient is acutely unwell
• Target saturations:
  • 94 - 98% for patients not at risk of hypercapnic respiratory failure
  • 88 - 92% for patients at risk of hypercapnic respiratory failure due to conditions such as Chronic Obstructive Pulmonary Disease (COPD)
• Examine patient’s chest. If the patient is vomiting there is a risk of aspiration
• Arterial blood gas (ABG)
• Chest X-ray if concerned about the patient’s ventilation or risk of aspiration. If the patient is unwell request a portable X-ray
• Obtain intravenous access by placing 2 large bore cannulae in the antecubital fossa. Take blood to check Full Blood Count (FBC), Urea and Electrolytes (U&Es), Liver Function Tests (LFTS), toxicology screen and Venous Blood Gas (VBG)
• Check Capillary Refill Time (CRT) - hold for five seconds and refilling should occur in 3 seconds
• Assess pulse rate, rhythm and character
  • Abnormal rhythms should be managed immediately as in “Arrhythmias - Bradycardia” and “Arrhythmias - Tachycardia” Chapters in the “Medical Emergencies” section
• Monitor heart rate and blood pressure
• 12 lead Electrocardiogram (ECG)
• Consider cardiac monitoring
• Call for senior help
• Listen to patient’s heart sounds
• Check urine output and consider catheterisation
• Intravenous (IV) fluids as required by clinical picture and balanced with patients’ risk of fluid overload. See more details in the “Circulation” Chapter in the “Response” Section under “Fluid Challenge”
• Check pupils are equal and reactive
• Assess Glasgow Coma Scale or ACVPU using the NEWS2 chart
• Check patient’s temperature and blood sugar
• Examine patient’s abdomen and legs
• Take urine sample for toxicology
• Consider venous thromboembolism prophylaxis

Response

Management

Immediate pharmacological management

• Specific antidotes
  • Opioid
    • Naloxone
      • The duration of action of naloxone is much shorter than most opioids therefore repeat doses or infusions may be required
  • Benzodiazepines
    • Flumazenil
      • Be careful in patients with benzodiazepine dependence as sudden withdrawal may cause seizures, arrhythmias and hypotension
  • Tricyclic antidepressants
    • Consider sodium bicarbonate for patients with cardiac arrhythmias

Referrals

• Discuss with senior member of the team
• Contact critical care outreach team
• Referral to general medical team
• Consider referral to Intensive Care Unit (ICU) if:
  • Failure to respond to medical management
  • Patient requires ventilator support
  • Patient requires blood pressure support
  • Deterioration of blood gas following medical management

Future management

• Once the patient is medically fit they need to be assessed by the psychiatric team to ensure they are safe to be discharged and have appropriate support