(A&E) (Peri-Op & Anaesthesia)

Overview

• Opiate Overdose → most common cause of death due to drug overdose
  • Drugs involves = codeine, dimorphine, fentanyl, loperamide
  • Most commonly due to heroin and morphine
  • Risk Factors → mental health conditions, alcoholics, renal impairment (can’t excrete drug)
• Paracetamol Overdose → most common intentional drug overdose in UK
  • Max recommended dose is 2x 500mg tablets, 4x in 24 hours (ie. max dose = 2g in one day)
  • May be acute overdose or staggered overdose
  • Hepatotoxic
    • Patients at increased risk of developing hepatotoxicity ⇒ chronic alcohol use, HIV, p450 inducers and malnourished patients (eg. anorexia)
  • Most important prognostic factor = arterial pH (<7.30)
  • Patients may be asymptomatic or only have mild GI symptoms at initial presentation
• Aspirin Overdose → aka Salicylate Toxicity
  • Leads to a mixed respiratory alkalosis (due to hyperventilation) and raised anion gap metabolic acidosis (due to toxicity + acute renal failure)
  • Nephrotoxic

Making Diagnosis

Clinical Features:

• Opiate Overdose → bilateral miosis (’pinpoint pupils’), respiratory depression (bradypnoea), altered mental status, constipation, needle track marks, rhinorrhoea
• Paracetamol Overdose → nausea & vomiting, RUQ pain, jaundice (may signify acute liver failure), hepatomegaly, altered conscious level
• Aspirin Overdose → tinnitus, N&V, lethargy, tachypnoea (hyperventilation), diaphoresis, hyperthermia, agitation, seizures, coma
• TCA Overdoes → dry mouth, dilated pupils, agitation, blurred vision, arrhythmias (prolonged QT interval)

Investigations:

• Toxicology Screen
• Opiate → therapeutic trial of naloxone. May show reversal of overdose signs.
• Paracetamol → serum paracetamol concentration (whether treated or not based on nomogram), LFTs (ALT may be elevated), PT (may be prolonged). pH (<7.30 is bad).
• Aspirin → ABG (mixed respiratory alkalosis and metabolic acidosis), Salicylate Levels (repeat every 2 hours until peak level).
  • Classified according to peak salicylate levels ⇒ mild (<300 mg/L), moderate (300-700 mg/L), severe (>700 mg/L)