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Perioperative med and anaesthesia Y3 > Drug overdose > Flashcards

Drug overdose Flashcards

1
Q

What is the definition of drug overdose?

A

Taking more opiates than you should (Heroin and morphine are responsible for most drug-related deaths) 

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2
Q

Describe the pathophysiology behind opioids

A
  1. Opioids are classified as agonists, partial agonists, or agonist-antagonists of the opioid receptors, which contributes to the specific clinical effects in overdose.
  2. Mu receptors mediate analgesia, sedation, respiratory depression, euphoria, gastrointestinal dysmotility, and physical dependence.
  3. Kappa receptors mediate analgesia, miosis, diuresis, and dysphoria.
  4. Less is known about delta receptors, which mediate analgesia, inhibition of dopamine release, and cough suppression.
  5. Sigma receptors are no longer considered opioid in character because they are not antagonised by naloxone. 
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3
Q

Describe the epidemiology of drug overdose

A

ELDERLY are more at risk because they are more likely to be on opiates 

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4
Q

What are the risk factors for opiate overdose?

A
  • Mental health conditions 
  • Alcoholics 
    Morphine toxicity at a lower dose due to: 
  • Hepatic impairment 
  • Renal impairment 
  • Hypotension 
  • Hypothyroidism 
  • Asthma (decreased respiratory reserve) 
  • There is increased risk of paracetamol toxicity in patients that are in glutathione deplete states. This includes eating disorders, HIV and malnutrition
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5
Q

What are some examples of opioids?

A
  • Codeine 
  • Diamorphine 
  • Dihydrocodeine 
  • Fentanyl 
  • Loperamide 
  • Methadone 
    (most commonly due to):
  • Morphine 
  • Heroin 
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6
Q

What are the symptoms of an opiate overdose?

A
  • Constipation (if chronic) 
  • Drowsiness (if acute overdose) 
  • Nausea and vomiting 
  • Loss of appetite 
  • Sedation 
  • Craving the next dose 
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7
Q

What signs of opiate overdose can be found on physical examination?

A
  • Respiratory depression (bradypnoea)
  • Altered mental status
  • Hypotension and tachycardia 
  • Bilateral miosis (pinpoint pupils) 
  • Track/needle marks
  • Rhinorrhoea
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8
Q

What investigations are used to diagnose/ monitor an opiate overdose?

A
  • Toxicology screen (can take a few days, should start ABCDE approach)
  • Paracetamol blood level (should be considered in patients who have self-poisoned) 
  • If in doubt, give a small test dose of naloxone : may show reversal of overdose signs
  • ABG (respiratory depression) 
  • FBC 
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9
Q

How would you manage an opiate overdose?

A
  1. Initial ventilation
  2. Initial naloxone (opioid antagonist- reverses overdose) administration: subcutaneously or intravenously every 2 to 3 minutes. 
  3. Repeat doses of naloxone 
  4. The duration of effect of most opioids is 4 hours or less, but some may last significantly longer. The effects of methadone, levomethadyl acetate (LAAM), and buprenorphine can last from 24 to 72 hours 
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10
Q

What complications can arise from an opiate overdose?

A
  • Hypoxia 
  • Aspiration 
  • ARDS 
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11
Q

Describe the prognosis of an opiate overdose

A

Timely administration of naloxone, and appropriate ventilation prior to antidote, results in complete reversal of the effects of opioid overdose 

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12
Q

What is meant by paracetamol overdose?

A

Paracetamol overdose is the excessive use of the medication paracetamol, also known as acetaminophen.

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13
Q

How can paracetamol overdose be classified?

A
  1. Acute overdose - excessive amounts in less than 1 hour, usually in context of self-harm)
  2. Staggered overdose - excessive amounts of paracetamol ingested over longer than 1 hour, usually in context of self harm)
  3. Therapeutic excess - excessive paracetamol taken with intent to treat pain or fever and without self-harm intent, ingested at dose greater than licensed daily dose (more than 75mg/kg/24 hours).
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14
Q

Describe the epidemiology of paracetamol overdose

A

Paracetamol is the most common agent for intentional self-harm in the UK. Paracetamol overdose accounts for 44% of all adult self-poisoning cases in the UK, with approximately 150,000 people admitted to hospital each year due to poisoning.

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15
Q

Describe the pathophysiology behind paracetamol overdose

A
  • Involves the buildup of a toxic substance called NAPQI (N-acetyl-p-benzoquinone-imine).
  • Normally, NAPQI is inactivated by glutathione, but during an overdose, glutathione stores are rapidly depleted, leaving NAPQI unmetabolised and resulting in liver and kidney damage. (most dmaage to liver- causes hepatotoxicity)
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16
Q

What are the presenting symptoms/ signs of paracetamol overdose?

A

Initially: Asymptomatic or mild GI symptoms
Nausea and vomiting
Loin/ RUQ pain
Haematuria and proteinuria
Jaundice
Abdominal pain
Coma/ altered conscious level
Hepatomegaly

17
Q

What investigations are used to diagnose/ monitor paracetamol overdose?

A
  • Serum paracetamol concentration (whether treated or not based on nomogram)
  • LFTs (ALT may be elevated)
  • PT may be prolonged
  • Venous Blood Gas - Severe metabolic acidosis pH<7.3
18
Q

How is paracetamol overdose managed?

A

The management of paracetamol overdose is dependent on the timing of ingestion, dose, and patient’s clinical condition:

  1. If <1 hour after ingestion and not staggered overdose + dose >150mg/kg= activated charcoal
  2. If ingestion <4 hours ago: Wait until 4 hours to take a level and treat with N-acetylcysteine based on level
  3. If ingestion 4-15 hours ago + dose >150mg/kg: Take immediate level and treat based on level OR if there is going to be a delay of ≥8 hours in obtaining the paracetamol level, start N-acetylcysteine immediately
  4. If staggered overdose (over >1 hour time period) or ingestion >15 hours ago/timing uncertainty + dose >150mg/kg: start IV N-acetylcysteine immediately
19
Q

What criteria is used to predict mortality from paracetamol overdose?

A

The King’s College Criteria is used to predict mortality from paracetamol overdose and to identify those patients who would potentially benefit from liver transplantation. It advises for urgent transfer for liver transplantation if:
- Arterial pH Less than 7.3
OR, all of:
- Serum creatinine > 300 µmol/L (3.4 mg/dL)
- Prothrombin time >100 seconds
- Grade III or IV encephalopathy

Other parameters suggestive of poor prognosis include:
- Bilirubin greater than 300 µmol/L (18 mg/dL)
- International normalized ratio (INR) greater than 6.5

20
Q

What is the max recommended dose of paracetamol?

A

2 x 500mg tablets, 4x in 24 hours (max is 2g in 1 day)

21
Q

Which patients are most at risk of liver hepatotoxicity following paracetamol overdose?

A
  • Chronic alcohol use
  • HIV
  • p450 inducers (SCARS)
  • Malnourished patients (e.g. anorexia)
22
Q

What is the most important prognostic factor for paracetamol overdose?

A

Arterial pH (<7.30) → bad

23
Q

What is an aspirin overdose?

A

Aspirin overdose (aka salicylate toxicity) is a potentially life-threatening condition that occurs when a person ingests an excessive amount of aspirin, either accidentally or intentionally. This can lead to a variety of systemic effects, and may result in severe organ damage if not treated promptly.

24
Q

Describe the epidemiology of aspirin overdose?

A

Aspirin overdose is a common occurrence, primarily due to its widespread availability as an over-the-counter medication. It can occur in all age groups but is most common in adolescents and adults, particularly those with a history of mental health disorders or substance abuse.

25
Q

What are the signs/ symptoms of an aspirin overdose?

A

Acute overdose classically causes a respiratory alkalosis by stimulating the respiratory centres in the brain followed by a metabolic acidosis by uncoupling oxidative phosphorylation.

Key clinical features:
Nausea and vomiting
Tinnitus
Fever
lethargy
tachypnoea (hyperventilation)
diaphoresis- excessive sweating
hyperthermia
Confusion
seizures
coma
agitation
Tachycardia

26
Q

What does aspirin overdose lead to on ABG?

A

Mixed resp alkalosis (due to hyperventilation) and raised anion gap metabolic acidosis (due to toxicity and acute renal failure)

27
Q

What organ is most affected by aspirin overdose?

A

Kidney- nephrotoxic

28
Q

What investigations are used to diagnose/ monitor aspirin overdose?

A
    • ABG (mixed resp alkalosis and metabolic acidosis)
  2. Salicylate levels- repeat every 2 hours until peak level
29
Q

How is aspirin overdose classified?

A

According to peak salicylate levels:
- Mild <300 mg/L
- Moderate 300-700 mg/L
- Severe >700 mg/L

30
Q

How is aspirin overdose managed?

A
  1. Activated charcoal: This is administered if the ingestion occurred less than 1 hour ago.
  2. Intravenous treatment: This involves the administration of IV fluids, sodium bicarbonate, and potassium chloride. The aim is to maintain good kidney function and alkalise the urine to increase salicylate excretion.
  3. Dialysis: This may be necessary if blood levels of aspirin are extremely high- if pulmonary oedema and severe metabolic acidosis
31
Q

What is TCA overdose?

A

Tricyclic antidepressants (TCAs) are a class of drugs that act as noradrenaline and serotonin re-uptake inhibitors, thereby increasing the levels of these neurotransmitters in the brain. They are commonly used to treat depression and other mood disorders. However, an overdose of these medications can be fatal, leading to severe symptoms such as drowsiness, coma, seizures, and cardiac dysrhythmias.

32
Q

What are the signs/ symptoms of a TCA overdose?

A
  • dry mouth and dry hot skin
  • dilated pupils
  • agitation
  • blurred vision
  • arrhythmias (prolonged QT interval and QRS widening)
  • convulsions
  • altered mental status
33
Q

What investigations are used to diagnose/ monitor TCA overdose?

A

ECG → wide QRS >100ms associated with seizures and >160ms with ventricular arrhythmias

34
Q

How is a TCA overdose managed?

A

Adminster IV Sodium Bicarbonate

  • Consider activated Charcoal within 2-4 hours of the overdose
  • Consider invasive ventilation
    Intravanous fluids

Perioperative med and anaesthesia Y3 (5 decks)

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