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Yr 4 - ACC > Overdoses > Flashcards

Overdoses Flashcards

1
Q

What are tricyclic antidepressants (TCAs)?

A

A class of medications developed initially for severe depression.

Now more used to manage neuropathic pain and for migraine prophylaxis.

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2
Q

Give 3 examples of TCAs

A

1) amitriptyline

2) nortriptyline

3) dosulepin

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3
Q

What are the 2 most common drugs most commonly taken in fatal overdose?

A

1) analgesic drugs (most common)

2) TCAs: highly toxic in overdose.

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4
Q

What are the 2 main mechanisms of action of TCAs?

A

1) Reuptake inhibition (more neurotransmitter remains in synaptic cleft) i.e. INCREASED effect

2) Postsynaptic receptor antagonism: prevents the neurotransmitter from activating the postsynaptic receptor, overall reducing its effect i.e. DECREASED effect

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5
Q

What 2 neurotransmitters do TCAs have an INCREASED effect on (i.e. via reuptake inhibition)?

A

1) serotonin (5-HT receptors)

2) Noradrenaline (NA receptors)

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6
Q

What 2 neurotransmitters do TCAs have a DECREASED effect on (i.e. via postsynaptic receptor antagonism)?

A

1) histamine (H1 receptors)

2) A-1 adrenoreceptors

3) Acetylcholine receptors

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7
Q

What is the key mechanism by which TCAs achieve their antidepressant effect?

A

Inhibiting the reuptake of serotonin and noradrenaline.

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8
Q

What causes increased side effects and toxicity in overdose of TCAs?

A

The lack of specificity and effects on other pathways results in an extensive side effect profile

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9
Q

List of side effects of TCAs due to each pathway:

A

Serotonin: nausea, GI upset, sexual dysfunction

Noradrenaline: tachycardia, tremors

Histamine: sedation, weight gain

Anticholinergic: dry mouth, blurred vision, confusion, constipation, tachycardia, urinary retention

Alpha-1 adrenergic: postural hypotension, drowsiness, dizziness

TCAs also act on the fast sodium channels in myocardial cells, resulting in sodium channel blockade and risk of cardiac arrhythmias, convulsions, and coma in overdose.

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10
Q

When do the clinical manifestations of TCA overdose typically appear?

A

within 6 hours of ingestion

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11
Q

Which 2 TCAs are particularly dangerous in overdose?

A

1) amitriptyline
2) dosulepin (dothiepin)

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12
Q

What are the key clinical features of TCA overdose?

A

Signs of anticholinergic toxicity:
- dry mouth
- dilated pupils
- tachycardia
- blurred vision
- agitation

Signs of sodium channel blockade:
- arrhythmias
- CVS collapse
- convulsions
- metabolic acidosis
- coma

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13
Q

What ECG changes may be seen in TCA overdose?

A

1) sinus tachycardia
2) widening of QRS
3) prolongation of QT interval

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14
Q

What are the complications of widening of QRS?

A

1) Widening of QRS > 100ms: associated with an increased risk of seizures

2) Widening of QRS > 160ms: associated with ventricular arrhythmias

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15
Q

How may TCA overdose affect breathing?

A

In patients presenting with severe toxicity, respiratory depression may occur resulting in reduced respiratory rate and reduced SpO2.

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16
Q

How may TCA overdose affect circulation?

A

1) TCAs cause myocardial sodium channel blockade: hypotension & arrhythmia

2) Serotonergic activity: tachycardia and peripheral vasodilation may occur

3) ECG findings: widened QRS, prolonged QTc (predispose to ventricular tachycardia and ventricular fibrillation)

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17
Q

What is serotonin syndrome?

A

A potentially life-threatening presentation precipitated by the overactivation of both central and peripheral serotonin receptors.

Caused by using serotonergic drugs e.g. TCAs, SSRIs, opioids, MAOIs.

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18
Q

What are the 3 hallmark features of serotonin syndrome?

A

1) altered mental state
2) neuromuscular hyperactivity
3) autonomic hyperactivity

This results in:
- HTN
- tachycardia
- sweating
- myoclonus
- hyperreflexia
- severe: hyperthermia, muscle rigidity

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19
Q

Bedside investigations in TCA overdose?

A

1) Vital signs (as part of ABCDE): tachycardia, hypotension, hyperthermia

2) ECG: widened QRS, prolonged QTc

3) Blood glucose: exclude hypoglycaemia

4) Blood gas: mixed acidosis

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20
Q

Lab investigations in TCA overdose?

A

1) FBC: baseline

2) U&Es:
- hypokalaemia common
- patients with renal impairment more at risk as TCAs renally excreted

3) Magnesium & bone profile: electrolyte disturbances can worsen arrhythmia and require correction

4) LFTs

5) Paracetamol & salicylate levels: typically checked in all patients presenting with overdose, particularly where the history is unclear

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21
Q

How is potassium level affected by TCA overdose?

A

Hypokalaemia: risk of seizures or cardiac arrhythmias

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22
Q

How are TCAs excreted?

A

Renally

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23
Q

What imaging may be relevant in TCA overdose?

A

1) CXR: useful in the assessment of patients who are presenting with reduced conscious level and airway compromise, where there is a risk of aspiration pneumonia

2) CT head: considered in patients with significantly reduced GCS to rule out concurrent intracranial pathology.

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24
Q

Acute management of TCA overdose?

A

There is no specific antidote to TCAs, therefore management is supportive.

1) ABCDE

2) Can give activated charcoal to conscious patient –> prevent absorption if they present within one hour of ingestion

3) Sodium bicarb: given in arrhythmia and acidosis to prevent progression to ventricular arrhythmias.

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25
Q

When can activated charcoal be given in TCA overdose?

A

If they present within 1 hour of ingestion

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26
Q

1st line medical management of hypotension or arrhythmias in TCA overdose?

A

IV bicarb

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27
Q

Indications for IV bicarb in TCA overdose?

A

ECG changes of:
- widening of QRS >100 msec
- ventricular arrhythmia

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28
Q

Why is Flecainide contraindicated in TCA overdose?

A

As it prolongs depolarisation

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29
Q

Why is amiodarone contraindicated in TCA overdose?

A

It prolongs QT interval

30
Q

What are salicylates?

A

A group of medications of which aspirin (acetylsalicylic acid) is the most common.

NSAIDs (both oral and topical) also contain salicylates.

31
Q

What is the most common salicylate?

A

Aspirin

32
Q

Is accidental overdose of TCAs or salicylates more common?

A

Salicylates: due to widespread use, accidental ingestion of more than the recommended dose is common.

33
Q

Clinical features of MILD salicylate overdose?

A

Irritates gastric lining:
- epigastric pain
- N&V

Ototoxicity:
- tinnitus
- dizziness

Lethargy

34
Q

Clinical features of MODERATE salicylate overdose?

A
  • sweating
  • fever
  • dyspnoea
35
Q

Clinical features of SEVERE salicylate overdose?

A
  • confusion
  • convulsions
  • coma
36
Q

How does salicylate overdose affect blood gas?

A

Higher doses –> Mixed respiratory alkalosis & metabolic acidosis.

37
Q

What causes respiratory alkalosis in salicylate overdose?

A

salicylates stimulate the cerebral medulla, leading to hyperventilation and respiratory alkalosis.

38
Q

What causes metabolic acidosis in salicylate overdose?

A

Metabolisation of salicylates causes uncoupling of oxidative phosphorylation, resulting in anaerobic metabolism.

This causes heat production and pyrexia and increased lactic acid production, resulting in metabolic acidosis.

39
Q

Clinical findings in moderate/severe toxicity in salicylate overdose?

A
  • warm peripheries & bounding pulse
  • tachypnoea & hyperventilation
  • cardiac arrhythmia
  • acute pulmonary oedema
40
Q

Bedside investigations in salicylate overdose?

A

1) Obs

2) ECG: monitor for arrhythmias

3) Glucose: exclude hypoglycaemia or ketoacidosis

4) ABG: monitor acid-base balance
- Initially, hyperventilation causes respiratory alkalosis, but this will then progress to metabolic acidosis with a partial respiratory compensation, with a normal or high pH.

41
Q

Lab investigations in salicylate overdose?

A

1) plasma salicylate conc: taken at least 2 hours after ingestion and repeated every 2 hours until salicylate concentration peaks.

2) plasma paracetamol conc

3) FBC

4) U&Es: hyprkalaemia is common, may cause AKI

5) LFTs

6) Coagulation

42
Q

Management of salicylate overdose?

A

1) ABCDE

2) Supportive care (consider ICU admission)

3) Activated charcoal: if presenting within 1 hour of ingestion

4) Fluids

5) Urinary alkalinisation with IV sodium bicarbonate - enhances elimination of aspirin in the urine

6) haemodialysis

43
Q

Purpose of IV sodium bicarb in salicylate overdose?

A

enhances elimination of aspirin in the urine

44
Q

How does salicylate overdose affect body temp?

A

Hyperthermia

45
Q

Clinical features of ecstasy poisoning?

A

1) Neuro: agitation, anxiety, confusion, ataxia

2) Cardio: tachycardia, HTN

3) Hyponatraemia

4) Hyperthermia

5) Rhabdomyolysis

46
Q

What can cause hyponatraemia in ecstasy poisoning?

A

either SIADH or excessive water consumption whilst taking MDMA

47
Q

Management of ecstasy poisoning?

A

1) supportive

2) dantrolene may be used for hyperthermia if simple measures fail

48
Q

What may be used for hyperthermia in ecstasy poisoning?

A

dantrolene

49
Q

Give some examples of amphetamines

A
  • adderall
  • methylphenidate (Ritalin)
  • cocaine
  • MDMA
50
Q

Give some drugs that can cause serotonin syndrome

A

1) monoamine oxidase inhibitors

2) SSRIs

3) ectasy

4) amphetamines

51
Q

What are 2 key drugs that can interact with SSRIs are cause serotonin syndrome?

A

1) St John’s Wort: often taken over the counter for depression

2) Tramadol

52
Q

Management of serotonin syndrome?

A

1) supportive including IV fluids

2) benzos

3) more severe cases are managed using serotonin antagonists such as cyproheptadine and chlorpromazine

53
Q

What are some features of opioid misuse?

A
  • rhinorrhoea & watering eyes
  • needle track marks
  • pinpoint pupils
  • drowsiness
  • yawning
54
Q

What are some complications of opioid misuse?

A

1) viral infection 2ary to needle sharing e.g. Hep B&C, HIV

2) bacterial infection 2ary to injection e.g. infective endocarditis, septic arthritis, septicaemia, necrotising fasciitis

3) VTE

4) overdose may lead to respiratory depression & death

5) psychological problems: craving

6) social problems: crime, prostitution, homelessness

55
Q

Emergency management of opioid overdose?

A

IV or IM naloxone –> has a rapid onset and relatively short duration of action

56
Q

Harm reduction interventions in opioid misuse?

A

1) needle exchange

2) offer testing for HIV, hep B&C

57
Q

1st line for treatment in opioid detoxification?

A

1) methadone

OR

2) buprenorphine

58
Q

What type of respiratory failure does opioid overdose cause?

A

Type 2 respiratory failure

59
Q

What is the key investigation in opioid overdose?

A

ABG –> to assess the degree of type 2 respiratory failure 2ary to respiratory depression.

(also always get a blood glucose)

60
Q

Mechanism of benzos?

A

Enhance the effect of GABA, resulting in sedative, anxiolytic, anticonvulsant and muscle relaxant effects.

61
Q

Clinical features of benzos overdose?

A

1) Reduced level of consciousness (including coma): if severe this can result in loss of airway tone and reflexes leading to hypoxia if left untreated.

2) Respiratory depression: decreased respiratory rate can result in hypoxia and inadequate tissue perfusion.

3) Hypotension

4) Bradycardia

5) Rhabdomyolysis

6) Hypothermia

62
Q

What ABG finding is typically seen in benzo overdose?

A

Type 2 respiratory failure due to respiratory depression

63
Q

Management of benzo overdose?

A

1) ?airway

2) oxygen

3) IV fluids for hypotension

4) flumenazil

64
Q

How does a benzo overdose affect the pupils?

A

Dilated pupils

65
Q

What drug is used in the the medical management of a benzo overdose?

A

Flumenazil

66
Q

What is flumenazil?

A

GABA receptor antagonist

67
Q

When should flumenazil be used in a benzo overdose?

A

Only when:

1) CNS depression is severe enough that patients are requiring ventilation

2) You are confident that only benzodiazepines have been taken (e.g. no possibility of a mixed overdose)

3) The patient is not known to be benzodiazepine dependent

Use outside of these conditions risks precipitating seizures (e.g. if a patient has also taken TCAs) which are particularly difficult to treat due to the GABA antagonism caused by Flumazenil.

68
Q

How does a benzo overdose typically affect body temp?

A

typically associated with hypothermia

69
Q

How does an amphetamine overdose typically affect body temp?

A

typically associated with hyperthermia

70
Q
A

Yr 4 - ACC (73 decks)

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