Cardiac arrhythmia

1
Cardiac arrhythmia

• Primary
• quinidinelike drugs, sympathomimetic drugs,
  calcium channel blockers, ßblockers, digitalis,
  chloroquine
• Secondary to metabolic/electrolyte abnormalities
• salicylates, methanol, ethylene glycol

2
Cardiotoxic drugs

• All patients should have
• oxygenation and protection of airway
• decontamination of the GIT
• atropine premedication
• correction of electrolyte abnormalities
• acid base balance
• cardioversion when appropriate
• consultation

3
Cardiac arrest

• Successful resuscitation has been well documented
  after 8 hours of CPR
• Overdose patients usually have
• a reversible cause for their arrest
• good general health
• novel treatments for arrhythmias
• cerebral protection

4
Antidotes asystole bradycardia

• Atropine everything
• Bicarbonate tricyclic antidepressants
• Calcium calcium channel blockers
• Diazepam chloroquine, organochlorines
• Epinephrine everything, ßblockers
• Fab fragments digoxin
• Glucagon ßblockers, CCBs

5
Cardiac case 1

• 18 yo female admitted 3 hours after
  selfpoisoning with
• 3.5 g of slow release verapamil (Isoptin SR)
• 6 g of paracetamol
• 4.5 g of tetracycline
• 1 g of pseudoephedrine
• On arrival in casualty
• pr 120, BP 110/80, RR 20, afebrile
• drowsy but oriented and cooperative

6
Cardiac case 1

• GI decontamination
• emesis before arrival
• lavaged with return of green tablets
• 50 g of charcoal with sorbitol repeated 4 h later
• Investigations
• ECG
• sinus tachycardia with normal QRS width
• serum paracetamol at 4 h was 38 µmol/l
• hepatotoxicity gt 1300 µmol/l at 4 hours

7
Cardiac case 1

• In intensive care unit
• 16 hours post overdose
• BP fell to 70/40 and then 50/30
• PR 50
• oxygen saturation dropped to 75
• ECG
• absent p waves
• prominent u waves
• normal QRS duration and QT interval

8
Cardiac case 1

• Treatment
• IV atropine 0.6 mgs no response
• IV calcium gluconate
• 6 g over 20 minutes
• further 6 g over the next hour
• pr 60, sinus rhythm, BP 100/80
• oxygen saturation gt 95
• infusion of 10 calcium gluconate at 2 G/h for 10
  hours
• she was also given 2.5 L IV fluids

9
Cardiac case 1

• Outcome
• noncardiogenic pulmonary oedema
• twenty four hours post admission
• largely recovered , sinus rhythm PR 60, BP 115/70
• peak serum Ca was 4.8 (2.182.47 mmol/l)
• serial verapamil levels at 6, 18, 22 and 46 hours
  were 616, 2374, 2518 and 1006 ng/ml
• range during usual therapy
• 100300 ng/ml

10
Cardiac case 2

• 38 yo female admitted after selfpoisoning with
• amitriptyline 2525 mg
• dothiepin 1650 mg
• Found unconscious with suicide note carefully
  documenting tablets
• last seen 9 a.m., brought in by ambulance at 6
  p.m.
• later said she had read that 2.5 g was a lethal
  dose

11
Cardiac case 2

• No past medical history
• Depressed for several months, treated by a
  psychiatrist
• On examination
• absent gag
• unconscious, flexes to pain
• PR 40, BP 130/100, afebrile
• hypoventilating, 02 saturation 94
• flushed, dilated pupils, reduced bowel sounds

12
Cardiac case 2

• Investigations
• FBC
• EUC
• paracetamol level
• ECG
• CXR ? aspiration
• GI decontamination
• gastric lavage and activated charcoal

13
Cardiac case 2

• Treatment and outcome
• given NaHC03 IV
• intubated and hyperventilated
• IV normal saline
• ABGs monitored to keep pH 7.5
• serial ECGs
• prolonged unconsciousness
• extubated 40 hours later
• no long term sequelae

14
Cardiac case 3

• 26 yo female
• found unconscious by police in caravan
• empty bottle of tablets with label removed
• no relatives/other history available
• On examination
• PR 140, BP 120/80, afebrile
• unconscious
• GCS 6

15
Cardiac case 3

• Investigations
• ECG
• QRS width 120 ms
• PR interval 200 ms
• CXR
• aspiration pneumonia
• Management
• intubated, lavage, charcoal, antibiotics

16
Cardiac case 3

• Outcome
• sudden deterioration 2 hours later
• bradycardia
• asystole
• unable to be resuscitated

17
Tricyclic antidepressants

• Ingestion of 1520 mg/kg is potentially fatal
• Mechanism of action
• block reuptake of noradrenaline and serotonin
• competitive antagonists at H1 and H2 receptors
• anticholinergic effects
• membrane effects on sodium channel,
  quinidinelike effect

18
Toxicokinetics

• Absorption and distribution
• highly lipid soluble
• rapidly absorbed
• high volume of distribution
• delayed absorption due to anticholinergic effect
  in GIT
• pH dependent protein binding gt 95
• large variation in amount of free TCA
• a change in the pH from 7.38 to 7.50 produces a
  21 reduction in free TCA

19
TCA management

• General
• supportive care, ABG, ECG, electrolytes
• lavage, charcoal with sorbitol/mannitol
• CNS toxicity
• seizures
• IV diazepam
• IV phenytoin (1518 mg/kg)
• anticholinergic delirium
• benzodiazepines, haloperidol
• seizure and fever consider physostigmine

20
TCA management

• Arrhythmias
• plasma alkalinisation to pH 7.5
• sodium bicarbonate, hyperventilation
• drug treatment
• acute
• magnesium
• sotalol
• lignocaine
• prophylactic
• phenytoin
• overdrive pacing

21
TCA management

• hypotension
• volume expansion
• pH correction
• alpha agonists e.g. noradrenaline
• inotropics e.g. dopamine, dobutamine