CPTP4.24

Question 1

Difference between paroxysmal and persistent AF?

Answer 1

Paryoxsmal self terminates!

Question 2

When is rhythm control preferred?

Answer 2

Reversible cause, HF mainly due to AF, new onset, clinical judgement

Question 3

Options for rate control?

Answer 3

First line is cardioselective B-blocker or rate-limiting CCB. Digoxin monotherapy can be used if sedentary. If B-blocker and CCB alone not enough, consider dual therapy with any two of: B-blocker, diltiazem, digoxin. If have LVF, give B-blocker and digoxin.

Question 4

Choice of B-blockers for AF?

Answer 4

Sotalol contraindicated (torsade); can use carvedilol, bisprolol, atenolol, metoprolol. All can be negative inotropes and chronotropes. Chronically get fatigue and cold extremities.

Question 5

CCBs in AF?

Answer 5

Non-DHP. L-type CCB. -ve inotropes and chronotropes. AEs include headache, constipation, ankle oedema, hypotension. Bad in HF.

Question 6

Digoxin in AF?

Answer 6

Less effective than other two. Consider in sedentary. Risk of toxicity in renal impairment. Acts by increasing vagal tone (reduces rate) but positively inotropic. Mostly renally eliminated and narrow Tw. Stops K+/Na+ antiporter. Means less Na+ outside of cell so less of a gradient to then remove calcium.

Question 7

Pill in the pocket for AF?

Answer 7

Use for paroxysmal. Must have no history of LVF/IHD/valve disease, infrequent symptomatic AF episodes, able to understand treatment.

Question 8

Cardioverting?

Answer 8

If unstable, do DC cardioversion regardless of anticoagulated. If <48 hours and stable, can do either. If choose pharma, then flecainide best in first 12 hours, then equal, but bad for structural heart disease. Amiodarone not good for thyroid disease. Both can cause hypotension and HF but amiodarone less so. If >48 hours, need three weeks anticoagulation then DC, then four weeks after. Can give rate control in the meantime. Also need echo for elective.

Question 9

Amiodarone?

Answer 9

Class III antiarrhythmic. Indicated for rhythm control. If going to do elective DC cardioverson, give before and after. Extensive tissue binding and has chronic adverse effects of photosensitivity, hepatotoxicity, pulmonary fibrosis, thyroid disease, hypotension, blue skin. Acutely (IV) can get thrombophlebitis.

Question 10

Warfarin?

Answer 10

Vit K reductase inhibitor. Affected by illness, NSAIDs and many drug interactions. Induced by alcohol (chronic), St Johns Wort, rifampicin, carbamazepine, phenytoin. Inhibited by macrolies, azoles, non-DHP CCBs, amiodarone, valproate. Takes 2-3 days to work because only acts on synthesis of new factors. Requires monitoring, hepatically excreted, need steady state and >50% in therapeutic range. 3% risk of bleeding per year. OD.

Question 11

NOACs?

Answer 11

Can be factor Xa inhibitors (rivaroxaban, epixaban) or direct thrombin inhibitors (dabigatran). Do not need INR monitoring but are expensive and antidotes are not widespread. GI side effects and GI bleeds, less ICH. Metabolism inhibited by amiodarone and verapamil.

Question 12

Managing paroxysmal AF?

Answer 12

Standard B-blocker, or pill-in-the-pocket.

Question 13

Reversing warfarin?

Answer 13

1. No bleeding, INR <8 = omit/reduce, consider PO vit K. If INR >8, give 1mg Vit K PO.
2. Bleeding. Minor = PO vit K. Significant, stable = IV vit K, consider FFP. Life/limb/site threatening, IV vit K AND beriplex.

Question 14

Epidemiology of poisoning?

Answer 14

Mostly affects children 1-5, or AYA (M=F).

Question 15

Poisons most likely to cause death?

Answer 15

Paracetamol, TCAs, opiates (!!!), carbon monoxide.

Question 16

Gastric lavage?

Answer 16

A gastric decontamination method. Suitable for very large and life-threatening overdoses, for poisons not absorbed by activated charcoal. Worse in children. Must protect airway with cuffed ET if drowsy. Complications include ASPIRATION, gut perforation, pneumothorax. Contraindications include hydrocarbons (very risky in lungs), caustic substances (damaged oesophagus).

Question 17

Activated charcoal?

Answer 17

A gastric decontamination method. Works if used early and at high dose (8:1). Adsorbs poison so reduces absorption. Can be given NG if unconscious but airway needs protecting. Complications are aspiration, reduced absorption of therapeutic agents, can form briquettes and obstruct bowel in large volumes (give laxative). Not effective for all poisons. Contra in absent bowel sounds, impaired gag reflex or unsafe swallow (charcoal dangerous in lungs).

Question 18

What substances is activated charcoal ineffective for?

Answer 18

Elemental metals/salts (lithium, iron), insecticides, cyanide, strong acids/alkalis, hydrocarbons.

Question 19

MDAC?

Answer 19

Means of increasing eliminiation (interferes with enterohepatic circulation and reduces concentration in bowel to pull poison back in. Give 50g then further 25g every two hours along with laxative. Good efficacy for carbamazepine, theophylline, salicylates, phenytoin. Cx = obstruction.

Question 20

Haemodialysis and haemoperfusion indications?

Answer 20

Useful when poison has small Vd (i.e. is in blood), low inherent clearance rate (so can be increased), very toxic, and is small enough to cross the membrane (haemodialysis) or bound to activated charcoal (haemoperfusion). Haemoperfusion rarely used. Haemodialysis can be used for salicyclates.

Question 21

Paracetamol OD?

Answer 21

1/2 of ODs include paracetamol. Normally metabolised to glucoronide or sylphate conjugates; saturable so get accumulation of toxic NAPQI, if glutathione absent get injury. NAC replaces glutathione. Early clinical features vague, KEY IS DELAYED (2-3 days) get jaundice, RUQ pain, encepahlopathy, coagulopathy, hepatic failure, death. Can get renal failure and met acidosis and hypoglycaemia. Poor prognostic features include metabolic acidosis, HE III/IV, raised lactate or creatinine.

Question 22

Treating paracetamol OD?

Answer 22

1. If over 8 hours, treat immediately, or if staggered. If less than 8, can wait for paracetamol level as treatment is very effective up until 8 hours; less effective after but still give at any time.
2. If in first hour, can give activated charcoal large dose.
3. Supportive; vit K, FFP, liver unit, RRT, OLT

Question 23

NAC Cx?

Answer 23

Anaphylactoid reaction (wheeze, hypotension, urticaria). Not true allergic reactions e.g. no IgE but mast cells degranulate. Reduce infusion rate, can give chlorphenamine. Steroids NOT INDICATED. Usually happens on first bag as infusion rate is highest. 15%.

Question 24

Salicyclate OD?

Answer 24

Dizziness, TINNITUS, agitation, vomiting, coma, hyperventilation. Get metabolic acidosis, respiratory alkalosis, hypoglycaemia and hypokalaemia.

1. Give 50g charcoal in an hour; can do lavage and charcoal if very large.
2. Bicarb prevents CNS penetration.
3. Enhanced elimination (bicarb [urinary alkalinisation]), MDAC).
4. Haemodialysis. Highly effective and corrects metabolic abnormalities. Consider if pH <7.3, salicyclates >700, renal failure.
5. Supportive, KCl.

Question 25

Opiate OD?

Answer 25

Methadone has long t1/2 so particularly difficult. Get CNS/resp depression, pinpoint pupils, hypotension and tachycardia, hallucinations, rhabdomyolysis, non-cardiac pulmonary oedema. Give naloxone; just aim to improve breathing or cause acute withdrawal/severe pain.

1. Naloxone indicated if RR <10 or GCS <10. Repeat as needed.
2. Short half life; watch for withdrawal etc. Can be very bad.

Question 26

TCA OD?

Answer 26

High fatality. Anticholinergic (hot, dry, tachycardia, mydriasis, retention, fits! Na+ blocking effects (arrhythmia, long QRS and QT). Alpha adrenoreceptor antagonism (hypotension). NEED ECG! BROAD QRS.

1. Charcoal in an hour.
2. MDAC may help.
3. Arrhythmias; more likely if low pH (<7.4) so give NaHCO3 (helps pH and Na+). Give for acidosis, wide QRS, arrhythmias. Correct K+. May need DC cardioversion. Do not use antiarrhythmics.
4. Fits; can cause hypoxia and arrhythmias so give diazepam or lorazepam.

Question 27

Fe poisoning?

Answer 27

Corrosive. Early = vague GI, bloody diarrhoea. Delayed = black offensive stools, drowsiness, coma, fits, circ. collapse. Late is acute liver necrosis and renal failure. Very late is gastric strictures. Must establish dose of elemental iron; do level after 4 hours then repeat after 2-3.

1. Gastric lavage if large (charcoal ineffective).
2. Desferrioxamine (chelates iron, chelate excreted in urine (red)). Can cause hypotension and pulmonary oedema, contraindicated in renal failure. Used in severe toxicity.
3. Supportive. Treat acidosis, fluids, fits, vomiting, RRT.

Question 28

Benzodiazepine OD?

Answer 28

Drowsiness, ataxia, dysarthria, nystagmus, resp depression. Potentiates other CNS depressants (alcohol, opiates). Quite low risk in isolation.

1. Activated charcoal generally not recommended; can be used in mixed overdose.
2. Can use flumazenil (competitive antagonist). Contraindicated if have taken substances that promotes seizures, have tachycardia, wide QRS i.e. anticholinergic signs, or history of seizures.
3. Benzos have large Vd so haemodialysis not very helpful.

Question 29

Organophosphate poisoning?

Answer 29

Absorbed through skin, bronchi, gut. Inhibit cholinesterase so prolongs ACh effect. Headache, bradycardia, muscle weakness, miosis, hypersalivation, coma, convulsions, hyperglycaemia and glycosyuria.

1. ABC, clear airway of secretions.
2. Can do lavage if airway protected.
3. Antidote; give atropine until skin flushed and drug, pupils dilate, brachycardia stopped.
4. Give pralidoxime as adjunct in moderate/severe.