Perioperative arrythmias

First Thoughts

First Thoughts

* Can I feel a pulse?
* ?Immediately life threatening
* Is there a blood pressure?
* Is it stable or unstable?
* ?Regular or irregular
* ?Fast or ?slow

Narrow Complex Tachycardia

Narrow Complex Tachycardia

* What rhythm is it? (For AF see treatment slide for AF)
* Can you slow it down to see what it is? eg vagal manoeuvre, adenosine

Adenosine

Adenosine

* To terminate SVT, or, for other NCT’s transient AV block may help diagnosis
* Dose: 6 mg IV push, then 12mg if no response, further12mg if no response
* Adverse effects: bradyarrhythmias, flushing, chest pain which are Shortlived because t1/2 is just a few seconds
* Other drugs to use: beta blocker (BB), calcium channel blocker(CCB), digoxin

Atrial Fibrillation

Atrial Fibrillation

* Stable or unstable?? (If unstable consider DC cardioversion)
* >48 hours beware of CLOT: TOE, anti-coagulate before conversion
* Aims: RATE CONTROL or CONVERSION

  Rate Control Conversion
Good LV BB CCB Amiodarone SCV
Poor LV Digoxin Amiodarone SCV Amiodarone
WPW (Wolf Parkinson White) Amiodarone Sotalol  

*BB=beta-blocker, CCB=calcium channel blocker,SCV= synch cardiovert

Synchronized Cardioversion

Synchronized Cardioversion

* Sync mode delivers energy of the shock just after the R wave
Use of sync mode prevents delivering a shock during the T wave, which can trigger off VF eg use in AF,A Flutter, SVT
* Indications
all tachycardias rate > 150 bpm with serious signs and symptoms related to the tachycardia (may give a brief trial of medications if patient not severly unstable)
Note: low threshold for cardioversion if under GA

* Precautions
reactivation of sync mode is required after each attempted cardioversion (machines default to unsynchronized)
* Technique
look for sync markers on the R wave monophasic
shocks sequence is 100J, 200J, 300J, 360J (SVT and atrial flutter often respond to lower energy, start at 50 J)
Treat pulseless VT likeVF: ie unsynchronized monophasic 200, 200, 360, biphasic starts lower 150

Ventricular Tachycardia with a Pulse

Ventricular Tachycardia with a Pulse

Type of VT Good LV Poor LV
Mono Lignocaine
Amiodarone
Lignocaine
Amiodarone
Poly, normal QT BB
Lignocaine
Amiodarone
Lignocaine
Amiodarone
Poly, wide QT Mg, Lignocaine, Overdrive pace Lignocaine

Bradycardia

Bradycardia

* Treatment for symptomatic brady regardless of cause:
-stop vagal stimulation (what is the surgeon doing?)
-?pace or use drugs??
-first line drug atropine, 500 mcg repeated to total of 3 mg
-second line drug either isoprenaline (controversial) or adrenaline
* Unstable symptomatic patients: transcutaneous cardiac pacing (TCP), atropine +/- adrenaline, as temporary measure until transvenous pacing can be inserted
* Stable patients where there is a risk of asystole (eg pauses >3 sec or block at or below the AV node) may need to be paced.

Types of Bradycardia

Types of Bradycardia

* Sinus Bradycardia, First Degree Block and Second Degree Block-Mobitz Type 1(progressive P-R lengthening until QRS is dropped):
-these are rarely symptomatic
-these can be caused by excess vagal stimulation, especially if patient is on BB, digoxin, verapamil
* Sick Sinus Syndrome (Alternating brady and tachy)
-treatment with combination of permanent pacemaker (PPM) and anti-arrhythmics
* Second Degree Block-Mobitz Type 2 (P-R interval lengthened but fixed, with intermittent drop out of QRS)
-more worrying than Type 1. May progress to 3rd degree heart block (Complete Heart Block)
-causes: eg myocardial infarction, degeneration of conduction system
* Third Degree Block, Complete Heart Block
-this is total failure of AV conduction
-unstable rhythm, often severe bradycardia and can get episode of ventricular asystole
Causes: eg myocardial ischaemia or infarction, or chronic degeneration of conduction system
Treatment: permanent pacemaker PPM)

Emergency Pacing

Emergency Pacing

* Indications
-haemodynamically unstable bradycardia, especially if not responding to drug treatment
-bradycardia with pause dependent ventricular rhythm (risk of VT or VF)
-cardiac arrest secondary to reversible causes eg drug OD, acidosis, electrolyte disturbance
* Relative contra-indications
-beware of the prolonged brady-asystolic arrest >20 minutes (Is the patient already dead?)
-exclude hypothermia
Technique for Transcutaneous Pacing TCP
-modern defibrillators have TCP ability
-large diameter (8cm) electrodes
(anterior over cardiac apex to left of sternum, posterior on back to left of spine behind anterior electrode)
-start pacing, default rate usually 80 bpm. Select either demand or fixed rate.
-gradually increase output until capture (wide QRS and broad T wave after pacing spike) occurs. Pace at 10% above capture threshold

Causes of Arrhthymias- Is there a Treatable Cause?

Causes of Arrhthymias- Is there a Treatable Cause?

* Ischaemia Hypovolaemia
* Electrolyte disturbances
* Acid-base disturbances
* Hypo/hyperthermia
* Endocrine disturbance eg hyperthyroidism
* CVC/SwanGanz insertion
* Drugs-drug error, cocaine, amphetamines

LIGNOCAINE

LIGNOCAINE

* Indications
-cardiac arrest from VF/VT Class 2 b)
-stable VT, wide complex tachycardia of uncertain type, or wide complex SVT (Class 2 b)
* Precautions
-reduce maintenance dose (not loading dose)
in impaired liver function or left ventricular dysfunction
-discontinue infusion immediately if signs of toxicity develop
* Dose
-Initial dose: 1 to 1.5 mg/kg IV
-Can repeat 0.5 to 0.75 mg/kg every 5-10 minutes, max total dose 3mg/kg
-Maintenance Infusion: 1 to 4 mg/min (30 to 50 mcg/kg per minute)

AMIODARONE

AMIODARONE

* Indications
-treatment of shock refractory VF/pulseless VT
-treatment of polymorphic VT and wide complex tachycardia of uncertain origin
-control of haemodynamically stable VT when cardioversion unsuccessful (particularly useful in presence of LV dysfunction)
-used as adjunct to electrical cardioversion of SVT
-termination or rate control of atrial fibrillation/atrial flutter
* Precautions
-may produce vasodilation and hypotension
-may have some negative inotropic effects
>-use with caution in renal failure
* DOSE
-Cardiac arrest: 300mg IV push, consider repeating 150 mg IV push in 3 to 5 minutes (max cumulative dose 2.2g/24 hours)
-Other arrhythmias 5 mg/kg in 250 ml 5% dextrose over 20 minutes to 2 hours, then 10-15mg/kg over 24 hours

BETA BLOCKERS

BETA BLOCKERS
Indications
-to convert to normal sinus rhythm or to slow ventricular response ( or both) in supraventricular tachyarrhythmias eg SVT, atrial fibrillation, atrial flutter
-patients with suspected AMI and in unstable angina in absence of complications: are effective anti-anginal agents and can reduce incidence of VF

* Precautions
-concurrent admin of IV CCB eg verapamil can cause severe hypotensions
-contra-indicated severe LVF, hypoperfusion, 2nd or 3rd degree AV block, caution with bronchospastic disease
* DOSE
Esmolol- 0.5 mg/kgover 1 min, then infusion 0.05mg/kg/min(max 0.3 mg/kg/min)
Atenolol-eg 5 mg slow IV (over 5 minutes), wait 10 minutes then 2nd dose 5mg Slow IV

CALCIUM CHANNEL BLOCKERS

Verapamil

* Indications
-alternative drug to terminate SVT with narrow QRS complex, adequate blood pressure and preserved LV function
-may control ventricular response in patients with atrial fibrillation, flutter, or multi-focal atrial tachycardia
* Precautions
-do not use for wide QRS tachycardias
-avoid in WPW and atrial fibrillation, sick sinus, and 2nd and 3rd degree AV block without pacemaker
-expect blood pressure may drop due to peripheral vasodilation
-may exacerbate CCF in patients with LV dysfunction
-use with caution in presence of beta blockers
* Dose
2.5mg to 5mg IV bolus over 2-3 minutes. Second dose 5-10mg if needed in 15-30 minutes. Max dose 20mg

MAGNESIUM CHLORIDE

MAGNESIUM CHLORIDE

* Indications
-in cardiac arrest only if torsades de pointes or suspected hypomagnesaemia is present
-refractory VF (after lignocaine)
-torsades de pointes with a pulse
-life threatening ventricular arrhythmias due to digoxin toxicity

* Precautions
-blood pressure can fall with rapid administration
-caution if renal failure
* Dose
-cardiac arrest (with torsades or hypomagnesaemia) 1-2 mmol diluted to 10 mls and IV push
-torsades de pointes (not in cardiac arrest) 1-2 g mixed in 50-100ml of 5% dextrose, over 5-60 minutes IV. Follow with 0.5 to 1.0 g/hour