Management of heart blocks and arrhythmias (intraoperatively)

 

Management of arrhythmias

 

                               Atrial Fibrillation

Immediate management

•         DC cardioversion if the patient is hemodynamically unstable (Rate Control)

 

•         Administer beta blocking drugs (esmolol 500 mcg/kg over1 minute, then 50 mcg/kg/min to a maximum of 300 mcg/kg/min)

 

•         Calcium channel blockers (diltiazem)• Amiodarone (150 mg IV over 10 minutes, then 1 mg/min IV for 6 hours, then 0.5 mg/min for 18 hours.) Be alert for hypotension when administering a bolus dose

 

•         Digoxin 0.125–0.25 mcg IV.

Sub sequent management

Rhythm Control

•         Cardioversion (electrical or chemical)

•         Amiodarone in resistant cases

•         Electrophysiology and cryoablation

•         Surgical ablation

Risk Control (Stroke)
Anticoagulation with heparin and warfarin

 

                                  Bradycardia

Immediate management

•          Remove possible causes. (E.g., during laparoscopic surgery, ask the surgeons to reduce intra-abdominal pressure.)
•          Initiate immediate transcutaneous pacing if there is evidence of tissue hypo perfusion.
•          Administer atropine while preparing for pacing (0.5 mg IV repeat every 5 minutes to a total dose of 3 mg).

Sub sequent management

•          Trans venous pacing if transcutaneous pacing fails to capture
•          Epinephrine (2–10 micrograms/min) or dopamine (2–10
•      micrograms/kg/min) infusion
•          Permanent pacemaker placement

 

               Narrow complex Tachycardia 

Immediate management

•        Administer adenosine (6 mg rapid IV push, repeat 12 mg × 2).
•          Stable regular narrow complex tachycardia: treat for underlying cause (fever, anemia, shock, sepsis, pain, etc.).
•          Stable, irregular, narrow complex tachycardia’s: control heartrate with diltiazem (15 mg IV over 20 minutes) or metoprolol (5 mg IV q 5 minutes).
•          Consider DC cardioversion if hemodynamically unstable.
•          Treat unstable arrhythmias with immediate electrical cardioversion.

 

Sub sequent management

•          If adenosine fails, initiate rate control with either intravenous calcium-channel blockers or beta-blockers.
•         Chemical cardioversion: Administer procainamide (50 mg/min IV, up to a dose of 18–20 mg/kg) or amiodarone (5 mg/kg IV over 15 minutes).
•         Use electrical cardioversion for tachycardia resistant to pharmacological interventions and/or in patients who are hemodynamically unstable

 

                  Wide complex Tachycardia 

Immediate management

•        DC cardioversion if hemodynamically unstable

Regular Rhythm

•          Amiodarone (150 mg IV given over 10 minutes, repeated as needed to a total of 2.2 g IV over the first 24 hours)

Irregular Rhythm

•         Procainamide (20 mg/min IV up to a total of 17 mg/kg)
•          Lidocaine (1 mg/kg IV, may repeat 0.5 mg/kg every 5 minutes as needed to total of 3 mg/kg)

Sub sequent management

•          Cardioversion for regular tachycardia resistant to pharmacological intervention, or if hemodynamically unstable.
•          If the patient has a history of a preexcitation syndrome (e.g., Wolff Parkinson-White syndrome), or evidence of preexcitation on the ECG (e.g., delta wave), procainamide is the preferred treatment (20 mg/min continuous infusion until the arrhythmia is suppressed, the patient is hypotensive, the QRS widens 50% beyond baseline, or a maximum dose of 17 mg/kg is administered)

 

                           Ventricular fibrillation

Immediate management

•          360 J* monophasic (200 J* biphasic) cardioversion—may repeat every 2 minutes if necessary (avoid delay—administer shocks before airway management)
•            Endotracheal intubation
•          CPR after shock to maintain 30:2 ratios for 2 minutes without pausing to check rhythm or pulse
•          Epinephrine 1 mg IV (repeat every 3–5 minutes) OR 40 U IV vasopressin (one-time dose)

Sub sequent management

•          Airway management
•          ACLS secondary survey
•          Amiodarone 300 mg IV (repeat 150 mg in 3–5 minutes if VF/PVT persists)
•          Lidocaine (if amiodarone unavailable) 1.0–1.5 mg/kg IV, may repeat to a 3 mg/kg max. loading dose
•          Magnesium sulfate1–2 g IV diluted in 10 mL 5% dextrose in water for torsades de pointes or suspected/ known hypomagnesemia.

 

INTRA-OPERATIVE ARRHYTHMIAS AlGORITHM

Management of heart blocks

Preoperative assessment

The following questions must be answered:

•          What is the rhythm disturbance and what compromise results from it?
•          Is the cardiac anatomy normal?
•          If the anatomy is not normal, is there any history of progression of heart failure, cyanosis or chronic pulmonary disease?
•          What is the ventricular performance?
•          Are there are any implanted devices?  
•          What is the anti-coagulation status?
•          Are serum electrolyte concentrations (especially potassium and magnesium) within acceptable ranges?
•          What procedure is intended?

Effect of anesthetic agents on cardiac conduction:

•          The interaction of both intravenous and volatile anesthetic agents with the cardiac conduction system is complex and incompletely understood, in terms of both the effects themselves and the clinical significance of such effects.
  
  
•         In isolated heart preparations, thiopental has been shown to significantly prolong the atrial refractory period in a concentration-dependent manner
  
  
•          propofol and ketamine have no effect on atrial refractoriness.
  
  
•          However, ketamine causes a dose-dependent decrease in atrial conduction velocity, not seen with propofol and thiopental.
  
  
•          All three drugs produce a concentration-dependent decrease in A-V node conduction and an increase in A-V node effective refractory period, with propofol being more potent in this regard than the other two agents.
  
  
•          Opioids, when used in combination with a benzodiazepine (e.g. alfentanil midazolam or sufentanil  lorazepam) have no significant effect on either the normal cardiac conduction tissue or accessory pathways found in Wolff-Parkinson-White syndrome.
  
  
•         Desflurane at 2 MAC shortens atrial AP duration and the effective atrial refractory period.
  
  
•          Isoflurane prolongs the atrial refractory period and delays ventricular repolarization.

Management

•         In general, patients that present with first-degree or second-degree Mobitz type 1 AV block do not require treatment. Any provoking medications can be removed, and patients can be monitored on an outpatient basis.

•         However, patients with higher degrees of AV block (Mobitz type 2 AV block, 3rd degree) tend to have severe damage to the conduction system. They are usually at a much greater risk of progressing into asystole, ventricular tachycardia, or sudden cardiac death. Hence, they require urgent admission for cardiac monitoring, further evaluation, consideration of a backup temporary cardiac pacing on a case-to-case basis, and eventually the insertion of a permanent pacemaker.

•         There is modest evidence and strong clinical consensus that patients with persistent second or third-degree AV block must receive permanent cardiac pacing therapy. The evidence is modest and the consensus is weak for patients who have persistent bifascicular block (with or without underlying first degree AV block) associated with transient AV block or with prolongation of PR interval.

•         Use of an urgent or emergent temporary transvenous pacemaker should not be a "knee jerk" reaction to the presence of a second-degree, high grade or third-degree AV block. It should be considered after a careful evaluation of the risk-benefit ratio in clinical settings, consideration of hemodynamic stability (as gauged by the evaluation of systolic blood pressure and the degree and duration of patient's clinical symptoms), level of AV block and presence of the type of escape rhythm. 

•         Complications are very common in patients treated with placement of a temporary transvenous pacemaker. The complications are not just related to the implant itself but also related to the care post-implant including the change of position of the lead, change of capture threshold, pacer malfunction, faulty programming and/or battery depletion of the pacer box.

•         Complications may also be related to accidental extraction of the lead by the patient. The use of a temporary pacer should be kept to the shortest duration possible in order to avoid patients' risk of immobility, infection, thromboembolism and risk of cardiac perforation. The potential complications must be kept in mind as sometimes the risk-benefit ratio may significantly outweigh justifying its potential use. 

•         European Task force guidelines and other expert consensus usually strongly leans towards the fact that temporary transvenous pacing should be avoided as far as possible and the treatment time should be kept as brief as possible.