Anaesthesia for patient with pacemaker

A patient with pacemaker presents a complex challenge to the attending anaesthesiologist. The mode of management will be according to the type of pacemaker implanted. This presentation discusses in brief the peri-operative consideration in a patient with pacemaker.

1. ANAESTHESIA FOR PATIENT WITH PACEMAKER DR HASSAN

2. OVERVIEW :- 1958 : 1 st Battery operated pacing devices. 1980: Implantable Cardioverter defibrillator ( ICDs ). Today: > 3, 000 pacemaker models, produced by 26 companies. USA data: > 250,000 adults & children are undergoing Cardiac Rhythm Management Device (CRMD) implantation annually.(Global ~ 5 million)

3. WHAT IS A PACEMAKER? A PACEMAKER (OR ARTIFICIAL PACEMAKER) IS A MEDICAL DEVICE WHICH GENERATES ELECTRICAL IMPULSES AND DELIVERS BY ELECTRODES CONTRACTING THE HEART MUSCLES , TO REGULATE THE BEATING OF THE HEART.

4. PARTS OF PACEMAKER Pulse Generator : power source or battery. ( Zinc,Lithium Iodide) Leads Or Wire : deliver electrical impulse. Cathode : (-) electrode. Anode : (+) electrode.

5. TYPES TEMPORARY PACEMAKERS. IMPLANTABLE CARDIOVERTER DEFIBRILLATOR (ICDS). PERMENANT PACEMAKERS.

6. TEMPORARY PACEMAKERS External, battery-powered, pulse generators with exteriorized electrodes produce e lectrical cardiac stimulation to treat a bradyarrhythmia or tachyarrhythmia until it resolves or until long-term therapy can be initiated. Used for less than three days .

7. - TRANSVENOUS -TRANSCUTANEOUS -EPICARDIAL Transvenous pacing ( Invasive) Epicardial pacing ( Invasive) Transcutaneous pacing ( Non Invasive) 4. Esophageal

8. IMPLANTABLE CARDIOVERTER D EFIBRILLATOR ( ICD) S pecialized device designed for tachyarrhythmia detection and therapy . Functions :- Antitachycardia and antibradycardia pacing , Synchronized ( Cardioversion ) shock. Non synchronized ( Defibrillation ) shock . Telemetry. Diagnostics .

9. INDICATION:- initial therapy in survivors of cardiac arrest due to VF/VT. Syncope with hemodynamically unstable sustained VT/ VF.

10. PERMANENT PACEMAKER Implantable pulse generators with endocardial or myocardial electrodes for long- term or permanent use.

11. PERMANENT PACEMAKER INDICATIONS:- Symptomatic diseases of impulse formation ( S A Node Disease ) . Symptomatic diseases of impulse conduction ( AV Node Disease ) . Hypertrophic Obstructive C ardiomyopathy (HOCM ). Dilated Cardiomyopathy (DCM). Long Q T Syndrome. Bryce et al, Ann Intern Med. 2001; 134:1130-41.

12. GENERIC CODE FOR PACEMAKER NASPE/BPEG (North American Society Of Pacing And Electrophysiology/ British Pacing And Electrophysiology Group) Alliance

13. IMPORTANT TERMS REGARDING PACEMAKERS. Pacing Sensing Pacing Threshold Capture Rate Response Triggered Pacing Inhibition Of Output Pacing Modes

14. Pacing :-regular output of electrical current, for the purpose of depolarizing the cardiac tissue in the immediate vicinity of the lead, with resulting propagation of a wave of depolarization throughout that chamber. Sensing :- response of a pacemaker to intrinsic heartbeats .

15. 3. Pacing Threshold :- The threshold is the minimum amount of energy the pacemaker sends down the lead to initiate a heart beat. 4. Capture :- Cardiac depolarization and resultant contraction ( atrial or ventricular) - Caused by pacemaker stimulus. 5. Rate response :- it have various sensors that will active while patient during activities and adjust the rate .

16. 6. Triggered pacing :- Dual chamber pacemakers can be programmed to sense activity in one chamber (usually the atrium) and deliver a pacing stimulus in the other chamber (usually the ventricle) after a certain time delay. 7. Inhibition of Output :-pacemaker can be programmed to inhibit pacing if it senses intrinsic activity, or it can be programmed to ignore intrinsic activity and deliver a pacing stimulus anyway.

17. MODES OF PACING Asynchronous Pacing.( eg . AOO,VOO,DOO) Single Chamber Demand Pacing. ( eg . AAI,VVI) Dual Chamber AV Sequential Demand Pacing.( eg . DDD 70 with AV interval 200msec)

18. PROGRAMMABLE PACEMAKER Recent generation pacemakers provide flexibility to device to patients changing metabolic needs . Capacity to noninvasively alter one of several aspects of the function of a pacer . Sensors capable of detecting body movements, changes in ventricular repolarisation , central venous temprature , respiratory rate and depth and right ventricular contractibility.

19. PROGRAMMABLE FACTORS :- Pacing rate. Pulse Duration. Voltage output. Refractory periods. PR Interval. Mode of pacing. Hysteresis.

20. BIVENTRICULAR PACEMAKER/CRS (CARDIAC RESYNCHRONISATION THERAPY) A pacemaker that paces both the septal and lateral wall of left ventricle simultaneously. This resynchronizes a heart to contract in full synchrony. Leads in right and left ventricle and right atrium .

21. INDICATION:- patients with dilated cardiomyopathy with LVEF <35% NYHA III/IV despite maximal medical therapy(CHF)

22. Preoperative Evaluation Evaluation Of The Patient:- Underlying cardiovascular disease responsible for pacemaker implantation. Any other associated illness e.g CAD, HTN, DM etc. Severity of the cardiac disease. Current functional status. Medication status of the patient.

23. PACEMAKER EVALUATION :- Type of pacemaker (fixed rate or demand rate). Conduct a focused physical examination (check for scars and palpate for device). Half-life of the pacemaker battery. Effect of the Magnet Application on Pacemaker Function. Time since implantation. Pacemaker rate at the time of implantation.

24. INVESTIGATIONS :- Routine investigation:- CBC,RFT Biochemistry serum electrolytes (s. K +, S.Na + ) CXR, ( continuity of leads ) ECG, ( Spike )

25. PREOPERATIVE PREPARATION Determine whether EMI is likely to occur during the planned procedure. If interference is likely, reprogram CRMD and suspend anti tachyarrhythmia function . Determine pacemaker baseline rate and rhythm. Correct any underlying electrolyte abnormality ( if present)

26. CHOICE OF ANAESTHESIA Technique may not influence directly but physiological changes (acid-base, electrolytes) & hemodynamic shifts ( heart rate, rhythm, hypertension, coronary ischemia) can change CIED function & adversely effect patient outcome.

27. ANAESTHETIC TECHNIQUE Narcotic and inhalational techniques can be used successfully. In a patient with newly implanted pacemaker, nitrous oxide is avoided – expansion of gas in pacemaker pocket. Etomidate and ketamine should be avoided as these cause myoclonic movements . Pacemaker function should be verified before and after initiating mechanical ventilation as Positive Pressure Ventilation can dislodge pacemaker leads.

28. Skeletal myopotentials , electroconvulsive therapy, succinylcholine fasciculation, myoclonic movements, or direct muscle stimulation can inappropriately inhibit or trigger stimulation , depending on the programmed pacing modes. Care should be taken during insertion of guide wire or central venous catheter as they are arrhythmogenic and can dislodge pacemaker leads.

29. MONITORING Based on the patient’s underlying disease and the type of surgery. Continuous ECG monitoring (artifact filter disabled). NIBP, ETCO 2 and peripheral temperature monitoring . Both electrical and mechanical evidence of the heart function should be monitored by manual palpation of the pulse, pulse oximetry , precordial stethoscope and arterial line.

30. FACTORS AFFECTING PACING THRESHOLDS Increase 1-4 weeks after implantation Myocardial ischaemia / infaction Hypothermia, hypothyroidism Hyperkalaemia acidosis/alkalosis Antiarrythmics Severe hypoxia/ hypoglycaemia Inhalation-local anaesthetics Decrease Increased catecholamines Stress, anxiety Sympathomimetic drugs - Anticholinergics Glucocorticoides Hyperthyroidism Hypermetabolic status

31. EFFECT OF EMI (Electromagnetic Interference) ON PACEMAKER Inhibition of pacing. Asynchronous pacing. Reset to back up mode. Myocardial burn.(rare) Ventricular fibrillation.(rare)

32. Measures To Decrease Possibility Of Adverse Effects Due To EMI Bipolar cautery or ultrasonic (harmonic) scalpel in place of a monopolar cautery , if possible. Unipolar cautery (grounding plate should be placed close to the operative site and as far away as possible from the site of pacemaker) Electrocautery should not be used within 15cm of pacemaker . Pacemaker may be programmed to asynchronous mode by a magnet or by a programmer.

33. Provision of alternate temporary pacing. Drugs ( isoproterenol and atropine) should be available. Careful monitoring of pulse, pulse oximetry and arterial pressure is necessary during electrocautery , as ECG monitoring can also be affected by interference. The device should always be rechecked after operation.

34. MAGNET APPLICATION ON PACEMAKER FUNCTION The magnet is placed over the pulse generator to trigger the reed switch present in the pulse generator resulting in a non-sensing asynchronous mode with a fixed pacing rate ( magnet rate ). It shuts down the demand function so that the pacemaker stimulates asynchronous pacing . Thus, it protects the pacemaker dependent patient during EMI, such as diathermy or electrocautery .

35. The response varies with the model and the manufacturer so advisable to consult the manufacturer to know the magnet response before use. Demonstrates remaining battery life and sometimes pacing thresholds. Complications- ventricular asynchrony, altered programming.

36. EMERGENCY DEFIBRILLATION OR CARDIOVERSION In a patient with ICD and magnet-disabled therapies , Before attempting emergency defibrillation or cardioversion :- -All sources of EMI should be terminated. -Remove the magnet to reenable antitachycardia therapies. Patient with ICD and antiarrhythmic therapies that have been disabled by programming , consider re enabling therapies through programming. If it fail to restore ICD function, proceed with emergency external defibrillation or cardioversion .

37. Follow ACLS guidelines for energy level and for paddle placement. If possible , attempt to minimize the current flowing through the pulse generator and lead system by positioning the pads or paddles :- -as far as possible from the pulse generator. -perpendicular to the major axis of the CIED pulse generator and leads to the extent possible by placing them in an anterior-posterior location.

38. Specific Perioperative Considerations Transuretheral Resection of Prostate (TURP) and Uterine Hysteroscopy. Electroconvulsive Therapy . Radiation . Nerve Stimulator Testing or Transcutaneous Electronic Nerve Stimulator Unit . (TENS) Lithotripsy . Magnetic Resonance Imaging ( MRI ) .

39. Postoperative Care Cardiac rate, rhythm monitoring continuously. Shivering and fasciculation should be avoided. Back-up pacing capability and cardioversion defibrillation equipment should be immediately available at all time. Interrogate CIED ; consultation with a cardiologist or pacemaker-ICD service may be necessary. Restore all antitachyarrhythmic therapies in ICDs Assure that all other settings of the CIED are appropriate.

40. SUMMARY Adopting a multidisciplinary approach that involves the surgeon, anesthetist, cardiologist and industry employed allied health professional is ideal for safe peri -operative CIED management . Decision-making process should be tailored to individual patients and their needs, with the aim of preventing haemodynamic embarrassment consequent to CIED malfunction. Anaesthetic management should be planned preoperatively according to patient’s medical status.

41. Monitoring and anesthesia technique with due considerations to patients CVS status. Initiate invasive arterial pressure monitoring in addition to standard monitoring. Avoid electrocautery use , If necessary consider use of bipolar or harmonic scalpel. Be ready for alternate mode of pacemaker and defibrillator if necessity arises. Rate responsive pacemakers should have rate responsive mode disabled before surgery. Pacemaker should be rechecked after the procedure.

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