Anesthesiology

Pacemaker or AICD Insertion

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1. What the anesthesiologist should know before the operative procedure

Pacemakers and AICDs are implantable devices, used to deliver electrical therapy to the heart in patients with rhythm disturbances, dysfunction of the cardiac conduction system and heart failure.

AICDs detect tachyarrhythmias, and deliver an antiarrhythmic therapy, either by overdrive pacing (pacing at a higher rate than the patient's intrinsic rhythm), or by cardioversion (defibrillation), depending on the type and rate of the arrhythmia. These devices also have built in pacemakers.

Permanent pacemakers (PPM) deliver electrical energy to the heart to restore or enhance cardiac pacing and conduction when required. The majority of indications are for symptomatic bradyarrhythmias. Pacing lead positions may include the right atrium, the right ventricle and occasionally the coronary sinus (to enable left ventricular pacing with biventricular devices used for resynchonization therapy in patients with heart failure).

The decision to implant a permanent pacemaker or AICD should be based on sound clinical evidence, per the American College of Cardiologists (ACC) and American Heart Association (AHA) guidelines.

Patients presenting for these procedures usually have significant cardiovascular disease, and often have other major systemic diseases as well. A careful preoperative assessment is therefore always required.

Procedures are usually performed under local anesthetic with or without mild sedation. In addition, where indicated, AICD defibrillation threshold (DFT) testing requires a brief period of general anesthesia.

Patients with significant orthopnea may not be able to tolerate the required supine position, and medical management should be optimized prior to the procedure, or general anesthesia should be used.

Reversible causes of an unstable conduction or rhythm disturbances, such as electrolyte abnormalities or drug interactions, should always be ruled out first.

What is the urgency of the surgery?

The implantation of permanent devices is performed on an elective basis.

Unstable patients should be managed with temporary devices, and medical management should be optimized prior to the insertion of a permanent device.

What is the risk of delay in order to obtain additional preoperative information?

Emergent: Surgery is never emergent. Unstable patients should be managed according to the American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Once stable and reversible causes have been corrected, and the patient meets criteria for a permanent device, surgery can be done on a scheduled basis.

Urgent: Patients requiring hospitalization, in particular when observation in an intensive care unit is required while awaiting insertion of a permanent device, should be accommodated ahead of electively scheduled cases.

Elective: The majority of procedures can be performed on an ambulatory basis.

2. Preoperative evaluation

What medical conditions warrant further evaluation?

Further evaluation is seldom indicated:

  • These are minor surgical procedures with minimal associated risk, usually performed under local anesthetic infiltration with minimal sedation

  • Detailed cardiology assessments are usually available for review.

A detailed anesthetic assessment is always required:

  • Patients often have significant cardiovascular and other systemic disease that might impact on the choice of drugs for sedation, amount of sedation administered or the need for general anesthesia.

  • The underlying etiology of the arrhythmia or conduction block may have specific anesthetic implications. Underlying conditions include ischemic cardiomyopathy, dilated cardiomyopathy, hypertophic cardiomyopathy, infiltrative disorders such as hematological malignancies, sarcoidosis and amyloidosis, and chronic neuromuscular disorders such as Duchenne's and other muscular dystrophies.

Specific conditions that should be noted preoperatively:

  • allergies, in particular to antibiotics or intravenous radiocontrast media

  • the risk, presence or history of intracardiac thrombus requiring anticoagulation

  • signs, symptoms or risk factors for infection (white cell count, urine analysis, indwelling catheters, central lines or temporary devices)

  • vascular patency for device insertion (previous devices, central vascular access lines, deep venous thrombosis or orthopedic injuries to upper extremities)

  • orthopnea

  • obstructive sleep apnea

  • pulmonary hypertension

  • low left ventricular ejection fraction

  • significant valvular heart disease

3. What are the implications of co-existing disease on perioperative care?

b. Cardiovascular system

Coronary artery disease - myocardial ischemia and infarction are common causes of cardiomyopathy, ventricular arrhythmias and conduction block, resulting in the need for an AICD or PPM. A detailed cardiology assessment should be available, and medical management should be optimized.

Heart valve disease - patients with heart valve disease, in particular aortic valve disease, mitral valve disease, rheumatic heart disease and endocarditis commonly develop conduction defects and arrhythmias.

Heart surgery - About 1.5% of all cardiac surgery patients may require a PPM postoperative. Following aortic valve replacement surgery 5% of patients will require PPM insertion. Complete heart block is also common following mitral and tricuspid valve repair or replacement. A third of patients requiring PPM insertion will recover normal conduction in the long-term. To allow time for spontaneous recovery, while enabling early discharge, it is recommended to insert a PPM on day 5 postoperative.

Cardiomyopathy - the majority of patients presenting for AICD insertion have a low left ventricular ejection fraction (EF) with heart failure symptoms. The presence of left ventricular or left atrial appendage thrombus (in the presence of atrial fibrillation) should be ruled out in patients not therapeutically anticoagulated. Orthopnea, preventing patients from lying flat, should be identified preoperatively. Small boluses of intravenous induction agent (propofol 10-20 mg) should be titrated slowly to loss of consciousness, to enable DFT testing. DFT testing is often not performed in patients with severe LV dysfunction, or severe pulmonary hypertension, due to the risk of persistent ventricular fibrillation or pulseless electrical activity.

Pulmonary hypertension - apart from the risk for PEA with DFT testing, care should be taken to use minimal sedation in patients with pulmonary hypertension, avoiding hypercapnea and acidosis that might induce right ventricular decompensation.

Atrial fibrillation and atrial flutter - left atrial appendage thrombus should be ruled out by transesophageal echocardiography in atrial fibrillation or flutter patients presenting for a PPM or AICD, unless they have been therapeutically anticoagulated for at least 3 weeks. In the absence of adequate anticoagulation (INR 2-3, or aPTT 1.5-2 times higher than normal), the risk for stroke within the first 10 days following cardioversion resulting from electric shock, pacing or spontaneous cardioversion may exceed 5%.

c. Pulmonary

Chronic obstructive pulmonary disease - common in patients with smoking related heart disease. The presence of an active infective exacerbation, associated with increased sputum production, response and elevated white cell count, surgery should be postponed. Patient should be able to lie flat on 1 pillow for the duration of the procedure. Routine bronchodilator therapy should be continued. Minimal amounts of short-acting sedation should be administered to patients with end-stage lung disease.

Obstructive sleep apnea - an important cause of arrhythmias and pulmonary hypertension. Minimal sedation should be used, to prevent airway obstruction, which could increase the risk for air embolism, or hypoxia and hypercarbia, which might aggravate pulmonary hypertension when present. CPAP should be available.

Gastroesophageal reflux - more common and often asymptomatic in patients with obstructive sleep apnea and reactive airways disease. When other risk factors are present, such as hiatal hernia or diabetic autonomic neuropathy, patients should receive aspiration prophylaxis. General anesthesia with rapid sequence induction should be considered.

d. Renal-GI

Patients with advanced heart disease commonly have renal impairment, and cardiac disease is more common in patients with end-stage renal disease. As a result, patients presenting for PPM or AICD insertion often have chronic renal impairment.

In patients on hemodialysis cardiac disease accounts for 45% of all deaths, of which 60% are the result of sudden cardiac death (PUBMED:12694343). PPM and AICDs are therefore common in this patient population. The long-term risk for lead and device infection is increased in dialysis patients due to vascular access procedures and an impaired immune response.

Acute renal dysfunction is also common in patients recovering from heart surgery, myocardial infarction, or acute systemic illness.

Minor procedures such as the insertion of a device do not result in fluid shifts, and generally do not increase the risk for acute kidney injury.

Fluid and electrolyte abnormalities are common in patients with renal impairment and should be identified.

Diuretic therapy - should be continued in the perioperative period. Intravascular dehydration should be anticipated and the level of sedation should be adjusted accordingly to prevent hypotension. Associated electrolyte abnormalities such as hypokalemia and hypomagnesemia should be identified and corrected.

Hemodialysis - routine dialysis should be continued. Patients on hemodialysis have a high incidence of central venous stenoses from multiple vascular access procedures for dialysis. This might complicate lead insertion and should be identified preoperatively. When experiencing difficulties during lead placement, a venogram could identify stenoses.

Bleeding tendency - patients with uremia have platelet dysfunction, which may warrant desmopressin (PUBMED:17322926).

GI -Routine management

e. Neurologic:

Intracardiac thrombus should be ruled out in patients with cardiomyopathy or atrial fibrillation prior to device insertion.

f. Endocrine:

Routine management.

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (eg. Musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

Deep venous thrombosis: a history of previous deep venous thrombosis of upper extremities might require a venogram prior to lead insertion to document vascular patency.

Previous orthopedic injuries or surgery, breast surgery, or dialysis fistuli might also impact surgical site selection

4. What are the patient's medications and how should they be managed in the perioperative period?

All medications should be continued.

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

Anticoagulant agents:

  • commonly prescribed

  • care should be taken to maintain coagulation assay results are in the therapeutic range to avoid thrombotic and bleeding complications

  • there is no need for using a heparin bridge in patients on oral anticoagulants, and maintaining an INR around 2.5 might be associated with fewer bleeding complications than with a heparin bridge (PUBMED:20202136).

i. What should be recommended with regard to continuation of medications taken chronically?

All chronic medications should be continued.

j. How To modify care for patients with known allergies-

Allergies to IV contrast agents should be identified in advance, and an oral regimen that includes a corticosteroid and histamine antagonists (H1 and H2) should be initiated a day or 2 in advance. These drugs may also be administered in IV formulation immediately prior to exposure to contrast agents. Consideration should be given to avoiding contrast exposure.

k. Latex allergy- If the patient has a sensitivity to latex (eg. rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

If the patient has a sensitivity to latex vs. anaphylactic reaction, prepare the operating room with latex-free products.

l. Does the patient have any antibiotic allergies? (common antibiotic allergies and alternative antibiotics)

N/A

m. Does the patient have a history of allergy to anesthesia?

N/A

5. What laboratory tests should be obtained and has everything been reviewed?

Coagulation assays: should be in therapeutic range when on anticoagulants to avoid thrombotic or hemorrhagic complications; for patients on Coumadin the INR should be around 2.5 (PUBMED:20202136 )

Electrolytes: potassium in particular should be normalized when abnormal

Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?

a. Regional anesthesia

  1. Neuraxial - Not applicable

  2. Peripheral nerve block - Not applicable

  3. Surgical field infiltration - Used in all patients; administered by surgeon; may be the sole anesthetic in high-risk patients.

b. General Anesthesia

Seldom indicated. Might be considered in the following patients:

  1. Severe orthopnea

  2. Severe reflux

c. Monitored Anesthesia Care

  1. Benefits: surgical planes of anesthesia are not warranted, sedation is titrated to patient comfort, rapid recovery with fewer drug-related side effects.

  2. Drawbacks: airway not protected

  3. Other issues: some patients may become disinhibited or agitated

6. What is the author's preferred method of anesthesia technique and why?

What prophylactic antibiotics should be administered?

Cephazolin or cefuroxime should be administered within 1 hour prior to incision; in patients with a beta-lactam allergy vancomycin or clindamycin should be used. Several studies have documented the benefit of prophylactic antibiotic administration at the time of device insertion (PUBMED:19808441).

What do I need to know about the surgical technique to optimize my anesthetic care?

The devices consist of an impulse generator and leads. There are two basic approaches for lead placement: transvenous (by far the most common) or epicardial. Epicardial lead placement is more challenging and has a higher infection rate. It is reserved for patients where transvenous lead placement is not feasible, and is done in the operating room through a median sternotomy, left thoracotomy, subxyphoid, or subcostal approach. Transvenous lead placement is usually performed in the EP laboratory under high-resolution fluoroscopic guidance. Devices are usually implanted in the left upper pectoral region (in right-handed patients). Venous access for lead placement can be obtained, with or without the aid of a venogram, from the subclavian, the internal jugular, external jugular, axillary or cephalic vein.

The ventricular lead is advanced into the right ventricular apex, the atrial lead into the right atrial appendage and in the case of a biventricular pacemaker an additional lead is advanced into the coronary sinus. The pacing and sensing thresholds are then determined, and if sufficient the generator is positioned in a pocket in the prepectoral fascia. In the case of AICD insertion the defibrillation threshold (DFT), or the lowest amount of energy required to defibrillate the heart is determined. Given the rare need for system revision and the reliability of modern AICD devices in terminating ventricular tachyarrhythmias, the need for routine testing at the time of device implantation has been called into question (PUBMED:18687250). The most common approach in clinical practice to approximate the DFT is to induce ventricular fibrillation (through burst stimulation or shock-on-T) at least twice and defibrillate the patient with an energy setting of at least 10 J less than the maximum output of the AICD.

What can I do intraoperatively to assist the surgeon and optimize patient care?

Optimum patient comfort and cooperation should enable optimum conditions for device insertion. Careful explanation and patient education in advance, generous local anesthetic infiltration with bupivacaine 0.25% with epinephrine, and a propofol infusion, carefully titrate to patient comfort (10-50 mg/kg/h) is the author's preferred method of anesthesia. This not only ensures patient comfort, but also allows for rapid reversal of unwanted side effects of sedation, such as hypotension, airway obstruction and snoring, by decreasing the dose. It also enables rapid reversal at the end of the procedure with minimal risk for nausea or prolonged sedation.

Alternatives, (or adjuncts) may include small amounts of fentanyl (25-100 mcg administered as 25-mcg boluses) and midazolam (0.5-2 mg). A brief state of general anesthesia is induced for DFT testing using small boluses of propofol (20 mg), carefully titrated to loss of consciousness, while maintaining spontaneous respiration and supporting the blood pressure with phenylephrine if required.

What are the most common intraoperative complications and how can they be avoided/treated?

Prioritize them by urgency. Insertion of PPM or AICD is a relatively safe procedure and seldom leads to complications. However, it may lead to life-threatening complications of which the anesthesiologist need to be acutely aware. Obtaining vascular access may result in a pneumothorax due to pleural injury, or hemothorax due to vascular injury. Leads may also perforate the heart during placement, which may lead to tamponade. Unexplained desaturation and or hemodynamic derangements should therefore be communicated, and these potential complications should be ruled out systematically.

Complications

Cardiac: Procedure-related complications include vascular injury, hemorrhage, venous air embolism, cardiac perforation with tamponade, heart valve damage, and lead dislodgement. Patients may also develop arrhythmias while undergoing procedures, or even develop complete heart block requiring temporary pacing. Anesthetic related complications include hypotension, which may lead to myocardial or cerebral ischemia.

Pulmonary: Procedure-related complications include pneumothorax due to pleural injury or acute orthopnea due to positioning. Anesthetic-related complications include aspiration and acute airway obstruction in a patient where access to the airway might be challenging due to the environment.

Neurologic: Unique to procedure: Patients with undiagnosed intracardiac thrombus prior to device insertion are at risk for stroke.

a. Neurologic:

N/A

b. If the patient is intubated, are there any special criteria for extubation?

N/A

c. Postoperative management

What analgesic modalities can I implement?

With adequate local anesthetic infiltration during the procedure, surgical site pain is generally not an issue. Patients with preexisting painful musculoskeletal disorders may experience increased discomfort due to positioning during the procedure. This can generally be managed with oral analgesics.

What level bed acuity is appropriate?

In uncomplicated cases, these procedures are performed as outpatient procedures.

What are common postoperative complications, and ways to prevent and treat them?

Generator pocket hematoma has been associated with an increased risk for device infection. This might be related to inadequate hemostasis, or the use of anticoagulants. Pneumothorax, hemothorax, and tamponade may have delayed presentations in the early postoperative period.

What's the Evidence?

Circulation. vol. 122. 2010. pp. 18.

Herzog, CA. "Cardiac arrest in dialysis patients: approaches to alter an abysmal outcome". Kidney Int Suppl . vol. 84. 2003. pp. S197-200.

Hedges, SJ, Dehoney, SB, Hooper, JS, Amanzadeh, J, Busti, AJ. "Evidence-based treatment recommendations for uremic bleeding". Nat Clin Pract Nephrol . vol. 3. 2007. pp. 138-53.

Love, CJ. "Perioperative management of anticoagulation in patients undergoing cardiac rhythm device procedures: a bridge to nowhere?". Pacing Clin Electrophysiol . vol. 33. 2010. pp. 383-4.

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