Anesthesiology

Minimally invasive aortic valve replacement

What the Anesthesiologist Should Know before the Operative Procedure

Minimally invasive aortic valve replacement (MIAVR) can be performed as an elective or non-elective procedure. It represents an alternative approach to median sternotomy for surgical aortic valve replacement.

Signs and symptoms of aortic stenosis (AS):

- decreased exercise capacity

- angina

- syncope

- congestive heart failure

Signs and symptoms of aortic insufficiency (AI):

- decreased exercise capacity

- angina

- dyspnea / pulmonary edema

- tachycardia, water hammer pulse

Surgical approach:

- 6-8 cm right minithoracotomy in the second or third intercostal space (most commonly) (Figure 1)

Minimally invasive aortic valve replacement - intraoperative approach

- Cardiopulmonary bypass required

- Cannulation of the ascending aorta, cannulation via the femoral artery as an alternative option

- Aortic cross-clamp and aortic cannulation is required for antegrade cardioplegia, direct cannulation of coronary ostia in case of AI

- Venous cannulation can be performed via the femoral vein or directly through the right atrium.

- Retrograde cardioplegia via coronary sinus catheter (percutaneously via jugular vein) or direct placement by the surgeon

- Surgical field flooded with CO2 to increase absorption rate of inadvertently intravascularly introduced gas

- Right pleural chest tubes are placed at completion of surgical procedure

1. What is the urgency of the surgery

Patients with symptomatic valvular disease from aortic stenosis and/or aortic insufficiency require aortic valve replacement. PUBMED:12835667, PUBMED:21871335, PUBMED:19130998

Symptoms of heart failure, angina, or syncope indicate a higher level of urgency to undergo surgery.

Emergent surgery can be associated with other cardiac or vascular pathology requiring modification of the surgical technique or choice of a standard sternotomy approach:

  • Aortic stenosis (AS): Concomitant three vessel coronary artery disease or left main disease might require simultaneous CABG

  • Aortic Insufficiency (AI): In acute AI aortic dissection is common, possibly requiring repair via sternotomy

  • Aortic valve endocarditis requiring immediate valve replacement

    • Emergent/urgent indication - heart failure, angina, or syncope

    • Elective - known AS or AI causes symptoms such as dyspnea or decreased exercise tolerance. First signs of left ventricular dysfunction on transthoracic echocardiography (TTE) are indication for elective AVR.

2. Preoperative evaluation

A thorough history and physical examination should be obtained with special emphasis on:

  • Coronary artery disease

  • Congestive heart failure

  • Cardiomyopathy

  • Cardiac dysrhythmia

  • Aortic aneurism

  • Aortic dissection, especially in acute AI

  • Presence of AI in cases of AS

  • Peripheral vascular disease

  • Cerebrovascular disease

  • Diabetes type I/II

  • Acute / chronic kidney disease

  • Previous cardiac surgery

  • Chronic obstructive pulmonary disease

  • Connective tissue disorder, e.g. Marfan's disease

  • History of rheumatic fever

Time for evaluation is dictated by level of urgency for the procedure. Delaying surgery may be indicated in an elective repair for:

  • Non-invasive revascularization of concomitant coronary artery disease - alternatively combined AVR/CABG procedure via sternotomy

  • Therapy of non-valvular causes of heart failure

  • Therapy of symptomatic arrhythmia

  • Therapy of severe dental decay prior to implantation of hardware

  • Treatment of poorly controlled diabetes

  • Treatment or newly diagnosed kidney disease

  • Treatment to enable optimization of respiratory function

  • Treatment of infection, e.g., urinary tract infection

a. Cardiovascular system

Coronary artery disease

  • Evaluation: History and physical exam, EKG, possibly Holter monitor, Echocardiography as indicated, stress testing as indicated

  • Goals of management: Medical optimization, e.g., with betablocker, statin, and aspirin therapy, revascularization as indicated

Congestive heart failure

  • Evaluation: History and physical exam, EKG, Echocardiography as indicated, stress testing as indicated, TTE to rule out other reasons for heart failure (e.g. other valve disease)

  • Goals of management: Therapy of active CHF as indicated to achieve resolution of symptoms not thought to be secondary to aortic valvular disease

Arrhythmia

  • Evaluation: History and physical exam, EKG, possibly Holter monitor, transesophageal echocardiography (TEE) to rule out left atrial thrombus

  • Goals of management: Therapy of symptomatic arrhythmia as indicated, e.g., cardioversion for atrial fibrillation

c. Pulmonary

Pulmonary disease

  • Evaluation: History and physical exam, chest X-ray, pulmonary function tests (ABG, FEV1, FVC, DLCO) as indicated

  • Goals of management: Optimization of respiratory function, e.g., adding bronchodilator therapy in obstructive airway disease, adding inhaled steroids for poorly controlled asthma, therapy of pulmonary infection

d. Renal-GI:

Acute and/or chronic kidney disease

  • Evaluation: History and physical exam, basic metabolic panel, creatinine clearance, further testing as indicated

  • Goals of management: Treatment of reversible causes of kidney disease, e.g., hypovolemia with hydration

Gastroesophageal reflux disease (GERD)

  • Evaluation: History and physical exam, further testing as indicated, e.g., esophagogastroscopy

  • Goals of management: Treatment, e.g., with proton pump inhibitors

e. Neurologic:

Cerebrovascular disease

  • Evaluation: History and physical exam, further evaluation as indicated, e.g., ultrasound Doppler examination of the carotid arteries

  • Goals of management: Diagnosis and documentation of pre-existing neurologic deficits, therapy as indicated, e.g., carotid endarterectomy

Peripheral nerve injury

  • Evaluation: History and physical exam, further evaluation as indicated, e.g., nerve conduction studies

  • Goals of management: Diagnosis and documentation of pre-existing neurologic deficits, determination of optimal intraoperative positioning

Infectious diseases

  • Evaluation: History and physical examination, urinary analysis, screening for MRSA, further testing as indicated

  • Goals of management: Therapy of active infection, e.g., urinary tract infection with antibiotics, isolation of carriers of resistant organisms

f. Endocrine:

Diabetes mellitus

  • Evaluation: History and physical examination, review of records, distinction between type 1 and type 2 diabetes, laboratory as indicated, e.g., fasting glucose, hemoglobin A1C

  • Goals of management: Diabetic management to achieve adequate glycemic control, determination of optimal perioperative insulin regimen, determination of regimen for perioperative antidiabetic oral medications, if needed obtain endocrine consultation

g. Dental:

  • Evaluation: History and physical examination

  • Goals of management: Restoration or removal of decayed teeth prior to implantation of hardware

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

Anticoagulant / anti platelet medications, e.g., aspirin, clopidogrel, coumadin

  • Evaluation: Review of records and indications

  • Goals of management:

  • Patients on aspirin: current guidelines advocate preoperative withdrawal of aspirin only in strictly elective patients without coronary syndromes with the expectation that blood transfusion will be reduced (IIa recommendation, level of evidence A).PUBMED:17462454

  • Patients on thienopyridines (such as clopidogrel): current guidelines consider it reasonable to discontinue thienopyridines 5 to 7 days prior to cardiac procedures to limit blood loss and transfusion (IIa recommendation, level for evidence B).PUBMED:17462454 Alternatively, patients can be transitioned to more short-acting

  • Patients on coumadin should be transitioned to perioperative i.v. heparin infusion

5. What laboratory tests should be obtained?

Complete blood count (CBC), PT/PTT, metabolic panel, Type and screen, antithrombin 3 level if patient was on heparin, other tests as indicated

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

The standard anesthetic technique for this procedure is general anesthesia

a. Regional anesthesia -

Given the need for systemic anticoagulation during cardiopulmonary bypass, epidural anesthesia is not commonly employed

1. Epidural

  • Advantage: Improved postoperative analgesia

  • Drawbacks: Higher risk for epidural hematoma in the setting of systemic anticoagulation, possibly need for rescheduling of procedure if "bloody tap" obtained during placement of epidural catheter

1. Peripheral Nerve Block

  • Paravertebral blocks/catheters are a possible option, but there generally is little experience employing this technique in this setting. However, paravertebral nerve blocks might pose less risk for epidural hematoma in the setting of systemic anticoagulation

  • Intercostal nerve blocks or single shot paravertebral nerve blocks offer short term analgesia

Monitoring

1. ASA standard monitors (electrocardiogram, blood pressure, pulse oximetry, capnography, temperature)

2. Radial arterial line - check bilateral upper extremity NIBP prior to placement to evaluate for arterial stenosis leading to falsely low BP measurement, alternatively femoral arterial access

3. Central venous access is recommended

4. TEE:

  • Allows placement of retrograde cardioplegia cannula under direct vision Allows placement of femoral venous drainage cannula under direct vision

  • Allows evaluation of aorta for atheromatous disease prior to placement of aortic cross-clamp

  • Allows evaluation of valvular status pre and post replacement of aortic valve

  • Allows evaluation of prosthetic valve in situ

  • Allows evaluation of myocardial function pre and post repair

5. Optional PAC - weigh risk of adverse effects inducing arrhythmia in setting of AS against value of monitoring RVSP, LVEDP

6. Optional BIS

7. Optional cerebral pulse oximetry

8. Urine output

Complications

  • Cardiac complications: new onset atrial fibrillation, conduction delays requiring permanent pacemaker, need for conversion to open procedure or reoperation

  • Pulmonary: aspiration pneumonia, ARDS, TRALI

  • Neurologic: stroke, coma, delirium, cognitive dysfunction, seizures

  • Renal: acute kidney injury

  • Infectious: wound infection, mediastinitis

  • Hematologic: bleeding, complications from transfusion, e.g. TRALI

c. Postoperative management

  1. Analgesic modalities: IV opioids initially, conversion to oral regimen as soon as possible - usually after 12 hours. Adjunct analgesics: Acetaminophen, pregabalin, NSAIDs if no contraindication

  2. Disposition: ICU

  3. Postoperative concerns include: Arrhythmia, paravalvular leak, bleeding, cardiac tamponade, myocardial ischemia, stroke, infection

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