Summary
The anesthetic management of patients undergoing cardiac surgery involves meticulous preparation and persistent vigilance. In this chapter, we will discuss the general anesthetic principles that apply to all cardiac surgical procedures in the preoperative, intraoperative, and early postoperative phases. By doing so, we aim to provide a standard approach and rationale for monitoring and managing complex cardiac surgical patients. We will then conclude by highlighting anesthetic considerations that are unique to specific types of cardiac procedures.
Introduction
The anesthetic management of patients undergoing cardiac surgery involves meticulous preparation and persistent vigilance. In this chapter, we will discuss the general anesthetic principles that apply to all cardiac surgical procedures in the preoperative, intraoperative, and early postoperative phases. By doing so, we aim to provide a standard approach and rationale for monitoring and managing complex cardiac surgical patients. We will then conclude by highlighting anesthetic considerations that are unique to specific types of cardiac procedures.
Preoperative Evaluation
Patients requiring cardiac surgery should undergo a thorough preoperative evaluation. The results of this assessment impact preoperative optimization, intraoperative anesthetic management, and postoperative planning. Recommended preoperative tests and objectives are provided in Table 14.1 [Reference Szelkowski, Puri and Singh1]. A sample of a standard cardiac anesthesia setup is listed in Table 14.2.
Table 14.1 Recommended tests before cardiac surgery
| Test | Objective |
|---|---|
| Complete blood count | To detect anemia, thrombocytopenia, and infection |
| Basic metabolic panel | To detect renal disease, electrolyte abnormalities, and poor glycemic control |
| Hemoglobin A1c | To diagnose and determine the severity of diabetes mellitus |
| Liver function tests | To detect unknown liver disease |
| Coagulation profile | To detect unknown coagulation disorders |
| Pulmonary function tests | To aid in differentiating between restrictive and obstructive pathology, and in ventilator weaning |
| Brain natriuretic peptide | When elevated, there is increased risk of atrial arrhythmias and prolonged postoperative stay |
| Thyroid function tests | To detect thyroid dysfunction |
| Blood type and crossmatch | To allow for rapid blood preparation and transfusion, if needed |
| Echocardiography | To detect undiagnosed pathology that may determine hemodynamic goals, selection of appropriate monitors, and need for circulatory support |
| Cardiac catheterization | To evaluate coronary disease, patency of previous grafts, gather information about coronary anatomy and potential targets for grafting, and confirm chamber pressure and severity of pulmonary hypertension |
| Carotid DopplerFootnote a | To detect carotid stenosis and determine perioperative stroke risk |
| Chest radiograph | To evaluate lung fields, detect aortic calcification and pleural effusions, and help identify sternal wires that are a sign of prior sternotomy and implanted medical devices |
a Recommended in patients with a history of transient ischaemic attack or stroke or patients >65 years old with carotid bruits or peripheral vascular disease.
Table 14.2 Cardiac anesthesia setup
|
Maintaining adequate tissue oxygen delivery and hemostasis for patients undergoing cardiac surgery can be challenging. Adequate blood products should be prepared, as transfusion of blood products is often necessary, though the associated risks may complicate the decision to transfuse. The Transfusion Requirements in Cardiac Surgery III trial concluded a restrictive transfusion threshold of 7.5 g dL−1 had noninferior outcomes to a more liberal transfusion threshold and can be used to guide the administration of red blood cells [Reference Shehata, Whitlock and Fergusson2]. Other factors indicating inadequate oxygen delivery, such as low mixed venous oxygen saturation and lactic acidosis, may also support the decision to either transfuse or hemoconcentrate blood to raise the hemoglobin level and oxygen-carrying capacity. The use of plasma, platelets, cryoprecipitate, or other factors should be guided by laboratory testing and clinical bleeding. For patients who refuse blood transfusions, a thorough discussion identifying acceptable alternative strategies in the preoperative period is essential. These alternatives may include the preoperative use of erythropoietin, iron, and vitamin B12 and folate supplementation, as well as intraoperative acute normovolemic hemodilution, cell salvage, and recombinant clotting factors [Reference Hughes, Ullery and Barie3]. Of note, normovolemic hemodilution is contraindicated in severe aortic stenosis, left main coronary artery disease, and preoperative hemoglobin concentration <11 g dL−1. Contraindications to using cell salvage include infection, malignancy, and use of topical hemostatic agents. Of note, platelets and coagulation factors are removed during the washing process, promoting dilutional thrombocytopenia and reduction in clotting factors. Additionally, attempts should be made to prevent fibrinolysis through the use of either tranexamic acid or aminocaproic acid.
Patients undergoing repeat cardiac surgery have adhesive scar encasement of cardiovascular structures and are at risk of sudden massive hemorrhage with repeat sternotomy and mediastinal dissection. CT of the chest should be performed to ascertain the retrosternal position of these structures [Reference Roselli4]. In high-risk patients, it may be necessary to preemptively expose the femoral vessels or even establish peripheral cardiopulmonary bypass prior to sternotomy. Additional units of blood should be readily available and external defibrillator pads should be considered also for these cases.
Any implanted cardiac electronic device should be evaluated prior to cardiac surgery. Important variables to assess include the type of device (e.g., single- or dual-lead pacemaker, biventricular resynchronization pacemaker, implantable cardiac defibrillator), pacemaker dependency, device functionality, and the patient’s underlying rhythm. Pacemakers usually require reprogramming to pace in asynchronous mode, with any tachytherapies disabled to avoid device activation or inhibition by electrical artifacts. In particular, the use of surgical electrocautery in close proximity to the device leads to extensive electromagnetic interference. Patients with disabled tachytherapies should always have external defibrillator pads in place.
Chronically taken cardiac-specific medications that should be continued throughout the perioperative period include statins, aspirin, and beta-blockers. Those that may need to be held prior to cardiac surgery are listed in Table 14.3. Additional medications to consider in the preoperative setting include a benzodiazepine for anxiolysis and fentanyl for analgesia during preinduction arterial catheter placement. Benzodiazepines and fentanyl should be used judiciously, however, to avoid excessive sedation, hypoventilation, hypercarbia, hypoxemia, and increased pulmonary arterial pressure. This is especially concerning in patients with preexisting pulmonary hypertension and/or right ventricular dysfunction.
Table 14.3 Recommendations for holding medications prior to cardiac surgery
| Medication | Recommendation |
|---|---|
| Adenosine diphosphate inhibitors | Stop at least 5 days prior to surgery |
| Coumadin | Stop 3–5 days prior to surgery |
| Direct thrombin inhibitor | Stop 2–4 days prior to surgery |
| Direct factor Xa inhibitor | Stop 2 days prior to surgery |
| Glycoprotein IIb/IIIa inhibitors | Do not take on the day of surgery |
| Angiotensin-converting enzyme inhibitors | Do not take on the day of surgery |
| Angiotensin receptor blockers | Do not take on the day of surgery |
Intraoperative Management
Monitoring
In addition to standard American Society of Anesthesiologists monitors, patients receiving cardiac surgery also require monitoring of continuous five-lead ECG with automated ST-segment analysis, processed EEG to minimize the risk of intraoperative awareness, nerve stimulation of motor activity to ensure immobility, arterial and central venous pressure monitoring to detect sudden changes in hemodynamics, both nasal and bladder temperature monitoring to trend changes induced by cardiopulmonary bypass (CPB), urinary output for assessing end-organ perfusion, and possibly also pulmonary artery pressure, mixed venous oxygen saturation, and cerebral oximetry. Prevailing evidence does not support routine pulmonary artery catheterization. Reasons to place a pulmonary artery catheter include significantly reduced left or right ventricular function, severe diastolic dysfunction, recent myocardial infarction, significant pulmonary hypertension, or high surgical complexity [Reference Sandham, Hull and Brant5]. Transesophageal echocardiography (TEE) is an invaluable tool that is also utilized in cardiac anesthesia. Tables 14.4, 14.5, and 14.6 describe some of the many applications of TEE in cardiac anesthesia, as well as indications and contraindications to use [Reference Nicoara and Swaminathan6].
Table 14.4 Role of transesophageal echocardiography in cardiac surgery
| Evaluation | Impact |
|---|---|
| LV and RV systolic function | Aids in determining appropriate monitors, fluid resuscitation, pharmacologic agents, and perioperative mechanical circulatory support |
| LV diastolic function | Aids in determining optimum heart rate to allow for maximum cardiac output |
| Regional wall motion abnormalities | Aids in early detection of ischemia and is predictive of long-term adverse cardiac events |
| Ventricular dimensions | Aids in determining failure of the left or right ventricle. Ventricles that undergo chamber dilatation are less sensitive to preload and extremely sensitive to increased afterload |
| Valvular function | Evaluating the severity of valvular lesions aids in determining hemodynamic goals and may prompt surgical intervention |
| Aortic atheroma | The presence of large or mobile atheromas have been associated with a higher incidence of postoperative stroke |
| Pericardial diseases and effusion | Large pericardial effusions could indicate tamponade pathology. Patients with pericarditis or pericardial constriction typically have significant blood loss |
| Anatomic defects | Previously undiagnosed anatomic defects may alter the surgical plan. Septal defects can result in RV volume overload and pulmonary hypertension. It is important to look for additional associated congenital cardiac anomalies (i.e., coronary sinus defects, partial anomalous venous connection, or cleft anterior mitral valve leaflet) |
| Arterial or mural thrombus | Thrombus in the left atrial appendage or apex of the left ventricle may prompt thrombectomy or ligation of the left atrial appendage. The presence of the thrombus should be confirmed with TEE both during and after surgery |
| Guide line/cannula placement | Direct visualization can aid in placement of lines and cannulae |
| De-airing procedures | Direct visualization of the ventricle can aid in this procedure to avoid air embolism |
| Surgical feedback | Immediate feedback with the surgical team regarding the adequacy of surgical repairs and possible collateral injury can prompt additional intervention prior to leaving the operating room |
LV, left ventricular; RV, right ventricular; TEE, transesophageal echocardiography.
Table 14.5 Indications for transesophageal echocardiography
| Valvular procedures |
| Thoracic aortic surgical procedures |
| Transcatheter intracardiac procedures (undergoing general anesthesia) |
| Congenital heart surgery with cardiopulmonary bypass |
| Hypertrophic cardiomyopathy surgery |
| Resection of cardiac mass |
| Ventricular remodeling surgery |
| Heart transplantation |
| Pericardiectomy |
| Ventricular assist device insertion |
| Cannula positioning |
| Septal defect closures |
| Atrial appendage obliteration |
| CABGFootnote a |
| Unexplained hemodynamic instability during any surgical procedure |
a Should be considered for CABG and off-pump CABG. Generally recommended for patients with abnormal ventricular function, though may play an important role in all cases.
CABG, coronary artery bypass graft.
Table 14.6 Contraindications to transesophageal echocardiography
| Absolute contraindications | Relative contraindications |
|---|---|
| Esophageal stricture | Esophageal varices |
| Esophageal trauma | Acute esophagitis |
| Esophageal tumor | Barrett’s esophagus |
| Postesophageal surgery | Restriction of neck mobility (severe cervical arthritis/atlantoaxial joint disease) |
| Tracheoesophageal fistula | History of radiation of the neck and mediastinum |
| Acute upper GI bleed | Coagulopathy |
| History of GI surgery | |
| Recent upper GI bleed | |
| Acute peptic ulcer disease |
GI, gastrointestinal.
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