Chapter 1. Preoperative Evaluation of the Heart Surgery Patient

• It is often said that the anesthesiologist is the internist of the operating room (OR). By extension, the cardiac anesthesiologist becomes the OR's cardiologist. While it is certainly true that anesthesiologists must have knowledge of medicine in general and cardiology in particular, the practice of cardiac anesthesia is a unique discipline unto itself. Although cardiac anesthesiologists must have knowledge of why someone is being taken to cardiac surgery, they will not be the ones to decide if surgery is indicated or not. Rather, cardiac anesthesia staff must review the totality of the patient's cardiac and medical history to determine the best approaches to manage sick patients perioperatively. This chapter will briefly examine how someone is referred for cardiac surgery and the essential elements of preoperative evaluation necessary for patient management.

Patients of all types present for heart surgery. From the smallest, hypoxemic infant with congenital heart disease to the 90-year-old with critical aortic stenosis, all varieties of patients undergo heart surgery. Even patients undergoing the same type of surgery can vary greatly depending upon their preoperative comorbidities and the impact their disease has had upon their cardiac function. A patient with well-preserved ventricular function presents far different challenges than an individual with a low ejection fraction. Likewise, the patient with intact renal function free of diabetes and lung disease is potentially less problematic than the person afflicted with these comorbidities. In this regard the conduct of cardiac anesthesia parallels that of any anesthetic. A patient's comorbidities are considered as the anesthetist determines the appropriate anesthetic technique, monitoring, and plan for postoperative management. What is perhaps unique about cardiac anesthesia is that so many of these comorbidities are regularly present; the "routine" cardiac surgery patient is incredibly sick both as a consequence of their primary heart disease as well as the associated illnesses which occur frequently in this patient population.

Generally, the "routine" cardiac surgery patient is designated as an American Society of Anesthesiologists (ASA) class 4. No one undertakes cardiac surgery on a whim and as such anesthesia consent should be direct and sobering to avoid excessive optimism in patients and their families. All patients are informed of the inherent risk of death, stroke, neurological dysfunction, or renal failure. The risk/benefits of transesophageal echocardiography (TEE) should likewise be discussed with the patient preoperatively. Although the risk of stroke following bypass surgery is low (3%)1 and that of death even lower, cardiac surgery is associated with multiple postoperative morbidities including cognitive dysfunction, renal failure, gut ischemia, and potentially prolonged ICU care. Because both the surgeon and the anesthesia team influence the patient's hemodynamic performance it is often difficult to discern whether surgery or anesthesia is responsible for an adverse outcome. Ideally both the surgery and cardiac anesthesia groups function as a team sharing the joy when difficult patients are safely managed and sharing the anguish when the inevitable death or brain injury occurs. Anesthesiologists entering into cardiac anesthesia practice should be aware that outcomes are often disappointing and there is the ever-present risk of litigation even if the anesthesiologist has practiced according to all possible standards of care. Unfortunately, adverse events happen to people during cardiac surgery as a consequence of both patient illness and the numerous techniques necessary to repair the dysfunctional heart. Careful documentation and frank discussions with patients and their family are essential in cardiac anesthesia practice.

Although patients of all ages, races, and genders present for cardiac anesthesia and surgery, access by all demographic groups to cardiac surgery therapies may not be equal.2 Disadvantaged groups may have less access to invasive cardiac surgery procedures.3-5 Female patients are at risk for higher mortality when undergoing coronary bypass surgery. Why such discrepancies in outcomes and access? It is possible that female patients are at disadvantage because they present at an older age with poorer ventricular function as well as more comorbid disease states such as diabetes and renal dysfunction. Patients from less well-off communities may have less access to surgery or are perhaps treated in less well-equipped hospitals.

Also, female patients following coronary artery surgery may have a longer period of intubation and length of hospital stay.6 This may be secondary to the increased incidence of comorbidities in female cardiac surgery patients.

The increased use of angioplasty and stents to treat coronary artery disease has reduced the number of patients presenting for heart surgery. The otherwise healthy patient with preserved ventricular function and angina in need of a two-vessel bypass is increasingly rare in the cardiac surgery operating room. Many patients undergo various percutaneous coronary interventions (PCIs) as first-line therapy upon presentation with anginal pain. Many studies have tried to highlight the risks and benefits of coronary artery bypass surgery versus medical therapy versus bare metal stents versus drug eluting stents for the definitive treatment of coronary disease. As catheter-mediated valve replacement becomes even more perfected, debate will likely follow on the benefits and risk of valve surgery versus catheter-mediated valve replacement.

Serruys et al prospectively randomized 1800 patients with severe three vessels or left main coronary artery disease to cardiac surgery or PCI assuming that both techniques in the opinion of the patient's cardiologist and cardiac surgeon could achieve equivalent anatomical revascularization.7 They demonstrated that the rates of adverse cardiac or cerebrovascular events at 1 year were higher in the PCI group secondary to the increased need for repeat revascularization efforts in those patients treated with stents as opposed to surgery. The medicine, angioplasty, or surgery study (MASS) II trial randomized 611 patients with coronary disease to surgery, PCI, or medical therapy (MT).8 At 5 years the three approaches resulted in similarly low death rates. However, patients undergoing surgery required fewer additional procedures during the study period. A meta-analysis looking at four trials comparing stent versus bypass surgery revealed that the overall incidence of adverse cardiac or cerebrovascular events was lower in the surgery group secondary to the reduced need in operated patients to perform repeat revascularization procedures.9 However, survival at 5 years was not found different between the groups.

The risk of stent thrombosis with both bare metal and drug eluting stents is well known.10 Patients following stent placement are treated with various antiplatelet regimens to prevent stent thrombosis. The anesthesia staff should not take it upon themselves to discontinue antithrombotic or antiplatelet medication perioperatively in patients treated with stents. Only the patient's cardiologist and surgeon should determine collectively if antiplatelet medications should be discontinued perioperatively and if surgery is to be considered in a patient with prior stent placement. However, patients requiring antiplatelet therapy perioperatively are likely to require large amounts of blood products during surgery and the anesthesiologist should be prepared for this situation.

Frequently, the cardiac patient coming for revascularization nowadays will have undergone PCI at some point in the past. Surgery is elected when lesions are not amenable to PCI or the patient has combined coronary arterial and valvular heart disease. Such patients may have presented with recurrent myocardial infarctions prior to each stent placement. Over time, patients can develop ventricular dysfunction from recurrent myocardial ischemia and infarction.

Patients with cardiac angina, positive stress tests, nuclear medicine scans suggestive of myocardial ischemia, valvular heart disease, and ventricular dysfunction are routinely taken to the cardiac catheterization laboratory for diagnostic purposes. Catheterization demonstrates the coronary vasculature and pathology. PCI is usually performed at the time of diagnosis or the patient is referred for surgery. Figure 1–1 demonstrates the normal left and right coronary anatomy. Figure 1–2 reveals occlusions in both the left and right circulations (Video 1–1). Coronary artery lesions are frequently treated with percutaneously placed stents (Video 1–2). When the patient's anatomy does not favor PCI, patients are referred for surgery. Newer technologies using magnetic resonance imaging and computed tomography have been employed to better visualize the coronary arteries.11,12 The role of these technologies in the diagnosis and treatment of coronary artery disease is likely to increase. However, at present cardiac catheterization remains the most common pathway by which patients find their way to surgery.

Patients present with cardiac disease to the cardiologist either electively or emergently. Increasingly, patients are being treated with emergency catheterization and PCI rather than with systemic thrombolytic therapy (an alternative emergency therapy for acute myocardial ischemia refractory to antianginal drugs). From time to time patients will present directly from the catheterization laboratory after emergency cardiac interventions when PCI is not considered feasible or when PCI has failed to restore blood flow. Such patients usually have been administered antiplatelet drugs such as glycoprotein IIb/IIIa inhibitors and/or heparin. These patients when taken to surgery emergently are at very high risk for protracted bleeding.

Patients presenting for elective surgery generally have the benefit of a more thorough cardiology workup. Transthoracic echocardiography (TTE) has usually been performed preoperatively to provide an estimate of valvular integrity and cardiac function.

Occasionally there are significant differences between the preoperative TTE and the intraoperative transesophageal echocardiography examination. Therefore, the cardiac anesthesiologist should perform an independent assessment through a comprehensive and thorough intraoperative TEE examination.

Ultimately the choice of the therapeutic modality (surgery vs PCI) is the decision of the surgeon and the cardiologist. However, the anesthesiologist should inform both surgeon and cardiologist regarding specific anesthesia-related concerns (airway difficulties, malignant hyperthermia risk, etc) which might increase the patient's risk of surgery versus catheter-mediated therapies. In this way, they may factor those anesthesia-specific concerns into the overall risk/benefit calculations and discussions with the patient.

Patients presenting for heart surgery, whether electively or emergently, require the routine preoperative assessment that is incumbent with general anesthesiology practice. Obviously the patient in cardiac arrest undergoing cardiopulmonary resuscitation (CPR) arriving from the catheterization laboratory in cardiac arrest precludes the usual anesthesia routine. Fortunately, such patients are indeed quite rare and even most patients who are "urgent" can have a complete anesthesia assessment in a matter of moments. The cardiac anesthesia workup should focus upon:

1. Identification and hospital protocols—All patients must be identified by at least two separate patient identifiers. Before anything else, the patient must be correctly identified and any hospital flow protocols carefully followed such as the World Health Organization checklist. Confirm perioperative antibiotic orders.

2. Routine anesthesia evaluation—All patients are asked the routine anesthesia questions regarding past personal and family anesthesia history, last oral intake, routine medications, allergies, etc.

3. Chart review—The patient's chart likely contains extensive information from their catheterization and echocardiographic studies. These should be carefully reviewed.

4. TEE—TEE is used routinely in most cardiac cases. The patient should be questioned about esophageal pathology, gastric bypass surgery, and difficulty swallowing to determine the safety of perioperative TEE examination.

5. Pulmonary history—Many patients presenting for cardiac surgery have a long history of lung disease usually secondary to smoking. Dyspnea in the cardiac surgery patient can be secondary to both cardiac and pulmonary dysfunction. The patient's history regarding the use of oral corticosteroids and bronchodilators is reviewed. Patients will require stress dose of corticosteroids perioperatively if steroids are a part of the patient's pulmonary regimen. Bronchodilators can be given perioperatively to decrease wheezing. Patients with lung disease may have pulmonary hypertension and impaired right ventricular function. Should the patient indicate a history of deep vein thrombosis, anti-fibrinolytic agents should be avoided.

6. Renal history—Patients with increased serum creatinine are at increased risk for acute renal failure perioperatively. Cardiac surgery can occasionally convert the non-dialysis renal failure patient into a dialysis dependent patient. Hypertension, acid-base imbalances, and hyperkalemia may all complicate the perioperative management of the renal failure patient undergoing heart surgery. Dialysis dependent patients are frequently dialyzed preoperatively rendering them relatively hypovolemic at the time of anesthesia induction. Postoperatively dialysis is often needed to remove excessive fluid and potassium acquired during cardioplegia administration.

7. Hepatic disease—The patient's alcohol-and other substance abuse–related history is obtained so to determine both the possibility of cross-tolerance to anesthetic agents or postoperative alcohol withdrawal syndrome. Patients with a history of hepatic failure are at risk for coagulopathy, ascites, portal hypertension and varices, encephalopathy, arterio-venous shunting, and hepatorenal syndrome. The diseased liver may be sensitive to perioperative hypoperfusion leading to "shock" liver postoperatively.

8. Hematological disorders—There are a variety of hematological conditions which can complicate cardiac surgery. Close coordination with the patient's hematologist in the preoperative period is critical to minimize the impact of these conditions on the patient's perioperative course. Hemophilia A is an X-linked recessive disorder leading to reduced factor VIII pro-coagulant. Hemophilia B is similarly an X-linked recessive disorder leading to decreased factor IX. The hematologist through perioperative factor replacement manages these conditions. Von Willebrand disease is associated with a decrease in von Willebrand factor and decreased platelet adhesion. DDAVP (1-deamino-8-D-arginine vasopressin) in a dose of 0.3 μg/kg can be administered to increase circulating von Willebrand factor perioperatively. Patients taking Coumadin undergoing emergency cardiac surgery are likely to bleed perioperatively. Fresh frozen plasma and vitamin K can be administered to attempt to normalize the patient's international normalized ratio (INR). Deficiencies in protein S and protein C as well as factor V Leiden put the patient at risk for hypercoagulability. Heparin-induced thrombocytopenia prevents the use of heparin perioperatively complicating the management of cardiopulmonary bypass. Sickle cell disease places the patient at risk of sickling crisis during hypothermia and periods of hypoxemia. Exchange transfusion is often necessary to reduce the amount of hemoglobin S in the blood or the surgery should be performed off-pump when amenable. Irrespective of the nature of the patient's hematological condition close coordination between the anesthesiologist, surgeon, and hematologist is critical. Lastly, patients for a variety of reasons often refuse blood product transfusion. Such refusal must be clearly documented prior to taking the patient to surgery and alternative modalities of blood salvage should be discussed.

9. Neurological history—Many patients have combined carotid and coronary artery disease or a history of previous strokes or other neurological injuries. If a patient's neurological function is in anyway impaired preoperatively it will certainly not be improved postoperatively. Consequently, it is imperative to document the patient's mental status, motor function, and pupil size preoperatively as a baseline to be compared against any postoperative deterioration. Regrettably, there are many sources of postoperative neurological dysfunction including embolization, hypoperfusion, and inflammation which can lead to both overt stroke and cognitive dysfunction.

10. Physical examination—A routine anesthesia examination is performed. The airway is assessed and locations for vascular access and invasive monitoring examined. The lungs are auscultated to identify any new wheezing or heart failure. The carotids are examined for signs of bruits—although in general this will have been done by the cardiologist and surgery staff preoperatively.

11. Laboratory/ECG review—Routine labs are reviewed. In particular the patient's blood glucose is noted, as blood glucose control by regular insulin infusion is often necessary perioperatively. Baseline electrolytes especially potassium, calcium, and magnesium are noted. Patients on diuretic therapy may have baseline hypokalemia; however, often at the end of surgery the potassium concentration is increased secondary to the delivery of potassium-rich cardioplegia solutions during cardiopulmonary bypass. Serum calcium measures are dependent upon the patient's albumin concentration and are of limited use. Ionized calcium concentrations are measured perioperatively. It may decrease transiently during cardiopulmonary bypass only to generally be restored to baseline following the bypass run. Magnesium replacement is often needed postoperatively and its baseline concentration should be noted. Other routine lab values are screened relating to platelet count, coagulation, hemoglobin concentration, and liver and renal function. The baseline ECG is reviewed and the patient's baseline rhythm noted.

Patients presenting for any type of cardiac surgery by their very nature are unstable. As such they can deteriorate, arrest, stroke at any point in the time up to the induction of anesthesia (and certainly afterward—see Chapter 4). It is critically important that such patients be carefully monitored during the entire time they are under the care of the anesthesia team. Consequently, the authors do not routinely administer oral pre-medications to patients awaiting surgery. It is often said that the best pre-medication is a caring anesthetist at the patient's bedside answering their questions and allaying their fears. When that does not work, small amounts of intravenous midazolam can be employed (0.5-2.0 mg IV) in the holding area assuming the patient is monitored and the anesthetist is present at the patient's bedside. Patients with critical aortic stenosis as well as those with severely impaired ventricular function are best not medicated at all until such time as the induction of anesthesia. Whenever any pre-medication is given a plan for monitoring and resuscitating, the patient should be prepared in advance.

However, overly anxious patients might become tachycardic leading to myocardial ischemia. Most patients will be treated with beta-blockers as a part of their medical regimen, thus reducing the incidence of sinus tachycardia preoperatively. Should beta blockade be inadequate and thought needed, small doses of short–acting beta-blockers (eg, esmolol) can be administered. Supplemental oxygen should be provided to all patients preoperatively.