Various populations of patients have different cardiac physiology. Thus, a newborn with a heart rate of 120 to 160 beats per minute would be normal, while in a resting adult would be deemed abnormal. Anesthesiologists must, therefore, appreciate normal cardiac physiology as well pathophysiologic states. While cardiovascular physiology and the anesthesia considerations of the cardiovascular system are discussed in previous chapters, this section will focus on specific anesthetic considerations as applicable to the cardiovascular system.1
STRATIFICATION OF CARDIAC RISK
A key consideration in approaching anesthetic and perioperative care in patients with cardiovascular disease is stratification of risk. This involves elucidating a thorough preoperative history and physical examination, followed by cardiac testing to assess progression of disease, if necessary. Such tests include echocardiogram, Holter monitor, dobutamine stress echocardiogram, and angiogram.2–6 The American College of Cardiology (ACC) and American Heart Association (AHA) developed the ACC/AHA Guideline Perioperative Cardiovascular Evaluation for Noncardiac Surgery; however, it is important to note that there has been no proven benefit between either medical therapy or prophylactic invasive testing with coronary angioplasty with stenting or CABG.7,8 The POISE study, on prophylactic perioperative β-adrenergic blockade use, is still controversial.9 It is recommended to continue anti-ischemic drugs in the perioperative setting. It is also recommended to use β-adrenergic blockers in coronary artery disease (CAD) or peripheral vascular disease (PVD) patients, prophylactically in patients with significant cardiac risk (RCI 3 or more).10–13
ESSENTIAL HYPERTENSION CONSIDERATIONS
Essential hypertension (HTN) is defined as chronically high systemic blood pressure higher than 160 mm Hg or diastolic blood pressure greater than 90 mm Hg independent of a known disease cause. Essential HTN is a risk factor for coronary artery disease (CAD) and end organ damage.14–16
Preoperatively, drug therapy is used to control the extent of the disease, as well as control the effects of preoperative anxiety on the systemic arterial blood pressure. Intraoperatively, blunting the sympathetic nervous system response on the systemic arterial blood pressure to painful stimulus is a critical consideration. Antihypertensive drugs are continued throughout the entire perioperative period and signs of CAD must be assessed throughout. Intra-arterial catheter monitoring, which allows for beat-to-beat measures of blood pressure, is justified for use in significant surgical procedures where blood loss can be assessed and for patients with significant cardiovascular or systemic pathogenesis. It is important to note that these patients are at higher risk of cerebral or spinal cord ischemia in cases of lowered perfusion pressure, since cerebral and spinal cord blood flow is directly related to mean arterial pressure minus central venous pressure or intracranial pressure (whichever is larger). In this regard, autoregulation can be shifted with acidosis, history of HTN, and/or other factors. It is also important to assess renal dysfunction as this would affect the choice of drugs, especially given the effects of renal clearance of drug metabolites.