Patients with diastolic pressures higher than 110 mm Hg or systolic pressures higher than 180 mm Hg should receive medication to control their hypertension before surgery. Beta-blockers may be particularly effective agents for treatment of preoperative hypertension (179). Chronically hypertensive patients are very susceptible to intraoperative hypotension because of impaired autoregulation of blood ﬂow to the brain and require a higher mean arterial pressure to maintain adequate perfusion (209). During induction of anesthesia, episodes of hypertension occur, and such episodes are seen more frequently in patients with baseline hypertension.
Postoperative hypertension is usually treated parenterally because gastrointestinal absorption may be diminished, and transdermal absorption can be erratic in patients who are cold and rewarming. Commonly used parenteral antihypertensives are listed in Table 22.19.
Increasing numbers of patients undergo coronary revascularization procedures, otherwise known as coronary artery bypass grafting, or percutaneous coronary intervention, typically stent placement. With the evolution of bare metal and drug-eluting stents, perioperative management of cardiovascular thrombotic risk versus perioperative bleeding and mortality is challenged. Given that drug-eluting stents generally require 12 months’ treatment with dual agent aspirin and thienopyridine (i.e., clopidogrel), the American College of Cardiology and American Heart Association (ACC/AHA) guidelines recommend avoiding elective surgery within 12 months of drug-eluting stent placement. When surgery cannot wait, the ACC/AHA recommends continuation of aspirin perioperatively, discontinuation of thienopyridine 5 days prior to surgery, and resuming it as soon as possible postoperatively. Ultimately the risk of perioperative morbidity secondary to bleeding must be weighed against the risk of repeat thrombosis and cardiovascular morbidity and mortality. If a patient requires new placement of a cardiac stent and requires a
Table 22.19 Common Parenteral Antihypertensives
Hemodynamic Monitoring Hemodynamic monitoring is integral to the perioperative management of patients with cardiovascular and pulmonary diseases. The major impetus for this advancement resides in the need for the quantitative estimate of cardiac function, resulting in the development of bedside pulmonary artery catheterization. The impact of monitoring cardiac function is demonstrated by the significant reduction of myocardial infarctions in high-risk patients who are aggressively monitored for 72 to 96 hours postoperatively (175).
Before the development of the pulmonary artery catheter, central venous pressure (CVP) measurement was used to assess intravascular volume status and cardiac function. To measure the CVP, a catheter is placed in the central venous system, most frequently the superior vena cava. A water manometer or a calibrated pressure transducer is connected to the CVP line, allowing an estimation of right atrial pressure. Right atrial pressure is determined by the balance between cardiac output and venous return. Cardiac output is determined by heart rate, myocardial contractility, preload, and afterload. If the pulmonary vascularity and left ventricular function are normal, the CVP accurately reﬂects the left ventricular end-diastolic pressure (LVEDP). The LVEDP reﬂects cardiac output or systemic perfusion and was considered the standard estimator of left ventricular pump function. Venous return is determined primarily by the mean systemic pressure, which propels blood toward the heart, balanced against resistance to venous return, which acts in the opposite direction. If right ventricular function is normal, the CVP accurately reﬂects intravascular volume.