Systemic and pulmonary arterial hypertension

Lifestyle modification

Lifestyle modifications of proven value in lowering blood pressure include weight reduction, moderation of alcohol intake, increased aerobic exercise, and smoking cessation. There is a continuous relationship between increased body mass index (BMI) and blood pressure, with waist-to-hip ratio as an even stronger correlate. Weight loss is an effective nonpharmacologic intervention, through direct blood pressure reduction and synergistic enhancement of antihypertensive drug therapy efficacy. Overweight adults should aim for ideal body weight but can expect a 1 mm Hg reduction in blood pressure for every 1 kg of weight loss. Excessive alcohol consumption can be associated with increased hypertension and may cause resistance to antihypertensive drugs. Even modest increases in physical activity are associated with blood pressure decrease.

Dietary potassium and calcium intake is inversely related to both hypertension and cerebrovascular disease in the general population. Salt restriction (e.g., Dietary Approaches to Stop Hypertension [DASH] eating plan) is associated with small but consistent decreases in systemic blood pressure. Sodium restriction may be most beneficial in lowering blood pressure in blacks, older adults, diabetics, or those with metabolic syndrome, patient populations with low renin activity that, in total, constitute nearly half of all adults in the United States. Recent findings challenge previous views on salt restriction and improvement in blood pressure or cardiovascular symptoms.

Pharmacologic therapy

With continual research regarding the physiology and public health implications of hypertension, as well as identification of new cellular and molecular targets for pharmacologic intervention, treatment guidelines remain fluid. It is clear, however, that optimal drug therapy needs to consider ethnicity, advanced age, comorbidities, and end-organ function. The most recent evidence-based guidelines for the management of high blood pressure in adults (the ACC/AHA guidelines of 2017) outlined several broad conclusions:

• 1.

  Out-of-office blood pressure measurements are recommended for the diagnosis of hypertension and titration of antihypertensive medications.

• 2.

  There is strong evidence to support treating patients with ischemic heart disease, cerebrovascular disease, chronic kidney disease, or with an elevated risk of atherosclerotic cardiovascular disease with blood pressure–lowering medications if systolic blood pressure is 130 mm Hg and above. The recommendation of treating a diastolic blood pressure of 80 mm Hg and above has more limited data but is strongly recommended.

• 3.

  There is limited data to support the ACC/AHA Class I recommendation to treat patients without elevated cardiovascular disease risk or cerebrovascular disease with nonpharmacologic therapy if systolic blood pressure is 130 mm Hg and above or diastolic blood pressure is 80 mm Hg and above (stage 1 hypertension) and with blood pressure–lowering medications if systolic blood pressure is 140 mm Hg and above or diastolic blood pressure is 90 mm Hg and above (stage 2 hypertension).

• 4.

  The same thresholds and goals are recommended for hypertensive adults with diabetes or nondiabetic chronic kidney disease as for the general hypertensive population.

• 5.

  ACE inhibitors, ARBs, CCBs, or thiazide-type diuretics are useful and effective in the nonblack hypertensive population, including those with diabetes.

• 6.

  In black adult hypertensives without heart failure (HF) or chronic kidney disease (CKD), including those with diabetes, there is moderate evidence to support initial antihypertensive therapy with a CCB or thiazide-type diuretic.

• 7.

  There is moderate evidence to support antihypertensive therapy with an ACE inhibitor or ARB in persons with CKD to improve kidney outcomes.

• 8.

  Nonpharmacologic interventions, including weight loss, sodium reduction, potassium supplementation, increased physical activity, and reduced alcohol consumption, are important components to a comprehensive blood pressure management approach.

As noted in the guidelines, first-line antihypertensive therapy consists of diuretics, CCBs, ACE inhibitors, and ARBs. Notably absent from first-line therapy are β blockers, which tend to be reserved for patients with coronary artery disease or tachydysrhythmia, or as a component of multidrug therapy in resistant hypertension. A wide range of antihypertensive drugs are in common use ( Table 9.5 ). A recent review noted that drugs in 15 different classes have been approved for the treatment of hypertension in the United States, many of which are also available in single-pill combinations with other compounds. Importantly, although all the available drugs can reduce blood pressure, their disparate pharmacology is evident in the reported relative risk reduction of hypertension-related events. For example, CCBs may lower the risk of stroke but not HF or mortality, whereas a Cochrane review found that in patients with uncomplicated hypertension, low-dose thiazides reduce mortality and cardiovascular morbidity. Nonetheless, across the range of hypertension etiology and severity, the varying pharmacology of available medications allows for combining drugs with different and potentially beneficial properties in terms of optimizing end-organ function ( Table 9.6 ). Despite the plethora of treatment options already available, the public health burden of hypertension continues to drive research into new pharmacologic targets and therapies, including vaccines and surgical interventions ( Table 9.7 ).

Treatment of secondary hypertension

Treatment of secondary hypertension is often interventional, including correction of renal artery stenosis via angioplasty or direct arterial repair, and adrenalectomy for adrenal adenoma or pheochromocytoma. For patients in whom renal artery repair is not possible, blood pressure control may be accomplished with ACE inhibitors alone or in combination with diuretics, although ACE inhibitors, ARBs, and direct renin inhibitors are not recommended in patients with severe bilateral renal artery stenosis as they can hasten progression to renal failure. Primary hyperaldosteronism in women can be treated with an aldosterone antagonist such as spironolactone, whereas amiloride is often used in men owing to the potential for spironolactone-induced gynecomastia. Certain disease entities, such as pheochromocytoma, require a combined pharmacologic and surgical approach for optimal outcome.

Preoperative evaluation

Assessment of blood pressure in the preoperative area or clinic is often complicated by an anxiety-related hypertensive response (white-coat hypertension). Furthermore, patients are often instructed to interrupt prescribed antihypertensives, such as ACE inhibitors and diuretics, on the day of surgery. Assessing blood pressure in a single moment in time does not give an accurate picture of overall blood pressure optimization and, according to current guidelines, multiple elevated blood pressure readings over time are necessary for a diagnosis of hypertension. Firstly, appropriate blood pressure technique should be confirmed, and, if still elevated, a pressure on the contralateral arm should be obtained. A careful review of prior clinic data, home blood pressure readings, and a thorough patient history are necessary to gain a better overall picture of cardiovascular health. Therefore, in general, elevated blood pressure per se is not a direct prompt to delay surgery in asymptomatic patients without other risk factors. In fact, unless there is marked hypertension (systolic >180 mm Hg and/or diastolic >110 mm Hg) or end-organ injury that can be ameliorated by aggressive blood pressure control, delaying surgery is not generally recommended.

While secondary hypertension is rare, suspicion of such should prompt a workup. A secondary etiology may be indicated by symptoms (e.g., flushing, sweating, palpitations suggestive of pheochromocytoma), physical examination (e.g., a renal bruit suggestive of renal artery stenosis), laboratory abnormalities (e.g., hypokalemia suggestive of hyperaldosteronism), or age (most hypertension in children <12 years of age is secondary). These patients often present as severely hypertensive with no prior diagnosis of hypertension, and they would be exception to the “no delay” approach to preoperative hypertension. In fact, there have been multiple reports of a pheochromocytoma being “diagnosed” by induction of general anesthesia for an incidental procedure.

Once the decision is made to proceed with surgery, it is now common practice to continue antihypertensive medications, with the possible exception of high-dose ARBs and ACE inhibitors. Some authors advocate discontinuing these drugs at least 10 hours prior to surgery owing to concerns about refractory hypotension. In contrast, others believe there is little direct association between chronic use of ARBs and ACE inhibitors and sustained hypotension and therefore support continuing these drugs up to the time of surgery, especially in ambulatory patients. In addition, cessation of β-adrenergic antagonists or clonidine can be associated with rebound effects. Interruption of CCBs is associated with increased perioperative cardiovascular events.

Intraoperative considerations

Although guidelines do not support delaying surgery for poorly controlled blood pressure, perioperative hypertension increases blood loss as well as the incidence of myocardial ischemia and cerebrovascular events. Furthermore, owing to a combination of physiologic factors (volume depletion, loss of vascular elasticity, baroreceptor desensitization) in combination with antihypertensive treatment, hypertensive patients are prone to intraoperative hemodynamic volatility. When superimposed on organ damage from chronic hypertensive disease, even brief periods of hypotension are associated with acute kidney injury, myocardial injury, and death. Ultimately, regardless of treatment efficacy at the time of surgery, hypertension as a disease entity has long been known to be an independent predictor for adverse perioperative cardiovascular events, especially when combined with other risk factors. Accordingly, clinicians need to consider acute intraoperative changes in blood pressure in the context of alterations in end-organ functional reserve brought about by chronic disease. Particular emphasis has been placed upon ischemic heart disease and the implications of left ventricular hypertrophy on cardiac relaxation and filling during diastole ( Fig. 9.2 ). Nevertheless, guidelines for optimal systolic and diastolic blood pressures and MAP are lacking and impossible to derive, as blood pressure itself provides little guidance about microvascular blood flow and resistance.

Induction of anesthesia and monitoring

As already noted, hypertensive patients can be hemodynamically volatile, with induction of anesthesia producing hypotension and subsequent laryngoscopy and tracheal intubation eliciting hypertension and tachycardia. To lessen this risk it has been suggested that placement of an intraarterial catheter followed by a multimodal induction that includes transient β blockade with esmolol may be beneficial. Poorly controlled hypertension is often accompanied by relative volume depletion, especially if a diuretic is part of chronic therapy. In some patients, modest volume loading prior to induction of anesthesia may provide hemodynamic stability, although this approach may be counterproductive in patients with marked left ventricular hypertrophy and significant diastolic dysfunction.

As with any procedure, a management plan for hemodynamic monitoring and vasoactive drug therapy for hypertensive patients should consider age, functional reserve, preoperative pharmacotherapy, and the planned operation. For example, intention-to-treat thresholds for patients undergoing repair of aortic dissection or women with peripartum hypertension will be lower than for the general surgical population. While arterial catheterization provides useful continuous information, the decision to use invasive monitoring is typically reserved for select patients based on magnitude of surgery, severity of disease, functional capacity, and comorbidities. Assessment of fluid status can be challenging in patients with long-standing hypertension, especially those with a history of heart failure with preserved ejection fraction (HFpEF). Left ventricular hypertrophy reduces chamber compliance such that with volume infusion, right heart pressures rise despite the fact that the left ventricle is relatively underfilled. Ultimately, intraoperative use of a pulmonary artery catheter is controversial, and pressure measurements from a central venous catheter may not provide a clear representation of volume status. Overall, echocardiographic evaluation of cardiac volumes may be the most useful in patients with HFpEF, but this has its own inherent risks and requires specialized personnel.

Maintenance of anesthesia

Achieving hemodynamic stability may be more important than targeting an arbitrary intraoperative blood pressure, especially given the influence of other comorbidities, surgical procedure and position, volume status, mechanical ventilation, and depth of anesthesia. The management of intraoperative blood pressure over the wide range of potential clinical scenarios is beyond the scope of this review. However, it is important to consider that although high-dose anesthetics can acutely control blood pressure in many patients, this approach can have side effects, slows emergence, and cannot be continued into the postoperative phase. Accordingly, addition of sympathomodulators (esmolol, metoprolol, labetalol) or titrated calcium channel blocker therapy (nicardipine or clevidipine) can facilitate transition from the operating room to postanesthesia care unit (PACU) or intensive care unit (ICU).