Continuing Education Activity

Patients with pulmonary hypertension require special anesthetic considerations when undergoing anesthesia and surgery because of their increased morbidity and mortality. The anesthesiologist needs to understand the disease process to avoid potential complications, including myocardial infarction, respiratory failure, and death. This review focuses on the preoperative evaluation for patients with pulmonary hypertension and the appropriate intraoperative monitoring and ventilator management, pain control, and pharmacologic therapies for non-cardiac surgery.

Objectives:

• Review the preoperative evaluation needed for patients with pulmonary hypertension.
• Discuss options for intraoperative monitoring.
• Review some potential complications of pulmonary hypertension.
• Summarize the pharmacologic therapies prescribed by the interprofessional team both in and out of the operating room.

Introduction

The pulmonary vasculature system is normally a low-pressure, low resistance circuit. Pulmonary hypertension is classified as a mean pulmonary artery pressure greater than or equal to 25 mmHg at rest and is definitively diagnosed by right heart catheterization.[1][2] It is caused by a combination of physiologic changes, such as vascular proliferation, arteriolar vasoconstriction, left heart disease elevating pulmonary venous pressure, and in-situ thrombosis. Over time, the consistently elevated pulmonary pressures begin to increase the right ventricular afterload, leading to right ventricular hypertrophy and ultimately dysfunction.[3]

Patients with pulmonary hypertension with or without right ventricular heart failure have significantly increased morbidity and mortality when undergoing anesthesia and surgery. The stress of the surgery can exacerbate pulmonary hypertension and lead to potential complications, including arrhythmias, congestive heart failure, myocardial ischemia, postoperative respiratory failure, hemodynamic instability, delayed extubation, and longer length of stay in the ICU and overall hospital admission.[4][5] 

A patient with pulmonary hypertension presents a challenge for the anesthesiologist. In addition to having an in-depth understanding of the pathophysiology, the anesthesiologist must optimize blood pressure with vasodilators or vasopressors, oxygenation, and ventilation, avoid exacerbating factors, and control pain throughout the procedure to help achieve the best perioperative outcomes.[6] 

This review article will discuss the general considerations for perioperative anesthesia management for patients with pulmonary hypertension with or without subsequent right heart ventricular failure that are undergoing non-cardiac surgery.

Function

Preoperative Evaluation: The preoperative evaluation should include a thorough history and physical exam. It is not uncommon for patients to have undiagnosed pulmonary hypertension on the day of surgery. Patients with mild pulmonary hypertension may complain of generalized fatigue, whereas patients with more severe disease complain of angina, near syncope, and syncopal episodes. Physical exam findings correlating with right ventricular dysfunction are distended neck veins, tricuspid regurgitation, S3 gallop, hepatomegaly, abdominal ascites, and peripheral edema. If the patient presents with dyspnea at rest, syncope, or hypoxemia on the day of surgery, it should be rescheduled if it is not emergent. Additionally, a right heart catheterization should be considered if the patient has known severe disease or new evidence of right heart dysfunction.[4][7][8]

Preoperative labs and imaging are beneficial for knowing the current status of the patient’s disease and developing an anesthetic plan. A hemoglobin and hematocrit, comprehensive metabolic panel to assess renal and liver function, an electrocardiogram, echocardiogram, and chest radiograph should be obtained and reviewed.[5] For patients with unknown disease status, pulmonary function testing and arterial blood gas should be considered.[4]

The anesthesiologist needs to be familiar with the procedure, especially those with increased risk to the patient. For example, insufflation during laparoscopic procedures can increase abdominal pressure high enough to impede lung compliance or decrease venous return. It may also precipitate a respiratory acidosis that requires increasing minute ventilation or sodium bicarbonate to correct.[6] 

Orthopedic procedures utilizing cement may produce profound hypotension requiring immediate action. They also have an increased risk for fat or cement emboli.[4] Before proceeding, if not an emergent case, the surgery team needs to consider the risk-benefit ratio, and the anesthesiologist needs to verify that he or she has the available tools to manage acute right ventricular failure should it occur.[6] Patients should be medically optimized to lower pulmonary vascular resistance and improve right ventricular function prior to surgery if possible.

Intraoperative Monitoring: The American Society of Anesthesiologists recommends that a pulse oximeter, electrocardiography, blood pressure device, and temperature monitoring should be applied for all surgical cases. Additional and more invasive monitoring may be required for patients with multiple or advanced comorbidities. With pulmonary hypertension, an indwelling arterial catheter can be inserted to provide continuous systemic blood pressure monitoring as well as access for arterial blood gas samples. The arterial line allows for quick intervention and determining the appropriate ventilatory management.[2] 

A central venous catheter with a pulmonary artery catheter should be placed to monitor central venous and pulmonary artery pressures and targeted therapy for vasopressors, vasodilators, and fluids. Transesophageal echocardiography (TEE) can be used to evaluate the right ventricle. The mid-esophageal four-chamber view is ideal for measuring the dimensions of the right ventricle. A right ventricle that is volume overloaded will shift the septal wall to the left during diastole, causing the left ventricle to look like the letter “D.” If the right ventricle is pressure overloaded, it shifts the septal wall during systole.[8] TEE can also be utilized to calculate the pulmonary artery pressure and evaluate volume status.[5][6]

Induction: General anesthesia is a common anesthetic approach for patients with pulmonary hypertension. Peripheral nerve blocks and/or epidurals are helpful for perioperative pain control. Uncontrolled pain can be a trigger for a pulmonary hypertension exacerbation. Spinal anesthesia should be avoided because of the rapid onset and profound sympatholytic effects.[6] 

Prior to induction, the patient should be pre-oxygenated with 100% oxygen to increase their functional residual capacity and avoid hypoxemia. Etomidate, a quick onset sedation agent, is ideal for induction because it minimally affects cardiac function and systemic vascular resistance and is generally well tolerated with pulmonary hypertension. Intravenous or nebulized treatments with prostanoids or nitric oxide can be given to minimize pulmonary hypertensive responses to intubation.[6] A rapid sequence induction with an experienced provider is preferred. If laryngoscopy is attempted before achieving a deep level of anesthesia, it may cause intense sympathetic stimulation and worsen the patient’s pulmonary hypertension.[4] 

Adding a benzodiazepine and/or opioid during induction will help decrease a sympathetic response.[6] The overall goals are to avoid changes in preload, systemic vascular resistance, and contractility in order for the right ventricle to maintain cardiac output.[3]

Ventilation: Once the airway is secured, the anesthesiologist may begin ventilator management and use volatile inhaled anesthetics to maintain anesthesia. It is preferred to begin with low tidal volumes, 6 ml/kg, and keep peak airway pressures under 30 mmHg.[6] Ventilator settings should include a higher fraction of inspired oxygen, hyperventilation if necessary to maintain partial pressure of exhaled carbon dioxide between 30 to 35 mmHg, and positive end-expiratory pressure (PEEP), ideally between 5 and 10 cm water.[4] Increase the fraction of inspired oxygen rather than PEEP to improve oxygenation because increasing levels of PEEP will begin to compromise preload and cause systemic hypotension. One-lung ventilation should be avoided if at all possible. Blood flow decreases to the non-ventilated lung, causing an acute exacerbation of pulmonary hypertension due to hypoxic pulmonary vasoconstriction.[6]

Medications: Pharmacologic therapies for pulmonary hypertension continue to emerge. The vasodilator drugs that are widely used for treatment are prostanoids, endothelin receptor antagonists, nitric oxide, and phosphodiesterase inhibitors.[9] 

Prostanoids mimic prostacyclins and produce vasodilation and inhibit platelet aggregation. Epoprostenol, an intravenous medication, has been shown to reduce mortality. Endothelin is a vasoconstrictor; therefore, endothelin antagonists help with vasodilation. They also have anti-inflammatory effects and decrease the proliferation of vascular smooth muscle.[10] These medications are only available in oral form and have shown improvement in hemodynamics and exercise capacity. Nitric oxide stimulates pulmonary vasodilation by stimulating guanylate cyclase and subsequently cyclic guanosine monophosphate (cGMP). Unfortunately, the effects are short because cGMP is rapidly degraded by phosphodiesterase. Continuously inhaled nitric oxide is commonly used in the perioperative period. Phosphodiesterase inhibitors, such as sildenafil and tadalafil, are more appropriate for chronic therapy and have shown benefits for patients with pulmonary hypertension due to left heart disease. However, there are no clear benefits for phosphodiesterase inhibitors in pulmonary hypertension due to chronic lung or thromboembolic disease.[11] 

If the patient was recently diagnosed with pulmonary hypertension, then sildenafil, a phosphodiesterase inhibitor, is a possible preoperative treatment to prevent pulmonary hypertension exacerbations.[3]

Issues of Concern

The anesthesiologist needs to balance blood pressure, fluid management, oxygenation, and acid-base physiology throughout the procedure. Unfortunately, even with the best efforts, complications may arise. These can include acute right heart failure, arrhythmias, systemic hypotension, and even death. With right heart failure, the right heart is not adequately pumping blood through the pulmonary vasculature and the left heart, decreasing cardiac output. It is managed by fluid administration, afterload reduction, and improved contractility.

If the patient has depleted intravascular volume due to excessive blood loss or insensible losses, the heart cannot maintain cardiac output because of inadequate right-sided filling pressures. In this situation, fluid administration would be appropriate to increase filling pressures and thus cardiac output. To reduce right ventricle afterload, first correct any hypercapnia, hypoxia, or acidemia present. If those are corrected and there is no improvement, then pulmonary vasodilators should be added. Lastly, improving right ventricle contractility with inotropic agents such as norepinephrine may be beneficial.[12] The most dangerous intraoperative complication from a pulmonary hypertension exacerbation is right ventricular failure causing persistent systemic hypotension.

Systemic hypotension is not well tolerated in these patients and needs to be aggressively treated with vasoconstrictors such as vasopressin or phenylephrine, an alpha one agonist. To avoid exacerbations, treatment with inhaled vasodilators such as nitric oxide or iloprost, a synthetic analog of prostacyclin PGI2, may be beneficial.[3]

The most common arrhythmias are supraventricular tachycardia, and they can trigger right heart decompensation. The goal is to restore sinus rhythm with either electrical cardioversion, radiofrequency ablation, or drug therapy such as amiodarone. If the patient undergoes a cardioversion or ablation without success, then rate control with beta-blockers or calcium channel blockers must be considered.[9]

Clinical Significance

Pulmonary hypertension, similar to chronic obstructive pulmonary disease, is a chronic and progressive disease that usually causes a delay in diagnosis and, therefore, treatment.[7] The incidence of patients presenting for surgery with treated or untreated pulmonary hypertension continues to increase worldwide. Recognizing symptoms during the preoperative evaluation and understanding how to formulate the safest anesthetic plan is crucial for anesthesiologists today because of the high morbidity and mortality rates.

Enhancing Healthcare Team Outcomes

Caring for a patient with pulmonary hypertension during the perioperative period is a team effort. The operating room is a high-stakes environment that forces people together from various training backgrounds and specialties. Multiple physicians, including the surgeon, anesthesiologist, pulmonologist, cardiologist, and intensivist, need to discuss the short-term and long-term care goals for the patient as well as potential challenges and complications. If the surgery is not emergent, it is ideal for the team to optimize the patient for surgery and begin patient education to help manage the disease long term. Although there may be patient frustrations about surgical delays, the medical team must maintain an open dialogue and assure the patient that their overall health and safety are of the utmost importance. 

When developing an anesthetic plan, talk with the pharmacist about the potential medications you may need during the surgery as they may not be easily accessible in the operating room or even available at the hospital. On the day of surgery, there needs to be clear communication between the anesthesia technicians, nursing staff, and anesthesiologist about special needs during the procedure, such as arterial blood gas draws. The nurses in the recovery unit should be reminded to watch for signs and symptoms of complications such as heart failure and respiratory compromise.

Overall, communication is important to ensure preparedness amongst all providers and patient safety.