Anesthetic considerations for a parturient with pulmonary hypertension

Bhavna Gupta; Kamna Kakkar; Lalit Gupta; Anish Gupta

doi:10.4103/TheIAForum.TheIAForum_28_17

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REVIEW ARTICLE

Year : 2017 \| Volume : 18 \| Issue : 2 \| Page : 39-45

Anesthetic considerations for a parturient with pulmonary hypertension

Bhavna Gupta¹, Kamna Kakkar², Lalit Gupta¹, Anish Gupta³
¹ Department of Anesthesia and ICU, Maulana Azad Medical College and Lok Nayak Hospital, New Delhi, India
² Department of Anesthesia and ICU, PGIMS, Rohtak, Haryana, India
³ Department of CTVS, AIIMS, New Delhi, India

Date of Submission	18-Aug-2017
Date of Acceptance	13-Oct-2017
Date of Web Publication	12-Dec-2017

Correspondence Address:
Dr. Bhavna Gupta
Maulana Azad Medical College, New Delhi
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/TheIAForum.TheIAForum_28_17

Abstract

Pulmonary hypertension is defined as persistent rise in mean pulmonary artery pressure of 25 mmHg or more with pulmonary occlusion pressure <15 mmHg. Most of the symptoms encountered in pulmonary hypertension overlap with that of normal pregnancy such as shortness of breath, weakness, fatigue, chest pain, syncope, and abdominal discomfort. Pulmonary hypertension in pregnant patients carries high mortality rates between 30% and 56% and is also the important cause of increased perioperative morbidity and mortality. Basic principles of management include maintaining right ventricular function and reducing pulmonary vascular resistance. Preoperative risk assessment and successful management of patients with pulmonary hypertension undergoing surgery are crucial and important and involve an understanding of the pathophysiology of the disease, analysis of preoperative and operative risk factors, thorough multidisciplinary planning, meticulous intraoperative management, and early recognition and treatment of postoperative complications. We searched PubMed and Google Scholar databases with the following key words: pulmonary hypertension, anesthesia concerns, and parturient female for literature search.

Keywords: Anesthesia, parturient female, pulmonary hypertension

How to cite this article:
Gupta B, Kakkar K, Gupta L, Gupta A. Anesthetic considerations for a parturient with pulmonary hypertension. Indian Anaesth Forum 2017;18:39-45

How to cite this URL:
Gupta B, Kakkar K, Gupta L, Gupta A. Anesthetic considerations for a parturient with pulmonary hypertension. Indian Anaesth Forum [serial online] 2017 [cited 2023 Jun 4];18:39-45. Available from: http://www.theiaforum.org/text.asp?2017/18/2/39/220555

Introduction

Pulmonary artery hypertension (PAH) is defined as persistent increase in mean pulmonary artery pressure (PAP) of 25 mmHg or more with pulmonary occlusion pressure <15 mmHg.^[1] Idiopathic or primary PAH is relatively rare and in other common forms is associated with HIV infection, drug exposure (fenfluramine), sleep apnea, chronic liver disease (especially portal hypertension), and collagen disorders (systemic lupus erythematosus, scleroderma).^[2] Pregnancy in women with PAH is known to be associated with significantly high mortality rates between 30% and 56%.^[1],[2],[3] The physiologic changes that occur during pregnancy and the peripartum period are poorly tolerated in these patients. Majority of maternal deaths occur during labor or within 1 month postpartum.^[2]

Symptoms of PAH include chest pain, cough, shortness of breath with or without features of right heart failure, which includes lower extremity swelling, dizziness, or syncope. The average age of diagnosis is 37 years and sometimes may be first manifested during pregnancy. Dyspnea is an initial symptom in 60% of individuals, but is present in 98% by the time of diagnosis. Presenting symptoms in patients with PAH are not specific, characterized by shortness of breath, weakness, fatigue, chest pain, syncope, and abdominal discomfort. Physical examination may reveal a split S₂ with a loud second component, right ventricular heave, tricuspid regurgitation murmur, prominent pulmonic component of the second heart sound with elevated jugular venous pulse, ascites, hepatomegaly, jugular venous distention, and peripheral edema.^{[1],[2],[3],[4]} We searched PubMed and Google Scholar databases with the following key words: pulmonary hypertension, anesthesia concerns, and pregnant female for literature search.

Pathophysiology of Pulmonary Hypertension

Pulmonary hypertension of different causes can lead to a final common pathway of “right ventricular strain or failure.” Right ventricle (RV) is a thin-walled structure that poorly tolerates acute increase in afterload. This is because right ventricular stroke volume decreases proportionately to acute increase in afterload, and it cannot acutely increase the mean PAP to more than 40 mmHg. The RV subsequently becomes dilated, which is in contrast to chronic pulmonary hypertension where RV hypertrophy is the main feature reflecting an adaptive mechanism. RV distention in turn results in increased oxygen consumption and reduction in contractility.^[5],[6]

Medical Management

General management

Pulmonary hypertension in pregnancy is a complex clinical entity that requires collaborative efforts between obstetricians, anesthesiologists, cardiologists, pulmonologists, and intensivists. General measures include advice on physical activity and supervised rehabilitation, psychological support, infection control, and birth control. Supportive measures include advice on anticoagulation, diuretics, and oxygen therapy. Oxygen administration has been demonstrated to reduce pulmonary vascular resistance in patients with PAH.^[6],[7],[8]

Fluid management

Fluid management is often challenging in these patients as they poorly tolerate both hypo- and hypervolemia. Unmonitored fluid challenges may further impair RV function and are not recommended. Transesophageal echocardiography (TOE) may be required in high-risk cases to determine tricuspid regurgitation or volume overload and the same can be reflected as rising “v” wave on a central venous pressure trace. In predominantly diastolic RV dysfunction patients, management involves diuresis or hemofiltration.^[8]

Vasodilators

Endothelin receptor blockers are the potent vasodilator drugs taken orally. Currently available drugs are bosentan, ambrisentan, and macitentan. All drugs in this group are considered to be teratogenic (Category X), and therefore if a PAH patient becomes pregnant, discontinuation of these drugs is mandatory. These agents have been associated with profound craniofacial, cardiovascular, and visceral malformations in the rat model ^[8]
Drugs acting via prostacyclin pathway – Intravenous epoprostenol or treprostinil, subcutaneous pump (treprostinil), or inhalation (iloprost) are the drugs which act via prostacyclin pathway.^[10] Both epoprostenol and treprostinil are classified as category B and iloprost as category C drug in pregnancy. Most of the published case reports describe initiating intravenous (IV) epoprostenol several weeks before or near the time of delivery. However, IV epoprostenol may inhibit platelet aggregation, so bleeding should be monitored particularly during delivery and in postpartum period. Nebulized iloprost (category C) has also been used with positive outcome although with limited evidence.^[9],[27]

Thromboprophylaxis or anticoagulation

According to the published literature, anticoagulant treatment is recommended in idiopathic PAH, heritable PAH, PAH due to the use of anorexigens (Recommendation Grade IIA), and PAH associated with other conditions (Recommendation Grade IIB).^[10] Pregnant patients have an increased risk of deep vein thrombosis that can cause pulmonary embolism and therefore the common practice is to give anticoagulation therapy, although no prospective studies have proved the efficacy of this treatment. Warfarin is known to be teratogenic; therefore, subcutaneous injection of enoxaparin (1 mg/kg twice daily) is recommended.^[10]

Nitric oxide

Nitric oxide (NO) by acting via cyclic guanosine monophosphate (cGMP) pathway causes vasodilatation and antiproliferation of the pulmonary vasculature. This effect is inhibited by phosphodiesterase Type 5 (PDE5) activity and therefore PDE5 inhibitors increase the concentration of cGMP and thus encourage the activity of NO and cause vasodilatation of the pulmonary vasculature. Currently available drugs are sildenafil and tadalafil, both taken orally.^[11] These drugs can be given during pregnancy (Category B). During labor and hospitalization, continuously inhaled NO can also be used to lower the pulmonary vascular pressure, but this treatment is not feasible outside the hospital. Sildenafil has a positive inotropic effect on the hypertrophic RV. Using sildenafil to treat PAH in pregnancy appears to be safe, but prolonged administration is associated with several adverse effects, such as rebound pulmonary hypertension after withdrawal and development of methemoglobinemia.^[11] Albackr et al. have used intraoperative NO to reduce pulmonary arterial systolic pressure and had successfully delivered a healthy neonate. Pulmonary pressures were controlled with nebulization of iloprost and sildenafil, and the patient was discharged on tablet sildenafil.^[12]

Vasoconstrictors, inotropes, and inodilators

Maintaining the gradient between aorta and RV is achieved using sympathomimetic and nonsympathomimetic vasopressors. Noradrenaline and vasopressin improve perfusion of the right coronary artery, reduce the pulmonary/systemic vascular resistance ratio, enhance right ventricular performance, and marginally improve cardiac output. The use of inotropes has a modest impact in reducing the overall mortality related to PAH, and their wide availability and ease of administration make this group of drugs very attractive for use in perioperative settings. Inodilators, such as the phosphodiesterase-3 inhibitors milrinone and enoximone, have been shown to be beneficial when compared with the conventional inotropic support only. It appears that the influence of phosphodiesterase-3 inhibitors on reducing pulmonary vascular resistance is more pronounced than the reduction in systemic vascular resistance. However, reduction in systemic vascular resistance can compromise right coronary artery blood flow in patients with severe PAH and therefore they should be administered cautiously.^[13]

Delivery and Anesthesia

Normal vaginal delivery is desired over cesarean section to minimize the risk of anesthesia exposure, less change in blood volume, less risk of infection, and to avoid fluid shifts and preferably should be done in left lateral position to avoid aorto-caval compression, but the disadvantages of vaginal delivery such as stress and pain are poorly tolerated in PAH. Sympathetic increase in blood pressure and pulse rate increases the load on the RV.

Lower segment cesarean section

The important benefit of cesarean section is that it is performed electively under optimal conditions, thus avoiding prolonged stress and pain. It also cut shorts the second stage of labor and the adverse effects of bearing down.^{[11],[12],[13],[14],[15],[16]}

Preoperative Evaluation

The preoperative evaluation of a patient with established pulmonary hypertension is based on a risk assessment that takes into account their functional state, severity of the disease, and type of surgery proposed. A detailed history and physical examination should be complemented with relevant investigations. Patients' symptoms range from general fatigue, dyspnea, and chest pain on exertion to syncope in advanced PAH. Syncope is an ominous sign and in most cases is related to the inability to increase cardiac output on exertion and places the patient in the advanced functional class. New York Heart Association functional class at diagnosis is an important predictor of survival in patients with PAH and improvement from functional class 3/4–1/2 with treatment is associated with a better prognosis.^{[1],[2],[3],[4]}

Preoperative investigations

In addition to a detailed history taking and clinical examination, the following investigations are required:^{[17],[18],[19],[20]}

Electrocardiogram (ECG): Typical ECG findings include right-axis deviation, right bundle branch block, right ventricular hypertrophy, and tall R waves in leads V1 and V2. Right atrial hypertrophy and “P-pulmonale” may be present in severe pulmonary hypertension, with peakedPwaves, usually in leads II, III, aVF, and V1
Chest radiograph (with abdominal shield) for heart size, pulmonary congestion, lung consolidation, and pleural effusions. Enlargement of the main pulmonary artery and a globular heart shape with loss of the retrosternal airspace from right ventricular dilation can be seen on a chest radiograph
Echocardiography to evaluate and monitor regional and global ventricular function, valve structure and function, pericardial effusion, and mechanical complications of myocardial infarction (MI). The most usual echocardiographic sign of RV dilatation is the loss of its typical triangular shape. Right ventricular size can also be assessed by calculating the RV/left ventricular (LV) end-diastolic area ratio in the four-chamber view. A normal ratio is below 0.6. When the RV is larger than the LV, the RV is defined as severely dilated. Another specific sign of RV failure is the paradoxical septal motion in systole with shifting to the left ventricle (D-shaped septum), reflecting RV overload ^[18]
Blood tests: Full blood count, coagulation screen, C-reactive protein, serum creatinine and electrolytes, glucose, and liver function tests in all patients are required. Troponin, creatine phosphokinase-MB, and brain natriuretic peptide levels may assist in confirming the diagnosis and allow an estimation of severity in heart failure and MI
Lung ultrasonography may be integrated into bedside evaluation as an adjunct to the standard chest radiograph and computed tomography scan. Lung ultrasonography may help differentiate the causes of pulmonary hypertension in critical care and minimize radiation exposure in pregnant patients.^[19]

Monitoring During Anesthesia

Noninvasive monitoring

Routine standard monitoring includes ECG, pulse oximetry, end-tidal carbon dioxide, noninvasive blood pressure, and temperature measurement.^[19]

Invasive arterial monitoring can help detect early changes of hemodynamic instability and simultaneously allow to take blood gas samples to check adequate ventilation. Intraoperative monitoring with TOE and/or a pulmonary artery catheter should be considered in all patients with severe PAH or mild-to-moderate PAH with the existing right-sided heart failure. Monitoring with TOE allows continuous measurement of systolic PAP, valuable information on right ventricular performance, and guidance for fluid management. However, several factors limit the routine use of TOE; the image acquisition and interpretation of findings are dependent on the operator's training and personal experience, and the probe is not well tolerated in awake patients undergoing regional anesthesia.^[18],[20]

The intraoperative use of a pulmonary artery catheter is controversial. Many studies have failed to demonstrate any benefit in its use for intraoperative monitoring; however, in most of the studies, a pulmonary artery catheter was used for measurement and guiding optimization of cardiac output and LV end-diastolic pressure. Ronald B George et al. have seen critical arrhythmias during the use of pulmonary artery catheterization in a case of severe PAH.^[21]

Anesthetic Considerations

Both regional and general anesthesia have been described in most cardiac conditions. Although there is no evidence to support any particular technique, cardiovascular stability is the goal. The aim is for gradual, careful introduction of general or regional anesthesia with invasive monitoring in place.^{[20],[21],[22]}

Goals

Avoiding further increase in pulmonary vascular resistance (PVR)
Avoiding marked decrease in venous return
Avoiding marked reduction in systemic vascular resistance
Avoiding myocardial depression.

Perioperative anesthetic management and its goals

A variety of intraoperative events, both surgical and anesthetic, can affect the right ventricular oxygen supply–demand relationship. The transition from spontaneous breathing to intermittent positive pressure ventilation, addition of positive end-expiratory pressure (PEEP), patient positioning, and diaphragmatic compression can significantly increase right ventricular afterload and precipitate pulmonary hypertensive crisis. In addition to the pulmonary vascular effects of hypoxia and hypercarbia, patients may also be subjected to venous emboli arising from air, thrombi, or particulate matter forced into the circulation. Right ventricular contractility can be affected directly or indirectly by either depression from anesthetic drugs or acute changes in the sympathetic or parasympathetic balance. Patients with PAH have a high rate of perioperative morbidity and mortality. Mild pulmonary hypertension rarely affects anesthetic management, but moderate-to-severe disease increases the risk of right heart failure.^[23]

Patients may be treated with diuretics, anticoagulation, calcium channel blockers, supplemental oxygen, sildenafil (PDE inhibitor), endothelin receptor antagonists (e.g., bosentan), and prostanoids (e.g., iloprost, epoprostenol). Some of these drugs are given by continuous IV infusions, and even momentary interruption of therapy can be catastrophic. All drugs must be continued perioperatively. All attempts to reduce pulmonary hypertension prior to surgery should be performed, such as the administration of oxygen, bronchodilators, antibiotics, steroids to patients with obstructive lung disease, and vasodilators and inotropes to patients with cardiac disease. Patients receiving chronic therapy for pulmonary hypertension should continue on such therapy throughout the perioperative period. Patients on chronic prostacyclin (epoprostenol) or treprostinil infusions should have the infusion continued throughout the perioperative period, and management of hypotension should be with vasopressor therapy rather than with downward titration of the infusion. Patients on chronic inhaled iloprost should receive treatment prior to surgery. If they are unable to continue inhaled iloprost after surgery, consideration should be given to inhaled NO, nebulized iloprost, or IV or nebulized prostacyclin.^{[11],[22],[23]}

Intraoperative anesthetic management

Airway and ventilation

When using conscious sedation techniques, it is vital to ensure a patent airway and easy access to it, in case ventilation becomes compromised. An adequate depth of anesthesia should be ensured before attempting laryngoscopy and tracheal intubation, as sympathetic stimulation has deleterious effects on right ventricular afterload. Hypercarbia, acidosis, high inspiratory pressures, and high levels of PEEP should also be avoided.

Circulation

In general, patients with PAH have low systemic arterial pressures as a result of both their disease and specific medical therapy, rendering them susceptible to decompensation. The goal is to maintain the preanesthetic hemodynamic condition. Therefore, invasive monitoring before induction is often required. Permissive hypotension is not applicable to high-risk patients; in contrast, the use of a low dose of vasoconstrictor to compensate for the reduction in systemic vascular resistance caused by anesthetic drugs is a safe and effective approach.^[23]

Intravenous anesthetic agents

Etomidate is an ideal agent for induction of general anesthesia, and a balanced maintenance technique is generally tolerated in patients with pulmonary hypertension. Propofol decreases right ventricular contractility whereas ketamine increases pulmonary vascular resistance. Fentanyl and sufentanil have minimal effects on pulmonary hemodynamics. Remifentanil produces minor pulmonary vasodilatation, which is mediated by histamine release. Merten et al. had used target controlled infusion of propofol and remifentanil for induction and they were successful in maintaining hemodynamic stability during and after intubation.^[24]

Similar to aortic stenosis, the goal is to maintain adequate preload, systemic vascular resistance, and contractility in order to allow the RV to maintain cardiac output; in addition, it is essential to prevent increases in PVR from hypoxia, hypercarbia, acidosis, agitation, pain, and hypothermia. Since hypotension can produce a rapid downward spiral, continuous blood pressure monitoring with an arterial catheter should be considered in all patients with significant PAH.

Inhalational anesthetic agents

Inhalational anesthetics such as isoflurane and desflurane have a marked dose-dependent effect in reducing right ventricular contractility and some negative impact on right ventricular afterload; hence, they significantly impair RV pulmonary artery coupling. Sevoflurane causes significant depression of global right ventricular function associated with a qualitatively different effect on inflow and outflow tracts, without any modification of pulmonary vascular resistance. The use of nitrous oxide should be restricted because it increases pulmonary vascular resistance.^[25]

Central Neuraxial Blockade

Epidural anesthesia is slow in onset, about 15–20 min, but usually allows hemodynamic stability to be maintained.^[16] Conversely, the onset of spinal anesthesia is rapid, usually within 1–2 min, and the sudden associated peripheral vascular dilatation may lead to significant systemic hypotension requiring immediate intervention. Sen et al. have used epidural anesthesia in a patient with multivalvular disease with severe pulmonary hypertension with good maternal and fetal outcome.^[26] Similarly, Mishra et al. have used segmental epidural anesthesia in a case of severe pulmonary hypertension due to uncorrected Tausig Bing anomaly with uncorrected transposition of great vessels.^[27] Although central neuraxial blockade has been used safely in patients with PAH, blocking cardiac sympathetic fibers in the upper thoracic region disrupts right ventricular homeometric autoregulation. Homeometric autoregulation is an adaptive mechanism that allows the RV to tolerate acute increases in afterload but preserves the mechanical coupling between RV and the pulmonary circulation. When inhibited (e.g., by central neuraxial blockade), it can lead to a critical reduction in cardiac output and right heart failure that is not due to impaired right ventricular coronary flow dynamics or systemic vasodilation. Duggan and Katz have used combined spinal–epidural anesthesia for cesarean section with a multidisciplinary approach.^[28] The major advantage the obstetric anesthesiologists find in using the subarachnoid block is the rapidity of action, but at the cost of causing hemodynamic instability. Epidural anesthesia provides better hemodynamic stability and prevents the adrenergic response seen during general anesthesia associated with intubation which can be deleterious in patients with severe pulmonary hypertension. Epidural anesthesia is widely used for providing labor analgesia and the same can be used in case of emergency lower segment cesarean section and for postoperative pain relief. Oxytocin bolus should be avoided due to tachycardia and hypotension in most cases. Continuous infusion is preferred. Ergometrine should be avoided in severe cardiac disease, as it leads to vasoconstriction and hypertension and increases the risks of MI and pulmonary edema.

Postnatal Care

There should be a robust plan for pain management, including regional blocks and nonopioid medications. Multimodal analgesia should be the norm and patients should be given adequate analgesia using patient-controlled IV analgesia or epidural analgesia.

The majority of deaths among pregnant patients with PAH occur in the peripartum period, mainly within the 1^st month after delivery. During delivery, both systolic and diastolic blood pressures increase markedly during contractions because of compression of the abdominal aorta by the uterus, resulting in an increase in peripheral vascular resistance. Furthermore, temporary increase in venous return due to relief of caval compression and the additional blood shifting from the contracting uterus into the systemic circulation result in additional hemodynamic stress, leading to increased pulmonary hypertension and refractory right heart failure. Pulmonary embolism risk also continues after delivery, therefore careful monitoring of the patient and supportive treatment is needed to prevent the development of right heart failure.

Postoperative clinical deterioration and death are due to fluid shifts, pulmonary vasoconstriction, arrhythmias, and pulmonary thromboembolism. Respiratory failure (60%) and right ventricular failure (50%) are the most frequent contributing causes to death. Atrial tachyarrhythmias are associated with right ventricular failure and death. Beta-blockers should be avoided as they are poorly tolerated in these patients and amiodarone would be the drug of choice. In patients in whom sinus rhythm cannot be restored, digoxin should be considered for rate control. Postsurgical complications such as bleeding and infection must be promptly controlled and treated. Right ventricular function in PAH is “preload dependent,” but at the same time, fluid overloading is detrimental. Maintenance of systemic pressures with vasopressors and inotropes, along with replacement of blood volume when necessary, is of paramount importance. Vasodilator therapies that were started intraoperatively must be continued and slowly transitioned back to the patient's preoperative state.^[5],[21]

Conclusion

Pulmonary hypertension in a parturient female carries increased morbidity and mortality. There are a lot of advancements in the recent years regarding understanding of pathophysiology and management of pulmonary hypertension using multidisciplinary approach leading to improvement of maternal and fetal survival and outcome. Preoperative risk assessment and successful management of patients with pulmonary hypertension undergoing surgery involve an understanding of the pathophysiology of the disease, screening of at-risk patients, and analysis of preoperative and operative risk factors. Thorough multidisciplinary planning, careful intraoperative management, and early recognition and treatment of postoperative complications are key elements to decrease morbidity and mortality.

.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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