Pulmonary arterial hypertension

23 Pulmonary arterial hypertension




Overview/pathophysiology


As blood passes through the pulmonary vasculature, it exchanges CO2 and particulate matter for O2. Normally the pulmonary vascular bed offers little resistance to blood flow, but when resistance occurs, pulmonary pressures rise and pulmonary hypertension results. Pulmonary arterial hypertension (PAH) can be idiopathic (rare), which has a poor prognosis and affects primarily young and middle-age women; or it can be secondary (most common), which often responds to therapy and is found in a variety of medical conditions. The cause of idiopathic pulmonary arterial hypertension (IPAH) is unknown. It may be familial and has been linked to the bone morphogenetic protein receptor 2 (BMPR2). The underlying cause of secondary PAH often is chronic hypoxia, which can result from increased pulmonary blood flow from a ventricular or atrial shunt, left ventricular failure, chronic obstructive pulmonary disease (COPD) or sleep apnea, pulmonary embolus, interstitial lung disease, human immunodeficiency virus (HIV) infection, collagen vascular disorders such as scleroderma or lupus, portal hypertension due to liver disease, or any physiologic occurrence that increases pulmonary vascular resistance or constriction of the vessels in the pulmonary tree.



Health care setting


Primary care with possible hospitalization in a medical-surgical unit resulting from complications or in a special center for heart-lung transplantation



Assessment




Acute indicators:


Exertional dyspnea and fatigue (the most common presenting symptoms), eventually progressing to dyspnea at rest. Syncope, precordial chest pain, and palpitations can occur because of low cardiac output or hypoxia.



Chronic indicators:


Signs of right or left ventricular failure as a result of right ventricular enlargement and eventual fluid overload.



Right ventricular failure:


Peripheral edema, increased venous pressure and pulsations, liver engorgement, distended neck veins.



Left ventricular failure:


Dyspnea; shortness of breath, particularly on exertion; decreased blood pressure (BP); oliguria; orthopnea; anorexia.



Physical assessment:


Cyanosis from decreased cardiac output with subsequent systemic vasoconstriction and ventilation-perfusion mismatch, systolic murmur caused by tricuspid regurgitation or pulmonary stenosis, diastolic murmur caused by pulmonary valvular incompetence, accentuated S2 heart sound, possible S3 or S4 heart sound, and a parasternal heave caused by right ventricular enlargement.



Diagnostic tests




Chest x-ray examination:


Will show enlargement of the pulmonary artery and right atrium and ventricle. Pulmonary vasculature may appear engorged.



Echocardiography:


Valuable for showing increased right ventricular dimension, thickened right ventricular wall, and possible tricuspid or pulmonary valve dysfunction. This test indirectly measures pulmonary artery systolic pressure.



Radionuclide imaging:


Equilibrium-gated blood pool imaging and thallium imaging assess function of the right ventricle.



Computerized tomography (CT) scan:


Evaluates diameter of the main pulmonary arteries, which is helpful in evaluating severity of disease. High-resolution CT can confirm the presence of interstitial lung disease. Spiral CT is more specific in evaluating pulmonary embolus.



Right heart catheterization:


Gold standard for diagnosing PAH. It also provides helpful information regarding severity of the disease and establishing prognosis. Pulmonary vascular resistance will be very high, and pulmonary artery and right ventricular pressures can approach or equal systemic arterial pressures. Vasodilator challenge is often performed to assess reactivity and guide treatment. Adenosine, epoprostenol, and nitric oxide typically are used.



Pulmonary perfusion scintigraphy (perfusion scan):


A noninvasive way to assess pulmonary blood flow. This study involves intravenous (IV) injection of serum albumin tagged with trace amounts of a radioisotope, most often technetium. The particles pass through the circulation and lodge in the pulmonary vascular bed. Subsequent scanning reveals concentrations of particles in areas of adequate pulmonary blood flow. Scan is normal in PAH. Abnormal scan suggests presence of thromboembolic pulmonary hypertension.



Electrocardiogram (ECG) results:


Will show evidence of right atrial enlargement and right ventricular enlargement (evidenced by right axis deviation, right bundle branch block, tall and peaked P waves, and large R waves in V1) secondary to the increased pressure needed to force blood through the hypertensive pulmonary vascular bed.



Pulmonary function test:


Results are usually normal, although some individuals will have increased residual volume, reduced maximum voluntary ventilation, and decreased vital capacity.



Sleep study:


Confirms diagnosis of sleep apnea as etiology for associated PAH.



Exercise testing:


Symptom-limited stress test or 6-min walk test can help assess severity of symptoms and guide response to treatment.



Arterial blood gas (ABG) analysis:


May show low Paco2 and high pH, which occur with hyperventilation, or increased Paco2 with decreased gas exchange.



Oximetry:


May show decreased O2 saturation (92% or less).



Blood tests to rule out secondary causes of PAH:


Anti-nuclear antibody, rheumatoid arthritis, erythrocyte sedimentation rate (tests for collagen vascular disorders), HIV, and thyroid-stimulating hormone (thyroid abnormalities commonly coexist with PAH).



Complete blood count (CBC):


Polycythemia can occur in the presence of chronic hypoxemia as a result of compensation.



Liver function tests:


May be abnormal if venous congestion is significant. Examples include increased aspartate aminotransferase (AST), alanine aminotransferase (ALT), and bilirubin.





Nursing diagnosis:


Impaired gas exchange

related to altered blood flow occurring with pulmonary capillary constriction


Desired Outcome: Patient has improved gas exchange by at least 24 hr before hospital discharge, as evidenced by O2 saturation greater than 92% (90% or greater for patients with COPD) and Pao2 80 mm Hg or higher.








































ASSESSMENT/INTERVENTIONS RATIONALES
Assess O2 saturation; report O2 saturation 92% or less to health care provider. Low O2 saturation may signal the need for oxygen supplementation.
Monitor ABG results. Report significant findings to health care provider. ABG results can reveal signs of hypoventilation (decreased Pao2, increased Paco2, and decreased pH), which can signal respiratory failure, or hyperventilation (low Paco2 and high pH), which can occur with anxiety or respiratory distress. Hypoxemia is the key gas deficit seen with pulmonary vascular vasoconstriction. Blood flow through the lungs is impaired, making it difficult to exchange O2 for CO2. O2 becomes low (hypoxemia) and CO2 becomes high (hypercarbia). Hypercarbia causes a change in pH to the acid side. Although initially respiratory in origin, hypoxemia eventually results in metabolic acidosis because of lactic acid production. Values outside of normal or acceptable range should be reported promptly for timely intervention.
Assess all lung fields for breath sounds q4-8h, or more frequently as indicated. Adventitious sounds (especially rales) can occur with fluid overload; diminished breath sounds are congruent with disease severity
Assess respiratory rate (RR), pattern, and depth; chest excursion; and use of accessory muscles of respiration q4h. Increased RR, abdominal breathing, use of accessory muscles, and nasal flaring are signals of hypoxia and respiratory distress.
Inspect skin and mucous membranes for cyanosis or skin color change. These color changes are significant and later signs of decreased gas exchange.
Assess mental status and report significant changes. Changes in mental acuity or level of consciousness (LOC) may be indications of hypoxemia or acid-base imbalance.
Assist patient into high Fowler’s position (head of bed [HOB] up 90 degrees), if possible. This position reduces work of breathing and maximizes chest excursion.
Teach patient to take slow, deep breaths. This promotes gas exchange.
Administer prescribed O2 as indicated. Oxygen treats hypoxia. It can be administered continuously or only at bedtime or with exercise when oxygen desaturation is most likely to occur. If hypoxia is severe, O2 is administered by mask.
Caution: Use care when administering O2 to patients with a history of COPD. High concentrations of O2 can depress the respiratory drive in individuals with chronic CO2 retention.
Deliver O2 with humidity. Humidity helps prevent oxygen’s drying effects on oral and nasal mucosa.
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Jul 18, 2016 | Posted by in NURSING | Comments Off on Pulmonary arterial hypertension

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