Pulmonary Hypertension in the Intensive Care Unit

Ana Cojocaru

Kimberly A. Fisher

I. INTRODUCTION

A. Pulmonary hypertension (PH), defined as a mean pulmonary artery pressure (mPAP) > 25 mm Hg, is a common finding in critically ill patients.

B. Decompensated right heart failure due to PH and requiring ICU admission is associated with a high mortality rate (32% to 41%).

II. CLASSIFICATION/ETIOLOGY

A. Classification: PH is classified into five groups based on similar pathology and response to treatment (Table 47-1). Grouping is based on the location of the primary abnormality.

B. Common etiologies of PH in the intensive care unit (Table 47-2).

1. Related to underlying critical illness.

a. Acute respiratory distress syndrome (ARDS).

i. Reported in 93% to 100% of patients with severe ARDS.

ii. Usually mild to moderate severity; 7% with ARDS have severe PH.

iii. Severity of PH correlates with degree of lung injury.

iv. Incidence of PH may have decreased with low tidal volume ventilation.

b. Acute pulmonary embolism.

i. Fifty percent obstruction of pulmonary vasculature must occur before PH occurs.

ii. PH may occur with lesser degree of pulmonary vascular obstruction in patients with underlying cardiopulmonary disease.

2. Decompensation of preexisting condition.

a. Left-sided heart failure.

b. Exacerbation of chronic hypoxemic lung disease (chronic obstructive pulmonary disease [COPD] or interstitial lung disease [ILD]).

3. Deterioration of chronic pulmonary arterial hypertension (PAH).

III. PHYSIOLOGY OF THE PULMONARY CIRCULATION AND RIGHT VENTRICLE

A. Normal pulmonary circulation.

1. Low-pressure and low-resistance vascular bed.

TABLE 47-1 Updated Clinical Classification of Pulmonary Hypertension

Group 1: pulmonary arterial hypertension (PAH)

Idiopathic PAH (IPAH)

Heritable

Drug and toxin induced

Associated with connective tissues disease, HIV infection, portal hypertension, congenital heart diseases, schistosomiasis, chronic hemolytic anemia

Persistent pulmonary hypertension of the newborn

Pulmonary venoocclusive disease and/or pulmonary capillary hemangiomatosis

Group 2: pulmonary hypertension owing to left heart disease

Systolic dysfunction

Diastolic dysfunction

Valvular disease

Group 3: pulmonary hypertension owing to lung disease and/or hypoxia

Chronic obstructive pulmonary disease (COPD)

Interstitial lung disease (ILD)

Other pulmonary diseases with mixed restrictive and obstructive pattern

Sleep-disordered breathing

Alveolar hypoventilation disorders

Chronic exposure to high altitude

Developmental abnormalities

Group 4: chronic thromboembolic pulmonary hypertension (CTEPH)

Group 5: pulmonary hypertension with unclear multifactorial mechanisms

Hematologic disorders: myeloproliferative disorders, splenectomy

Systemic disorders: sarcoidosis, pulmonary Langerhans cell histiocytosis, lymphangioleiomyomatosis, neurofibromatosis, vasculitis

Metabolic disorders: glycogen storage disease, Gaucher disease, thyroid disorders

Others: tumoral obstruction, fibrosing mediastinitis, chronic renal failure on dialysis

Modified from Simonneau G, Robbins IM, Beghetti M, et al. Updated clinical classification of pulmonary hypertension. J Am Coll Cardiol 2009;54:S43-S54.

2. Accommodates increases in cardiac output via dilatation and recruitment of previously closed vessels.

3. Thin-walled right ventricle (RV) able to accommodate large increases in volume (preload).

B. RV pressure overload.

1. Increases in afterload due to PH lead to proportionate decrease in RV stroke volume.

2. Decreased RV stroke volume reduces blood return to the left ventricle (LV), leading to decreased cardiac output.

TABLE 47-2 Common Causes of Pulmonary Hypertension in the Intensive Care Unit

Hypoxemia/parenchymal lung disease

Acute respiratory distress syndrome

Pulmonary embolism

Interstitial lung disease

Obstructive sleep apnea

Chronic obstructive pulmonary disease

Left heart disease

Acute myocardial infarction

Valvular disease (mitral regurgitation/mitral stenosis)

Severe diastolic dysfunction

Cardiomyopathy

Postoperative states

Coronary artery bypass grafting

Cardiac transplantation

Lung/heart-lung transplantation

Pneumonectomy

Thromboembolic lung disease

Pulmonary embolism

Deterioration of chronic pulmonary arterial hypertension

Infection

Fluid overloaded state

Arrhythmias

Pulmonary embolism

Acute on chronic pulmonary hypertension

Medication withdrawal

Modified from Zamanian RT, Haddad F, Doyle RL, et al. Management strategies for patients with pulmonary hypertension in the intensive care unit. Crit Care Med 2007;35:2037-2050.

3. Elevated RV end-diastolic pressure causes bowing of the interventricular septum toward the LV during diastole, preventing LV diastolic filling and further reducing cardiac output (“ventricular interdependence”).

4. Can open foramen ovale, causing hypoxemia due to right to left shunting of blood.

IV. DIAGNOSIS

A. Signs and symptoms.

1. Symptoms may be related to

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