Chapter 63: Hemoptysis

INTRODUCTION AND EPIDEMIOLOGY

Hemoptysis is the expectoration of blood from the lungs or tracheobronchial tree. Severity ranges from mild to severe, and it can be difficult to stop. The challenge is to stabilize the patient while simultaneously determining the source and providing treatment. Most cases of hemoptysis are mild and resolve spontaneously; predicting which individual will develop large-volume bleeding is difficult. Determining the cause, location, and extent of hemoptysis requires a multidisciplinary approach.¹

Assessing the amount of expectorated blood is difficult, because patients may either exaggerate or be unable to quantify the amount. The definition of "massive" or "severe" hemoptysis varies, with reported ranges from 100 mL per 24 hours to >1000 mL per 24 hours,^2,3 with a midpoint value of 600 mL per 24 hours accepted by many.⁴ However, because even small volumes of blood can cause asphyxiation, any hemoptysis requires prompt attention.⁵ Morbidity and mortality depend on the rate of bleeding, the ability of the patient to clear the blood, and the presence of underlying lung disease, which potentiates the effects of blood in the airways. We define "minor" hemoptysis as small-volume expectoration of blood in a patient with no comorbid lung disease, normal/stable oxygenation and ventilation, normal vital signs, and no risk factors for continued bleeding.

PATHOPHYSIOLOGY

Hemoptysis results from disruption of blood vessels within the walls of the airways, from trachea to bronchi, bronchioles, and the lung parenchyma (Table 63-1). The pulmonary arteries account for 99% of the arterial blood flow to the lungs but are a low-pressure system and rarely the source of hemoptysis. The bronchial circulation accounts for only about 1% of the arterial blood flow to the lungs but 90% of the cases of hemoptysis because it is a high-pressure system.⁶ The bronchial arteries typically branch off the thoracic aorta and are responsible for supplying oxygenated blood to the bronchi, pulmonary arteries and veins, and lung parenchyma. They follow the course of bronchi along their tortuous paths. Once the bronchial arteries reach the level of capillaries, three anastomoses occur: the larger bronchial arteries can merge directly with the alveolar microvasculature; the smaller bronchial arteries can merge with the veins of the pleural and pulmonary drainage system; and bronchial capillaries can merge directly with pulmonary capillaries.⁷ These connections produce a physiological right-to-left shunt comprising 5% of the total cardiac output.