Other Vasoocclusive Types of Crises

ACUTE CHEST SYNDROME/PULMONARY CRISIS Acute chest syndrome is characterized by signs and symptoms of acute lower respiratory tract disease—i.e., cough, chest pain (often pleuritic in nature), leukocytosis, tachypnea, dyspnea, and so on. All are usually accompanied by an infiltrate on chest x-ray (often the infiltrate takes 2 to 3 days to become apparent on a radiograph). The differential diagnosis includes acute chest syndrome/pulmonary infarction, pneumonia (bacterial or viral), and pulmonary thromboembolus. Pulmonary infarcted areas often become secondarily infected, leading to the acute chest syndrome. This is a major cause of mortality in sickle patients of all ages but especially in those above the age of 10. It accounts for about 15 percent of adult deaths and can be seen in about 30 percent of patients with sickle disease.

A standard chest/infiltrative disease workup is indicated with some notable variations. Arterial blood gases, complete blood count (CBC), and sputum analysis are certainly indicated. These patients should all be admitted to the hospital for supplemental oxygen therapy, pulmonary toilet, and empiric parenteral antibiotic therapy. The role and value of noninvasive pulse oximetry has been controversial. Some investigators believe that it accurately reflects arterial oxygen saturation, but others question the accuracy of the readings. It is clear, however, that some totally asymptomatic patients with sickle disease exhibit appreciable oxygen desaturation. This may be due to the abnormal sickle cell morphology of the red blood cell (RBC) and its spectrographic "reflection" on light plethysmography as measured by most standard pulse oximeters. The other issue is pulmonary angiography, which in general is to be avoided, since contrast material seems to cause more pulmonary sickling. A ventilation/perfusion (^Q) scan may be helpful, especially if a baseline scan is available for comparison. If a significant V/Q mismatch is discovered, heparinization may be indicated. The major concern is that multiple episodes of chest syndrome can result in pulmonary fibrosis and impair pulmonary function. Patients with multiple episodes often develop pulmonary hypertension and end-stage lung disease as young adults, hence the high morbidity and mortality rates. Any patient with significant cardiopulmonary decompensation should be considered for exchange transfusion therapy.

CEREBROVASCULAR DISEASE/CNS CRISIS Some 5 to 10 percent of children (15 to 25 percent in all age categories) with SCD have a clinically apparent cerebrovascular event, characterized by acute onset of hemiparesis, seizures, headaches, transient ischemic attacks, dizziness/vertigo, sensory hearing loss, cranial nerve palsies, paresthesias, and inexplicable coma. These crises tend to be painless but are abrupt in onset. Cerebral infarction is more common in children, while cerebral hemorrhage is more typical in adults. The overall rate of subarachnoid hemorrhage (SAH) is increased in sickle disease patients. CT scan, lumbar puncture, and magnetic resonance imaging (MRI) are all helpful.

RENAL CRISIS Like cerebrovascular crisis, renal vasoocclusive events are common but generally asymptomatic. Symptoms of renal infarction may include flank pain, renal colic, and costovertebral angle tenderness to percussion/palpation. Gross or microscopic hematuria may be evident, and some patients may actually pass renal tissue in their urine secondary to papillary necrosis. Monitoring of baseline renal function (i.e., BUN/creatinine) is always recommended in sickle patients.

PRIAPISM This painful, sustained erection of the penis in the absence of sexual stimulation is the result of the accumulation of sickled cells in the corpora cavernosa. Severe and prolonged attacks can cause impotence. This occurs in up to 30 percent of males with SCD; surgical decompression is usually required. Newer approaches include oral administration of a-adrenergic agonists (terbutaline and pseudoephedrine) or intrapenile injection (usually with dilute epinephrine) of vasodilators such as hydralazine, and/or needle aspiration of the corpora cavernosa.

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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