Cerebral involvement, PRES and cardiopulmonary changes
THE CONTEXT
The passage describes neurological and cardiopulmonary involvement in hypertensive disorders of pregnancy, including posterior reversible encephalopathy syndrome (PRES).
Brain pathology and cerebral circulation
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CT and MRI findings include cortical hypodense areas, cerebral edema, capillary thrombosis, infarction, intraventricular and parenchymal hemorrhage, and fibrinoid necrosis.
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Cerebral blood flow is directly proportional to arterial pCO₂. Hypoventilation raises arterial pCO₂ and cerebral blood flow; hyperventilation lowers both.
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Normal or high pO₂ and baroreceptor reflexes do not affect cerebral blood flow.
Posterior reversible encephalopathy syndrome
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PRES is a transient neuroradiological entity associated with hypertension, generalized seizures, altered mental status, headache and visual changes.
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Its diagnostic hallmark is bilateral symmetrical vasogenic edema in the occipital and posterior parietal lobes, evident on T2-weighted MRI.
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The proposed pathology includes cerebral edema and vasospasm of cerebral and retinal vessels.
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PRES is usually reversible with prompt diagnosis and treatment. Rarely, cortical infarction, irreversible ischemic damage or death can occur.
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Persistent headache, hypertension, seizures or visual changes warrant neuroradiological imaging, including during the postpartum period.
Cardiac and pulmonary involvement
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Subendothelial hemorrhage may occur. Focal myocardial necrosis and hemorrhage can affect the conducting system and lead to heart failure.
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Mechanical compression of the left coronary vessels during systole permits little or no flow; most left ventricular blood flow occurs during diastole.
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Severe tachycardia is dangerous because it shortens the time available for coronary perfusion.
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Pulmonary findings include edema, hemorrhagic bronchopneumonia and ARDS.