Laboratory tests to be conducted include urine toxicology, blood glucose, a basic metabolic panel evaluating kidney function, or a complete metabolic panel evaluating liver function, EKG, chest x-rays, and pregnancy screening.The eyes may show bleeding in the retina, an exudate, cotton-wool spots, scattered splinter hemorrhages, or swelling of the optic disc called papilledema. Causes
Many factors and causes are contributory in hypertensive crises. The most common cause is patients with diagnosed, chronic hypertension who have discontinued anti hypertensive medications.Other common causes of hypertensive crises are autonomic hyperactivity such as pheochromocytoma, collagen-vascular diseases, drug use particularly stimulants, cocaine and amphetamines and their substituted analogues, monoamine oxidase inhibitors or food-drug interactions, spinal cord disorders, glomerulonephritis, head trauma, neoplasias, preeclampsia and eclampsia, hyperthyroidism and renovascular hypertension. People withdrawing from medications such as clonidine or beta-blockers have been frequently found to develop hypertensive crises. It is important to note that these conditions exist outside of hypertensive emergency, in that patients diagnosed with these conditions are at increased risk of hypertensive emergencies or end organ failure. Pathophysiology
The pathophysiology of hypertensive emergency is not well understood. Failure of normal autoregulation and an abrupt rise in systemic vascular resistance are typical initial components of the disease process.Hypertensive emergency pathophysiology includes:
Abrupt increase in systemic vascular resistance, likely related to humoral vasoconstrictors
Endothelial injury and dysfunction
Fibrinoid necrosis of the arterioles
Deposition of platelets and fibrin
Breakdown of normal autoregulatory functionThe resulting ischemia prompts further release of vasoactive substances including prostaglandins, free radicals, and thrombotic/mitotic growth factors, completing a vicious cycle of inflammatory changes.
If the process is not stopped, homeostatic failure begins, leading to loss of cerebral and local autoregulation, organ system ischemia and dysfunction, and myocardial infarction. Single-organ involvement is found in approximately 83% of hypertensive emergency patients, two-organ involvement in about 14% of patients, and multi-organ failure (failure of at least 3 organ systems) in about 3% of patients.In the brain, hypertensive encephalopathy - characterized by hypertension, altered mental status, and swelling of the optic disc - is a manifestation of the dysfunction of cerebral autoregulation. Cerebral autoregulation is the ability of the blood vessels in the brain to maintain a constant blood flow. People with chronic hypertension can tolerate higher arterial pressure before their autoregulation system is disrupted. Hypertensives also have an increased cerebrovascular resistance which puts them at greater risk of developing cerebral ischemia if the blood flow decreases into a normotensive range. On the other hand, sudden or rapid rises in blood pressure may cause hyperperfusion and increased cerebral blood flow, causing increased intracranial pressure and cerebral edema, with increased risk of intracranial bleeding.In the heart, increased arterial stiffness, increased systolic blood pressure, and widened pulse pressures, all resulting from chronic hypertension, can cause significant damage. Coronary perfusion pressures are decreased by these factors, which also increase myocardial oxygen consumption, possibly leading to left ventricular hypertrophy.