ED 08-4 DIAGNOSIS AND TREATMENT OF HYPERTENSIVE EMERGENCY IN CHILDREN.

According to the seventh report of Joint National Committee (JNC 7), hypertensive emergency (HE), a kind of hypertensive crisis, is defined as a sudden and abrupt elevation in blood pressure so as to cause acute target organ dysfunctions, including central nervous system, cardiovascular system or kidneys. Patients with HE require immediate reduction in markedly elevated blood pressure. Currently, there are no international guidelines for children HE, so the JNC definition is commonly used. Hypertensive emergency in children is rare but a life-threatening emergency. Generally, secondary hypertension is the most common reason of hypertensive emergency. We analyzed clinical features of 16 patients with HE who were diagnosed as HE from Jan 2007 to Dec 2015 in our hospital. Results showed that all patients were diagnosed as secondary hypertension, including 10 cases associated with renal diseases, 3 cases with Takayasu arteritis,1case with hypercortisolism, 1 case with migraine, and 1 case with unknown reason. The pathophysiologic mechanisms of HE involve sympathetic hyperactivity and increasing of vasoconstricting substances, activation of renin-angiotensin system (RAS), decreasing in auto-regulation of target organs, and chronic endothelial damage and remodeling. There is strong evidence that the renin-angiotensin system plays an important role in the genesis of hypertensive crisis. Target organ dysfunctions may be manifested as hypertensive encephalopathy, acute left ventricular failure, acute renal failure and papilledema, etc. Hypertensive encephalopathy is the most common one with the symptoms of persistent headache, nausea, vomiting, altered mental status, convulsion and coma. Some patients may be revealed as reversible posterior leukoencephalopathy. Among 16 patients involved in our study, 13 patients had encephalopathy with 4 cases of reversible posterior leukoencephalopathy, 4 patients had acute heart failure with 1 case of fundus exudation, and 2 case of acute renal failure. 2 patients died with 3 target organ dysfunctions, including encephalopathy, acute heart failure, and acute renal failure, which showed that multiple organ dysfunction may increase the mortality of HE, so earlier identification of target organ dysfunction to take steps is important. As to the key points of diagnosis of HE, one is the level of blood pressure and its elevation speed, the other is to identify target organ dysfunction earlier. Detailed medical history and complete physical examination are important. Additionally, serum electrolytes, complete blood counts, blood urea nitrogen, creatine, urinalysis, chest radiography, electrocardiogram, enchocardiography, brain MRI and fundoscopy may be needed in some situation. It is worth mentioning that 8 patients had hypokalemia, and hypokalemia is associated with the activation of RAS. It indicates the possibility that hypokalemia may be a predictive factor of HE. The treatment of HE is based on the differentiation of acute, chronic or acute attack on chronic hypertension. Once HE is confirmed, intravenous drugs should be emergently applied. It is suggested that the targeted drop of mean arterial pressure in the first 6∼8 hours should reach 25% of the difference between the original value and the target value, and should be followed by a gradual reduction to the target value within 24∼48 hours. Safe and efficacious drugs with rapid onset of action are favorable. According to our experience, sodium nitroprusside and phentolamine are the most useful and effective in our hospital. It's notable that lowering intracranial pressure is more important than decreasing blood pressure for those patients with a high intracranial pressure who are diagnosed as encephalopathy. However, rapidly decreasing blood pressure levels may result in decreasing blood flow of brain, causing ischemia and infarction. To patients with acute left heart failure, management including sedation, oxygen supplement, cardiotonics, diuresis, and vascular dilation should be necessary. Long-acting oral anti-hypertensive medications should be introduced in conscious child after the blood pressure has been reasonably controlled within 24-48 hours. According to our experience, these patients with HE should need more than 2 kinds of anti-hypertensive drugs. In summary, the key points of diagnosis and treatment of HE are earlier identification and effective therapy to control the development of acute target organ dysfunctions.