Hypertensive Crisis in Critical Care

nursebob.comę02/04/09

Primary hypertension may occur as an unknown cause. However there are several risk factors which predispose a person to hypertension.
Hypertension is usually diagnosed in men between 30-50 years of age. Blacks have twice the incidence. Obesity is one factor as well as smoking, excessive sodium intake, elevated serum lipids and alcohol intake. Stress may result in increased in sympathetic nervous system activity. In all of these cases hypertension and hypertensive crisis can be prevented or controlled. Hypertensive emergencies and urgencies occur in less than 1% of the 60 million people with hypertension. Even though not many people with hypertension experience hypertensive crisis, there are still a significant number of events. If left untreated, over time hypertension will cause changes in the vessels,resulting in stroke, blindness are renal failure

Any patent may have a diastolic pressure over 120 mm Hg is suffering from a hypertensive urgency. Hypertensive crisis occurs once organs are damaged. A hypertensive emergency is further characterized by end organ damage, while hypertensive urgency is characterized by a lack of end organ damage. Secondary hypertension is hypertension caused from another disease such as renal disease, toxemias of pregnancy, or adrenal cortex lesions. Some of the early symptoms of hypertension may include dizziness, flushed face, epistaxis, tinnitus, and headache.

Hypertensive urgencies are associated with the following: malignant hypertension, left ventricular failure, unstable angina, perioperative hypertension, and preeclampsia. There is a common misconception that hypertensive crisis usually occurs secondary to other problems. The most common cause of hypertensive crisis is inadequately treated primary (essential) hypertension. It may also be caused by renovascular hypertension, and renal parenchymal diseases. Rarely, it may be caused by pheochromocytoma, or primary hyperaldosteronism. Urgent hypertensive crises is caused by an abrupt increase in systemic vascular resistance. This increase is secondary to an increase in systemic vasoconstricting hormones (angiotensin II, vasopressin, norepinephrine.)

Hypertensive emergencies are associated with the following: hypertensive encephalopathy, intracranial hemorrhage, stroke, pulmonary edema, acute myocardial infarction, adrenergic crisis, dissecting aortic aneurysm, and eclampsia.

 

  Hypertensive Crisis Hypertensive Urgency
  Diastolic over 120 mm Hg

End organ damage

Associated with

No organ damage

  Intercranial hemorrhage Malignant hypertension
  Stroke Left ventricular failure
  Pulmonary edema Unstable angina
  Acute MI Perioperative hypertension
  Adrenergic crisis Preeclampsia
  Dissecting aorta  
  Aneurysm  
  Eclampsia  
  Etiology Etiology
  Inadequately treated primary hypertension Abrupt increase in systemic vascular resistance
  Renovascular hypertension Increase in systemic vasoconstricting
  Renal parenchymal diseases Hormones (angiotensin II, vasopressin, norepinephrine
  Pheochromocytoma (rare)  
  Primary hyperaldosteronism.  

When caring for patients with hypertension, as with all critical care patients, the weight should be measured daily, sodium intake should be monitored closely, intake and outputs must be monitored consistently, urine output must be measured ever hour, and blood pressure must be measured frequently. Tthe patient must be monitored for ischemic episodes (TIA). watch for the four "C's" of the complications of hypertension.

Complications - 4 C's
CAD - Coronary Artery Disease.
CRF - Chronic Renal Failure
CHF - Congestive Heart Failure
CVA - Cerebral Vascular Accident.

One of the first things which must be done and when carrying for patients with hypertension, is being able to distinguish between a hypertensive emergency in which organ damage is present and hypertensive urgency which has no organ damage.
this is best done by dynamite federal incomplete history from the patient, if this is not possible information might be obtained from previous medical records, relatives, our friends. It must be determined if the patient has had pre-existing hypertension. Any pre-existing renal disease must be determined as well as a history of cardiac disease such as; peripheral edema, orthopnea, shortness of breath or neurological symptoms which my include slurred speech, abnormal motor or sensory changes. be sure to include a medication history both prescription and nonprescription drugs. determined that the patient has been taken the illegal substances such as amphetamines, cocaine, LSD, or other sympathetic central nervous system stimulant. Determine if the patient has recently withdrawn from prescription antihypertensive drugs payong particular attention to clonidine and beta-blockers.

The physical exam should be done in a relaxed atmosphere with the patient in a comfortable position. The curtain should be drawn, and privacy afforded. Blood pressures both lying and upright must be taken, as many patients with severe hypertension undergo pressure diuresis. This is because the kidney has had increased pressure for an extended period of time. The body has undergone the excretion of sodium which has resulted in a decrease in volume. Often these patients are orthostatic. In addition to taking lying and standing blood pressures, the pressure should be checked in both the left and right upper extremity in order to assess for aortic disease. Endoscopic examination is imperative. Endoscopy helps distinguish between hypertensive urgency which will have good vessels with no spasm or enudate an emergency hypertension which will have Apple edema and hard action dates. I cardiovascular examination should include examination of the heart and aorta, electrocardiogram, the point a maximum impulse should be determined, chest x-ray should be done to rule out cardiomegaly and to evaluate the status of the lungs. The presence or absence of an aortic insufficiency murmor should be done to determine myocardial damage. A check for abdominal pulses should be done to assess the possibility of abdominal aortic aneurysm. In addition to this, a complete neurological examination should be performed.

Among the laboratory test performed, the urine analysis complete with dipstick should be done to determine protein or hematuria. A complete electrolyte panel should be done including the BUN and creatinine to assist in determination of renal function. A complete blood count should also be performed.

The establishment of intravenous access early is imperative. A central venous line might be required an arterial line in order to measure arterial pressure is essential. The patient must be placed on cardiac monitor. Do not wait for laboratory data before initiating treatment.

When treating hypertensive emergencies, many drugs can rapidly lower blood pressure. Initially, a target blood pressure should be identified to ensure that the blood pressure is not brought down lower than desired. This brings up two key questions; first, how rapidly should blood pressure be lowered and how much should the blood pressure be lowered? There are several additional factors, which must be considered in order to determine this.

Some other factors which are important to the management of hypertensive crisis are, the age and volume status of the patient. Caution should be observed when lowering the blood pressure in elderly patients. Keep in mind that the autoregulation mechanism of the elderly may not function completely. Consequently a rapid lower end of the blood pressure may result in ischemic cerebral vascular advance. The volume status of the patient diuresis may be depleted in elderly patients. Take BP setting and standing to determine the volume status. If a central line has been placed a central venous pressure might be obtained. Diuretics should be avoided is volume depletion is present. Some additional factors relevant to the management of hypertensive crisis. Is the patient undergoing any concurrent antihypertensive treatment? How long as hypertension present? Designation have any underlying medical conditions?

Medical Management of Hypertensive Crisis

Nitroprusside is a arterial and venous vasodilator. It has little to no effect on cardiac output. It is administered by I.V. infusion pump with a dose of 0.25-8 micrograms*kg/min. It has a rapid onset (seconds) and lasts for 3-5 minutes. Thiocyanate (a metabolite of nitroprusside which is excreted by the kidney) toxicity may occur if infusion is given too rapidly (more than 15 micrograms*kg/min) or for prolonged periods of time (greater than 48 hours). Special caution should be observed in patients with renal insufficiency, and nitroprusside is not recommended for use in pregnant patients. The build up of thiocyanate ion results in blurred vision, tinnitus, confusion, or seizures. Thiocyanate toxicity can be avoided in the following way: thiocyanate levels can be measured and the nitroprusside dosage adjusted to reduce toxicity, thiocyanate can also be removed by dialysis. Thiocyanate toxicity is not an issue in patients with normal renal function. Sodium nitroprusside is the most widely used medication for the treatment of hypertensive crisis. It is an ideal agent to manage hypertension because of its rapid onset, ease of titration, and reversibility of its effects.

Nitroglycerin is primarily a venous vasodilator. The effect on the venous system is considerably greater than the effect on the arterial system. It is administered by I.V. infusion pump with a dose of 5-100 micrograms/min. It has an onset from 2-5 min and a duration of 5-10 minutes. Possible side effects include headache and tachycardia.3

Diazoxide is an arterial vasodilator. It also effects the heart by increasing left ventricular contractility, work and oxygen consumption of the heart. Proper dosage is 50-150 mg q5 min or as infusion of 7.5-30 mg/min. It has an onset between 1-5 minutes and lasts for 4-24 hours. Use is contraindicated for patients with myocardial infarction, angina pectoris, dissecting aneurism or pulmonary edema. Additionally diazoxide may arrest active labor and increase blood sugar.3 Bolus injection can bottom out the BP and therefore has fallen out of favor. Infusion administration is becoming more popular.

Trimethaphan is a ganglionic blocker. It is administered by I.V. infusion pump with a dosage of 0.5-5 mg/min. It has an onset in 1-5 minutes and lasts for 10 minutes. This is the medication of choice in patients with emergent treatment of aortic dissection.

Labetalol is a beta adrenergic blocker. Dosage 2 mg/min IV or 20 mg initially followed by 20-80 mg q10 min with a maximum dose of 300 mg. It has an onset in less than 5 minutes and lasts for 3-6 hours. This medication has a 80-90% response rate and can be followed by the same drug orally.

Hydralazine is an arteriolar vasodilator. Dosage is 10-20 mg IV. It has an onset in 10-30 minutes and lasts for 2-4 hours. Importantly this medication may cause myocardial infarction or angina. This medication is not used for treatment of aortic dissection. The main use of this medication is for pregnant individuals.

Propranolol is a beta-adrenergic blocker. It is given either IV (1-10 mg load followed by 3 mg/hr) or p.o.(80-640 mg daily. It has an immediate onset and lasts for 2 hrs for IV dose and 12 hours for the oral dose. The primary use of this medication is as an adjunct to potent vasodilators to prevent tachycardia. It does not usually lower BP acutely.3

Enalaprilat is an ACE inhibitor. Dosage is 1.25-5 mg IV q6hrs. It has an onset of 15 minutes and a duration of 12-24 hours. This medication has a variable (and sometimes excessive) response. It should not to be used in pregnancy.3

Clonidine is a central sympatholytic. It is administered p.o. with a dose of 0.2 mg initially followed by 0.1 mg qh up to a 0.8 mg maximum. It has an onset between half an hour and 2 hours and lasts for 6-8 hours. Additionally, sedation is prominent and rebound hypertension may occur.3

Captopril is an ACE inhibitor. It administered p.o. with a dose of 6.5-50 mg. It has an onset in 15 min and lasts for 4-6 hours. Excessive response may occur in cases of renal artery stenosis or after diuretics. Additionally, captopril should not be used during pregnancy.3

Phentolamine is a alpha antagonist. It is administered IV with a dose of 5 mg for short term management of hypertensive crisis. It may cause tachycardia, cardiac arrhythmias, and ischemic events. The main use of this medication is in patients with pheochromocytoma.

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