HTN: Chapter 83

1
HTN Chapter 83

• Marx Rosen's Emergency Medicine Concepts and
  Clinical Practice, 6th ed.

2
Perspective

• Perspective
• Medical management of hypertension has reduced
  stroke mortality by 50 on an age-adjusted basis
• Probably partially responsible for the decline in
  mortality from coronary artery disease.
• Although approximately 75 of patients with
  chronically elevated BP are aware of their
  disease
• as few as one half to one quarter of these
  patients are adequately treated.

3

• Anxiety and pain often cause transient
  hypertension, but evaluation of the patient for
  evidence of acute end-organ ischemia is
  important.
• Even if the patient's BP does remain elevated
  without end-organ damage, urgent treatment is
  rarely beneficial, and an appropriate referral
  for long-term management should be made.

4
Principles of Disease

• Definition
• In adults, a systolic pressure less than 140 mm
  Hg and a diastolic pressure less than 90 mm Hg
  are considered normal.
• Prehypertension
• If the systolic pressure is between 140 and 159
  mm Hg or if the diastolic pressure is between 90
  and 95 mm Hg, the term prehypertension is now
  applied.
• reflecting that the lifetime incidence of
  hypertension in these individuals is twice that
  of individuals in the normal range.2
• Hypertension
• The patient with a systolic pressure of 160 mm Hg
  or greater or a diastolic pressure over 95 mm Hg
  is considered to be hypertensive.

5

• Even isolated systolic hypertension in elderly
  patients is a significant risk factor for
  cardiovascular disease, especially when combined
  with other risk factors.
• In older patients, an elevated pulse pressure
  (determined by subtracting diastolic from
  systolic pressure) is an equally significant risk
  factor for stroke and MI.
• A single elevated BP does not necessarily mean
  that the patient has hypertension. This is
  especially true in children.9 BP measurement
  should be repeated after the patient is in a
  reclining position for at least 10 minutes and
  should be checked in both arms.
• If the second reading is also elevated or close
  to the hypertensive range, the patient should be
  advised of the potential for hypertension and
  referred for follow-up.

6
Pathophysiology

• Essential hypertension.
• No specific cause of essential hypertension has
  been identified, although many factors, including
  heredity, age, race, obesity, and the amount of
  dietary sodium, may contribute to the elevated BP
• Two major theories exist
• (1) hypertension results from alterations in the
  contractile properties of smooth muscle in
  arterial walls
• (2) alterations of arterial smooth muscle are a
  response to chronically elevated BP resulting
  from a primary failure of normal autoregulatory
  mechanisms.

7
Renin, Angiotensin, and Aldosterone

• Renin
• An enzyme produced by the kidney that splits off
  angiotensin I from a plasma globulin
  precursor.11 Angiotensin I is converted by an
  enzyme in the lung to produce angiotensin II.
  Angiotensin II is a potent vasoconstrictor and
  also stimulates aldosterone production in the
  adrenal gland.
• ACE inhibitors or angiotensin blockers are
  clearly the drugs of choice in hypertensive
  patients with diabetes or decreased left
  ventricular function, or both.

8
Renal Disease

• All types of renal disease have been associated
  with hypertension
• Renovascular hypertension results from the
  overproduction of renin secondary to reduced
  blood flow through the stenotic renal artery. The
  increased levels of renin lead to activation of
  the angiotensin pathway and resultant
  hypertension.
• Another vascular lesion associated with arterial
  stenosis and hypertension is fibromuscular
  dysplasia of the renal arteries. This disease is
  predominant in young white women, and flank
  bruits are often present.
• Up to 70 of patients with chronic pyelonephritis
  have elevated BP.

9
Arterial Disease

• Coarctation of the aorta
• An important cause of secondary hypertension,
  and early surgical intervention can greatly
  improve the patient's prognosis.
• triad of upper extremity hypertension, a systolic
  murmur best heard over the back, and delayed
  femoral pulses should alert the examiner to the
  diagnosis of coarctation.
• Loss of elasticity in the larger arteries
  associated with the aging process produces
  systolic hypertension as well as elevations in
  pulse pressure.
• The current literature strongly suggests that
  isolated systolic hypertension is associated with
  an increased risk of stroke, heart disease, and
  renal failure and should be treated.

10
Thyroid and Parathyroid Disease

• In thyroid storm, patients are usually
  hypertensive and tachycardic and ß-blockade is a
  mainstay of the acute management.

11
Pheochromocytoma

• Pheochromocytomas are responsible for less than
  1 of cases of hypertension.
• The characteristic feature of pheochromocytoma is
  paroxysms of hypertension associated with
  palpitations, tachycardia, malaise, apprehension,
  and sweating.
• These episodes may be related to physical and
  emotional stress, eating, position, or even
  micturition.
• Because of the episodic nature of this syndrome,
  the patient is often dismissed, and a diagnosis
  of hyperventilation syndrome or anxiety attack is
  made.
• The diagnosis is confirmed with elevated urinary
  levels of catecholamines, metanephrines, and
  vanillylmandelic acid.
• Treatment consists of a-blockade to control
  hypertension and subsequent ß-blockade for the
  control of cardiac dysrhythmias.

12
Emergency Department Presentation

• Hypertension is seen in the emergency department
  in the following four general ways   
• 1.    Hypertensive emergency or hypertensive
  crisis with acute end-organ ischemia
• 2.   Hypertensive urgency, a historical term
  related to arbitrarily elevated BP with
  nonspecific symptoms
• 3.    Mild hypertension without end-organ
  ischemia
• 4. Transient hypertension related to anxiety or
  the primary complaint

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CLINICAL PRESENTATION OF HYPERTENSIVE EMERGENCIES

• BP is usually markedly elevated and there is
  evidence of acute dysfunction in the
  cardiovascular, neurologic, or renal organ
  system. These conditions are true medical
  emergencies and mandate reduction of BP within 1
  hour.

14
Hypertensive Encephalopathy

• Throughout the normal range of BP, cerebral blood
  flow is maintained by fluctuations in the
  vascular tone of the cerebral resistance vessels
  known as autoregulation.
• Hypertensive encephalopathy is an uncommon
  syndrome resulting from an abrupt, sustained rise
  of BP that exceeds the limits of cerebral
  autoregulation of the small resistance arteries
  in the brain.
• Hypertensive encephalopathy
• (1) acute in onset
• (2) reversible.
• Patients present with severe headaches,
  vomiting, drowsiness, and confusion.
• Hypertensive encephalopathy is a true medical
  emergency untreated patients develop increasing
  coma, and death may ensue within a few hours. The
  rapid measured reduction of BP is mandatory. The
  standard treatment regimen is intravenous (IV)
  nitroprusside with a careful reduction of the MAP
  by 25 or to a minimum diastolic pressure of 110
  mm Hg over an hour.

15
Malignant Hypertension

• Malignant (accelerated) hypertension is severe
  hypertension associated with evidence of acute
  and progressive damage to end organs.
• The diastolic BP is usually greater than 130 mm
  Hg.
• Patients with malignant hypertension appear ill
  and often present with complaints of severe
  headache, blurred vision, dyspnea, and chest pain
  or with symptoms of uremia.
• In addition to elevated BP, these patients must
  demonstrate evidence of acute end-organ damage as
  a result of the hypertension.
• Malignant hypertension is treated by the
  judicious lowering of MAP by 25 of pretreatment
  levels over the initial minutes to hours, then
  toward a target of 160/100 over 2 to 6 hours

16
Stroke Syndromes

• In most of these patients, elevated BP is the
  physiologic response to the stroke itself and is
  not the immediate cause
• Some have recommended careful antihypertensive
  treatment for patients with persistent, extreme
  elevations of BP after a stroke (e.g., diastolic
  pressure gt140 or MAP gt130 mm Hg), but data are
  lacking.
• If BP reduction is pursued in these patients,
  labetalol is the agent of choice.

17
Pulmonary Edema

• Most patients with congestive heart failure have
  some degree of increased peripheral vascular
  resistance (PVR) and resultant hypertension this
  is a normal response.
• With standard treatment of pulmonary edema,
  including morphine, nitrates, oxygen, ACE
  inhibitors, and furosemide, catecholamine levels
  fall and BP returns rapidly toward normal.

18
Pregnancy

• Any acute elevation of the diastolic BP above 100
  mm Hg in the pregnant patient represents a true
  hypertensive emergency.
• Although it may cause tachycardia and
  hypotension, the antihypertensive agent of choice
  in preeclampsia has classically been IV
  hydralazine.

19
Aortic Dissection

• The goals of medical therapy are to lower the BP
  to a systolic level of 100 to 120 mm Hg and to
  reduce the ejection force of the heart.
• The combined a/ß-blocker labetalol has been used
  successfully

20
MANAGEMENT OF HYPERTENSIVE EMERGENCIES

• Vasodilators
• Sodium Nitroprusside
• Nitroprusside (Nipride, Nitropress) is a powerful
  vasodilator, with a direct effect on the smooth
  muscle of both resistance and capacitance
  vessels.
• Cyanide is an intermediate metabolite, but
  cyanide toxicity is extremely rare

21
Vasodilators

• Nitroglycerin
• Nitroglycerin is a vasodilating agent that acts
  predominantly on the venous system, decreasing
  left ventricular end-diastolic pressure.
• Hydralazine
• Hydralazine (Apresoline) is a direct arteriolar
  vasodilator that was widely used in the past for
  the treatment of hypertensive emergencies of
  pregnancy.
• The usual starting dose of hydralazine is 5 mg
  IV, with repeated doses of 5 to 10 mg every 20
  minutes as needed to keep the diastolic pressure
  below 110 mm Hg

22
ß-Blockers

• Labetalol
• Labetalol (Trandate, Normodyne) is a selective
  a1-blocker and nonselective ß-blocker with a
  ratio of a/ß-blockade between 13 and 17.
• Labetalol lowers BP by blockade of the
  a1-receptors in vascular smooth muscle and the
  cardiac ß-receptors.

23
a-Blockers

• Phentolamine (Regitine) is an a-blocking agent
  used for the management of catecholamine-induced
  hypertensive crises (e.g., pheochromocytoma, MAOI
  crisis, cocaine overdose).

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• Nicardipine
• Nicardipine (Cardene) is a parenteral
  dihydropyridine calcium channel blocker that has
  become very popular in the treatment of
  postoperative hypertension.
• Nicardipine is administered as an infusion
  beginning at 5 mg/hr, increasing the infusion
  rate every 15 minutes until the desired reduction
  of BP has been achieved, to a maximum dose of 15
  mg/hr.

25
Enalaprilat and Enalapril

• Enalaprilat (Vasotec) is a parenteral active
  metabolite of the ACE inhibitor enalapril.
• The acute dose is 0.625 to 5 mg administered as a
  single bolus.

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Osteopathic Considerations

• Sub-occipital release
• Normalizes the parasympathetics
• Rib raising
• Normalizes the sympathetics