WORKUP

Lab Studies:

• Hematocrit may be lowered in patients with a ruptured aneurysm.

• Coagulation studies may demonstrate coagulopathy.

• BUN and creatinine levels may be elevated in patients with shock and renal hypoperfusion.

• A blood bank sample should be ordered.

• Creatine kinase (CK) and troponin levels may be measured to assess for myocardial infarction.

Imaging Studies:

• CT scanning, MRI, angiography, and transesophageal echocardiography are most often used to assess thoracic aneurysm in the emergent setting. The preferred method of assessment depends on the stability of the patient, the availability of radiographic modalities, and the preference of the surgeon. However, CT scanning is most commonly used in both emergent and outpatient settings to diagnose and follow thoracic aneurysm.

• Chest radiography

• Chest radiography should be obtained in the initial workup of patients with chest discomfort.

• Findings may not demonstrate small aneurysms.

• Findings suggestive of aneurysm include mediastinal widening, blurring of the aortic knob, and tracheal displacement. Pleural effusion is usually associated with aortic dissection rather than with a stable aneurysm.

• An elevated hemidiaphragm may suggest phrenic nerve compression from mass effect, but this finding is exceedingly rare compared with the other findings listed.

• Thoracic CT scanning

• Intravenous contrast-enhanced CT scanning is the procedure of choice for diagnosis.

• Its sensitivity is 96-100%, and its specificity is 99% for detecting aneurysms.

• CT scanning is useful in evaluating aneurysm size, proximal and distal extension, presence or absence of dissection, and in seeking other pathology within the chest.

• Use caution in patients with an allergy to the contrast agent or in those with renal failure.

• Use caution in moving patients who are potentially unstable to the CT scanner.

• Contrast angiography

• Contrast angiography is useful in assessing complex aortic pathology and identifying anatomy of branch vessels.

• Its sensitivity is 85% and its specificity is 95% in detecting aneurysms.

• Aortic dissection may not be detected, especially if thrombosis is present in the false lumen.

• Use caution in patients with an allergy to the contrast agent or in those with renal failure.

• Use caution in moving patients who are potentially unstable to the angiography suite.

• Magnetic resonance angiography

• Magnetic resonance angiography is useful in assessing the aortic anatomy, the size of the aneurysm, the dissection, and the branch vessels.

• Its sensitivity is 100% and its specificity is 100% in detecting aneurysms.

• Magnetic resonance angiography does not require the administration of iodinated radiologic contrast material.

• This study requires longer image acquisition times than other modalities.

• Use caution in moving patients who are potentially unstable to the MRI scanner, where distance from the emergency department is compounded by difficulties in hemodynamic monitoring within the scanner.

• Transesophageal echocardiography

• Transesophageal echocardiography is increasingly used to assess the anatomy of the aorta and its valves and the presence of dissection.

• Its sensitivity is 98% and its specificity is 99% in depicting aneurysms.

• Transesophageal echocardiography may be performed rapidly at the bedside.

• The results are operator dependent.

Other Tests:

• ECG

• ECG is useful in evaluating patients with chest discomfort or dyspnea.

• Findings may demonstrate strain or ischemia when a proximal aneurysm distorts the anatomy of the aortic valve or the coronary artery. Myocardial infarction may also be present.

TREATMENT

Prehospital Care:

• In patients with symptoms suggestive of TAA, prehospital care should consist of ensuring adequate airway and breathing, providing oxygen via a nonrebreather mask, placing 2 large-bore intravenous lines, and providing continuous cardiac monitoring.

• Patients who are unstable (often those with a ruptured aneurysm or dissection) may require airway protection, mechanical ventilation, and aggressive fluid resuscitation. Timely communication between prehospital care providers and the receiving hospital is important in ensuring that the proper resources are available and brought to bear rapidly.

Emergency Department Care:

• Initial stabilization includes the following:

• Placing 2 large-bore intravenous lines, administering 100% oxygen, and providing a cardiac monitor

• Monitoring urine output

• Consider alternate diagnoses. Until the diagnosis of TAA is established, be vigilant for other causes of symptoms, such as myocardial infarction (MI), aortic insufficiency, CHF, or pulmonary embolus.

• Provide aggressive blood pressure control. Beta-blockers and nitrates are commonly used.

• For patients who are hemodynamically unstable, provide the following:

• Aggressive fluid resuscitation (including blood products)

• Placing an arterial line in the right radial artery (or in the left radial artery, if the systolic blood pressure on the left is higher), especially in patients who may have dissection or in those who are receiving intravenous nitroprusside and/or esmolol

• Correction of coagulopathy

• Immediate surgical consultation

Consultations:

• Immediately consult with a cardiac surgeon (for ascending aorta or arch) or with a vascular surgeon (for descending aorta) for patients who are hemodynamically unstable or for patients with symptoms of a thoracic aneurysm. Anesthesia and operating room personnel need to be contacted in cases where emergent operative procedures are indicated.

• Consult with a vascular surgeon or a cardiac surgeon and a radiologist to determine the optimal studies for assessing the anatomy of the thoracic aneurysm.

MEDICATION

The goal of medical therapy is to reduce the pulse pressure (dP/dt) within the aorta. Reducing the heart rate, the blood pressure (BP), pain, and anxiety are the mainstays of therapy.

Drug Category: Antihypertensive agents -- These agents are used to reduce arterial pressure. Short-acting IV beta blockade and nitrates are very effective in reducing the dP/dt, especially in the ascending aorta. Consider calcium channel blockade in patients with contraindications to beta blockade.

Drug Name	Esmolol (Brevibloc) -- Ultra–short-acting beta1-blocker particularly useful in patients with labile arterial pressure because it can be abruptly discontinued if necessary. Typically used in conjunction with nitroprusside. May be useful as a means to test beta-blocker safety and tolerance in patients with history of obstructive pulmonary disease who are at uncertain risk of bronchospasm from beta blockade. Elimination half-life is 9 min. The objective is a target heart rate of 55-65 bpm.
Adult Dose	Loading dose infusion: 250-500 mcg/kg IV over 1 min, followed by a 4-min maintenance infusion of 50 mcg/kg/min; if desired clinical effects are not observed, a repeat loading dose may be administered, followed by a 4-min infusion at 100 mcg/kg/min IV; 2 more repeat loading doses may be administered if desired effect is still not attained, increasing each subsequent 4-min infusion dose by 50 mcg/kg/min IV; the overall pattern would yield the following: Cycle 1: Load 250-500 mcg/kg IV over 1 min, 50 mcg/kg/min IV over 4 min Cycle 2: Load 250-500 mcg/kg IV over 1 min, 100 mcg/kg/min IV over 4 min Cycle 3: Load 250-500 mcg/kg IV over 1 min, 150 mcg/kg/min IV over 4 min Cycle 4: Load 250-500 mcg/kg IV over 1 min, 200 mcg/kg/min IV over 4 min When desired BP is approached, omit loading infusion and reduce incremental dose in maintenance infusion from 50 mcg/kg/min to 25 mcg/kg/min or lower; may increase interval between titration steps from 5-10 min, if desired
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity; uncompensated CHF; bradycardia; cardiogenic shock; AV conduction abnormalities
Interactions	Aluminum salts, barbiturates, NSAIDs, penicillins, calcium salts, cholestyramine, and rifampin may decrease bioavailability and plasma levels, possibly resulting in decreased pharmacologic effect; sparfloxacin, astemizole (recalled from US market), calcium channel blockers, quinidine, flecainide, and contraceptives may increase cardiotoxicity; digoxin, flecainide, acetaminophen, clonidine, epinephrine, nifedipine, prazosin, haloperidol, phenothiazines, and catecholamine-depleting agents may increase toxicity
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Beta-adrenergic blockers may mask signs and symptoms of acute hypoglycemia and clinical signs of hyperthyroidism; symptoms of hyperthyroidism, including thyroid storm, may worsen when medication is withdrawn abruptly (withdraw drug slowly and monitor closely)

Drug Name	Labetalol (Normodyne, Trandate) -- Blocks alpha-, beta1-, and beta2-adrenergic receptor sites, decreasing BP.
Adult Dose	Initial dose: 20 mg (0.25 mg/kg for 80-kg adult) IV over 2 min; follow with 20-80 mg IV q10-15min until BP is controlled Maintenance dose: 2 mg/min IV continuous infusion; titrate up to 5-20 mg/min; not to exceed total dose of 300 mg
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity; cardiogenic shock; AV block; uncompensated CHF; pulmonary edema; bradycardia; reactive airway disease
Interactions	Decreases effects of diuretics and increases toxicity of methotrexate, lithium, and salicylates; may diminish reflex tachycardia associated with nitroglycerin use without interfering with hypotensive effects; cimetidine may increase blood levels; glutethimide may decrease effects by inducing microsomal enzymes
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Caution in impaired hepatic function; discontinue therapy if signs of liver dysfunction occur; lower response rate and higher incidence of toxicity may be observed in elderly patients

Drug Name	Metoprolol (Lopressor) -- Selective beta1-adrenergic receptor blocker that decreases automaticity of contractions. During IV administration, carefully monitor BP, heart rate, and ECG. When considering conversion from IV to PO dosage forms, use ratio of 2.5 mg PO to 1 mg IV metoprolol.
Adult Dose	5 mg IV q2min, up to 3 times 100 mg/d PO qd or divided bid/tid initially; increase at 1-wk intervals prn; not to exceed 450 mg/d
Pediatric Dose	Not established
Contraindications	Documented hypersensitivity; uncompensated CHF; cardiogenic shock; bradycardia; AV conduction abnormalities
Interactions	Aluminum salts, barbiturates, NSAIDs, penicillins, calcium salts, cholestyramine, and rifampin may decrease bioavailability and plasma levels, possibly resulting in decreased pharmacologic effects; sparfloxacin, phenothiazines, astemizole (recalled from US market), calcium channel blockers, quinidine, flecainide, and contraceptives may increase toxicity; may increase toxicity of digoxin, flecainide, clonidine, epinephrine, nifedipine, prazosin, verapamil, and lidocaine
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Beta-adrenergic blockade may reduce signs and symptoms of acute hypoglycemia and may decrease clinical signs of hyperthyroidism; abrupt withdrawal may exacerbate symptoms of hyperthyroidism, including thyroid storm (withdraw drug slowly and monitor closely); during IV administration, carefully monitor BP, heart rate, and ECG

Drug Name	Propranolol (Inderal, Betachron E-R) -- Class II antiarrhythmic nonselective beta-adrenergic receptor blocker. Has membrane-stabilizing activity and decreases automaticity of contractions. Not a first-line agent in the treatment of hypertensive emergencies. Do not administer IV in hypertensive emergencies.
Adult Dose	40-80 mg PO bid initially; increase to usual range of 160-320 mg/d PO prn; up to 640 mg/d PO may be required
Pediatric Dose	0.5 mg/kg/d PO divided bid/qid; increase gradually q3-7d; usual dosage range is 2-4 mg/kg/d PO divided bid; not to exceed 16 mg/kg/d
Contraindications	Documented hypersensitivity; uncompensated CHF; bradycardia; cardiogenic shock; AV conduction abnormalities
Interactions	Aluminum salts, barbiturates, NSAIDs, penicillins, calcium salts, cholestyramine, and rifampin may decrease effects; calcium channel blockers, cimetidine, loop diuretics, and MAOIs may increase toxicity; may increase toxicity of hydralazine, haloperidol, benzodiazepines, and phenothiazines
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Beta-adrenergic blockade may decrease signs of acute hypoglycemia and hyperthyroidism; abrupt withdrawal may exacerbate symptoms of hyperthyroidism, including thyroid storm (withdraw drug slowly and monitor closely); caution in patients with reactive airway disease; consider arterial line for close BP monitoring

Drug Name	Nitroprusside (Nipride, Nitropress) -- Causes peripheral vasodilation by direct action on venous and arteriolar smooth muscle, thus reducing peripheral resistance. Commonly used IV because of rapid onset and short duration of action. Easily titratable to reach desired effect. Light sensitive; both bottle and tubing should be wrapped in aluminum foil. Prior to initiating, administer beta-blocker to counteract physiologic response of reflex tachycardia that occurs when nitroprusside is used alone. This physiologic response increases shear forces against aortic wall, thus increasing dP/dT.
Adult Dose	0.5-3 mcg/kg/min IV; rates >4 mcg/kg/min may lead to cyanide toxicity
Pediatric Dose	Administer as in adults
Contraindications	Documented hypersensitivity; subaortic stenosis; idiopathic hypertrophic; atrial fibrillation or flutter
Interactions	None reported
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Caution in increased intracranial pressure, hepatic failure, severe renal impairment, and hypothyroidism; in renal or hepatic insufficiency, levels may increase and can cause cyanide toxicity; has ability to lower BP and thus should be used only in patients with mean arterial pressures >70 mm Hg

Drug Category: Analgesics -- Analgesics are used to control pain and to decrease sympathetic tone.

Drug Name	Morphine sulfate (Astramorph, Infumorph) -- DOC for narcotic analgesia because of reliable and predictable effects, safety profile, and ease of reversibility with naloxone. Like fentanyl, morphine sulfate is easily titrated to desired level of pain control. If administered IV, may be dosed in a number of ways; commonly titrated until desired effect obtained.
Adult Dose	Initial dose: 0.1-0.3 mg/kg IV/IM/SC Maintenance dose: 5-20 mg IV/IM/SC q4h for a 70-kg adult
Pediatric Dose	0.1-0.2 mg/kg IV/IM/SC q2-4h prn
Contraindications	Documented hypersensitivity; hypotension; potentially compromised airway in which establishing rapid airway control would be difficult
Interactions	Phenothiazines may antagonize analgesic effects; tricyclic antidepressants, MAOIs, and other CNS depressants may potentiate adverse effects
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Avoid in hypotension, respiratory depression, nausea, emesis, constipation, and urinary retention; caution in atrial flutter and other supraventricular tachycardias; has vagolytic action and may increase ventricular response rate

FOLLOW-UP

Further Inpatient Care:

• Unstable patients usually require medical or surgical ICU admission for careful hemodynamic monitoring.

• Patients who are symptomatic require admission, as do those in whom a final diagnosis is uncertain.

• Some patients with complicating conditions, such as Marfan syndrome or another cardiovascular disease, may require admission for medical stabilization and for more urgent surgical repair, even if they are asymptomatic at presentation.

• Indications for surgical repair include the following:

• Rupture

• Acute dissection (ascending requires urgent intervention, whereas descending is managed medically or surgically, if vascular complications arise)

• Symptomatic states, including pain, mediastinal organ compression, or aortic insufficiency severe enough to cause CHF or a dilated hypokinetic left ventricle

• Rapid aneurysm growth rate

• Absolute size (5.5 cm for ascending aortic aneurysm, 6.0 cm for descending aortic aneurysm; in patients with Marfan syndrome, 5.0 cm for ascending aortic aneurysm, 6.0 cm for descending aortic aneurysm)

• Surgical and other interventional options for TAA repair include the following:
  • Open approaches using cardiopulmonary bypass, hypothermia, and grafting

  • Endovascular stent grafting may be an option when TAA is limited to the descending aorta.

  • Complications of repair include paraplegia, renal failure, and intraoperative mortality.

Transfer:

• Patients with TAA who are symptomatic should only be transferred via advanced life support (ALS) system if the sending facility is unable to provide appropriate operative care.

Complications:

• Complications include the following:

• Rupture of the TAA into the mediastinum, pleural space, trachea, or esophagus

• Dissection

• Aortic insufficiency

• Congestive heart failure

Prognosis:

• In a series of 370 patients with TAA, survival at 1, 5, and 10 years were found to be 88%, 69%, and 56%, respectively.

MISCELLANEOUS

Medical/Legal Pitfalls:

• A large proportion of patients with TAA are asymptomatic, and patients who are symptomatic may exhibit a wide range of presentations in the setting of normal vital signs and normal ECG and chest radiography findings. Thus, the challenge is to retain a high index of suspicion for this disease.

PICTURES

Caption: Picture 1. Descending thoracic aortic aneurysm with mural thrombus at the level of the left atrium.
Picture Type: CT