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CHAPTER 42: Aortic Dissection 363

FIGURE 42-12. TEE shows 2D and color Doppler imaging of type A dissection involving aortic valve with aortic insufficiency. A two-beat loop can be viewed online. TL, True Lumen; FL, False Lumen.

TREATMENT of lactic acidosis, and a concomitant reduction in heart rate (usually
<60 bpm). A higher heart rate may be needed to improve circulation if
To maximize survival, optimal treatment of acute dissections must severe aortic regurgitation complicates aortic dissection.
include early pharmacologic control of blood pressure and pain, often Labetalol is the first choice among antihypertensive agents for blood
before the definitive diagnosis is made, combined with appropriate sur- pressure control in a patient with aortic dissection. It is a β -, β -, and
2
1
gical intervention. All patients with aortic dissections must have inten- α -adrenergic receptor (AR) blocker available for intravenous use
1
sive monitoring. The patient should be placed on a cardiac monitor and and therefore an excellent agent to quickly reduce blood pressure, heart
have an intra-arterial catheter (for ongoing blood pressure control) and rate, and dP/dT . It can be delivered by bolus (20 mg initially over
max
urinary catheter inserted. Blood should be drawn for standard labora- 2 minutes, followed by 20 to 80 mg every 10 to 15 minutes up to 300 mg
tory investigations as well as cross and typing for blood transfusion in cumulative dose) or as continuous infusion (0.5-2 mg/min). Although
case surgery is needed. The patient should be observed closely for any doses as high as 6 to 8 mg/min have been used, we recommend addi-
change in hemodynamic parameters or neurologic function and for tion of a different vasodilator if >2 mg/min is required for BP control.
evidence of organ ischemia. Its onset of action occurs within 2 to 5 minutes with peak effect in 5 to
15 minutes, and its duration of action is 2 to 12 hours. It is also suitable
PHARMACOLOGIC CONTROL OF BLOOD PRESSURE for long-term control of hypertension in oral form with usual doses of
■ ACUTE MANAGEMENT 100 to 400 mg twice daily up to 2400 mg total daily dose.
Esmolol is an ultrashort-acting selective β -adrenergic receptor
1
The initial therapeutic goal is to halt the progression of the dissect- blocker that is useful for patients with normal or labile blood pressure
ing hematoma and prevent aortic leakage or rupture. Pain control and for those expected to have emergent surgery. Its very rapid onset
is very important to reduce the adrenergic drive and is usually (decrease in heart rate in less than 2 minutes) and short duration of
accomplished with intravenous morphine or other intravenous opi- action (half-life of 8-10 minutes) allow for tight control of blood pres-
ates. Antihypertensive agents are used to reduce the systolic blood sure to the desired goal. It is usually administered as a bolus, 0.5 to
pressure, heart rate, and velocity of LV contraction (or rate of rise in 1 mg/kg over 1 minute, followed by continuous infusion at 50 µg/kg/min
intra- ventricular pressure, so called dP/dT ). This is usually accom- that can be titrated in 50 µg/kg/min increments every 5 minutes up to a
max
plished with one or more antihypertensive agents listed in Table 42-2. maximum of 300 µg/kg/min. Due to β -receptor selectivity, its effect on
1
The goal is a reduction of systolic blood pressure to the lowest tolerated blood pressure is significantly less than that of the nonselective labet-
for cerebral and end-organ perfusion (usually 100-110 mm Hg systolic) alol. Intravenous metoprolol and propranolol can also be used for acute
as evidenced by clear sensorium, good urinary output, and the absence aortic dissection.

TABLE 42-2 Antihypertensive Agents in Acute Aortic Dissection
Drug Mechanism Administration (Intravenous)
Labetalol hydrochloride α - And β -adrenergic blocker; decreases peripheral resistance without reflex 1. Bolus infusion: 0.25 mg/kg (20-80 mg over 2 minutes); may repeat
1+2
1
increase in heart rate and myocardial contractility (dP/dT ); action in 5-10 min- every 10 minutes
max
utes; half-life 6-8 hours 2. Continuous infusion: 0.5-2 mg/minutes. Max cumulative dose 300 mg/d
Esmolol hydrochloride β-Blocker with β -selective blockade; decrease in heart rate and myocardial con- 1. Bolus infusion: 500 µg/kg over 1 minute
1
tractility (dP/dT ); action in 2 min; half-life 8-10 min 2. Continuous infusion: 25-200 µg/kg/min
max
Sodium nitroprusside Direct vascular smooth muscle relaxant; decreased peripheral resistance and pre- Average continuous infusion: 0.5-3 µg/kg/min. Requires arterial line
load, may increase dP/dT when used alone; action in 1-2 min; half-life 2-3 min
max
Propanolol hydrochloride β-Adrenergic blocker; decreases myocardial contractility and peripheral resistance; Bolus infusion: 1-3 mg over 2-3 minutes; may repeat in 2-3 minutes
action in 1-2 minutes; half-life 2-3 hours
Enalaprilat Angiotensin-converting-enzyme inhibitor; action in <15 minnutes, duration Bolus infusion: 0.625-1.25 mg every 6 hours
~6 hours, has prolonged half-life with renal dysfunction

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