主动脉内球囊反搏综述Intraaortic Balloon Pump( IABP)Review Article

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Intraaortic balloon pump (IABP) counterpulsation was first developed in 1962.

The subsequent introduction of percutaneous insertion (usually through the femoral artery with placement in the descending thoracic aorta distal to the left subclavian artery) increased the speed and ease of insertion, thereby providing an impetus for its expanded use in the following clinical settings :

• 1.Treatment of cardiogenic shock (left ventricular failure or mechanical complications of an acute myocardial infarction)
• 2.Treatment of intractable angina
• 3.Weaning patients from cardiopulmonary bypass
• 4.Adjunctive therapy after thrombolysis in patients at high risk for restenosis .
• 5.Adjunctive therapy in high risk or complicated angioplasty .
• 6.Prophylaxis in patients with severe left main coronary arterial stenosis or critical aortic stenosis in whom surgery is pending .

IABP has emerged as the single most effective and widely used circulatory assist device. The basic principles regarding use of the IABP are presented here.

HEMODYNAMIC EFFECTS — A counterpulsation balloon pump that was synchronized to the cardiac cycle was used for the first time in patients in cardiogenic shock in 1969 . The IABP has two major hemodynamic effects:

• Blood is displaced to the proximal aorta by inflation during diastole
• Aortic volume and afterload are reduced during systole through a vacuum effect created by rapid balloon deflation.

These effects may be quite variable, and they depend upon the volume of the balloon, its position in the aorta, heart rate, rhythm, the compliance of the aorta, and systemic resistance . The higher the arterial elastance, which is determined in part by compliance, the greater the hemodynamic improvement from IABP . Despite this variability, expected changes in the hemodynamic profile in the majority of patients with cardiogenic shock include :

• -A decrease in systolic pressure by 20 percent
• -An increase in diastolic pressure by 30 percent, which may raise coronary blood flow to territory perfused by a vessel with a critical stenosis
• -A reduction of the heart rate by less than 20 percent
• -A decrease in the mean pulmonary capillary wedge pressure by 20 percent
• -An elevation in the cardiac output by 20 percent

-In addition, intraaortic balloon pumping reduces mean systemic impedance and developed systolic pressure, and causes a 14 percent decline in calculated peak left ventricular wall stress . The reductions in afterload and wall stress lead to a fall in myocardial oxygen consumption.

Effects on coronary artery blood flow — The IABP has a variable effect on total coronary blood flow. Some studies, for example, found little or no change in coronary blood flow ,while others noted a significant augmentation .
Increased blood flow is most likely to occur in coronary vascular beds maximally dilated by ischemia, a setting in which autoregulation is at a maximal level and flow becomes pressure-dependent.Counterpulsation is able to enhance blood flow to these areas via an increase in perfusion pressure.
Another determinant of the coronary blood flow response to IABP is the severity of the coronary stenosis . One report, for example, found no improvement distal to critical stenoses (95 percent diameter narrowing) . There was, however, a significant increase in flow after successful angioplasty .

INDICATIONS — The IABP is an effective temporary therapeutic option in the patient with significant dysfunction resulting from ischemia. The 2004 American College of Cardiology/American Heart Association (ACC/AHA) guidelines on ST elevation MI made the following recommendations, which were not changed in the 2007 focused update, for the use of IABP in the following settings :

• 1.Hypotension (systolic blood pressure less than 90 mmHg or 30 mmHg below baseline mean arterial pressure) that is not responsive to other interventions.

• 2.A low output state.

• 3.Cardiogenic shock that is not quickly reversed with pharmacologic therapy.

• 4.Acute mitral regurgitation, particularly due to papillary muscle rupture, or ventricular septal rupture.
  

• 5.Recurrent ischemic chest discomfort with signs of hemodynamic instability, poor left ventricular function, or a large area of myocardium at risk.

In the last three settings, the use of an IABP was considered to be beneficial both for hemodynamic support and as a stabilizing measure for angiography and prompt revascularization.

Acute coronary ischemia — Intraaortic balloon pumping reduces ST-segment abnormalities in patients with acute myocardial infarction or unstable angina, and is effective in the treatment of angina unresponsive to medical therapy .
Cardiogenic shock — Intraaortic balloon counterpulsation alone is effective hemodynamically in patients with cardiogenic shock resulting from an acute myocardial infarction . The hemodynamic response is most prominent in patients with mechanical defects such as mitral regurgitation or a ventricular septal defect in whom the cardiac output will rise and pulmonary capillary wedge pressure will fall. A large nonrandomized cooperative trial, performed before the availability of thrombolytic agents and percutaneous angioplasty, demonstrated that IABP reversed end-organ hypoperfusion in patients with an acute myocardial infarction and cardiogenic shock in whom vasopressor therapy was ineffective .
The mortality rate remains very high (83 percent in this report) in cardiogenic shock when IABP is not combined with coronary reperfusion or revascularization. This is compatible with the observation noted above that IABP does not increase coronary flow distal to a critical stenosis but will do so after revascularization .
High-risk PCI — Intraaortic balloon pumping may be useful in a high-risk or complicated percutaneous coronary intervention (PCI), or rescue PCI following failed thrombolysis . As an example, one report of prophylactic IABP for high-risk patients undergoing PTCA (LVEF 24 percent) found that revascularization was successful in 96 percent, with no deaths or myocardial infarctions within 24 hours of the procedure. One non-randomized comparison of prophylactic IABP insertion versus no prophylactic insertion in high risk PCI patients observed that the six month major adverse cardiac event rate was lower in the prophylactic group .
IABP also may reduce periprocedural and postprocedural complications. In a series of 1490 patients with an acute myocardial infarction, IABP, inserted before PTCA, reduced the incidence of periprocedural events (ventricular fibrillation or tachycardia, cardiopulmonary arrest, or prolonged hypotension requiring support) in patients with cardiogenic shock (15 versus 35 percent for those not treated with an IABP) and in those with congestive heart failure or a low ejection fraction (0 versus 15 percent) . The use of an IABP was a significant independent predictor of freedom from catheterization laboratory events (odd ratio 0.48), suggesting that it may have a role as prophylactic therapy for infarction patients with poor left ventricular function who undergo primary PTCA.
Primary PCI for acute MI — IABP has been used in an attempt to maintain patency of coronary arteries in patients undergoing PCI during acute myocardial infarction. One multicenter trial, for example, randomly assigned patients who had vascular patency restored by primary PCI within 24 hours of an acute MI to standard therapy (which included intravenous heparin) or 48 hours of counterpulsation plus standard therapy . Significant reductions with IABP were noted for the combined end point of death, strokes, and recurrent ischemic events (13 versus 24 percent with standard therapy), and for reocclusion (8 versus 21 percent).
In contrast, in the PAMI-II trial, prophylactic IABP use following primary PCI was not beneficial in hemodynamically stable patients with at least one high-risk feature, including age>70, LVEF<45 percent, suboptimal PTCA result, malignant arrhythmias, three vessel coronary disease, or saphenous vein graft occlusion. At present, we occasionally use IABP for high-risk PCI but not routinely with primary PCI of acute MI or after failed thrombolysis.
Other — Other indications for IABP include mechanical complications of acute myocardial infarction such as acute ventricular septal defect and mitral regurgitation , inability to wean from cardiopulmonary bypass support , and early failure of thrombolytic therapy after an acute myocardial infarction.
The prophylactic placement of an IABP prior to CABG has been performed in patients with left main coronary artery stenosis, severely depressed left ventricular systolic function, diffuse coronary artery disease, and redo surgery .A meta-analysis from the Cochrane database of five randomized trials of preoperative IABP placement concluded that IABP placement might be beneficial in the above subgroups.
The 2004 American College of Cardiology/American Heart Association (ACC/AHA) guidelines on bypass surgery concluded that prophylactic IABP placement prior to CABG is probably indicated in patients with evidence of ongoing ischemia and/or a reduced cardiac output .
Refractory ventricular arrhythmias — The IABP can contribute to the management of medically refractory ventricular tachycardia and/or ventricular fibrillation in selected patients. This includes those with severely impaired left ventricular function and those in whom the arrhythmia compromises hemodynamic status for whom the IABP may provide time to implement appropriate therapy.

CONTRAINDICATIONS — The following circumstances are contraindications to IABP insertion:

• 1.Significant aortic regurgitation or significant arteriovenous shunting
• 2.Abdominal aortic aneurysm or aortic dissection
• 3.Uncontrolled sepsis
• 4.Uncontrolled bleeding disorder
• 5.Severe bilateral peripheral vascular disease
• 6.Bilateral femoral popliteal bypass grafts for severe peripheral vascular disease.

Insertion can be carried out in patients with aorto-bifemoral bypass grafts.

COMPLICATIONS
— Complications associated with the IABP may be divided into vascular and nonvascular events. The incidence of any complication was 7 percent, while major complications (major acute limb ischemia, severe bleeding, balloon leak, death related directly to the IABP insertion or IABP failure) occurred in 2.6 percent . The in-hospital mortality was 21 percent, one-half of which occurred while the IABP was in place. IABP-related mortality was only 0.5 percent.

Vascular — Vascular complications (occurring in six to 25 percent of cases) remain the major risk associated with intraaortic balloon pumping. The most common major complications include:

• Limb ischemia
• Vascular laceration necessitating surgical repair
• Major hemorrhage

It is important that the IABP be inserted into the common femoral artery rather than one of its branches (eg, the superficial or profunda femoral artery). Neither of the branches is generally large enough to permit insertion without producing arterial obstruction and limb ischemia. Improper insertion from a needle puncture which is too low is the most common cause of ischemic complications during IABP, and will often require removal of the IABP and contralateral insertion.
Arterial dissection is most often due to improper advancement of the guidewire with subsequent insertion of the IABP into a false lumen. The balloon may function normally in this position. Dissection may be diagnosed by ultrasonography and requires immediate balloon removal.
Less common vascular complications due to IABP compromise of perfusion include spinal cord ischemia and visceral ischemia.
Other — There are a number of other complications of the IABP :

• --Cholesterol embolization is an infrequent occurrence that may result in limb loss .

• --Cerebrovascular accident is a rare complication of IABP, since the balloon is normally positioned distal to the left subclavian artery. Cerebral ischemia only occurs when the IABP has been placed too proximally or has accidentally migrated proximally, or the central balloon lumen has been flushed vigorously and dislodged a thrombus.

• --Sepsis is uncommon unless counterpulsation continues for more than seven days. This observation suggests that infections can be minimized by meticulous sterile technique.

• --Balloon rupture is a rare event, and is generally related to the balloon pumping against a calcified plaque. Rupture may be followed by thrombus formation within the balloon, which requires surgical removal . In order to prevent helium gas embolization from the IABP, the balloon console will withdraw helium from the balloon and shut down the system with an alarm when it detects a loss of pressure.

---Additional complications include a fall in platelet count, hemolysis, seromas, groin infection, and peripheral neuropathy.

Clinical factors increasing IABP complications — The following factors are associated with an increase in the probability of vascular complications :

• -Peripheral vascular disease
• -Older age
• -Female gender
• -Diabetes mellitus
• -Hypertension
• -Prolonged support
• -Larger catheter size (>9.5 French)
• -Body surface area <1.8 m2
• -Cardiac index <2.2 L/min/m2

The higher complication rate in women is most likely related to the size of the iliac and femoral arteries. Patients with diabetes and hypertension suffer more vascular complications due to an increased incidence of peripheral vascular disease.
Newer percutaneous left ventricular assist devices (VAD), such as Tandem Heart™, have been compared to IABP.




这段文章节录自Up-to-date 网的一份最新 Review Article .我看了觉得或许我们麻醉医生也应该知道一些IABP 的知识吧,就发上来了.

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