Pediatric low cardiac output syndrome

Introduction to children with low cardiac output syndrome Low cardiac output syndrome (lowcardiacoutputsyndrome) is the most serious physiological abnormality in cardiac surgery and is one of the leading causes of postoperative patient death. The normal person's cardiac output is calculated per square meter area, that is, the heart index is 3 ~ 4L / (min · m2), if the heart index is reduced to below 3L / (min · m2), and there is peripheral vasoconstriction, tissue perfusion The phenomenon of deficiency is called low cardiac output syndrome. basic knowledge The proportion of illness: 0.001% Susceptible people: children Mode of infection: non-infectious Complications: hand and foot cyanosis

The cause of low cardiac output syndrome in children

(1) Causes of the disease

Incomplete treatment of right ventricular outflow obstruction or incomplete correction of pulmonary artery malformation is an important cause of postoperative low cardiac output. In addition to blood volume imbalance, insufficient diastolic capacity can affect cardiac output. The reason is that during intracardiac operation, it is necessary to block the heart circulation, ischemia, hypoxia can cause damage to the myocardium, resulting in myocardial insufficiency. In addition, if there is insufficient oxygen exchange after operation, hypoxia or acidemia can be aggravated. Myocardial systolic insufficiency, tachycardia or bradycardia affect atrioventricular diastolic, arrhythmia such as hypoxia or surgical trauma caused by tertiary conduction block, is often the cause of low postoperative discharge, in addition, cardiac compression Influencing the filling of the ventricle, such as pericardial tamponade or tight pericardial suture, is also one of the reasons for postoperative low discharge. Insufficient coronary insufficiency and coronary artery thrombosis caused by myocardial infarction are occasional causes.

Patients with poor preoperative cardiac function have poor general condition, heart, lung, liver and kidney function have different degrees of obstacles, and are prone to low cardiac output syndrome. Patients with large left to right heart flow are prone to pulmonary hypertension. In patients with severe pulmonary hypertension, pulmonary arteriosus wall sclerosis and wall thickening and stenosis, often accompanied by thickening of alveolar and capillary tissues, interstitial edema, increased pulmonary vascular resistance, enlarged right ventricular hypertrophy, preoperative The balance of supply and demand of myocardial oxygen is already in a state of compensation, and improper treatment during surgery can also be a triggering factor for low cardiac output syndrome.

(two) pathogenesis

Low cardiac output syndrome is the final result of imbalance of myocardial energy supply and demand during hypothermic cardiopulmonary bypass. After aortic blockade, metabolism is converted from aerobic metabolism to anaerobic metabolism, energy production is sharply reduced, and it is difficult to maintain the normal metabolism of cells. The function of the sodium pump is disordered. A large amount of sodium ions are retained in the cells to cause myocardial edema. The increase of lactic acid in the end products of anaerobic metabolism causes intracellular acidosis, which damages the myocardial cells. The left subventricular membrane is hypoxic during ischemia and hypoxia. The most serious, local metabolite accumulation, subendocardial microvascular dilatation, poorly protected myocardium, severe myocardial structural damage during ischemia, increased cell membrane permeability, capillary integrity destruction, blood recovery After perfusion, a large amount of water and electrolyte can enter the cells in a short time, aggravating myocardial edema, increasing endocardial vascular resistance, reducing blood flow, and further imbalance of supply and demand of oxygen under the intima, eventually resulting in subendocardial hemorrhage.

Active cardioprotection can effectively prolong the tolerance time of myocardial ischemia and reduce the degree of myocardial edema and necrosis during cardiopulmonary bypass. Continuous perfusion of oxygenated blood at room temperature can continuously supply oxygen to the myocardium, so as to block myocardial during circulation. From anaerobic metabolism to aerobic metabolism, it can avoid negative balance of myocardial energy metabolism, which is conducive to the recovery of postoperative myocardial function.

Prevention of low cardiac output syndrome in children

Strengthen various measures to prevent and treat myocardial hypoxia and ischemia; prevent heart rate, abnormal heart rhythm; improve the operation level of surgery, prevent heart pressure; prevent coronary blood supply, etc., give oxygen before surgery, nourish the heart muscle, strengthen the heart and diuresis, etc. Treatment can improve the heart function and is of great significance in reducing the incidence of low cardiac output syndrome. For children with congenital heart disease with high flow rate and pulmonary hypertension, angiotensin converting enzyme should be administered early. Treatment with inhibitors to control or reduce pulmonary hypertension can reduce the incidence of low cardiac output syndrome.

Complications of low cardiac output syndrome in children Complications of the foot and the foot

The blood pressure drops, the peripheral blood vessels contract, the limbs become cold, pale or blemishes, and the amount of urine is significantly reduced.

Symptoms of low-heart discharge syndrome in children Common symptoms Calcium-lowering heart rate Increases cold blood pressure in limbs, hair loss, metabolic acidosis

The decrease in cardiac output requires some clinical symptoms when the heart index is 2.5L/(min·m2), such as increased heart rate, reduced pulse pressure, decreased blood pressure (systolic blood pressure below 12 kPa), radial artery, and back. The arterial pulse is weak, the central venous pressure rises, the peripheral blood vessels contract, the limbs are cold, pale or blemishes, etc., and the urine volume can be reduced to 0.5~1ml/kg or less. At this time, the cardiac output is monitored: the index can be shown. 2L/(min·m2), blood test index <25ml/(m2·times), peripheral vascular resistance>1800dyn·s·cm-5, oxygen consumption 100ml/(min·m2), >20mg%.

Examination of children with low cardiac output syndrome

Blood tests have non-specific changes such as a decrease in PaO2, a change in pH, and a decrease in urine output.

1. Electrocardiogram examination: There may be performances such as arrhythmia.

2. Bedside film or ultrasound: to help diagnose the pericardial tamponade.

3. Echocardiography: decreased cardiac function and myocardial insufficiency.

Diagnosis and diagnosis of low cardiac output syndrome in children

Clinically, the decrease in blood pressure, the increase in central venous pressure, and the significant decrease in urine volume are sufficient to confirm the diagnosis of low cardiac levitation. Kouchakos et al. pointed out that when the general signs of low cardiac output do not appear, the following conditions should be suspected. Intrinsic: 1 blood pressure decreased; 2 left atrial pressure increased; 3 peripheral perfusion insufficient; 4 metabolic acidosis, according to the history and clinical manifestations should consider the diagnosis of this disease, combined with the results of auxiliary examination confirmed.

After making a diagnosis of this disease, pay attention to the identification of the cause.

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