Cardiogenic Shock Overview:
Cardiogenic shock occurs when adequate oxygen and nutrient delivery to the organs and tissues of the body is compromised as a direct result of myocardial dysfunction.
In other words, there is a failure of the heart to effectively pump blood.
Common causes of myocardial dysfunction that lead to shock include cardiomyopathy, myocarditis, arrhythmias, congenital heart disease, and the postoperative period after cardiac surgery.
Cardiogenic shock can also occur secondary to other forms of untreated shock as a result of inadequate oxygen delivery to the myocardium.
When cardiogenic shock occurs, the natural compensatory response results in tachycardia with increased systemic vascular resistance (vasoconstriction). These physiologic and compensatory responses can prove to be counterproductive and even detrimental to the critically-ill child.
Cardiogenic shock is characterized by significantly impaired myocardial contractility, increased preload, severely impaired myocardial compliance, increased afterload, and an abnormally and persistently high heart rate.
Signs of Cardiogenic Shock:
The four common clinical signs that distinguish cardiogenic shock are tachycardia, dyspnea, jugular vein distention, and hepatomegaly.
Increased respiratory effort is often the distinguishing characteristic that sets cardiogenic shock apart from other forms of shock.
The following list provides other signs and symptoms using the primary assessment model (ABCDE). (Click to view Signs and Symptoms)
- typically no airway abnormalities and patent airway
- tachypena, crackles, rales, cyanosis of extremities, nasal flaring, grunting, and pulmonary edema
- tachycardia, weak or absent peripheral pulses, jugular venous distention, low BP with a narrow pulse pressure, delayed capillary refill, signs of congestive heart failure, and oliguria
- anxiety, confusion, restlessness, drowsiness, and coma
- pale, cool, mottled skin, and diaphoresis
EKG, BNP, and chest X-Ray are three tests that can help to quickly direct the clinical pathway toward impaired myocardial function.
Management of Cardiogenic Shock:
Unlike other forms of shock which improve with aggressive fluid resuscitation, rapid fluid resuscitation with cardiogenic shock can be counterproductive and may worsen the patient’s condition. Fluid overload and pulmonary edema may occur, and caution should be used when administering fluids in the presence of cardiogenic shock.
Since cardiogenic shock is a result of myocardial dysfunction, the main objective of treatment is directed at improving cardiac function and cardiac output to restore adequate oxygen delivery to peripheral tissues. Another important objective is to minimize myocardial oxygen demand.
Any drug that causes an increase in systemic vascular resistance (SVR) (afterload) should be avoided. This includes phenylephrine and norepinephrine which both cause potent vasoconstriction.
Improve Cardiac Function:
The most effective way to improve cardiac function in the presence of cardiogenic shock is to reduce SVR. Medications which improve myocardial contractility and reduce SVR include dobutamine, milrinone, dopamine, and epinephrine.
Nitroprusside, which is a pure vasodilator, may be of benefit for reducing the high systemic vascular resistance associated with cardiogenic shock. However, it may be necessary to use dopamine or epinephrine to improve perfusion pressure when nitroprusside is administered.
Diuretics may also be used if there is evidence of pulmonary edema or systemic venous congestion. Diuretics help reduce fluid overload in the vascular space.
Myocardial Oxygen Demand:
Another important aspect to the treatment of cardiogenic shock is the reduction of myocardial oxygen demand. This can be achieved by support with intubation and mechanical ventilation, maintenance of a normal temperature, and patient sedation.
Pediatric cardiogenic shock represents a diagnostic and therapeutic challenge because of the large number of disorders that can cause it.
Identification of the etiology is of primary importance because the etiology will direct the course of treatment. Early expert consultation should be obtained.
There may be times when the etiology of cardiogenic shock cannot be readily identified or the cause is reversible (e.g. myocarditis, poisoning, etc…) and medical therapies have failed to correct shock. In cases like these, the use of (ECMO) Extracorporeal Membrane Oxygenation may be necessary for the temporary support and maintenance of cardiac output, oxygenation, and ventilation.
ECMO is basically a heart-lung bypass machine. With ECMO, the blood is removed from the body, and the carbon dioxide is artificially removed and exchanged for oxygen. The blood is then returned to the body. ECMO is usually only available at higher-level pediatric centers.
Ventricular assistive devices, like an aortic balloon pump, may also be used to support cardiac function.