Cardiogenic shock


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Cardiogenic shock

  1. 1. Cardiogenic shock is a state in which a weakened heart isn't able to pump enough blood to meet the body's needs. It is a medical emergency and is fatal if not treated right away. The most common cause of cardiogenic shock is damage to the heart muscle from a severe heart attack. Not everyone who has a heart attack develops cardiogenic shock. In fact, less than 10 percent of people who have a heart attack develop it. But when cardiogenic shock does occur, it's very dangerous. For people who die from a heart attack in a hospital, cardiogenic shock is the most common cause. The medical term "shock" refers to a state in which not enough blood and oxygen reach important organs in the body, such as the brain and kidneys. In a state of shock, a person's blood pressure is very low. When a person is in shock (from any cause), not enough blood or oxygen is reaching the body's organs. If shock lasts more than several minutes, the lack of oxygen to the organs starts to damage them. If shock isn't treated quickly, the organ damage can become permanent, and the person can die. Pathophysiology The most common initiating event in cardiogenic shock is AMI. Dead myocardium does not contract, and classical teaching has been that when more than 40% of the myocardium is irreversibly damaged (particularly, the anterior cardiac wall), cardiogenic shock may result. On a mechanical level, a marked decrease in contractility reduces the ejection fraction and cardiac output. These lead to increased ventricular filling pressures, cardiac chamber dilatation,
  2. 2. and ultimately univentricular or biventricular failure that result in systemic hypotension and/or pulmonary edema. A systemic inflammatory response syndrome–type mechanism has been implicated in the pathophysiology of cardiogenic shock. Elevated levels of white blood cells, body temperature, complement, interleukins, and C-reactive protein are often seen in large myocardial infarctions. Similarly, inflammatory nitric oxide synthetase (iNOS) is also released in high levels during myocardial stress. iNOS induces nitric oxide production, which may uncouple calcium metabolism in the myocardium resulting in a stunned myocardium. Additionally, iNOS leads to the expression of interleukins, which may themselves cause hypotension. Myocardial ischemia causes a decrease in contractile function, which leads to left ventricular dysfunction and decreased arterial pressure; these, in turn, exacerbate the myocardial ischemia. The end result is a vicious cycle that leads to severe cardiovascular decompensation. Causes  The vast majority of cases of cardiogenic shock in adults are due to acute myocardial ischemia.  Systolic -Beta-blocker overdose, calcium channel blocker overdose, myocardial contusion, respiratory acidosis, hypocalcemia, hypophosphatemia, and cardiotoxic drugs (eg, doxorubicin [Adriamycin])  Diastolic - Ventricular hypertrophy and restrictive cardiomyopathies
  3. 3.  After load -Aortic stenosis, hypertrophic cardiomyopathy, dynamic outflow obstruction, aortic coarctation, and malignant hypertension  Valvular/structural -Mitral stenosis, endocarditis, myocarditis, mitral or aortic regurgitation, atrial myxoma or thrombus, pericardial tamponade & pulmonary embolism.  Risk factors for the development of cardiogenic shock include preexisting myocardial damage or disease (eg, diabetes, advanced age, previous AMI(acute MI), AMI (eg, Q-wave, large or anterior wall AMIs), congenital heart disease, and dysrhythmia. Signs & symptoms:  Profuse sweating, moist skin  Tachycardia & tachypnea  Restlessness, agitation, confusion due to decreased cerebral perfusion and subsequent hypoxia.  Skin that feels cool to the touch  Pale skin color or blotchy (mottled) skin  Rapid & Weak (thready) pulse  Decreased mental status - Loss of ability to concentrate & Loss of alertness  Decreased or no urine output  Hypotension due to decrease in cardiac output
  4. 4.  Distended jugular veins due to increased jugular venous pressure. DiagnosisBlood pressure. very low blood pressure, the most common sign of shock. ECG (electrocardiogram). diagnose severe heart attack & and monitor heart's condition. Chest X-ray.. A chest X-ray shows whether the heart is enlarged or whether there is fluid in the lungs, which can be signs of cardiogenic shock. Echocardiography. This test uses sound waves to create a moving picture of your heart. Echocardiography provides information about the size and shape of your heart and how well your heart chambers and valves are working. The test also can identify areas of heart muscle that aren't contracting normally. Not enough blood is flowing to these areas. Coronary angiography. passing a catheter (a thin, flexible tube) through an artery in leg or arm to heart. The catheter can measure the pressure inside the various chambers of your heart. A dye that can be seen on X-ray is injected into the blood through the tip of the catheter. The dye allows to study the flow of blood through the heart and blood vessels and see any blockages that exist. Arterial blood gas measurement. In this test, a blood sample is taken from an artery to measure oxygen, carbon dioxide, and pH (acidity) in the blood.. Cardiac enzymes. When cells in the heart die, they release enzymes into the blood called markers or biomarkers. Measuring these
  5. 5. markers can show whether the heart is damaged and the extent of the damage. Cardiac biomarkers (eg, creatine kinase, troponin, myoglobin) Coagulation profile (eg, prothrombin time, activated partial thromboplastin time) Tests that measure the function of various organs, such as the kidneys and liver. If these organs aren't working right, it could be a sign that they aren't getting enough blood and oxygen, which could be a sign of cardiogenic shock. Brain natriuretic peptide (BNP) may be useful as an indicator of congestive heart failure and as an independent prognostic indicator of survival. A low BNP level may effectively rule out cardiogenic shock in the setting of hypotension; however, an elevated BNP level does not rule in the disease. TreatmentEmergency life support- Emergency life support is a necessary treatment for most people who have cardiogenic shock. - Giving extra oxygen to breathe to minimize damage to your muscles. - If necessary, connected to a breathing machine (ventilator). - Receiving medications and fluid through an intravenous (IV) line in your arm. Medication Vasopressors- These drugs increase both coronary and cerebral blood flow present during the low-flow state associated with shock.
  6. 6. Dopamine and dobutamine are the drugs of choice to improve cardiac contractility. Dopamine (Intropin)- 5-20 mcg/kg/min IV continuous infusion; increase by 1-4 mcg/kg/min q10-30min to optimal response. Dobutamine (Dobutrex)- 5-20 mcg/kg/min IV continuous infusion. Phosphodiesterase enzyme inhibitors- These agents improve cardiac output in refractory hypotension and shock. Milrinone and inamrinone (formerly amrinone) may be used. Milrinone- Loading dose: 50 mcg/kg IV over 10 min infusion: 0.375-0.75 mcg/kg/min IV Continuous Inamrinone- Initial bolus: 0.75 mg/kg IV slowly over 2-3 min. Maintenance infusion: 5-10 mcg/kg/min IV; not to exceed 10 mg/kg; adjust dose according to response. Platelet Aggregation Inhibitors- Agents that irreversibly inhibit platelet aggregation may improve morbidity. Aspirin- 160-324 mg PO or chewed; Vasodilators- Smooth-muscle relaxers and vasodilators that can reduce systemic vascular resistance, allowing more forward flow and improving cardiac output. Nitroglycerin- 10-20 mcg/min IV infusion. Analgesics- Pain control Morphine sulphate Diuretics- drugs cause diuresis to decrease plasma volume and edema and thereby decrease cardiac output BP Furosemide (Lasix)- 40-80 mg/d IV/IM
  7. 7. Natriuretic peptide- These drugs cause arterial and venous dilation by binding to cyclic GMP receptor on vascular smooth muscle causing smooth muscle relaxation. Nesiritide- Initial 2 mcg/kg IV bolus over 30 min followed by continuous infusion at 0.01 mcg/kg/min Medical procedures Medical procedures to treat cardiogenic shock usually focus on restoring blood flow through heart. They include: Angioplasty and stenting. Emergency angioplasty opens blocked coronary arteries, letting blood flow more freely to heart. Doctors insert a long, thin tube (catheter) that's passed through an artery, usually in leg, to a blocked artery in heart. This catheter is equipped with a special balloon tip. Once in position, the balloon tip is briefly inflated to open up a blocked coronary artery. At the same time, a metal mesh stent may be inserted into the artery to keep it open long term, restoring blood flow to the heart. Depending on condition, doctor may opt to place a stent coated with a slowreleasing medication to help keep your artery open. Balloon pump. Depending on condition, doctors may choose to insert a balloon pump in the main artery of heart (aorta). The balloon pump inflates and deflates to mimic the pumping action of your heart, helping blood flow through. Surgery If medications and medical procedures don't work to treat cardiogenic shock, your doctor may recommend surgery. Coronary artery bypass surgery. Bypass surgery involves sewing veins or arteries in place at a site beyond a blocked or narrowed
  8. 8. coronary artery (bypassing the narrowed section). This restores blood flow to the heart. Surgery to repair an injury to your heart. Sometimes, an injury in heart, such as a tear in one of heart's chambers or a damaged heart valve, can cause cardiogenic shock. If an injury is causing cardiogenic shock, doctor may recommend surgery to correct the problem. Heart pumps. These mechanical devices, called left ventricular assist devices (LVADs), are implanted into the abdomen and attached to a weakened heart to help it pump. Implanted heart pumps can significantly extend and improve the lives of some people with endstage heart failure who aren't eligible for or able to undergo heart transplantation or are waiting for a new heart. Heart transplant. If heart is so damaged that no other treatments work, a heart transplant may be a last resort for treating cardiogenic shock.