Heart Failure and Circulatory Shock

Heart Failure
Function of the heart
Move deoxygenated blood from the venous system through the right heart into the pulmonary circulation
Move the oxygenated blood from the pulmonary circulation through the left heart into the arterial system
Right and left heart must maintain an equal output to function properly
Right Heart Failure
Represents failure of the right heart to pump blood forward into the pulmonary circulation
Blood backs up in the systemic circulation
Causes peripheral edema and congestion of the abdominal organs
Left Heart Failure
Represents failure of the left heart to move blood from pulmonary circulation into system circulation
Blood backs up in the pulmonary circulation
Causes of Heart Failure
Myocardial disease
Cardiomyopathies
Myocarditis
Coronary insufficiency
Myocardial infarction
Causes of Heart Failure (cont.)
Valvular heart disease
Stenotic valvular disease
Regurgitant valvular disease
Congenital heart defects
Constrictive pericarditis

Cardiac Output
Cardiac output: the amount of blood the heart pumps each minute
Cardiac output = heart rate x stroke volume
Heart rate: how often the heart beats each minute
Regulated by a balance between the activity of the sympathetic sympathetic nervous system (increases heart rate), and the parasympathetic nervous system (slows heart rate)
Cardiac Output (cont.)
Stroke volume: how much blood the heart pumps with each beat
A function of preload, afterload, and cardiac contractility


Maintenance of Cardiac Reserve in Heat Failure
Compensatory or adaptive mechanisms
Frank-Starling mechanism
Activation of neurohumoral influences such as the sympathetic nervous system
The renin-angiotensin-aldosterone mechanism
Natriuretic peptides
Locally-produced vasoactive substances
Myocardial hypertrophy and remodeling
Causes of Heart Failure
Acute myocardial infarction
Hypertension
Degenerative conditions of the heart muscle known collectively as cardiomyopathies
Excessive work demands (hypermetabolic states)
Volume overload (renal failure)
Descriptions of Heart Failure
High-output or low-output failure
Systolic or diastolic failure
Right-sided or left-sided failure


Causes of Right-Sided Heart Failure
Conditions that restrict blood flow into the lungs
Stenosis or regurgitation of the tricuspid or pulmonic valves
Right ventricular infarction
Cardiomyopathy
Persistent left-sided failure
Acute or chronic pulmonary disease (cor pulmonale)
Causes of Left-Sided Heart Failure
Acute myocardial infarction
Cardiomyopathy
Manifestations of Heart Failure
Physiologic effects of the impaired pumping ability of the heart
Decreased renal blood flow
Activation of the sympathetic compensatory mechanisms
Signs and Symptoms of Heart Failure
Fluid retention and edema
Shortness of breath
Fatigue and limited exercise tolerance
Cyanosis
Cachexia and malnutrition
Distention of the jugular veins in right-sided failure
Diaphoresis and tachycardia


Functional Classification of Patients with Heart Disease (NY Heart Association)
Class I: patients with cardiac disease but without resulting limitations in physical activity
Class II: patients with heart disease resulting in slight limitations of physical activity
Class III: patients with cardiac disease resulting in marked limitation of physical activity
Class IV: patients with cardiac disease resulting in inability to carry out any physical activity without discomfort
Goals of Treatment for Chronic Heart Failure
Relieving the symptoms and improving the quality of life
Long-term goal:
Slowing, halting, or reversing the cardiac dysfunction
Treatment Measures for Chronic Heart Failure
Correction of reversible causes
Surgical repair of a ventricular defect or an improperly functioning valve
Pharmacologic and non-pharmacologic control of afterload stresses
Modification of activities and lifestyle consistent with the functional limitations of a reduced cardiac reserve
Use of medications to improve cardiac function and limit excessive compensatory mechanisms

Acute Pulmonary Edema
Capillary fluid moves into the alveoli, causes lung stiffness, makes lung expansion more difficult, and impairs the gas exchange function of the lung
With the decreased ability of the lungs to oxygenate the blood, the hemoglobin leaves the pulmonary circulation without being fully oxygenated
Results in shortness of breath and cyanosis

Causes of Cardiogenic Shock
Damage to the heart from myocardial infarction
Ineffective pumping caused by cardiac arrhythmias
Ventricular septal defect
Ventricular aneurysm
Acute disruption of valvular function
Problems associated with open heart surgery
Classification of Circulatory Shock
Hypovolemic
Loss of whole blood
Loss of plasma
Loss of extracellular fluid
Obstructive
Inability of heart to fill properly
Obstruction to outflow from the heart
Classification of Circulatory Shock (cont.)
Distributive
Loss of sympathetic vasomotor tone
Presence of vasodilating substance in the blood
Presence of inflammatory mediators


Causes of Hypovolemic Shock
Diminished blood volume with inadequate filling of the vascular compartment
Acute loss of 15% to 20% of the circulating blood volume
External loss of whole blood (e.g., hemorrhage), plasma (e.g., severe burns), or extracellular fluid (e.g., gastrointestinal fluids lost in vomiting or diarrhea)
Internal hemorrhage or from third-space losses
Stages of Hypovolemic Shock
Initial stage: the circulatory blood volume is decreased, but not enough to cause serious effects
Second stage: Compensatory mechanisms are able to maintain blood pressure and tissue perfusion at a level sufficient to prevent cell damage
Third stage: Blood pressure begins to fall, blood flow to the heart and brain is impaired, capillary permeability is increased, fluid begins to leave the capillaries, blood flow becomes sluggish, and the cells and their enzyme systems are damaged
Stages of Hypovolemic Shock (cont.)
Fourth and final stage: irreversible shock, even though the blood volume may be restored and vital signs stabilized, death ensues eventually

Types of Shock
Obstructive shock
Distributive shock
Neurogenic shock
Anaphylactic shock
Sepsis and septic shock
Complications of Shock
Acute respiratory distress syndrome
Acute renal failure
Gastrointestinal complications
Disseminated Intravascular Coagulation
Multiple organ dysfunction syndrome
Signs and Symptoms of Heart Failure in Infants and Children
Fatigue
Effort intolerance
Cough
Anorexia
Abdominal pain