Blood and Introduction Shock
1) Introduction
Shock is a syndrome, in which oxygen supply to various tissues and organs of the body are interrupted.1 It represents the final common pathway, of a variety of potentially lethal diseases and conditions.2,3 It is a medical emergency, involving acute tissue hypoperfusion and cellular destruction, and will ultimately lead to organ failure and death, if left untreated.2,3 Despite a huge amount of research into understanding the syndrome, it remains a very common clinical condition, carrying high morbidity and mortality rates.2 This essay reviews different causes and types of shock, and illustrates the pathophysiological mechanisms underlying the condition, using shock caused by heart failure as an example. It also touches on the hyperlactaemia and the raised central venous pressure (CVP) associated with shock.
2) Pathophysiology of shock
Circulatory shock is defined as the failure of circulatory system to provide adequate perfusion of oxygen to peripheral tissues and organs of the body. It can be caused by a reduction in blood flow (hypovolemic shock), cardiac pump failure (cardiogenic shock), an obstruction to the circulatory system (obstructive shock), or a fall in peripheral resistance, due to excessive vasodilation (distributive shock). Each type begins with either a reduced cardiac output (CO) or a reduced venous return, with the exception of distributive shock (fig. 1).4-6
2.1 Cardiogenic Shock- occurs when the heart fails to pump effectively to meet the oxygen demand of the body, resulting in a fall in CO, and consequently, a fall in systemic arterial blood pressure. There are many causes that can give rise to this type of shock such as cardiac dysrhythmia, valvular damage, and cardiac surgery but myocardial infarction particularly with left ventricular failure remains the most common cause of cardiogenic shock.5-7
2.2 Hypovolemic Shock- is characterised by a fall in the circulating blood volume, which leads to a reduction in
Shock is a syndrome, in which oxygen supply to various tissues and organs of the body are interrupted.1 It represents the final common pathway, of a variety of potentially lethal diseases and conditions.2,3 It is a medical emergency, involving acute tissue hypoperfusion and cellular destruction, and will ultimately lead to organ failure and death, if left untreated.2,3 Despite a huge amount of research into understanding the syndrome, it remains a very common clinical condition, carrying high morbidity and mortality rates.2 This essay reviews different causes and types of shock, and illustrates the pathophysiological mechanisms underlying the condition, using shock caused by heart failure as an example. It also touches on the hyperlactaemia and the raised central venous pressure (CVP) associated with shock.
2) Pathophysiology of shock
Circulatory shock is defined as the failure of circulatory system to provide adequate perfusion of oxygen to peripheral tissues and organs of the body. It can be caused by a reduction in blood flow (hypovolemic shock), cardiac pump failure (cardiogenic shock), an obstruction to the circulatory system (obstructive shock), or a fall in peripheral resistance, due to excessive vasodilation (distributive shock). Each type begins with either a reduced cardiac output (CO) or a reduced venous return, with the exception of distributive shock (fig. 1).4-6
2.1 Cardiogenic Shock- occurs when the heart fails to pump effectively to meet the oxygen demand of the body, resulting in a fall in CO, and consequently, a fall in systemic arterial blood pressure. There are many causes that can give rise to this type of shock such as cardiac dysrhythmia, valvular damage, and cardiac surgery but myocardial infarction particularly with left ventricular failure remains the most common cause of cardiogenic shock.5-7
2.2 Hypovolemic Shock- is characterised by a fall in the circulating blood volume, which leads to a reduction in