The organs need oxygen and nutrients carried in blood in order to function. The cells of the body use oxygen and glucose together to make fuel in the process of aerobic metabolism. If deprived of oxygen, the cells can compensate for a short time by using only glucose without oxygen in the process of anaerobic metabolism. Shock is defined as the inadequate perfusion of the organs with blood, such that they are unable to function. The result is a switch to anaerobic metabolism, leading to the buildup of lactic acid. Excess acid in the tissues is known as acidosis.
Causes
Organs with a high metabolism--in high need for fuel from oxygen and glucose, such as the brain, liver, heart and kidneys--require more oxygen and are therefore highly susceptible to oxygen deprivation. The lungs, heart, blood vessels and blood are crucial in the delivery of oxygen to the tissues. The lungs take up oxygen from the air and deliver it to the blood. The heart delivers the blood to the lungs and body organs. The blood vessels transmit the blood, and the blood carries the oxygen in red blood cells. Problems in these body systems lead to shock, according to the University of Pennsylvania's Critical Care Medicine Tutorials.
Types
One way to categorize shock is to divide the cardiovascular system into the pump, the pipes and the fuel it delivers. The pump is analogous to the heart; shock caused by heart dysfunction is called cardiogenic shock. The pipes are the blood vessels. Shock caused by problems in the blood vessels is known as distributive shock. Subtypes of distributive shock include neurogenic shock, which may be caused by a severed spinal cord. In this type, nerves signal the blood vessels to dilate too much and drop the blood pressure. In septic shock, chemicals released by bacteria or other pathogens and the immune system dilate the blood vessels. Finally, problems in the fuel correspond to loss of blood, known as hypovolemic shock.
Diagnosis
According to the National Institutes of Health, evidence for shock can be found on physical exams and labs due to organ dysfunction. Inadequate delivery of blood to the brain leads to mental status changes from confusion to unconsciousness. Changes in blood flow to the skin can make it warm and red or cool and pale. Kidney failure can decrease urine output. Anaerobic metabolism makes lactic acid that can be measured in the blood.
Treatment
The Merck Manual says treatment depends on the type of shock. Most types require fluids such as normal saline or blood to be given through the veins. If the blood pressure doesn't respond adequately to fluids, drugs can be given to increase the blood pressure and the output of the heart. Examples include norepinephrine and dopamine. Infections must be treated with appropriate antibiotics.
Complications
Complications tend to arise from persistent damage to organs. Kidney failure may persist after the resolution of shock, as can liver damage. Parts of the intestine may be permanently damaged and must be removed. Even though there are many treatments for shock, there is still a relatively high risk of death.
