Introduction
Shock occurs when there is an insufficient supply of oxygen to cells and tissues (Silverman, 2005). A condition characterized by insufficient oxygen supply to tissues is called Hypoperfusion (Silverman, 2005). Hypoperfusion can be caused by impairment of blood flow and oxygen delivery to tissues. This condition can also occur as a result of an increase in the amount of oxygen needed for utilization in tissues if the body fails to initiate mechanisms necessary to supply the additional oxygen. Oxygen is necessary for normal metabolism to take place (Silverman, 2005). Therefore, an insufficient supply of oxygen to tissues reduces or stops metabolism. The body responds to insufficient oxygen supply to cells by initiating systemic stress response (Silverman, 2005). Silverman (2005) observes that this can be done by increasing heart rate as well as initiating peripheral vasoconstriction. Sometimes hypoperfusion can continue until physiological compensation mechanisms are exhausted. Some organs fail to function after this exhaustion, causing irreversible damages. This condition can lead to death (Silverman, 2005).
Cardiogenic Shock
Cardiogenic shock results from impaired or insufficient myocardial contraction (Diez & Varon, 2009). Myocardial contraction is responsible for pumping blood out of the heart. Impairment of such contractions compromises the flow of blood to tissues (Diez & Varon, 2009). Myocardial contractility can be impaired for many reasons, including myocardial infarction and other diseases of the heart (Diez & Varon, 2009).
The left ventricle of the heart is responsible for pumping blood out of the heart (Diez & Varon, 2009). Malfunctioning of this ventricle, therefore, interferes with blood flow. The result will be a reduction in the amount of blood exiting the heart per heartbeat, causing a reduction in stroke volume (Diez & Varon, 2009). As a result, the heart rate increases in response to a reduction in the amount of blood exiting the heart. Hypoperfusion takes place when the heart rate increases to the maximum without fully compensating for the reduced blood outflow. The inability to pump blood out of the heart leads to its accumulation in the left ventricle and left atrium, causing an increase in pressure (Diez & Varon, 2009). This pressure causes an increase in pulmonary capillary pressure due to obstruction (Diez & Varon, 2009).
Hypovolemic Shock
Hypovolemic shock is caused by plasma loss resulting from several reasons including burns, lack of sufficient water in the body and bleeding (Diez & Varon, 2009). A reduction in the number of fluids available in the body also causes a reduction in the number of fluids available in blood vessels. Consequently, there will be less blood flowing to the heart and a slowdown in the ventricular filling. The resulting reduction in the amount of blood available in the ventricle for pumping reduces stroke volume (Diez & Varon, 2009). The heart rate will increase to make up for the reduction in the amount of blood exiting the heart. Hypoperfusion takes place when the heart rate reaches the maximum limit without fully compensating the reduced blood outflow (Diez & Varon, 2009).
Neurogenic Shock
In neurogenic shock, sympathetic impulses responsible for stimulating vasoconstriction are interfered with, causing uncontrolled vasodilation of some vessels (Diez & Varon, 2009). According to Diez and Varon (2009) this scenario is caused by a number of factors including injury to the spinal cord, anxiety and pain. Venous dilation leads to accumulation of blood in distensible veins due to lack of pressure to move it to the larger veins (Diez & Varon, 2009). As a result of this accumulation, there will be a reduction in the amount of blood going back to the heart, causing a drop in stroke volume, cardiac output and blood pressure. On the other hand, arterial dilation reduces peripheral vascular resistance (Diez & Varon, 2009). The heart will, consequently, pump blood with reduced energy. This leads to insufficient force to drive blood, oxygen and nutrients to tissues because of a reduction in peripheral pressure. To some extent, this also leads to accumulation of blood in the arteries and, consequently, reduces the amount of blood flowing to the heart (Diez & Varon, 2009).
Anaphylactic Shock
Sometimes allergic reaction to foreign substances can cause shock (Dutton, Mackenzie & Scalea, 2002). According to Dutton et al. (2002), bodies initiate production of antigens when they sense foreign substances. After developing antigens, any further exposure to similar antibodies leads to creation of antigen-antibody complex in the affected body (Dutton et al., 2002). The formed complex has the ability to initiate production of chemicals that make blood vessels to dilate. This reduces the amount of blood flowing back to the heart (Dutton et al., 2002). In addition, there will be uncontrolled flow of fluids and other substances to the interstitial space due to an increase in the permeability of capillaries (Dutton et al., 2002). This results to severe interstitial edema.
Septic Shock
Sepsis is common in people with severe medical conditions (Dutton et al., 2002). The condition is associated with bacterial and fungal infections. Sepsis that advances in severity and compromises the functioning of several organ systems is referred to as septic shock. Septic shock occurs when sepsis progresses to a point where it affects more than one organ systems (Dutton et al., 2002). When an infection is detected in the body, immune activities are triggered. Some chemicals such as cytokines and vasodilators are produced to bring the situation back to normal (Dutton et al., 2002). Instate of controlling the situation, such chemicals cause more destruction in septic shock. In an attempt to protect itself, the intruding organism produces endotoxins that cause further organ destruction (Dutton et al., 2002). This leads to peripheral vasodilation and interstitial edema, resulting to serious reduction in the amount of blood flowing to the heart (Dutton et al., 2002). The ability of the cells to receive oxygen can also be compromised. The body tries to restore normalcy by increasing the heart rate. When the heart rate increases to the maximum, hypoperfusion takes place, leading to failure of some organs (Dutton et al., 2002).
Pre-hospital Treatment
Shock cases should be reported to a doctor for immediately emergency services (Cocchi, Kimlin, Walsh & Donnino, 2007). In the case of hypovolemic shock, further bleeding should be stopped by appropriate first aid. The patient should be monitored for breathing problems so that resuscitation can be done whenever it is necessary. The patient should also rest in shock position in a well-ventilated place (Cocchi, et al., 2007).
Symptoms of Shock
Shock is characterised by very low blood pressure, weakness, nauseous, dizziness and confusion. Shock patients also experience chest pain and increased heart rates. The patients also experience a lot of sweating with faster and shallow breathing (Cocchi, et al., 2007).
Conclusion
Shock occurs when there is no sufficient supply of blood to cells and tissues. The body responds to hypoperfusion by increasing the heart rate. Ones the heart rate increases to the maximum, hypoperfusion worsens. This stops vital metabolic processes. As a result, tissues become severely damaged. Shock can be classified into five depending on the cause of hypoperfusion. Shock is a medical emergence and a doctor should be contacted immediately after it happens. First aid should also start immediately while monitoring the state of the patient.
References
Cocchi, M. N, Kimlin E., Walsh M. & Donnino, M.W. (2007). Identification and resuscitation of the trauma patient in shock. Emergency medicine clinics of North America 25 (3): 623–42.
Diez, C. & Varon, A. J. (2009). Airway management and initial resuscitation of the trauma patient. Current opinion in critical care Nursing,15 (6): 542–7.
Dutton, R.P., Mackenzie C.F. & Scalea T.M. (2002). Hypotensive resuscitation during active haemorrhage: Impact on in-hospital mortality. Journal of Trauma;52:41-6.
Silverman, A. (2005). Shock: A Common pathway for life-threatening paediatric illnesses and injuries. Pediatric Emergency Medicine Practice 2 (10): 7-19.