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Shock is a common condition that affects about one third of patients who are admitted in the intensive care unit (ICU) [1]. It is a highly prevalent condition in the ICU, and hence, is a major concern for critical care, as it requires immediate treatment [2].
Shock is defined as “an acute clinical life-threatening and generalized syndrome of acute circulatory failure associated with inadequate oxygen utilization by the cells” [1]. Hence, the various organs and tissues in the body are damaged due to the decreased blood supply which results in decreased oxygen and nutrients being delivered [2]. Furthermore, this condition has high mortality and morbidity rates as it can lead to multi-organ failure if it is not identified and managed immediately [3]. Hence, it is important to recognize the initial signs of shock, and the pathophysiology behind the cause to provide the necessary treatment.
Shock is mainly classified into four different categories. These include hypovolemic shock, distributive shock, cardiogenic shock, and obstructive shock [2]. Hypovolemic shock is characterized by a decreased blood volume leading to decreased oxygen delivery and cardiac output [4]. Some causes include hemorrhage, trauma, GI losses and burns [4]. Distributive shock is present with systemic vasodilation from a decrease in vascular tone [4]. The most common cause of distributive shock is sepsis. Other causes include anaphylaxis, adrenal insufficiency, transfusion reactions, liver failure and neurogenic shock [4].
Cardiogenic shock is present when there is a decreased blood flow due to a defect in cardiac function. This may be from an intrinsic defect in the heart muscle or in the valves [4]. Some causes of cardiogenic shock are myocardial infarction, symptomatic bradycardia, valvular disease, heart blocks and end stage heart failure [4]. Obstructive shock is caused by a mechanical obstruction that interferes with blood flow into and/or out of the heart [4]. Causes of obstructive shock include pulmonary embolism, tension pneumothorax, and pericardial tamponade [4].
Furthermore, each of these types vary in their incidence rates, mortality rates, and potentially vary in their management. According to a European study conducted, “septic shock [accounted] for 62% of cases, cardiogenic shock [for] 17% and [hypovolemic shock for] 16%” of the cases [1]. Mortality rates for septic shock “ranged between 40–50%, and in some severe cases, the death rate was as high as 80%” [1]. Mortality rates for cardiogenic shock are still as high as 40-70% despite medical advancements [1]. Hence, it is vital to recognize the type of shock involved and to proceed with the appropriate treatment immediately.
The initial step for management of shock is recognition of the symptoms and stabilization of the patient. Physicians should “assess for immediate life-threatening circumstances” such as issues with airways, breathing and circulation [4]. The patient should then be placed on a cardiac monitor, pulse oximeter and have appropriate IV access to efficiently address any issues that may come up [4]. In addition, recognizing the type and cause of shock may be determined from medical history, physical examination, and clinical investigations conducted after. For example, early clinical signs include changes in “skin color and skin temperature, heart rate, rhythm, electrocardiogram (ECG), capillary re-fill test, urine output, mental status, the effect of body position on the blood pressure,” etc. [1]. After the initial recognition, hemodynamic stabilization is critical as this can prevent organ dysfunction and failure [3].
Steps to stabilize the patient may include administration of oxygen to increase oxygen delivery to various organs, fluid resuscitation to improve blood flow, administration of vasoactive agents when necessary. Ventilatory support can be through a mask or from intubation, and is primarily used to increase “oxygen delivery and prevent pulmonary hypertension” [3]. Fluid therapy is essential to manage all four types of shock as it can increase the blood flow and volume, but it should be monitored to prevent excess intake leading to edema [3]. Vasoactive agents can include vasopressors such as norepinephrine, epinephrine and dopamine, inotropic agents such as dobutamine and enoximone, and vasodilators such as nitrates [3]. Vasopressors are used when the patient has continued severe hypotension despite fluid therapy [3]. Inotropic agents, especially dobutamine, are used to increase cardiac output by increasing the contractility of the heart and vasodilators are used to improve blood flow and perfusion to various tissues [3].
Once the patient is stabilized from any life-threatening circumstances, a focused history and physical examination are conducted to determine the type of shock and the specific cause [4]. There may be different examinations to conduct based on the type of shock the patient has. For example, in a hypovolemic shock the physical examination would be focused on “bilateral breath sounds, abdominal examination, pelvic stability, extremity and back examinations” along with imaging as needed, whereas in a distributive shock the physical examination will be more focused on “extremity strength, spine step-offs, rectal tone, long bone or pelvic deformities” [4]. In an obstructive shock the physical examination would focus on bilateral breath sounds, heart sounds and thoracic ultrasound [4].
In a cardiogenic shock patient, the diagnostic tools would be bedside cardiac ultrasound, ECG, and troponin level [4]. Other diagnostic tests that may be conducted are laboratory studies such as lactate levels, imaging such as ultrasounds, chest X-rays and CT scans, echocardiography and others as needed [4]. These focused exams and diagnostic studies help to determine what type of shock a patient has and the cause of the specific type. Furthermore, additional treatment may be administered depending on the type. For instance, antibiotics are usually administered to patients with septic shock whereas antihistamines and glucocorticoids are administered to patients with anaphylactic shock [4]. Further measures may also be taken to address any complications and to prevent relapse/ recurrence.
Shock is a highly life-threatening condition that affects patients globally. It is associated with high morbidity and mortality rates, and requires immediate treatment. It is vital that a physician can recognize the initial signs of shock and efficiently stabilize the patient's condition to determine the type and cause in the specific patient. Hence, the physician needs to recognize the differences between the types of shock and potential differences in management to treat the patient efficiently and give the patient their best possible outcomes.
References
1. Hendy, A., & Bubenek-Turconi, Ş. I. (2016). The Diagnosis and Hemodynamic Monitoring of Circulatory Shock: Current and Future Trends. Journal of critical care medicine (Universitatea de Medicina si Farmacie din Targu-Mures), 2(3), 115–123. https://doi.org/10.1515/jccm-2016-0018
2. Aushev, A., Ripoll, V. R., Vellido, A., Aletti, F., Pinto, B. B., Herpain, A., Post, E. H., Medina, E. R., Ferrer, R., Baselli, G., & Bendjelid, K. (2018). Feature selection for the accurate prediction of septic and cardiogenic shock ICU mortality in the acute phase. PloS one, 13(11), e0199089. https://doi.org/10.1371/journal.pone.0199089
3. Vincent, J. L., & De Backer, D. (2013). Circulatory shock. The New England journal of medicine, 369(18), 1726–1734. https://doi.org/10.1056/NEJMra1208943
4. Richards, J. B., & Wilcox, S. R. (2014). Diagnosis and management of shock in the emergency department. Emergency medicine practice, 16(3), 1–23.
Contributors
Author: Bhagya Arikala
Editor: Kayjah Taylor
Health Scientist: Bhagya Arikala
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