Recognizing shock (Proceedings)


Recognizing shock (Proceedings)

Apr 01, 2010

Definition of shock

Shock is the general term used to describe several conditions that lead to inadequate perfusion of the tissues. There are multiple types of shock, but the common derangement in all forms is inadequate delivery of oxygen and nutrients to the cells and inadequate elimination of metabolic byproducts.

Types of Shock

               • Cardiogenic shock results from an inability of the heart to propel the blood through the circulation. Cardiogenic shock can result from anything that interferes with the ability of the heart to fill or pump blood. Examples of this type of shock are heart failure, arrhythmias, pericardial effusion, or tension pneumothorax.

               • Hypovilemic shock results from inadequate circulating blood volume. Causes of hypovolemia include blood loss, water loss (severe dehydration) and third spacing of body fluids.

               • Distributive shock results from massive vasodilation. The consequence of this vasodilation is that the amount of blood in circulation is inadequate to fill the vascular space, creating an effective hypovolemia. The most common type of distributive shock is septic shock. Because patients with "septic shock" do not always have a source of infection, a more recent term to describe the condition seen in septic shock is the systemic inflammatory response syndrome (SIRS). In septic shock, the immune system is activated and inflammatory mediators are produced that cause vasodilation. In addition to vasodilation, these inflammatory mediators lead to stimulation of coagulation, fever, release of more mediators, tissue injury and increased vascular permeability. Septic shock can also progress to hypovolemic and cardiogenic forms of shock. Distributive shock can also result from neurogenic, anaphylactic, or drug induced systemic vasodilation.

               • Hypoxic shock results from tissue hypoxia from other causes such as pulmonary disease, anemia or toxins that interfere with oxygen delivery or metabolism.

Case example

You are presented with a 10 year old female, spayed, 40 kg Boxer with a 4-day history of vomiting. She had a mast cell tumor removed 4 days ago and was treated with an anti-emetic, an antihistamine and steroids for 2 days.

Physical exam findings

Table 1
               - Temperature: 103.1°F (normal 100.5-102.5)
               - Pulse rate: 160 bpm (normal for a large dog 60-120)
               - Pulse quality: snappy
               - Mucous membranes: pale pink
               - Capillary refill time: 2.5 sec
               - Respiratory rate: 60 bpm (normal 20-30), inspiratory dyspnea, dull lung sounds
               - No heart murmur
               - Hydration: 7% dehydrated
               - Mentation: depressed
               - Abdomen: distended