Shock and dehydration

2 Shock and dehydration

Shock and dehydration are both commonly seen in emergency practice and both require fluid therapy as a crucial part of their management (see Ch. 4). However, they represent different pathophysiological processes and have different clinicopathological findings. Understanding these differences is essential to ensuring that the most appropriate management is implemented.

Hypoperfusion and Shock

Organs and peripheral tissues rely on an adequate intravascular fluid space (adequate perfusion) for the delivery of oxygen and nutrients and the removal of by-products of tissue metabolism. ‘Hypoperfusion’ describes a situation in which there is a decrease in the blood supply to an organ or tissue. Although this can occur solely on a local level, it is seen most commonly in the context of a global (systemic) reduction in blood supply.

The term ‘shock’ is used clinically to describe the condition of a patient in which this global hypoperfusion has reached a certain level of severity, sufficient for the patient to manifest a number of characteristic clinical findings. This usually occurs when the reduction in blood supply is severe enough to cause inadequate oxygen delivery to the cells and thereby inadequate energy production. If the degree of shock is sufficiently severe or prolonged, irreversible cell damage can occur and treatment is invariably unsuccessful.

Causes of hypoperfusion

The mechanisms of hypoperfusion and shock can be divided into four categories. However, it is important to remember that more than one type can exist in the same patient at the same time, and that they share some common changes and derangements at a cellular level.

Obstructive shock

Systemic hypoperfusion occurs due to obstruction of blood flow from the heart or venous return to the heart; the most common example of this in small animals is pericardial tamponade.

Causes of systemic hypoperfusion in companion animals are listed in Table 2.1.

Table 2.1 Causes of systemic hypoperfusion in dogs and cats

Type of hypoperfusion Causes




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Sep 3, 2016 | Posted by in SMALL ANIMAL | Comments Off on Shock and dehydration

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