Shock

Question 1

What is the definition of shock?

Answer 1

An imbalance between oxygen delivery and oxygen consumption within the tissues

Question 2

Tissue oxygen content is affected by three main things?

Answer 2

Blood oxygen content

Blood flow (perfusion)

Cardiac output (CO)

Question 3

Hypoxemic Shock - due to?

Answer 3

Decreased oxygen delivery due to reduced oxygen content of arterial blood

Decreased haemoglobin
Dysfunctional haemoglobin

Impaired lung function

Question 4

Circulatory shock - due to?

Answer 4

Decreased oxygen delivery due to reduced blood circulation

Hypovolaemic
Cardiogenic
Distributive shock
Obstructive shock

Question 5

Metabolic shock - due to?

Answer 5

Decreased mitochondrial cellular respiration (ATP production from oxygen)

Hypoglycaemia
Toxins (e.g. cyanide toxicity, sepsis)

Question 6

What shock types are there based on “classification by circulatory system effects”?

4 types

Answer 6

• Hypovolaemic shock
• Cardiogenic shock
• Obstructive shock
• Distributive shock

Question 7

What is hypocolaemic shock?

Answer 7

Decreased circulating blood volume

• Haemorrhage - trauma or coagulopathy resulting in significant blood loss, and therefore, volume loss
• Severe dehydration e.g. due to vomiting and diarrhoea (high losses), occurs with concurrent hypovolaemia as once the extravascular space is depleted losses occur from the intravascular space as well
• Burns

Question 8

What is cardiogenic shock?

Answer 8

Decreased ability of the heart to pump blood forward into the arteries (decreased CO)

• Cardiomyopathy
• Severe arrhythmia
• Valvular disease

Question 9

What is Obstructive shock?

Answer 9

• Pericardial disease (cardiac tamponade) leading to reduced filling, and therefore reduced cardiac output.
• Pulmonary thrombo-embolism – can result in impeded venous return to the heart
• Intra-abdominal hypertension – peritoneal effusion, organomegaly, GDV – results in reduced venous return

Question 10

What is distributive shock?

Answer 10

Due to an inappropriate vasodilation or lack of appropriate vasoconstriction leading to increased vascular capacitance, blood pooling in the vascular space, decreased venous return to the heart and decreased CO.

Question 11

Clinical presentation of shock?

6 clinical signs

Answer 11

• Tachycardia (bradycardia in cats),
• Pale mucous membrane,
• Prolonged capillary refill time (CRT),
• Pulses initially increase in amplitude then decrease,
• Hypothermia,
• Altered mentation

Question 12

Pathophysiology hypovolaemic shock - what three overhauling stages are there?

Answer 12

1. Compensatory shock - Patients often appear stable and have normal blood pressure due to the compensatory effects of the increased sympathetic nervous system
2. Decompensatory shock - Most of the body has inadequate oxygen and blood supply and will convert to anaerobic metabolism.
3. End stage shock - all organs has hypoxia

Question 13

Treatment of hypovolemic shock - 4 things?

Answer 13

• Restore effective circulating volume volume (by intravenous fluids)
• Enhance oxygen delivery to tissues
• Normalise cardiac output
• Treat underlying cause of shock