Shock

The main purpose of a cardiovascular system examination in an emergency patient is to detect the presence of shock. In the veterinary field, shock is defined as a lack of oxygen delivery to the tissues. This occurs most commonly secondary to a problem of the circulatory system and hypoperfusion.

Decreased perfusion resulting in decreased oxygen delivery to the tissues, will have significant effects on the organs, especially the heart, brain and kidneys. If prolonged, it will lead to organ failure and death.

Four major types of shock are recognized

• Hypovolaemic shock is the most common form and is characterized by:
  • Tachycardia
  • Prolonged capillary refill time
  • Pale mucous membranes
  • Low blood pressure (if severe)
• In cardiogenic and obstructive shock the findings are very similar to those in hypovolaemic shock, but arrhythmias may also be present.
• In distributive shock, of whatever cause, there is one important difference: as the body is unable to constrict its blood vessels normally, the mucous membranes appear abnormally red.

A drop in blood pressure is a late change during shock, as the body has a number of mechanisms that try to maintain blood pressure. A mean arterial blood pressure of <60 mmHg is of considerable concern, as there may be damage to vital organs such as the brain,heart and kidneys.


Management of shock

The management of shock varies depending on the cause. Most patients with hypovolaemic or distributive shock will require some form of intravenous fluid therapy.

If bleeding is an obvious cause of shock, efforts should be made to arrest the haemorrhage. Methods of arresting haemorrhage include:

• Direct digital pressure: Ensure that gloves are worn and apply pressure for at least 5 minutes.
• Artery forceps (haemostats): If the bleeding vessel can be visualized it may be possible to clamp it directly with artery forceps.
• Pressure dressing: Apply direct pressure over the bleeding area using an absorbent pad and cohesive bandage.
• Cold compress: Constricts the blood vessels, reducing the haemorrhage.

Patients with shock are also likely to benefit from oxygen supplementation and being kept in a stress-free, comfortable environment. They may have a reduced body temperature but should be re-warmed slowly and only after fluid therapy has been started. Patients with shock require careful and close monitoring, especiallyin the first few hours after presentation.