Shock
What is Shock?
In 1872 S.D. Gross defined shock as "a manifestation of a rude unhinging of the machinery of life." A recent veterinary textbook defines shock as "the clinical state resulting from an inadequate supply of oxygen to the tissues or an inability of the tissues to properly use oxygen." Many attempts have been made to define shock, but because it is such a complex disorder, no single definition has been successful.
Shock and the Cardiovascular System
To gain a basic understanding of shock, one must first have an understanding of the normal cardiovascular system of dogs and cats. Envision the cardiovascular system as the closed circuit diagrammed on the following page, consisting of a pump (the heart) and a series of stretchable tubes (blood vessels). The system is filled to capacity with a fluid (blood) which circulates through the tubes delivering fuel (oxygen and other metabolic substances) and picking up trash (carbon dioxide and other metabolic waste). In order to be efficient, the pump must be able to deliver a proper amount of the fluid and there must be enough fluid to completely fill and stretch the system of tubes. An insult to any part of this system that results in lower fuel delivery, excess fuel burning, and/or excess waste accumulation may result in a condition analogous to shock.
An animal who has been hit by a car is in danger of suffering life-threatening shock. Shock will ultimately lead to involvement of the entire cardiovascular system and, if left unchecked, will result in the death of the pet. For example, if a pet has been hit by a car and sustains injuries that cause blood loss, there will be a deficiency in the fluid that carries fuel. The pump (heart) operates on this fuel. Since an inadequate fuel supply is being delivered to the pump, it begins to fail. As the pump fails, it is unable to circulate the fluid that is present, so even less fluid is delivered. Without adequate fuel, the blood vessels become inelastic and are less efficient in fluid movement -- again, less fuel. Eventually, these events will result in total collapse of the cardiovascular system and the death of the pet.
Causes of Shock
The most common causes of shock in our pets is trauma: e.g., fights with other animals, being struck by a car, and gunshots. Other causes include poisoning, insect stings, fluid loss from vomiting and/or diarrhoea, infections, burns, and lack of oxygen caused by heart failure or obstruction of airways (pneumonia or choking, for example). Regardless of the cause, shock is life-threatening. Immediate identification is crucial.
The Circulatory System
Oxygenated blood leaves the heart through the left ventricle (A), and circulates to the body (F) through the arterial system where its precious oxygen is distributed. The deoxygenated blood then travels to the right atrium (C) and the right ventricle (D) of the heart, where it is pumped to the lungs (E) to pick up more oxygen. The newly oxygenated blood returns to the heart via the left atrium (F), travels to the left ventricle, and the circulatory cycle begins all over again.
Signs of Shock
Early Stages of Shock
** Bright red gums.
** Very rapid capillary refill time.
** The pet may be either excited or subdued.
** Rapid heart rate.
** Pulse not difficult to find. Middle Stages of Shock
** Gums appear pale or "muddy".
** Abnormally long capillary refill time.
** The heart rate is frequently above normal.
** The pulse weakens and may be difficult to locate.
** The pet will most likely be subdued, depressed and weak.
** Respiration often shallow and rapid (but may be normal).
** Rectal temperature often below normal (may be normal or even elevated).
Late Stages of Shock
** Gums extremely pale or show a bluish discoloration, and are often "blotchy" in appearance.
** Capillary refill time is longer (sometimes longer than 3 to 4 seconds).
** *Heart rate is probably elevated and irregular, but may be normal or below normal as heart muscle begins to fail.
** The pulse will be very weak and difficult or impossible to locate.
** Respiration may be slow or rapid, shallow or deep.
** The eyes may take on a glazed appearance and appear not to focus normally.
** Mental condition deteriorates from depression to stupor to coma.
** Rectal temperature will be below normal, often critically so. Treatment of Shock:
What to Do
Successful treatment of a patient in shock involves prompt recognition of the signs, immediate initiation of first aid procedures, and safe and rapid transport to the veterinary facility for definitive treatment.
First aid procedures include:
** Providing adequate breathing (see CPR).
** Stopping blood loss (see bleeding).
** Immobilizing the pet.
** Protecting obvious fractures from further injury (see splints).
** Preventing loss of body heat by covering the patient with one or more blankets.
** Immediately transporting the patient to a veterinary facility for definitive treatment of shock and other injuries and illnesses (see transport).
Treatment of Shock:
What Not to Do
Well-meaning pet owners often use first aid procedures that may seem helpful, but, in fact, may prove dangerous to the animal.
** Do not allow the injured pet to move about on his own. Walking about or any unnecessary movement (especially allowing the pet to jump in or out of the transport vehicle) may increase internal bleeding. Unnecessary use of muscles "burns fuel," which can be fatal to a patient in shock.
** Do not apply a heating pad to a sick or injured patient. He may suffer a severe burn. In addition, application of heat will cause the vessels of the skin to dilate. These dilated vessels require more blood to fill them and decrease the efficiency of the already failing cardiovascular system, resulting in worsening of the shock condition.
** Do not pour water (or anything else) into the animal's mouth. Animals in shock are weak and may inhale anything given by mouth into the lungs, causing a serious complication.
** Do not administer any medications (including aspirin or other pain relievers) unless instructed to do so by a veterinarian.
** Do not assume the pet is not in shock after an accident. Early, mild stages of shock are difficult to recognize, and the pet may deteriorate rapidly if not treated.
** Do not hesitate seeking veterinary assistance. Many injuries and illnesses that cause shock may cause irreparable damage in minutes. Any hesitation could mean the difference between a pet making a full recovery and a pet that cannot be saved.