Emergency and Critical Care in Small Animal Practice
- 1. ABC’s of Severe Cardiovascular Collapse
- 1.1 A if for Airway
Many efforts at resuscitating a dying animal fail because principles that are known for humans do not apply to animals. Dogs and cats are not that different from their human masters when it comes to CPR Once you know the slight differences as well as the newer thoughts on CPR you should be able to “Jump Start” an animal as easily as a human.
A is for airway indicates that the most important thing that keeps an animal alive is oxygen. Making sure an animal has a clear passage to the trachea and lungs is the first order of business. Many people are intimidated by checking the mouth of a dog because of the obvious danger involved. The normal routine below is followed by a few common sense hints.
If the patient is not breathing through the mouth or not breathing at all, suspect total airway obstruction:
a. Extend the neck, finger sweep the throat
b. Give five or six abdominal thrusts
c. Repeat finger sweep, then thrust again
d. Turn on side, give blows to the back
e. Repeat, but not for too long
f. If still obstructed, perform a tracheotomy
This may seem foreign to those not in the medical field. In general, we would consider this action on an animal which has been hit by a car, poisoned or collapsed from heatstroke, seizures or other catastrophic illness. If the pet is moving around, conscious, making noise (such as whining or crying), then it has an airway and can breathe. If it is lying still as if it can’t move and does resist your opening its mouth, then you can perform the above. actions
Agonal is a term that refers to an animal which is most likely dead but still has some reflex activity. These animals will gasp with their mouth open and neck arched about once every minute. Their eyes will be widely dilated and will not blink when you touch the eyeball. Many animals will be rushed to veterinarian in an agonal state (which can last for some period of time) with the owners thinking the animal is still alive. Many of these animals could have been saved if CPR were performed when discovered by the owner.
- 1.2 B Is For Breathing
Breathing is done in the healthy awake animal about every 2 or three seconds, and in the asleep animal every five or six seconds. Older CPR methods dictated that breaths be given every five seconds. Newer data indicates that a breath every second or every other second is needed to provide enough oxygen to keep the brain from dying. In an animal, these are given by holding the mouth closed and blowing into the nose. It is almost impossible for one person to accomplish CPR on an animal by themselves. One person cannot breathe into an animals nose every second for very long without hyperventilation. A second person must relieve that person frequently. Breathing should alternate with chest compressions as much as possible.
- 1.3 C Is For Cardiac Massage
Cardiac massage is the term to describe an external pumping action that is meant to revive the failed heart. The blood flow to the heart itself is the single most important of the early heart massage. The heart stops beating after the lungs stop breathing. The heart is rarely the first thing to fail.
Circulation to the heart can be accomplished by chest compressions. These compressions have to be given at the same rate that the heart would normally beat. 80 to 120 chest compressions per minute are given in a “cough-like” manner to the widest portion of the chest. These chest compressions cause circulation of blood through the heart as well as through the whole body. The spring of the rib cage acts like a bellows pump. To be effective, the heat and chest of the dog should be placed lower than the rest of the body so that gravity will allow blood to rush to the heart and brain. The movements need to be quickly applied in a manner as to cause a 30% movementof the chest wall. Alternating abdominal compressions (at the rate of 70-90 per minute) will aid greatly in the movement of blood. The counterpressure has been shown to increase survivability. The abdominal compressions just mentioned are a part of this. Another helpful maneuver is to wrap the rear legs and abdomen with ace bandages to force the blood out of less needed areas into the chest and brain. This will effectively double the blood flow.
If the heart is stopped or fibrillating, (ineffective tremors of the heart muscle) it may need to be shocked into pumping again. The heart is felt between the ribs at the spot where the elbow touches the chest. If the heart cannot be felt after the first round of CPR, then give the heart a sharp blow or slap (called a precordial thump in human terms) to try to “jump start” the heart without a defibrillator. This maneuver is very effective at starting normal heart function.
Internal cardiac massage is the most effective form of CPR but it has the complications of potential massive hemorrhage and infection.
- 1.4 D Is For Drugs
Few of you will have the availability or knowledge of the use of any of the CPR drugs. Most must be given I.V. or intratracheally to be effective. The drugs most commonly used in the initial effort are:
- 1. Epinephrine (Adrenaline) 1:1000 –
- 1 cc per 10 lbs I.V.
- 2 cc per 10 lbs intratracheal
- 2 cc per 10 lbs intra-tongue
- DO NOT INJECT INTO HEART
- 2. Atropine –
- Dog – .5 cc per 10 lbs I.V.
- Cat – .25 cc per cat
3. Lidocaine –
- Dog – .5 cc per 10 lbs.
- Cat – .05 cc per cat
- Cortef – 20 mg/kg I.V.
5. I.V. Hypertonic Saline 7.5% –
- Dogs 4-5 ml per Kg I.V.
- Cats 2 ml per Kg I.V.
5. HESPAN (Hetastarch) –
- 14-20 ml per Kg I.V..
- 1.5 E Is For Evaluate Status
Evaluation of the patient is the next order. Monitor and transport are the orders. Many hearts will be able to be “jump started” but be aware that the conditins that caused it to stop in the first place are still present. I have started many failed hearts and had just the time to congratulate myself and my coworkers before it stopped again. Close monitoring of breathing and heart function are imperative.
Monitor the heart and pulse – the heart is felt under the tongue in an easily tractable pet or on the inside of the rear flank on any pet.
Monitor Consciousness – The eye can be touched in an unconscious animal. If the eye is touched and the eye blinks, then the animal is most likely conscious. If the outside of the eye is touched and the animal blinks then the animal is even more awake. These are good signs. Pupils are a good indicator of brain function. Maximally dilated pupils are bad. They appear in brain death and look as if the pet has no iris or colored part to the eyes. Pinpoint pupils usually mean pain or pressure in the brain. Unequal pupils mean that a serious concussion has happened.
Monitor the gum – The capillary refill time is the best way to monitor cardiovascular function. If the gums are pink and the color returns within 1 second after they are touched, then we have almost normal blood flow. Shock or poor circulation will give us white gum tissue. Pain or illness will give us injected gum tissue so the individual blood vessels stand out more than the uniform color. Blue gums usually mean lack of oxygen, not lack of circulation. Brick red gums indicate that the circulation is congested. Any gum color can be present in a dead animal.
- 2. Shock
- 2.1 What Is Shock?
Shock is a term that is commonly used to denote a state of serious derangement. Shock actually is a term that means poor circulation of the blood. The blood circulation is what brings oxygen to the cells of the body. Without oxygen the cells start to die. This cell death starts very quickly in some organs and will actually cause the shock to worsen.
The blood is circulated in arteries to the tissues and in veins away from tissues. At any point in time the animal is using only a small number of the blood vessels that are present. These blood vessels are not always needed but serve as reserve for increased need or exertion.
Shock can occur in many ways. Hypovolemic (blood loss), Neurogenic (caused by the brain), or Cardiogenic (caused by the heart).
Blood loss causes shock by reducing the amount of blood that can be circulated to the body tissues, muscle cells, brain, etc. The body has systems that will shunt the blood flow to the more vital areas of the body (heart, brain) and away from less vital areas such as the skin or gut. During this process less vital tissues start to die and scream for oxygen. This causes the extra blood cells in the body to open up. The remaining blood cannot fill these blood vessels and just pools in them. Unless the blood vessels are full, blood pressure can’t develop and the blood will not circulate. This lack of circulation is shock. It is analogous to Houston’s water supply to homes. As long as there is good water pressure, every home that needs water gets water. But when there is going to be a freeze and everyone turns their water on to keep the pipes from freezing the pressure falls. This causes less water to flow to each house. If all the faucets in Houston were turned on, it would be impossible for the main pumping station to deliver water to any homes.
The brain can cause shock in severe situations – it is startled by some event that convinces it that a signal to open up all the blood vessels in the body is a correct action. This causes poor circulation even though the heart is normal and blood volume is normal. This might occur with a severe scare or electrical shock or head trauma.
Failure of the heart to pump is a reason for poor circulation and poor delivery of oxygen to the tissues. This eventually leads to increased demand and opening of the blood vessels and even less circulation. This is cardiogenic shock.
Infections, cancer, toxins, drowning, cold, heat, can all lead to poor circulation in one way or another, leading to shock.
- 2.2 How Do We Treat Shock?
Shock is usually present in dogs that have been hit by a car. The best way to determine if shock is present is to check the gum color and capillary refill time. The gum color in a normal dog is coral pink. A painful dog will have pink gums that are injected (blood vessels are prominent). A pet in shock will have white or very pale gums. The capillary refill time is a measure of the circulation in the body. The capillaries are very small vessels that are responsible for the color of the gums. The capillaries are not considered essential in times of emergency. If blood is not flowing to the capillaries, the gums will be pale or white. If blood is not flowing to the capillaries then blood is not flowing to the other organs of the body and we are in shock. The capillary refill time is the amount of time for the color to come back after touching the gums to blanch them. The normal is 1 second or less. A CRT of three seconds or more is serious.
Shock is poor delivery of oxygen to the tissues. This is usually due to poor circulation of blood or lack of blood to circulate. This oxygen need by the tissues can be met by filling the blood vessels with fluid so that circulation can happen. The amount of oxygen delivered to the tissues can be increased by giving the pet oxygen which is the first thing done in the animal hospital but is rarely available at the patients home. (If oxygen is available, do not try to put an oxygen mask on a pet in shock – place a clear plastic bag over the head of the pet and pass the oxygen hose through a corner of the bag.) Circulation is restored in the hospital by giving large amounts of I.V. fluids as fast as possible through multiple I.V. catheters if needed. As an emergency procedure, shock can be treated effectively by wrapping the extremities and abdomen with Ace bandages to force the blood into the more vital areas of the body.