Anesthesia

 

One of the most important tools available to veterinarians to thoroughly and painlessly treat pets is the advent of modern day anesthetics. These anesthetic agents allow us to sedate and anesthetize a wide variety of animals with negligible chance of serious side effects.

The lack of significant complications from anesthesia is due to a combination of expertise, thorough pre-anesthetic testing, and state of the art anesthetic and monitoring equipment. We are equipped to anesthetize any pet from a finch that weighs 15 grams (it takes 454 grams to make up one pound), to pets that weigh several hundred pounds. We are also particularly proficient in anesthetizing older (geriatric) pets and pets with medical problems like liver and kidney disease.

The goals of anesthesia are to minimize anxiety and eliminate pain. In addition, from the surgical point of view, anesthesia allows profound muscle relaxation. This is helpful in every surgery because the procedure will go quicker and incisions can be made smaller when the muscles are relaxed. In certain types of surgery like fracture repair, this muscle relaxation is crucial for success.

It is normal for you to have concern if your pet is about to undergo a procedure that requires anesthesia. Because of this fact, we invite you to be a part of our anesthetic team. Your primary responsibility is to let us know of your concern. You will have access to your doctor to discuss any of your concerns and to set up a custom protocol for your pet, taking its specific needs into consideration. Only when you are comfortable with the situation will we proceed any further. Also, to alleviate your concern on the day of actual anesthesia, we will call you immediately after your pet wakes up, if you so desire. Please leave a number where we can reach you on the day of surgery.

We have a short video on monitoring pets during anesthesia. You will need QuickTIme from www.apple.com to be able to view it.

Precautions

One of the best precautions we take to minimize the risk of anesthesia it to perform pre-anesthetic diagnostic tests. A pet can pass its pre anesthetic physical exam and still have significant internal problems, so it is important that we perform more than just a physical exam. This is because animals cannot tell us of their problems, have high pain thresholds in comparison to people, and have defensive mechanisms allowing them to hide symptoms. Pre-anesthetic diagnostic tests are designed to alert us to internal problems that are occurring without any symptoms.

Those pets that have infections (especially tooth infections) are put on antibiotics ahead of time. They make pets feel better, and help support internal organs.

Older pets or those with medical problems are given intravenous (IV) fluids prior to and during the anesthetic procedure. Giving fluids prior to the surgery greatly reduces anesthetic risk. This is particularly important in older pets and those with kidney or liver disease. Most pets that have significant dental disease will also be given IV fluids.


Injectable Anesthesia

Injectable anesthetics are used for many purposes. One of their primary uses is to sedate pets before giving the actual anesthesia (called pre-anesthetic). By sedating ahead of time we dramatically minimize anxiety, cause a smoother recovery, and minimize how much anesthetic we need to administer during the actual procedure. In addition, some injectable anesthetics minimize vomiting, a common problem when waking up from anesthetic.

Little Bit is receiving an intravenous injection of an anesthetic before his teeth cleaning. It is being given through an I.V. catheter in the cephalic vein of the forearm.

Injectable anesthetics are also used to give complete anesthesia for short periods of time. This is used for C-sections and minor surgical procedures. Injectable anesthetics are ideal to sedate a pet for radiographs (x-rays).

As new anesthetic agents evolve, the trend is towards using injectable anesthetics more and more for complete surgical anesthesia. They are very effective, very safe, and allow for rapid recovery from anesthesia. They also protect the environment because there are no anesthetic gases vented into the atmosphere.

The primary anesthetic in this category is called Propofol. It induces anesthesia rapidly, and pets wake up almost immediately.

Gas Anesthesia

The mainstay for general anesthesia is gas anesthesia because it is very safe and highly controllable. We use the safest and most effective gas anesthesia available, called Isoflurane. It is so safe it can be used in creatures as small as tiny birds.

Gas anesthesia requires specialized equipment and training. Several precision components are used to administer and monitor anesthesia:

Oxygen

All pets put under gas anesthesia are given 100% oxygen from the moment they are anesthetized until they wake up, dramatically increasing the safety of the procedure.

We have a special machine in surgery that generates 100% oxygen

As a backup,  oxygen is stored in large tanks under high pressure. The oxygen in the tanks is delivered to the anesthetic machine via special piping throughout the hospital. This allows us to have anesthetic machines in several hospital locations. A pet can be brought into radiology after its surgery and still be kept under gas anesthesia while the surgeon reviews post operative radiographs to ensure everything is in order. This is especially helpful when orthopedic surgery is performed.

Endotracheal Tube

With rare exceptions, oxygen is delivered to your pet by a breathing tube (endotracheal tube) in its windpipe. It is the preferred method to administer oxygen because it is very efficient, will prevent any vomitus from entering the trachea (vomiting rarely happens because of fasting and pre-anesthetic sedation), and allows us to gently inflate the lungs during surgery so that work at maximum efficiency. Besides oxygen, the anesthetic gas (Isoflurane) is also administered through the endotracheal tube. Medications can even be administered via this special tube.

After Little Bit was given an injectable anesthetic a breathing tube was placed in his windpipe and Isoflurane was administered.

We can easily inflate your pet’s lungs by gently squeezing the bag connected to the tube and monitoring the amount of pressure we are exerting with a gauge on the anesthetic machine. Each size and species of pet requires a different sized endotracheal tube. The tube is not removed from your pet until it is literally waking up. This ensures that the swallowing reflex is present and your pet is now safely able to breathe on its own.

This x-ray shows the breathing tube (follow the arrow) as it passes over the tongue and down the trachea (windpipe).

"Chase Summerville" 2/2/98

Vaporizer

An instrument called a precision vaporizer is used to deliver the anesthetic gas within the oxygen. It is a very precise instrument allowing us to make fine adjustments in anesthetic level. Without this vaporizer we would not have the wide safety margin that we currently enjoy.

For most surgeries we administer the anesthetic at a setting of 1-2 %. This small percent of anesthetic, added to the oxygen the pet is breathing, is all that is needed to achieve complete surgical anesthesia. Before the surgical procedure is finished the anesthetic is lowered before it is turned off completely. As the surgeon is finishing the procedure your pet is in the beginning stages of waking up. This is another way we minimize anesthetic risk.

Monitoring

During the procedure your pet will be monitored in several ways. One of the best monitors is the surgeon because he is literally visualizing the blood in the circulatory system. Any change in the blood is readily noticed because pets that are breathing 100% oxygen should have bright red blood.

Also, we have an anesthetist nurse in the room monitoring anesthesia. She monitors oxygen flow and anesthetic settings on the precision vaporizer, along with heart rate and respiratory rate. She also uses several tools to aid her in keeping a close watch on important anesthetic parameters:

 

Anesthetic Monitor

This highly accurate and sensitive monitor gives us detailed information on your pets physiologic status while under anesthesia.

It is calibrated prior to surgery to ensure accuracy

Esophageal Stethoscope

Our anesthetist technician can also use an esophageal stethoscope to listen to the heart. This sensitive instrument is passed into your pet’s esophagus while under anesthesia and placed right at the level of the heart, thus greatly enhancing our ability to hear the heart and detect any problems.

Pulse Oximeter

The portable pulse oximeter is an instrument that measures the oxygen saturation of you pet’s red blood cells (to be more specific, its hemoglobin). It is an extremely sensitive instrument that gives us an indication of problems that may be arising long before your pet suffers any ill effects. In addition to measuring oxygen saturation, it measures heart rate, pulse character, and respiration.

This instrument does its magic by measuring the hemoglobin that is oxygenated and comparing it to the hemoglobin that is not oxygenated. It does this by shining a light on an artery, and then measures how much of this light is absorbed. It gives us an answer in PaO2- the partial atmospheric pressure of oxygen

This pulse oximeter shows a pet with an oxygen saturation of 94%, a heart rate of 157. It is breathing 27 times per minute, and its heart rate is steady.

This is Little Bit having his teeth cleaned under general anesthesia. The pulse oximeter is attached to his rear leg.

The pulse oximeter has several different types of sensors that can be attached in various locations depending on the procedure being performed.The pulse oximeter can also be used on pets that are not anesthetized. It is useful for pets that are having difficulty breathing (dyspnea) from many different causes. It is also used to monitor pets that are in a state of shock. One of the most common reasons for pets to be presented to us in a state of shock is from trauma, especially being hit by a car (HBC).

The esophageal stethoscope and the pulse oximeter can be used simultaneously. In this dog, undergoing a neuter operation, Denise, our nurse anesthetist, is taking a reading with both instruments.

The blue tube on the anesthetic machine suctions exhaled gases from our patient and vents them outside the building. The white particles in the canister absorb exhaled carbon dioxide, and the round gauge measures the pressure at which oxygen is being introduced into the endotracheal tube when the technician inflates the bag.

Techa 1

We have a short Quicktime movie showing a pulse oximeter in action on one of our volunteers. The top number is the oxygen saturation, the bottom number is the heart rate. The vertical bar gives us a clue as to the strength of the heart beat. Click on the link below.

Pulse Oximeter

Capillary Refill Time

To complement these high tech methods of monitoring, our anesthetist technician uses several hands-on techniques as a backup. One of the easiest of these is called capillary refill time (CRT). By pressing on the mucous membranes in the mouth, and noting how long it takes for the blanched area to turn pink again, we get a basic assessment of your pets cardiovascular status. A normal pet’s pink color returns within 2 seconds. This technique is used in other situations besides anesthetic monitoring. It is especially helpful when a pet is in shock or is dehydrated.

Blood Pressure Monitor

We also monitor the blood pressure when pets are under anesthesia for the longer surgical procedures. This is done with our anesthetic monitor. Our hypertension page has a video of the doppler blood pressure monitor in action when we use it in an exam room.

Pain Medication

We complete the anesthetic process by giving your pet a pain injection before it wakes up from the anesthetic. Since the gas anesthesia has a small amount of residual analgesia (ability to kill pain), the pain shot kicks in as the gas anesthetic is wearing off. This allows for a very smooth and pain free recovery. Those of us that have had even minor surgery know how important pain medication is after a procedure. This pain injection will keep your pet calm its first night home from any surgery.

Local Anesthesia

Another excellent way to prevent the pain encountered when your pet first wakes up is to use a long acting local anesthetic at the incision site. We administer it prior to completion of the surgery, and its affects last for 6 hours.

We use the long acting version of this drug which eliminates pain for up to 8 hours.

We even have a local anesthesia patch that is used in some cases to bring long term relief for several days if needed.

Pain Patch

We also use Duragesic patches for general pain control in the more serious cases. It is preferable to apply it 12 hours before the surgery for maximum effect postoperatively. It provides pain relief for 3 days. It is important to make sure that no children or other pets are allowed to contact the patch in any way. Bring your pet back to us for proper removal and disposal.

The patch is applied in different locations depending on the surgery. Wrapped around one of the legs and between the shoulder blades are common locations. One of our nurses is applying it in this picture using gloves to ensure she does not come into contact with the active ingredient.

If we put it on the leg it is covered with a bandage. We will commonly staple the patch to the skin if we put it between the shoulder blades. It will be bandaged for protection and to minimize the chance of contact with other pets and children. Please return in 3 days for us to remove it and dispose of it properly.

To ensure your pets complete safety, it will stay with us for at least several hours after it is awake. We will verify the pain medication is working and there are no ill effects from the anesthetic administered. It will also allow your pet to completely wake up and walk normally in a controlled environment where it cannot hurt itself. Our technical staff monitors your pet post operatively until we are certain it is ready to go home.

Long term pain control at home is also important during the next several days. We will routinely send you home with an anti-inflammatory medication or pain suspension for long term pain control. The two most common medications we use are Rimadyl and Torbutrol suspension.

Laser Surgery

Even though it is not an actual pain medication, using our carbon dioxide laser when indicated during a surgical procedure dramatically minimizes pain because it decreases inflammation, swelling, and cauterizes nerve endings. By using the laser and stopping the pain cascade before it even begins there is a dramatic influence on decreasing post operative pain.

Returning Home after anesthesia

When you bring your pet home after anesthesia it is helpful to follow some common sense suggestions:

Keep contact with other pets and children to a minimum for at least the first 12 hours. Confine it to an area where it cannot hurt itself  because it may not be steady on its feet for up to 24 hours. It might be groggy the first night due to the pain injection it was given.

Use pain medication as prescribed and keep your pet in a warm and quiet area. You can spend time giving unlimited TLC

Even though your pet has probably been fasted for the anesthesia, feed it only a small amount of food and water when first returning home. Give it more later if it eats well and does not vomit (emesis). Most pets return to a normal appetite within 24 hours. If your pet has not fully recovered from the anesthetic by the next day then please call our office.

Please call us in the evening if you have any questions when your pet returns home from surgery or any anesthetic procedure.