Anesthesia & Patient Monitoring

Proper anesthesia begins with knowing your patient, their history and their current medical and surgical needs. Gathering this information allows us to select the best anesthesia protocols and drugs and which drugs may not be suited for the patient or the procedure.

It’s an unavoidable reality of pet ownership for most of us: at some point, your pet will need a procedure that requires they be anesthetized. Dental procedures, some imaging procedures, and nearly all surgical procedures require that pets be “put under” for anywhere from a few minutes to several hours. These veterinary procedures require precision that would not be possible with a stressed animal that isn’t anesthetized. Thankfully, modern anesthetic techniques and advanced anesthetic drugs have made going under anesthesia less strenuous and less dangerous than ever before. (Learn more)

  • The Use of Modern Anesthetics in Veterinary Medicine
  • Pre-Anesthetic Testing & Your Pet
  • How Safe is Anesthesia for my Senior Pet?

Modern anesthetic drugs and anesthesia techniques have made going under anesthetic safer and less complicated than it has ever been before. Animals under an anesthetic for various procedures are monitored continuously by trained technicians and their anesthetic level is kept at the minimum possible to keep them still and unconscious without pushing them into deeper anesthetic states than necessary.

These days, a short-acting IV anesthetic is typically administered to gently put the animal under prior to Inserting a breathing tube. This breathing tube is attached to an anesthesia machine, dispersing an inhalant agent (isoflurane) that keeps the animal under a steady state of anesthesia. Modern inhalant anesthetics are considerably gentler on an animals’ organ systems and so safe that we do not hesitate to anesthetize any pet that needs to have a procedure done. Below is just some of the drugs we use for anesthetic procedures.

Anesthetic Agents

Anesthetic agent can be classified in three categories:

LOCAL ANESTHETICS – These drugs are injected into the body to create a desensitized area of the skin, or sections of a limb. Although very commonly used in human medicine, many of our pets will not cooperate and physically holding them still might be more dangerous to them than using a general anesthetic. So local anesthesia is used mainly for small growth removals on areas of the body where the pet will tolerate manipulations awake. Examples of local anesthetics are Lidocaine and Carbocaine.

INJECTABLE ANESTHETICS  These drugs are usually used for either very short procedures, or they may be used to “induce” anesthesia and are then followed by introduction of a gas anesthetic agent to continue the anesthetic procedure.  There are several drugs and drug combinations that are extremely safe that will provide sedation and analgesia prior to anesthetic induction with Propofol that will allow endotracheal intubation.

Propofol – this is the state-of-the-art injectable drug for humans. It is our most commonly used injectable anesthetic, since it does not depend on the liver or the kidneys for its elimination. Propofol can provide complete anesthesia and additional doses are not additive, meaning that your pet will be awake within minutes of the final dose.

Dexdomitor – this is a very unique drug. It will cause profound sleepiness and muscle relaxation. It is most commonly used for very short procedures. It is ideal, for example, for use in radiology where proper positioning is not possible in the awake pet. The great thing about this drug, is that we can inject a second drug called Antisedan that will completely reverse the Dexdomitor. This enables us to send your pet home within minutes of the procedure.

GAS ANESTHETICS – For procedures longer than several minutes, gas anesthetics are the safest way to go.  In humans and in our pets, gas anesthetics are delivered with a special anesthetic machine. Anesthetic machines basically are a source of oxygen and a mechanism for vaporizing a special agent that causes anesthesia when breathed into the lungs. Isoflurane is the most commonly used gas anesthetic in veterinary medicine.  It is safe and effective in almost any pet.  Once the anesthetic is turned off,  your pet will awaken within minutes.  Gas anesthetics are administered through tubing that is then connected to an endotracheal tube which is placed into your pet’s windpipe. With this setup, it is possible for us to have complete control over your pet’s breathing, which is essential for absolute safety.  Being in complete control allows us to administer the exact amount of anesthetic that your pet needs, providing us with the safest form of anesthetic possible.

Every patient undergoing any length of anesthesia should have an intravenous (IV) catheter placed prior to anesthesia. This provides direct and rapid access to the patient’s venous system for drug administration in case of emergency.

Anesthetic Monitoring

No anesthetic protocol is safe without the right monitoring equipment and trained technicians to watch over your pet’s anesthetic protocol.  There are many different types of monitors.  Let’s look at a few of them:

  1. Respiratory Monitors – No system is more important to monitor than your pet’s respirations. There are multiple ways to monitor respiration. The easiest way is to visually observe chest movements.  This, however, is not adequate in many cases, so we have two electronic monitors that help us. We have an Apalert Monitor that makes an audible beep with each breath and displays to us the number of seconds between each breath. An alarm is always set to tell us if too many seconds go by without a breath. We also use an Electronic Volume Sensor that displays how big your pet’s breath is.  Once again, there is an alarm that can be set to any volume of air that we choose. When your pet is under gas anesthesia, we also visually watch the bag or the bellows that moves with each breath.
  2. Electrocardiograph Monitor – We always monitor the electrical activity of the heart. This is critical with anesthesia, since electrical disturbances or arrhythmias can be picked up easily and treated if necessary. These monitors also constantly display the heart rate and make audible beeps with each beat.  This makes it easy to monitor your pet, both by sound and electrical wave patterns.
  3. Pulse Oximetry – A Pulse Oximeter measures the percentage of hemoglobin that is saturated with oxygen. OK, in English, that means that it monitors how well the Red Blood Cells are being Oxygenated by the lungs and pumped by the heart. This is a very sensitive instrument and can alert us to any combination of poor respiration or poor circulation. Once again, we have both audible and visual output.
  4. Blood Pressure – Blood pressures are routinely done in humans to monitor depth of anesthesia. This is an essential monitoring technique in pets as well. Blood pressure can be monitored by a simple cuff that is placed either on a leg or a tail.  Fluids are given through an IV catheter to maintain blood pressure (as discussed above) and to keep the animal hydrated during surgery.
  5. Temperature – Core body temperature is reduced by anesthesia. This is especially true in long procedures and with smaller patients. We have a heated surgical table as well as a fluid warmer.  Temperature can be taken with just a thermometer; However, we use an esophageal stethoscope for a continuous reading of temperature. This way trends can be monitored, and warmth added even if there is a drop in temperature by 0.1 degrees.  It is much easier and more beneficial to the patient to prevent a drop in temperature, rather than to try and warm them up after a drop has occurred. To this end, attention to temperature starts when the patient has their premedication prior to putting them under anesthesia. Effective strategies include warm fluid bags in their kennel whilst their sedative and analgesic combination takes effect, and then a constant source of heat during the procedure. A ‘Bair Hugger’ Warming Blanket’ is used at all times throughout the procedure and during post-surgical recovery

Preanesthetic Testing and Your Pet

What to know before your pet goes under Anesthesia

Regular checkups and blood work for your pet is important. Whether your dog or cat is old or young, healthy or sick, fat or skinny, small or tall, regular checkups and blood work allow your veterinarian to do a thorough job to keep your pet healthy. When your veterinarian is able to establish a baseline laboratory values for your pet – what’s normal in your pet when he or she is healthy – it’s easier for your veterinarian to give your pet great care. With a thorough medical history, your veterinarian can detect subtle changes in your pet’s health and will be able to catch and treat illnesses early when it they are most treatable. Preanesthetic testing Performing blood work and establishing baselines are beneficial to your pet in other ways, too. When your pet needs surgery, your veterinarian will always perform a physical exam, but you’ll also have the option to have preanesthetic blood work done to ensure your furry friend is healthy enough to undergo anesthesia and surgery. You never know – your otherwise healthy pup may have an unknown condition that prevents his blood from clotting, or a heart issue, or some other disorder that increase the risk of complications from anesthesia and surgery. There’s a lot involved when your dog or cat is set to undergo anesthesia.

Preanesthetic testing is done for a few major reasons:

  • Detect hidden illnesses that may put your pet at risk during  anesthesia and surgery
  • Reduce risk by adjusting the approach to anesthesia and surgery
  • Peace of mind – when it comes to your pet’s life, preanesthetic testing can be very reassuring

It’s likely that preanesthetic testing will cost you a little extra, but it can save your pet’s life and reduce the risk of anesthetic and surgical complications. In the end, it’s all about safety, peace of mind and ensuring the future health of your pet.

What to Expect

Most pets will receive anesthesia at least once in their lifetimes. Many pets undergo anesthesia early in life as part of spaying and neutering procedures. Preanesthetic testing differs based on the age and breed of your pet. You veterinarian will screen for conditions specific to certain breeds or to pets at certain life stages. 

So, what exactly is your veterinarian looking for during preanesthetic testing? Here are some common diagnostic tests performed prior to administering anesthesia:

  • Chemistry tests to evaluate kidney, liver, and pancreatic function and ability to normally recover from anesthetic agents
  • A complete blood count (CBC) to rule out blood-related conditions such as anemia, clotting problems, inability to fight infection, and more
  • Electrolyte tests to ensure your pet isn’t dehydrated or suffering from an electrolyte imbalance
  • Urinalysis to screen for urinary tract infections and other diseases, and to evaluate the kidney’s ability to concentrate urine and filter anesthetic agents from the bloodstream

Additional tests, such as an ECG, may be added on an individual basis, and your veterinarian will recommend the right thing for your best friend.

How Safe is Anesthesia in My Senior Dog?

Dr. Phil Zeltzman, DVM, DACVS, CVJ
Dog Surgery A-Z
Kelly Serfas, a Certified Veterinary Technician in Bethlehem, PA, contributed to this article.

Pet parents often worry that their dog is too old for anesthesia. This is a huge misconception that prevents many dogs from getting the surgery they need. As we often say, “age is not a disease.” That said, we do not take anesthesia lightly in patients of any age, and certain precautions should be taken for senior dogs. Here are 7 facts that may help you feel more secure when your senior needs anesthesia:

  1. A workup makes anesthesia safer. A thorough physical exam should be performed on every patient prior to anesthesia. In addition, what is called a “full workup” helps vets understand the “overall picture.” This includes blood work and a urinalysis. Such tests will show any changes in the function of organs, such as the liver or the kidneys. Chest X-rays may be recommended. They will show the size of the heart and if there are any masses or concerning changes in the lungs.
  2. Your vet will consider all conditions before beginning anesthesia. Blood work abnormalities, diabetes, thyroid disease, high or low blood pressure, Cushing’s disease, heart disease and other conditions should be controlled prior to anesthesia, if at all possible. This may not be possible in all cases, for example in the case of a life-threatening emergency. But in most cases, when vets have the luxury of time, we can correct abnormalities to make the anesthesia smoother. For example, if your dog has a low red blood cell count, finding the cause and blood transfusion, prior to anesthesia and surgery, may be important. Deciding when the time is right to perform anesthesia is part of the art of veterinary medicine. In order to know how well the heart is functioning, an EKG can be performed.
  3. Anesthesia dosing is carefully selected. There is no “one size fits all” anesthesia dosage. Anesthesia drugs are chosen and calculated based on body weight, health issues, breed, temperament and even anticipated length of anesthesia and pain involved with the surgery. We now have the luxury of choosing from multiple anesthesia drugs, depending on the pet’s particular needs.
  4. Veterinarians know there is no routine anesthesia. “There are routine surgeries, but there is no routine anesthesia.” What does this common quote, invented by an anesthesiologist, mean? Some surgeries are so common, that they become fairly predictable. However, with anesthesia, you are always at the mercy of an unpredictable complication. Fortunately, a good surgery and anesthesia team can anticipate and correct complications. Most complications are minor and easy to correct.
  5. Monitoring will help protect your dog during anesthesia. Proper monitoring is an essential part of anesthesia. Monitoring includes keeping a close eye on breathing, heart rate, temperature, EKG, and oxygen level. Ideally it will also include watching blood pressure and CO2 levels. Small changes can be seen right away. They help the doctor or nurse adjust the anesthesia to keep your dog in safe ranges. Some dogs may require additional monitoring such as diabetics, who should have their blood sugar level checked throughout the procedure.
  6. Monitoring recovery will help keep your dog stay safe after anesthesia. Most clients are not aware that the recovery period is actually riskier than the anesthesia period itself. More dogs get in trouble after they wake up, then when they are under anesthesia. Monitoring, and encouraging dogs to wake up smoothly will still involve the surgery and anesthesia team. Make sure that your dog will continue to be supervised after waking up from anesthesia.
  7. Fatal complications from anesthesia are very rare.  According to a study posted by the National Center for Biotechnology Information (NCBI), the average death rate under anesthesia is around 0.2%. Said otherwise, an average of 99.8% of pets, regardless of their age or health status, survive anesthesia. Overall, dogs do great under anesthesia, regardless of their age or health status. Remember, we put dogs under anesthesia for good reasons: perhaps cleaning teeth, removing a tumor, or correcting laryngeal paralysis. As I always say, “anesthesia is not the enemy, the disease is the enemy.” If you have any questions or concerns, you should always visit or call your veterinarian – they are your best resource to ensure the health and well-being of your pets.

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