Anesthesia- What you should know

Anesthesia:
What You Should Know Before a Procedure
By Dr. Karen Burgess

 Anesthesia is an artificially created state of insensitivity typically created by drugs or inhalant gas that depress the nervous system.  General anesthesia creates a state of unconsciousness allowing for muscle relaxation and complete lack of sensation.  Local anesthesia is typically where a small area is numbed allowing for less invasive procedures while a pet is awake.   For pet owners anesthesia is a situation that often evokes a feeling of fear or anxiety.  Estimates indicate that only 1 out of 100,000 will have a reaction of some sort to anesthesia.  While this number is small, understanding the process of anesthesia and the steps that are taken to minimize the associated risks helps to alleviate these concerns.

Trusted and trained professional team
The most important element behind a safe and successful anesthetic procedure is the team working with your pet.  Having a relationship with your veterinarian and their staff, knowing that they practice up to date medical management, and understanding that their attention is dedicated exclusively to your pet while it is under general anesthesia is essential.  As a pet owner you should feel that your concerns have been addressed prior to any anesthetized procedure and that there is an open line of communication between the veterinary team and yourself.  Talk to your veterinarian about how they develop their protocols, what specific considerations there may be for your pet, and what additional training in anesthesia/pain management they have had.  It is also important to know that all “veterinary technicians” are not the same.  The title may be a certified (academically trained) technician, a degreed Animal Science major, or simply someone that was hired yesterday with no formal training.  A typical anesthetic procedure at Healthy Paws Animal Hospital involves at a minimum a dedicated certified technician/degreed major and the doctor.  The pet under anesthesia is the primary focus of all involved.

Physical examination, complete history, signed consent

  • The physical exam allows the doctor to evaluate for any issues that may impact the anesthetic episode or procedure.  This should occur immediately prior to general anesthesia to ensure accuracy.  Historical questions asked at admission allow a dialogue with the pet owner looking for any additional issues or concerns.  Previous medical problems, current medications, and recent ingestion of food are only a few of the necessary details.  An anesthesia consent form should also be completed allowing the client to understand and acknowledge that the details of the procedure, potential risks, and financial commitment are understood and agreed to by all.

Pre-anesthetic laboratory testing

  • Testing of the blood and at times urine allows a more detailed evaluation of a pet’s internal organs.  Dehydration, kidney, liver, and electrolyte abnormalities can all negatively impact an anesthetic episode.  Laboratory testing may be done the day of a procedure or within the several weeks prior.  While test results should be normal, any abnormalities may cause a procedure to be postponed until addressed further.  In some cases radiographs (x-rays) of the heart may also be recommended as an added precaution.

Intravenous Catheter

  • An intravenous catheter allows direct access to a pet’s vein and thus immediate access for necessary treatments.  Typical uses for an IV catheter include administration of additional sedation, pain medication, antibiotics, or fluids.  When pets are under general anesthesia maintenance of blood pressure is of utmost importance.  The ability to administer large volumes of fluid quickly is essential if blood pressure problems arise.  It has been shown that 1-2% of pets NOT receiving fluids during a procedure will develop kidney problems within two weeks of anesthesia.  This risk is nearly zero in animals that DO receive fluids.  In times of low blood pressure or an anesthetic crisis it can be very difficult to place an IV catheter thus the need for placement when the pet is still awake.

Appropriate sedation

  • Pre-emptive/intraoperative pain management, inhalant anesthesia via an endotracheal tube
  • Animals should be maintained under anesthesia via a tube placed in the mouth and down the windpipe thus allowing direct access to the lungs.  An endotracheal tube allows tighter control of the depth of anesthesia and if respiratory problems develop the ability to administer oxygen and artificial respirations.  This tube also seals the airway preventing any unintentional leakage of fluid from the esophagus into the airway.  The gas administered via the tube is typically isoflurane mixed with oxygen and is very short acting.  Thus when you turn the gas off, animals should wake up within minutes.  Prior to intubation with an endotracheal tube, pets should be sedated with drugs that provide both anxiety and preemptive pain relief.  Following sedation, an induction agent is given intravenously putting them in a sleep state and thus allowing the tube to be placed.  It is common for five or six different drugs to be given prior to gas anesthesia with the goal being to create as smooth and safe an anesthetic episode as possible.  By using very small amounts of many drugs (“cocktails”) better overall control can be achieved.  Providing pain control prior to painful stimulation better controls pet’s comfort throughout the procedure.  Additional pain management in the form of local nerve blocks or injectable drugs during the procedure continue the pain control process.

Continual monitoring

  • There are many ways to evaluate depth of anesthesia.  Ultimately we want to administer enough gas to keep the pet asleep but not so much as to be dangerous.  Complications from anesthesia are most commonly related to a pet becoming “too deep”.  With appropriate monitoring, this should be almost completely avoidable.  The following are recommended for the safest episode possible:
  • Licensed technician-human observation is the absolute most important monitor available.  The veterinary technician is constantly monitoring the level of anesthesia and altering the amount of anesthesia being given accordingly.
  • End tidal CO2-measurement of respiratory rate and carbon dioxide levels as the breath leaves the lungs is one of the earliest indicators of poor oxygenation.
  • Blood pressure-low pressures can impact blood flow to sensitive organs (brain, kidneys).
  • Pulse oximetry-indirect evaluation of the oxygen being carried by blood cells and the heart rate.
  • EKG-visual  image of heart beat and electrical waves
  • Temperature control-the body temperature tends to fall with anesthesia leading to potentially life-threatening complications   It is imperative that a pet’s body temperature be monitored and controlled until they are completely awake and normalized.

Recovery management/postoperative pain management

  • Once a pet is awake the job is not done.  Continued monitoring to ensure return to normal body temperature, comfort, and safety are necessary.  Observation should continue until all parameters are normal and the pet is perhaps drowsy but able to move safely on its own.  Comprehensive discharge instructions and discussion with the pet owner to relay expectations after discharge and resources if problems arrive should also be provided.