December 01, 2020
‘There are only safe anesthetists’
In human medicine, some anesthesiologists can go an entire career without having a patient die. In contrast, for a variety of reasons, veterinarians and veterinary technicians who anesthetize cats and dogs on a regular basis see higher mortality rates than their human counterparts.
Perhaps one of the most famous quotes in medicine is from Robert Smith, MD, who said: “There are no safe anesthetic agents, there are no safe anesthetic procedures. There are only safe anesthetists.”
Speakers at the AVMA Virtual Convention 2020 in August discussed issues with anesthesia in cats and dogs—and ways to improve safety, such as through better monitoring and the use of checklists. In addition, speakers at the American Animal Hospital Association’s Connexity 2020 conference in October covered the AAHA anesthesia guidelines, which were updated earlier this year.
Decreasing the odds of death
Dr. Anderson F. da Cunha, a professor of anesthesiology at Midwestern University College of Veterinary Medicine in Glendale, Arizona, spoke at the AVMA Virtual Convention 2020 on “How to Reduce Anesthesia-Related Morbidity and Mortality.”
He said: “Anesthesia mortality can always be lower. It can be zero, and that would be ideal. But is that achievable?”
A 2008 study in the journal Veterinary Anaesthesia and Analgesia examined the risk of anesthetic- or sedation-related death in almost 100,000 dogs and 80,000 cats between June 2002 and June 2004 in the United Kingdom. The risk of death was 1 in 1,849 for healthy dogs and 1 in 75 for sick dogs. The risk of death was 1 in 895 for healthy cats and 1 in 71 for sick cats.
A 2017 JAVMA study examined the risk of anesthetic-related death in about 1.3 million dogs and 275,000 cats anesthetized between January 2010 and March 2013 at Banfield Pet Hospitals, which have similar anesthetic protocols for every hospital. The risk of death for dogs was about 1 in 2,000 anesthesia episodes, and the risk of death for cats was about 1 in 900 anesthesia episodes.
In human medicine, Dr. da Cunha said, the risk of anesthetic-related death is about 1 in 100,000 to 1 in 250,000 anesthesia episodes.
What is the difference? Training. Veterinary professionals treat more than one species, each with its own unique anatomy and physiology, so they need to have broad medical knowledge and adjust as needed. They also have fewer pieces of equipment and less money to spend.
Among the factors that increase the odds of anesthetic-related death in individual dogs and cats are being in worse health, urgent procedures, age, long procedures, use of injectable anesthesia rather than inhalant anesthesia, obesity, and brachycephaly.
Factors that decrease the odds of anesthetic-related death are an equipment check with a protocol and checklist, direct availability of an anesthesiologist and a trained nurse, no change of anesthetics during the procedure, two people available for emergencies, post-operative pain management, epidural or local analgesia rather than systemic analgesia, pulse oximetry, and monitoring in general.
Dr. da Cunha said all the studies—on horses, rabbits, cats, dogs, or humans—agree that monitoring is key to reducing mortality rates. He also recommended following an anesthesia checklist to prevent mistakes, as he does.
The imperfect anesthetist
Heidi Reuss-Lamky, a veterinary technician specialist in anesthesia and surgery at Oakland Veterinary Referral Services in Oakland County, Michigan, spoke at the AVMA Virtual Convention 2020 on “Anesthesia Mistakes Awareness.”
Reuss-Lamky said the perfect anesthetist would have access to excellent anesthesia and monitoring equipment; do a pre-anesthetic workup and hands-on monitoring; know a lot about pharmacology, physiology, and pathophysiology; have good communication skills; stay current on continuing education; do great post-operative support; and have a little bit of intuition. Plus, he or she would never have a bad day.
“We’re people, right? We’re not machines,” Reuss-Lamky said. “And so everyone will eventually have a bad day, and mistakes can and do happen.”
She listed the following areas of concern with the patient, pharmacology, monitoring, anesthesia, and the anesthetist.
- The patient: Inadequate preoperative workup, undiagnosed underlying disease, mismanaged preexisting conditions, clinicopathologic abnormalities, inadequate preoperative stabilization, emergency situations, fearful or feral patients, and human errors such as recording the incorrect weight.
- Pharmacology: Administering a drug by the wrong route, incorrect drug dose calculations, human errors such as medicating the wrong patient, and adverse drug interactions.
- Monitoring: Incorrect monitoring devices, patient’s abnormality not accurately reflected by the monitor, inaccurate data provided by the monitor, relying too heavily on monitors, and accurate data provided by the monitor but ignored or alarms silenced.
- Anesthesia: Improper flow rates, not scavenging waste anesthetic gases, broken or improper equipment, unidentified malfunction in the anesthesia machine, poorly maintained anesthetic equipment, and post-operative hypoventilation.
- The anesthetist: Incorrect use of the anesthetic machine or equipment, inadequate preoperative preparation or stabilization, breathing and ventilation errors, substandard patient monitoring, the many stresses that veterinary technicians face, and poor communication.
Reuss-Lamky said checklists are heavily used in human medicine and are creeping into the veterinary side. She showed a pre-surgical checklist used in her practice. When developing a checklist, she said, a practice should get input from all staff members to be make sure the checklist will be well used after implementation.
There are no safe anesthetic agents, there are no safe anesthetic procedures. There are only safe anesthetists.
Robert Smith, MD
She said, in summary, that preventing anesthesia mishaps involves proper patient preparation, training and experience, adequately functioning monitoring devices and anesthetic equipment, and diligent post-operative monitoring.
Continuum of care
When anesthetizing patients, veterinary teams follow the adage: “The lighter, the better. The deeper, the deader.”
Dr. Tamara Grubb, a veterinary anesthesiologist, and Jennifer Sager, a veterinary technician specialist in anesthesia, spoke at AAHA Connexity on “The Calmer, the Better: How to Defuse Fear and Infuse Enthusiasm by Following the 2020 AAHA Anesthesia and Monitoring Guidelines for Dogs and Cats.” Dr. Grubb and Sager co-chaired the task force that prepared the guidelines.
Dr. Grubb, an adjunct clinical professor at Washington State University College of Veterinary Medicine, said: “We all know that anesthesia can be really scary because anesthesia, of course, creates a physiologic plane that is somewhere much deeper than normal sleep. And it should always create a little bit of enhanced attentiveness, but it doesn’t need to be scary.”
According to the AAHA guidelines, “In addition, ‘anesthesia’ is not limited to the period when the patient is unconscious but is a continuum of care that begins before the patient leaves home and ends when the patient is returned home with appropriate physiologic function and absent or minimal pain levels.”
Dr. Grubb said the guidelines are divided into three phases with numerous steps that can serve as a descriptive checklist for the entire anesthesia team, as follows.
Phase I: Pre-anesthesia: Individualized anesthetic and analgesic plan, client communication.
- Step 1: Pre-anesthetic evaluation and plan.
- Step 2: Client communication and education.
Phase II: Day of anesthesia: From doorknob (home) to doorknob (home) and everything in between.
- Step 1: Anesthesia begins at home, with fasting and sometimes medications.
- Step 2: Equipment preparation.
- Step 3: Patient preparation.
- Step 4: Anesthetic protocol.
- Step 4a: Pain management.
- Step 4b: Pre-anesthetic anxiolytics and sedatives.
- Step 4c: Anesthetic induction.
- Step 4d: Anesthetic maintenance, including physiologic monitoring, physiologic support, and troubleshooting of anesthetic complications.
- Step 4e: Recovery.
Phase III: Return home.
Sager, education and training specialist at the University of Florida College of Veterinary Medicine’s Small Animal Hospital, emphasized putting safety first with anesthesia and seeing anesthesia as multidimensional—scary, but fun as a challenge. Her key points are to pay attention to equipment selection, develop individual anesthetic plans, and use multimodal anesthesia techniques.
In the realm of anesthesia overall, Sager advised practices to take the time to invest in clients with communication and education and to take the time to invest in the veterinary staff with training.