Many variables affect anesthesia including the patient, the sedative and anesthetic agents used and the anesthetist.
Many variables affect anesthesia including the patient, the sedative and anesthetic agents used and the anesthetist. Veterinary patients pose a greater anesthetic challenge than human patients because of weight and breed variables, monetary limitations and often the lack of a comprehensive anesthetic history. Preanesthetic testing helps identify pre-existing conditions thus improving anesthetic safety but also providing valuable baseline data for future comparison. Furthermore, not offering preanesthetic testing can open your practice to liability issues and create anesthetic nightmares.
Preanesthetic profiling young patients was a new concept in the 1980's and emerged as more common occurrence in the late 1990's. Client compliance is frequently an issue with new programs and preanesthetic testing is a good example.
To overcome these challenges, Metzger Animal Hospital developed a client consent form for preanesthetic testing in 1996.The original form explained the purpose of the tests, likening them to tests a physician would run if the client were to undergo surgery. Clients would choose among three Pet Health Screens, based on the animal's age and health status, and then sign the form which resulted in client compliance of approximately 65-70% (Form #1).
In 1997, compliance increased to over 80 percent after the hospital started mailing the form before the scheduled surgery or dental date with a cover letter emphasizing the importance and advantages of testing. In addition, the letter served as a reminder and included a pre-surgery checklist (Form#2).
In 1998 Metzger Animal Hospital instituted mandatory preanesthetic testing for all surgical and dental procedures. Tests include the CBC, biochemical profile with electrolytes for all patients and adding thyroid testing (total T4) for all patients over 7 years of age. Advantages include a more comprehensive testing protocol, less client confusion and better team member efficiency.
Comprehensive laboratory profiling allows for a more thorough evaluation of organ systems including hematopoetic, renal, hepatic and endocrine systems. Proper evaluation of testing parameters frequently depends on one another, for example evaluating calcium and albumin or amylase with renal function. Hematology is a very important preanesthetic test because anemia, polycythemia, leucopenia, Leukocytosis and thrombocytopenia may contribute to adverse anesthetic events (ref_Guide to hematology). Pre-existing renal or hepatic disease may interfere with anesthetic metabolism and excretion especially in anesthetics requiring biotransformation and elimination. Undetected hypoglycemia may result in serious cerebral dysfunction and death. Electrolyte abnormalities such as hyperkalemia may predispose the patient to life-threatening cardiac arrhythmias.
Client confusion is eliminated with mandatory preanesthetic testing because no forms or signatures are required and a consistent unified message is communicated that the practice believes the testing is important. Preanesthetic testing is analogous to pain management-you either believe in it or you don't.
Front office and technician team members welcome mandatory testing because once again, no forms or signatures are required. Front office staff can focus on clients instead of answering questions about the cost and forms. With mandatory testing technicians no longer need to review forms to see which patients receive the needed testing.
Mandatory preanesthetic testing is becoming the standard of care and the veterinary team needs to explain the safety benefits to patients and visually review the results with owners when the patient is discharged.
The cost of testing must be weighed against the benefits. Statistically speaking anesthetic complications and abnormalities detected on preanesthetic testing are uncommon. A recent study of nearly 1,000,000 patients (254,530 cats with an average age of 8 months and 738,276 dogs averaging 10 months of age )undergoing pre-anesthetic profiling, reported 9% of patients had one or more laboratory parameters outside of the normal reference range. Preanesthetic testing included a CBC and a 12 chemistry biochemical profile. Table 1 shows results of various preanesthetic abnormalities and their relative incidence in patients presented for ovariohysterectomy, castration or dental procedures. Note that electrolytes were not part of the preanesthetic protocol included in the study which would undoubtedly increase the % of patients with results deviating from the reference range. Also note that every abnormality may not significantly affect anesthesia or surgery, however other parameters like HCT, platelet count and creatinine might significantly affect patient recovery and survival.
Mel, a Metzger Animal Hospital client dedicated the following to her puppy Ruca and the transcript is from her web site.
"Ruca, a chocolate, Labrador retriever, was born January 2, 2004.She was a very affectionate puppy, and learned very quickly, performing her commands at only 3 months of age!!! She loved our cat, Saydi; she was a wonderful puppy, and a wonderful addition to our family. Her life was short, but as with any amazing being, her impact was immense. She taught me to love animals intensely, and to love unconditionally." "At exactly 5 months of age, I dropped Ruca off at 7:30AM to Metzger Animal Hospital for her scheduled spaying surgery. I chatted with Beth, one of the receptionists and gave Ruca kisses. Beth explained that they perform blood tests on all patients receiving anesthesia and it was included in the spay price. I commented to Beth (receptionist) that I wished she could stay that size forever, a comment that would soon come back to haunt me." "I received a call at 10AM from our veterinarian; his voice was serious and he was very concerned. He explained that Ruca's blood work showed evidence of kidney failure. He requested that the technician run the blood analysis again, just to be sure the results were Ruca's. He requested my permission to perform an ultrasound. I agreed, of course, and he called back within an hour to inform me that Ruca's kidneys were badly deformed, and that her condition was congenital. The prognosis was heart-breaking: this sweet little puppy very likely had only a few weeks to a few months to live."
"At Metzger's (and many other reputable veterinarian hospitals nationwide); blood work is performed prior to any major surgery, to ensure that the animal is healthy. In Ruca's case, the findings were devastating, but at least we were able to take measures to treat her and to keep her comfortable for a while longer. Needless to say, Ruca was not spayed that second day of June."
" On her last day, I grilled her NY Strip steak, and bought some fresh watermelon! She LOVED watermelon. However, our sick little Rica wouldn't eat even one bite of the steak. She managed one piece of watermelon, and then turned her nose up at the rest of it. The rest of the day, she lay on the couch awake.... she didn't even sleep.... she just lay there. Her behavior that day assured us that we had made a fair decision." Ruca was a special dog and I love her in a way I cannot express. She taught me a lot about life, both good things and wonderful things, and about loving animals!!! She also taught me about the harshness of nature... the unfair things about life. My husband, other dog Paris and I miss her very much, but are getting along very well these days. There is even talk of getting another dog."
"We are forever grateful to every veterinarian, technician and staff member at Metzgers. They were all so kind to us, and to our animals, of course, throughout all of this. Their sincere care helped to lessen the anguish of this situation. "
Ruca's case emphasizes the value of preanesthetic diagnostics because anesthesia could have resulted in many complications including death. Contemplate Ruca surviving surgery only to present with renal failure several days later, leading the owners (and perhaps the veterinarian) to speculate that the surgical procedure resulted in renal failure. Ill feelings and perhaps legal action might be an unfortunate consequence of not performing preanesthetic profiling or at least offering it to every client. Anesthetic complications are rare and significant preanesthetic testing abnormalities are uncommon, however in the eyes of a grieving client failure is 100%.
Lees, GE. 1998. Congenital renal disease in dogs and cats. ACVIM-Proceedings of the 16th Annual Veterinary Medical Forum, p 28-30.
DiBartola, SP. 1995. Familial renal disease in dogs and cats. In E.J. Ettinger and E.C. Feldman (eds) Textbook of Veterinary Internal Medicine, p. 1796-1801. W.B. Saunders Co., Toronto.
Rebar, AH; Metzger FL 2002. Hematology in practice. A Guide to hematology in dogs and cats, p5-8