Every patient must be evaluated before anesthesia. The patient history is a vital part of the preoperative process and in
some cases will clue the practitioner of potential problems better than lab results and radiographs.
Photo 2: Handheld ECG machine wirelessly transports images to a printer located in the treatment room
When the physical exam is normal in our office, age-appropriate and condition blood tests and electrocardiograph evaluations
are performed. Thanks to the advent of easy-to-operate, economical blood analyzers, which deliver almost instantaneous valuable
results, and handheld electro-cardiographic devices, all anesthetic procedures are preceded with patient blood analysis and
ECG (Photo 2). Much like a pilot performing a pre-flight checklist, run through a list of critical systems beforehand. I also
want to know as much as possible about the patient. Argument can be made that preanesthetic testing lacks evidence-based medical
rational (preanesthesia lab testing and ECG equals or does not equal a successful anesthetic event), if you compare preoperative
testing to a pilot's preflight checklist, both the veterinarian and pilot want to know as much as practically possible before
an event. It just adds to our comfort knowing as much about our patient as practical before performing a procedure that will
drastically alter its current status. Additionally, the testing makes the client feel more secure. Before dental anesthesia,
my own clinically normal 4-year-old Lowland Sheepdog's blood work revealed a 3.9 creatinine, albumin 1.9, urine specific gravity
1.014 with 3+ protein and a urine-protein-creatinine ratio of 6.2!
For procedures expected to last less than two hours, our protocol is:
- Patients under 1 year of age without apparent physical organ function disease: CBC, ECG rhythm strip, stool examination.
- Patients between 1 and 3 years: CBC, mini-profile, six-lead ECG, urinalysis with sediment with ERD test.
- Patients between 3 and 7 years old: all of the previous tests plus full chemical profile, electrolytes.
- Patient older than 7 years and patients undergoing a procedure expected to last greater than two hours: all of the previously
mentioned tests plus three-view chest radiographs, blood gas/acid base status. In animals with low albumin or those that have
proteinuria, a urine-protein-creatinine ratio is also evaluated. The beauty of blood gas analysis is that we can respond to
findings before anesthesia as well as during. If electrolytes are abnormal, the fluid type used is changed (with high sodium
and chloride values, we use dextrose 5 percent water. If the pH is decreased, we use lactated ringers. If PO2 is low and PCO2 is high, we would assist ventilation.
If all the preoperative tests are normal before the patient is anesthetized in our office, the doctor signs off on the case.
Much like our pilot example, the procedure helps confirm that the tests were performed and evaluated.
The correct anesthesia protocol
Anesthesia protocols vary by patient age, condition, co-morbidity factors, length of and type of procedure. Local anesthetics
are used on all operative dental procedures where tissue is incised. There are many anesthesia protocols; the best one is
the one that you are most comfortable with. Here is the one that has met with success in our office:
- Premedication/induction/maintenance: an intravenous catheter and fluids are placed in all patients undergoing anesthesia.
For healthy dogs, our first choice is hydro-morphone 0.1 to 0.2 mg/kg or morphine 0.5 to 1.0 mg/kg combined with acepromazine
0.010 to 0.040 mg/kg. No anticholinergic unless patient demonstrates need, are pediatric or brachycephalic.
As they become more debilitated or aged, we shift toward hydromorphone 0.1 to 0.2 mg/kg alone or with midazolam 0.2 to 0.4
mg/kg. Still no anticholinergic unless specific need.
For healthy cats, our first choice is hydro-morphone 0.2 mg/kg or butorphanol 0.2 mg/kg combined with medetomidine 0.010 to
0.015 mg/kg, plus atropine.