Chapter 1 Part 1

Pages 5-26

PREANESTHETIC PERIOD

While the preanesthetic period

refers to the period immediately proceeding the induction of anesthesia, preparation for surgery can begin long before an animal is anesthetized.

Some PREANESTHETIC responsibilities of a technician include:

• obtaining patient history• reviewing consent form with an owner• making sure the patient is fasted• performing a physical exam• drawing blood and running diagnostic tests• placing an IV catheter• calculating drug doses• administering premedications• preparing anesthesic equipment

Feeling overwhelmed?

NO TWO PATIENTS ARE ALIKE!!!!

Anesthesia is NOT a cookie cutter procedure. Age, breed, size, and

health status are some of the factors that can play into the selection of anesthetic agents and techniques.

MINIMUM DATA BASEInformation used to evaluate a patient’s readiness for anesthesia is gathered into a MINIMUM DATA BASE which varies with each clinic/veterinarian/patient, but should

ideally include:

HISTORY, PROCEDURE TO BE PERFORMED, PHYSICAL EXAM,

DIAGNOSTICS and CONSULTATION TO DETERMINE PHYSICAL STATUS AND

ANESTHETIC RISK

FASTING• Fasting usually begins the night before surgery.

WHY FAST?

• Fasting is done to avoid vomiting/regurgitation during surgery or recovery which can cause esophagitis, respiratory obstruction, or aspiration pneumonia.

HOW LONG SHOULD THE FASTING PERIOD BE?

• Adult dog or cat: Withhold food for 8-12 hours before surgery. Water is withheld anywhere from 2-10 hours before surgery, depending on the veterinarian’s preference.

• Pediatric patients less than 3 months or less than 4 pounds: Much shorter fasting period (depending on species, could be 4-6 hrs, or no fasting) to avoid dehydration or hypoglycemia.

• GI surgery: Withhold food for 24 hours, water for 8-12 hours.

• In addition to not fasting long enough, it is not safe to have animals fasted for too long.

– This usually refers to animals refusing to eat for various reasons - usually when the surgery is not elective: serious GI obstructions/perforations, or in the situation where 2 surgeries are performed several days apart and the animal does not want to eat in between the surgeries.

• This leads to a longer recovery period, delays healing, and puts the animal at risk for other medical problems (hepatic lipidosis).

• Options include hand/syringe feeding, inserting feeding tubes, or total parenteral nutrition.

HISTORY TAKINGALWAYS LOOK FOR WAYS TO MODIFY YOUR METHOD. LEARN FROM YOUR EXPERIENCES.

LIMIT POSSIBLE YES OR NO QUESTIONS – THEY PROVIDE LITTLE INFORMATION!

EXAMPLE: Instead of asking “Does your dog drink a lot of water?”, ask “How much water does your dog drink daily?”.

DON’T ASK LEADING QUESTIONS!

EXAMPLE: Don’t ask “Your dog doesn’t drink much, does he?”

ALLOW THE CLIENT TO ANSWER, DON’T UNKNOWINGLY GUIDE THEM

TO AVOID/CHOOSE ABNORMAL/NORMAL ANSWERS.

YOU WILL GET AMORE TRUTHFUL EVALUATION.

So what questions should I ask?

• What procedure(s) is/are being performed today?• How old is your animal?• Is there a history of previous

illnesses/problems/treatment and if so, do you have past medical records?

• Is your pet currently ill?• What medications has your pet been on?• Does your pet have any allergies or a history of drug

reactions?• Has your pet had any previous anesthetic problems?• Is your pet current on vaccines?• Is your pet in heat or pregnant?

CONSENT FORM• Have the client sign a consent form/estimate.• This should be done in person. By phone is

an option, although this is not ideal. Make sure a witness also hears the authorization.

• A consent form reviews anesthetic risks, resuscitation options, blood work options, and phone numbers for the owner.

• Some forms also state that a drug will be used on their animal in an extra-label manner.

* If possible, have the owner read the estimate and consent form before the day of surgery.

PHYSICAL EXAM

The physical exam is done by a veterinarian, but a technician can also perform an

exam. This can easily been done when drawing blood for diagnostics.

POINT OUT WHAT YOU FIND (EVEN WHAT MAY SEEM OBVIOUS) AS

SOME THINGS ARE EASILY OVERLOOKED ON A BUSY

SURGERY DAY. Write down your findings and also tell them to the

doctor.

SIGNALMENT: species, breed, weight, age, sex, reproductive status

THIS IS HOW EVERY ANIMAL’S HISTORY SHOULD BEGIN

Example: “Tiny is a 4 year old intact female Pug who weighs 33 pounds.”

THE SIGNALMENT HAS A LOT OF IMPORTANT INFORMATION

SPECIES AND BREED

• Usually don’t have to say the species if the breed makes it obvious

• Doses are different between species and are listed accordingly in drug manuals. NEVER ASSUME that the dose for one species will be the dose for another.

Each animal will respond differently to various drugs and have different anesthetic needs

Example: Thiopental is an injectable induction agent that usually has a short recovery time because it is highly lipid soluble,

meaning it moves quickly from brain to muscle and then to fat. Sighthounds have a low amount of fat, so the drug remains in

effect for a longer period of time.

Tiny is a Pug- what anesthetic concerns exist for this breed?

Brachycephalic breeds are at risk for having an elongated soft palate which can make intubation and

recovery difficult.

WEIGHT

• Dosages are based on weight in addition to species. DON’T ESTIMATE. Weigh accurately.

• Use a pediatric scale (if available) if less than 15 kg – will read pounds and ounces.

• Compare current weight to previous weights.

• IV fluid rates are also weight based.

WEIGHT CONT’D….

OBESE ANIMALS can experience dyspnea, they can be difficult to draw blood from, harder to assess hydration status, anddifficult to auscultate any abnormalities.

THIN ANIMALS can be at risk for hypothermia and may have an underlying condition causingweight loss.

AGE• VERY YOUNG ANIMALS (usually less than

8 weeks) are less capable of metabolizing injectable drugs because the liver is not

fully developed and most biotransformation occurs in the

liver.

• GERIATRIC ANIMALS may have poor organ function and may not be able to properly handle the metabolism. This leads to a potentially slow recovery.

REPRODUCTIVE STATUS

• Is there a possibility of pregnancy?

Affects which drugs are used – want minimal affect on fetuses

• Are both testicles descended? Affects clip, prep, surgery

• Always check females for evidence of a spay scar or tattoo

SEX

ALWAYS BE SURE THAT THE FEMALE CAT WHO ARRIVES TO BE SPAYED IS ACTUALLY A FEMALE!

No one wants to spay a male!

BEYOND SIGNALMENT

DISPOSITION AND ACTIVITY LEVEL

• Anxious or aggressive animals may require a combination of drugs for sedation, or more potent medications.

• Fearful or aggressive animals may require a different route of medicine administration (ex: oral, induction chamber)

ASSESSING HYDRATION STATUS

PHYSICAL FEATURE

5% (mild)

DEHYDRATED

6-9% (moderate) DEHYDRATION

10-12% (profound)

DEHYDRATION

EYELID PINCH MILD TENTING; PINCH SLOWLY RELAXES

SEVERE TENTING; PINCH PERSISTS

SEVERE TENTING; PINCH PERSISTS

CORNEA CORNEA MOIST; TEARING STILL POSSIBLE

CORNEA DRIER; TEARING INFREQUENT

DRY CORNEA; NO TEARING

EYEBALL POSITION IN ORBIT

MINIMAL SPACE BTW. MEDIAL CANTHUS AND GLOBE (1-2mm)

PRONOUNCED SPACE BETWEEN (2-4 mm)

SPACE IS LARGER THAN 4 mm

SKIN ON NECK DECREASED PLIABILITY

TENTED SKIN PERSISTS 3-5 sec

TENT PERSISTS > 5 sec

ORAL MUCOUS MEMBRANES

MOIST, WARM, PINK

WARM, STICKY, PALE

DRY, COLD, CYANOTIC OR PALE. POOR CRT

GENERAL CONDITION

STANDING; EXTREMETIES ARE WARM

OFTEN RECUMBENT

OFTEN MENTALLY DULL, EXTREMITIES COLD, RAPID PULSE

LAB FINDINGS NORMAL INCREASED PCV AND TOTAL PROTEIN, DECREASED URINE VOLUME

SAME

Ideally, dehydration should be corrected prior to surgery.

(Wt in kg)(1000 mL/kg)(% dehydration)

EXAMPLE:A 33 lb dog that is 9% dehydrated, needs

_______mL

33 lb /2.2 = 15 kg(15 kg)(1000 mL/kg) = 15,000 mL

(15,000 mL)(0.09) = 1350 mL

HEADORAL CAVITY- Breathing noises can indicate an anatomical problem.- Check gum color and capillary refill time (CRT)

- NOTE: Animals with pigmented gums can still be analyzed. Look at conjunctiva, inner vulva, prepuce to assess.

http://www.infovets.com/demo/demo/canine/B105.HTM

HEAD cont’d• Look at the ears and nose for any signs of growths,

infection, or ear mites

EYES• Observe not only for signs of dehydration, but also

look at pupillary reflexes (help localize the lesion – nerves vs. eyes. vs. brain)– NOTE: Some anesthetics or excitation will alter this.

AUSCULTATION

RATE RHYTHM ABNORMAL SOUNDS

DOGS

= 60-180 bpm (breed dependent)

= 10-30 bpm

CATS

= 110-220 bpm

= 25-40 bpm

Age and excitement, in addition to

medical conditions, can alter rate

Listen for normal

sinus rhythm versus

arrhythmias

Listen for murmurs,crackles, wheezes,

and extra heart beats.

Look for open-mouthed breathing, flared nostrils,

excessive panting, abdominalbreathing, stance, and cyanosis

Listen to all 4 quadrants of chest and all 4 valves.Cat murmurs are often

sternal in location.

PULSE

Assess the strength and rate• The femoral artery on the medial aspect of

the hind leg is the easiest location to palpate• Can also use the metatarsal/metacarpal

artery, sublingual artery, dorsal pedal artery• Strong/weak pulse correlates with blood

pressure• Pulse deficits = heart disease

OTHER THINGS TO LOOK FOR:

• BODY TEMPERATURE: N = 99.5-102.5°F

• LIMBS: look for signs of pain/lameness• LYMPH NODES: Are they palpable? Are they

firm?• ABDOMINAL PALPATION: feel for

abnormalities in organ size, location, fluid or gas within abdomen, fetuses, feces

• MAMMARY GLANDS: Are they engorged? Are there lumps? Is the animal lactating?

• PREPUCE/VULVA: Look for anatomical abnormalities and discharge

DIANOSTIC TESTS

• The extent of Diagnostic Testing performed as part of the MINIMUM DATA BASE depends on the clinic policy, owner consent, and what is ideal for the animal.

• It is important to provide the most complete and affordable testing available, depending on the clinic.

• PCV and RBC – used to determine the blood’s ability to deliver oxygen to

tissues. Increases usually indicates dehydration (which leads to increased viscosity of the blood, poor perfusion and decreased cardiac output). Decreased levels usually indicates anemia.

• TOTAL PLASMA PROTEIN – usually indicates dehydration if increased or a loss through

the renal, hepatic or GI systems if decreased. Decreased levels can lead to drug potency.

• BLOOD SMEAR – used to evaluate red blood cells, white blood cells, and

platelets grossly.

URINALYSIS

• SPECIFIC GRAVITY – used to detect evidence of dehydration or renal insufficiency

• GLUCOSE and KETONES – used to detect diabetes

• WBCs and RBCs – can be seen with urinary tract infections and crystalluria(can also be normal in small amounts)

• USE THESE RESULTS IN CONJUNCTION WITH OTHER TESTS

CHEMISTRY PANEL

MOST COMMONLY EVALUATED PARAMETERS PRE-OPERATIVELY

ARE:

ALP, ALT, BUN, CREATININE, GLUCOSE, ELECTROLYTES

The more parameters that are evaluated, the better picture we

have of the patient.

CLOTTING TIMES

• Not commonly performed for routine procedures unless coagulopathies are suspected.

• In-clinic testing is performed by either performing a Buccal Mucosal Bleeding Time (BMBT), a short nail trim to the quick, or placing whole blood in a plain red top. Blood should clot within 4 minutes.

ECG

Evaluates electrical activity, pattern, rhythm, size, and shape

• Do if heart disease is suspected, there is a history of trauma, electrolyte abnormalities, or if the animal is geriatric

RADIOGRAPHS are not routinely done in private practice, but are indicated with dyspnea, abnormal heart/lung sounds, or history of recent trauma.

HEARTWORM TEST – it is important to know heartworm status before undergoing anesthesia

ANESTHETIC STATUS

• Classification based on history, physical exam, and diagnostics performed

• Classification is objective and can change with animal’s status

• Correct problems before surgery if possible

Category Physical condition Examples

Class I

Minimal risk

Normal, healthy animal w/o underlying disease

Spay, neuter, declaw, hip rads

Class II

Slight risk, minor disease

Slight to mild systemic disturbances; animal compensate

Neonates, geriatric, obese, skin tumors, uncomplicated hernia, local infection

Class III

Moderate risk, obvious disease

Moderate systemic disease, mild clinical signs

Anemia, moderate dehydration, fever, low-grade murmur or heart disease

Class IV

High risk, significant disease

Preexisting systemic disease

Severe dehydration, shock, uremia, high fever, severe heart or lung disease, diabetes, emaciation

Class V

Extreme risk, moribund

Life threatening disease that may not be corrected by surgery, animal may not survive 24 hrs

Advanced heart, liver, kidney, lung, or terminal disease, severe shock, head injury, severe trauma

What anesthetic status would you give this dog?

2yr old, mixed breed intact male weighing 12lbs; BCS: 2/5,T-103.5, HR-160, RR-40; 8% dehydratedBloodwork: PCV: 35%, TP: 7.6 g/dl

Preanesthetic Pic of the Day

Based on the picture, what anesthetic category would you place

Oscar in?