2. patient preparation

1Copyright © 2011, 2003, 2000, 1994 by Mosby, Inc., an affiliate of Elsevier Inc.

Patient Preparation

All successful anesthetic procedures begin with careful patient preparation.

Chapter 2


Role of the Veterinary Anesthetist

Minimum patient database Proper patient fasting Preinduction patient care All supplies are available All equipment is in working order Preanesthetic medication


Communication is Important

Makes clients feel more comfortable and less anxious

Clients are more confident in your work Good communication shows you care An informed client can better handle

unexpected results


Clients don’t care how much you know, until they know how much you

care.


Minimum Patient Database (MPD)

Patient history Physical examination and assessment Preanesthetic diagnostic workup


Confirm the Scheduled Procedure

Verbally Prevents tragic accidents

Anesthetizing the wrong patient Performing an unnecessary procedure Not performing a scheduled procedure


Confirm the Scheduled Procedure (Cont’d)

Know the specifics Exact location of tumors Exact location Owner’s wishes regarding cytology or histology Owner’s wishes regarding decisions during the

procedure


Patient History

Information obtained from the client Know what questions to ask and how to ask

them Yes-no questions Leading questions


Patient History (Cont’d)

In addition to information given freely, determine the following: Information given freely Duration Severity or volume Frequency Appearance or character


Patient History—Signalment

Species Species have unique responses to anesthetic

agents Horses and cats—opioids Dosing requirements Recovery—horses Anticholinergics avoided in ruminants Ventilation support—large animals Excess airway secretions—cats and ruminants Exotic animals are handled differently


Patient History—Signalment (Cont’d)

Breed Differences in anatomy and physiology Sighthounds—sensitive to barbiturates Boxers and giant breeds—sensitive to

acepromazine Terriers—resistant to acepromazine Brachiocephalic dogs—difficult to intubate Draft horses—sensitive to sedatives



Age Plays a factor in drug choice

• Neonates and pediatric patients• Geriatric patients



Sex and reproductive status Male or female Intact or neutered Used for breeding? Pregnant Stallions—acepromazine Pregnant cows and ewes—xylazine


Patient History—Medications

Current or past May influence effect of anesthetic agents Sympathomimetics Tricyclic antidepressants Antibiotics Monoamine oxidase inhibitors Antihistamines


Patient History—Allergies/Drug Reactions

Record in the history to prevent future administration

Past adverse reactions to anesthetic agents Cats—prolonged ketamine recovery Dogs—behavioral change after acepromazine

sedation


Patient History—Preventive Care

Vaccination—date and type Fecal analysis and parasite control Heartworm status—dogs FLV and FIV testing—cats Tetanus toxoid—horses


Patient History—Past/Current Illnesses

Preexisting disease Anorexia, vomiting, diarrhea, coughing,

sneezing, polyuria, polydipsia, tenesmus, dysuria General signs of illness Stabilized prior to anesthesia

Change in behavior CNS disorder Pain Systemic illness


Patient History—Past/Current Illnesses (Cont’d)

Exercise intolerance Heart disease Anemia Musculoskeletal pain

Weakness A nonspecific sign

Fainting or seizures Often difficult to differentiate Have different etiologies


Past History—Past/Current Illnesses

Unexplained bleeding Bruising Blood in feces or urine Prolonged bleeding after injury

Associated with coagulation disorders Increased risk of intra- and postoperative

hemorrhage


Other Considerations

Written estimate Signed consent form

Legally necessary Informs of risks Standard forms are available Owner’s daytime phone number Permission to perform CPCR Lists extralabel drugs used


Physical Examination (PE) vs. Physical Assessment (PA)

PE Performed by a veterinarian To determine diagnosis and treatment planning

PA Performed by a veterinary technician To provide patient care, respond to patient needs,

detect changes in patient condition PE and PA

Both necessary and important to ensure high quality of patient care


Physical Examination/Physical Assessment

Examine the entire patient Use a consistent technique

Head to tail Organ system

Cardiovascular, nervous, and pulmonary systems are most affected by anesthetic agents


Patient Identification

Cage tags Patient identification collars Document external characteristics in medical

record Species and breed Size Hair coat length Color


Body Weight

Must be accurate for proper dosing <5 kg use a pediatric scale <1 kg use a gram scale Horses—estimated weight

body weight (kg) = heart girth (cm)2 × length (cm) 11880

Weigh animals immediately before anesthetic procedure

Compare current weight with previously recorded weight


Body Condition Score

Assessment of patient weight to the ideal weight

A numeric assessment 1-9 scale

• 4-5 in dogs or 5 in cats is the ideal weight • 1 is extreme cachexia; 9 is extreme obesity

1-5 scale• 3 is the ideal weight• 1 is extreme cachexia; 5 is extreme obesity

Body condition influences patient management


Hydration Assessment

Skin turgor Placement of eye in orbit Mucous membrane color, refill time, moisture level Heart rate and pulse strength Correct hydration abnormalities prior to anesthesia Young and obese patients appear more hydrated Old and cachectic patients appear less hydrated Panting dries the mucous membranes


Level of Consciousness (LOC)

To assess brain function Patient’s responsiveness to stimuli Healthy patients: alert, responsive, bright or

quiet Lethargic (lethargy) Obtunded (obtundity) Stuporous (stupor) Comatose (coma)


Pain Score

Assess patient’s level of pain To help select preanesthetic and anesthetic

agents


Body Temperature

Use a rectal thermometer Elevated = inflammation Decreased = numerous systemic disorders


General Condition

Visual examination from a distance Gait Temperament

Anxious or excited? Or ill? Activity level

Exercise intolerance Weakness

Will affect choice of anesthetic agents and methods of administration


Exterior Surfaces

Hair coat Skin

Part the hair and look at the skin Lymph nodes and mammary glands

Visual and manual examination Body openings

Odors and discharges Eyes, ears, nose, oral cavity (throat)

EENT


Pupillary Light Reflex (PLR)

Normal—pupils are the same size

Direct reflex Consensual reflex


Cardiovascular System Examination—Heart Rate

Measured as beats per minute (bpm) Auscultation of left chest wall Large animal patients vs. small animal

patients Obese animals, panting dogs, purring cats Pediatric patients Exercise or stress of handling


Cardiovascular System Examination—Heart Rhythm

Evaluation of the heart rate Normal sinus rhythm (NSR)

Dogs, cats, rodents, ferrets, rabbits, horses, ruminants

No rhythm irregularities Sinus arrhythmia (SA)

Dogs, horses, ruminants Heart rate is affected by respiration


Cardiovascular System Examination—Heart Rhythm (Cont’d)

First degree atrioventricular (A-V) heart block Delayed conduction through the A-V node Detected only on ECG tracing

Second degree A-V heart block Periodic block of conduction through the A-V node Results in skipped heartbeats


Cardiovascular System Examination—Murmurs

Listen over each valve Cranial-most aspect of left axilla—PDA

Caused by blood flow turbulence May result in increased patient anesthetic risk


Cardiovascular System Examination—Pulse

Pulse palpation points Dogs and cats—femoral artery Large animals—facial artery, ventral tail artery, or

auricular artery Pulse deficit Blood pressure estimate


Cardiovascular System Examination—Mucous Membrane Color

Mucous membrane color Gingiva at base of tooth Alternate sites Pale or cyanotic membranes

Capillary refill time (CRT) Normal = <2 seconds Prolonged refill time


Respiratory System Examination—Breath Rate

Measured in breaths per minute (bpm) Evaluated visually Inversely proportional to body size


Respiratory System Examination—Breathing Character

Effort Dyspnea and cyanosis

Relative length of inhalation and exhalation Regularity of inhalation and exhalation Inhale – exhale – rest – inhale –exhale –rest


Respiratory System Examination—Lung Auscultation

Four quadrants Discontinuous sounds Continuous sounds


Abdominal Palpation and Auscultation

Normal is soft and not painful Firm or painful structures Abdominal distention Borborygmus—large animals Rumen contraction—ruminants


Preanesthetic Diagnostic Workup

No one standardized diagnostic workup fits every patient to be anesthetized Geriatric patient workup Elective surgery patient workup Sick patient workup Workup based on age, history, and physical

examination Workup based on financial considerations

Completed after the patient history has been taken and the physical examination has been performed


Preanesthetic Diagnostic Testsand Procedures

Complete blood count (CBC) Urinalysis Blood chemistry Blood coagulation screens Electrocardiogram (ECG) Radiography Other tests as deemed necessary


Physical Status Classification

Classification is based on an evaluation of the Minimum Patient Database

Rates patient anesthetic risk American Society of Anesthesiologists Class P1 = minimal anesthetic risk Class P5 = extreme anesthetic risk Classes P1 and P2 use standard anesthetic

protocol Classes P3 to P5 need special protocols and

stabilization


Anesthetic Protocols

Established by the veterinarian Factors considered

Facilities and equipment Familiarity with anesthetic agents Nature of the procedure Circumstances specific to a procedure Cost Urgency


Preinduction Patient Care

Withholding food Complications

• Esophageal reflux, vomiting, regurgitation, pulmonary aspiration, pneumonia

if the patient is not fasted, one of several actions must be taken.

Preanesthetic with antiemetic properties Patient stabilization

Sick patients Patients with concurrent conditions Reduces anesthetic risk


Intravenous (IV) Catheterization

Reasons for placing an IV catheter Fluid administration Rapid IV access in an emergency Constant rate infusion (CRI) of drugs or anesthetic

agents Administration of vesicants Sequential administration of incompatible drugs


Intravenous Catheters

Through-the-needle Over-the-needle

Most commonly used 16-24 gauge, 3/4- to 2-inch catheter (small

animals) 12-16 gauge, 5¼-inch catheter (large animals)


IV Catheter Placement and Maintenance

Length Size Location Administration set with injection port Free-flowing fluids Minimal patient and catheter movement Slow administration Saline flush


Placing an IV Catheter in a Small Animal Patient

Equipment


Placing an IV Catheter in a Small Animal Patient (Cont’d)

Clip area over the veinPrepare the area using an aseptic techniquePlace tape over the catheter hubHold off the vein, tense the skin, and position the catheter


Placing an IV Catheter in a Small Animal Patient (Cont’d)

Advance the catheterassembly through the skinAdvance it further to firmly seat in the vein

Advance the catheter over the end of the needleRemove the needleApply pressure


Placing an IV Catheter in a Small Animal

Attach T-port, cap, or set line to the catheter hubSecure the catheter with tape

Flush the catheter with salineTwist the tape into a “bow-tie”


Placing an IV Catheter in a Small Animal (Cont’d)

Crisscross the tape under and around the catheter hub

Apply ointment to plastic strip



Apply the plastic strip over the site of insertion

Secure the catheter with tape



Create a tension loop with tape


Giving an IV Injection Through an IV Administration Set Port

Prepare medication or induction agent Cleanse injection port with alcohol


Giving an IV Injection Through an IV Administration Set Port (Cont’d)

Insert the needle in the injection portPinch off the administration set line



Give medication at an appropriate rate



Release administration set line


Fluid Administration


Composition of Body Fluids

Water Intracellular (ICF) Extracellular (ECF)

• Vascular• Interstitial

Other elements (solutes)


Blood Volume

Plasma is 5% of body weight Blood volume

8-9% of body weight—dogs and large animals 6-7% of body weight—cats

Calculating blood volume Dogs and large animals = 90 mL/kg lean body

weight Cats = 60 mL/kg lean body weight


Solutes

Ions—small molecular weight and electrically charged Electrolytes

• Cations—positive charge• Anions—negative charge

colloids—large molecular weight plasma proteins

Small nonionic particles


Important Electrolytes

Cations Sodium (Na+) Potassium (K+) Magnesium (Mg2+) Calcium (Ca2+)

Anions Chloride (Cl−) Bicarbonate (HCO3

−) Phosphates (HPO4

2− and H2PO4

−) Proteins


Homeostasis

A constant state within the body created and maintained by normal physiologic processes

Water and solute movement Passive diffusion Active transport

Composition of fluid compartments varies normally ICF: K+, Mg2+, protein, and phosphate ECF: Na+, Cl−, HCO3

−


Principles of Water and Solute Balance

In any given compartment, positively and negatively charged particle numbers must be equal.

Solute concentration (osmolarity) in any fluid compartment must be 300 mOms/L.

Solutes must provide osmotic pressure to pull water into a compartment.

Small solutes (ions) pass freely into and out of the intravascular space from the interstitial space. Water follows to create equilibrium.


Principles of Water and Solute Balance (Cont’d)

One-third of IV fluids administered will stay in the intravascular space. Two-thirds will diffuse into the interstitial space. Colloids don’t pass freely through the vascular

endothelium. The presence of colloids in the intravascular space

draws water into the space creating osmotic or oncotic pressure.

Some solute concentrations (Ca2+, K+) must be kept within a narrow range to maintain normal heart and muscle function.


Fluid Loss and General Anesthesia

Dehydration, anorexia, general disease condition Depletes ECF Administer fluids with a solute profile similar to

ECF Perioperative hemorrhage

Loss from intravascular space Administer fluids with a solute profile similar to

ECF Administer hypertonic saline or colloid solutions


Fluid Loss and General Anesthesia (Cont’d)

Significant perioperative hemorrhage Loss of blood constituents, water, electrolytes Administer blood products

Low albumin Administer blood plasma or colloid solutions


Intravenous Fluids

Composition varies One or more electrolytes Dextrose Buffers Colloids

Classification Crystalloid Colloid


Crystalloid Intravenous Fluids

Water and small-molecular-weight solutes May contain dextrose and/or buffers Often used in anesthetized patients


Crystalloid Intravenous Fluids (Cont’d)

Isotonic, polyionic replacement solutions Similar to ECF Lactated Ringer’s solution (LR) Normosol-R (NR) Plasma-Lyte A and R (PA and PR) Isolyte S (IS) LR and PR contain calcium and cannot be

administered with blood products



Isotonic, polyionic maintenance solutions For use over a longer time Contain less sodium and chloride Contain more potassium Contain lower concentrations of buffer Contain dextrose Normosol-M in 5% dextrose (NM5) Plasma-Lyte 56 in 5% dextrose (PL5)



Normal saline (NS) Physiologic saline, 0.9% saline, or sodium chloride

0.9% Contains only sodium and chloride dissolved in

water Sometimes used instead of isotonic, polyionic

replacement crystalloid solution Used to bathe tissues during surgery Used to flush the IV catheter Used to flush body cavities



Hypertonic saline solutions 3%, 5%, 7%, or 23.4% solutions Administered with isotonic crystalloid fluids Used to treat acute shock



Dextrose solutions 5% dextrose in water (D5W) or 2.5% dextrose May be found in some maintenance polyionic

solutions Used to support blood sugar levels D5W is used to replace fluid loss due to

dehydration or heat stroke


Colloid Solutions

Contain large-molecular-weight solutes Used to support blood volumes and blood

pressure Synthetic colloid solutions

Hetastarch Stay primarily in intravascular space

Blood products Plasma and whole blood

Hemoglobin-based oxygen carriers Human or bovine hemoglobin No need for crossmatch


Fluid Selection

Healthy animal undergoing routine surgery Isotonic, polyionic, replacement fluids

Sick patients PCV =>20, TP =>3.5 g/dL Isotonic, polyionic replacement fluids


Administration Rate

During routine anesthesia and surgery 10 mL/kg/hr during the first hour 5 mL/kg/hr during remainder of the procedure


Fluid Administration Rate—Isotonic Crystalloids

Excessive hemorrhage or hypotension 40 mL/kg/hr (dogs and large animals) 20 mL/kg/hr (cats)

Shock 90 mL/kg/hr as rapidly as possibly (dogs and large

animals) 55 mL/kg/hr as rapidly as possible (cats)

Shock and blood loss (large and small animals) 7% hypertonic saline 3-4 mL/kg slowly over 5 minutes Followed by isotonic crystalloid solution


Fluid Administration Rate—Colloids

10-20 mL/kg/day (dogs and large animals) 5-10 mL/kg/day (cats)

Monitor to prevent overload, coagulation disorders, and allergies

Administer as a slow bolus Over 15-60 minutes (dogs and large animals) Over 30-60 minutes (cats)


Adverse Effects of Fluid Administration

Volume overload Pulmonary or cerebral edema Use slower infusion rate

Overhydration Ocular and nasal discharge Chemosis Subcutaneous edema Increased lung sounds Increased respiratory rate and dyspnea Coughing and restlessness if patient is awake Hemodilution


Fluid Administration

Infusion pump Tape scale to monitor rate


Fluid Administrations (Cont’d)

Burette for small-volume use


Definitions

Prescribed rate Infusion rate Delivery rate Drip rate Infusion time Infusion volume Conversion factors


Infusion Sets

Macrodrip set chamber (15 gtt/mL)

Microdrip set chamber (60 gtt/mL)


Fluid Administration Rate

Infusion rate Use patient weight and prescribed rate

Drip rate Use infusion rate, delivery rate, conversion factors


Preanesthetic/Preoperative Medications

Antibiotics Preemptive analgesia Antiemetics Anticonvulsants Antiinflammatory drugs

2. patient preparation

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