Pre-Anesthetic and Fluid Therapy

patient assessment includes

signalment, history, physical exam, diagnostics, and ASA status

Signalment includes

species, breed, sex, age, and reproductive status

* health and vaccination status
* current medication
* recent issues (reason for anesthetizing patient)
* previous anesthesia history (complications and reactions)

history

* body weight and condition
* mentation/temperament
* temperature
* hydration status
* heart rate, rhythm, pulse
* respiratory rate and character
* mucous membranes
* capillary refill time

physical exam

drug calculations have their dose written as

mg/kg or mcg/kg

drug calculations for obese patients are based ideally on

ideal lean body weight

emaciated patients are prone to

hypothermia and sensitivity to effects of some anesthetics

level of consciousness - how well a patient responds to stimulus or how easily it can be aroused

mentation and temperament

consciousness of healthy patients is described as

alert and responsive (BAR or QAR)

patients with mildly decreased LOC, can be aroused with minimal difficulty

lethargic

depressed and cannot be fully aroused

obtunded

sleeplike state, only aroused by painful stimuli

stuporous

cannot be aroused, unresponsible to all stimuli including pain

comatose

temperaments

anxious, excited, aggressive, calm, alert

temperature range

99-102.5

these cause hyperthermia

illness, heatstroke, and stress

these cause hypothermia

illness, age, and body condition

perform skin tent

above the eye or caudal neck

0-5% dehydration

2-3 sec skin tent, slightly tacky mm, 2-3 sec CRT

5-8% dehydration

5-10 sec skin tent, dry mm, 2-3 sec CRT

8-10% dehydration

10-30 sec skin tent, dry mm, >3 sec CRT

10-12% dehydration

shock, death probable

12-15% dehydration

things to consider with skin tenting

breed, emaciated, and obese

pulse for dogs

50-180 bpm

pulse for cats

110-240 bpm

common locations for pulse

femoral and pedal (metatarsal and metacarpal)

when the heart rate is higher than actual palpable pulse

pulse deficit

swooshing sound of blood flowing backward through valve

murmurs

extra sounds (beats) other than Lub Dub

gallop rhythm

respiratory for dog and cat

15-30

when auscultating lungs

listen to all 4 quadrants of each lung

pleural space disease or space occupying lesion

absence of sound

fluid in lungs

crackles

small airway diseases

wheezes

large airway disease

loud breathing

extrathroacic

inspiration noise

intrathoracic

expiration noise

* reflects blood perfusion of peripheral tissue
* rough estimate of cardiovascular function
*

CRT

minimum database for diagnostics

BUN, glucose, PCV, TP

hematocrit and platelet count

CBC

plasma proteins, electrolytes, BUN, creatinine, glucose, ALT, and ALK

serum chemistry

BMBT

blood mucosal bleeding time

other diagnostics

coagulation profile, urinalysis, blood gas, and diagnostic imaging

American Society of Anesthesiologists status is a scale that describes

patient’s anesthetic risk

ASA I (elective procedures)

minimal risk

ASA II (mild systemic disease)

slight risk

ASA III (moderate systemic disease with compensation; mild clinical signs)

moderate risk

ASA IV (systemic disease without compensation and treatment needed to survive)

high risk

ASA V (will not survive with or without surgery)

extreme risk

how much of patient’s body weight is water?

60%

how much of the body weight water is intracellular and how much is extracellular?

intra - 40% and extra - 20%

blood volume for dogs and large animals

80-90 ml/kg

blood volume for cats

40-60 ml/kg

most important solutes in fluid therapy

ions (cations and anions), colloids, and small nonionic particles

small molecular weight, electrically charged particles

ions

positively charged ions (Na, K, Mg, and Ca)

cations

negatively charged ions (Cl, HCO3, phosphates, and proteins)

anions

large molecular weight plasma proteins

colloids

nonionic particles

glucose and small proteins

constant state within the body created and maintained by normal physiological processes

hemeostasis

number of negatively and positively charged particles must be equal

electroneutrality

solute concentration of 300 mosm/L is maintained in all body fluids

osmolarity

solutes in each fluid compartment provide the osmotic pressure

osmotic pressure

diffuse freely through vascular endothelium and take fluid with them

small particle solutes

presence provides colloid osmotic pressure (oncotic pressure)

colloids

concentration of certain solutes (K and Ca) must be kept within a narrow range

plasma concentration

components of extracellular fluid

Na, Cl, HCO3

components of intracellular fluid

K, Mg, proteins, and phosphates

intravascular component

albumin

intracellular component

K

* contain water and small molecular weight solutes
* routinely used in anesthetized patients

crystalloid solutions

5 crystalloid solutions

* isotonic, polyionic replacement solutions
* isotonic, polyionic maintenance solutions
* normal saline solution
* hypertonic saline solutions
* dextrose solutions

* reflects the solute composition of ECF
* contain buffers
* plasma-lyte A, plasma-lyte 148, and normosol-R contain magnesium
* lactated ringers solution contains calcium

isotonic, polyionic replacement solutions

* for maintenance therapy over long periods of time
* reflects the solute composition of total body water
* contain lower concentrations of buffer
* contain dextrose
* contain less Na and Cl
* contain more K

isotonic, polyionic maintenance solutions

* physiologic saline, 0.9% NaCl
* contains only Na and Cl (unbalanced replacement solution)
* used with blood transfusions
* doesn’t contain K

normal saline solution

* 3% NaCl, 7% NaCl
* rapidly, temporarily draws water into intravascular space
* hypovolemic, traumatic, endotoxic shock
* profound hemorrhage

hypertonic saline solutions

* 50% dextrose
* use for: neonatal, hypoglycemic, debilitated patients, diabetes mellitus, and hyperkalemia therapy

dextrose solutions

isotonic crystalloid administration rate for dogs and large animals

5 ml/kg/hr

isotonic crystalloid administration rate for cats and horses

3 ml/kg/hr

how much of bolus doses of crystalloids can be administered at 3 or 5 ml/kg/hr?

1 to 2

what should you consider if a patient’s hypotension is not responding?

colloids

how much of shock bolus is used for dogs and large animals?

80-90 ml/kg

how much shock bolus is used for cats and horses?

40-60 ml/kg

how much of the first ml/kg of shock bolus is given rapidly before reassessing your patient?

10-20

when to use hypertonic saline administration rate

shock and blood loss or when blood volume expansion is necessary

hypertonic saline administration rate for dogs and large animals

4-5 ml/kg

hypertonic saline administration rate for cats and horses

2-4 ml/kg

over how long of a time period do we administer hypertonic saline boluses?

5 minute period

* contain large molecular weight solutes
* don’t diffuse freely across vascular endothelium (stay in intravascular space)
* supports expansion of blood volume and blood pressure
* used with plasma protein less than 3.4 g/dl

colloid solutions

two types of colloids

synthetic and blood products

* contain large molecular weight solutes
* hetastarch, dextran, pentastarch, or gelatin products
* hetastarch most commonly used
* vetstarch is labeled for vet med
* used for cases of shock, hypotension, or blood loss

synthetic colloid solutions

how much of synthetic colloid will remain in the plasma 24 hours after administration?

30-60%

* used in cases of anemia, hypoproteinemia, coagulation disorders, thrombocytopenia

blood products

* support oxygen carrying capabilities
* used with profound blood loss

whole blood and packed RBCs

* supports expansion of blood volume
* treats hypoproteinemia

plasma

colloid administration rate for dogs and large animals

10-20 ml/kg/day (5ml/kg bolus)

colloid administration rate for cats and horses

5-10 ml/kg/day (3 ml/kg bolus)

CRI rate

1-2 ml/kg/hr

cautions with colloid administration

volume, coagulation disorders, allergic reactions, and nausea/vomiting