- blunt questions to check drugs/allergies/etc.

- mark ANY and ALL reactions/interactions with drugs (good or bad) for future reference

double check !

- compressed gas (cylinders)

- liquid  oxygen (tanks)

- oxygen generator (concentrator)

come in different sizes

• rebreathing - recycled air/cleaned = circle system (large animals)
• non rebreathing - new air at all times (smaller animals)

gives patient a breath manually

based on size of animal

= 6x tidal volume

(tidal volume = 5-7ml/lb)

30ml/lb

in circle systems- area within a circuit that is not flowing and the animal keeps rebreathing (in the Y)

circuit MUST be the correct size for patient

GOOD when crushable in fingers

watch for exothermic reaction (heat) and for it to turn purple upon usage

relieves pressure during breathing

air must have a place to go

closed = met oxygen requirements are met exactly

semi closed = above met requirements so it MUST remain open during breathing

ensures there wont be any unnecessary pressure exerted onto the lungs

high flow rate of oxygen forces the carbon dioxide out of the circuit to avoid the animal rebreathing

BLUE TANK

in a liquid state when it's in the tank

must be weighed to determine how full the tank is

mean arterial pressure

drives blood (perfusion)

maintain > 60 mmHg during anesthesia

manual - doppler method

automated - oscillometric method

width = 40% limb circumference

narrow?= artificially elevates value

wide? = artificially lowers values

cat= above elbow (if possible) medial side

dog = distal forelimb or rearlimb

equine = tail

ruminant = tail or distal limb

invasive - requires arterial catheter

1. mechanical movement converted to electrical via transducer - read with occilliscope

2. pulsations read with aneroid manometer

monitoring

ventilation

observation: thoracic wall movement, breathing bag movement

auditory: "honker", esophageal stethoscope

carbon dioxide: blood gas, capnography

rate, rhythm, nature, effort

rate: varies widely, look for sudden changes

tachypnea= too light/too deep, drug induced, obese/geriatric, hypoxia, hyperthermic

bradypnea or apnea= CNS depression (too deep?), opioids, barbiturates, propofol, after neuro procedures

monitoring

ventilation - auditory

"honker" = thermistor measures changes in air temperature

esophageal stethoscope

monitoring

ventilation - carbon dioxide

arterial blood gas analysis = invasive

end expired analysis = capnography (non-invasive)

instrument measures end tidal carbon dioxide providing estimate of arterial carbon dioxide partial pressure

normal = 40-45mmHg

increased? = hypoventilation,overproduction, rebreathing

decreased?= hyperventilation, cardiac arrest

clinical uses of capnography

• monitoring respiration and ventilation - apnea alarm
• verifying tracheal intubation
• monitoring for rebreathing of carbon dioxide - added dead space, faulty inspiratory/expiratory valves in circle, used up CO2 absorber
• prediction of survival from cardiac arrest 

types = mainstream & sidestream

monitoring

oxygenation

three methods

mucous membrane color (non  invasive)

arterial blood gas analysis (invasive)

pulse oximetry (non invasive)

• adequate blood oxygen - dissolved (partial pressure measured in mmHg), bound to hemoglobin (saturation measured in %)
• adequate hemoglobin content
• adequate peripheral perfusion

MM color/ blood = red --> blueish

occurs when unsaturated HgB exceeds 5g/100mls

unreliable - anemia, bad lighting, skin pigment

arterial blood gas analysis

info?

• acid base
• oxygenation - hemoglobin saturation, oxygen partial pressure
• ventilation - carbon dioxide partial pressure

instrument that provides a continuous estimate of the percent of hemoglobin saturated with oxygen

also:

pulse rate, pulse rhythm/audible changes, cardiac output

interference? motion, low perfusion, optical interference (external light, anemia, carbon monoxide, methemoglobin, intravascular dyes (methylene blue)

monitoring

other things?

adequacy of anesthesia

temperature

blood loss

monitoring

depth of anesthesia

• CNS activity (EEG)
• muscle relaxation (jaw tone)
• response to stimuli - pedal reflex, towel clamps, tail pinch
• sympathetic responses, HR, BP, RR
• eye positions/activity - eyes rotated ventral-medial, dull palpebral reflex, HORSES - nystagmus and tearing indicates plane of anesthesia

montitoring

blood loss

subjective - inaccurate, can't see it all, one 4x4 swab contain 10 mls of blood

objective - weigh swabs, measure volume in suction bottles, etc

monitoring

temperature

core - esophageal, middle ear

periphery - rectal, nasal

hypothermia

• increased cardiac irritability- bradycardia, spontaneous fibrillation
• hypoventilation
• increased blood viscosity
• decreased anesthetic requirements
• decreased metabolism - delayed recovery
• shivering in recovery - increased oxygen requirements

prevents attachment of incorrect gas cylinder

called pressure regulator, tank pressure gauge

measured in PSI

needs to be specific pressure = 50 lbs sq inch

• measures gas flow in mls or liters / minute to vaproizer
• color coded - GREEN = oxygen
• oxygen goes through graduated glass cylinder w/ floater or bobbin
• oxygen flows should meet or exceed metabolic requirement

• allows oxygen to by-pass the flow meter and vaporizer
• delivers PURE oxygen to the breathing circuit
• flow rate = 35-75 liters/minute

oxygen + vaporized anesthetic = fresh gas

the fresh gas line is attached to a breathing circuit at the fresh gas inlet

rebreathing - circle system

non rebreathing - bain circuit

classifications

• open - no rebreathing of gases
• closed - allows rebreathing of gases
• semi open - variation of an open system
• semi closed - variation of a closed system

inhalation/exhalation

also called flutter valves

keep gas flow going in a circle

prevents animal from rebreating

moisture may cause them to stick

breathing circuits

sizes

adult size = > 20lbs

pediatric size = between 6-20 lbs

dead space begins at the "Y"

• also called pressure gauge
• measures pressure withing breathing system
• used to help determine how big of a tidal volume to deliver to patient
• measure in cm H2O

pressure relief valve

normally OPEN - high oxygen flow rates

avoids barotrauma

• aids warming and humidification of the inspried gases
• increase in respiratory resistance to breathing - usually used on patients >20 lbs
• identical function to a conventional circle

circle system

CLOSED

• very low oxygen flow rate = metabolic
• all exhaled gases rebreathed
• all exhaled gases pass through soda sorb
• metabolic oxygen requirements replaces on min by min basis
• pop off valve may be CLOSED
• may need to increase % of inhalant delivered

circle system

CLOSED

advantages vs disadvantages

Advantages

more economical, less pollution, conserves heat and humidity, do not have to continually open and close the pop-off valve to give the animal a breath

Disadvantages

Hypoxia - watch the reservoir bag size to determine if administering enough oxygen

takes longer to change anesthetic concentration in circle

circle system

SEMI CLOSED

• lIndicates that the oxygen flow rate is greater than the metabolic requirement
• lSome of the exhaled gases are rebreathed and some exit the circle via the pop-off valve
• lIf the oxygen flow rate is close to the metabolic requirement it may be called  “low-flow” anesthesia

circle system

SEMI CLOSED

advantages vs disadvantages

advantages

economy of anestetic consumption, warming and humidification of the inspired gases, reduced atmospheric pollution (esp. closed-system)

disadvantages

slow changes in the inspired anesthetic concentration with low flows or a closed system

cannot be used on very small patients

circle system

testing the circuit

1. close pop off valve
2. occlude the Y-piece with your thumb
3. depress the oxygen flush valve until a pressure of 20 cm H2O is reached in the circuit
4. observe the manometer for a decrease in pressure which indicates a leak

a tube carrying fresh gas travels an outer resevoir tube to the endotracheal tube connector

• inspiration - patient recieves fresh gas from outer reservoir tube
• expiration - patient expires into reservoir tube, fresh gas is still flwoing so it is contaminated by expired gas
• expiratory pause - fresh gas from inner tube washes expired gas out of the resercoir tube filling it with fresh gas for next inspriation

bain circuit

technicalities

use oxygen flow rate of 100 ml/lb

which allows from rebreathing - eliminating ALL would require rate of 3 times minute ventilation

MV = RR X TV

used with patients <5-6 lbs

decreased dead space

decreased resistance to breathing

bain

advantages vs disadvantages

advantages

compact and inexpensive

low dead space

low resistance

facilitates scavenging of waste gases (vs mask only)

disadvantages

uses more oxygen and inhalation asthetic per lb of patient

loss of humidity = cold patient

loss of heat = cold patient

cannot use oxygen flush valves = lung barotrauma

bain

testing the circuit

scavenged from the pop-off valve

active = suction causes waste to enter the scavenger

passive = positive pressure of waste gas pushes gas into scavenger

gases pass to hole in wall and outside atmostphere, F/air canister (activated charcoal), surgiVet pure-guard (activated charcoal)

 flow of gases and fluids

laminar

flow of gases and fluids

turbulent

intubation

diameter and lengths

halving the radius reduces flow by a factor of 16

doubling the length reduces the flow by 1/2