anesthetic equipment

Pull oxygen from air.  Less volume, for lower need only.

for large hospitals (humans) only

• tanks containing oxygen in the form of compressed gas.  E tank, G tank, H tank.  
• cylinders are green in US, white in Canada

• compressed oxygen cylinder
• 660 L
• attaches to anesthesia machine, small tank.  Store only on yoke, secure to specifically designed cart or chain to wall
• Securely attached so can't fall or roll

• compressed oxygen cylinder
• 5,531 L
• uncommon

• compressed oxygen cylinder
• 6,900 to 7,000 L (more than 10x E tank)
• connected directly or through drop line to anesthesia machine.

• attached to cylinder, indicates O2 pressure in tank when valve is open. 
• Full cylinder is 2,000 to 2,200 psi when full (in ANY tank)
• Gauge reads 0 when gas line bled off
• in the red when 500 or below, consider a new tank

• aka pressure reducing valve
• Reduces O2 pressure from 2,200 psi to 40-50 psi
• High pressure line going in, low pressure line coming out (STILL TOO HIGH FOR P)

• combustion (keep away from flame/spark/outlet--orthopedic drills are battery or pneumonic)
• Pressure without regulator can tear skin off
• if dropped and regulator falls off, becomes a missile.  SECURE ATTACHMENT

• E, G, H tanks, hold greater volume
• Blue in US and Canada
• Exists as both liquid and gas in tank, so pressure gauge only shows when tank close to empty
• Determined by weight, weigh to see how much you have left (8 kg full, 5.9 kg empty)

• green - Oxygen
• blue - Nitrous Oxide
• black - nitrogen
• grey - carbon dioxide
• yellow - air (black and white in Canada)

• opening a different size for each gas, only allows connetion to that particular line.
• Diameter-Indexed Safety System

Gas lines and outlets are color coded and have diameter specific to each gas.

• A - yoke (attaches cylinders to anesthesia machine)
• B - wing nut
• C - outlet valve
• D - outlet port
• E - pin index safety system holes
• F - nipple yoke
• G - pin index safety system pins
• H - nylon washer

• tank attached to anesthetic machine by yoke to pin index safety system
• different pins for each type of gas, must match holes in cylinder outlet
• Like DISS

• sets gas rate in liters per minute delivered to patient (0-4L/min)
• Reduces pressure from 45-50 to 15 psi, safe for P, carries iso/sevo to P
• gas enters at bottom and exits at top
• read at center of ball or top of other float
• needle valve

• relatively rapid, precise adjustment of anesthetic depth
• intubation ensures P airway
• continuous O2 supply
• can continue longer (most IV cannot be given repeatedly)

• part of anesthesia machine that vaporizes liquid anesthetic and mixes with O2 for delivery to lungs
• vaporizer SPECIFIC to particular anesthetic agent

• yellow - sevoflurane
• purple - isoflurane
• blue - desflurane (mostly human, delicate vaporizer)
• red - halothane (rarely used)

• a measure of the amount of liquid anesthetic that will evaporate at 20 degrees C/68 degrees F.  
• higher vapor pressure = more O2 gets saturated = more anesthetic gas to P.
• iso, sevo and halothane have high vapor pressures, need precision vaporizers

•  
• 33% vapor pressure, A is 33% iso, MUST mix with O2 and dilute.

• very expensive electronic, heated vaporizer.  Rare in veterinary medicine.  Temperature and humidity control required.

• iso at 20C 33%
• iso at 24C 38%
• sevo at 20C 21%
• sevo at 24C 24%
• desflurane at 20C 87%
• halo at 20C 32%
• halo at 24C 38%

• lower anesthetic solubility in blood = easier saturated with anesthetic molecules = faster in and out.  
• Low solubility = faster in and out

• lower anesthetic solubility in blood = easier saturated with anesthetic molecules = faster in and out.  
• Low solubility = faster in and out
• Nitrous is fastest

inhalational agent solubility (blood:gas solubility coefficient)

• halothane: 2.4 (slowest)
• isoflurane: 1.4
• sevoflurane: 0.7
• nitrous oxide: 0.47 (fastest)

• convert volatile liquid anesthetic to gas, exactly calibrated for each type of gas (halo, iso, sevo)
• must have indicator windo to tell how much anesthetic is inside.  Clean before refilling

increased concentration of anesthetic gas, spills into diluent space

key and funnel.  Key is newer, minimizes contamination into atmosphere

must be drained, every 6 months, to remove thymol preservative residue

where gas comes out of vaporizer (where we change systems)

where fresh gas enters breathing circuit

• connects inspiratory hose to machine
• Allows gas to flow only to patient

• connects expiratory hose to machine
• Prevents expired gas from returning to patient before passing through CO2 absorbant

• between regulator and flow meter, so delivers oxygen at 30-60 L/min.  1 L of O2 glows into breathing circuit for every second that the button is held down.  
• For flushing anesthetic gas out of system.  NEVER when patient is connected

• aka adjustable pressure limiting valve or pressure release valve
• controls amount of gas ventilated into scavenger system
• PREVENTS BUILD UP OF PRESSURE.  Can rupture alveoli, animal can't breathe out.  For PPV.  MUST BE OPEN when animal is connected.
• High pressure alarms at 20cm H2O

• aka reservoir bag
• Fills as gas enters circuit, deflates on inspiration
• allows observation of repiration depth and frequency. 3/4 full
• allows manual ventilation
• capacity 6 times tidal volume (min 60mL/kg)

• volume of air inspired in normal quiet inspiration.  Should be equal to amount breathed out.  
• 10-15ml/kg

• 6 x tidal volume (10-15mL/kg), 60mL/kg MIN
• 6 x (20kg x 60mL/kg) = 1800mL ~ 2000mL ~ 2L

• contains soda lime granules
• exothermic reaction generates heat and water (should be warm if working). Change when blue/not crumbly after 6-12h of use, clean trap weekly.

• 1. granules hard, not crumbly
• 2. not warm when in use
• 3. turn violet or blue (temporary)
• 4. capnography

• linear flow - flows from top to bottom or bottom to top. Some take prefilled canisters
• reverse soda lime canisters - gas enters and leaves from top.  Baffle/tube in center must be covered. Doesn't take prefilled canisters

• measures gas pressure in breathing circuit = pressure in P's lungs.  
• measured in cmH2O or mmH2O.  
• SHOULD BE AT 0cm H2O when breathing spontaneously.  Pressure may be closed popoff valve or too high O2 rate (NOT ET TUBE)

• old fashioned, dangerous.

• 1. Closed (total rebreathing) - popoff valve closed
• 2. semi-closed (partial rebreathing system) - MOST COMMON for >7kg
• 3. semi-open (nonrebreathing system) - MOST COMMON for <7kg
• 4. open system - mask or chamber induction

patient rebreathes expired air with CO2 removed and fresh gas continuously added

• bad idea.
• pop-off valve kept closed
• recirculates all expired gas except CO2
• FRESH O2 MUST EQUAL O2 CONSUMPTION
• helps save heat/humidity

• partial rebreathing system, most common for P >7kg (smaller P can't open valve, weight drags on ET tube)
• Fresh gas and O2, exceed metabolic need, helps preserve heat/moisture
• pop-off open
• some dilution from expired air

• non-rebreathing system, bypasses flutter valves, monometer, CO2 absorber, rebreathing bag.  
• HIGH O2 FLOW RATE TO PREVENT REBREATHING (2-3 x minute ventilation), no dilution
• patients <7kg
• Fresh gas straight from vaporizer to to animal

• tidal volume x respiratory rate
• non-rebreathing system runs O2 at 2-3 times minute ventilation (500-1000 ml/kg/min)

• decreased resistance to breathing compared with rebreathers
• decreased dead space
• decreased drag on ET tube
• more immediate response to changes in vaporizer settings (rebreathers slower due to dilution)

• potential for rebreathing CO2 if rate is too low
• loss of heat and water from patient
• increased atmospheric pollution in scavenger inadequate

• Bickford
• Bain (fresh gas inhalation inside exhalation tube for heat retention)
• Ayers
• Mapleson (Magill)
• T-piece

• removes waste anesthetic gasses from breathing circuit, decreases environmental contamination
• active or passive systems
• waste gas vented outdoors, check daily.

• fan or vacuum pump draws waste gas into scavenger
• turn on daily
• suction can't be too strong, draws gasses from breathing circuit

• positive pressure of waste gas in breathing circuit drives gas into scavenger
• f/air canister (activated charcoal canister)

• F/air-type filters.  Passive scavenger system.
• positive pressure of waste gasses in breathing circuit pushing through canister
• 12-15 hours of use or weight gain of 50 grams. Some seem to leak 5ppm before.
• inefficient higher than 2L/min
• NOT FOR NITROUS OXIDE
• can't let holes in bottom get blocked

• No worker should be exposed to more than 2ppm on a time-weighted average
• Once you can smell iso it's probably at 33ppm

Waste anesthetic gas exposure badges.

where there is high pressure: between tank and flowmeter, DISS connectors on central lines, yoke connections, pressure regulators or pressure gauges.

• flowmeter at 0, turn on gas tank, note tank pressure reading.  Turn tank off.  After one hour, tank pressure should not have changed.  
• Can spray 10% detergent on connections and look for bubbles

• in rebreathing systems, between flowmeter and patient. 
• Close pop-off valve, occlude Y-piece with thumb, turn on flowmeter to 0.2L/min, fill reservoir bag with flush to 30 cmH2O, turn off, should not decrease more than 5 cmH2O in 10 sec.  open pop-off
• LEAKS OF 0.2 L/MIN OKAY

Occlude end, set O2 at 1-2 L/min, float in flowmeter should fall.

• open system
• used for feral or vicious
• 2 ports, fresh gas source and waste gas exit

• no airway control, can hold breath, can't tell when CO2 levels increase.
• Not for C-section
• increased dead space, no control over gas concentration
• struggling and stress
• prolonged stage II, increased catecholamine release
• increased risk regurg/vom and aspiration
• increased risk to staff
• iso: 8-9 min induction.  sevo: dogs 6 min, cats 7 min

mechanical and physiological

• reduces anatomical dead space
• reduces exposure to OR staff of waste gas
• decrease risk of aspiration
• maintains airway
• allows assisted or controlled ventilation

• murphy - has "eye"
• magill - no "eye"
• Cole - no eye, exotics, straight
• red rubber tube

• A. valve with syringe attached
• B. Pilot balloon
• C. Patient end
• D. Connector
• E. Tie
• F. Measurement of length from patient end in cm
• G. Measurement of internal diameter in mm
• H. Inflated cuff
• I. patient end
• J. Murphy eye

• Miller - straight
• McIntosh - curved

• tip in cervical trachea near thoracic inlet
• connector end as close to incisors as possible

• Excessively long ET tube
• narrow diameter ET tube

• overinflation or overly aggressive intubation can cause inflammation, pressure necrosis or tracheal rupture
• rough intubation causes vagal stimulation (bradycardia), damage recurrent laryngeal nerve (laryngeal paralysis), laryngospasm in cats
• traumatize soft palate, pharynx or larynx

• when swallowing reflex returns
• keep in as long as possible in brachycephalic
• monitor for chewing

• allows adjustment of anesthetic depth
• rapid recovery
• intubation ensures airway
• control of O2
• longer term - most IV can only be given once

• minimum alveolar concentration
• standard measure of potency
• percentage of anesthetic gas in mix with O2--no movement in response to painful stimulus in 50% of animals tested
• automotive, hormonal and nocioceptive response still active (EPI, NOREPI, PAIN, CORTISOL)

administration of smaller amounts of different drugs to provide unconsciousness, no movement, no autonomic, hormonal or nocioceptive response

• sevo dog: 2.36   cat 2.58
• iso dog: 1.2-1.3   cat 1.6
• halo dog: 0.87   cat 1.14

• Light anesthesia: 1 x MAC₅₀
• surgical anesthesia: 1.5 x MAC₅₀
• deep anesthesia: 2 x MAC₅₀

• young age
• hyperthermia
• hyperthyroidism 

increase metabolism, need more inhalant

• drugs that depress CNS (why we give induction drugs)
• old age
• hypothermia
• pregnancy (breathe faster)

• no vaporizer necessary
• can't produce MAC50 with nitrous alone
• risk of hypoxia (need at least 33% O2/>300mL/min - 1/3 O2)
• 5-10 min O2 after to avoid diffusion hypoxia
• diffuses into air pockets (like GDV, sinuses, anything blocked)

• intestinal obstruction
• GDV
• surgery into hollow organs
• pneumothorax
• blocked nasal sinuses
• diaphragmatic hernia
• Nitrous diffuses into air pockets in the body, causing distension

• vasodilation
• doesn't sensitize heart to catecholamines
• dose-dependant respiratory depression (pungent and irritating to airways)
• good muscle relaxation
• >99% excreted unchanged by lungs (good for liver-compromised)

• slightly faster induction, recovery, response to changes in vaporizer than iso (lower blood:gas solubility coefficient)
• dose-dependant respiratory depression
• doesn't sensitize heart to catecholamines
• not pungent or irritating to airway
• emergence phenomena in cats
• nephrotoxic metabolites (SODA LIME MUST BE FRESH, min O2 rate of 1L/min)

• facilitates mechanical ventilation in small animals
• complete skeletal muscle relaxation (flaccid paralysis)
• depolarizing agents: succinylcholine (no reversal)
• non-depolarizing agents: pancuronium, vercuronium (reversed with anticholinesterase like edrophonium)
• complete skeletal muscle paralysis (requirement for mechanical ventilation, respiratory arrest)
• no anesthesia or analgesia--WATCH FOR PAIN

• dilute detergent
• tracheal mucosal injury, esp in cats, caused by glutaraldehyde, ethylene oxide, chlorhexidine, (para)formaldehyde, trigene

• failure to rinse detergent or clean tube
• lubricating ointment
• movement within airway
• twisting tube around