Anaesthesia Delivery

Innovating Excellence in Anaesthesia

Darvall Anaesthesia Delivery Equipment

Veterinary anaesthesia has changed in many ways over the last 30 years. In the past, safety of the patient was measured by survival; keeping the subject asleep and immobile was the priority. The physiological well-being of the patient, particularly pain management, has gained prominence.

Today, the environmental impact and sustainability of anaesthetic activities, along with the safety and welfare of the entire veterinary team are primary.

Darvall has 30 years expertise and experience innovating and manufacturing high quality, versatile anaesthesia equipment designed for a systematic approach to deliver reliable and safe anaesthesia for all applications from rodents to small animals, exotics and for zoo or field use. Machines are reliable, simple to operate, feature modular components that are easily serviced or replaced by end users. Darvall’s equipment facilitates a standardised approach to anaesthesia that optimises patient safety and staff capability, confidence and training.

Only Darvall’s Stinger Ultra solution delivers predictable low-flow anaesthesia for all animals from 2kg-80kg (4lb-175lb), reducing consumption of oxygen, inhalant agents and other consumable by up to 90%, reducing heat loss compared to high flow non-rebreathing circuits while cutting environmental emissions

Today, the environmental impact and sustainability of anaesthetic activities, along with the safety and welfare of the entire veterinary team are primary.

Reduce consumption and environmental emissions

Low flow anaesthesia down to 200ml/minute is environmentally and economically efficient:

One tenth of oxygen and inhalant agent consumption compared to high-flow, non-rebreathing systems

Reduced outflow of inhalant agents by up to 90% from the pop-off valve cuts environmental emissions and enhances team safety

Removes the need for inefficient, expensive high volume oxygen concentrators that are harmful to the environment

Overall Darvall delivers significant gains in environmental and economic efficiencies.

Traditional veterinary anaesthetic techniques in our smallest patients have utilised relatively high fresh gas flow rates, well above the metabolic requirements of patients. This is highly wasteful of oxygen and inhalational anaesthetic agents, which in turn is unnecessarily costly, exposes the veterinary team to risk, and is environmentally damaging. Low flow anaesthesia and the resultant benefits are established concepts. However, care must be taken not to jeopardise patient safety in seeking environmental benefits.

Key equipment requirements for low-flow anaesthesia are:

  • A vaporiser calibrated and tested at low flows ideally down to 200 ml/min. for precise output
  • An Oxygen flowmeter with accurate low flow delivery and a visual scale that can easily be read down to 100ml/min. This half the typical minimum oxygen flow (200ml/min) ensuring reliable delivery
  • A low volume, low resistance circle absorber and with rapid response to vaporiser changes (in a few breaths) and no rebreathing of CO2 which can be used on all patients down to 2kg (4lb), permitting fresh gas flows up to 10 times lower than high flow non-rebreathing systems
  • Small volume, low resistance breathing hoses that support rapid response to vaporiser changes
  • Some breathing hoses can be heated to warm inspired gas from the moment of intubation to maximise warming efficiency and maintain humidification of inspired gas as water vapor rains out below 32o
  • A minimal dead space Y-piece (1.5ml) permits use of circle rebreathing systems and Lack non-rebreathing circuits in animals down to 2kg (4lb) with 10-15ml tidal volumes because total dead space (anatomic 30% VT + machine 1.5ml) remains less than 50% (= 5ml/kg) of that tidal volume (VT)
  • Preferably a fail-safe APL valve with high pressure release at 25-30 cm H20 when fully closed
  • An End-Tidal CO2 monitoring system that does not remove gas from the breathing system or else can return the sampled gas to the breathing system – essential for low-flow applications.
  • For Active Waste Gas Systems, an airbrake that prevents negative pressure developing at the waste gas spill valve of the breathing system, which would otherwise suck gas from the low-flow breathing system.

All these requirements overcome the major problems of using low-flow anaesthesia on animals under 10kg (22lb) so in 5 to 10 minutes (IV induction “wake-up” time) predictable, stable anaesthesia can be achieved.

The Stinger Anaesthesia Range

Darvall’s Stinger Ultra system delivers confident, safe and predictable low-flow anaesthesia.

  • The complete Low-Flow anaesthesia solution.
  • One-stop rebreathing system solution for all animals from 2kg-80kg (4lb-175lb)
  • Darvall’s modular components focus on reliability and patient safety.
  • Standardised and simplified for anaesthetic team training, operation & confidence.
  • Future-proof integrated low-flow anaesthesia.
  • Reduces environmental WAG emissions by up to 90%, particularly for animals under 15kg (35lb).
  • Minimises staff exposure, optimising operator safety.
  • Helps solve hypothermia by delivering warm, humidified gas.
  • Stinger Ultra pays for itself in consumable savings in less than 2 years.

Other models in the Stinger range:

Stinger Deluxe

  • Standard circle rebreathing anaesthesia system using the SafeAbsorb for all animals from 7kg-80kg (15lb-175lb).
  • For animals under 7kg (15lb). use high flow non-rebreathing anaesthesia.

Stinger Streamline

  • Simple machine for small animals, birds, reptiles & exotics all under 10kg (20lb) using high flow non-rebreathing circuits.

Stinger Backpack

  • Rugged & reliable field anaesthesia with a utility “Stinger Deluxe” model.
  • Mounted in a waterproof Pelican case and can be mounted on a backpack frame.

 

See also Anaesthesia for Exotics & Research for information on Stinger machines for biomedical research.

All Stinger machines can be configured to be mobile mounted on a wheel base that can also hold an oxygen tank, or fixed as a Table Top model for trolleys, benches and shelves. A Stinger Table Top with DVM vaporiser weighs 15kg (33lb). It can be wall mounted on a scissor action swing.

Key components of the Darvall Stinger low-flow anaesthesia machine range

DVM low flow vaporisers

Unique, highly accurate and reliable at very low gas flows down to 200ml/minute. Facilitates cost effective, environmentally responsible anaesthesia, even for very small patients. (Twice as accurate at 2.5 times lower minimum flow than all current human anaesthesia vaporisers.)

Precision expanded scale flowmeter

Precise, oxygen flowmeter with an expanded 0 – 1L O2 per minute scale that can be easily read at fresh gas flow rates down to 100ml/minute for accurate low flow delivery. Has a fluorescing back panel in case of low room lighting

Stingray Absorber

Low-volume, low-resistance circle absorber for all animals from 2kg- 80kg (4lb-175lb) that prevents rebreathing of CO2 and is responsive to vaporiser changes in 5-10 breaths even at low fresh gas flows. CO2 rebreathing is prevented by one-way inspiratory/expiratory valves that close with minimum force. Stable anaesthesia is rapidly achieved in 5 to 10 breaths by the innovative gas accumulator in the Stingray base, a large reservoir holding a high concentration of fresh gas from the vaporiser.

Smooth-wall tubing

Low resistance, smooth-wall tubes reduce volume by up to 70% compared to standard 22mm (7/8”) corrugated hoses to ensure faster circle system response to vaporiser dial change at very economical low gas flows.

Cozy Heated smooth-wall circuits are optional providing warming from the first breath after intubation.

Fail safe Adjustable Pressure-Limiting (APL) “Pop-Off” or “Spill” valve

Safety APL “spill valve” has high pressure release at 30 cm H2O in the fully closed position to prevent barotrauma in case the valve is inadvertently closed – a common problem in anaesthesia.

Darvall’s new minimum dead space, low resistance Y-piece

Reduces dead space to under 1.5ml compared to 7ml to 15ml for human paediatric or adult Y pieces respectively. Ergonomic design eliminates need for elbow adapters which typically have 10 ml dead space.

Vaporisers

The Darvall DVM Isoflurane Vaporiser is at the heart of our offering. Darvall has been in the vaporizer business for 25 years, servicing and remanufacturing over 12,000 vaporisers in Sydney since 1996 for human and veterinary use. Darvall’s engineers commenced design of the Darvall DVM isoflurane vaporizer in 2013; its innovations are recognised by granted international patents.

 

The primary design objective was to manufacture vaporisers with high accuracy and reliability at very low gas flows, down to 200ml/minute (1/3 less than the lowest gas flow of standard human vaporisers) , meeting the needs of very small patients so enabling delivery of cost effective and environmentally responsible low-flow anaesthesia. Manufactured in Sydney, over 1000 DVM’s are in clinical use.

Darvall’s new DVM Sevoflurane vaporiser has been developed with the same specifications and tolerance, making it an industry leader in veterinary and human anaesthesia for accurate, predictable low-flow sevoflurane anaesthesia and reliable performance with a long service interval.

Highest accuracy at lowest gas flows and virtually maintenance free 10-year service interval for efficiency.

Choice of:

  • Anaesthetic agent – Isoflurane or Sevoflurane.
  • Mounting system – Selectatec or Cage mount.
  • Filling system – Key-fill with on/off valve or pour fill.

Key Features of Darvall DVM Low-Flow Vaporisers

  • Minimum operating gas flow is 200ml/min, which is 2.5x lower than all other vaporisers, reducing waste anaesthetic gas emissions and costs; for superior environmental sustainability.
  • Ergonomic, top-mount, precision movement dial with a vertical calibration scale with large white-on -black numbers clearly visible from 2 metres (6’).
  • Innovative, integrated, valved fill port block for quick, simple and safe filling.
  • Vertical fluid gauge incorporated into the front of the fill port block is easy to see with clear markings, to avoid “running on empty”.
  • Large capacity sump holds 250mL (one bottle) of isoflurane, reducing need to refill during surgery, refill frequency and potential spillage.
  • Advanced aerospace engineering, excellence in build, calibration, and light 3.5kg (8lb) weight. Critical components are brass, critical protective coatings are ceramic or chrome.
  • Performance is +/- 10% of the dial setting, making it twice as accurate as human vaporisers at typical low veterinary gas flows.
  • Leak-proof at 250mmHg.
  • Ten-year service interval to minimise down time, cost and inconvenience

 

Upgrade any anaesthesia machine with Darvall DVM vaporisers and start using environmentally responsible low-flow anaesthesia with virtually no maintenance.

Hallowell Model 2002PRO Ventilator

Easy to use: turn power on, set the respiratory rate and adjust the breath volume… couldn’t be simpler.

Three sizes of bellows available to enable accurate volume deliver for all animals from 2kg to 200kg! 

Easy to mount & connect to Darvall’s Stinger range – connects to the breathing bag port of any breathing system. 

  • Electronic control – substantially reduces the volume of driving gas required to operate pneumatically  
  • Respiratory rate – control knob is adjustable from 6 – 40 breaths per minute (BPM).  
  • Tidal volume range: standard bellows from approximately 100ml to 1,500ml;
    Small animals up to 10kg – bellows from approximately 20ml to 300ml;
    Foals, small ruminants and pigs – bellows from approximately 200ml to 3,000ml
  • Time cycled – the I:E ratio is constant at 1:2 so regardless of the respiratory rate setting two-thirds of the breath will remain for expiration. 
  • Volume constant – the fine volume control valve is adjusted to set each delivered breath which will have essentially the same volume, independent of changes in patient compliance and airway resistance. 
  • Pressure Limited – Pressure limit knob is adjustable from 10 – 60 cm H2O, providing for patient safety by limiting the maximum working pressure. For cats and dogs, the pressure limit is usually set to 20 cm H2O
  • Includes a Low Oxygen Pressure Alarm 

Absorbers

Darvall Stingray low-flow Absorber

Darvall’s premium absorber brings the finest innovation and manufacturing excellence to veterinary anaesthesia.

Stingray’s innovations overcome the two major problems of using low-flow anaesthesia in animals under 15kg (35lb):

  • The critical need to prevent rebreathing of CO
  • In the first 5 to 10 minutes (as IV induction agents are depleting) achieving and maintaining predictable, stable anaesthesia.

 

Darvall’s Stingray is a circle absorber for all animals from 2kg-80kg (4lb-175lb).  It is responsive to vaporiser changes in 5-10 breaths even at low gas flows (10-30ml/kg/min; 7-15ml/lb/min) for the smallest animals with a minimum system flow of 200ml/min, sufficient for all animals from 2-7kg (4-15lb). CO2 rebreathing is prevented by one-way inspiratory/expiratory valves that close with minimum force to ensure one-way gas flow for very small animals down to 1kg (2lb) taking only a 10 ml/breath.

 

Stable anaesthesia is rapidly achieved in 5-10 minutes by the innovative gas accumulator technology inside the grey base. This non-mixing reservoir holds a large volume of vaporiser fresh gas; like a non-rebreathing system it almost immediately delivers high concentration anaesthetic gas typically in 5. This is facilitated by Darvall’s low volume smooth-wall tubing and Darvall’s Minimum Dead Space Y-piece.

 

Stingray delivers highly efficient, predictable and reliable rebreathing anaesthesia, reduces patient hypothermia, delivers accurate ETCO2 readings compared to non-rebreathing systems, reduces consumable and operational costs while simultaneously safeguarding the environment.

.

Key Features of Darvall’s Stingray Low-Flow Absorber

  • Same circle system for animals 2kg-80kg (4lb-175lb).
  • Ideal to use with Darvall Cozy Heated Breathing Circuits.
  • Gas accumulator in the Stingray base, a reservoir for gas from the vaporiser to rapidly deliver anaesthesia in 5 breaths even at the lowest gas flows to the smallest patients down to 1kg (2lb).
  • Minimal risk of CO2 rebreathing due to precision, low resistance one-way valves that close with minimum force to ensure one-way gas flow.
  • Valve leaflets are colour coded for easy set-up and breath movement detection.
  • 100% efficiency CO2 usage due to uni-directional flow through the absorber.
  • Simple to change soda lime.
  • Fail safe APL “pop-off” spill valve with high pressure release at 30 cm H2
  • All hose, waste gas and inlet connections are clearly labelled and size indexed to prevent incorrect assembly and are precision manufactured to human anaesthesia standards to ensure secure, leak-proof connection of bags, hoses and fittings.
  • Includes an airway pressure gauge to permit pressure testing, ET cuff inflation and safe IPPV.
  • Up to 10x less gas consumption and emissions for animals under 15kg (30lb) compared to use of non-rebreathing systems

 

Darvall’s Stingray absorber fits all anaesthetic machines.

The Darvall SafeAbsorb

Darvall’s simple low cost one-piece circle absorber that is end-user replaceable. Manufactured from lightweight recyclable polycarbonate

Key Features of Darvall’s SafeAbsorb Absorber

  • Use on animals from 7kg- 80kg (4lb-175lb).
  • Maintain anaesthesia with 30ml/kg/min O (60 ml/kg/min in first 5 min.)
  • All hose, waste gas and inlet connections are clearly labelled and size indexed to prevent incorrect assembly and are precision manufactured to human anaesthesia standards to ensure secure, leak-proof connection of bags, hoses and fittings.
  • Ideal for MRI anaesthesia – no metal parts.
  • Can use with Darvall’s Cozy heated circuits.
  • Fail safe APL “pop-off” spill valve with high pressure release at 30cm H2O
  • Safe Absorb fits to any anaesthesia machine directly via center mount 22mm ID recess or via Fresh Gas Outlet adapter mount kit – Darvall PN 2984 – T Mount to common gas outlet 22mm (7/8”)

Stinger Anaesthetic Machine Configurations

Key Components

Ultra

Deluxe

 

Deluxe Tabletop

Streamline

Tabletop

Research Dual-Flow

Backpack

Field Use

Darvall part number

575

582

449

9360

2848

843

Manual & Clinical Guide

Y

Y

Y

Y

Y

Y

High Pressure O2 hose

Y

Y

Y

Y

Y

Y

Precision expanded scale O2 Flowmeter 4

Y

Y

Y

Y

Y

Y

DVM low flow Vaporiser

Y

Y

Y

Y

Y

Y

Vaporiser mount – Selectatec

Y

O

O

O

O

X

Airway Pressure Gauge

Y

Y

Y

O

O

Y

O2 Flush & FGO outlet assembly

Y

Y

Y

Y

Y

Y

3-Way switch for FGO outlet

X

X

X

O

Y

X

Secondary flowmeter 0-1 LPM

X

X

X

X

Y

X

SafeAbsorb Standard Absorber

X

Y

Y

O

O

Y

StingrayLlow-flow Absorber

Y

O

O

O

O

X

Smooth-Wall circuits in 2 sizes:    12mm & 16mm ID

Y

Y

Y

O

O

Y

Heated Circuits, Lack & control unit

Y

O

O

O

O

X

NRB Bain circuit (not heated)

Y

Y

Y

Y

Y

Y

NRB ZDS Face Mask circuit

Y

Y

Y

Y

Y

Y

IV pole mount assembly

Y

Y

O

O

O

X

Mobile base assembly

Y

Y

O

O

O

X

Swing-Arm wall mount

X

X

O

O

O

X

O2 DS Cylinder Holder

O

O

O

O

O

X

Storage basket, pole mounted

O

O

O

O

O

X

WAG Charcoal scavenger

Y

O

O

O

O

O

WAG Air Brake for suction

O

O

O

O

O

X

Backpack Pelican Case

X

X

X

X

X

Y

Ventilator Anaesthesia – Hallowell

O

O

O

O

X

X

Y = standard   O = Optional Extra      X = NO (or n/a)

APL = Adjustable Pressure-Limiting spill valve

FGO = Fresh Gas Outlet

NRB = Non-Rebreathing circuit

ZDS = Zero Dead Space

WAG = Waste Anaesthetic Gas

Smooth-Wall circuits supplied in 2 sizes:

Small = 12mm (under 30kg [60lb])

Large = 16mm ID (over 30kg [60lb])

Darvall’s Breathing Circuit & Consumables Selection

(All end user replaceable)

For all small animal species and fit to any machine:

  • Smooth-Wall Low-Resistance Breathing Circuits* – 2 sizes that reduce volume by 1/3 to 1/2 for low flow anesthesia in dogs, cats, rabbits etc.
  • Lack* non-rebreathing circuit with minimum dead space “MDS” Y, APL safety valve and 12mm smooth-wall hoses for animals from 1kg up to 15kg (2lb-35lb).
  • Bain non-rebreathing circuit for animals from 1kg up to 15kg (2lb-35lb)..
  • T-Piece non-rebreathing circuit for animals from 1kg up to 7kg (2lb-15lb)..
  • F-Circuit single limb coaxial circuit (tube within tube) for circle systems for animals 5kg-80kg (10lb-175lb)
  • Zero Dead Space Face Mask non-rebreathing system suitable for induction and maintenance of pups, kittens, exotics, birds etc up to 2kg (4lb).
  • Zero Dead Space “ZDS” Qube* non-rebreathing system with interchangeable masks for birds, exotics, rodents and reptiles up to 1kg (2lb).
  • Minimum Dead Space Y-piece for circle systems and Lack circuits on animals up to 15kg (35lb
  • Darvall breathing bags – 5, 1, 2 & 3 L available in black rubber or green latex free
  • Darvall Endotracheal tube wall rack – holds all sizes of ET tube to size 14, can use to hang & drain washed breathing circuits

*available as Heated Circuits preventing hypothermia from the start of anesthesia

Darvall Cozy Heated Smooth-Wall Breathing Circuits

Darvall Smooth Wall Breathing Circuits reduce gas volume by 1/3 to 1/2 for sustainable low flow anaesthesia.

  • Low volume permits rapid anaesthetic response to vaporiser dial change at low flows.
  • Smooth wall has low resistance.
  • Moulded hose-ends for secure connection to breathing systems.
  • Easy to clean – simply rinse, drain and hang to dry.
  • Two sizes for all patients:
    • use 12mm (1/2”) ID up to 30kg (65lb).
    • use 16mm (5/8”) ID from 30kg to 80kg (65lb to 175lb).
  • Supplied with breathing bags and selected adapters including MDS Y-piece (12mm circuits).
  • Use with Darvall’s Stingray or SafeAbsorb absorbers or Lack non-rebreathing circuit.

 

Also available as Cozy Heated smooth-wall Circuits provide warm inspired gas from the first breath after intubation to prevent post-induction hypothermia. A dual approach to warming when combined with the Cozy Warm Air Blanket system is the most efficient and environmentally responsible approach to managing peri-anaesthesia hypothermia. (See Managing Hypothermia)

Darvall’s Smooth-Wall circuits and Cozy Heated smooth-wall circuits are a valuable upgrade to any inhalation anaesthetic breathing system.

Cozy Heated smooth-wall circuits are standard on Darvall’s Stinger Ultra

The Darvall Lack non-rebreathing circuit

Darvall’s Lack circuit can be used on the tiniest patients such as early spey/neuters 0.5kg-2kg (1lb-5lb). The Darvall Lack circuit is the only non-rebreathing system that can be effectively warmed using heated smooth-wall circuits.

Key Features of Darvall Lack circuit:

  • Use with Darvall’s Smooth Wall circuits.
  • Low volume, low resistance smooth-wall tubing.
  • Fail-safe Adjustable Pressure-Limiting (APL) Valve
  • Use efficient low gas flows on very small patients below 10kg (20lb).
  • Incorporating Darvall’s unique Minimum Dead Space (MDS) Y-piece.
  • Available as a Heated Lack to prevent hypothermia.

Zero Dead Space Face Mask non-rebreathing system

For anaesthesia or oxygen therapy in pups, kittens, rabbits, rodents, reptiles & birds to 2kg (4lb)

  • Polycarbonate mask 4cm (1.6”) OD supplied with two diaphragms in two aperture sizes.
  • Diaphragms aperture sizes 1.2cm (1/2”) and 1 x 2cm (3/4”).
  • Head does not need to fill a mask due to Zero Dead Space unidirectional flow.
  • Uni-directional mask gas flow eliminates dead space so no rebreathing of CO2.
  • Zero Dead Space gas flow ensures predictable anaesthetic gas delivery.
  • Connect Qube to any anesthetic machine fresh gas outlet.
  • Minimum O2 flow 100 ml/kg/min (50 ml/lb/min).

Darvall Anaesthesia Face Masks – cones with diaphragms

 

Part

Mask Size

Application

Description

5288

Face Mask  #1

45mm (1 3/4″) OD, tapered cone

Exotics / Kitten

45mm (1 3/4″) OD, tapered, polycarbonate. Supplied with silicon diaphragm 22mm (7/8″) aperture

546

Face Mask #2

60mm (2 3/8″) OD, tapered cone

Face Mask#2:

Rabbit / Small Cat

Mask 60mm (2 3/8″) OD, tapered, polycarbonate. Supplied with silicon diaphragm 29mm (1 1/8″) aperture

1861

Face Mask #3

63mm (2 1/2″) OD, tapered cone

Large Cat / Small Dog / Bird

Mask 63mm (2 1/2″) OD, tapered, polycarbonate with strap holder. Supplied with silicon diaphragm 37mm (1 1/2″) aperture

547

Face Mask #4

94mm (3 3/4″ ) OD, tapered cone

Small Dog / Bird

Mask 94mm (3 3/4″) OD, tapered, polycarbonate with strap holder. Supplied with silicon diaphragm 39mm (1 1/2″) aperture

1862

Face Mask #5

113mm (4 1/2″) OD, tapered cone

Medium Dog

Mask 113mm (4 1/2″) OD, Tapered, polycarbonate with strap holder. Supplied with silicon diaphragm 45mm (1 3/4″) aperture

548

Face Mask #6

140mm (5 1/2″) OD, tapered cone

Large Dog /Pig / Calf / Newborn Foal

Mask 140mm (5 1/2″) OD, tapered, polycarbonate with strap holder. Supplied with silicon diaphragm 74mm (2 7/8″) aperture

549

Face Mask Set of 6 Tapered Cones                               50mm(2″) to

140mm(5 1/2″) OD

Full range of tapered cone face masks all 6 sizes in carry case

Face Mask Set of 6 masks sizes OD:                                       45mm (1 3/4″), 60mm (2 3/8″), 63mm (2 1/2″),               94mm (3 3/4″), 113mm (4 1/2″) and 140mm (5 1/2″)             plus 2 x silicon head straps 50cm (20″) long

Darvall Cozy Zero Dead Space Qube

Zero Dead Space (ZDS) Qube non-rebreathing system for exotics, birds, rodents, & reptiles up to 2kg (4lb).

  • Stable aluminium block and rotates to adjust mask height.
  • ZDS+ Qube masks in five sizes supplied separately with autoclavable diaphragms.
  • Sealing masks and diaphragms reduce gas emissions.
  • Uni-directional mask gas flow eliminates dead space so no rebreathing of CO2
  • Zero Dead Space gas flow ensures predictable anaesthetic gas delivery.
  • Can use with ZDS+ Qube Extension for better access to the animal’s head.
  • Qube can be connected to any anaesthetic machine fresh gas outlet.
  • Use with DVM Vaporiser for sustainable minimum O2 flow 100 ml/kg/min (50 ml/lb/min).
  • Can use ZDS+ Qube with SAV04 ventilator and deliver IPPV at low gas flows.
  • Available as a Heated Qube to prevent hypothermia.

Cost Saving Calculations

Traditional Anaesthesia vs. Low Flow with Darvall Stinger Ultra and Darvall DVM Vaporiser

Download

Case Study

A 7.5kg Dachshund was presented for anaesthesia for thoracolumbar spinal decompressive surgery. A Darvall Stinger Ultra anaesthetic machine was used. It was set up with a 0.35L CO2 absorber canister and a 0.5L breathing bag. The system was pressure tested prior to use. Darvall Cozy heated circuits with 12mm tubing was used.

The dog was premedicated with acepromazine 0.03mg/kg and methadone 0.3mg/kg SC.

Anaesthesia was induced with proprofol and the patient intubated, connected to the breathing system and cuff inflated. The APL “pop-off” valve was set fully open.

The DVM Iso vaporiser was set to 2.5% with an O2 flow of 60ml/kg/min to flush the room air out of the Stingray breathing system.

After 5 minutes the O2 flow was lowered to 30 ml/kg/min and vaporiser set to 2%; the patient’s vital signs were checked and monitored. No further adjustment was needed.

Surgery duration was 80 minutes, total anaesthesia 115 minutes. Recovery was uneventful.

Comparison of features of the Darvall Stinger Ultra and the Humphrey ADE

FeatureDarvall StingrayHumphrey ADE
Convenience1,2Simple – Same circle system for animals 2kg-80kgRe-assembly needed to switch from semi-closed LAC up to 15kg or circle system >15kg
Resistance3Lowest of six systems testedSecond highest tested – five times higher than Darvall Stingray
Response to vaporiser change4Rapid – 5 to 10 breathsSlow for circle system – 24 breaths before isoflurane detected (approx. 2 min)
Fresh Gas Flow for patients 2-15kg2,4,5,6Low: 10ml/kg/min to 30 ml/kg/min.
200 ml/min minimum		High: 100 ml/kg/min (Semi-closed).
500 ml/min minimum
O2 “G” cylinder consumption190 hours – 10kg dogs57 hours – 10kg dogs
Need O2 Concentrator7No: Low Flow Stingray uses less than 1L/min up to 35kg animalsOffers concentrator, use of which removes any benefit of Low Flow.
CO2 Rebreathing RiskLowYes – rebreathing threshold results in sudden inspired CO2 increase
CO2 Absorber EfficiencyGood: 100% – gas flows top to bottom of canister; indicator change easy to see50% – gas tracks once it passes under the centre divider, 2nd side indicator change unreliable
CO2 Absorbent changeSimple & quickComplicated: upside down position to disassemble
Pop-Off ResistanceOpens @ 2 cmH20: 10L/min exp. flowOpens @ 3 cmH20: 10L/min exp. flow (=15kg dog)
Pop-Off Safety accidental closureFail Safe at 30 cmH20No Fail Safe relief

References

  1. Dunlop CI. Darvall Stingray Circle Absorber white paper. Darvall website 2015.
  2. Humphrey D. The Humphrey ADE-circle anaesthetic system in veterinary practice. Anaequip Website: 2015.
  3. JS Dunlop, CI Dunlop, P Hartigan et al. Comparative Flow Resistance of Circle Breathing Systems used for Anaesthesia of Small Animals. Abst. WCVA, Capetown S. Africa Sept 2012.
  4. CI Dunlop, JS Dunlop, RA Curtis et al. Comparison of the dynamic response to changing anaesthetic concentration in circle breathing systems used on animals from 3 to 20Kg. Abst. WCVA, Capetown S.Africa Sept 2012
  5. Brown V. The rate of rise of inspired anaesthetic concentration in a rebreathing system suitable for small dogs and cats. BScVet Hons Thesis Faculty of Veterinary Science, University of Sydney
  6. Alibhai HIK, Lilja AS, Clarke KW. Evaluation of the Humphrey ADE circuit during spontaneous ventilation in dogs. Abst.Vet Anaesth Analg 26:38-39; 1999.
  7. Artu AA, Katz RA. Evaluation of the Humphrey ADE breathing system. Can J Anaesth 34:484-488;1987

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