VNJ Volume 38 (3) June 2023 | Page 22

Use a rebreathing circuit

Practices use various breathing circuits to connect patients to oxygen and anaesthetic gas post-induction and intubation . The type selected often depends on the patient ' s size and the duration of the procedure .

Common breathing circuits include the T-piece , Mini Lack , Parallel Lack , Bain and circle rebreathing systems , with practices usually keeping a selection of these circuits ready for use .

Some breathing circuits are more environmentally friendly than others . For example , using a circle rebreathing circuit can reduce the amount of oxygen and volatile agent used for an anaesthetised patient .

A circle rebreathing circuit has the same components as other breathing circuits , with the addition of a soda lime canister . The exhaled anaesthetic gases can be reused and rebreathed after the expired carbon dioxide ( CO 2

) has been absorbed by the soda lime [ 7 ] . Rebreathing expired gases enables lower volumes of volatile agents and oxygen to be used in the anaesthetic procedure .

Before using a circle rebreathing system for the first time in practice , extensive training and related CPD should be provided for staff to ensure it is used correctly and safely .

Opt for sustainable anaesthesia

Fresh gas flow rates ( FGFRs ) should be encouraged for procedures involving a general anaesthetic . This allows patients to be placed on an adequate oxygen flow for their weight and average respiration rate . FGFRs also prevent rebreathing of CO 2 gas , which can be detrimental to a patient ' s health [ 7 ] .

Woodward Veterinary Practice has encouraged VNs to complete FGFR calculations by having the formula on the anaesthetic sheets for every patient ( Table 2 ).

Posters have also been placed by each anaesthetic machine , reminding VNs to calculate FGFRs and use rebreathing systems wherever possible .

Both pre- and perioperative analgesia can play an important role in sustainable anaesthesia . Perioperative analgesia can help to reduce the need for a greater anaesthetic depth and relieve pain felt by the patient .

In some instances , an anaesthetised patient may present with clinical signs such as tachycardia and tachypnoea as a response to pain . As a result , their anaesthetic depth may be increased in an attempt to ease perioperative reactions . Giving patients adequate analgesia can reduce the temptation to increase the amount of volatile agent to try to control their reactions while under anaesthetic .

Local anaesthetics and splash blocks can also reduce the need for a deeper plane of anaesthesia to mitigate a pain response . Local anaesthetic drugs , such as lidocaine , can be injected around incision sites or directly into areas of surgery , such as the testicles pre-castration . Zeltzman [ 8 ] discusses how intratesticular blocks have been shown to reduce the requirements for inhalant anaesthesia during neutering surgery . Patients that received a block also showed reduced pain scores postoperatively .

VNs should discuss with the operating veterinary surgeon whether additional analgesia or local anaesthetic is appropriate for a patient or procedure , on a case-by-case basis . Adequate training and protocols should also be put in place to aid in staff competence and patient safety .

Say ‘ no ’ to nitrous oxide

Nitrous oxide is a colourless , odourless gas that is usually stored in blue cylinders . It has analgesic properties and can , in some cases , reduce the amount of volatile agent needed to maintain a plane of anaesthesia [ 9 ] .

Table 2 . Fresh gas flow rate formula calculation .

Mini Lack 1 – 1.5 < 10 kg ( kg ) × 10 ml Lack 1 – 1.5 > 10 kg ( kg ) × 10 ml Bain 2.5 – 3 8 – 15 kg (< 10 kg × 15 ml )

FGFR = MV × circuit factor

(> 10 kg × 10 ml ) Magill 1 – 1.5 10 – 80 kg (< 10 kg × 15 ml )

(> 10 kg × 10 ml )

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