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A&S - Week 4
The Anaesthetic Machine & Thoracic Surgery
| Question | Answer |
|---|---|
| What Is The Function Of An Anaesthetic Machine? | To deliver oxygen along with a precisely controlled concentration of anaesthetic vapour. |
| What Are The Two Common Volatile Anaesthetic Agents Used In An Anaesthetic Machine? | -Isoflurane -Sevoflurane |
| What Components Make Up All Anaesthetic Machines? | -High pressure side directly from the oxygen and nitrous oxide cylinders -Pressure gauge -Regulator -Low pressure side -Needle valves and rotameters -Vaporisers -Oxygen flush -Common gas outlet to circuit -Low oxygen alarm |
| What Sizes Of Oxygen Cylinder Are Commonly Used In Practice? | -E (smallest), F and J |
| What Is The Function Of An Oxygen Concentrator? | Concentrates oxygen from atmosphere. |
| What Is The Function Of The Pin Index System On An Oxygen Cylinder? | -Ensures the correct gas is filled into the correct cylinder -Ensures the correct equipment is connected to the cylinder |
| Why Should Lubricants Never Be Used On An Anaesthetic Machine? | -They can be ignited in the presence of oxygen from tiny sparks caused by friction in the machine -Grease, dust and oil can also be ignited from sparks |
| What Colour Are Oxygen Cylinders? | Black and white. |
| What Colour Are Nitrous Oxide Cylinders? | Blue. |
| What Does It Mean If An Anaesthetic Machine Uses Piped Gas Oxygen? | -Cylinders stored outside -Cheaper - usually larger cylinders -More difficult to access when needs changing |
| What Is The Function Of The Pressure Gauge On An Oxygen Cylinder? | Indicator of how much oxygen is left in cylinder. |
| Why Is The Pressure Gauge Not A Reliable Indicator With Piped Oxygen? | -The oxygen pressure gauge on the machine will just tell you the pressure within the pipes -There will be another gauge on top of the cylinder that will give you an indication of how much oxygen remains |
| Why Is The Pressure Gauge Not A Reliable Indicator With Nitrous Oxide? | -The gauge will only show the gas pressure, which will remain high until all the liquid nitrous oxide is gone, then it will drop suddenly -To estimate how much nitrous oxide remains, it is easier to weigh the cylinder |
| What Is The Purpose Of The Regulators In An Anaesthetic Machine? | -Regulates high pressure gas to low pressure |
| What Is The Purpose Of The Vaporiser In An Anaesthetic Machine? | Gives volatile agent within specific temp and pressure range. |
| How Are Vaporisers Re-Filled? | -Key systems with distinct colour to match colour of vaporiser and gas bottle -Also funnels -Important to plan for spills (H&S) |
| What Is The Purpose Of The Oxygen Flush And Where Is It Usually Located? | -Bypasses vaporiser to deliver a fast flow rate oxygen without anaesthetic gas -Located near common gas outlet |
| How May Inhalational Agents (Volatile Agents, Oxygen) Be Delivered To A Patient? | -Anaesthetic chamber -Mask -Breathing system (circuit) with ET tube |
| What Are The Key Properties (Pros/Cons) Of Using An Anaesthetic Chamber To Deliver Inhalational Agents To A Patient? | -Used for induction of anaesthesia in small patients -Airtight and scavenged -High flow rate to avoid rebreathing carbon dioxide -Difficult to assess anaesthetic depth |
| What Are The Key Properties (Pros/Cons) Of Using A Mask To Deliver Inhalational Agents To A Patient? | -Used for induction, maintenance and supplementation -Should be close fitting -Easy to use, useful for short procedures, useful for small mammals that cannot be intubated -Mask may leak, airway not secure, surgical access to face and mouth limited |
| What Are Some Considerations For Choice Of ET Tube In Cats/Dogs? | -Should use largest tube that can pass comfortably -Cuffed tubes in dogs -Un-cuffed in cats -V gel tubes: sits in larynx, good for cats, small mammals, avoids tracheal spasms, irritation |
| Which Type Of ET Tube Delivers High Pressure - Low Volume? | Red rubber ET tubes. |
| Which Type Of E Tube Delivers Low Pressure - High Volume? | Silicone ET tubes (theoretically safer, however cuff needs to be adequately inflated). |
| What Are The Aims Of Breathing Systems? | -Delivery of oxygen and volatile agent (+/- nitrous oxide) -Removal of carbon dioxide and volatile agent -Control of ventilation in some cases - intermittent positive pressure ventilation (IPPV) |
| What Must Be Considered When Choosing A Breathing System For A Patient? | -Size of patient -Economy -Nitrous oxide being used? |
| What Anaesthetic Circuits Are Classed As Re-Breathing? | -Circle -Humphreys ADE |
| What Anaesthetic Circuits Are Classed As Non-Re-Breathing? | -Modified T-piece -Bain -Lack -Humphreys ADE |
| What Are The Advantages Of Re-Breathing Anaesthetic Systems? | -Low gas flow rates -Low volatile agent consumption -Expired moisture and heat conserved -Less pollution |
| What Are The Disadvantages Of Re-Breathing Anaesthetic Systems? | -High resistance to breathing -Cannot use nitrous oxide safely -Expensive to purchase -Regular soda lime replacement needed -Inspired gas undetermined -De-nitrogenation required -Can be slow to change level of anaesthesia |
| What Are Some Considerations For Using Re-Breathing Anaesthetic Systems? | -Used in larger patients -Begin at higher flow rate for de-nitrogenation (2-4l/min) -Then reduce flow rate, generally run semi-open at 0.5-1l/min |
| What Are Some Considerations For Using Non-Re-Breathing Anaesthetic Systems? | -If no soda lime is present then the system must not allow rebreathing -Enough gas must be supplied to flush away all the carbon dioxide before the next breath is taken -Fresh gas flow rate to prevent rebreathing |
| How Can Fresh Gas Flow Rate Be Calculated? | -Tidal volume = volume of air breathed in in a normal breath (cats and small dogs 15ml/kg, medium and large dogs 10ml/kg) -Minute volume = tidal volume x resp rate -Flow rate = minute volume (litres) x circuit factor |
| What Is The Circuit Factor For A T-Piece And Bain? | -2 ½ - 3 |
| What Is The Circuit Factor For A Lack? | -1 – 1 ½ |
| What Types Of Gas Are Present In A Breathing System? | -Fresh gas -Alveolar gas -Anatomical dead space gas (gas that did not reach alveoli, still oxygen rich) -Mechanical dead space (dead space in system, cannot be fully scavenged, patient ends up rebreathing this gas, mostly carbon dioxide) |
| How Can A Humphrey's ADE Circuit Be Used Both As A Re-Breathing System And Non-Rebreathing System? | -Used with the soda lime as a circle -Used without as a lack -Circle: helps to reduce resistance allowing it to be used on smaller patients than a normal circle -Lack: allows very low flow rates, permits rebreathing of anatomical dead space gas |
| Define Tracheostomy | Creating of an opening into the trachea. |
| Define Tracheotomy | Incision into the trachea. |
| What Two Types Of Tracheostomy Tubes Can Be Used? | -Single lumen -Double lumen (more versatile) |
| What Are The Main Steps In Tracheostomy? | 1.Dorsal recumbency 2.Incision behind larynx to expose trachea, then between 2/3rd, 3rd/4th tracheal ring 4.Tube should be length of 6-7 tracheal rings 5.Suture into trachea, on opposing edges of incision 6.Insert tube, close skin, use of suction |
| What Are The Pre-Op Considerations For Tracheostomy? | -Remain calm, stressful situation, often performed as patient in resp distress -Careful handling (stress free) -Oxygen supplementation -Withholding food unlikely (as emergency) -Ventral neck needs to be aseptically prepared |
| What Are The Intra-Op Considerations For Tracheostomy? | -Dorsal recumbency -Sand bag under neck -Monitoring -Is suction machine available? |
| What Are The Post-Op Considerations For Tracheostomy? | -Prevent tube becoming blocked: careful handling, use gloves -Regular suction – pre-oxygenate before + after -Humidification via nebuliser, tube adapter, saline -Regular cleaning – take out and clean lumen if double lumen with hibi -Kennel hygiene |
| Define Permanent Tracheostomy? | -Skin is permanently sutured to the mucosa of the trachea *prone to infection* |
| What Can Be Done In Respiratory Emergencies When Tracheostomy Is Not Possible? | -Wide gauge needle or catheter can be pushed quickly through ventral midline of neck, between tracheal rings into trachea -Oxygen can then be supplemented -Non-permanent solution |
| What Is Laryngeal Paralysis? | -Arytenoid cartilage in larynx fails to abduct (move aside – open airway) during inspiration, results in a narrow lumen – resp distress -Can develop due to nerve damage, tumour, etc can be idiopathic -Common in large older breed dogs |
| What Are The Clinical Signs Of Laryngeal Paralysis? | -Change in tone of bark -Gasping and panting -Resp distress |
| What Are The Pre-Op Considerations For Laryngeal Tie Back (Laryngeal Paralysis)? | -Remain calm, patient should already be stabilised, may have tracheostomy -Careful handling (stress free) -Oxygen supplementation -Entire cervical area to be aseptically prepared -Steroids may be given |
| What Are The Intra-Op Considerations For Laryngeal Tie Back (Laryngeal Paralysis)? | -Lateral or dorsal recumbency, neck elevated by sandbag |
| What Are The Post-Op Considerations For Laryngeal Tie Back (Laryngeal Paralysis)? | -Sternal recumbency -Delay extubating -Oxygen supplementation -Cool, stress-free environment -Pain scoring and analgesia -Tinned food 12-24 hrs later -Strict rest for 6 weeks |
| What Is Tracheal Collapse? | -Common in smaller dogs, toy, or miniature -Not necessarily entire trachea -Weakened tracheal rings -Congenital factors such as obesity, recent intubation, infection ,cardiomegaly, inhalation of irritants |
| What Are The Clinical Signs Of Tracheal Collapse? | -Honking cough -Rasping pant |
| How Can Tracheal Collapse Be Managed Medically? | -Weight loss -Replace collar with harness -Restrict exercise -Removal of irritants (smoking) -Treatment of underlying/causal disease |
| How Can Tracheal Collapse Be Managed Surgically? | -Extra-Luminal Prosthesis (opening on trachea from outside) -Intraluminal Prosthesis (stent into trachea) |
| What Are The Pre-Op Considerations For Extra-Luminal Prosthesis/Intraluminal Prosthesis (Tracheal Collapse)? | -Cool, calm environment -Careful handling round neck -Oxygen supplementation -Caudal mandibular area, ventral neck, and cranial thorax aseptically prepared |
| What Are The Intra-Op Considerations For Extra-Luminal Prosthesis/Intraluminal Prosthesis (Tracheal Collapse)? | -Dorsal recumbency with neck elevated with a sandbag -Monitoring oxygenation and ventilation |
| What Are The Post-Op Considerations For Extra-Luminal Prosthesis/Intraluminal Prosthesis (Tracheal Collapse)? | -Close monitoring -Quiet, stress-free environment (sedation if needed) -Cough suppressants -Oxygen supplementation -Cage rest for 3-7 days -Harness vs neck lead -Pain scoring and analgesia |
| Define Thoracotomy | Temporary opening into the thorax to allow surgery. |
| What Are The Two Approaches To Thoracotomy? | -Lateral/intercostal thoracotomy -Sternal thoracotomy |
| What Is A Ruptured Diaphragm And What Can Cause This? | -Blunt force trauma to abdomen = compression of organs, burst through diaphragm into thoracic cavity -Radial or circumferential tear -Causing impaired ventilation, collapse of airway, pressure on major vessels, ischaemia of organs |
| What Are The Clinical Signs Of A Ruptured Diaphragm? | -Dyspnoea -Tachypnoea -Empty feeling abdomen -Paradoxical breathing (breathes in, chest moves in – loss of pressure difference) -Can be chronic – patient can survive with this |
| How Can A Ruptured Diaphragm Be Treated? | -Higher mortality rate in animals that undergo surgery with 24 hours of trauma or more than one year later -Stabilise first -Emergency surgery if unable to stabilise |
| What Happens During Surgery In Order To Correct A Ruptured Diaphragm? | -Cranial midline laparotomy -Oxygenate as soon as abdomen opened -Organs returned to abdomen -Diaphragm sutured -Air drained from thoracic cavity |
| What Are The Pre-Op Considerations For Ruptured Diaphragm Correction? | -Monitoring -Calm, careful handling -Pre-oxygenation -Avoid ACP and nitrous oxide -Abdomen and caudal two thirds of thoracic cavity aseptically prepared |
| What Are The Intra-Op Considerations For Ruptured Diaphragm Correction? | -Dorsal recumbency -IPPV required as soon as abdomen is opened -Monitoring of oxygenation and ventilation |
| What Are The Post-Op Considerations For Ruptured Diaphragm Correction? | -Sternal recumbency -Oxygen supplementation -Close monitoring -Thoracotomy tube/thoracic drain care |
Created by:
aimee_knows_nothing
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