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22 Cards in this Set
- Front
- Back
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what situations is Jet ventilation used? |
Elective: for airway surgery or in ICU for lung protective ventilation. in anticipated difficult airway can place transtracheal needle to allow oxygenation. Emergency: for Jet ventilation in CICO with needle cricothyroidotomy. |
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What are the types of Jet ventilation and when are they used? |
low frequency Jet Ventilation (LFJV): this is the most commonly used in anaesthetics for airway surgery or emergency CICO. High frequency jet ventilation (HFJV): rarely used in anaesthetics. ?this is what is used in ICU for ARDS. can be used for one lung ventilation on non ventilated lung - provides some oxygenation with minimal movement. bronchoplural fistula as doesn't require bulk flow of gas. High frequency oscillatory ventilation (HFOV): this is a subset of HFJV that is used in neonates (i.e. the oscillator). Its different to HFJV as has active inspiration and expiration. |
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Describe how LFJV works in the elective setting? |
an injector supplies high pressure oxygen via a short, stiff cannula. As its an open airway, this entrains air due to the venturi effect to provide a close to physiological tidal volume. This causes bulk flow of oxygen to the lungs and then passive expiration. |
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How is the different to the emergency setting in CICO? |
In CICO with needle cricothyroidotomy there is NOT an open airway...therefore the injector does not entrain air.. in this setting you are not ventilating the patient but only oxygenating, using the high pressure device to overcome the high resistance of the cannula. Expiration is passive (except in same where have active expiration). the cannula resistance is to high for the natural recoil of the lungs and expiration will only occur via an open airway. |
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What is the venturi effect? how does it apply to jet ventilation. |
the bernouilli principle is key to it: a moving stream of fluid/gas has a constant energy (made up of kinetic and static - the pressure it exerts on the walls of the tube). as fluid enters a narrow segment it speeds up, > kinetic energy & therefore < static energy/force against wall. so a narrow segment will make vacuum and entrain air if open - this is the venturi effect. |
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what are the types of injector used for LFJV? how are they set up? what pressures do they run off? |
Sanders injector is the original and what knew ones are based on - e.g. manujet. connect direct to wall outlet or gas cylinder - so receive oxygen at 4bar pressure. internal pressure regulator alters pressure from 0-4 bar. 0-1 is the green section. |
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How do you use the sanders injector in elective airway surgery? |
once set up with wall oxygen, titrate injecting pressure to get "normal' chest expansion. aim for normal RR - 10-12 - this allows adequate time for passive expiration. is used with rigid laryngoscope or rigid bronchoscope that have rigid cannula in place to inject down. |
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what are the pros and cons of LFJV? |
Pros: easy set up and easy to use. allows good surgical access as ETT not in the way and larynx is immobile. Cons: risk of barotrauma, stomach insufflation if mall aligned, need to use TIVA as can't deliver inhalational, can't measure ET CO2. need to paralyse. |
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what are the options for LFJV in the emergency setting? |
Once needle cricothyroidotomy in place can use: - sanders injector. - 3 way tap with 15L O2. - Ventrain device. |
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what is the ventrain? how does it help? |
provides active expiration by venturi effect. inflation - occlude 3+5 expiration - occlude 5 no action - no holes closed. |
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what is the theory behind HFJV? how does this oxygenate the lungs? |
HFJV = rate 60-600 (usually about 60-100) doesn't provide bulk flow of gas, instead relies on diffusion of gases. the HFJV provides: high O2, low CO2 environment for diffusion. agitates the gas in the airways to facilitate mixing and diffusion. |
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what are the pros and cons of HFJV? |
Pros: provides oxygenation with minimal TV and therefore reduces volutrauma. minimal chest expansion/airway movement good for surgeons. Cons: barotrauma. unable to measure CO2, airway pressure easily. requires specific ventilator with high frequency mode. needs TIVA. |
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what is microlartyngoscopy tube (MLT)? when is it used and what are the pros and cons? |
small diameter, adult length tube (often size 5) used for microlaryngoscopy - examination of larynx with microscope. Pros: secure airway for aspiration etc. closed circuit so can use IPPV/volatile anaesthetic/measure CO2. CONs: high resistance, high inspiratory pressures. can obstruct surgeons view. risk of airway fire is laser used. |
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what is the difference between an MLT size 5 and a standard size 5 used in paediatrics? |
1 - the length: MLT is standard adult length, paediatric size 5 will be to short. 2 - cuff: has a larger volume cuff - allows it to be HIGH volume, LOW pressure cuff. a pedi tube cuff will need to be inflated to maximal volume and may still not seal - this would make it HIGH pressure, Low volume and possible cause ischaemia. |
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Inhaled foreign body: What is important on hx /ex? |
1 - what is inhaled - battery vs food, size, 1 or more. 2 - when: hours ago = likely no inflammatory change around it. days/week ago = inflam, hard to retrieve, atalectais and infective process behind it so oxygenation may not improve once its removed. 3 - current sx/extent of resp distress, can the lay flat. 4 - are they fasted? important in this case as will have UNPROTECTED AIRWAY during operation. |
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How would you set up the theatre for FB anaesthetic? |
surgeon - must be in the room, scrubbed with rigid bronch ready incase dislodge FB on induction and can't ventilate. second anaesthetist - one for airway. one for IV, drugs, monitors etc. senior anaesthetic assistant Tiva setup ??difficult airway trolley?? |
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what is your anaesthetic plan for inhaled FB? what are the risks of your plan? |
there are 2 types of anaesthetic options: 1 - spont vent gas induction, keep spent breathing and switch to TIVA. Issue - need to be very careful with anaesthetic level, continues physical monitor of breathing. If pt coughs - can put rigid bronch through wall of trachea/bronchus - this is why some do relaxant approach. 2 - relaxant GA. intermittantly ventilate the patient (LMA or BMV) then let surg do bronch till desaturate, then ventilate again. Issue - IPPV can dislodge FB down airway. makes surg more difficult. |
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outline how you would run TIVA for inhaled FB? |
propofol infusion titrated to depth of anaesthesia/RR Opioid - either remi infusion (0.05mcg/kg/min - leave on this, don't titrate) or small boluses of fentanyl. |
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Facial trauma: draw the anatomy of the bones of the face. what are the regions of the facial bones what is lefort fractures? |
the main ones to know are the mandible, maxilla, zygoma, nasal, ethmoid (sits in superior nose/base of skull) and sphenoid (base of eye socket and out behind zygoma) the face is divided into 1/3's. lower 1/3 = mandible. mid 1/3 = maxilla, zygoma, nasal bones and lower ethmoid. upper 1/3 = upper part of ethmoid, sphenoid, frontal bones lefort = these are all fractures of the mid face / middle third. - therefore involve maxilla, zygoma and nasal bones lefort 1 = maxilla only. lefort 2 = maxilla up to nasal bones. this is more mobile then 1 and can have more blood loss. lefort 3 = separation of entire mid face off the skull. maxilla, nasal bones and zygoma. the mid face is very mobile. lefort 3 can be airway emergency as can sink down and occlude the nasopharynx when supine. - pt normally want to sit up and forward. - facial bones are vascular, can get heavy bleeding/swelling that compromises the airway. - shouldn't do nasal stuff in lefort 3. ?lefort 2??? |
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What are the considerations in any ENT case to think about? |
there are some thing you need to think about in any ENT case that are often not involved in other anaesthetics; obviously the airway is a key one, other random things... BENT B - BP control for any microscopic or endoscopic procedure to reduce blood loss and allow the surgeons to see. e.g. FESS, middle ear surgery. E - epinephrine. ie topical vasoconstrictors and hypertension. particular issue if IHD. N - nerves. RLN in thyroid/neck dissection. facial nerve in parotid or middle ear surgery. T - throat packs...Fess, adenoids, |
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what types of airway can be used for microlaryngoscopy or panendoscopy. |
both of these procedures involve the surgeons assessing the airway and thus our tubes will be in the way....also consider laser could be used in some of these cases. options are: MLT jet vent with different options spont vent intermittant IPPV with BMV MLT tube...size 5. Pros: - allows inhalational with ET monitor - IPPV with relaxant so the pt is still. - allows ET CO2 measured. Disadvantage: - in the surgeons way a bit more. - flammable if using laser. Jet vent: there are several ways that a jet vent can be used for this...divide into supraglottic, infraglottic and transtracheal. Supraglottic - ie jet vent down the rigid laryngoscope. Pros: - best vision/access for surgeons. - no flammable part if laser and can stop ventilating at the time. - minimal movement of the cords. Cons: - can't do inhalational so need TIVA - can't measure ETCO2. - risk of barotrauma if misdirected jet stream. - not secure airway - need extra equipment. Subglottic - hans zucker. Pros: - less barotrauma as flow directed in midline. - can measure some CO2 depending on the device. - very small, smaller than MLT so less obstruction for surgeon and less risk of fire for laser. Cons: - tiva - not secure ariway - still is flammable. Transtracheal - ie cricothyroid cannula. Pros: - out of surg way. - back up airway cons: - damage to structures - surgical emphysema and loss of airway |
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Plastics: outline the plan for a free flap? |
The key for a free flap is to maintain flap perfusion.. Factors: - blood oxygen carrying capacity - arterial flow - direct compression - venous flow. Other factors: - long case, pressure, temp, position etc be sure to mention: - post op monitoring and flap obs. - consider HDU. - involve surgeons in management O2 carrying capacity: - aim for Hct of 30 - this is thought to be cross over of where risk of low Hb and reduced oxygen carrying capacity crosses increased flow from heamodilution. Arterial flow: - aim for hyper dynamic circulation with increased CO, vasodilution, hypervolemia, large pulse pressure. - monitor at least hourly. signs of insufficient arterial flow = immediate surgical r/v. - pulse dopller, white, pale, slow cap refill, cold Do everything you can to induce vasodilution: Fluid status: - hypervolemia will induce V.dilation, hypovolemia will induce vasospasm. - aim for CVP 12 or 5 above baseline. - U output >2mls/kg/hr - risk of excess fluid is tissue oedema that can occlude venous and artery flow. Temp: - aggressive temp management pre, intra and post op. - fluid warmers, blankets, room - want temp > 37 at all times. Pain/sympathetic tone: - adequate analgesia to decrease pain. - regional is especially good to induce selective vasodilation in the free flap area - consider epidural for lower limb, BP block for upper limb. BP: - aim for BP >60 Map using fluid. - avoid vasopressors. CO2: - avoid hypocapnia. Direct pressure and venous outflow: - ensure dressing, pressure etc don't compress site. - elevate to increase venous outflow. - signs of insufficient venous drainage is dark, dusky, oedema, blanches easily. |
