Four Corners Veterinary Symposium August 2017

“Every Breath You Take”

How to Avoid or Manage Anesthetic Airway Disasters Carrie Davis, DVM (AVCAA Board Eligible)

davisdvm04@yahoo.com Objectives: These notes are supplement to my 20 minute lecture & not a complete review. Hope to see you there!

Correct Endotracheal Tube (ETT) Placement Intubation Aids and Techniques Avoiding Tracheal Tears or Rupture

o Endotracheal Tube Options o Endotracheal Cuff Pressure

Avoiding Barotrauma/Volutrauma o Equipment Safety Features/Options

Rebreathing Circle System Mapleson/Non-rebreathing System

Alternative Techniques to Obtain an Airway Other Equipment Safety Features

Is the ETT Correctly Placed? This sounds embarrassingly basic….but the first step in successful airway management, often the culprit!

Visual assessment passing ETT through arytenoids, ALWAYS use a laryngoscope Condensation/fog in tube with breaths Air should move freely through the ETT during spontaneous breaths Chest rise & auscultation of lung sounds during ventilation/breath Capnography waveform observed ETCO2 value observed Bulb syringe ALWAYS require > 1 method for verification of your ETT placement

Suction Bulb:

*Allows rapid assessment *Bulb & adaptor = cheap! *Trachea = bulb immediately re-inflate *Esophagus = bulb generally NOT re-inflate *ALWAYS in conjunction with additional method of confirming ETT placement!

mailto:davisdvm04@yahoo.com

Avoiding Endotracheal Tube & Cuff Trauma

Tracheal Tear:

Clinical signs: Impressive SQ emphysema of cervical region, spreads rapidly Subsequent respiratory distress, secondary to changes described below

Monitoring changes: Depends on severity Shallow breaths (smaller tidal volume), hypercapnia or hypocapnia, hypoxia Changes on capnogram provided in lecture Cardiovascular collapse

Radiographic signs: Pneumomediastinum, possible spread to pneumothorax & retroperitoneal space

Immediate Management: Thoracocentesis to resolve pneumothorax, if present

o Don’t let them die waiting for rads….diagnostic thoracentesis based on clinical signs! o Prepare for possible tension pneumothorax (attend lecture for emx management)

Deflate ETT cuff, re-position tube passing it distal, to level of carina (hopefully below level of tear), or exchange for a new longer ETT if needed, re-inflate cuff gently

If tear extends to carina, difficult to manage

High Risk: Dental procedures Overzealous ETT cuff inflation Multiple position changes

Prevention Techniques: Use high volume, low pressure endotracheal tube cuffs Use guarded ETT when appropriate ALWAYS detach the patient from the circuit before moving or rotating the patient! Secure the ETT to the patient appropriately Careful ETT cuff inflation

o Leak test appropriately o ETT cuff pressure monitoring

Common Endotracheal Tubes:……………&……….Check Cuff Integrity Prior to EACH Use:

Endotracheal Tubes: Cuff Options High Volume, Low Pressure:

PREFERED, minimize risk of ischemic tracheal injury from pressure on tracheal wall Pressure exerted by cuff on tracheal wall = similar to intracuff pressure Allows good estimate of pressure on tracheal wall exerted by cuff PVC Murphy Tubes Cuff is bulky, excess material

↑ likely to leak due to folds in cuff

Low Volume, High Pressure: Intracuff pressure does NOT reflect pressure on tracheal wall

o Pressure exerted on tracheal wall difficult to measure Silicone Murphy Tubes & Reinforced/Guarded Murphy Tubes Cuff is less bulky, smooth

High Volume Low Pressure

Low Volume High Pressure

High Volume Low Pressure

Low Volume High Pressure

PVC Murphy Tube

Reinforced/Guarded Murphy Tube

Silicone Murphy Tube

TRASH!

Endotracheal Tubes: Cuff Pressure, Monitors Perfusion pressure of tracheal mucosa = 25-35mmHg (34-47 cmH2O)

o Recommended cuff pressure range = 18 mmHg-25 mmHg (25-34 cmH2O) If < 18mmHg (< 25cmH20) risk aspiration

Tips: *Use as large of ETT as possible for patient

-↓ amount of air required to inflate cuff *ALWAYS leak test MACHINE prior to intubating -Identify leak as a machine problem vs ETT problem! *Leak test ETT: after intubated, close APL valve, hold pressure to 20 cmH20 & should be no audible leak or pressure drop on manometer -Remember to reopen APL valve! *Leak? Slowly add small amounts to cuff & repeat test *Use ETT cuff pressure monitor *What if reach max ETT cuff pressure & leak remains: -Leak is elsewhere in circuit -Need a larger ETT

Preventing Excess Airway Pressure: Peak Inspiratory Pressure (PIP) Adjustable Pressure Limiting Valve (APL Valve) AKA “Pop-Off” Valve: APL Valve & PIP Manometer: Pneumothorax:

APL Valve

PIP: NEVER Exceed

20 cmH20

APL Valve Purpose: Prevent excess pressure from accumulating in the breathing circle while allowing intermittent

closure for manual ventilation

APL Valve Rules of Use: Remain OPEN in all situations except when patient is on mechanical ventilator

APL Valve Complications: Inadvertent & persistent closure

Outcome: Volutrauma, pneumothorax, &/or failure of venous return = cardiac arrest

Clinical Signs/Monitoring Changes: (Depends on severity) Hope you visualize rebreathing bag is HUGE! May hear hiss of gas leaking around ETT cuff if pressure > 20cmH20 (leak test pressure) Shallow breaths (smaller tidal volume), hypercapnia or hypocapnia, hypoxia Changes on capnogram provided in lecture Cardiovascular collapse

o If using a Doppler, will hear change in shape of pulse sound as stroke volume diminishes… WOOSH, WOOSH, Woosh, woosh, woo, wo, ……..

Immediate Management: Disconnect circuit from patient to relieve pressure, then open APL vale & reconnect

o Do NOT rip the bag off

o Risk ↑ pressure & rupture lungs Thoracentesis if needed, prepare for tension pneumothorax, chest tube placement

↓ tidal volume & ↓ PIP to minimums required to maintain normoxemia & normocapnia If CPR is required, open chest CPR is advised

Prevention of Excess PIP: Commercial high patient airway pressure alarm

o Best solution to detect ↑ airway pressure

o *Audible alarm

o *Requires you to respond/resolve issue

o *Does not relieve pressure, simply alarms

o *No employee exposure to inhalant gases

Commercially available momentary closure valve Separate Momentary Closure Valve: Combo APL Valve & Momentary Closure Valve:

*Can be added to any machine, downstream of APL valve *APL valve remains open = safety (Intermittently depress button to administer a breath) *APL valve must be OPEN for this to be an effective safety device *If APL valve is closed, this does NOT help you at all

Example using a momentary closure valve, permitting APL (pop-off valve) to remain open:

APL Valve Remains

Open

EMD Safety Valve for PIP Pressure Relief o https://www.essentialmedicaldevices.com

Pressure-relief valve, using a commercial PEEP valve o (Cheap version of EMD Safety Valve) o See pictures & description below o *This is an ABNORMAL use of the PEEP valve

*Not to confuse: PEEP Valve: Positive End Expiratory Pressure Valve Intended/proper use of PEEP valve: maintain positive end expiratory pressure in specific situations, & not the topic of discussion today

For clarity, example of NORMAL position & use of commercial PEEP valve, as intended:

*In the expiratory limb *Inflow to PEEP valve is from the expiratory limb of the breathing circuit *Outflow from PEEP valve is through the expiratory 1 way valve *This position will induce PEEP *This position will NOT prevent excess airway pressure build up *PEEP is not the topic of discussion today

PEEP Valve “Normal” Position

https://www.essentialmedicaldevices.com/

Commercial PEEP Valve,*Abnormal Use, Acting as Pressure Relief Valve:

*Cheap prevention of excess airway pressure: purchase 20 cmH20 PEEP valve & adapter *Placed in expiratory limb of breathing circuit, upstream from the APL valve *Inflow from the T piece in expiratory limb, outflow = free flow to ROOM! *Requires this abnormal positioning for pressure relief, *NOT intended purpose of PEEP valve! *Must be positioned as in picture above, or will not vent excess pressure

*No alarm, but immediately releases any ↑ airway pressure

*Response to ↑ pressure = vent airway circuit gas to room, exposes employee to inhalant gases!

APL Valve

PEEP Valve:

Position For

Pressure Relief Use

Prevention of ↑PIP Mapleson/Non-Rebreathing Systems: Type of Mapleson System

o Rubber valve incorporated into the bag (picture to right) o Only cause barotrauma if you physically occluding the valve o Considered safer

No sliding open/close mechanism to be forgotten

Disposable Resuscitation Bag Manometer Cheap, easy to incorporate

ONLY provides protection from excess PIP

o You visualize max 20 cmH20 & STOP manual inhalation

Does NOT protect against accidental APL valve closure!

o If you leave APL valve closed, no alarm, must visualize large

bag & ↑ pressure

Mounting Block, AKA “Bain Block” Attached to machine Fixed connection for non-rebreathing circuit, reservoir bag & scavenge tubing APL valve (“pop-off” valve) Pressure gauge/manometer Can attach the PEEP valve for safety pressure relief valve, as described above!

Manometer

Special Techniques for Managing the Challenging Airway Guide Tube/Stylet Endoscopic Guidance (not discussed in notes) Nasotracheal Intubation (uncommon in small animals, not discussed in notes) Retrograde Intubation Lateral Pharyngotomy Tracheostomy

Guide Wire/Tube/Stylet Intubation:

*When direct visualization of laryngeal opening is not possible or obscured *Abnormal anatomy or positioning *Diameter needs to be smaller than ETT, slide easily *Length: longer than you think! Need to obtain control of wire while passing tube *Blunt end, delicate handling

*Pass wire with visualization,

then pass ETT blindly over wire

ETT Exchanging: Use guide wire/stylet to allow exchange of ETT easily when repositioning is not possible if need to exchange a malfunctioning ETT cuff or improper size ETT

Retrograde Intubation: When direct visualization of glottis impossible

*Pass needle through skin of ventral neck into trachea, between upper tracheal rings *Distal to larynx, but high in trachea *Guidewire maneuvered through needle rostrally into larynx, pharynx & oral cavity *ETT is fed over this guidewire & manipulated into larynx blindly *Once tip ETT in larynx, needle & guidewire removed, ETT passed to position with cuffed end near thoracic inlet *Cuff MUST be caudal to puncture site of needle to avoid forcing gases SQ or into mediastinum during positive pressure ventilation (manual or mechanical)

*SQ emphysema & pneumothorax = COMPLICATIONS, among others

Midcervical Trachea

Max! *Guidewire

Will Need To Be LONGER!

*Guidewire Will Need To Be

LONGER!

Lateral Pharyngotomy: Alternative to tracheostomy (and less invasive) for facilitating surgical procedures of the

mandible, maxilla or oral cavity Improves visualization in surgical field & dental occlusion to aid in reduction of fractures Several technique options, 1 shown here (Photo credit, Rachel Reed):

Hemostats to level desired near angle of mandible: Skin incision over hemostats:

Blunt dissection of hemostats through skin: Grasp ETT with hemostats & pull into oral cavity:

Turn & Feed ETT into Trachea: Proper placement:

Inflate ETT cuff as normal and suture in place with purse string Option to use guarded ETT based on patient size and procedure performed Option to intubate & use that SAME ETT by briefly disconnecting from the circuit, & passing it

out the pharyngotomy site When procedure complete, simply remove ETT, incision heals via second intention

o Blunt dissection is key, only use scalpel to pass through skin layer o Staple or suture skin if you wish, but should just treat it like an E-tube incision

Complications: Damaging neurovascular structures of the region

o External carotid artery, jugular vein, linguofacial vein, maxillary vein, hypoglossal nerve, vagosympathetic trunk of the recurrent laryngeal nerve

Example below: intubated patient, then performed lateral pharyngotomy with new tube & exchanged tubes once performed with aid of laryngoscope

Tracheostomy: Invasive & reserved for patients in which above options are not viable Consider pharyngostomy as first option, if possible Details of placement not topic of lecture today

Complications:

Infection, granulomas, tracheal stricture, cartilage damage, hemorrhage, pneumothorax, SQ emphysema, fistula, dysphagia, malacia

Other Safety Features Advised:

Negative Pressure Relief Valve:

*In inspiratory limb of breathing circuit *On dome of inspiratory 1 way valve *Activated if inspiratory valve is stuck or occluded *Allows patient to inhale room air *Patient will wake up if you do not realize this is happening, as patient is only inhaling room air & NOT machine gases *Protects patient from suffocation!

References “Thank You” for critically reviewing my notes & lecture:

Chris Egger, DVM, MVSc, DACVAA & Rachel Reed, DVM, DACVAA Lumb and Jones. Veterinary Anesthesia and Analgesia. Blackwell Publishing, 2007 & 2015

Disclaimer!

These notes & 20 minute lecture DO NOT provide comprehensive information on topics discussed. This is NOT a lecture on mastering techniques for performing all procedures discussed.

These are simply recommendations & tips for improving patient airway safety.