19/11/2023
I get this question from veterinary surgeons and nurses a lot: When I intubate a dog's trachea, the patient coughs a little. That is okay, right? (At least I know it is in the trachea).
Let's go back first to the goals of airway management:
1. Provide effective supportive oxygen therapy (FiO2 ≥ 0.3)
2. Provide a means to monitor pulmonary gas exchange as well as monitoring appropriate application of a technique (FGF) for the selected breathing circuit to prevent inhaling a gas mixture containing CO2.
3. Secure a patent airway irrespective of positioning
4. Provide a protected airway (taking over this function from the functional larynx in awake dogs)
5. Means to support pulmonary minute ventilation
This is best achieved bij placing an endotracheal tube with cuff (low pressure, high volume).
In order to place the ET tube, you were taught the correct method at University.
In practice I encounter a plethora of variations being applied, usually leaving out one or several steps, like no induction agent administered (only premedication), not using a light source/laryngoscope or omitting using a desensitising topical spray on the vocal cords.
With the stepwise approach given below, you will not only maximize success of endotracheal tube placement (on first attempt), but also keep airway and laryngeal trauma or temporary dysphonia to a minimum and postprocedural patient comfort optimal during swallowing and normal use of the larynx.
A. Check the patient file for demographic data, BCS, head/jaw/upper airway trauma/disease/symptoms and/or sleep apnea and previous anaesthetic records (ET tube size placed, remarks made on ease of intubation); Check cliënt adherence to vasted status in planned procedures. Postpone or discuss rapid sequence induction (risks/costs) when non-fasted (not further discussed here)
B. Prepare airway management -less or more elaborately- based on the predicted risks and actual pre-anarsthetic physical exam
C. Prepare 3 sequential ETtube sizes and (also 1 or 2 guarded ET tubes to be placed after CT Scan), do a visual inspection of ALL ET tubes and place them on a clean tissue. Inflate the cuff of ALL ET tubes and leave them for 5 min on the tissue to detect slow leaks of the cuff; do not forget to check tightness of the tube to circuit adaptor as well.
D. Deflate the cuffs prior to premedication or IV cannula placement.
E. Prepare appropriate topical anaesthesia and a laryngoscope, check lightsource/battery with intended blade to be used; Clean/disinfect the blade prior to induction.
F. Induce the patient, pre-oxygenate when still breathing with high flow O2 if not done so already
G.check for jaw tone and introduce the laryngoscope GENTLY to visualize the larynx. Assess laryngeal motility
H. Spray the larynx in this stage already if possible, and take the size of the rima glottis.This requires no slime/foreign matter being present of course.
I. Allow further increase of anaesthetic depth by allowing time or fractioned dosing of induction agent (continue pre-oxygenation even when not breathing)
J. Perform a full oropharyngeal inspection using the laryngoscope (do not forget to inspect under the tongue). Inspect and desensitize the laryngeal mucosa first, if not already done under H.
Remove any foreign matter using suction first, before desensitizing the larynx.
K. REMOVE/retract your laryngoscope when distracted or reaching for the ET tube
L. Check anaesthetic depth, type/rate of breathing and mucous membrane colour.
M. Place an appropriate size ET tube between the vocal cord, retract the laryngoscope and assess correct position of the ET tube by:
1. Observing tidal appearance of condensation during expiration (after manual breath if apneic) -note: coughing is NOT a desired assessment technique!)
2. Feel with your own cornea (very sensitive detector) that air flows TROUGH the lumen -note, the cuff is NOT inflated untill correct position is confirmed). Let an assistant gently yet briefly and quickly apply pressure on the thorax in non breathing patients to generate flow.
3. Connect the breathing circuit (O2 flow 1-2L/min depending on patient size
4.generate 20 hPa of in circuit pressure by squeezing the reservoir af and listen of air escaping alongside the ET tube.
5. Inflate the cuff gradually during the next 2 squeezes to 20hPa untill no leak is heard anymore
N. Fix the position of the ET tube to the patient as per local custom
O. Place a capnograph sensor as close to the ET tube as possible and give 3-5 appropriate manual breaths and observe the ETCO2. If going down to almost 0.5kPa (3,2 mmHg) the ET tube is in the oesophagus!
P. After confirming ETCO2 stays above 3.5 kPa (25 mmHg), your ET tube is endotracheally positioned
Q. Auscultate during 2-3 manual breaths ventrally cranial to the heart on the thorax for bilateral breathing sounds. If you do not hear breathing sounds, auscultate the stomach; if no sounds on the right, the ET tube is too far (in the carina).
R. In that latter case, deflate the cuff, retract the ET tube a bit and re-insufflate the cuff. Auscultate again and if satisfactory, refix the position of the ET tube as per local costum.
Primum non Nocere provides critical care, anaesthesia and pain management consultancy for busineses and institutions in the Veterinary field.
