Intubation

Procedure for Endotracheal intubation: sterile cockpit environment. More than 40% of adverse outcomes result from human factors.

Source: Difficult Airway Society Guideline 2015. doi: 10.1093/bja/aev371

• prepare the patient: assess for indicators of difficult airway, reliable IV/IO access, optimize position (wedge if obese), find cricothyroid membrane, optimise hemodynamics e.g. for shock, consider C-spine protection

• prepare the equipment: drugs, equipment

• prepare people: allocate the roles of 1st intubator, 2nd intubator, who to apply cricoid force, who to pass ETT tube, who to push drugs, who to monitor the patient, who will scribe/track time, who will perform FONA if needed. Who we call for help. Consider location around the patient.

• Verbalize the plan: "Airway plan is": Plan A (Drugs and Laryngoscopy), Plan B and C (second incubator after 3 attempts, superglottic vs facemask), Plan D (FONA/Scalpel-bougie-tube)

• preoxygenation

• pretreatment (e.g. fentanyl if needed)

• paralysis and induction

• placement with proof steps, confirmation with ETCO2

• postintubation management

More thoughts here: https://emcrit.org/pulmcrit/10-pearls-from-the-levitan-airway-course/

##Steps:

• Look in mouth (insert glidescope midline),
• look at screen (insert past uvula to epiglotis, then forward),
• look in mouth (while inserting ETT from corner of mouth and rotating midline),
• then look at screen (to insert through vocal folds, retract style with thumb before passing into the airway).

Equipement:

Glidescope vs DL

Glidescope - blade has more angulation than Mac blade (easier view, harder to pass ETT). Only need grade 2 view (grade 1 = will often cause too much distortion.

• can now use Mac blade glidescope either for DL (with attending seeing VL). Placed into velecula so that epiglottis is visualized.

• Mac (curved) vs Miller (straight) - Miller goes straight past epiglottis and hooks it out of the way -> straight view through cords.

• working suction (Yankauer suction tip = stiff, large intake)

• ETT tube with cuff checked (x2) and attached syringe

• Bougie

• Stylet

• Supraglottic airway

• OPA/NPA

• BVM with PEEP valve

• Front of neck access set (blade, bougie)

• ETCO2 monitor

Rigid Stylet = for hyper-angulated blade. Malleable Style = for DL [ ] Mac blade VL?

Sniff position for both DL and VL

Rapid Sequence Induction

Definition: unresponsiveness (induction agent) and neuromuscular relaxation simultaneously. Traditionally - this meant no ventilation.

Use: minimize risk of aspiration, need for immediate control.

Modified RSI

same as above, except with pre-oxygenation (often with OPA and BVM to maximized FRC. Although BiPAP or HFNC can work) ahead of time. This is the most common current approach.

Delayed Sequence Intubation

Use: RSI leads to significant hypoxemia because they can't be pre-oxygenated or need to do something (e.g. insert NG tube) that they won't tolerate prior.

e.g. someone who is too agitated to be effectively ventilated.

Worry: will increase risk of aspiration

• head up
• induction agent but with the intent of keeping them ventilating (e.g. ketamine 1-2mg/kg. though Dr. Bott suggests a lower dose to avoid making them go apneic - e.g. 20mg ketamine)
• pre-oxygenated (as above)
• administer neuromuscular blocks (e.g. rocuronium 1.2 mg/kg IV)
• intubate

Pre-oxygenation

Use: Extend safe-apnea time (SaO2 > 88%) by flushing nitrogen out of the lungs (so SaO2 = 100% does NOT mean adequately pre-oxygenated) . In OR can assess ETO2 to ensure preoxygenated. ~8 minutes in health who is preox (vs 1 minute without), less if ill.

• head up, wedge if obese
• place NC at 6 to 15L (for some apneic oxygenation), leave HFNC in place if already on (has been shown to increase nonhypoxic apneic time in obese patients).
• use BVM at w/ 15 L/min O2 for 3m+, or face mask

Oxygenation

• if someone is large / may be hard to ventilate, but already desaturating... consider putting in an LMA to be able apply more PEEP to recruit (can also blind intubate thru LMA with 90% success rate - higher in obese patients. Use bronchoscope if still worried and intubating through LMA)

• often after intubation - weigh risk of high peep / recruitment with dropping venous return / increasing RV afterload.

Ways to avoid aspiration / Peri-intubation risk

Prevention (still a risk with all intubations, even when NPO because gastric emptying is variable. Can use US to assess)

• keep some height to the head of the bed
• wait the full 55-60 seconds for paralysis to insert blade (no gagging)
• insert an OPA or NPA before doing any bagging - with gentle pressure.
• if using cricoid pressure - pressure must be on the cricoid ring itself (not larynx or trachea - those aren't circumferential).
• NG tube before? doesn't fully empty the stomach so no risk reduction unless there is a compressed stomach (e.g. SBO, gastroparesis and distention) in which case it may be ok if they can protect their airway if they vomit while inserting.

####Access

• Peripheral usually OK
• IO is an option, however the infusion can be quite painful. Consider use of adjunctive lidocaine though the I/O first to avoid this.
• is there time to put in a central line first to ensure access?

Upmost importance to have reliable access. Make sure meds going through the line that is flushing/drawing easiest.

Drugs

pretreatment, induction, paralytic. Summary

• fentanyl 2-3 mcg/kg IV (sympathomimetic, neuro/vascular protection for MI/Stroke/Dissection)
• induction agents - sedative/hypnotics (ketamine 1.5-2 mg/kg IBW = dissociative, Etomidate (0.3-0.4 mg/kg TBW, fent 2-10 mcg/kg TBW, propofol 1.5-2.5 mg/kg TBW)
• defasciculating dose of non-depolarizing neuromuscular blocker (0.1-0.12 mg/kg rocuronium or 0.01 mg/kg vecuronium) - can be reversed by sugamedex if needed

####Sedative/hypnotics Indication:

• use to provide comfort
• prevent HTN/tachycardia
• prevent intracranial HTN (from pain/glottic stim)

Ketamine

• 1.5 mg/kg. Rapid onset/short duration of effect.
• Dose dependent negative inotropy (patient may counteract with endogenous catecholamines - though in extremis they are often catacholamine depletion)
• may or may not increase ICP, but does increase cerebral metabolism

Etomidate

• 0.3 mg/kg
• rapid onset, short duration of effect
• minimal, if any, dose-dependent hemodynamic effect. Reduces ICP and CMRO2.
• Adrenal suppression with single dose? Not sure. Definitely happens if you use it as a gtt for sedation (which is why this is not done)

Midazolam

• previously used more. Dose 0.15 mg/kg (10mg). Longer action
• moderate dose-dependent hemodynamic effect. Reduces ICP and cerebral metabolic rate

Propofol

• 2 mg/kg (150mg). Rapid onset and very short duration of effect (gone in 10 minutes).
• anti-emetic and bronchodilator, reduces ICP and cerebral metabolism.
• profound hemodynamic effects: hypovolemia or heart failure

Paralytics / Neuromuscular blockers

Paralyze voluntary muscle (not cardiac or smooth muscle), including vocal cords and diaphragm.

History: in old days, used to avoid paralytics because it was thought that by avoiding respiratory arrest, failure to pass ETT would not be as big of a problem. However, this did not pan out because it also makes it much harder to bag.

Indication: Use always unless they have no brain stem function.

• prevent active vomiting (though not passive regurgitation) and laryngospasm.
• to facilitate BVM or laryngoscopy.

#####Rocuronium Dose: 1.2 mg/kg Onset: 50 seconds, Duration: 45-60 minute duration of effect (need to cover this long tail - ICP goes through the roof) No CV/ICP effects, no contraindications.

#####Succinylcholine Onset: 50 seconds, duration: 8-10. Dose: 1.5 mg/kg but dose-response curve is wide. No CV effect or insignificant ICP effect. Malig. Hyperthermia risk, raises K by 0.5-1 mEq for 10 minutes (as cells repolarize), thus don't use if K < 5.0 or chronic denervation injury (e.g. hemi/para/quadriplegia - more ACh receptors), large burn, rhabdo.

##Adjuncts Lidocaine - anesthesia does always. Avoids burn of infusion, and has some general anesthetic effect. 100mg dose right before you push the sedative hypnotic.

Fentanyl - anesthesia does always. 100 mcg. Be aware that dose-response is widely variable and this can cause apnea in folks who are sensitivity.

Dexmedetomidine - adjunct for awake intubation or to facilitate pre-oxygenation in AMS. 10-20 mg IVP

Peri-intubation arrest

Incidence 2-5% Usually PEA Usually <6 minutes after intubation 50% mortality

Risk factors: High BMI, SaO2 <92% despite pre-oxygenation (desat->arrest time is short), SBP <90 or Shock index > 0.9, failure to use pre-intubation checklist.

Difficult Airway

• consider awake intubation with ketamine, video-assisted laryngoscopy (glidescope)
• After 3 attempts at DL/ VL: declare this a failed airway.
• supraglottic (king or LMA) airway recommended in intubation fails while next steps arranged.
• +1 attempt at DL/VL by more experience operator, consider maximum 2 attempts intubating through a different method.
• if can't oxygenate and can't ventilate at any point: Declare CICO and procede to scalpel cricothyroidotomy (front of neck access)

Scalpel cricothyroidotomy

Put in an LMA

• find (or have previously marked) the cricothyroid
• insert 10 blade scalpel with dominant hand, blade toward operator.
• rotate blade 90 degrees and pull toward operator
• insert bougie on far side of blade and in to trachea
• insert ETT over the top of the blade
• if obese and cricothyroid cartilage is not identifiable, perform a vertical skin incision followed by manual dissection of tissue is required.

####How to predict the difficult airway

Source: doi:10.1001/jama.2018.21413

#####History

• history of difficult intubation
• snoring (+LR 3.4, -LR 0.65)

#####Exam

• poor mandibular range via Upper Lip Bite test (inability to bite any part of lip = +LR 14, ability to bite vermillion border = -LR 0.42)
• cervical spine mobility via sternomental distance (impaired = +LR 4.2, -LR 0.77)
• interincisor gap (mouth opening capacity. +LR 3.6, -LR 0.71) - difficult to assess mallampati in ICU because patients need to be able to take the sniffing position and open their mouth without saying ahh.

#####Setting

• hypoxia at time of intubation
• inexperience operator
• MAHOCA score

##Specific Cases

Considerations in Shock

Loss of negative pressure ventilation is main driver (not medication) in most hypovolemic folks. Also, loss of catecholamine tone.

• use titrated dose of induction agent to avoid hemodynamic compromise - 1/2 dose in elderly or patients with AMS. (also, perhaps smaller Vd in shock)
• ketamine is least cardio-depressing
• avoid apnea worsening acidosis
• resuscitate before you intubate (decrease preload switching to positive pressure ventilation)
• consider no sedative hypnotic for patients in extremis

Cervical injury

-anterior C collar off (need to access neck and open mouth) -someone holding in-line stabilization (not traction) to not allow movement -use Glidescope (bronchoscope and LMA as backup)

Severe PAH

-quick (avoid prolonged hypoventilation - increase vasoconstriction in lung) -use systemic vasoconstrictors and inotrope infusion (since they will lose tone - e.g. NE for MAP 75-80 to allow adequate coronary perfusion pressure and 0.3 milrinone for 10 minutes) -Admin Flolan 8ml/hr = max via mask to reduce PVR as much as you can -smaller dose of sedative hypnotic and full dose roc. you need some baseline catacholamine/inotropic tone so avoid high dose sedative.