Thread by @Pradipsedation

1.A primer on airway obstruction in #Sedation @pedsedation @PediAnesthesia @hyguruprep #MedTwitter
Lets focus on hypo-pharyngeal collapse & Laryngospasm
First lets review the Starling resistor model for airway obstruction (Butler JP et al. J Physiol. 2013 May 1;591(9):2233-4)

2. The nasal & tracheal structures support a collapsible segment-supraglottic area (CN IX, X & XII innervation).Sedatives inhibit tone of this segment with propensity to collapse more. The collapse can be exacerbated by diaphragmatic contraction (inspiratory negative pressure).

3.Supraglottic segment thus acts like a Starling resistor as its caliber is affected by pressures within the lumen. Loss of tone from sedation +negative pressure narrows the AP distance between the posterior pharynx & soft palate, epiglottis. @agstormorken @Pedisedationdoc

4. Airway obstruction during sedation occurs in the
supraglottic structures primarily due to the soft palate & epiglottis “falling back” to the posterior pharynx.
Reber, A., et al.Anesthesiology, 1999. 90(6): p. 1617-23.
Litman, R.S. Anesthesiology, 2005. 103(3): p. 453-4.

5. Is base of the tongue - the primary cause of upper airway obstruction during unconsciousness? No. Recent MRI studies of the upper airway in children suggests that the soft palate & epiglottis are the most likely structures causing pharyngeal obstruction.

6. Hypo-pharyngeal collapse (pharyngeal obstruction) is the most common type of airway obstruction during sedation. Simple airway maneuvers like a chin lift/jaw thrust, CPAP are often sufficient to relieve the airway obstruction related to pharyngeal collapse.

7. Hypopharyngeal collapse, which usually presents as "snoring" (sometimes appears stridulous) type of noise heard immediately after patient enters state of moderate- deep sedation. Resist temptation to suction. Reposition, + jaw thrust & CPAP with anesthesia bag & mask.

8. With airway reposition + Jaw thrust +/- CPAP: patients should rapidly improve. Next we look at obstruction at glottis. @doccarmen1 @tarhealer @areinamo21 @yoncabulutmd @freckledpedidoc @pccm_doc @DeannaMarie208 @EmoryAnesthesia @DrBudde21 @KerrynRoome @DryerBecca @magod_b

9. Laryngospasm happens at level of glottis (# 2 in fig above).
It is glottic musculature spasm & may result in partial or complete airway obstruction. Risk factors for laryngospasm include upper airway secretions, airway manipulation, recent URI, GERD, exposure to tobacco smoke,

10. young age & higher ASA-PS status. Additionally, the contribution of inhaled anesthetics to laryngospasm or use of lidocaine for prevention- provide conflicting evidence.
Harounian J. et al. Medications & Larynx. Curr Opin Otolaryngol Head Neck Surg. 2019 Dec;27(6):482-488

11. A meta-analysis by Bellolio F et al. BMJ Open. 2016 Jun 15;6(6):e011384 reported a higher incidence of laryngospasm with ketamine. A 0.3% incidence of laryngospasm can occur with ketamine as an idiosyncratic response (Green SM et al.Ann Emerg Med. 2009;54:158Y168.e1Ye4.).

12. Melendez et al (Pediatr Emerg Care. 2009;25:325Y328.). reported a higher incidence with intramuscular use of Ketamine.

13. Simple airway maneuvers DO NOT reverse laryngospasm. Mgment. of laryngospasm requires a stepwise approach, which may require positive pressure ventilation, deepening the depth of sedation (i.e more propofol) & in extreme circumstances neuromuscular blockade. Brief approach-

14. Recognition of laryngospasm (initially inspiratory stridor -may progress complete airway obstruction):
1) No air entry by auscultation despite chest movement/respiratory effort (tracheal tugging etc.)
2) Loss of EtCO2 waveform followed by SPO2 drop and then bradycardia etc.

15. As pointed above: airway maneuvers (repositioning, suctioning, jaw thrust, placement of oral or nasal airway) will NOT relieve the obstruction.
Team approach is needed: Designate a person to bag-mask, deepen anesthesia (use propofol), try laryngospasm (Larsen) maneuver.

16. Laryngospasm (Larsen) maneuver:

Larson CP Jr. Laryngospasm -- the best treatment. Anesthesiology 1998;89:1293-1294

17. If everything fails: Use succinylcholine choline (SC) (with atropine). SC: IV, IM, IO or intra-lingual. Support ventilation with 100% O2. Intubation may be still required especially with development of pulmonary edema etc.
@pccm_doc @DrKJeffries @SapnaKmd @ChrisCarrollMD

18. We don't keep SC in our emergency drug box (glycopyrrolate, naloxone, flumazenil & rocuronium). So we will use rocuronium especially at offsite locations. Sugammadex should be considered after spasm is broken to reverse rocuronium. @sedationccls #Anesthesiology @SMukkamalaMD

19. Lastly: Train for such high risk scenarios frequently using simulation etc. (Hollman G. et al. Development, implementation, and initial participant feedback of a pediatric sedation provider course. Teach Learn Med
. 2013;25(3):249-57.) Learn more at:
pedsedation.org/offerings/upco…

If folks have suggestions, comments or clinical pearls please add to this OR correct if I am wrong. @agstormorken @MaryLandrigan @AmberPRogers @Pedisedationdoc @doccarmen1 @hyguruprep @areinamo21 @VSLanziotti @freckledpedidoc @PHMConf #medtwitter @pookul99 @tony_breu @PEMTweets