Status Asthmaticus

Medical management:
-O2, fluids*
-bronchodilators, magnesium
-heliox if NOT hypoxemic (using heliox means proportionally less FiO2)
-epi IM 0.01 mg/kg OR dirty epi drip
-BiPAP: 10 IPAP / 3-5 PEEP (EPAP) (aka “ZEEP”. When pts begin tiring out, inspiratory pressure support helps move air in and out)

*Note:
-hypoxemia is a LATE finding in asthma – give O2 EARLY to promote pulmonary vasodilation
-“normal” pCO2 on blood gas = pt tiring out (compensating pts will have low pCO2 as they hyperventilate to blow off lactic acid)
-these pts are severely volume-depleted due to insensible losses – need fluids! (30cc/kg)
-lung ultrasound has primarily A lines (no interstitial fluid)
-these pts can tolerate hypercapnea and acidosis

Absolute indications for intubation:
-deteriorating consciousness
-respiratory muscle fatigue nonresponsive to BiPAP
-cardiac/respiratory arrest

Avoid intubation as it does nothing to fix the underlying problem of bronchoconstriction and increases risk of hyperinflation.

Intubation:
-use DSI with ketamine 1-2 mg/kg*. Choose roc for longer paralysis to prevent vent asynchrony
-hyperinflation (due to breath-stacking) is your enemy — increased airway pressures = risk for tension PTX, decreased venous return and thus cardiac output
-strategy = permissive hypercapnea Рto allow for full exhalation:
—-RR 6-8 breaths/min, TV 6cc/kg, <5 PEEP, inspir flow rate 100-120 L/min

Subdissociative dose ketamine 0.5-1 mg/kg

The Deteriorating/Coding Intubated Asthmatic:
-disconnect from vent, allow exhalation (may push on chest), and slowly bag at 6 breaths/min
-if no improvement and see breath-stacking on vent, needle decompression / finger thoracostomy
-DOPES: Displaced tube (use VL or bronchoscope to confirm), Obstruction (pass suction catheter, look for kinking of tubing), T-PTX, Equipment problem, Stacked breaths
-VV ECMO

Vent Settings & Supplemental O2

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General Vent Concepts
-oxygenation: PEEP, FiO2
-ventilation: TV, RR

-PEEP = alveolar recruitment (oxygenation)
-RR = time to exhale (ventilation)
-TV = 6-8mL/kg IBW (ideal body weight) — titrate to protect alveoli (baby lungs)

NIV
-IPAP/EPAP = 10/5
-EPAP = PEEP (recruitment/oxygenation)
-IPAP = pressure control (PC) over PEEP (PC minus PEEP = TV) – increasing IPAP (PC) without changing PEEP increases TV (ventilation)

 

Initial Vent Settings

Nonobstructive process:
-PEEP 5
-RR 16 or higher if metabolic acidosis…..MICU: after paralyze, initially ventilate at RR 25-30 to blow off acid accumulated during apneic period

Obstructive (asthma/COPD):
-ZEEP (zero or minimal PEEP/EPAP) with high IPAP (promote air movement for fatigued respiratory muscles)
-low RR (10)

ARDS (baby lung):
-400-450 mL males; 350-400 mL females (4-6 mL/kg IBW)

 

Post Intubation
-bring initial RR to 25-30 – to blow off CO2 accumulated during apneic period
-fentanyl drip, then assess for further need for sedation if tachycardic or diaphoretic (neuromuscular blockade only affects nicotinic/motor receptors)

Check for autoPEEP: hold “expiratory hold”
Check plateau pressure: hold “inspiratory hold”

 

FYI
-prior to intubation of severely acidotic pt, consider giving several bicarb pushes OR bagging pt during apneic period – to prevent pt from coding during apneic period from severe acidosis