Ver el código de «Acute respiratory distress syndrome»

==Background==
[[File:Lung and diaphragm.jpg|thumb|Lobes of the lung with related anatomy.]]
*Non-cardiogenic [[pulmonary edema]] due to lung capillary endothelial injury (diffuse alveolar damage)
**Proteinaceous material accumulate in alveoli in a heterogeneous manner (hyalinosis)
*Symptom of an underlying disease

===Causes===
*[[Pneumonia]]
*[[Sepsis]]
*[[Pancreatitis]]
*[[Burns]]
*[[Aspiration pneumonia and pneumonitis]]
*[[Trauma (main)|Trauma]]
*[[Submersion Injuries (Drowning)|Near drowning]]
*[[Fat embolism syndrome]]
*[[Amniotic Fluid Embolus|Amniotic fluid embolism]]
*[[Toxicology (Main)|Overdose]]
*[[Massive transfusion]]
*[[Transfusion-related acute lung injury]]

==Clinical Features==
*Severe [[dyspnea]]
*[[Hypoxemia]]
*Diffuse crackles

==Differential Diagnosis==
*[[Pneumonia]]
*[[PE]]
*[[Diffuse alveolar hemorrhage]]
*[[DIC]]
*[[CHF]]

{{Pulmonary edema types}}

==Evaluation==
[[File:ARDSSevere.png|thumb|Classic ARDS on [[CXR]].]]
[[File:ARDS.png|thumb|ARDS on CXR]]
===Workup===
*[[CXR]]
*CBC
*Chem 10
*[[Urinalysis]]
*[[LFTs]]
*Lipase
*PT/PTT
*[[Influenza]] testing (seasonal)
*Blood cultures
*[[Lactate]]
*Consider bedside [[echocardiography|echo]]
*Consider [[ABG]]/[[VBG]]
*Consider [[BNP]]

===Diagnosis===
*'''Risk factors and origin of edema''' 
**Precipitated by an acute predisposing risk factor, such as pneumonia, nonpulmonary infection, trauma, transfusion, aspiration, or shock. Pulmonary edema is not exclusively or primarily attributable to cardiogenic pulmonary edema/fluid overload, and hypoxemia/gas exchange abnormalities are not primarily attributable to atelectasis.
*'''Timing'''
**Acute onset or worsening of hypoxemic respiratory failure within 1 week of the estimated onset of the predisposing risk factor or new or worsening respiratory symptoms.
*'''Chest Imaging'''
**Bilateral opacities on chest radiography and computed tomography or bilateral B lines and/or consolidations on ultrasound

====Diagnostic Criteria<ref name="Matthay"> Matthay, M. et al. (2024). A New Global Definition of Acute Respiratory Distress Syndrome. American Journal of Respiratory and Critical Care Medicine, 30(1), 37-47. https://doi.org/10.1164/rccm.202303-0558WS </ref>====
*'''Nonintubated ARDS'''
**PaO2:FiO2 ≤ 300 mm Hg or SpO2:FiO2 ≤ 315 (if SpO2 ≤ 97%) on HFNO with flow of ≥ 30 L/min or NIV/CPAP with at least 5 cm H2O end-expiratory pressure
*'''Intubated ARDS'''
**Mild: 200 < PaO2:FiO2 ≤ 300 mm Hg or 235 < SpO2:FiO2 ≤ 315 (if SpO2 ≤ 97%)
**Moderate: 100 < PaO2:FiO2 ≤ 200 mm Hg or 148 < SpO2:FiO2 ≤ 235 (if SpO2 ≤ 97%)
**Severe: PaO2:FiO2 ≤ 100 mm Hg or SpO2:FiO2 ≤ 148 (if SpO2 ≤ 97%)
*'''Modified Definition for Resource Limited Settings'''
**SpO2:FiO2 ≤ 315 (if SpO2 ≤ 97%). Neither positive end-expiratory pressure nor a minimum flow rate of oxygen is required for diagnosis in resource-limited settings.

==Management==
===General Care===
*Treat underlying cause
**Cover for [[sepsis]]
***[[Pneumonia]] in addition to other identified source
**[[Tamiflu]] 75mg BID oral or NGT if influenza season <ref>http://www.cdc.gov/flu/professionals/antivirals/summary-clinicians.htm</ref>

===Pulse Dose [[Steroids]]===
*Consider in early, established, severe ARDS in ICU setting<ref>Khilnani GC and Hadda V. Corticosteroids and ARDS: A review of treatment and prevention evidence. Lung India. 2011 Apr-Jun; 28(2): 114–119.</ref>
**'''NOT''' for prevention of ARDS (will increase risk for ARDS and worsening sepsis if not in ARDS already)
**In theory, may reduce fibro-proliferative inflammatory changes during exudative phase (< 1 wk)
**No benefit to starting in late ARDS (> 2 wks)
*Meduri protocol (21 vs. 43% mortality)<ref>Meduri GU, Golden E, Freire AX, Taylor E, Zaman M, Carson SJ, et al. Methylprednisolone infusion in early severe ARDS: Results of a randomized controlled trial. Chest. 2007;131:954–63.</ref>
**1mg/kg loading dose [[methylprednisolone]]
**Followed by infusion of 1mg/kg/day from day 1-14
**Then 0.5mg/kg/day from day 15-21
**Then 0.25mg/kg/day from day 22-25
**Finally 0.125mg/kg/day from day 26-28

{{Lung Protective Ventilator Settings}}
{{Lung Protective FiO2 and PEEP Scale}}

===Additional [[Ventilation (Main)|Ventilation]] Considerations===
*Permissive hypercapnia
*Maintain plateau pressures < 30 <ref>Hansen-Flaschen et al. Acute respiratory distress syndrome: Clinical features and diagnosis.UpToDate accessed 3/26/14</ref>
**Driving pressure (plateau pressure minus PEEP) <14 is most strongly associated with decreased mortality<ref>Amato MB, Meade MO, Slutsky AS, et al. Driving pressure and survival in the acute respiratory distress syndrome. N Engl J Med. 2015;372(8):747-755. doi:10.1056/NEJMsa1410639</ref>
*Ensure adequate [[sedation]]
**Better synchrony with vent
**Decreased oxygen consumption
**Less [[delirium]]
**Increased patient comfort
*Prone ventilation <ref>Guerin, C. (2014) ‘Prone ventilation in acute respiratory distress syndrome’, European Respiratory Review, 23(132), pp. 249–257.</ref> 
**Increases survival for severe ARDS
**Consider for refractory hypoxemia
**Many consider this a type of [[recruitment maneuver]]
*Consider [[Airway pressure release ventilation]] (APRV)
*[[Pressure control ventilation]] ([[PCV]]) if acidosis with APRV
**Attempt to maintain same rate
**Maintain same Pmean
*[[PRVC]] or [[Volume control ventilation]] with paralysis to prevent barotrauma in breath stacking and vent dyssynchrony<ref>Gainnier M, Roch A, Forel JM, et al. Effect of neuromuscular blocking agents on gas exchange in patients presenting with acute respiratory distress syndrome. Crit Care Med. 2004;32:113-119.</ref><ref>Papazian L, Forel JM, Gacouin A, et al. Neuromuscular blockers in early acute respiratory distress syndrome. N Engl J Med. 2010;363:1107-1116.</ref>
**[[Cisatricurium]] loading dose 0.15 mg/kg, followed by 1-3 mcg/kg/min
**Titrated to less than 2 twitches in train of four
**Cisatricurium preferred to pancuronium in renal impairment
**Cannot use paralysis with APRV
*[[Recruitment maneuver]]
**Varying methods and protocols
**Controversial in risks and benefits

===Adjuncts===
*Evidence of [[pulmonary hypertension]]
**[[Inhaled nitric oxide]] ([[iNO]])
**[[Epoprostenol (prostacyclin)]]
*[[ECMO]]
*[[Oscillation ventilation]], [[High frequency oscillation ventilation]] ([[HFOV]])


==Medication Dosing==
{{MedicationDose
| drug = Methylprednisolone
| dose = 1mg/kg load, then 1mg/kg/day (d1-14), taper over d15-28
| route = IV
| context = Pulse-dose steroids for early established severe ARDS (Meduri protocol)
| indication = Acute respiratory distress syndrome
| population = Adult
| notes = NOT for prevention; no benefit if started >2 weeks into ARDS
}}
{{MedicationDose
| drug = Cisatracurium
| dose = 0.15mg/kg load, then 1-3mcg/kg/min
| route = IV
| context = Neuromuscular blockade to prevent barotrauma/vent dyssynchrony
| indication = Acute respiratory distress syndrome
| population = Adult
| notes = Titrate to <2 twitches in train of four; preferred over pancuronium in renal impairment
}}

==Disposition==
*Admit to ICU

==Prognosis==
===Severity (Berlin Definition)<ref name="Ferguson"> Ferguson ND et. al. The Berlin definition of ARDS: an expanded rationale, justification, and supplementary material. Intensive Care Med. 2012 Oct;38(10):1573-82.</ref>===
{| class="wikitable"
| align="center" style="background:#f0f0f0;"|'''PaO2/FiO2'''
| align="center" style="background:#f0f0f0;"|'''Severity'''
| align="center" style="background:#f0f0f0;"|'''Mortality'''
|-
| 200-300||Mild||27%
|-
| 100-200||Mod||32%
|-
| <100||Severe||45%
|- 
|}

==See Also==
*[[EBQ:ARDSnet Trial]]
*[[Pulmonary edema]]

{{Mechanical ventilation pages}}

==External Links==
*[http://www.ardsnet.org/files/ventilator_protocol_2008-07.pdf ARDSnet Ventilator Settings]
*[https://resusreview.com/2013/aprv-ventilation-mode-introduction-basic-use-management-and-advanced-tips/ APRV / BiVent]

==References==
<references/>

[[Category:Pulmonary]]
[[Category:Critical Care]]