Management of ARDS and Concurrent COVID-19 Infection

The purpose of this article is to review the ARDSnet protocol for management of ARDS with concurrent COVID-19 infection.

As of April 18th, 2020, the current confirmed positive cases of COVID-19 is 739,998 with 39,928 deaths (Google News, 2020).

Most patients with COVID-19 present with cough (65-80%), fever (45% and 85% febrile during illness), and SOB (20-40%).  A small percentage of patients experienced GI and URI symptoms.  Approximately 5-10% of patients that have COVID-19 require intensive care admission and mechanical ventilation (Poston, 2020).

The most common and severe complication of COVID -19 is acute hypoxemic respiratory failure or acute respiratory distress syndrome (ARDS), requiring oxygen and or mechanical ventilation.  

ARDS

ARDS is an inflammatory process in the lungs that produce bilateral peripheral pulmonary edema.  The consequence of this inflammatory process is profound hypoxemia, decreased lung compliance, and increased V/Q mismatching.  There is severe inflammatory injury to the alveolar capillary barrier, destruction of type II pneumocytes leading to surfactant depletion, and loss of aerated lung parenchyma. The occurrence of ARDS with COVID-19 varied between 17% and 41% (Villar, 2020).  Patients with severe ARDS confront a mortality rate between 40-45% and for those that survive, there is significant health and psychological issues (Papazian et al, 2019).   

The Berlin definition aids in the diagnosis of ARDS, which includes the onset between exposure and the development of ARDS must be within 7 days, a PaO2/FiO2 ratio of less than or equal to 300 with a minimum PEEP of 5cmH2O, and the presence of bilateral infiltrates on CXR that cannot be explained by effusion, collapsed lung, or lung nodule (Amin & Amanda, 2017).  The CXR looks like pulmonary edema, however the nature of the pulmonary edema must not be cardiogenic (left atrial hypertension).  ARDS can be classified as mild, moderate, or severe based on the PaO2/FiO2 ratio.  Mild ARDS is a PaO2/FiO2 </= 300 but >200; moderate ARDS is a ratio of 100-200; and severe ARDS is a ratio of <100.

ARDS Protocol

For adult COVID-19 patients who have ARDS, the ARDSnet protocol helps guide ventilator management.   Here’s a synopsis of the ARDSnet protocol:

  1.  Calculate the patients predicted body weight (PBW)
    1. Males: 50 +2.3 [height in inches – 60]
    1. Females: 45.5 + 2.3 [height in inches – 60]
  2. Select your choice of ventilator mode
  3. Set the tidal volume to achieve 8ml/kg PBW
  4. Reduced the tidal volume by 1ml/kg at intervals </= 2 hours until tidal volume is 6ml/kg PBW
  5. Set initial ventilator rate to approximate baseline minute ventilation (do not exceed 35bpm)
  6. Adjust the tidal volume and RR to achieve a pH and plateau pressure goals to </=30cmH2O.  There are suggestions for keeping plateau pressure within goal.  See attached link for ARDSnet protocol.

Note:  

  1.  Minute ventilation = RR x tidal volume (ex. 70kg male, at 8ml/kg: Vt = 560ml x 16RR = 8.9LPM)
  2. Plateau pressure = pressure when there is no gas flow (at the end of inspiration), measurement of the static compliance of the entire lung (high plateau pressure = poor compliance in the lungs like ARDS)
  3. Peak airway pressure = pressure in the proximal airway, resistance in the airway.

The oxygenation goal is a PaO2 55-80mmHg, SpO2 88-95%.  It is important to utilize a minimum PEEP of 5cmH20 and consider use of incremental PEEP/FiO2 combinations to achieve oxygenation goal.  The ARDSnet protocol provides the practitioner with a choice of utilizing lower PEEP/higher FiO2 or higher PEEP/lower FiO2.  

The patient may not be able to maintain his/her pH within the normal range due to the severity of lung injury.  The pH goal is between 7.3 to 7.45; however, in the case of respiratory acidosis defined as a pH 7.15 to 7.30, the RR maybe increased up to 35bpm.  However, if the pH remains less than 7.15, increase tidal volume in 1ml/kg incremental steps until pH >7.15, recognizing that the plateau pressure of 30cmH20 may be exceeded.  In the event that the pH >7.45, decrease the ventilator rate, provided that the tidal volume is 6ml/kg.

Surviving Sepsis Campaign (SSC)

For patients with severe ARDS, the Surviving Sepsis Campaign (SSC) recommends proning the patient 12 to 16 hours versus no proning. Also, in cases where the patient experience ventilator dyssynchrony, intermittent doses of neuromuscular blocking agent are preferred over continuous infusion.   However, it is important to ensure that the patients are adequately sedated with Propofol and/or Dexmedetomidine prior to institution of neuromuscular blocking agents, as they have no amnestic properties.  For patients with severe ARDS, the SSC recommend the administration of corticosteroid in selected patients (Poston, 2020).

With respect to hemodynamic support, the SSC recommend a conservative fluid administration strategy and to utilize crystalloids over colloids.  If the patient is not fluid responsive, the use of Norepinephrine is considered the first-line vasoactive support, followed by Epinephrine or Vasopressin.  

ECMO

There are discussions as to whether venovenous (V-V) ECMO could be utilized as a rescue therapy for patients with severe ARDS.  Henry and Lippi (2020) performed a pool analysis on various studies and concluded that ECMO does not seemingly produce neither harm or benefit in COVID-19 patients progressing to ARDS. The ECMO pool analysis indicate poor survival rate.  Of the 17 patients placed on ECMO, only one patient survived.  However, the sample size (n=17) was low and more research is needed to assess the effectiveness of ECMO in ARDS and concurrent COVID-19 infection.

In conclusion, ARDS with concurrent COVID-19 infection is managed similarly to patients with ARDS. There are many recommendations and investigational therapies; however, four interventions are strongly recommended: low tidal volume, limitation of plateau pressure, no high frequency oscillatory ventilation, and proning.  Please click on the ARDSnet hyperlink to open the mechanical ventilation protocol summary (http://www.ardsnet.org/files/ventilator_protocol_2008-07.pdf).

References:

Amin, Z. & Amanda, A.  (2017).  Comparison of new ARDS criteria (Berlin) and old criteria (AECC) and its application in country with limited facilities.  Journal of General and Emergency Medicine.  2(1).  Retrieved from https://scientonline.org/open-access/comparison-of-new-ards-criteria-berlin-with-old-criteria-aecc-and-its-application-in-country-with-limited-facilities.pdf

ARDS Clinical Network.   (2014).  Mechanical ventilation protocol summary.  Retrieved from http://www.ardsnet.org/files/ventilator_protocol_2008-07.pdf

Google News.  (2020).  Retrieved from https://news.google.com/covid19/map?hl=en-US&gl=US&ceid=US:en

Henry, B. M., & Lippi, G. (2020). Poor survival with extracorporeal membrane oxygenation in acute respiratory distress syndrome (ARDS) due to coronavirus disease 2019 (COVID-19): Pooled analysis of early reports. Journal of critical care58, 27–28. Advance online publication. https://doi.org/10.1016/j.jcrc.2020.03.01

Papazian, L. et al. (2019).  Formal guidelines: Management of acute respiratory distress syndrome.  Ann. Intensive Care. 9:69, Retrieved from https://doi.org/10.1186/s13613-019-0540-9

Poston, J.T., Patel, B. K., & Davis, A.M. (2020). Management of critically ill adults with COVID-19. JAMA Clinical Guidelines Synopsis.  Retrieved from https://jamanetwork.com/journals/jama/fullarticle/2763879

Villar, Jesús MD, PhD1–3; Confalonieri, Marco MD4; Pastores, Stephen M. MD, MACP, FCCP, FCCM5; Meduri, G. Umberto MD6,,7 Rationale for Prolonged Corticosteroid Treatment in the Acute Respiratory Distress Syndrome Caused by Coronavirus Disease 2019, Critical Care Explorations: April 2020 – Volume 2 – Issue 4 – p e0111 doi: 10.1097/CCE.0000000000000111

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