Refractory ARDS

Editor's Notes

• #5: Mecahnical cardiopulm support used for prolonged time periods ~3-10 days The goal of therapy is to minimize ventilator-induced lung injury while allowing additional time to treat the underlying disease process and to permit recovery from acute injury. During ECMO, blood is drained from the native vascular system, circulated outside the body by a mechanical pump, and reinfused into the circulation. While outside the body, the blood passes through an oxygenator and heat exchanger. In the oxygenator, hemoglobin becomes fully saturated with oxygen, while carbon dioxide (CO2) is removed. Oxygenation is determined by flow rate, where elimination of CO2 can be controlled by adjusting the rate of countercurrent gas flow through the oxygenator VA: Blood is extracted from the RA and returned to the arterial system: Provides both cardiac and pulmonary support . Veno venous : Blood is extracted from the vena cava or RA and returned to the RA, THUS THE PATIENT MUST PROVIDE THE HD. CANNULAS ARE USALLY PLACED IN THE RIGHT COMMON FEMORAL FOR EXTRAXTION AND THE RIGHT IJ FOR INFUSION Although this porcedure sounds simple. The act of placing very large bore cannulas in these locations comes with considerable risk and must be performed under the guidence of a CT surgeon.  
• #6: The guidelines for indications foe use of ECMO are publised by the Extracorporeal life support organization. Generally ECMO could be considered in patients who are sufferinf from at least one of the following.
• #7: The use of this technique in adults comes from well described data on infants/neonates which has shown a mortaliy benefit when used in the setting of resp failure and lung transplant. Unfortunately this mortality benefit has yet to be convincingly confirmed in adult. Ealry Publications of Clinical research trial using ECMO in adults with ARDS yilded poor results. As an axample Given the negative results from these trials, enthusiasm for the use of ECMO in adult respiratory failure waned in the 1980s,   Advances in overall ICU care, ventilator management and ECMO technology render these early trial results not applicable to current practice.
• #8: After doing a Pubmed search using the words ECMo and ARDS then limited the search to clinical trials in adults. 18 papers are found. After briefly reviewing them in addition to reviweing the uptodate article written by Dr, Jonathan Haft a profsssoer of caridac surgery at the university of michigan, and Dr. Robert Bartlett who is a professor emeritus at the same. 11 of these show promising results 8 of these studies were observtional, but consistantly found a slighlty beter survival rate than those published in the past. The last two I believe has spurred a debate about where the survival benefit comes from. Interestingly, when reading the uptodate article on this topic the recommendation for ECMO in ARDS states of note the seciton editor for this article was our own Dr. Parsons. Lets look at why.
• #9: To date this is thonly randomized clincal control trial to date which has compared our current conventional ventilation to ECMO.
• #10: high pressure (>30 cm H2O of peak inspiratory pressure) or high FiO2 (>0·8) ventilation for more than 7 days; intracranial bleeding; any other contraindication to limited heparinisation; or any contraindication to continuation of active treatment
• #11: The group referred to the ECMO center had significantly increased survival without disability at six months compared to conventional management (63 versus 47 percent
• #12: Twenty five percent of the patients referred for ECMO were not managed with ECMO because 6 died before transfer to the ECMO center and 24% reovered with the conventional ventilation protocol used by the ECMO center.
• #13: Additionally another potential limitation of this study was in the use of the murray lung injury score. The main disadvantage to the Murray score, especially in the conduct of large clinical studies, is that pulmonary compliance is not routinely measured. A significant deficiency of the Murrary score is that cardiogenic pulmonary edema is not excluded
• #14: The other artice published 2011 pertained to ARDS 2/2 H1N1.
• #15: AcohortstudyinwhichECMO-referredpatientswere defined as all patients with H1N1-related ARDS who were referred, accepted, and trans- ferred to 1 of the 4 adult ECMO centers in the United Kingdom during the H1N1 pan- demic in winter 2009-2010. The ECMO-referred patients and the non–ECMO-referred patients were matched using data from a concurrent, longitudinal cohort study (Swine Flu Triage study) of critically ill patients with suspected or confirmed H1N1. Detailed demo- graphic, physiological, and comorbidity data were used in 3 different matching tech- niques (individual matching, propensity score matching, and GenMatch matching).
• #16: Evern after adjusting the data through three different level of matching there was a survival benefit 23.7 versus 52.5 percent But again in this study ~15% of patients referrred to an ecmo center were managed with conventiaonal ventilation Eighty five percent of the patients referred to an ECMO center were managed with ECMO, while the others improved with conventional ventilation Of note since the 2009 epidemic referal for ECMO in the setting of H1N1 has increased from 100 cases per year to 400, not because there is more data but because like our patient those referred are very young w/out significanct co morbidity who develop progound hypoxemia in the setting of a very stiff lung. Refractory to conventionalt therapy,
• #17: Or is it that I we standardize conventiional therapy patients do better?
• #18: Ecmo vs convtional ventilation protocolized.