Cannulation and ECMO initiation-
Femoral-femoral veno-venous ECMO cannulation was performed by the cardiac surgeon in the ICU under trans-esophageal (TEE) guidance by cardiac anesthesia. Full personal protective equipment was worn by all members of the health care team within the room. Additional precautionary measures included limiting the number of health care workers within the patients’ room during cannulation. The institutional cannulation heparin bolus dose for VV ECMO was increased from 50u/kg to 100u/kg or more after the initial patients formed significant thromboses despite heparin anticoagulation. Cannula included a Edwards ThruPort™ Quick Draw™ (Irvine, CA) 25Fr multi-stage femoral venous drain with the distal tip positioned at approximately the hepatic vein - inferior vena cava junction, and a Medtronic Bio-Medicus™ NextGen (Minneapolis, MN) 19-21Fr return cannula with the tip placed within the right atrium. ECMO equipment consisted of either a Rotaflow centrifugal pump (Getinge AB, Getinge, Sweden) with a Quadrox iD Adult oxygenator or a CARDIOHELPi system (Getinge AB) with HLS Set Advanced 7.0. ECMO blood flow was maintained > 3 L/min to help minimize the identified risk of thrombosis.
Following cannulation, patients were placed on an ultra-protective ventilator strategy that included a graded reduction in plateau pressure to < 20 cmH2O over the next 12 hours. Tidal volumes were reduced to < 4ml/kg IBW and the FiO2 was reduced to 60% if the patient was able to maintain an acceptable oxygenation status. Positive end expiratory pressure (PEEP) was slowly reduced to a level of 10 - 14cmH2O. Higher levels of PEEP were required in patients with high BMI’s. Respiratory rate was maintained at 8 - 10 breaths/minute for the initial 24 hours. In Covid-19 patients with the lung phenotype characterized with increased compliance, higher tidal volumes, and respiratory rates were tolerated as the patients started to improve (10). In addition, patients with bilateral infiltrative disease that did not improve after fluid removal and lung rest underwent a 16-hour prone positioning plan (Figure 2). Seven of the fifteen patients managed on ECMO were placed into a prone position at least once, with the majority in prone position multiple times. Mobility was gradually enhanced from a bed tilt of 30-45 degrees to as high as standing (vertical) positioning via a specialty bed (Kreg Medical, Inc. Chicago, IL) (Figure 3).