Results
Our patient is a 49 year-old woman with obesity (BMI 39) and hypertension who developed cough, sore throat, and fever progressing to severe dyspnea. She presented to the emergency room with a resting oxygen saturation of 75% (room air) improving to 88% via non-rebreather. Chest radiograph revealed bilateral infiltrates, attempts to obtain an arterial blood gas (ABG) were unsuccessful due to clotted samples.
Her dyspnea worsened prompting intubation and mechanical ventilation support, with a tidal volume of 6 ml/kg (ideal body weight), PEEP 18cmH2O, and FiO2 100% yielding an arterial partial pressure of oxygen (PAO2) 134mmHg with plateau pressure 30cmH2O. Echocardiogram revealed normal cardiac function, renal and liver function were without abnormality, and intravenous heparin was started (PTT 60-80) for a D-dimer greater than 4000ng/ml and fibrinogen above assay. She was paralyzed, treated with inhaled nitric oxide, and underwent prone positioning.
Due to persistent hypoxia she was ultimately initiated on VV ECMO. Ultrasound was used to access the right femoral vein (RFV) and right internal jugular vein (RIJ). A 10,000 unit bolus of intravenous heparin was administered followed by insertion of a 25Fr multistage cannula in the RFV and a 17Fr return cannula in the RIJ. Flows ranging from 4.5-5.0 liters/minute were achieved at pump RPMs of 3700. Despite excellent circuit oxygenation (confirmed with post-membrane oxygenator ABG) and ECMO optimization, the patient required an FiO2 of 70% to maintain a PAO2 > 60mmHg.
She remained febrile and tachycardic with an estimated cardiac output(CO) of 9.8L/min (via Fick equation). We hypothesized that her elevated CO was not required to maintain adequate oxygen delivery (DO2), as her estimated basal output was 5.5-6L, but instead provoked by the infection. In an effort to increase the fraction of her CO entrained into the circuit we initiated an esmolol infusion (50mcg/kg/min) titrated to a pulse of 60-70 bpm. Phenylephrine (50 mcg/min) and vasopressin (0.04 units/min) infusions were started to maintain a mean arterial pressure >65mmHg. These interventions enabled decreasing the FiO2 on the ventilator to 50%, PEEP 16cmH2O (per lung protective ventilation protocol) and achieved a PAO2>80mmHg with low tidal volumes.
After nine days on ECMO, compliance measured on the ventilator showed mild improvement (12-20ml/cmH20) and a trial off ECMO maintained PAO2>100 on 60%FIO2 and PEEP 16cmH2O. In the setting of persistent bleeding at her cannulation sites and ability to be maintained on non-injurious ventilator support we decannulated. The patient improved on supine ventilation and was ultimately extubated and discharged from the hospital.