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.