Presence of procoagulant peripheral blood mononuclear cells in severe COVID-19 patients relate to ventilation perfusion mismatch and precede pulmonary embolism

PURPOSE

Pulmonary emboli (PE) contribute substantially to coronavirus disease 2019 (COVID-19) related mortality and morbidity. Immune cell-mediated hyperinflammation drives the procoagulant state in COVID-19 patients, resulting in immunothrombosis. To study the role of peripheral blood mononuclear cells (PBMC) in the procoagulant state of COVID-19 patients, we performed a functional bioassay and related outcomes to the occurrence of PE. Secondary aims were to relate this functional assay to plasma D-dimer levels, ventilation perfusion mismatch and TF expression on monocyte subsets.

METHODS

PBMC from an ICU biobank were obtained from 20 patients with a computed tomography angiograph (CTA) proven PE and compared to 15 COVID-19 controls without a proven PE. Functional procoagulant properties of PBMC were measured using a modified fibrin generation time (MC-FGT) assay. Tissue factor (TF) expression on monocyte subsets were measured by flow cytometry. Additional clinical data were obtained from patient records including end-tidal to arterial carbon dioxide gradient.

RESULTS

MC-FGT levels were highest in the samples taken closest to the PE detection, similar to the end-tidal to arterial carbon dioxide gradient (ETCO2 - PaCO2), a measurement to quantify ventilation-perfusion mismatch. In patients without proven PE, peak MC-FGT relates to an increase in end-tidal to arterial carbon dioxide gradient. We identified non-classical, CD16 positive monocytes as the subset with increased TF expression.

CONCLUSION

We show that the procoagulant state of PBMC could aid in early detection of PE in COVID-19 ICU patients. Combined with end-tidal to ETCO2 - PaCO2 gradient, these tests could improve early detection of PE on the ICU.

Fat embolism syndrome in a patient that sustained a femoral neck fracture: A case report

Background

We present a case of a patient with a femoral neck fracture that shows neurological impairment and respiratory distress 1 day after trauma, caused by the Fat Embolism Syndrome with the presence of Cerebral Fat Embolisms.

Case summary

A 75 year old female remained unresponsive after a hemi arthroplasty was performed because of a 1 day old femoral neck fracture. She rapidly developed respiratory insufficiency and an obstructive shock with right ventricle dilatation on transthoracic echocardiography. The diffusion-weighted MRI brain images showed the "Starfield" pattern, a radiologic phenomenon typical for FES. During 3 weeks of ICU admission the neurologic state slowly ameliorated.

Conclusion

The rare FES is a clinical diagnosis with mainly respiratory, neurologic and dermatologic symptoms in the setting of a trauma patient. Fat embolisms are able to reach the brain without the presence of a patent foramen ovale to cause neurological symptoms. Diagnosing FES remains challenging but the distinctive "Starfield" pattern on MRI scans is promising.