Early outcomes with utilization of tissue plasminogen activator in COVID-19-associated respiratory distress: A series of five cases.

BACKGROUND: Coronavirus patients demonstrate varying degrees of respiratory insufficiency; many will progress to respiratory failure with a severe version of acute respiratory distress syndrome refractory to traditional supportive strategies. Providers must consider alternative therapies to deter or prevent the cascade of decompensation to fulminant respiratory failure. METHODS: This is a case-series of five COVID-19 positive patients who demonstrated severe hypoxemia, declining respiratory performance, and escalating oxygen requirements. Patients met the following criteria: COVID-19 positivity, worsening respiratory performance, severe hypoxemia (PaO2 ≤ 80) despite traditional supportive measures, escalating supplemental oxygen requirements, and D-dimer greater than 1.5 µg/mL. All patients received protocol directed thrombolytic therapy with tissue plasminogen activator (tPA). RESULTS: All five patients improved without deleterious effects of thrombolytic therapy. Patient one was on maximum ventilator support, paralytics, and prone positioning without improvement. During tPA administration his PaO2/FIO2 ratio improved from 69 to 127. Ventilator support was weaned immediately on posttreatment day 1, and he was extubated on posttreatment day 12. Our second through fifth patients were not intubated at time of initiation of tPA therapy. These patients each required significant oxygen supplementation trending toward intubation. After tPA therapy, all patients demonstrated a noticeable increase in PaO2 values overtime. Three of these patients avoided intubation due to COVID-19-associated respiratory failure. CONCLUSION: Administration of thrombolytics was followed by overall improvement in patients' oxygen requirements, and in three cases, prevented progression to mechanical ventilation, without deleterious effects. Clinical trials of thrombolytic therapy would further serve to underscore the efficacy and utility of this therapy. LEVEL OF EVIDENCE: Case series of therapeutic effect, Level V.

l-Galactose replaces l-fucose in the pectic polysaccharide rhamnogalacturonan II synthesized by the l-fucose-deficient mur1 Arabidopsis mutant.

Arabidopsis thaliana mur1 is a dwarf mutant with altered cell-wall properties, in which l-fucose is partially replaced by l-galactose in the xyloglucan and glycoproteins. We found that the mur1 mutation also affects the primary structure of the pectic polysaccharide rhamnogalacturonan II (RG-II). In mur1 RG-II a non-reducing terminal 2- O-methyl l-galactosyl residue and a 3,4-linked l-galactosyl residue replace the non-reducing terminal 2- O-methyl l-fucosyl residue and the 3,4-linked l-fucosyl residue, respectively, that are present in wild-type RG-II. Furthermore, we found that a terminal non-reducing l-galactosyl residue, rather than the previously reported d-galactosyl residue, is present on the 2- O-methyl xylose-containing side chain of RG-II in both wild type and mur1 plants. Approximately 95% of the RG-II from wild type and mur1 plants is solubilized as a high-molecular-weight (>100 kDa) complex, by treating walls with aqueous potassium phosphate. The molecular mass of RG-II in this complex was reduced to 5-10 kDa by treatment with endopolygalacturonase, providing additional evidence that RG-II is covalently linked to homogalacturonan. The results of this study provide additional information on the structure of RG-II and the role of this pectic polysaccharide in the plant cell wall.