Introduction:

Among the patients infected with SARS-CoV-2, 14.6% were admitted to intensive care unit. this 29 to 75% required invasive mechanical ventilation with an associated mortality of 12 to 81%. Acute respiratory distress syndrome (ARDS) is the most serious form of presentation. The pathophysiology of ARDS secondary to SARS-CoV-2 differs from conventional causes. It presents dysregulation in hypoxic pulmonary vasoconstriction, secondary acute pulmonary hypertension and microthrombotic phenomena. The development of refractory severe hypoxemia (PaO2 < 60 mmHg or PaO2/FiO2 < 100 mmHg, with FiO2 80 to 100%, with PEEP > 10 to 20 cmH2O for at least 10 to 12 hours) constitutes the scenario of maximum severity with an associated mortality of 71 to 94%. The use of rescue strategies that impact on the specific pathophysiology of this entity such as the use of inhaled nitric oxide, neuromuscular blockade and prone ventilation have emerged as therapeutic targets of interest. Protective mechanical ventilation (plateau pressure [Pplat] < 27 cmH2O and driving pressure [DP] < 15 cmH2O) continues to be the cornerstone of the management.

Objectives:

To determine whether there is an association between the use of inhaled nitric oxide and prone ventilation with ventilatory mechanics in patients with severe refractory hypoxemia secondary to SARS-CoV-2 infection.

Material and methods:

A historical, retrospective, descriptive, comparative and retrolective cohort study was carried out. Data from the records of patients admitted to the Respiratory ICU of the ABC Medical Center with a diagnosis of ARDS secondary to SARS-CoV-2 infection who required iNO and mechanical ventilation in prone from April 1 to December 31, 2020 were analyzed. A univariate analysis was performed, the statistical analysis was performed in SPSS v 21, measures of trend, dispersion were analyzed as well as the analysis of risk factors with Student’s t test and χ2.

Results:

A total of 108 patients were analyzed, of which 54 received iNO, neuromuscular blockade and prone and 54 only neuromuscular blockade and prone ventilation. 81.5% (n = 88) were men. The most common comorbidity was diabetes mellitus in 51.9% (n = 56). The increase in oxygenation (delta PaO2/FiO2) was with a median of 31.9 ± 15.2 mmHg in the iNO group and 52.9 ± 16.74 mmHg in the control group (p = 0.001). The postintervention Pplat in the iNO group was 26.3 ± 3 and 34.5 ± 1.9 cmH2O in the control group (p = 0.792). The preintervention DP in the iNO group was 17.2 ± 3.9 and 13.4 ± 2.8 cmH2O in control group vs 13.1 ± 1.29 and 12 ± 1.92 cmH2O after the intervention (p = 0.001).

Conclusions:

The use of iNO in patients with severe hypoxemia refractory to prone ventilation and neuromuscular blockade did not produce a statistically significant improvement in oxygenation, however it allowed to reprogram the ventilatory support to keep the patient in goals of alveolar protection.

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