Our research showed that among a moderately sized sample of patients who were hospitalized with Covid 19 requiring supplemental oxygen, patients exposed to intravenous furosemide was significantly associated with a lower use of mechanical ventilation compared to those that were not exposed to intravenous furosemide (adjusted Odds Ratio 0.37, 95% CI 0.21–0.66 p-value < 0.05). However, given the observational design of the study and the relatively wide confidence interval, the results of the study should not be taken to mean all Covid 19 patients should receive intravenous diuresis.
It appears the overall pathophysiology and clinical course of COVID-19-related lung injury suggests that it is broadly similar to other forms of virally-mediated acute respiratory distress syndrome. (59) The likely mechanism involved decreasing pulmonary edema with diuresis in Covid 19 patients who developed acute respiratory distress syndrome, resulting in improved gas exchange and oxygenation. This is similar to other strategies such as “keeping the lungs dry” and “maintaining a slightly negative fluid balance,” typically seen in the management of acute respiratory distress syndrome in non-Covid patients (13).
Our results support the use of intravenous diuresis as tolerated in hospitalized Covid 19 patients requiring supplemental oxygen to decrease the risk of mechanical ventilation. Noteworthy, one of the clinical practices during the Covid 19 pandemic was to intubate Covid 19 patients who showed acute respiratory failure or distress, early. Despite this, our study showed intravenous diuresis was still effective in reducing the use of mechanical ventilation in severe Covid 19 patients. More importantly, our results could have implications in the acute management of possible future viral outbreaks whose disease course is complicated by severe respiratory injury.
Reynolds, who was the first to report on anti-hypertensive agents such as hydrochlorothiazide in COVID-19 patients, found no statistically significant association between their use and adverse effects or the severity of Covid 19 disease (57). In our study, we specifically focused on only diuretics and mechanical ventilation. In another study, Tsolaki suggested cautious use of diuretics in mechanically ventilated COVID-19 patients and hypothesized detrimental effects by exacerbating heart-lung interactions, especially when a strategy of increased PEEP was applied (58). However, the paper focused on COIVD- 19 patients already on mechanical ventilation, while our study examined patients before the initiation of mechanical ventilation (58). Another study showed that among patients hospitalized with COVID-19, the baseline use of diuretics did not have a significant impact on the mortality or severity of the illness (56). The study only look at oral diuretics (56) while in our research chose to study intravenous diuretics because they were more likely to achieve effective volume removal when compared to oral diuretics.
The risk of unmeasured confounding cannot be fully dismissed in any observational study. One interpretation of our results is that selection bias likely existed in which patients the clinician(s) decided to give intravenous diuretics to. The patient population who received intravenous diuretics were likely to be different compared to the population of patients whose clinician(s) decided not to give intravenous diuretics. With that said, propensity score matching whose aim is to create an overall balance between comparison groups, was used to better account for this potential bias for the receipt of intravenous furosemide. In our propensity score matching analysis, an overall 76.6% of the patients (754 of the original 984) were paired. In particular, comorbidities, along with medications and laboratory values were all well matched between the comparison groups. Notably, the acute severity of the illness, characterized in one way by the use of low flow Nasal Cannula versus high flow Nasal Cannula, was not included in the propensity score analysis because it had already been accounted for in the study. All of the patients included in this study were either those on low flow Nasal Cannula, Venturi Mask, non-Rebreather Mask or high flow Nasal Cannula during the hospitalization. It should be noted, despite propensity score matching analysis, there may still be residual unmeasured confounder(s) affecting the results.
The study adjusted for likely confounders such as age, race, obesity, chronic kidney disease, diabetes, hypertension, chronic lung disease and congestive heart failure. In addition, medication administration, specifically Covid 19-specific therapies used during hospitalization were adjusted for because Remdesivir (an antiviral agent), Dexamethasone (a steroid) and Tocilizumab (an Interleukin-6 Receptor Antibody) have all been shown to decrease lung inflammation, and theoretically could effect the need for mechanical ventilation. The patient’s Covid Vaccination Status was also included in the analysis for similar reasons. Confidence in the results is supported by the multiple sensitivity analyses performed, all of which showed unchanged conclusions. The consistency of the results across the sensitivity analyses is reassuring.
One limitation in our study was it only examined intravenous furosemide and not other types of diuretics such as bumetanide or oral diuretics. The single center design may limit generalizability of these results. Most of the studied cohort was of a single race (Black 82.6%) which could limit generalizability. We did not use objective variables, such as PaO2:Fio2 ratio to define hypoxia. One possible limitation is the potential bias introduced by the study’s definition of intravenous diuretic exposure, which was defined as receiving intravenous furosemide at any point prior to mechanical ventilation initiation. If mechanical ventilation was initiated earlier in a patient's stay, they therefore, may have had less time to be exposed to intravenous diuretics, which could have resulted in biased results. With that said, at the hospital this study was carried out at, during most of the pandemic intravenous diuretics was recommended to be given as tolerated to Covid 19 patients who were hypoxic and thus likely would have helped mitigated this potential bias. Also, due to small sample sizes, some covariates in adjusted models do not have observations in all levels of the coviarate. In this case, the covariate is dropped from the model. Finally, due to the observational nature of this study, a randomized clinical trial is the best approach to determine whether any benefit from intravenous diuresis can be attributed to Covid 19 patients.
Further research should be aimed at examining the effects on mortality. One question that is raised by our study: if intravenous diuresis decreases mechanical ventilation, does it also decrease the severity of Covid 19 disease? Specifically, the progression to acute respiratory distress syndrome? Other research could focus on if acute dialysis shows similar results. Studying the effect of diuresis on the viral load of Covid 19 is interesting, as a case report from China showed the isolation of SARS-CoV-2 from the urine of a Covid 19 patient (29). Finally, investigating the effects of diuresis on the long-term complications of Covid 19 such as “long Covid” is another potential area of research.
In conclusion, we identified that intravenous diuresis decreases the use of mechanical ventilation in Covid 19 patients requiring supplemental oxygen.