An outbreak of highly contagious COVID-19 began at the end of 2019, and its incubation period was unclear. A small number of cases with an incubation period of up to 28 days have since been reported . The disease progresses rapidly, and significant worsening can be seen on chest CT within 2 days. The clinical manifestations of COVID-19 are not specific, and most patients are asymptomatic at the early stage of the disease. As the disease progresses, patients develop fever, cough, chest tightness and respiratory failure, and their conditions range from mild to severe. The prognosis of mild COVID-19 with common clinical treatment is generally good, and most patients are cured, with few sequelae. However, due to insufficient understanding of the disease and in patients with underlying disease, mild disease can develop into severe COVID-19, which is associated with poor prognosis.
This study presented the clinical characteristics of severe and critical cases of COVID-19. Based on the patients treated in our hospital, critical patients generally exhibit underlying diseases, mainly hypertension and diabetes, which is consistent with previous reports by other researchers . As with previous studies, the majority of COVID-19 cases were found to have clear epidemiological connections [24–26]. Of the 13 patients examined, 7 had been in contact with a COVID-19 patient in Wuhan. COVID-19 was first discovered in Wuhan, China, after which many articles began to refer to COVID-19 as Wuhan pneumonia [3, 27, 28].
This study also supports previous findings that severe COVID-19 cases are more common in males [3, 29]. A potential reason for this could be that COVID-19 was first found in a seafood market in Wuhan, and most of the workers there were men. The treatment courses for severe COVID-19 are varied, and the duration of treatment ranged from 7–39 days in our study. The shorter hospital stays could be explained by the rapid progression of the disease, and patients who died because of failure to receive timely treatment. Moreover, most patients presented with chest tightness, which could be explained by the rapid progression of the disease, and patients showed obvious short-term hypoxemia that developed into respiratory failure. Mechanical ventilation was often required because oxygen and antiviral treatments could not ease the symptoms.
The symptoms of severe COVID-19 were not restricted to viral infection, and bacterial or fungal infections were also observed. In our study, 10 patients presented with an increased neutrophil percentage and absolute neutrophil count, indicating a need for antimicrobial therapy. The two patients who died had fungal infections contributing to increased lesions in the lungs. Therefore, pulmonary fungal infection should be prevented in patients with COVID-19 to reduce the risk of mortality, and the risk factors for pulmonary aspergillosis should be monitored .
Most patients also presented with elevated cardiac and liver enzymes, which could be explained by destruction of cardiomyocytes and hepatocytes by the SARS-CoV-2 virus. These enzyme elevations were more evident in patients with severe COVID-19 than in those with milder disease. In addition, 4 patients in our study showed high D2 polymer levels and blood viscosity, which could be caused by damage to the coagulation system and trigger an emergency status in patients with COVID-19 .
Furthermore, lower immune status has been shown to be a risk factor for the onset of COVID-19 and the development of more severe disease [2, 10, 32–34]. Immune status may be the key to the relatively high incidence of hypertension, diabetes mellitus, and coronary heart disease found in patients with severe COVID-19 in this study. Studies have already found that patients with hypertension, diabetes mellitus, and coronary heart disease showed lower immunity status than healthy individuals [35–37].
The most common symptoms of severe COVID-19 patients were fever, cough, fatigue, chest tightness, and leukocytosis, and these signs should be carefully monitored to prevent the progression of COVID-19. The treatment regimens for severe COVID-19 patients in our hospital were based on the National Health and Construction Commission guidelines . In addition, traditional Chinese medicine and symptomatic support was combined with antiviral treatment. We noted that most patients presented with bacterial infection, and antibiotics were added into the conventional regimens. Glucocorticoids were administered to prevent infection for patients without bacterial infection . One study found that the use of glucocorticoids could inhibit an excessive inflammatory response in the body and reduce lung injury . Moreover, glucocorticoids may promote the absorption of pulmonary lesions in the acute stage and reduce the risk of pulmonary fibrosis in the later stage, leading to a shorter duration of mechanical ventilation [5, 41]. Therefore, glucocorticoids should be administered for severe COVID-19 patients presenting with progression of oxygenation indexes. However, glucocorticoids may inhibit lymphocytes and reduce immune function, which are significantly related to the disease course and prognosis of COVID-19. Therefore, glucocorticoids should be combined with immunoglobulin and albumin as an important supportive treatment for patients with COVID-19. Finally, mechanical ventilation should be considered, depending on the patient’s respiratory function, and the early use of a ventilation device could improve patients’ oxygenation, reduce pulmonary interstitial edema, and reduce the mortality risk for severe COVID-19.
Several limitations in this study should be acknowledged. The retrospective case series only included 13 patients, and there was no control group of patients with non-severe disease or comparison of characteristics and prognosis between those with mild and severe disease. The risk factors for the prognosis of severe COVID-19 were not identified, and the potential confounders were not adjusted.