The dynamics of clinical, radiological and virological parameters in patients with SARS
Severe acute respiratory syndrome (SARS) occurs in three stages and the development of adult respiratory distress syndrome with SARS is not a consequence of the uncontrolled replication of the virus, but has an immunological nature.
The May issue of Lancet magazine published the results of a prospective study of the dynamics of clinical, radiological and virological parameters in patients with severe acute respiratory syndromes (SARS). The 3-week study was followed by 75 patients who received treatment with the currently generally accepted standard regimen using ribavirin and glucocorticoids. At the same time, the dynamics of the clinical symptoms of the disease, the risk factors for adverse effects and the effectiveness of the diagnostic methods currently used were evaluated.
The results of the study showed that in most cases, SARS has a three-step course. The duration of each stage is approximately one week.
The first phase is characterized by fever, myalgia, chills, weakness, malaise, headache; after 2-7 days of illness, an unproductive dry cough appears. As a rule, at the end of the first week of the disease, the condition of the patients improves.
The progression of the cough characterizes the start of the second phase of SARS (end 1 - start 2 weeks of illness). Negative dynamics of the radiographic data are noted, shortness of breath, shortness of breath appears, some patients develop acute respiratory distress syndrome and the occurrence of watery diarrhea.
Fever, clinical and radiological signs of pneumonia were the main manifestations of the first days of the disease; a positive dynamic of these symptoms was noted towards the end of the first week, but after 8 to 9 days in 64 cases (85%), the fever reappeared. In 55 (73%) patients, symptoms of watery diarrhea occurred on days 5 to 7. In 60 (80%) patients, the radiological picture deteriorated on day 4-7. On the 6-8 day of the disease, respiratory symptoms progressed in 34 cases (45%). In 34 patients (45%), the positive dynamics of the initial lesions of the pulmonary tissue were accompanied by the appearance of new lesions on the radiography. During the third week of observation, nine patients (12%) developed pneumomediastinum and fifteen (20%) had acute respiratory distress syndrome requiring mechanical ventilation.
Quantitative analysis of the virus content in nasopharyngeal secretion, performed by reverse transcriptase PCR in 14 patients, showed that the peak of viral load occurs on the 10th day of the disease, whereas after 15 days this indicator was lower than at the time of hospitalization.
Summarizing these data, it can be assumed that the presence of fever, myalgia and other symptoms of general intoxication during the first week of the disease is associated with virus replication and cytolysis, while lesions lungs during the second week are largely caused by a pronounced immune response, rather than by a progressive replication of the virus.
The study revealed that the age of over 60 and chronic hepatitis B, specially treated with lamivudine, are independent risk factors for the development of acute respiratory distress syndrome (p = 0.001). The latter fact partly explains the high death rate from SARS in southern China, where chronic hepatitis B is widespread.
Antiviral drugs can play an important role in preventing the development of acute respiratory distress syndrome, which help reduce cytolysis and viral load in the early stages of the disease and reduce the severity of immune mediated damage in later stages. In terms of immunocorrection, the efficacy of the use of glucocorticoids, iv immunoglobulins, immunoglobulins enriched in IgM, plasma convalescents, thymosin TNF requires further study in other studies.
Thus, it can be assumed that the development of acute respiratory distress syndrome with SARS is not due to uncontrolled replication of the virus, but is an immune mediated pathological process.