3.1. Epidemiological data
Between 8th February and 16th March, 107 patients were admitted to the ICU of Wuhan Huoshenshan Hospital, and 13 patients who did not reach the endpoint were ineligible. The patient flow chart is shown in Figure 1. Ultimately, 94 critical patients met our inclusion criteria and were included in this study. Overall, 42 (45%) of them eventually died, another 14 (15%) patients were discharged from our hospital, 30 (32%) patients were transferred out of the ICU, and 8 (8%) were in stable condition.
An overview of the baseline characteristics of nonsurvivors (n=42) and survivors (n=52) in terms of demographic and underlying health problems is provided in Table 1. There were 54 (58%) males and 40 (43%) females, and the average age was 69.17±9.55 years. We found that most critical patients were over 60 years old, and the average age was significantly higher in nonsurvivors than in survivors (70.93±8.48 vs. 67.75±10.20), which can also be observed visually in Figure 2. Among these patients, only 11 patients (12%) had been in close contact with confirmed patients, and no one was ever exposed to the Huanan seafood market. Closer inspection of this table showed that more than half of the patients had underlying health problems, of which the first few were hypertension (60%), diabetes mellitus (19%), cardiovascular diseases and chronic pulmonary diseases.
3.2 Clinical features on admission
The clinical features on admission are summarized in Table 2. Interestingly, many laboratory test results were significantly different between the two groups, including WBC, TLC, PLT, CRP, cardiac function indicators, D-dimer, PCT, etc. Low TLC was present in both groups, but it was much lower in nonsurvivors than in survivors (0.63*109/L±0.41 vs. 0.89±0.45). Although the PLT in each group were in the normal range, a lower PLT was observed in nonsurvivors (162.73±110.55 vs. 203.69±87.85). The inflammatory indicators, cardiac function, PCT level and D-dimer level in nonsurvivors were more severely impaired than those in survivors as well, while most liver function and kidney function remained normal or mildly abnormal (the influence of underlying health problems cannot be ruled out).
3.3 Findings during clinical course
As a whole, the median duration from admission to transfer to the ICU was 2 days (IQR 0, 7), whereas the median length of ICU stay was 8 days (IQR 4, 13) (Table 3). The most frequently observed symptom was fever (77%), followed by dry cough (59%) and fatigue (54%). Moreover, few patients developed infrequent conditions, such as headache (3[3%]), vomiting (2[%]) and diarrhea (2[2%]). Most patients required supplemental oxygen with nasal high-flow oxygen therapy (71%); noninvasive mechanical ventilation (54%) and invasive mechanical ventilation (37%) were also used in patients, among whom nonsurvivors accounted for a higher proportion and had worse illness. Extracorporeal membrane oxygenation was used in 2 patients; unfortunately, none of them survived. Regarding medications, glucocorticoids (80%), antiviral drugs (79%) and antibiotics (82%) were widely used; interestingly, the use of Chinese medicine was statistically significant between the two groups (P=0.0005). Not surprisingly, sepsis (100%) and acute respiratory distress syndrome (ARDS) (95%) were the two most common complications in nonsurvivors. Compared to survivors, nonsurvivors also showed a significantly higher proportion of secondary bacterial infection (69% vs. 21%), myocardial injury (64% vs. 15%), acute kidney injury (60% vs. 13%), coagulopathy (55% vs. 12%) and acute liver injury (48% vs. 12%).
As shown in Figure 3, the dynamic changes in several key laboratory indexes were compared. It was apparent that TLC and PLT were generally lower in nonsurvivors than in survivors, whereas WBC and CRP levels were higher. We supposed that an elevated WBC was affected by a second bacterial infection and that the usage of glucocorticoids and presence of reduced TLC was expected based on the biological characteristics of this virus. Hepatic enzymes and TBIL were elevated and peaked on approximately the tenth day after admission among nonsurvivors, but the variations were small as a whole. To assess cardiac function, hsTNI was recorded and found to be remarkably increased. CRE and PCT were also recorded (see Figure E1 in the online data supplement).
The distinct trajectories of temperature during the follow-up, which could provide valuable insight to monitoring the recovery of patients, are demonstrated in Figure 4. The patients were classified into 3 groups based on the temperature trajectory after admission as follows: group 1 (stabilized group; n=55, 59.7%), maintained a stable temperature below 37℃; group 2 (down-and-up group; n=22, 24.4%), had a mean temperature that decreased at the beginning and finally climbed up; and group 3 (steady-declining group; n=15, 16.0%), the temperature of these patients was initially higher than normal and dropped gradually to approximately 36.4℃ from the above normal body temperature. Patients with these 3 temperature trajectories had distinct fatalities. Group 1 had the lowest fatality rate at 25.45%, with a mean temperature of 36.46°C. Patients in group 2 had a mean temperature of 36.71°C and a fatality rate of 54.55%. In particular, the steady-declining group was characterized by the highest fatality rate of 93.33% (mean temperature, 36.98°C). The characteristics at baseline and laboratory tests on admission stratified by temperature trajectory groups were presented in Table E1 (see Table E1 in the online data supplement).