Table 1 Baseline characteristics, stratified by wave

Age (years)

54.6 (14.0)

57.3 (13.2)***

Male sex

222 (70%)

297 (65%)

Ethnicity

 White

120 (38%)

179 (39%)***

 Black

90 (29%)

72 (16%)

 Other

106 (34%)

205 (45%)

Source of admission

 ED

94 (30%)

148 (32%)

 Ward

105 (33%)

116 (25%)

 Transfer from another hospital

114 (36%)

188 (41%)

 Other

3 (1%)

4 (1%)

Infection setting

 Community

278 (88%)

425 (93%)**

 Hospital

8 (2%)

18 (4%)

 Occupational

24 (8%)

10 (2%)

 Other

6 (2%)

3 (1%)

 BMI

28.4 (24.8–33.6)

29.4 (26.0–36.2)**

 Current smoker

13 (4%)

17 (4%)

 Days of symptoms pre-admission

9 (7–13)

9 (5–13)

 Admission SOFA score

5 (3–7)

4 (3–6)***

 APACHE II score

14.1 (4.8)

13.2 (5.1)

 Clinical frailty score

2 (2–3)

3 (2–3)*

Pre-existing comorbidities

 Diabetes

96 (30%)

137 (30%)

 Asthma

48 (15%)

69 (15%)

 Hypertension

127 (40%)

205 (45%)

 CAD

16 (5%)

41 (9%)*

 CHF

14 (4%)

17 (4%)

 Atrial fibrillation/atrial flutter

11 (3%)

12 (3%)

 COPD

12 (4%)

35 (8%)

 Chronic kidney disease

22 (7%)

33 (7%)

 Chronic liver disease

12 (4%)

17 (4%)

 HIV infection

7 (2%)

9 (2%)

 Malignancy

14 (4%)

23 (5%)

Baseline laboratory parameters and organ support on admission to ICU

 Type of ventilation on admission

  Invasive ventilation

254 (80%)

278 (61%)***

  Non-invasive ventilation

4 (1%)

16 (4%)

  High-flow nasal cannula

24 (8%)

151 (33%)

  None

34 (11%)

11(2%)

  Extracorporeal membrane oxygenation

58 (18%)

64 (14%)

 Number of vasopressors

  0

183 (58%)

320 (70%)**

  1

131 (38%)

130 (29%)

  2

11 (3%)

6 (1%)

  3

1 (1%)

–

 Baseline creatinine (µmol/L)

81.5 (68.0–96.1)

78.0 (65.5–91.5)*

 pH

7.4 (7.3–7.4)

7.4 (7.4–7.5)***

 PaO₂ (kPa)

10.1 (8.8–12.8)

8.3 (7.2–9.6)***

 Ionised calcium (mmol/L)

1.1 (1.1–1.2)

1.1 (1.1–1.2)

 Lactate (mmol/L)

1.7 (1.3–2.3)

1.8 (1.4–2.4)

 Chloride (mEg/L)

99.7 (5.5)

102.2 (5.3)***

 White blood cells (10⁹/L)

8.7 (6.4 -12.4)

9.7 (6.5–13.8)

 Neutrophils (10⁹/L)

7.5 (4.8–10.4)

8.4 (5.4–12.1)*

 Lymphocytes (10⁹/L)

0.8 (0.5–1.1)

0.7 (0.4–1.0)**

 Haemoglobin (g/L)

117 (21.3)

118 (23.9)

 Ferritin (µg/L)

1121 (676–2182)

1039 (527–1859)*

 d-dimer (mg/L)

1.7 (0.80–6.84)

2.1 (0.92–7.31)

 CRP (mg/L)

170 (92–292)

91 (42–174)***

 PaO₂/FiO₂ ratio

17.8 (13.1–25.1)

13 (10.0–17.7)***

On admission to ICU

 AKI diagnosis

121 (38%)

110 (24%)

 Kidney replacement therapy

31 (13%)

20 (9%)**

During ICU admission

 Max PEEP in first 24 h (cmH₂O)

7.5 (4.9)

5.5 (5.1)***

 Max PEEP in first 48 h (cmH₂O)

8.42 (4.84)

6.45 (5.26)***

 AKI diagnosis

241 (76%)

232 (51%)***

 Kidney replacement therapy

100 (32%)

60 (13%)***

 Delta fluid balance between day 1 and 2 (mL/kg)^a

3.64 (16.4)

4.01 (16.1)

 Diuretic use in first 48 h (%)

111 (35%)

96 (21%)***