Clinical characteristics and outcomes of patients with COVID-19 admitted to the intensive care unit during the first and second waves of the pandemic in Brazil: a single-center retrospective cohort study

Corrêa, Thiago Domingos; Midega, Thais Dias; Cordioli, Ricardo Luiz; Barbas, Carmen Silvia Valente; Rabello Filho, Roberto; Silva, Bruno Caldin da; Silva Júnior, Moacyr; Nawa, Ricardo Kenji; Carvalho, Fabrício Rodrigues Torres de; Matos, Gustavo Faissol Janot de; Lucinio, Neide Marcela; Rodrigues, Rodrigo Dias; Eid, Raquel Afonso Caserta; Bravim, Bruno de Arruda; Pereira, Adriano José; Santos, Bento Fortunato Cardoso dos; Pinho, João Renato Rebello; Pardini, Andreia; Teich, Vanessa Damazio; Laselva, Claudia Regina; Cendoroglo Neto, Miguel; Klajner, Sidney; Ferraz, Leonardo José Rolim

doi:10.31744/einstein_journal/2023AO0233

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ORIGINAL ARTICLE • einstein (São Paulo) 21 • 2023 • https://doi.org/10.31744/einstein_journal/2023AO0233 linkcopy

Clinical characteristics and outcomes of patients with COVID-19 admitted to the intensive care unit during the first and second waves of the pandemic in Brazil: a single-center retrospective cohort study

Authorship SCIMAGO INSTITUTIONS RANKINGS

Objective To describe and compare the clinical characteristics and outcomes of patients admitted to intensive care units during the first and second waves of the COVID-19 pandemic.

Methods In this retrospective single-center cohort study, data were retrieved from the Epimed Monitor System; all adult patients admitted to the intensive care unit between March 4, 2020, and October 1, 2021, were included in the study. We compared the clinical characteristics and outcomes of patients admitted to the intensive care unit of a quaternary private hospital in São Paulo, Brazil, during the first (May 1, 2020, to August 31, 2020) and second (March 1, 2021, to June 30, 2021) waves of the COVID-19 pandemic.

Results In total, 1,427 patients with COVID-19 were admitted to the intensive care unit during the first (421 patients) and second (1,006 patients) waves. Compared with the first wave group [median (IQR)], the second wave group was younger [57 (46-70) versus 67 (52-80) years; p<0.001], had a lower SAPS 3 Score [45 (42-52) versus 49 (43-57); p<0.001], lower SOFA Score on intensive care unit admission [3 (1-6) versus 4 (2-6); p=0.018], lower Charlson Comorbidity Index [0 (0-1) versus 1 (0-2); p<0.001], and were less frequently frail (10.4% versus 18.1%; p<0.001). The second wave group used more noninvasive ventilation (81.3% versus 53.4%; p<0.001) and high-flow nasal cannula (63.2% versus 23.0%; p<0.001) during their intensive care unit stay. The intensive care unit (11.3% versus 10.5%; p=0.696) and in-hospital mortality (12.3% versus 12.1%; p=0.998) rates did not differ between both waves.

Conclusion In the first and second waves, patients with severe COVID-19 exhibited similar mortality rates and need for invasive organ support, despite the second wave group being younger and less severely ill at the time of intensive care unit admission.

Coronavirus infections; COVID-19; SARS-CoV-2; Respiration, artificial; Noninvasive ventilation; Extracorporeal membrane oxygenation; Critical care outcomes; Mortality; Intensive care units

Characteristics	All n=1,427	First wave n=421	Second wave n=1,006	p value*
Age, years (median, IQR)	59 (47-73)	67 (52-80)	57 (46-70)	<0.001^#
Men, n/total n (%)	972/1,427 (68.1)	269/421 (63.9)	703/1,006 (69.9)	0.032^&
SAPS 3 Score (median, IQR)	46 (42-54)	49 (43-57)	45 (42-52)	<0.001^#
SOFA Score (median, IQR)^$	3 (1-6)	4 (2-6)	3 (1-6)	0.018^#
CCI (median, IQR)	0 (0-1)	1 (0-2)	0 (0-1)	<0.001^#
MFI, points (median, IQR)^‡	1 (0-2)	1 (0-2)	1 (0-2)	<0.001^#
Non-frail	612/1,416 (43.2)	153/421 (36.3)	459/995 (46.1)	<0.001^&
Pre-frail	625/1,416 (44.1)	192/421 (45.6)	433/995 (43.5)
Frail	179/1,416 (12.6)	76/421 (18.1)	103/995 (10.4)
Underlying disease, n/total n (%)
Systemic hypertension	623/1,083 (57.5)	195/335 (58.2)	428/748 (57.2)	0.812^&
Diabetes mellitus	328/1,083 (30.3)	113/335 (33.7)	215/748 (28.7)	0.114^&
Asthma	68/1,083 (6.3)	23/335 (6.9)	45/748 (6.0)	0.691^&
Cancer	72/1,083 (6.6)	23/335 (6.9)	49/748 (6.6)	0.952^&
Congestive heart failure	50/1,083 (4.6)	24/335 (7.2)	26/748 (3.5)	0.012^&
COPD	66/1,083 (6.1)	17/335 (5.1)	49/748 (6.6)	0.423^&
Chronic kidney disease	45/1,083 (4.2)	20/335 (6.0)	25/748 (3.3)	0.066^&
Chronic kidney disease requiring RRT	18/1,083 (1.7)	6/335 (1.8)	12/748 (1.6)	1.000^&
Hematologic cancer	21/1,083 (1.9)	12/335 (3.6)	9/748 (1.2)	0.017^&
Metastatic cancer	9/1,083 (0.8)	4/335 (1.2)	5/748 (0.7)	0.604^&
Days from hospital to ICU admission	1 (0-2)	0 (0-2)	1 (0-3)	<0.001^#
Support at ICU admission, n/total n (%)
Non-invasive ventilation	581/1,425 (40.8)	69/421 (16.4)	512/1,004 (51.0)	<0.001^&
Mechanical ventilation	122/1,425 (8.6)	49/421 (11.6)	73/1,004 (7.3)	0.010^&
Vasopressors	100/1,425 (7.0)	35/421 (8.3)	65/1,004 (6.5)	0.260^&
Renal replacement therapy	4/1,425 (0.3)	2/421 (0.5)	2/1,004 (0.2)	0.727^&

Resource	All n=1,427	First wave n=421	Second wave n=1,006	p value*
Support during ICU stay, n/total n (%)
Non-invasive ventilation	1,043/1,427 (73.1)	225/421 (53.4)	818/1,006 (81.3)	<0.001^&
Mechanical ventilation	494/1,427 (34.6)	137/421 (32.5)	357/1,006 (35.5)	0.315^&
Vasopressors	434/1,427 (30.4)	143/421 (34.0)	291/1,006 (28.9)	0.068^&
High flow nasal cannula	733/1,427 (51.4)	97/421 (23.0)	636/1,006 (63.2)	<0.001^&
Renal replacement therapy	149/1,427 (10.4)	35/421 (8.3)	114/1,006 (11.3)	0.108^&
ECMO	20/1,427 (1.4)	6/421 (1.4)	14/1,006 (1.4)	1.000^&
Tracheostomy, n/total n (%)	92/1,427 (6.4)	26/421 (6.2)	66/1,006 (6.6)	0.879^&
MV duration (days), median (IQR)	9 (6-23)	9 (5-15)	10 (6-24)	0.170^#

Outcomes	All n=1,427	First wave n=421	Second wave n=1,006	p value*
Destination at hospital discharge, n/total n (%)				0.452^&
Home	1,220/1,422 (85.8)	358/421 (85.0)	862/1,001 (86.1)
Home-care	15/1,422 (1.1)	7/421 (1.7)	8/1,001 (0.8)
Transfer to another hospital	13/1,422 (0.9)	5/421 (1.2)	8/1,001 (0.8)
Death	174/1,422 (12.2)	51/421 (12.1)	123/1,001 (12.3)
Palliative care	24/1,422 (1.7)	16/421 (3.8)	8/1,001 (0.8)	<0.001^&
ICU mortality	158/1,427 (11.1)	44/421 (10.5)	114/1,006 (11.3)	0.696^&
Hospital mortality	174/1,422 (12.2)	51/421 (12.1)	123/1,001 (12.3)	0.998^&
ICU LOS (days), median (IQR)	8 (5-16)	8 (4-15)	9 (5-16)	0.009^#
Hospital LOS (days), median (IQR)	13 (9-22)	12 (8-22)	13 (9-22)	0.031^#
According to the use of MV
Patients who received MV, n/total n (%)	494/1,427 (34.6)	137/421 (32.5)	357/1,006 (35.5)
ICU mortality	128/494 (25.9)	30/137 (21.9)	98/357 (27.5)	0.252^&
Hospital mortality	138/491 (28.1)	36/137 (26.3)	102/354 (28.8)	0.654^&
ICU LOS (days), median (IQR)	18 (13-29)^§	18 (12-30)^§	18 (13-29)^§	0.735^#
Hospital LOS (days), median (IQR)	24 (16-38)^§	24 (15-41)^§	24 (16-37)^§	0.836^#
Patients who did not receive MV, n/total n (%)	933/1,427 (65.4)	284/421 (67.5)	649/1,006 (64.5)
ICU mortality	30/933 (3.2)	14/284 (4.9)	16/649 (2.5)	0.078^&
Hospital mortality	36/931 (3.9)	15/284 (5.3)	21/647 (3.2)	0.194^&
ICU LOS (days), median (IQR)	6 (3-9)	5 (2-9)	6 (4-9)	0.001^#
Hospital LOS (days), median (IQR)	11 (8-14)	10 (7-14)	11 (8-14)	0.012^#
According to the use of RRT
Patients who received RRT, n/total n (%)	149/1,427 (10.4)	35/421 (8.3)	114/1,006 (11.3)
ICU mortality	76/149 (51.0)	13/35 (37.1)	63/114 (55.3)	0.092^&
Hospital mortality	80/149 (53.7)	17/35 (48.6)	63/114 (55.3)	0.617^&
ICU LOS (days), median (IQR)	26 (15-42)^¶	25 (12-48)^¶	27 (16-40)^¶	0.975^#
Hospital LOS (days), median (IQR)	34 (18-56)^¶	36 (17-56)^¶	33 (18-57)^¶	0.525^#
Patients who did not receive RRT, n/total n (%)	1,278/1,427 (89.6)	386/421 (91.7)	892/1,006 (88.7)
ICU mortality	82/1,278 (6.4)	31/386 (8.0)	51/892 (5.7)	0.154^&
Hospital mortality	94/1,273 (7.4)	34/386 (8.8)	60/887 (6.8)	0.244^&
ICU LOS (days), median (IQR)	8 (4-14)	7 (3-13)	8 (5-14)	0.033^#
Hospital LOS (days), median (IQR)	13 (9-19)	12 (8-19)	13 (9-19)	0.053^#
According to the use of ECMO
Patients who received ECMO, n/total n (%)	20/1,427 (1.4)	6/421 (1.4)	14/1,006 (1.4)
ICU mortality	10/20 (50.0)	1/6 (16.7)	9/14 (64.3)	0.141^$
Hospital mortality	11/20 (55.0)	2/6 (33.3)	9/14 (64.3)	0.336^$
ICU LOS (days), median (IQR)	25 (16-45)^‡	37 (22-55)^†	25 (12-40)^‡	0.353^#
Hospital LOS (days), median (IQR)	31 (16-49)^‡	49 (27-56)^†	26 (12-46)^Ψ	0.153^#
Patients who did not receive ECMO, n/total n (%)	1,407/1,427 (98.6)	415/421 (98.6)	992/1,006 (98.6)
ICU mortality	148/1,407 (10.5)	43/415 (10.4)	105/992 (10.6)	0.977^&
Hospital mortality	163/1,402 (11.6)	49/415 (11.8)	114/987 (11.6)	0.963^&
ICU LOS (days), median (IQR)	8 (5-16)	8 (4-15)	9 (5-16)	0.007^#
Hospital LOS (days), median (IQR)	13 (9-21)	12 (8-21)	13 (9-21)	0.020^#

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[TFN1] Values represent median (IQR) or n/n total (%).

[TFN2] * P values were calculated using; ^# Mann-Whitney U test; ^& χ² test; ^$ data available for 827 patients (First Wave: 295 patients, Second Wave: 532 patients); ^‡ patients were categorized according to their MFI values into Non-frail (MFI=0), Pre-frail (MFI=1-2) or Frail (MFI≥3).

[TFN3] SAPS 3: Simplified Acute Physiology Score 3, scores range from 0 to 217, with higher scores indicating more severe illness and higher risk of death; SOFA Score: Sequential Organ Failure Assessment Score, ranges from 0 to 24, with higher scores indicating more severe organ dysfunction; CCI: Charlson Comorbidity Index, based on a point scoring system (from 0 to 37) for the presence of specific associated diseases and is used for prognosis of lethality; MFI: Modified Frailty Index, values from 1 to 11, scored by assigning 1 point for each frailty components (11 possible comorbidities or deficits). COPD: chronic obstructive pulmonary disease; RRT: renal replacement therapy; ICU: intensive care unit.