The impact of bariatric and metabolic surgery on the morbidity and mortality of patients infected during the COVID-19 pandemic: a retrospective cohort study

ABSTRACT BACKGROUND: Since the impact of the coronavirus disease 2019 (COVID-19) pandemic in March 2020, several studies have shown a strong relationship between obesity and severe cases of COVID-19. It is imperative to assess whether bariatric surgery exerts a protective effect in such cases. OBJECTIVE: This study aimed to assess the impact of bariatric surgery on the morbidity and mortality in obese patients during the COVID-19 pandemic. A comprehensive search was performed using the PubMed and Cochrane Library databases. DESIGN AND SETTING: Retrospective cohort studies conducted in the Faculdade de Medicina da Universidade Cidade de São Paulo, São Paulo (SP), Brazil. METHODS: The search comprised the following descriptors: “bariatric, surgery, COVID-19”. Current retrospective cohort studies that examined the influence of bariatric surgery on the morbidity and mortality of obese patients during the COVID-19 pandemic were considered eligible. RESULTS: After removing duplicates, 184 studies were obtained from the databases. Of these, 181 were excluded from the analysis as they did not meet the eligibility criteria. Patients undergoing postoperative follow-up of bariatric surgery had a similar probability of SARS-CoV-2 infection compared to the general population, and persistent comorbidities were associated with an increased risk and severity of infection. CONCLUSION: Bariatric surgery has a protective effect against severe COVID-19 in the obese population, bringing the prevalence of severe disease cases to levels equivalent to those of the nonobese general population, with a positive impact on morbidity and mortality.


INTRODUCTION
In March 2020, the World Health Organization (WHO) declared the coronavirus disease 2019 (COVID-19) a pandemic. Since then, the impact of this infection on the public and private health systems of many countries has become evident. 1 The overcrowding of intensive care beds has led to the cancellation of elective surgeries, as there has been an increasing demand for professionals and and resources to treat infected patients. 2,3 In this context, Hussain et al. 4 presented a flowchart scaling priority among candidates for elective and revision procedures during the pandemic. Patients with severe obesity, comorbidities, or surgical complications should be prioritized when performing procedures. Outpatient activities began to be performed through telemedicine, and only urgent procedures such as early and late surgical complications remained in the usual routine.
Studies indicate obesity as an isolated risk factor for severe cases of COVID-19. [4][5][6] In addition, biochemical and endocrine factors related to obesity, such as type 2 diabetes and insulin resistance, are worse prognostic factors in infected patients. 7,8 Therefore, it has become imperative to evaluate whether bariatric surgery exerts a protective effect against severe covid-19 conditions. Retrospective studies have evaluated outcomes in patients with previous bariatric surgery infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) regarding the severity of the disease, need for intensive care and impact on mortality. 6,9,10 Table 1. Comprehensive search strategy for research on bariatric and metabolic surgery during the coronavirus-2019 pandemic using harvesting information retrieval framework

Search results
A total of 186 studies were obtained from the surveyed databases.
After removing duplicates, 184 studies were retained for the analysis. Of these, 181 were excluded after analyzing titles, abstracts, and full texts because they did not meet the eligibility criteria. Only three studies were included in this review (Figure 1).
The characterization of the participants included in the studies is shown in Table 2.
A description of studies evaluating the impact of bariatric surgery on the morbidity and mortality of obese patients during the COVID-19 pandemic is shown in Table 3.

DISCUSSION
Studies indicate obesity as an isolated risk factor for severe cases of COVID-19. [4][5][6] In addition, biochemical and endocrine factors related to obesity, such as type 2 diabetes and insulin resistance, are associated with a worse prognosis in infected patients. 7,8,11 In this context, the publications evaluated in this study explore bariatric surgery as an intervention capable of serving as a protective factor against severe cases of COVID-19. 6,9,10 There is great heterogeneity between the methodology of the studies since the situation of social isolation itself made it impossible to conduct controlled clinical trials.
The publication by Uccelli et al., 6 whose data collection was carried out from March to May 2020, presented many participants  6 2,145 44 Male and female Obesity Study Aminian et al. 9 Bel Lassen et al. 10 Uccelli et al. 6 Participants n = 363 tested positive for COVID-19 Group with previous surgery: 33; Group of nonoperated: 330 n = 738; All underwent bariatric surgery Group "probably infected": 62; Group "probably not infected": 676 n = 2,145; All underwent bariatric surgery

Goals
Investigate the relationship between previous metabolic surgery and the severity of COVID-19 in patients with severe obesity.
Estimate the prevalence of COVID-19 and evaluate factors associated with the incidence and severity of the disease in patients who underwent bariatric surgery.
Investigate the incidence of SARS-CoV-2 infection and its severity in patients who underwent bariatric surgery.

Collection procedures
A search was performed in medical records of the institution that conducted the study for patients who tested positive in RT-PCR for COVID-19, evaluating the rate and time of hospitalization, need for ICU, mechanical ventilation, dialysis, and mortality in patients who tested positive in RT-PCR for COVID-19, evaluating the rate and time of hospitalization, need for ICU, mechanical ventilation, dialysis and mortality.
A standardized questionnaire was conducted through telephone calls in which probable symptoms of COVID-19 were questioned, such as anosmia, fever, rhinorrhea, odynophagia, or patients who tested positive for the disease. In addition, a medical record search was performed for anthropometric and laboratory data before and after the patients.
A questionnaire was sent to patients previously submitted to bariatric surgery in which age, gender, BMI, origin, comorbidities, and type of surgery were questioned, and they were asked about the main symptoms of COVID-19, and occurrence of hospitalization and ICU admission.

Main findings
The mean preoperative BMI in the group with previous surgery was 49. In the group with previous surgery, none of these four outcomes were identified.
Patients had a mean age of 50 ± 12.3 years, with most being female (78.3%) and 44% having type 2 diabetes before surgery. The most used surgical technique was gastric bypass (54.4%), followed by sleeve gastrectomy (45.0%). The mean postoperative time at collection was 3.7 ± 2.7 years. There was no difference in the surgical technique outcomes between the groups. The mean postoperative time was significantly longer in the "probably infected" group, with a considerably higher proportion of persistently diabetic patients than in the "probably not infected" group.
All patients underwent elective bariatric surgery. The mean preoperative BMI was 44 ± 6.8 kg/m 2 with a reduction to 29.3 ± 5.5 kg/ m 2 in the postoperative period. The main technique used was laparoscopic sleeve gastrectomy (82.4%). The reduction in the number of comorbidities was almost entirely statistically significant. A total of 181 patients (8.4%) reported at least one symptom related to COVID-19. Nevertheless, only 26 cases (1.2%) were tested, and only 13 individuals (0.6%) tested positive. Six patients (0.3%) were admitted to hospital units; two patients (0.1%) required ICU with mechanical ventilation. The mean length of hospital stay was 23 ± 13 days.

Conclusions
The study identified that previous bariatric surgery is associated with lower hospitalization rates and the need for ICU for patients infected with SARS-CoV-2.
Patients under postoperative follow-up of bariatric surgery presented a probability of SARS-CoV-2infection similar to that of the general population. The persistence of type 2 diabetes and the presence of lower BMI are associated with increased risk and severity of SARS-CoV-2 infection.
Because the rate of hospitalization and need for ICU of the patients evaluated was equivalent to those of the general nonobese population, the study concludes that bariatric surgery can be considered a protective factor for severe acute respiratory syndrome caused by SARS-CoV-2 infection