Obesidade, cirurgia de desvio gástrico em Y-de-Roux e anemia: uma análise multivariada usando equações de estimativas generalizadas

Abstract

Obesity, Roux-en-Y gastric bypass surgery, and anemia: a multivariate analysis using generalized estimating equations Introduction: Roux-en-Y gastric bypass (RYGB) surgery, although efficient in restricting energy intake and promoting the treatment of obesity, leads to deficiencies of iron, vitamin B9, and vitamin B12, among other essential nutrients. Despite the nutritional supplementation operated patients are advised to do throughout the rest of their lives, the development of anemia is a common sequela of that surgery. Objective: In this context, the present study aimed to investigate the development of anemia using the Generalized Estimating Equations (GEE) technique. Methods: The tendency to anemia was investigated in three GEE models using red blood cell count (erythrocytes), mean cell volume (MCV), and the red cell distribution width (RDW) as dependent variables, and factors that could be associated with the development of anemia, such as time after surgery, sex, body mass index (BMI), serum iron, ferritin, vitamin B9, and vitamin B12. The studied sample, consisting of individuals submitted to RYGB, was retrospectively analyzed at six different moments of the study (before and 1, 3, 6, 12, and over 12 months after surgery). The data were collected from the patient's medical records in the Hospital Information System of the Unified Health System of Brazil. Results: Model 1 (n = 50), with RBC as a dependent variable, revealed that RBC count decreased with the decrease in IMC and erythrocyte hemoglobin content. Model 2 (n = 50), which has MCV as a dependent variable, revealed a discrepant lifting trend in MCV values with elevation in vitamin B12 levels about three months after surgery. However, the influence of MCV in this model was minimal due to the low value obtained for Wald coefficient B, and the model adjustment quality was very precarious due to the high value obtained for the QUICc (Quasi-likelihood Under the Independence model Criterion corrected). Model 3 (n = 49), with RDW as a dependent variable, showed an increase of this variable with a decrease in hemoglobin and not with the serum iron levels one and six months after surgery. Conclusion: After bariatric surgery, the tendency to anemia could not be explained based on the availability of circulating iron but by decreased BMI values and hemoglobin levels. The association of the tendency to anemia with decreased hemoglobin suggests that this tendency to anemia is occurring due to essential amino acid deficiency, with a decrease in the production of hemoglobin. Keywords: Body Mass Index; Bariatric Surgery; Rou-en-Y Bypass; Anemia; Iron; Ferritin; Vitamin B9; Vitamin B12.