Hidden blood loss and the risk factors after posterior lumbar fusion surgery: A retrospective study.

Hidden blood loss (HBL) plays an important role in perioperative rehabilitation of patients underwent posterior lumbar fusion surgery. This study was to calculate the volume of HBL and evaluate the risk factors among patients after posterior lumbar fusion surgery.A retrospective analysis was made on the clinical data of 143 patients underwent posterior lumbar fusion surgery from March 2017 to December 2017. Recording preoperative and postoperative hematocrit to calculate HBL according to Gross formula and analyzing its related factors including age, sex, height, weight, body mass index (BMI), surgery levels, surgical time, surgery types, duration of symptoms, disorder type, specific gravity of urine (SGU), plasma albumin (ALB), glomerular filtration rate (GFR), glucose (GLU), drainage volume, hypertension. Risk factors were further analyzed by multivariate linear regression analysis and t test.Eighty-six males and 57 females, mean age 52.7 ± 11.4 years, mean height 162 ± 7.0, mean weight 61.5 ± 9.4, were included in this study. The HBL was 449 ± 191 mL, with a percentage of 44.2% ± 16.6% in the total perioperative blood loss. Multivariate linear regression analysis revealed that patients with higher BMI (P = .026), PLIF procedures (P = .040), and more surgical time (P = .018) had a greater amount of HBL. Whereas age (P = 0.713), sex (P = .276), surgery levels (P = .921), duration of symptoms (P = .801), disorder type (P = .511), SGU (P = .183), ALB (P = .478), GFR (P = .139), GLU (P = .423), hypertension (P = .337) were not statistically significant differences with HBL.HBL is a large proportion of total blood loss in patients after posterior lumbar fusion surgery. BMI >24 kg/m, PLIF procedures, and more surgical time are risk factors of HBL. Whereas age, sex, surgery levels, duration of symptoms, disorder type, SGU, ALB, GFR, GLU, hypertension were not associated with HBL.