The effects of patient related factors on hidden and total blood loss in single-level open transforaminal lumbar interbody fusion surgery

OBJECTIVE: The aim of this retrospective study was to identify the amount of TBL and HBL and analyse the risk factors using multivariate linear regression analysis during single-level OTLIF surgery. METHODS: In this study 62 patients (32 male, 30 female, mean age 49.22 ± 13.26) who underwent single-level interbody fusion procedures by a single surgeon between 2015 and 2021 were included. Retrospectively, relevant statistics regarding body mass index (BMI), American Society of Anesthesiologist Score (ASA), preoperative mean arterial pressure (MAP), and age were gathered. Preoperative MR images were used to assess and measure radiological parameters such as skin-disc distance (SDA), canal area (CA), paravertebral muscle area (PVMA),lumbosacral maximum subcutaneous fat thickness (LSMSF), operation level subcutaneous fat thickness (OPSF) and spinous process length (SPL).Total blood loss (TBL) was calculated according to Nadler’s formula. Hidden blood loss (HBL) was measured by deducting the measured (visible) blood loss from TBL. TBL, HBL and their relationship with preoperative parameters were assessed. RESULTS: HBL was determined to be significantly higher in older patients (P = 0.012). MAP was seen to have a statistically significant correlation with operating time (P = 0.002), operative bleeding (P = 0.002), TBL (P = 0.006), and HBL (P = 0.001), and an inverse correlation with postoperative drainage (P = 0.007). The ASA scores were observed to be statistically significantly correlated with TBL (P = 0.001), and HBL (P = 0.001). LSMSF showed a significant correlation with TBL (P = 0.005) and HBL (P = 0.002). OPSF was determined to be correlated with TBL (P = 0.011), HBL (P = 0.009) and length of stay in hospital (P =0.034). SDD was correlated with TBL (P =0.043), and SPL with HBL (P = 0.013). It was shown that age (P =0.012), MAP (P =0.001), ASA (P =0.001), LSMFS (P = 0.002), OPSF (P = 0.009), SPL (P = 0.013) were risk factors for HBL. According to multivariate logistic regression analysis; two anatomical factors LSMSF and SPL were independent risk factors for HBL (P < 0.05). CONCLUSION: This results of this study have revealed that most patient-related parameters have a significant effect on HBL and TBL.The study has also demonstrated that LSMSF and SPL are independent risk factors for HBL. LEVEL OF EVIDENCE: Level IV, Therapeutic Study