Daniel D. Bohl

Hypoalbuminemia Independently Predicts Surgical Site Infection, Pneumonia, Length of Stay, and Readmission After Total Joint Arthroplasty

This study investigates the association between preoperative hypoalbuminemia, a marker for malnutrition, and complications during the 30 days after total joint arthroplasty. Patients who underwent elective primary total hip and knee arthroplasty as part of the American College of Surgeons National Surgical Quality Improvement Program were identified. Outcomes were compared between patients with and without hypoalbuminemia (serum albumin concentration <3.5 g/dL) with adjustment for patient and procedural factors. A total of 49603 patients were included. In comparison to patients with normal albumin concentration, patients with hypoalbuminemia had a higher risk for surgical site infection, pneumonia, extended length of stay, and readmission. Future efforts should investigate methods of correcting nutritional deficiencies prior to total joint arthroplasty. If successful, such efforts could lead to improvements in short-term outcomes for patients.

Using the ACS-NSQIP to identify factors affecting hospital length of stay after elective posterior lumbar fusion.

Study Design. Retrospective cohort study of the American College of Surgeons National Surgical Quality Improvement Program database from 2005 to 2010 that included 1861 patients who had undergone elective posterior lumbar fusion. Objective. To characterize factors that were independently associated with increased hospital length of stay (LOS) in patients who had undergone elective posterior lumbar fusion. Summary of Background Data. Posterior lumbar spine fusion is a common surgical procedure used to treat lumbar spine pathology. LOS is an important clinical variable and a major determinant of inpatient hospital costs. There is lack of studies in the literature using multivariate analysis to examine specifically the predictors of LOS after elective posterior lumbar fusion. Methods. Patients who underwent elective posterior lumbar fusion from 2005 to 2010 were identified in the American College of Surgeons National Surgical Quality Improvement Program database. Preoperative and intraoperative variables were extracted for each case and a multivariate linear regression was performed to assess the contribution of each variable to LOS. Results. A total of 1861 patients who had undergone elective posterior lumbar fusion were identified. The average age for patients in this cohort was 60.6 ± 13.9 years (mean ± standard deviation) with a body mass index of 30.3 ± 6.2 kg/m2. Of the total patients, 44.7% of patients were male. LOS was in the range from 0 days to 51 days. Multivariate linear regression identified age (P < 0.001), morbid obesity (body mass index ≥ 40 kg/m2, P < 0.001), American Society of Anesthesiologists class (P = 0.001), operative time (P < 0.001), multilevel procedure (P = 0.001), and intraoperative transfusion (P < 0.001) as significant predictors of extended LOS. Conclusion. The identified preoperative and intraoperative variables associated with extended LOS after elective posterior lumbar fusion may be helpful to clinicians for patient counseling and postoperative planning. Level of Evidence: 3

Postoperative length of stay and 30-day readmission after geriatric hip fracture: an analysis of 8434 patients.

Objectives: To identify factors associated with increased postoperative length of stay (LOS) and readmission after surgical repair of geriatric hip fractures. Methods: Patients aged 70 years and older who underwent hip fracture surgery from January 2011 through December 2012 were identified in the American College of Surgeons National Surgical Quality Improvement Program database. Patient characteristics were tested for association with postoperative LOS and readmission using bivariate and multivariate analyses. Results: For the 8434 patients with hip fracture identified, the average age was 83.8 ± 5.9 years (mean ± SD), and 26.9% were male. Average postoperative LOS was 5.6 ± 6.0 days. Ten percent were readmitted within the first 30 postoperative days. Increased postoperative LOS of at least 1 full day was associated with increased time from admission to surgery, non–general anesthesia, and procedure type on multivariate analysis. Readmission was associated with increased age, male sex, body mass index ≥35 kg/m2, American Society of Anesthesiologists class ≥3, pulmonary disease, hypertension, steroid use, dependent functional status, and discharge to a facility on multivariate analysis. Conclusions: Ten percent of patients were readmitted after hip fracture repair in this national sample. Preoperative time to surgery, anesthesia type, and implant selection are 3 risk factors for increased LOS that can potentially be modified. A clinically significant risk factor for readmission was body mass index ≥35 kg/m2, which was not associated with increased postoperative LOS. The identified risk factors illuminate opportunities for optimizing care for hip fracture patients aged 70 and older. Level of Evidence: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Patient characteristics associated with increased postoperative length of stay and readmission after elective laminectomy for lumbar spinal stenosis.

Study Design. Retrospective cohort. Objective. To identify factors that were independently associated with increased postoperative length of stay (LOS) and readmission in patients who underwent elective laminectomy for lumbar spinal stenosis. Summary of Background Data. Lumbar spinal stenosis is a common pathology that is traditionally treated with decompressive laminectomy. Risk factors associated with increased LOS and readmission have not been fully characterized for laminectomy. Methods. Patients who underwent laminectomy for lumbar spinal stenosis during 2011 and 2012 were identified from the American College of Surgeons National Surgical Quality Improvement Program database. Patient characteristics were tested for association with LOS and readmission using bivariate and multivariate analyses. Patients with LOS more than 10 days were excluded from the readmission analysis as the American College of Surgeons National Surgical Quality Improvement Program only captures readmissions within 30 postoperative days, and the window for potential readmission was deemed too short for patients staying longer than 10 days. Results. A total of 2358 patients who underwent laminectomy met inclusion criteria. The average age was 66.4 ± 11.7 years (mean ± standard deviation). Average postoperative LOS was 2.1 ± 2.6 days. Of those meeting criteria for readmission analysis, 3.7% of patients (86 of 2339) were readmitted within 30 days postoperatively. Independent risk factors for prolonged LOS were increased age (P < 0.001), increased body mass index (P = 0.004), American Society of Anesthesiologists class 3–4 (P = 0.005), and preoperative hematocrit less than 36.0 (P = 0.001). Independent risk factors for readmission were increased age (P = 0.013), increased body mass index (P = 0.040), American Society of Anesthesiologists class 3–4 (P < 0.001), and steroid use (P = 0.001). The most common reason for readmission was surgical site-related infections (25.0% of patients readmitted in 2012). Conclusion. The identified factors associated with LOS and readmission after lumbar laminectomy may be useful for optimizing patient care. Level of Evidence: 3

Administrative database concerns: accuracy of International Classification of Diseases, Ninth Revision coding is poor for preoperative anemia in patients undergoing spinal fusion.

Study Design. Cross-sectional study. Objective. To objectively evaluate the ability of International Classification of Diseases, Ninth Revision (ICD-9) codes, which are used as the foundation for administratively coded national databases, to identify preoperative anemia in patients undergoing spinal fusion. Summary of Background Data. National database research in spine surgery continues to rise. However, the validity of studies based on administratively coded data, such as the Nationwide Inpatient Sample, are dependent on the accuracy of ICD-9 coding. Such coding has previously been found to have poor sensitivity to conditions such as obesity and infection. Methods. A cross-sectional study was performed at an academic medical center. Hospital-reported anemia ICD-9 codes (those used for administratively coded databases) were directly compared with the chart-documented preoperative hematocrits (true laboratory values). A patient was deemed to have preoperative anemia if the preoperative hematocrit was less than the lower end of the normal range (36.0% for females and 41.0% for males). Results. The study included 260 patients. Of these, 37 patients (14.2%) were anemic; however, only 10 patients (3.8%) received an “anemia” ICD-9 code. Of the 10 patients coded as anemic, 7 were anemic by definition, whereas 3 were not, and thus were miscoded. This equates to an ICD-9 code sensitivity of 0.19, with a specificity of 0.99, and positive and negative predictive values of 0.70 and 0.88, respectively. Conclusion. This study uses preoperative anemia to demonstrate the potential inaccuracies of ICD-9 coding. These results have implications for publications using databases that are compiled from ICD-9 coding data. Furthermore, the findings of the current investigation raise concerns regarding the accuracy of additional comorbidities. Although administrative databases are powerful resources that provide large sample sizes, it is crucial that we further consider the quality of the data source relative to its intended purpose. Level of Evidence: 3

Risk Factors for Blood Transfusion with Primary Posterior Lumbar Fusion.

Study Design. Retrospective cohort study. Objective. To identify factors associated with blood transfusion for primary posterior lumbar fusion surgery, and to identify associations between blood transfusion and other postoperative complications. Summary of Background Data. Blood transfusion is a relatively common occurrence for patients undergoing primary posterior lumbar fusion. There is limited information available describing which patients are at increased risk for blood transfusion, and the relationship between blood transfusion and short‐term postoperative outcomes is poorly characterized. Methods. The American College of Surgeons National Surgical Quality Improvement Program (ACS‐NSQIP) database was used to identify patients undergoing primary posterior lumbar fusion from 2011 to 2013. Multivariate analysis was used to find associations between patient characteristics and blood transfusion, along with associations between blood transfusion and postoperative outcomes. Results. Out of 4223 patients, 704 (16.7%) had a blood transfusion. Age 60 to 69 (relative risk [RR] 1.6), age greater than equal to 70 (RR 1.7), American Society of Anesthesiologists class greater than equal to 3 (RR 1.1), female sex (RR 1.1), pulmonary disease (RR 1.2), preoperative hematocrit less than 36.0 (RR 2.0), operative time greater than equal to 310 minutes (RR 2.9), 2 levels (RR 1.6), and 3 or more levels (RR 2.1) were independently associated with blood transfusion. Interbody fusion (RR 0.9) was associated with decreased rates of blood transfusion. Receiving a blood transfusion was significantly associated with any complication (RR 1.7), sepsis (RR 2.6), return to the operating room (RR 1.7), deep surgical site infection (RR 2.6), and pulmonary embolism (RR 5.1). Blood transfusion was also associated with an increase in postoperative length of stay of 1.4 days (P < 0.001). Conclusion. 1 in 6 patients received a blood transfusion while undergoing primary posterior lumbar fusion, and risk factors for these occurrences were characterized. Strategies to minimize blood loss might be considered in these patients to avoid the associated complications. Level of Evidence: 3

Complication rates following elective lumbar fusion in patients with diabetes: insulin dependence makes the difference.

Study Design. Retrospective cohort. Objective. To determine the effect of non–insulin-dependent diabetes mellitus (NIDDM) and insulin-dependent diabetes mellitus (IDDM) on postoperative complications after elective lumbar fusion surgery. Summary of Background Data. Diabetes mellitus (DM) is a common chronic disease. The effects of NIDDM and IDDM on rates of postoperative complications, extended length of stay, and readmission after lumbar fusion surgery are not well established. Methods. A retrospective cohort study was conducted using the American College of Surgeons National Surgical Quality Improvement Program database. Patients undergoing lumbar fusion between 2005 and 2012 were identified and characterized as having NIDDM, IDDM, or neither. Bivariate and multivariate analyses were used to test patients with NIDDM and IDDM for increased risk of adverse postoperative outcomes over the initial 30 postoperative days. Results. A total of 15,480 patients who underwent lumbar fusion were identified (13,043 were patients without DM, 1,650 patients had NIDDM, and 787 patients had IDDM). NIDDM was independently associated with an increased risk of wound dehiscence (relative risk = 2.3; P = 0.033) and extended length of stay (1.2; P < 0.003). IDDM was independently associated with an increased risk of death (2.7; P = 0.020), sepsis (2.2; P = 0.002), septic shock (3.3; P = 0.032), unplanned intubation (2.8; P = 0.003), ventilator-assisted respiration for more than 48 hours postoperatively (2.8; P = 0.005), wound-related infection (1.9; P = 0.001), urinary tract infection (1.6; P = 0.011), pneumonia (3.1; P < 0.001), extended length of stay (1.5; P < 0.001), and readmission within 30 days (1.5; P = 0.036). Conclusion. Compared with patients without DM, IDDM was associated with an increased risk of a considerably higher number of postoperative complications than NIDDM. These complications were also of greater severity. This important designation may improve preoperative risk stratification and counseling of patients with diabetes prior to lumbar fusion surgery. Level of Evidence: 3

Factors Affecting Length of Stay and Complications After Elective Anterior Cervical Discectomy and Fusion: A Study of 2164 Patients From The American College of Surgeons National Surgical Quality Improvement Project Database (ACS NSQIP).

Study Design: Retrospective review of the prospective American College of Surgeons National Surgical Quality Improvement Project (ACS NSQIP) database with 30-day follow-up of 2164 patients undergoing elective anterior cervical discectomy and fusion (ACDF). Objective: To determine factors independently associated with increased length of stay (LOS) and complications after ACDF to facilitate preoperative planning and setting of realistic expectations for patients and providers. Summary of Background Data: The effect of individual preoperative factors on LOS and complications has been evaluated in small-scale studies. Large database analysis with multivariate analysis of these variables has not been reported. Methods: The ACS NSQIP database from 2005 to 2010 was queried for patients undergoing ACDF procedures. Preoperative and perioperative variables were collected. Multivariate regression determined significant predictors (P<0.05) of extended LOS and complications. Results: Average LOS was 2.0±4.0 days (mean±SD) with a range of 0–103 days. By multivariate analysis, age 65 years and above, functional status, transfer from facility, preoperative anemia, and diabetes were the preoperative factors predictive of extended LOS. Major complications, minor complications, and extended surgery time were the perioperative factors associated with increased LOS. The elongating effect of these variables was determined, and ranged from 0.5 to 5.0 days. Seventy-one patients (3.3%) had a total of 92 major complications, including return to operating room (40), venous thrombotic events (13), respiratory (21), cardiac (6), mortality (5), sepsis (4), and organ space infection (3). Multivariate analysis determined ASA score ≥3, preoperative anemia, age 65 years and above, extended surgery time, and male sex to be predictive of major complications (odds ratios ranging between 1.756 and 2.609). No association was found between levels fused and LOS or complications. Conclusion: Extended LOS after ACDF is associated with factors including age, anemia, and diabetes, as well as the development of postoperative complications. One in 33 patients develops a major complication postoperatively, which are associated with an increased LOS of 5 days.

Malnutrition Predicts Infectious and Wound Complications Following Posterior Lumbar Spinal Fusion

Study Design. A retrospective review of data collected prospectively by the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP). Objective. The aim of this study was to investigate the association between preoperative hypoalbuminemia, a marker for malnutrition, and complications during the 30 days following posterior lumbar fusion surgery. Summary of Background Data. Malnutrition is a potentially modifiable risk factor that may contribute to complications following spinal surgery. Although prior studies have identified associations between malnutrition, delayed wound healing, and surgical site infection (SSI), the evidence for such a relationship within spine surgery is mixed. Methods. Patients who underwent posterior lumbar spinal fusion of one to three levels as part of the ACS-NSQIP were identified. Patients without preoperative serum albumin concentration were excluded. Outcomes were compared between patients with and without hypoalbuminemia (defined as serum albumin concentration <3.5 g/dL). All comparisons were adjusted for baseline differences between populations. Results. Four thousand three hundred ten patients were included. The prevalence of hypoalbuminemia was 4.8%. In comparison to patients with normal albumin concentration, patients with hypoalbuminemia had a higher risk for occurrence of wound dehiscence [1.5% vs. 0.2%, adjusted relative risk (RR) = 5.8, P = 0.006], SSI (5.4% vs. 1.7%, adjusted RR = 2.3, P = 0.010), and urinary tract infection (5.4% vs. 1.5%, adjusted RR = 2.5, P = 0.005). Similarly, patients with hypoalbuminemia had a higher risk for unplanned hospital readmission within 30 days of surgery (11.7% vs. 5.4%, RR = 1.8, P < 0.001). Finally, patients with hypoalbuminemia had a longer mean inpatient stay (5.2 vs. 3.7 days, RR = 1.2, P < 0.001). Conclusion. The present study suggests that malnutrition is an independent risk factor for infectious and wound complications following posterior lumbar fusion. Malnutrition was also associated with an increased length of stay and readmission. Future studies should evaluate methods of correcting malnutrition before lumbar spinal surgery. Such efforts have the potential to meaningfully decrease the rates of adverse events following this procedure. Level of Evidence: 3

Timing of Complications After Spinal Fusion Surgery.

Study Design. Retrospective cohort study. Objective. To characterize the timing of complications after spinal fusion procedures. Summary of Background Data. Despite many publications on risk factors for complications after spine surgery, there are few publications on the timing at which such complications occur. Methods. Patients undergoing anterior cervical decompression and fusion (ACDF) or posterior lumbar fusion (PLF; with or without interbody) procedures during 2011–2013 were identified in the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database. For each of 8 different complications, the median time from surgery until complication was determined, along with the interquartile range and middle 80%. Results. A total of 12,067 patients undergoing ACDF and 11,807 patients undergoing PLF were identified. For ACDF, the median day of diagnosis (and interquartile range; middle 80%) for anemia requiring transfusion was 0 (0–1; 0–2), myocardial infarction 2 (1–5; 0–15), pneumonia 4 (2–9; 1–14), pulmonary embolism 5 (2–9; 1–10), deep vein thrombosis 10.5 (7–16.5; 5–21), sepsis 10.5 (4–18; 1–23), surgical site infection 13 (8–19; 5–25), and urinary tract infection 17 (8–22; 4–26). For PLF, the median day of diagnosis (and interquartile range; middle 80%) for anemia requiring transfusion was 0 (0–1; 0–2), myocardial infarction 2 (1–4; 1–8), pneumonia 4 (2–9; 1–17), pulmonary embolism 5 (3–11; 2–17), urinary tract infection 7 (4–14; 2–23), deep vein thrombosis 8 (5–16; 3–20), sepsis 9 (4–16; 2–22), and surgical site infection 17 (13–22; 9–27). Conclusion. These precisely described postoperative time periods enable heightened clinical awareness among spine surgeons. Spine surgeons should have the lowest threshold for testing for each complication during the time period of greatest risk. Authors, reviewers, and surgeons utilizing research on postoperative complications should carefully consider the impact that the duration of follow-up has on study results. Level of Evidence: 3