SPINE Volume 39, Number 10, pp 833-840 ©2014, Lippincott Williams & Wilkins
HEALTH SERVICES RESEARCH
Patient Characteristics Associated With Increased Postoperative Length of Stay and Readmission After Elective Laminectomy for Lumbar Spinal Stenosis Bryce A. Basques, BS, Arya G. Varthi, MD, Nicholas S. Golinvaux, BA, Daniel D. Bohl, MPH, and Jonathan N. Grauer, MD
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 From the Department of Orthopaedics and Rehabilitation, Yale University School of Medicine. Acknowledgment date: January 23, 2014. First revision date: January 31, 2014. Acceptance date: February 1, 2014. The manuscript submitted does not contain information about medical device(s)/drug(s). National Center for Advancing Translational Sciences of the National Institutes of Health under award number TL1TR000141 funds were received to support this work. Relevant financial activities outside the submitted work: grant, consultancy, and expert testimony. Address correspondence and reprint requests to Jonathan N. Grauer, MD, Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, 800 Howard Ave, New Haven, CT; E-mail: jonathan.grauer@yale. edu DOI: 10.1097/BRS.0000000000000276 Spine
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. Key words: lumbar, spinal stenosis, laminectomy, decompression, length of stay, readmission, age, body mass index, obesity, American Society of Anesthesiologists, anemia, functional status, steroid, infection. Level of Evidence: 3 Spine 2014;39:833–840
L
umbar spinal stenosis (LSS) is a degenerative condition that is a major cause of lumbar-related symptoms. In 2007, more than 37,000 operations were performed on patients with a primary diagnosis of LSS in the United States at a total cost of $1.7 billion.1,2 LSS is most commonly treated with decompressive lumbar laminectomy.1 Patients undergoing lumbar laminectomy are at risk for postoperative complications and prolonged hospital stays.3 Although several prior studies have examined factors predicting complications,2,4–12 little is known about which factors are independently associated with prolonged postoperative length of stay (LOS) and readmission. In addition to increasing costs for both patients and hospitals, extended LOS and readmission are associated with increased risk of postoperative complications and morbidity.13–16 In this study, we aim to identify patient characteristics that are independently associated with prolonged LOS and readmission after lumbar laminectomy on a large cohort of patients with LSS from a national database using multivariate analysis. This information may be useful for preoperative counseling, inpatient discharge planning, and optimizing postoperative care given to patients with LSS. www.spinejournal.com
833
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE140141_LR 833
01/04/14 11:31 AM
HEALTH SERVICES RESEARCH MATERIALS AND METHODS Data Source A waiver was issued for this study by our institution’s Human Investigations Committee. For this study, we used the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database, which captures data from more than 370 participating United States hospitals.17 In the ACS-NSQIP, more than 150 patient variables are prospectively abstracted from operative reports, medical records, and patient interviews to assess 30-day adjusted surgical outcomes.17,18 Patients are identified prospectively and randomly sampled at eligible hospitals. Clinical data are collected in the entire 30-day postoperative period, regardless of discharge status within this time.
Data Collection The ACS-NSQIP database from 2011 and 2012 was queried to identify patients who underwent laminectomy for LSS. Patients were initially selected by a postoperative diagnosis of LSS (International Classification of Diseases, Ninth Revision, codes 724.02 and 724.03). From these patients, only those with the primary Current Procedural Terminology code for lumbar laminectomy (63047) were included in the analysis. Patients undergoing other spinal procedures including lumbar fusion, patients undergoing urgent or emergent surgery, or those with previous evidence of infection were excluded from the analysis. Among the variables available in the ACS-NSQIP database are patient characteristics including sex, age, height, weight, and a history of smoking within one year.17 Body mass index (BMI) was calculated from each patient’s height and weight. The ACS-NSQIP database also includes information on medical comorbidities, including any history of diabetes, hypertension, pulmonary comorbidities, cardiac comorbidities, and American Society of Anesthesiologists (ASA) class. A history of pulmonary disease was defined as a history of dyspnea, severe chronic obstructive pulmonary disease, ventilator-assisted respiration within 48 hours before surgery, or current pneumonia. A history of heart disease was defined as a history of congestive heart failure within 30 days before admission, myocardial infarction within 6 months before admission, angina within 1 month before admission, cardiac surgery, or percutaneous coronary intervention. ASA class 3 or more corresponds to severe systemic disease. Steroid use was defined as requiring regular administration of oral or parenteral corticosteroid medications in the 30 days prior to surgery. Patients with hematocrit 36.0 or more or not drawn were defined as having normal preoperative hematocrit, and hematocrit less than 36.0 was defined as low. Functional status was defined as the patient’s ability to perform the activities of daily living within the 30 days prior to surgery. As of 2011, the ACS-NSQIP started collecting information about a patient’s discharge destination.17 For readmission analysis, patients were grouped on the basis of whether they were discharged to home or a facility. 834
Laminectomy LOS and Readmission • Basques et al
In 2012, the ACS-NSQIP began recording suspected reasons for readmission and the total days from the operation to readmission.17 Suspected reasons for readmission are entered into the database as either a category (such as superficial surgical site infection) or specified by an International Classification of Diseases, Ninth Revision, diagnosis code. The number of days between discharge and readmission was calculated by subtracting each patient’s LOS from the days between operation and readmission. Suspected reasons for readmission and the total days from discharge to readmission were tabulated for those patients who underwent laminectomy in 2012.
Length of Stay LOS was defined as the number of calendar days from the operation to hospital discharge. LOS was treated as a continuous variable for analysis.
Readmission Thirty-day readmission data in the ACS-NSQIP was first collected in 2011. For this study, readmission was defined as positive when a patient had an unplanned readmission one or more times. Readmission is tracked for the 30-day period after the operation. As this 30-day period includes the time before discharge, only patients with LOS 10 days or less (99th percentile LOS in this cohort) were included in the readmission analysis to leave a large enough window to capture readmissions.
Analysis Statistical analyses were conducted using STATA version 11.2 (StataCorp, LP, College Station, TX). All tests were 2-tailed, and the statistical difference was established at a 2-sided α level of 0.05 (P < 0.05). Demographic and comorbidity variables were tested for association with LOS using bivariate and multivariate linear regression. Only preoperative variables (all variables except discharge destination and LOS) were used to create a predictive model that was useful for preoperative counseling and planning, unlike a model containing intraoperative and/or postoperative variables. Preoperative data, discharge destination, and LOS were then tested for association with readmission using bivariate and multivariate logistic regression. Discharge destination and LOS were included in the readmission analysis because this information would be available at the time of discharge and would be useful to include in a model that predicts odds of readmission. For the readmission analysis, LOS was dichotomized at the median LOS. Final multivariate models were constructed using a backward stepwise process that initially included all potential variables and sequentially excluded variables with the highest P value until only those with P < 0.20 remained. Variables with 0.05 < P < 0.20 were left in the model to control for potential confounding, but were not considered to be significantly associated with the outcome.
www.spinejournal.com
May 2014
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE140141_LR 834
01/04/14 11:31 AM
HEALTH SERVICES RESEARCH
Laminectomy LOS and Readmission • Basques et al
RESULTS Patient Demographics and Comorbidities A total of 2358 patients who underwent laminectomy met inclusion criteria. A summary of patient demographics and comorbidities can be found in Table 1. The average age was 66.4 ± 11.7 years (mean ± standard deviation). The cohort was 40.4% female. The remaining patient characteristics are listed in the table.
Length of Stay
Average LOS was 2.1 ± 2.6 days and was in the range from 0 days (same-day discharge) to 61 days (Figure 1). Median LOS was 2 days. Bivariate linear regression was performed to test the association of each individual demographic and comorbidity variable with LOS. These results can be found in the bivariate analyses columns of Table 2. Unstandardized beta coefficients
TABLE 1. Demographics and Comorbidities of
Patients Who Undergo Laminectomy n
%
2358
100.0
18–59
630
26.7
60–69
723
30.7
70–79
702
29.8
≥80
303
12.9
952
40.4
18–25
412
17.6
25–30
822
35.1
30–35
651
27.8
≥35
456
19.5
ASA 3–4
1192
50.6
History of diabetes
475
20.1
History of smoking
376
16.0
History of pulmonary disease
255
10.8
History of hypertension
1542
65.4
History of heart disease
113
4.8
Steroid use
83
3.5
Preoperative hematocrit
HEALTH SERVICES RESEARCH
Patient Characteristics Associated With Increased Postoperative Length of Stay and Readmission After Elective Laminectomy for Lumbar Spinal Stenosis Bryce A. Basques, BS, Arya G. Varthi, MD, Nicholas S. Golinvaux, BA, Daniel D. Bohl, MPH, and Jonathan N. Grauer, MD
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 From the Department of Orthopaedics and Rehabilitation, Yale University School of Medicine. Acknowledgment date: January 23, 2014. First revision date: January 31, 2014. Acceptance date: February 1, 2014. The manuscript submitted does not contain information about medical device(s)/drug(s). National Center for Advancing Translational Sciences of the National Institutes of Health under award number TL1TR000141 funds were received to support this work. Relevant financial activities outside the submitted work: grant, consultancy, and expert testimony. Address correspondence and reprint requests to Jonathan N. Grauer, MD, Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, 800 Howard Ave, New Haven, CT; E-mail: jonathan.grauer@yale. edu DOI: 10.1097/BRS.0000000000000276 Spine
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. Key words: lumbar, spinal stenosis, laminectomy, decompression, length of stay, readmission, age, body mass index, obesity, American Society of Anesthesiologists, anemia, functional status, steroid, infection. Level of Evidence: 3 Spine 2014;39:833–840
L
umbar spinal stenosis (LSS) is a degenerative condition that is a major cause of lumbar-related symptoms. In 2007, more than 37,000 operations were performed on patients with a primary diagnosis of LSS in the United States at a total cost of $1.7 billion.1,2 LSS is most commonly treated with decompressive lumbar laminectomy.1 Patients undergoing lumbar laminectomy are at risk for postoperative complications and prolonged hospital stays.3 Although several prior studies have examined factors predicting complications,2,4–12 little is known about which factors are independently associated with prolonged postoperative length of stay (LOS) and readmission. In addition to increasing costs for both patients and hospitals, extended LOS and readmission are associated with increased risk of postoperative complications and morbidity.13–16 In this study, we aim to identify patient characteristics that are independently associated with prolonged LOS and readmission after lumbar laminectomy on a large cohort of patients with LSS from a national database using multivariate analysis. This information may be useful for preoperative counseling, inpatient discharge planning, and optimizing postoperative care given to patients with LSS. www.spinejournal.com
833
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE140141_LR 833
01/04/14 11:31 AM
HEALTH SERVICES RESEARCH MATERIALS AND METHODS Data Source A waiver was issued for this study by our institution’s Human Investigations Committee. For this study, we used the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database, which captures data from more than 370 participating United States hospitals.17 In the ACS-NSQIP, more than 150 patient variables are prospectively abstracted from operative reports, medical records, and patient interviews to assess 30-day adjusted surgical outcomes.17,18 Patients are identified prospectively and randomly sampled at eligible hospitals. Clinical data are collected in the entire 30-day postoperative period, regardless of discharge status within this time.
Data Collection The ACS-NSQIP database from 2011 and 2012 was queried to identify patients who underwent laminectomy for LSS. Patients were initially selected by a postoperative diagnosis of LSS (International Classification of Diseases, Ninth Revision, codes 724.02 and 724.03). From these patients, only those with the primary Current Procedural Terminology code for lumbar laminectomy (63047) were included in the analysis. Patients undergoing other spinal procedures including lumbar fusion, patients undergoing urgent or emergent surgery, or those with previous evidence of infection were excluded from the analysis. Among the variables available in the ACS-NSQIP database are patient characteristics including sex, age, height, weight, and a history of smoking within one year.17 Body mass index (BMI) was calculated from each patient’s height and weight. The ACS-NSQIP database also includes information on medical comorbidities, including any history of diabetes, hypertension, pulmonary comorbidities, cardiac comorbidities, and American Society of Anesthesiologists (ASA) class. A history of pulmonary disease was defined as a history of dyspnea, severe chronic obstructive pulmonary disease, ventilator-assisted respiration within 48 hours before surgery, or current pneumonia. A history of heart disease was defined as a history of congestive heart failure within 30 days before admission, myocardial infarction within 6 months before admission, angina within 1 month before admission, cardiac surgery, or percutaneous coronary intervention. ASA class 3 or more corresponds to severe systemic disease. Steroid use was defined as requiring regular administration of oral or parenteral corticosteroid medications in the 30 days prior to surgery. Patients with hematocrit 36.0 or more or not drawn were defined as having normal preoperative hematocrit, and hematocrit less than 36.0 was defined as low. Functional status was defined as the patient’s ability to perform the activities of daily living within the 30 days prior to surgery. As of 2011, the ACS-NSQIP started collecting information about a patient’s discharge destination.17 For readmission analysis, patients were grouped on the basis of whether they were discharged to home or a facility. 834
Laminectomy LOS and Readmission • Basques et al
In 2012, the ACS-NSQIP began recording suspected reasons for readmission and the total days from the operation to readmission.17 Suspected reasons for readmission are entered into the database as either a category (such as superficial surgical site infection) or specified by an International Classification of Diseases, Ninth Revision, diagnosis code. The number of days between discharge and readmission was calculated by subtracting each patient’s LOS from the days between operation and readmission. Suspected reasons for readmission and the total days from discharge to readmission were tabulated for those patients who underwent laminectomy in 2012.
Length of Stay LOS was defined as the number of calendar days from the operation to hospital discharge. LOS was treated as a continuous variable for analysis.
Readmission Thirty-day readmission data in the ACS-NSQIP was first collected in 2011. For this study, readmission was defined as positive when a patient had an unplanned readmission one or more times. Readmission is tracked for the 30-day period after the operation. As this 30-day period includes the time before discharge, only patients with LOS 10 days or less (99th percentile LOS in this cohort) were included in the readmission analysis to leave a large enough window to capture readmissions.
Analysis Statistical analyses were conducted using STATA version 11.2 (StataCorp, LP, College Station, TX). All tests were 2-tailed, and the statistical difference was established at a 2-sided α level of 0.05 (P < 0.05). Demographic and comorbidity variables were tested for association with LOS using bivariate and multivariate linear regression. Only preoperative variables (all variables except discharge destination and LOS) were used to create a predictive model that was useful for preoperative counseling and planning, unlike a model containing intraoperative and/or postoperative variables. Preoperative data, discharge destination, and LOS were then tested for association with readmission using bivariate and multivariate logistic regression. Discharge destination and LOS were included in the readmission analysis because this information would be available at the time of discharge and would be useful to include in a model that predicts odds of readmission. For the readmission analysis, LOS was dichotomized at the median LOS. Final multivariate models were constructed using a backward stepwise process that initially included all potential variables and sequentially excluded variables with the highest P value until only those with P < 0.20 remained. Variables with 0.05 < P < 0.20 were left in the model to control for potential confounding, but were not considered to be significantly associated with the outcome.
www.spinejournal.com
May 2014
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. SPINE140141_LR 834
01/04/14 11:31 AM
HEALTH SERVICES RESEARCH
Laminectomy LOS and Readmission • Basques et al
RESULTS Patient Demographics and Comorbidities A total of 2358 patients who underwent laminectomy met inclusion criteria. A summary of patient demographics and comorbidities can be found in Table 1. The average age was 66.4 ± 11.7 years (mean ± standard deviation). The cohort was 40.4% female. The remaining patient characteristics are listed in the table.
Length of Stay
Average LOS was 2.1 ± 2.6 days and was in the range from 0 days (same-day discharge) to 61 days (Figure 1). Median LOS was 2 days. Bivariate linear regression was performed to test the association of each individual demographic and comorbidity variable with LOS. These results can be found in the bivariate analyses columns of Table 2. Unstandardized beta coefficients
TABLE 1. Demographics and Comorbidities of
Patients Who Undergo Laminectomy n
%
2358
100.0
18–59
630
26.7
60–69
723
30.7
70–79
702
29.8
≥80
303
12.9
952
40.4
18–25
412
17.6
25–30
822
35.1
30–35
651
27.8
≥35
456
19.5
ASA 3–4
1192
50.6
History of diabetes
475
20.1
History of smoking
376
16.0
History of pulmonary disease
255
10.8
History of hypertension
1542
65.4
History of heart disease
113
4.8
Steroid use
83
3.5
Preoperative hematocrit
