Article
Risk Factors for 30-Day Hospital Readmission in Patients Undergoing Treatment for Peripheral Artery Disease
Vascular and Endovascular Surgery 2015, Vol. 49(3-4) 69-74 ª The Author(s) 2015 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/1538574415593498 ves.sagepub.com
Sukgu M. Han, MD1, Bian Wu, MD1, Charles M. Eichler, MD1, Linda M. Reilly, MD1, Shant M. Vartanian, MD1, Michael S. Conte, MD1, and Jade Hiramoto, MD1
Abstract Early hospital readmission among vascular surgery patients is a focus of Medicare’s new reimbursement structure. We aim to identify factors associated with 30-day readmission after lower extremity interventions to treat peripheral artery disease (PAD). Retrospective analysis of 174 consecutive patients discharged from the vascular surgery service between January 1, 2011, and July 31, 2012, after procedures for lower extremity PAD was performed. Of 174 patients, 37 were readmitted within 30 days of discharge. There were no significant differences in baseline characteristics between the readmitted and the nonreadmitted groups. In a multivariate logistic regression model, urgent operation and advanced chronic kidney disease (CKD) were associated with increased risk of 30-day readmission. The most common reasons for readmission were infection of the surgical site or index limb (18 of 37), followed by unresolved limb symptoms (13 of 37). The 30-day readmission is frequent after lower extremity interventions to treat PAD. Urgent operative intervention and advanced CKD appear to be risk factors for early hospital readmission. Keywords peripheral vascular disease, critical limb ischemia, readmission
Introduction In accordance with the Patient Protection and Affordable Care Act of 2010, the Center for Medicare and Medicaid Services has proposed policy changes restructuring reimbursement in an effort to reduce costs associated with hospital readmissions. In addition, risk-adjusted rates of 30-day hospital readmissions will be publicly reported in the near future.1 According to national Medicare claims data from 2003 to 2004, vascular surgical patients have high rates of hospital readmissions, second only to patients with congestive heart failure.2 However, available data on hospital readmissions following vascular surgical procedures are limited, and those derived from heterogeneous administrative databases may lack an appropriate level of detail to delineate the clinical risk factors associated with these readmissions.1-11 Although readmission rates after vascular surgical procedures vary widely, peripheral vascular procedures, especially those for critical limb ischemia (CLI), have been associated with a 30-day readmission rate greater than 20%.8-10,12 It is difficult to determine an ‘‘acceptable’’ rate of unplanned readmission after vascular surgical procedures, given that types of procedures and patient populations vary between different studies. In addition, patients with CLI may undergo staged procedures that necessitate return to the hospital within 30 days.
Institutional studies have identified dialysis dependence, congestive heart failure, and tissue loss as risk factors for readmission after lower extremity bypass procedures.3 In the future, hospitals with higher than expected readmission rates will be penalized financially.1 However, benchmark hospital readmission rates after vascular surgery procedures have not been established nor has a risk-adjusted model been developed. The purpose of our study was to determine the 30-day hospital readmission rate after lower extremity interventions to treat peripheral artery disease (PAD) and to identify risk factors associated with early readmission.
Methods This was a retrospective review of a prospective cohort of 174 patients who were discharged following interventions for lower extremity PAD at the University of California San Francisco, 1
Division of Vascular and Endovascular Surgery, Department of Surgery, University of California San Francisco, San Francisco, CA, USA Corresponding Author: Sukgu M. Han, University of California San Francisco, 400 Parnassus Ave, Room A-581, San Francisco, CA 94143, USA. Email: [email protected]
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from January 2011 to July 2012. These interventions included endovascular and open revascularizations as well as major and minor amputations. Patients who died during the hospitalization were excluded from the analysis. Patients who underwent revascularization for vascular trauma or adjunct endovascular procedures for previously placed aortic stent grafts were also excluded. The primary outcome variable was 30-day readmission to the hospital from the initial discharge, following the index procedure. For patients who underwent more than 1 procedure during the study interval, only the initial index procedure and hospitalization were included; hence, no patient was included more than once in this study. In cases where a patient had multiple 30-day readmissions during the study period, only the initial readmission was included in order to accurately characterize patient-related factors. We categorized the readmission types as related or unrelated to the index vascular procedure and planned or unplanned.12 To further validate the relationship with the index procedure, we identified the readmission diagnosis and admitting service. Planned readmissions included any admissions associated with elective procedures that were designed as part of multistaged procedures, those scheduled at the time of discharge, and those electively scheduled during outpatient clinic visits. Baseline patient characteristics included in this study were extracted from the electronic medical record and included age, gender, and race. Medical comorbidities included a history of diabetes, hypertension, coronary artery disease, congestive heart failure, arrhythmias, cerebrovascular accident, chronic obstructive pulmonary disease, chronic kidney disease (CKD), and dialysis dependence. Glomerular filtration rates (GFRs) were calculated using Modification of Diet in Renal Disease protocol. Advanced CKD was defined as stage IV (GFR < 30 mL/min/1.73 m2) or stage V (hemodialysis dependence). The lowest GFR within 3 months prior to the index procedure was used in the analysis. Smoking history was dichotomized to nonsmokers and current/prior smokers. Limb ischemia was recorded as acute or chronic, and the degree of ischemia (claudication, rest pain, tissue loss, or gangrene) was noted. An urgent operation was defined as a procedure performed within 24 hours of an unscheduled admission. Functional status was categorized as ambulatory, wheelchair dependent, or bed bound. Discharge destination was recorded as home, rehabilitation center/skilled nursing facility, or transfer to an inpatient hospital. Statistical analyses were performed using STATA 12 software (StataCorp LP, College Station, Texas). Proportions between groups were compared using the chi-square or Fisher exact tests, and continuous variables between groups were compared using the Student t test. Multivariable predictors of 30-day hospital readmission were analyzed by a logistic regression model. A P value .20 was used as the threshold for inclusion in the multivariate regression model.
Results Patient Characteristics Of the 174 consecutive patients discharged after lower extremity vascular surgical procedures, 37 (21%) were readmitted within
30 days of the initial discharge. The mean age was 69 + 11.5 years, 65% were male, and 66% were Caucasian. The mean length of hospital stay following the index procedure was 7.6 days, and 21% underwent an urgent operation (Table 1).
Procedures Performed During Index Hospitalization Forty-six patients underwent percutaneous endoluminal intervention to treat occlusive disease of the iliac, femoral, popliteal, and tibial arteries. Eighteen patients underwent angioplasty alone, while 17 patients underwent infrainguinal stent placement and 2 patients received iliac stents. Nine patients had thrombolysis of occluded stents or bypass grafts. All patients with thrombolysis were taken back to the operating department within 24 hours for repeat angiography, where angioplasty was performed in 7 and stenting in 1. Ninety-one (57%) patients underwent open revascularization procedures to treat lower extremity PAD. Eighteen of these patients underwent open bypass for aortoiliac occlusive disease, while 73 patients had open infrainguinal revascularization. An additional 13 patients underwent combined open and endovascular revascularization (iliac stents were combined with various open reconstructions in 8 patients, and 5 patients had femoral endarterectomy with distal superficial femoral artery (SFA) angioplasty or stents). Foot debridement with or without minor amputations below the ankle were performed in 20 patients. Three patients received primary below-knee amputations, while 1 patient had an above-knee amputation. There were a total of 36 (21%) urgent procedures performed. Fourteen of these patients presented with acute limb ischemia, while 10 had wet gangrene requiring emergent debridement, 10 had threatened bypass grafts, 1 had a bypass graft infection, and 1 had an anastomotic pseudoaneurysm.
Degree of Ischemia On initial presentation, signs of critical limb ischemia were present in 112 (64%) patients. Thirty-six of these patients had rest pain, while 76 had tissue loss. An additional 14 patients presented with signs of acute limb ischemia, all of which required urgent procedures. Thirty-nine patients presented with claudication. Five patients had asymptomatic stenosis of a previous bypass graft detected by surveillance duplex ultrasound. Four patients had infection of a previous bypass graft.
Description of Readmissions Of 37 readmissions, 31 were related to the index procedure (Table 2). Infection either at the surgical site or involving the index limb was the most frequent reason for readmission (18/ 37 ¼ 49%). The groin incision was the site of infection in 6 of these 18 patients. Twelve patients had infection involving the leg incisions or amputation site. Only 3 of these patients had their surgical site infection diagnosed during the index admission. Eleven of these 18 patients readmitted with infection underwent surgical debridement, while 7 were managed with intravenous antibiotics. Only 3 of these 18 patients were claudicants at initial presentation, and the remainder presented with CLI.
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Table 1. Patient Characteristics.
Number Age Male gender Race White Black Hispanic Asian Others DM Hypertension CAD CHF Hyperlipidemia Stroke Advanced CKD (stage IV or V) COPD Smoking VTE Atrial fibrillation Length of stay, days Urgent operation Re-do operation Functional status at discharge Ambulatory Wheelchair bound Bedbound Operation performed Aortoiliac revascularization Open infrainguinal revascularizationbypass Percutaneous endoluminal revascularization Major amputation Hybrid BPG þ angio Debridement þ minor amputation Discharge destination Home Home health Skilled nursing facility Acute care at outside hospital AMA
Total
Nonreadmitted
Readmitted
174 69.0 + 11.5 111 (64%)
137 68.8 + 11.4 66%
37 68.7 + 11.4 54%
116 17 17 15 9 82 146 67 20 95 23 34 31 113 10 19 7.6 36 17
93 12 15 9 8 68 113 53 16 77 19 22 24 92 8 14 7.68 23 13
23 5 2 6 1 14 33 14 4 18 4 12 7 21 2 5 7.65 13 4
(66%) (10%) (10%) (9%) (5%) (47%) (84%) (39%) (12%) (55%) (13%) (19%) (18%) (65%) (6%) (11%) + 5.1 (21%) (10%)
147 (85%) 19 (11%) 8 (5%)
(67%) (9%) (11%) (7%) (6%) (50%) (82%) (39%) (12%) (56%) (14%) (16%) (17%) (67%) (6%) (10%) (17%) (9%)
119 (86%) 14 (10%) 4 (3%)
(62%) (14%) (5%) (16%) (3%) (38%) (89%) (37%) (11%) (49%) (11%) (33%) (19%) (57%) (5%) (14%) (35%) (11%)
P Value .87 .15 .25
.20 .33 .86 .8 .39 .64 .02 .83 .23 .93 .65 .7 .02 .81 .08
28 (76%) 5 (13%) 4 (11%) .32
18 73 46 4 13 20
(11%) (42%) (26%) (2.%) (8%) (11%)
16 59 36 2 11 13
(12%) (43%) (26%) (1.5%) (8%) (9%)
2 14 10 2 2 7
(5.4%) (38%) (27%) (5.4%) (5.4%) (19%)
93 34 36 7 4
(53%) (20%) (21%) (4%) (2.3%)
77 23 27 7 3
(56%) (17%) (20%) (5%) (2.2%)
16 11 9 0 1
(43%) (30%) (24%)
.23
(2.7%)
Abbreviations: CKD, chronic kidney disease; COPD, chronic obstructive pulmonary disease; DM, diabetes mellitus; VTE, venous thromboembolism; AMA, against medical advice; BPG, bypass graft; CAD, coronary artery disease; CHF, congestive heart failure.
The second most common reason for readmission was unresolved limb symptoms, either persistent rest pain or failure of appropriate progression of wound healing in the index limb (13/37 ¼ 33%). Three of these 13 patients were readmitted with graft thrombosis and underwent urgent angiography. Six readmissions were unrelated to the index procedure (Table 2). All readmissions were evenly distributed throughout the 30-day time period following the index discharge. There were 7 (19%) of 37 planned readmissions for staged care of CLI.
Risk Factors for Readmissions There were no significant differences in demographic characteristics, comorbid conditions, length of hospital stay, or
Table 2. Thirty-Day Readmission Details. Number Readmission related to index procedure Infection of surgical incision/index limb Unresolved limb symtoms Unrelated readmission CHF exacerbation/arrhymia Decompensated cirrhosis Nausea/vomitting Hypoglycemia
31 18 13 6 3 1 1 1
discharge functional status between the readmitted and the nonreadmitted groups. Advanced CKD (32% vs 16%, P ¼ .02) and urgent operation (35% vs 17%, P ¼ .02) were significantly
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Table 3. Multivariate Analysis of Risk Factors Associated With 30-Day Readmission. Variable
OR
95% CI
P Value
Male gender DM Advanced CKD (stages IV and V) Urgent operation Nonambulatory status at initial discharge
0.58 0.46 3.14 2.98 2.02
0.26-1.27 0.21-1.05 1.28-7.71 1.27-6.97 0.75-5.44
.17 .07 .01 .01 .16
Abbreviations: CKD, chronic kidney disease; CI, confidence interval; DM, diabetes mellitus; OR, odds ratio.
Table 4. Multivariate Analysis of Risk Factors Associated With 30-day Readmission in Infrainguinal Revascularization Subgroup. Variable
OR
95% CI
P Value
Male gender DM Advanced CKD (stages IV and V) Urgent operation Open (vs endovascular) procedure Nonambulatory status at initial discharge
0.50 0.29 7.53 2.66 0.90 0.87
0.16-1.51 0.09-0.89 2.07-27.4 0.85-8.37 0.31-2.59 0.20-3.75
.22 .03 .002 .09 .84 .85
Abbreviations: CKD, chronic kidney disease; CI, confidence interval; DM, diabetes mellitus; OR, odds ratio.
associated with early readmission (Table 1). These 2 factors, as well as gender, diabetes mellitus, and functional status at discharge were included in a multivariate logistic regression model (all Ps .20 in univariate analysis). In a multivariate logistic regression model, urgent index operation (odds ratio [OR]: 2.98, 95% confidence interval [CI]:1.27-6.97) and advanced CKD (OR: 3.14, 95% CI: 1.28-7.71) remained significantly associated with increased risk of 30-day readmission. Although diabetes mellitus was associated with a lower risk of readmission (OR: 0.46, 95% CI: 0.21-1.05), this was not statistically significant (Table 3). Because this study included multiple different types of procedures to treat lower extremity PAD, we performed a subgroup analysis of those 117 patients who underwent infrainguinal revascularization procedures. There was no significant difference in readmission rates in the endovascular-treated compared to the open-treated groups (P ¼ .65). In a multivariate analysis of risk factors limited to this subgroup of 117 patients, advanced CKD (OR: 7.53, 95% CI: 2.07-27.4) remained significantly associated with increased risk of 30-day readmission (Table 4). Urgent index operation was no longer significantly associated with increased risk of 30-day readmission (P ¼ .09), while presence of diabetes mellitus appeared protective of readmission (OR: 0.29, 95% CI: 0.09-0.89; Table 4).
Discussion This study was conducted as the initial part of our institutional effort to understand risk factors for 30-day readmissions following vascular surgery. Our overall readmission rate following lower extremity interventions was 21%, which is similar
to other published studies.3,7,13-15 A recent series from the Brigham and Women’s Hospital showed a 24% overall readmission rate following lower extremity bypass surgery. The majority of their patients had CLI, which was a significant risk factor for readmission. Other risk factors for readmission in their series were dialysis dependence, congestive heart failure, tissue loss indication, distal inflow source, wound infection, and graft failure.7 In a post hoc analysis of participants in the Project of ExVivo vein graft Engineering via Transfection III (PREVENT III) study, a similar readmission rate of 24% was found. Again, hemodialysis dependence was significantly associated with readmission, as were female gender, current smoking, tissue loss, and in-hospital, graft-related events.3 In our study, patients with end-stage renal disease on hemodialysis were more likely to be readmitted, but this was not statistically significant. This is likely related to the small number of patients in our study, as we found that advanced CKD (stages IV and V) was a significant and independent predictor for readmission. Patients with significantly compromised renal function appear to be a high-risk group for 30-day readmission after lower extremity procedures to treat PAD. This observation is consistent with previous studies identifying CKD as a significant predictor for poor outcomes in patients with CLI.16,17 A series from the University of Pennsylvania evaluating readmissions after vascular surgery procedures found a lower readmission rate (14.6%) following open bypass procedures for CLI.13 In their series, diabetes mellitus was identified as the strongest predictor for readmission. Similar findings of diabetes mellitus on 30-day readmission rates were seen in a large population-based study on patients with PAD who underwent both endovascular and open revascularization.14 The association of diabetes mellitus with poor wound healing, increased infectious complications, and poor outcomes in patients with CLI have been well documented.18,19,20,21,22 In our study, patients with diabetes mellitus were less likely to be readmitted, although this did not reach statistical significance (P ¼ .06 in the multivariable model). We believe that the lower hospital readmission rate in the diabetic patients in our study may have been influenced by the higher degree of outpatient care received by these patients. During the study period, our institution established a multidisciplinary limb preservation team of vascular surgeons, podiatric specialists, and nurse practitioners who provided comprehensive inpatient and outpatient care to many of these patients included in this study. This unique observation of the effects of diabetes mellitus on readmissions may be in part a reflection of closer outpatient follow-up, resulting in a lower readmission rate in patients with diabetic foot wounds. The most common reason for readmission in our study was infection at the surgical incision or involving the index ischemic limb. This finding is consistent with previous reports identifying wound-related problems in the index limb as the primary reason for readmissions.3,7,13,23 While there was a total of 18 readmissions due to infectious reasons, only 3 of these patients had evidence of wound infection during the initial admission. In addition, the median interval from the index discharge to readmission for these patients was 14 days.
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Therefore, we do not believe that prolonging the initial hospital stay in order to monitor for signs of infection would have led to increased detection of infection or decreased 30-day readmission. While one may assume that endovascular procedures carry a lower risk of wound complications and therefore readmission, we observed similar, high rates of 30-day readmission in those treated with infrainguinal endovascular intervention and open infrainguinal bypass surgery. This likely reflects the fact that a large number of patients in our cohort (in both the endovascular and the open surgery groups) presented with CLI. In an analysis of US medical data from 2005 to 2007, Vogel et al showed a 30% readmission rate in patients who underwent tibioperoneal interventions for CLI.24 Percutaneous intervention did not appear to mitigate the ongoing need for longitudinal care through readmissions in our cohort. A similar high readmission rate seen in our amputation subgroup is consistent with a study by Curran et al, using American College of Surgeons National Surgical Quality Improvement Program database.25 While the smaller sample size and the single-institution, retrospective nature of our study are potential limitations, we believe that direct use of our institutional electronic clinical medical records allowed us to capture the relevant data for each readmission with a high level of clinical detail. Smaller studies such as ours may allow a more granular analysis of risk factors than can be achieved using larger population-based or billingderived data. In conclusion, patients undergoing lower extremity interventions to treat PAD experience high 30-day readmission rates. Patients with advanced CKD or those who require urgent operations are at even higher risk of readmission. While we would like to decrease the rate of readmissions, we do not believe that this is necessarily a marker of poor quality care. The high 30-day readmission rate may be reflective of the baseline severity of limb ischemia, procedural complexity, and significant patient comorbidities. Patients with CLI, in particular, often require multiple interventions to achieve successful limb salvage. It is imperative that readmission quality metrics be defined using an evidence-based approach that accounts for risk factors that cannot be altered once the episode of care has been initiated. Preventability should be defined scientifically, not economically.
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Declaration of Conflicting Interests The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
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The author(s) received no financial support for the research, authorship, and/or publication of this article.
References 1. Centers for Medicare & Medicaid Services. (n.d.). Readmissions Reduction Program. Web site. http://www.cms.gov/Medicare/
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Medicare-Fee-for-Service-Payment/AcuteInpatientPPS/Read missions-Reduction-Program.html. Jenks SF, William MV, Coleman EA. Rehospitalizations among patients in the medicare fee-for-service program. N Engl J Med. 2009;360(14):1418-1428. McPhee JT, Nguyen LL, Ho KJ, Ozaki CK, Conte MS, Belkin M. Risk prediction of 30-day readmission after infrainguinal bypass for critical limb ischemia. J Vasc Surg. 2013;57(6):1481-1488. Tsai TC, Joynt KE, Orav J, et al. Variation in surgicalreadmission rates and quality of hospital care. N Engl J Med. 2013;369(12):1134-1421. Hechenbleikner EM, Makary MA, Samarov D, et al. Hospital readmission by method of data collection. J Am Coll Surg. 2013;216(6):1150-1158. Sellers MM, Merkow RP, Halverson A, et al. Validation of new readmission data in the American college of surgeons national surgial quality improvement program. J Am Coll Surg. 2013; 216(3):420-427. McPhee JT, Barshes NR, Ho KJ, et al. Predictive factors of 30-day unplanned readmission after lower extremity bypass. J Vasc Surg. 2013;57(4):955-962. Wiseman JT, Guzman AM, Fernandes-Taylor S, Egelbert TL, Saunders RS, Kent KC. General and vascular surgery readmission: a systematic review. J Am Coll Surg. 2014;219(3): 552-569. Gupta PK, Fernandes-Taylor S, Ramanan B, Engelbert TL, Kent KC. Unplanned readmission after vascular surgery. J Vasc Surg. 2014;59(2):473-482. Engelbert TL, Fernandes-Taylor S, Gupta PK, Kent KC, Matsumura J. Clinical characteristics associated with readmission among patients undergoing vascular surgery. J Vasc Surg. 2014;59(5):1349-1355. Zhang JQ, Curran T, McCallum JC, Wang L, Wyers MC, Hamdan AD. Risk factors for readmissions after lower extremity bypass in the american college of surgeons national surgery quality improvement program. J Vasc Surg. 2014;59(5): 1331-1339. Brooke BS, DeMarino RR, Girotti M, Dimick JB, Goodney PP. Developing strategies for predicting and preventing readmissions in vascular surgery. J Vasc Surg. 2012;56(2):556-562. Jackson BM, Doctor L, Wang GJ, Woo EY. Low rehospitalization rate for vascular surgery patients. J Vasc Surg. 2011; 54(3):767-772. Vogel TR, Kruse RL. Risk factors for readmission after lower extremity procedures for peripheral artery disease. J Vasc Surg. 2013;58(1):90-97. Goodney PP, Stukel TA, Lucas FL, Finlayson EV, Birkmeyer JD. Hospital volume, length of stay and readmission rates in high-risk surgery. Ann Surg. 2003;238(2):161-167. Simons JP, Goodney PP, Nolan BW, Cronenwett JL, Messina LM, Schanzer A. Failure to achieve clinical improvement despite graft patency in patients undergoing infrainguinal lower extremity bypass for critical limb ischemia. J Vasc Surg. 2010;51(6): 1419-1424. Schanzer A, Goodney PP, Li Y, et al. Validation of the PIII CLI risk score for the prediction of amputation-free survival
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Vascular and Endovascular Surgery 49(3-4) in patients undergoing infrainguinal autogenous vein bypass for critical limb ischemia. J Vasc Surg. 2009;50(4):769-775. Gibbons GW, Shaw PM. Diabetic vascular disease: characteristics of vascular disease unique to the diabetic patients. Semin Vasc Surg. 2012;25(2):89-92. Conte MS. Diabetic revascularization: endovascular versus open bypass–do we have the answer? Semin Vasc Surg. 2012;25(2): 108-114. Dosluoglu HH, Lall P, Nader ND, Harris LM, Dyjsk ML. Insulin use is associated with poor limb salvage and survival in diabetic patients with chronic limb ischemia. J Vasc Surg. 2010;51(5): 1178-1189. Goodney PP, Nolan BW, Schanzer A, et al. Factors associated with death 1 year after lower extremity bypass in Northern New England. J Vasc Surg. 2010;51(1):71-79.
22. Meltzer AJ, Evangelisti G, Graham AR, et al. Determinants of outcome after endovascular therapy for critical limb ischemia with tissue loss. Ann Vasc Surg. 2014;28(1):144-151. 23. Davenport DL, Zwischenberger BA, Xenos ES. Analysis of 30-day readmission after aortoiliac and infrainguinal revascularization using the American college of surgeons national surgical quality improvement program data set. J Vasc Surg. 2014;60(5):1266-1274. 24. Vogel TR, Dombrovsky VY, Carson JL, Graham AM. In-hospital and 30-day outcomes after tibioperoneal interventions in the us medicare population with critical limb ischemia. J Vasc Surg. 2011;54(1):109-115. 25. Curran T, Zhang JQ, Lo RC, et al. Risk Factors and indications for readmission after lower extremity amputation in the American college of surgeons national quality improvement program. 2014;60(5):1315-1324.
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Risk Factors for 30-Day Hospital Readmission in Patients Undergoing Treatment for Peripheral Artery Disease
Vascular and Endovascular Surgery 2015, Vol. 49(3-4) 69-74 ª The Author(s) 2015 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/1538574415593498 ves.sagepub.com
Sukgu M. Han, MD1, Bian Wu, MD1, Charles M. Eichler, MD1, Linda M. Reilly, MD1, Shant M. Vartanian, MD1, Michael S. Conte, MD1, and Jade Hiramoto, MD1
Abstract Early hospital readmission among vascular surgery patients is a focus of Medicare’s new reimbursement structure. We aim to identify factors associated with 30-day readmission after lower extremity interventions to treat peripheral artery disease (PAD). Retrospective analysis of 174 consecutive patients discharged from the vascular surgery service between January 1, 2011, and July 31, 2012, after procedures for lower extremity PAD was performed. Of 174 patients, 37 were readmitted within 30 days of discharge. There were no significant differences in baseline characteristics between the readmitted and the nonreadmitted groups. In a multivariate logistic regression model, urgent operation and advanced chronic kidney disease (CKD) were associated with increased risk of 30-day readmission. The most common reasons for readmission were infection of the surgical site or index limb (18 of 37), followed by unresolved limb symptoms (13 of 37). The 30-day readmission is frequent after lower extremity interventions to treat PAD. Urgent operative intervention and advanced CKD appear to be risk factors for early hospital readmission. Keywords peripheral vascular disease, critical limb ischemia, readmission
Introduction In accordance with the Patient Protection and Affordable Care Act of 2010, the Center for Medicare and Medicaid Services has proposed policy changes restructuring reimbursement in an effort to reduce costs associated with hospital readmissions. In addition, risk-adjusted rates of 30-day hospital readmissions will be publicly reported in the near future.1 According to national Medicare claims data from 2003 to 2004, vascular surgical patients have high rates of hospital readmissions, second only to patients with congestive heart failure.2 However, available data on hospital readmissions following vascular surgical procedures are limited, and those derived from heterogeneous administrative databases may lack an appropriate level of detail to delineate the clinical risk factors associated with these readmissions.1-11 Although readmission rates after vascular surgical procedures vary widely, peripheral vascular procedures, especially those for critical limb ischemia (CLI), have been associated with a 30-day readmission rate greater than 20%.8-10,12 It is difficult to determine an ‘‘acceptable’’ rate of unplanned readmission after vascular surgical procedures, given that types of procedures and patient populations vary between different studies. In addition, patients with CLI may undergo staged procedures that necessitate return to the hospital within 30 days.
Institutional studies have identified dialysis dependence, congestive heart failure, and tissue loss as risk factors for readmission after lower extremity bypass procedures.3 In the future, hospitals with higher than expected readmission rates will be penalized financially.1 However, benchmark hospital readmission rates after vascular surgery procedures have not been established nor has a risk-adjusted model been developed. The purpose of our study was to determine the 30-day hospital readmission rate after lower extremity interventions to treat peripheral artery disease (PAD) and to identify risk factors associated with early readmission.
Methods This was a retrospective review of a prospective cohort of 174 patients who were discharged following interventions for lower extremity PAD at the University of California San Francisco, 1
Division of Vascular and Endovascular Surgery, Department of Surgery, University of California San Francisco, San Francisco, CA, USA Corresponding Author: Sukgu M. Han, University of California San Francisco, 400 Parnassus Ave, Room A-581, San Francisco, CA 94143, USA. Email: [email protected]
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from January 2011 to July 2012. These interventions included endovascular and open revascularizations as well as major and minor amputations. Patients who died during the hospitalization were excluded from the analysis. Patients who underwent revascularization for vascular trauma or adjunct endovascular procedures for previously placed aortic stent grafts were also excluded. The primary outcome variable was 30-day readmission to the hospital from the initial discharge, following the index procedure. For patients who underwent more than 1 procedure during the study interval, only the initial index procedure and hospitalization were included; hence, no patient was included more than once in this study. In cases where a patient had multiple 30-day readmissions during the study period, only the initial readmission was included in order to accurately characterize patient-related factors. We categorized the readmission types as related or unrelated to the index vascular procedure and planned or unplanned.12 To further validate the relationship with the index procedure, we identified the readmission diagnosis and admitting service. Planned readmissions included any admissions associated with elective procedures that were designed as part of multistaged procedures, those scheduled at the time of discharge, and those electively scheduled during outpatient clinic visits. Baseline patient characteristics included in this study were extracted from the electronic medical record and included age, gender, and race. Medical comorbidities included a history of diabetes, hypertension, coronary artery disease, congestive heart failure, arrhythmias, cerebrovascular accident, chronic obstructive pulmonary disease, chronic kidney disease (CKD), and dialysis dependence. Glomerular filtration rates (GFRs) were calculated using Modification of Diet in Renal Disease protocol. Advanced CKD was defined as stage IV (GFR < 30 mL/min/1.73 m2) or stage V (hemodialysis dependence). The lowest GFR within 3 months prior to the index procedure was used in the analysis. Smoking history was dichotomized to nonsmokers and current/prior smokers. Limb ischemia was recorded as acute or chronic, and the degree of ischemia (claudication, rest pain, tissue loss, or gangrene) was noted. An urgent operation was defined as a procedure performed within 24 hours of an unscheduled admission. Functional status was categorized as ambulatory, wheelchair dependent, or bed bound. Discharge destination was recorded as home, rehabilitation center/skilled nursing facility, or transfer to an inpatient hospital. Statistical analyses were performed using STATA 12 software (StataCorp LP, College Station, Texas). Proportions between groups were compared using the chi-square or Fisher exact tests, and continuous variables between groups were compared using the Student t test. Multivariable predictors of 30-day hospital readmission were analyzed by a logistic regression model. A P value .20 was used as the threshold for inclusion in the multivariate regression model.
Results Patient Characteristics Of the 174 consecutive patients discharged after lower extremity vascular surgical procedures, 37 (21%) were readmitted within
30 days of the initial discharge. The mean age was 69 + 11.5 years, 65% were male, and 66% were Caucasian. The mean length of hospital stay following the index procedure was 7.6 days, and 21% underwent an urgent operation (Table 1).
Procedures Performed During Index Hospitalization Forty-six patients underwent percutaneous endoluminal intervention to treat occlusive disease of the iliac, femoral, popliteal, and tibial arteries. Eighteen patients underwent angioplasty alone, while 17 patients underwent infrainguinal stent placement and 2 patients received iliac stents. Nine patients had thrombolysis of occluded stents or bypass grafts. All patients with thrombolysis were taken back to the operating department within 24 hours for repeat angiography, where angioplasty was performed in 7 and stenting in 1. Ninety-one (57%) patients underwent open revascularization procedures to treat lower extremity PAD. Eighteen of these patients underwent open bypass for aortoiliac occlusive disease, while 73 patients had open infrainguinal revascularization. An additional 13 patients underwent combined open and endovascular revascularization (iliac stents were combined with various open reconstructions in 8 patients, and 5 patients had femoral endarterectomy with distal superficial femoral artery (SFA) angioplasty or stents). Foot debridement with or without minor amputations below the ankle were performed in 20 patients. Three patients received primary below-knee amputations, while 1 patient had an above-knee amputation. There were a total of 36 (21%) urgent procedures performed. Fourteen of these patients presented with acute limb ischemia, while 10 had wet gangrene requiring emergent debridement, 10 had threatened bypass grafts, 1 had a bypass graft infection, and 1 had an anastomotic pseudoaneurysm.
Degree of Ischemia On initial presentation, signs of critical limb ischemia were present in 112 (64%) patients. Thirty-six of these patients had rest pain, while 76 had tissue loss. An additional 14 patients presented with signs of acute limb ischemia, all of which required urgent procedures. Thirty-nine patients presented with claudication. Five patients had asymptomatic stenosis of a previous bypass graft detected by surveillance duplex ultrasound. Four patients had infection of a previous bypass graft.
Description of Readmissions Of 37 readmissions, 31 were related to the index procedure (Table 2). Infection either at the surgical site or involving the index limb was the most frequent reason for readmission (18/ 37 ¼ 49%). The groin incision was the site of infection in 6 of these 18 patients. Twelve patients had infection involving the leg incisions or amputation site. Only 3 of these patients had their surgical site infection diagnosed during the index admission. Eleven of these 18 patients readmitted with infection underwent surgical debridement, while 7 were managed with intravenous antibiotics. Only 3 of these 18 patients were claudicants at initial presentation, and the remainder presented with CLI.
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Table 1. Patient Characteristics.
Number Age Male gender Race White Black Hispanic Asian Others DM Hypertension CAD CHF Hyperlipidemia Stroke Advanced CKD (stage IV or V) COPD Smoking VTE Atrial fibrillation Length of stay, days Urgent operation Re-do operation Functional status at discharge Ambulatory Wheelchair bound Bedbound Operation performed Aortoiliac revascularization Open infrainguinal revascularizationbypass Percutaneous endoluminal revascularization Major amputation Hybrid BPG þ angio Debridement þ minor amputation Discharge destination Home Home health Skilled nursing facility Acute care at outside hospital AMA
Total
Nonreadmitted
Readmitted
174 69.0 + 11.5 111 (64%)
137 68.8 + 11.4 66%
37 68.7 + 11.4 54%
116 17 17 15 9 82 146 67 20 95 23 34 31 113 10 19 7.6 36 17
93 12 15 9 8 68 113 53 16 77 19 22 24 92 8 14 7.68 23 13
23 5 2 6 1 14 33 14 4 18 4 12 7 21 2 5 7.65 13 4
(66%) (10%) (10%) (9%) (5%) (47%) (84%) (39%) (12%) (55%) (13%) (19%) (18%) (65%) (6%) (11%) + 5.1 (21%) (10%)
147 (85%) 19 (11%) 8 (5%)
(67%) (9%) (11%) (7%) (6%) (50%) (82%) (39%) (12%) (56%) (14%) (16%) (17%) (67%) (6%) (10%) (17%) (9%)
119 (86%) 14 (10%) 4 (3%)
(62%) (14%) (5%) (16%) (3%) (38%) (89%) (37%) (11%) (49%) (11%) (33%) (19%) (57%) (5%) (14%) (35%) (11%)
P Value .87 .15 .25
.20 .33 .86 .8 .39 .64 .02 .83 .23 .93 .65 .7 .02 .81 .08
28 (76%) 5 (13%) 4 (11%) .32
18 73 46 4 13 20
(11%) (42%) (26%) (2.%) (8%) (11%)
16 59 36 2 11 13
(12%) (43%) (26%) (1.5%) (8%) (9%)
2 14 10 2 2 7
(5.4%) (38%) (27%) (5.4%) (5.4%) (19%)
93 34 36 7 4
(53%) (20%) (21%) (4%) (2.3%)
77 23 27 7 3
(56%) (17%) (20%) (5%) (2.2%)
16 11 9 0 1
(43%) (30%) (24%)
.23
(2.7%)
Abbreviations: CKD, chronic kidney disease; COPD, chronic obstructive pulmonary disease; DM, diabetes mellitus; VTE, venous thromboembolism; AMA, against medical advice; BPG, bypass graft; CAD, coronary artery disease; CHF, congestive heart failure.
The second most common reason for readmission was unresolved limb symptoms, either persistent rest pain or failure of appropriate progression of wound healing in the index limb (13/37 ¼ 33%). Three of these 13 patients were readmitted with graft thrombosis and underwent urgent angiography. Six readmissions were unrelated to the index procedure (Table 2). All readmissions were evenly distributed throughout the 30-day time period following the index discharge. There were 7 (19%) of 37 planned readmissions for staged care of CLI.
Risk Factors for Readmissions There were no significant differences in demographic characteristics, comorbid conditions, length of hospital stay, or
Table 2. Thirty-Day Readmission Details. Number Readmission related to index procedure Infection of surgical incision/index limb Unresolved limb symtoms Unrelated readmission CHF exacerbation/arrhymia Decompensated cirrhosis Nausea/vomitting Hypoglycemia
31 18 13 6 3 1 1 1
discharge functional status between the readmitted and the nonreadmitted groups. Advanced CKD (32% vs 16%, P ¼ .02) and urgent operation (35% vs 17%, P ¼ .02) were significantly
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Vascular and Endovascular Surgery 49(3-4)
Table 3. Multivariate Analysis of Risk Factors Associated With 30-Day Readmission. Variable
OR
95% CI
P Value
Male gender DM Advanced CKD (stages IV and V) Urgent operation Nonambulatory status at initial discharge
0.58 0.46 3.14 2.98 2.02
0.26-1.27 0.21-1.05 1.28-7.71 1.27-6.97 0.75-5.44
.17 .07 .01 .01 .16
Abbreviations: CKD, chronic kidney disease; CI, confidence interval; DM, diabetes mellitus; OR, odds ratio.
Table 4. Multivariate Analysis of Risk Factors Associated With 30-day Readmission in Infrainguinal Revascularization Subgroup. Variable
OR
95% CI
P Value
Male gender DM Advanced CKD (stages IV and V) Urgent operation Open (vs endovascular) procedure Nonambulatory status at initial discharge
0.50 0.29 7.53 2.66 0.90 0.87
0.16-1.51 0.09-0.89 2.07-27.4 0.85-8.37 0.31-2.59 0.20-3.75
.22 .03 .002 .09 .84 .85
Abbreviations: CKD, chronic kidney disease; CI, confidence interval; DM, diabetes mellitus; OR, odds ratio.
associated with early readmission (Table 1). These 2 factors, as well as gender, diabetes mellitus, and functional status at discharge were included in a multivariate logistic regression model (all Ps .20 in univariate analysis). In a multivariate logistic regression model, urgent index operation (odds ratio [OR]: 2.98, 95% confidence interval [CI]:1.27-6.97) and advanced CKD (OR: 3.14, 95% CI: 1.28-7.71) remained significantly associated with increased risk of 30-day readmission. Although diabetes mellitus was associated with a lower risk of readmission (OR: 0.46, 95% CI: 0.21-1.05), this was not statistically significant (Table 3). Because this study included multiple different types of procedures to treat lower extremity PAD, we performed a subgroup analysis of those 117 patients who underwent infrainguinal revascularization procedures. There was no significant difference in readmission rates in the endovascular-treated compared to the open-treated groups (P ¼ .65). In a multivariate analysis of risk factors limited to this subgroup of 117 patients, advanced CKD (OR: 7.53, 95% CI: 2.07-27.4) remained significantly associated with increased risk of 30-day readmission (Table 4). Urgent index operation was no longer significantly associated with increased risk of 30-day readmission (P ¼ .09), while presence of diabetes mellitus appeared protective of readmission (OR: 0.29, 95% CI: 0.09-0.89; Table 4).
Discussion This study was conducted as the initial part of our institutional effort to understand risk factors for 30-day readmissions following vascular surgery. Our overall readmission rate following lower extremity interventions was 21%, which is similar
to other published studies.3,7,13-15 A recent series from the Brigham and Women’s Hospital showed a 24% overall readmission rate following lower extremity bypass surgery. The majority of their patients had CLI, which was a significant risk factor for readmission. Other risk factors for readmission in their series were dialysis dependence, congestive heart failure, tissue loss indication, distal inflow source, wound infection, and graft failure.7 In a post hoc analysis of participants in the Project of ExVivo vein graft Engineering via Transfection III (PREVENT III) study, a similar readmission rate of 24% was found. Again, hemodialysis dependence was significantly associated with readmission, as were female gender, current smoking, tissue loss, and in-hospital, graft-related events.3 In our study, patients with end-stage renal disease on hemodialysis were more likely to be readmitted, but this was not statistically significant. This is likely related to the small number of patients in our study, as we found that advanced CKD (stages IV and V) was a significant and independent predictor for readmission. Patients with significantly compromised renal function appear to be a high-risk group for 30-day readmission after lower extremity procedures to treat PAD. This observation is consistent with previous studies identifying CKD as a significant predictor for poor outcomes in patients with CLI.16,17 A series from the University of Pennsylvania evaluating readmissions after vascular surgery procedures found a lower readmission rate (14.6%) following open bypass procedures for CLI.13 In their series, diabetes mellitus was identified as the strongest predictor for readmission. Similar findings of diabetes mellitus on 30-day readmission rates were seen in a large population-based study on patients with PAD who underwent both endovascular and open revascularization.14 The association of diabetes mellitus with poor wound healing, increased infectious complications, and poor outcomes in patients with CLI have been well documented.18,19,20,21,22 In our study, patients with diabetes mellitus were less likely to be readmitted, although this did not reach statistical significance (P ¼ .06 in the multivariable model). We believe that the lower hospital readmission rate in the diabetic patients in our study may have been influenced by the higher degree of outpatient care received by these patients. During the study period, our institution established a multidisciplinary limb preservation team of vascular surgeons, podiatric specialists, and nurse practitioners who provided comprehensive inpatient and outpatient care to many of these patients included in this study. This unique observation of the effects of diabetes mellitus on readmissions may be in part a reflection of closer outpatient follow-up, resulting in a lower readmission rate in patients with diabetic foot wounds. The most common reason for readmission in our study was infection at the surgical incision or involving the index ischemic limb. This finding is consistent with previous reports identifying wound-related problems in the index limb as the primary reason for readmissions.3,7,13,23 While there was a total of 18 readmissions due to infectious reasons, only 3 of these patients had evidence of wound infection during the initial admission. In addition, the median interval from the index discharge to readmission for these patients was 14 days.
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Therefore, we do not believe that prolonging the initial hospital stay in order to monitor for signs of infection would have led to increased detection of infection or decreased 30-day readmission. While one may assume that endovascular procedures carry a lower risk of wound complications and therefore readmission, we observed similar, high rates of 30-day readmission in those treated with infrainguinal endovascular intervention and open infrainguinal bypass surgery. This likely reflects the fact that a large number of patients in our cohort (in both the endovascular and the open surgery groups) presented with CLI. In an analysis of US medical data from 2005 to 2007, Vogel et al showed a 30% readmission rate in patients who underwent tibioperoneal interventions for CLI.24 Percutaneous intervention did not appear to mitigate the ongoing need for longitudinal care through readmissions in our cohort. A similar high readmission rate seen in our amputation subgroup is consistent with a study by Curran et al, using American College of Surgeons National Surgical Quality Improvement Program database.25 While the smaller sample size and the single-institution, retrospective nature of our study are potential limitations, we believe that direct use of our institutional electronic clinical medical records allowed us to capture the relevant data for each readmission with a high level of clinical detail. Smaller studies such as ours may allow a more granular analysis of risk factors than can be achieved using larger population-based or billingderived data. In conclusion, patients undergoing lower extremity interventions to treat PAD experience high 30-day readmission rates. Patients with advanced CKD or those who require urgent operations are at even higher risk of readmission. While we would like to decrease the rate of readmissions, we do not believe that this is necessarily a marker of poor quality care. The high 30-day readmission rate may be reflective of the baseline severity of limb ischemia, procedural complexity, and significant patient comorbidities. Patients with CLI, in particular, often require multiple interventions to achieve successful limb salvage. It is imperative that readmission quality metrics be defined using an evidence-based approach that accounts for risk factors that cannot be altered once the episode of care has been initiated. Preventability should be defined scientifically, not economically.
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Declaration of Conflicting Interests The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
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The author(s) received no financial support for the research, authorship, and/or publication of this article.
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