Cost of treating advanced leg ischemia. Bypass graft vs primary amputation

The Role of Lower Extremity Amputation in Chronic Limb-Threatening Ischemia

Chronic limb-threatening ischemia (CLTI) is a severe form of peripheral artery disease associated with high rates of limb loss. The primary goal of treatment in CLTI is limb salvage via revascularization. Multidisciplinary teams provide improved care for those with CLTI and lead to improved limb salvage rates. Not all patients are candidates for revascularization, and a subset will require major amputation. This article highlights the role of amputations in the management of CLTI, and describes the patients who should be offered primary amputation.

The economic burden of inpatient diabetic foot ulcers in Toronto, Canada

OBJECTIVE

Diabetic foot ulcer, which often leads to lower limb amputation, is a devastating complication of diabetes that is a major burden on patients and the healthcare system. The main objective of this study is to determine the economic burden of diabetic foot ulcer-related care.

METHODS

We conducted a multicenter study of all diabetic foot ulcer patients admitted to general internal medicine wards at seven hospitals in the Greater Toronto Area, Canada from 2010 to 2015, using the GEMINI database. We compared the mean costs of care per patient for diabetic foot ulcer-related admissions, admissions for other diabetes-related complications, and admissions for the top five most costly general internal medicine conditions, using the Ontario Case Costing Initiative. Regression models were used to determine adjusted estimates of cost per patient. Propensity-score matched analyses were performed as sensitivity analyses.

RESULTS

Our study cohort comprised of 557 diabetic foot ulcer patients; 2939 non-diabetic foot ulcer diabetes patients; and 23,656 patients with the top 5 most costly general internal medicine conditions. Diabetic foot ulcer admissions incurred the highest mean cost per patient ($22,754) when compared to admissions with non-diabetic foot ulcer diabetes ($8,350) and the top five most costly conditions ($10,169). Using adjusted linear regression, diabetic foot ulcer admissions demonstrated a 49.6% greater mean cost of care than non-diabetic foot ulcer-related diabetes admissions (95% CI 1.14-1.58), and a 25.6% greater mean cost than the top five most costly conditions (95% CI 1.17-1.34). Propensity-scored matched analyses confirmed these results.

CONCLUSION

Diabetic foot ulcer patients incur significantly higher costs of care when compared to admissions with non-diabetic foot ulcer-related diabetes patients, and the top five most costly general internal medicine conditions.

[Does an attempt to save a limb always prolong the patient's life?]

AIM

The purpose of the study was to examine overall survival and the incidence of major adverse cardiovascular events, as well as economic expenditures for treatment of patients with occlusion of the femoropopliteal-tibial segment and critical ischaemia in low competence of the outflow channel, with a poor prognosis for endovascular or open revascularization of lower-limb arteries.

PATIENTS AND METHODS

We studied the results of treating a total of 68 patients with lower-limb critical ischaemia and low parameters of the outflow channel competence. Primary arterial reconstruction was performed in 48 cases. At various terms after revascularization due to thrombosis of the reconstruction zone and the development of gangrene, amputation of the lower limb was performed: at 3 to 11 (n=25) and at 12 to 24 (n=25) months. Primary amputation of the lower limb was performed in 20 patients. The endpoints of the study included overall survival, the incidence of major adverse cardiovascular events, and economic expenditures for the in-hospital treatment. The average duration of follow-up amounted to 2 years.

RESULTS

The obtained findings demonstrated that in patients with lower-limb critical ischaemia and low parameters of the outflow channel competence, redo arterial reconstructions and amputation within 11 months, as well as a high level of surgical risk were associated with a low overall survival rate and the development of major adverse cardiovascular events in the remote period. Secondary surgical interventions on the major vessels significantly increased the cost of treatment.

The Majority of Patients Have Diagnostic Evaluation Prior to Major Lower Extremity Amputation

BACKGROUND

Critical limb ischemia (CLI) patients who do not undergo revascularization are at great risk for major lower extremity (LE) amputation. It has been reported that less than half (49%) of a reference Medicare amputation population had any diagnostic vascular evaluation prior to a major LE amputation. We were surprised by these data so we reviewed the preoperative evaluation in all patients who had a major LE amputation. We propose that significantly more patients will have a vascular evaluation prior to major LE amputation at a tertiary care referral center when a vascular surgeon does the amputation.

METHODS

A retrospective analysis of major LE amputations was performed. Patient demographics, comorbidities, type of amputation, reason for amputation, Rutherford classification, and type of preoperative vascular examination were evaluated.

RESULTS

Over 4 years, 281 patients required major LE amputation. Above-knee amputation was performed in 39.1% of patients, whereas below-knee amputation was performed in 60.9%. Amputation was performed due to CLI in 92.9% of patients, whereas 7.1% of amputations were performed due to diabetes or other reasons. Preoperative vascular evaluation was performed in 100% of patients undergoing major LE amputation. Vascular surgeon pulse examination was most common (99.3%) followed by pulse volume recordings/ankle-brachial index (78.8%), angiography (54.8%), computed tomography angiography (29.3%), duplex ultrasonography (41.3%), and magnetic resonance angiography (0.4%). Amputations most commonly occurred due to Rutherford classification VI (63.3%) with 97.2% of patients having Rutherford IV-VI classification.

CONCLUSIONS

Preoperative vascular evaluation prior to major LE amputation is achievable in the majority of patients, reported here in 100% of patients undergoing a major LE amputation. This allows us to evaluate the patient for revascularization options prior to amputation for possible limb salvage.

Popliteo-pedal bypass surgery for critical limb ischemia

BACKGROUND

Critical limb ischaemia due to distal arterial disease represents a significant challenge. Randomised controlled evidence suggests that open surgery may be superior to endovascular intervention but there is limited data on the specific clinical cohort with exclusively infra-popliteal disease.

AIM

We analysed indications for, and outcome from all, popliteo-pedal bypass procedures performed between July 1998 to November 2008.

PATIENTS AND METHODS

Twenty-eight bypass procedures were performed in 24 patients. Autologous vein was used exclusively. The proximal anastomosis was to the below-knee popliteal artery in all the patients; the distal anastomosis was to plantar artery (n = 15) or dorsalis pedis artery (n = 13). Mean patient age was 63.Eight years of age (range 37-92 years). Indications for surgery were tissue loss (n = 21) and rest pain (n = 7). Ultrasound graft surveillance was performed every 6-months.

RESULTS

Using life table analysis, primary graft patency was 63.3% at 1-, 3- and 5-years and secondary patency (after three interventions) was 74.6% at 1-, 3- and 5-years. Limb salvage rate was 81.8% after 1-, 3- and 5-years as all five limb amputations were performed in the first 3-months following the surgery. Overall survival was 75, 75 and 47.1% at 1-, 3- and 5-years, respectively. The major amputation free survival rate was 54.2, 54.2 and 21.3% at 1-, 3- and 5-years, respectively. Seventy-nine percent (n = 19) patients were diabetic.

CONCLUSION

Our data supports popliteo-pedal bypass as an effective treatment for distal vascular disease. Comparison with endovascular treatment in a randomised trial needs to be performed.

Are femorodistal bypass grafts for acute limb ischemia worthwhile?

Background: It has been shown that autogenous veins are associated with the best limb salvage rates for femorodistal bypass surgery. However, in emergency settings, when an autogenous vein is unavailable, use of synthetic graft material or amputation is a critical decision to make. Objective: To assess the appropriateness of femorodistal bypass grafts for acute limb ischemia in emergency settings. Methods: Patients who underwent emergent bypass and elective femorodistal bypass surgery between 1996 and 2006 were reviewed retrospectively in a single center. Results: There were 147 patients of which 84 had elective and 63 had emergent bypass. The graft patency rates for elective admissions were 44 and 25% vs. 25 and 23% for admissions for acute femorodistal graft surgery at 2 and 4 years, respectively (p < 0.004). Admissions for acute ischemia who were treated with prosthetic grafts had a primary patency of 24 vs. 27% for vein grafts at 2 years and 24 vs. 23% at 4 years (p = 0.33). In the acute femorodistal grafts group, primary patency at 2 years for vein and prosthetic grafts was 27 and 24% as compared to 42 and 32% for electives. These values for cumulative limb salvage rates for elective bypasses were 73 and 63% as compared to 52% at both time points in the acute femorodistal graft group (p < 0.004). In emergency settings, the limb salvage rate for acute femorodistal bypass with prosthetic grafts was 38%, and for vein grafts it was 62% at both time points (p = 0.08). Conclusion: The long term limb salvage rate of 38% suggests that emergent femorodistal revascularization is worthwhile.

Health-care costs associated with amputation or reconstruction of a limb-threatening injury

BACKGROUND

Recent reports have suggested that functional outcomes are similar following either amputation or reconstruction of a severely injured lower extremity. The goal of this study was to compare two-year direct health-care costs and projected lifetime health-care costs associated with these two treatment pathways.

METHODS

Two-year health-care costs were estimated for 545 patients with a unilateral limb-threatening lower-extremity injury treated at one of eight level-I trauma centers. Included in the calculation were costs related to (1) the initial hospitalization, (2) all rehospitalizations for acute care related to the limb injury, (3) inpatient rehabilitation, (4) outpatient doctor visits, (5) outpatient physical and occupational therapy, and (6) purchase and maintenance of prosthetic devices. All dollar figures were inflated to constant 2002 dollars with use of the medical service Consumer Price Index. To estimate projected lifetime costs, the number of expected life years was multiplied by an estimate of future annual health-care costs and added to an estimate of future costs associated with the purchase and maintenance of prosthetic devices.

RESULTS

When costs associated with rehospitalizations and post-acute care were added to the cost of the initial hospitalization, the two-year costs for reconstruction and amputation were similar. When prosthesis-related costs were added, there was a substantial difference between the two groups ($81,316 for patients treated with reconstruction and $91,106 for patients treated with amputation). The projected lifetime health-care cost for the patients who had undergone amputation was three times higher than that for those treated with reconstruction ($509,275 and $163,282, respectively).

CONCLUSIONS

These estimates add support to previous conclusions that efforts to improve the rate of successful reconstructions have merit. Not only is reconstruction a reasonable goal at an experienced level-I trauma center, it results in lower lifetime costs.

Process of care and outcomes in patients with peripheral arterial disease

BACKGROUND

We investigated the association of process of care measures with adverse limb and systemic events in patients with peripheral arterial disease (PAD).

METHODS

We conducted a retrospective cohort study of patients with PAD, as defined by an ankle-brachial index (ABI) <0.9. The index date was defined as the date, during 1995 to 1998, when the patient was seen in the Michael E. DeBakey VA Medical Center noninvasive vascular laboratory and found to have PAD. We conducted a chart review for process of care variables starting 3 years before the index date and ending at the time of the first event or the final visit (December 31, 2001), whichever occurred first. We examined the association between PAD process of care measures, including risk factor control, and prescribing of medication, with time of the patient's first major limb event or death.

RESULTS

Of the 796 patients (mean age, 65 +/- 9.9 years), 230 (28.9% experienced an adverse limb event (136 lower-extremity bypass, 94 lower-extremity amputation), and 354 (44.5%) died. Of the patients who died, 247 died without a preceding limb event. Glucose control was protective against death or a limb event with a hazard ratio (HR) of 0.74 (95% confidence limits [CL] 0.60, 0.91, P = 0.004). African Americans were at 2.8 (95% CL 1.7, 4.5) times the risk of Whites or Hispanics for an adverse limb event. However, this risk was no longer significant if their glucose was controlled. For process measures, the dispensing of PAD specific medication (HR 1.4, 95% CL 1.1, 1.7) was associated an increased risk for an adverse outcome.

CONCLUSIONS

Our data suggest that glucose control is key to reducing the risk for adverse outcomes, particularly limb events in African Americans. Certain process of care measures, as markers of disease severity and disease management, are associated with poor outcomes in patients with PAD. Further work is needed to determine the role of early disease intervention to reduce poor outcomes in patients with PAD.

Influence of secondary infection on amputation in chronic critical limb ischemia

OBJECTIVES

To evaluate the influence of secondary infection on major amputation in chronic critical leg ischemia (CLI).

DESIGN

Prospective, controlled observational study.

MATERIALS AND METHODS

Sixty-seven patients with CLI and ischemic lesions participated in the study. Presence of infection was defined by clinical, laboratory and radiological criteria. Patients were categorized as having no local infection, soft tissue infection or osteomyelitis treated without antibiotics, amoxicillin/clavulanacid for 1 month or ciprofloxacin and clindamycin for 3 months, respectively. Clinical outcome was assessed at 2, 6 and 12 months. Study endpoints were major amputation and mortality. Analyses were performed using the Kaplan-Meier method.

RESULTS

Forty-seven of 67 patients had a local infection. Major amputation was lower in patients with successful revascularization as compared to patients unsuitable for or with failed (without) revascularization (0% vs 26%, p<0.01). In patients with successful revascularization the probability of complete healing was lower with secondary infection (23% vs 71%, p=0.03). In patients without revascularization complete healing was rare (<10%), but secondary infection did not influenced major amputation, mortality or serious adverse events.

CONCLUSION

Secondary infection reduces the likelihood of successful healing following revascularisation of CLI.

The economic burden of diabetic foot and ankle disorders

Physicians specializing in the care of patients with lower extremity disorders are acutely aware of the many adverse effects of diabetes mellitus and its secondary complications on all body systems. However, the disease has a devastating socioeconomic impact, as well. An estimated $98 billion in direct and indirect medical costs was spent on diabetes in 1997 in the United States. With a growing older population, cases of diabetes mellitus will certainly increase. The economic impact and clinical effectiveness of patient evaluation, preventive strategies, and treatment options are discussed.

Process of care and outcomes in peripheral arterial disease

Peripheral arterial disease (PAD) is a prevalent illness that most commonly affects patients older than 60 years. As the population ages, the prevalence of PAD and its associated adverse outcomes will also increase. Adverse outcomes in PAD are either systemic (ie, cardiovascular events such as myocardial infarctions or strokes) or localized to the legs (ie, bypass surgery or amputation). Although much research has focused on adverse systemic outcomes in patients with PAD, less is known about those factors related to adverse limb events. The Centers for Disease Control and Prevention estimate that more than 100,000 amputations are performed in the United States each year. What remains to be determined is the association between how physicians manage patients with PAD (ie, process of care) and the development of adverse limb outcomes. Determining the association of the management of PAD with adverse limb outcomes will highlight those areas in which to focus to improve the quality of care for patients with this disease. Understanding the relationship between risk factors, process of care, and outcomes will be of importance to patients, clinicians, and policy makers. The purpose of this article is to review the burden of PAD and to discuss the association of process of care with adverse limb outcomes in patients with PAD.

Initial experience with dorsal venous arch arterialization for limb salvage

Surgical reconstruction for patients with symptomatic lower extremity arterial occlusive disease is successful when a suitable distal target vessel is present. In patients with unreconstructable disease, practical surgical options are at a minimum. We report our initial experience with dorsal venous arch arterialization (DVAA) for limb salvage. Patients with a lower extremity arteriogram and tibia/plantar artery duplex scan demonstrating unreconstructable occlusive disease were evaluated for DVAA. The venous arch valve lysis technique consisted of retrograde balloon catheter, arterial dilator disruption, and direct valvulectomy. Outcome variables included patency, limb salvage rate, and toe pressure alterations. Initial results suggest that DVAA may be a viable option for end-stage limb salvage. Application of the DVAA appears to be more suitable for patients with symptoms secondary to atherosclerosis than those with Buerger's disease.

Proximity arteriography: cost-effectiveness in asymptomatic penetrating extremity trauma

PURPOSE

Many urban trauma centers have abandoned proximity arteriography, which is defined as exclusion arteriography used to evaluate the asymptomatic patient with penetrating extremity trauma near major arteries. However, decision analysis has not been applied to study proximity arteriography.

MATERIALS AND METHODS

The cost-effectiveness of proximity arteriography was examined by creating a decision model that compared arteriography with observation after patient examination in the trauma unit. The model used predominantly literature-derived estimates for input variables and outcomes. The authors retrospectively reviewed arteriograms for 1 year to identify major occult injuries (requiring intervention) at their institution. After a resource-based cost analysis from the taxpayers' perspective, the cost-effectiveness ratio was calculated (incremental cost per quality-adjusted life year [QALY] gained) for proximity arteriography.

RESULTS

For proximity trauma, arteriography is a dominant strategy (more effective and costs less) at a prevalence of major occult injury of 5.5% or more. Observation is a dominant strategy if the prevalence is from 0% to 0.5% or 2.0%, depending on arteriography complication assumptions. In between, arteriography is cost-effective, with a ratio of $12,100 per QALY at 2.5% prevalence (base case). Besides prevalence of occult injury, the model is sensitive to outcome assumptions for occult injuries.

CONCLUSION

Proximity arteriography is a cost-effective procedure if major occult injuries equal or exceed 1.0%.

A bibliography of cost-effectiveness practices in physical medicine and rehabilitation: AAPM&R white paper

Cost-effectiveness studies attempt to determine the ratio of costs to outcomes of a particular intervention or treatment and to compare a standard intervention with an alternative intervention to determine if the alternative is more cost effective. The goal is to establish priorities for the resources allocation and to decide among alternative interventions for the same medical condition. The global process of rehabilitation does not usually lend itself to cost-effective analysis (due to the complex set of treatments provided) but rather to specific interventions and specific aspects of outcome. The American Academy of Physical Medicine and Rehabilitation has published a cost effectiveness annotated bibliography on the Internet (http://www.aapmr.org/memphys/cebfinala.htm) that identifies 132 studies in the literature that meet specified criteria and are related to the field of rehabilitation. This White Paper attempts to interpret and synthesize the studies in that bibliography that relate to stroke, spinal cord injury (SCI), orthopedic conditions, pain syndromes, amputations, and traumatic brain injury (TBI). Most studies support the cost effectiveness of care for stroke and SCI in dedicated units or centers rather than in a general medical unit. Studies also support back programs and revascularization procedures in limb ischemia. Studies in TBI underscore the significant financial resources for the care of these patients as well as the potential benefit from rehabilitation services even in the most severely injured. Further high quality research in this area is needed.

Cost and patency rate targets for the development of endovascular devices to treat femoropopliteal arterial disease

PURPOSE

To determine the criteria that would make use of an endovascular device cost-effective compared with bypass surgery and percutaneous transluminal angioplasty in the treatment of femoropopliteal arterial disease.

MATERIALS AND METHODS

A decision model was developed to compare treatment with the use of a hypothetical endovascular device with established therapies. Cost-effectiveness from the perspective of the health care system was considered. Outcome measures were lifetime costs and quality-adjusted life-years. With the use of net health benefit calculations and threshold analysis, combinations of costs and patency rates were determined that would make the device cost-effective compared with established therapies. In subgroup and sensitivity analyses, the effect on decision-making of sex, age, indication, lesion type, procedural risk, and society's willingness to pay for incremental gain in health were explored.

RESULTS

Use of a device that costs $3,000 would be cost-effective compared with bypass surgery for critical ischemia if the 5-year patency rate is 29%-46%. Use of the same device would be cost-effective compared with angioplasty for disabling claudication and stenosis if the 5-year patency rate is 69%-86%.

CONCLUSION

The target combinations of costs and patency rates found in this study are probably attainable, and further development of such endovascular devices seems warranted.

Duplex scan surveillance during the first year after infrainguinal autologous vein bypass grafting surgery: costs and clinical outcomes compared with other surveillance programs

PURPOSE

In this study we assessed the costs and clinical outcomes of duplex scan surveillance during the first year after infrainguinal autologous vein bypass grafting surgery and compared duplex scan surveillance, ankle-brachial index surveillance, and clinical follow-up.

METHODS

In a clinical study, 293 patients (mean age, 70.1 years; 58.7% men) with peripheral arterial disease were observed in a duplex scan surveillance program after infrainguinal autologous vein bypass grafting surgery. Costs were calculated from the health care perspective for surveillance and subsequent interventions from 30 days to 1 year postoperatively. All costs are presented in 1995 US dollars per patient. In a simulation model, we estimated the costs and amputations of duplex scan surveillance, ankle-brachial index surveillance, and clinical follow-up conditional on the indication for surgery. The main outcome measure was the incremental cost per major amputation per patient avoided during the first postoperative year.

RESULTS

Duplex scan surveillance was the least expensive ($2823) and resulted in the fewest major amputations (17 per 1000 patients examined), compared with ankle-brachial index surveillance ($5411 and 77 amputations per 1000 patients) and clinical follow-up ($5072 and 77 amputations per 1000 patients). In patients treated for critical limb ischemia, duplex scan surveillance was the least expensive ($2974) and resulted in the fewest major amputations (19 per 1000 patients). Under all surveillance programs, 13 major amputations per 1000 patients treated for intermittent claudication were performed, and clinical follow-up had the lowest costs ($1577). In a sensitivity analysis that assumed that duplex scan surveillance could have avoided six major amputations per 1000 patients treated for intermittent claudication compared with the other programs, duplex scan surveillance had an incremental cost of $80,708 per major amputation per patient avoided compared with clinical follow-up.

CONCLUSION

Duplex scan surveillance is highly effective for patients treated for critical limb ischemia, leading to a reduction of major amputations and consequently to a reduction in costs compared with other surveillance programs. In patients treated for intermittent claudication, the evidence supporting duplex scan surveillance is less firm, but if duplex scan can avoid six major amputations per 1000 patients examined, the incremental costs are justified.

Limb salvage after successful pedal bypass grafting is associated with improved long-term survival

OBJECTIVES

Assessments of outcome after reconstruction for critical limb ischemia frequently ignore functional result and long-term morbidity and mortality. This study was undertaken to identify factors affecting long-term clinical outcome and survival after pedal bypass grafting.

METHODS

The clinical data of 256 consecutive patients who underwent pedal bypass grafting for critical limb ischemia over a 12-year period were retrospectively analyzed.

RESULTS

A total of 174 men and 82 women (median age, 70 years; range, 30-91 years) underwent 280 pedal bypass graft placements with autologous vein. Seventy-five percent of the patients were diabetic, and 20% had renal insufficiency (serum creatinine level > 2 mg/dL). The in-hospital mortality rate was 1.6% (4/256). The mean follow-up was 2.7 years (range, 0.1-10.1 years). Rates of primary and secondary patency, limb salvage, and survival at 5 years were 58%, 71%, 78%, 60%, respectively. A total of 160 limbs (57%) required additional interventions. Nineteen early graft thrombectomies/revisions and nine early amputations were performed. One hundred thirty-eight late interventions included 31 graft salvage procedures, 27 wound debridements, and 34 minor and 42 major amputations. At last follow-up or death, 219 (78%) limbs were being used for ambulation. End-stage renal disease (ESRD) and composite vein grafts predicted limb loss (P <.001, P <.001, respectively). Overall survival at 5 years was 60%. Survival after amputation was 79%, 53%, and 26% at 1, 3, and 5 years. Amputation and ESRD predicted higher mortality (P =.014, P =.0001, respectively).

CONCLUSIONS

Pedal bypass grafting resulted in good functional limb salvage, but at the expense of multiple interventions in more than half the cases. ESRD and composite vein graft were associated with poor long-term limb salvage. Amputation after bypass grafting was associated with significantly worse long-term survival.

An economic appraisal of lower extremity bypass graft maintenance

OBJECTIVE

Infrainguinal graft surveillance leads to intervention on the basis of duplex-identified stenoses. We have become increasingly concerned about the high frequency with which such revisions are required to maximize graft patency and limb salvage rates. The economic implications of these procedures have not been carefully analyzed or justified.

METHODS

We retrospectively reviewed 155 consecutive autogenous infrainguinal bypass grafts performed for chronic leg ischemia in 141 patients. All patients were enrolled in a prospective surveillance program using color flow duplex imaging. Full economic appraisal (cost analysis, cost-effect analysis, and cost-benefit analysis) was performed for all graft surveillance and limb salvage-related interventions through use of standard accounting and valuation techniques.

RESULTS

Mean follow-up was 27 months. Five-year assisted primary patency (72%) and limb salvage rates (91%) were calculated by means of life table analysis. A total of 61 grafts required 86 revisions. Within 1 year of implantation, 36% of the grafts required revision. During this first year, the mean cost per graft enrolled was $9417. Time intervals after the initial year demonstrated a reduced annual revision rate (6%) and cost ($1725 per graft). The mean 5-year cost of graft maintenance ($16,318) approached that of the initial bypass graft ($19,331). The sum of the initial cost of bypass graft and 5-year graft maintenance cost ($35,649) was similar to the cost of amputation ($36,273). Grafts revised for duplex-detected stenoses (n = 46), in comparison with those revised after thrombosis (n = 15), had an improved 1-year patency (93% vs 57%; P <.01), required fewer amputations (2% vs 33%; P <.01), less frequently required multiple graft revisions (P =.06), and generated fewer expenses (at 12 months after revision, $17,688 vs $45,252, P <.01).

CONCLUSION

The cost associated with graft maintenance is significant, particularly within the first year, and demands consideration. Revision of a duplex-identified stenosis was significantly less costly than revision after graft thrombosis. Compared with the cost of limb amputation, limb salvage-related expenses appear to be justified.

Is thrombolysis of lower extremity acute arterial occlusion cost-effective?

BACKGROUND

The TOPAS (thrombolysis or peripheral artery surgery) trial randomized 544 patients with acute lower extremity ischemia to either surgery or thrombolysis. Although statistically equivalent 1-year morbidities and mortalities were demonstrated, the comparative cost-effectiveness of these two interventions has not been explored.

MATERIALS AND METHODS

We constructed a Markov decision-analytic model to determine the cost-effectiveness of thrombolysis relative to surgery for a hypothetical cohort of patients with acute lower extremity arterial occlusion. Our measure of outcome was the cost-effectiveness ratio (CER), defined as the incremental lifetime cost per quality-adjusted life year gained. Estimates of 1-year outcomes were based on the TOPAS trial: mortality (lysis, 20%; surgery, 17%), amputation (lysis, 15%; surgery, 13%), the number of additional interventions required following the initial procedure (lysis, 544; surgery, 439). Procedural costs were estimated from the cost accounting system at the New York Presbyterian Hospital as well as from the literature.

RESULTS

Operative intervention for acute lower extremity arterial occlusion extended life and was less costly compared to thrombolysis. The projected life expectancy for patients who underwent initial surgery was 5.04 years versus 4.75 years for initial thrombolysis. The lifetime costs were $57,429 for surgery versus $dollar;76,326 for thrombolysis. In performing sensitivity analyses, a threshold CER of $60,000 was considered what society would pay for accepted medical interventions. Thrombolysis became cost-effective if the 1-year mortality rate for lysis was lowered from 20 to 10.7%, if the amputation rate for lysis diminished from 15 to 3.9%, or if the 1-year cost of lysis could be reduced to a level below $13,000.

CONCLUSIONS

Initial surgery provides the most efficient and economical utilization of resources for acute lower extremity arterial occlusion. The high cost of thrombolysis is related to the expense of the lytic agents, the need for subsequent interventions in patients treated with initial lysis, and the long-term costs of amputation in patients who fail lytic therapy.

Cost of prostheses in patients with unilateral transtibial amputation for vascular disease. A population-based follow-up during 8 years of 112 patients

We analyzed the cost of prostheses for patients amputated because of vascular disease. During 1 year, 112 patients were treated with a primary unilateral transtibial amputation in Malmöhus county, Sweden, which has 527,000 inhabitants. During the first 6 months after the amputation, 50% (56/112) of the patients had received a prosthesis. At 6 months, 49 patients (7 had died) were examined, 18 had poor and 31 had good prosthetic function. Within 1 year, 71 (63%) patients had been fitted with a prosthesis. During 8 years after the amputation, they received altogether 137 prostheses and 54 exchange sockets; 59% of the prostheses and 26% of the sockets were delivered during the first year. Each patient received a median of 1 prosthesis and 1 extra socket. During the 8-year period, the total cost of prostheses, sockets and maintenance for the 71 patients was USD 228,746, representing a median cost of USD 1,582 per patient. The total cost of maintenance of the prostheses during the same period was USD 37,959, representing 20% of the total cost of all the prostheses and sockets. There was no statistically significant difference in the costs between patients with good or poor function.

Cost-identification analysis of revascularization procedures on patients with peripheral arterial occlusive disease

OBJECTIVE

To determine average total in-hospital costs of various revascularization procedures for peripheral arterial occlusive disease; to examine the effect of procedure-related complications and patient characteristics on these costs; and to examine whether costs have changed over time.

METHODS

We collected cost data on all admissions involving one revascularization procedure for peripheral arterial occlusive disease at the Brigham and Women's hospital from 1990 through 1995 (n = 583). The main outcome measures were total costs per admission in 1995 US dollars and length of stay in days.

RESULTS

For each of 12 different procedures identified, total costs per admission varied considerably. Multiple linear regression analysis was performed to determine the effect of local and systemic complications and of patient characteristics on total in-hospital costs per admission. The additional cost incurred for fatal systemic complications was $11,675 (P = .004) and for nonfatal systemic complications was $9345 (P < .001). The results demonstrated significant additional costs with management of critical ischemia versus intermittent claudication ($4478, P < .001), presence of coronary artery disease ($1287, P = .05), female sex ($1461, P = .03), and advanced age ($1345, P = .02). No statistically significant changes over time were demonstrated.

CONCLUSION

Total in-hospital costs per admission for peripheral revascularization procedures are highly variable and significantly increased by procedure-related complications, advanced age, female sex, management of critical ischemia, and presence of coronary artery disease.

Patient recovery after infrainguinal bypass grafting for limb salvage

PURPOSE

The outcome of infrainguinal bypass surgery for limb salvage has traditionally been assessed by graft patency rates, limb salvage rates, and patient survival rates. Recently, functional outcome of limb salvage surgery has been assessed by patient ambulatory status and independent living status. These assessments fail to consider the adverse long-term patient effects of delayed wound healing, episodes of recurrent ischemia, and need for repeat operations. An ideal result of infrainguinal bypass surgery for limb salvage includes an uncomplicated operation, elimination of ischemia, prompt wound healing, and rapid return to premorbid functional status without recurrence or repeat surgery. The present study was performed to determine how often this ideal result is actually achieved.

METHODS

The records of 112 consecutive patients who underwent initial infrainguinal bypass surgery for limb salvage 5 to 7 years before the study were reviewed for operative complications, graft patency, limb salvage, survival, patient functional status, time to achieve wound healing, need for repeat operations, and recurrence of ischemia.

RESULTS

The mean patient age was 66 years. The mean postoperative follow-up was 42 months (range, 0 to 100.1 months). After operation 99 patients (88%) lived independently at home and 103 (92%) were ambulatory. There were seven perioperative deaths (6.3%), and wound complications occurred in 27 patients (24%). By life table, the assisted primary graft patency and limb salvage rates of the index extremity 5 years after operation were 77% and 87%, respectively, and the patient survival rate was 49%. At last follow-up or death, 73% of the patients (72 of 99) who lived independently at home before the operation were still living independently at home, and 70% (72 of 103) of those who were ambulatory before the operation remained ambulatory. Wound (operative and ischemic) healing required a mean of 4.2 months (range, 0.4 to 48 months), and 25 patients (22%) had not achieved complete wound healing at the time of last follow-up or death. Repeat operations to maintain graft patency, treat wound complications, or treat recurrent or contralateral ischemia were required in 61 patients (54%; mean, 1.6 reoperations/patient), and 26 patients (23.2%) ultimately required major limb amputation of the index or contralateral extremity. Only 16 of 112 patients (14.3%) achieved the ideal surgical result of an uncomplicated operation with long-term symptom relief, maintenance of functional status, and no recurrence or repeat operations.

CONCLUSIONS

Most patients who undergo infrainguinal bypass surgery for limb salvage require ongoing treatment and have persistent or recurrent symptoms until their death. A significant minority have major tissue loss despite successful initial surgery. Clinically important palliation is frequently achieved by bypass surgery, but ideal results are distinctly infrequent.

Costs and duration of care for lower extremity ulcers in patients with diabetes

Medical and pharmaceutical insurance claims associated with lower extremity diabetic ulcers were examined retrospectively to better understand the costs and duration of treatment in clinical practice. The study population consisted of working-age individuals (18 to 64 years old) with health care benefits provided through private employer-sponsored insurance plans. Diagnostic information contained in the claims database was used to identify the severity of the ulcers, and the charges associated with treatment were based on claims data. Claims for lower extremity ulcers were found in 5.1% of individuals with diabetes. Although many lower extremity ulcers heal with standard treatment, some are more resistant to treatment and require costly ongoing medical care. Almost half of these cases were associated with deep infection, osteomyelitis, or amputation. Total payments for treatment of lower extremity ulcers in this population averaged $2687 per patient per year, or $4595 per ulcer episode, with inpatient expenditures accounting for more than 80% of these costs. Costs were significantly higher for patients with more severe ulcers or with inadequate vascular status in the affected limb. We concluded that lower extremity ulcers occur in a large number of working-age people with diabetes and contribute significantly to the morbidity associated with this disease. The high cost of treating diabetic foot ulcers suggested by this analysis argues for the development of better treatment strategies and outcomes assessments for these patients.

Effects of vascular surgery on amputation rates and mortality

OBJECTIVES

To study the relation between rates of vascular interventions, amputations and mortality in a defined population.

DESIGN

Retrospective comparison between two consecutive 4-year periods.

SETTING

Swedish district hospital covering a population of 125,000.

MATERIAL

Three hundred and sixty-seven lower limb amputations and 1080 vascular procedures.

RESULTS

The number of legs treated for limb-threatening ischaemia with either revascularisation or amputation increased from 269 to 289. The rate of vascular interventions for limb-threatening ischaemia increased from the first to the second period by 65%, while the rate of amputations decreased by 23%. Limb salvage rate at 30 months increased from 37% to 53% (p < 0.0000). The reduced amputation rate was entirely related to primary amputations. The adjusted risk of amputation for patients treated in the second period was half of that for patients treated in the first period (relative risk = 0.49, p = 0.0001), while mortality was similar in both periods. Among survivors, the proportion of patients with intact legs was higher in the second period than in the first, while no difference was found between the two periods among deceased patients.

CONCLUSIONS

Increased vascular intervention leads to improved limb salvage rates and reduced amputation rates. It is important for both ethical and economical reasons to identify good responders to revascularisation, because the choice of initial treatment will only influence limb salvage but not survival.

Impact of a critical pathway on the results of carotid endarterectomy in a tertiary care university hospital: effect of methods on outcome

PURPOSE

A carotid endarterectomy critical pathway (CP) targeting a 3-day postoperative course was introduced in March 1994. This retrospective analysis assesses its impact on operative results, postoperative length of stay (POD), and cost of hospitalization (COH).

METHODS

One hundred eighty-six patients who underwent 201 carotid endarterectomy procedures from Nov. 1992 to Feb. 1994 (Pre-CP; n = 67) and from Apr. 1994 to Jul. 1995 (Post-CP; n = 134) at Johns Hopkins Hospital, a tertiary care referral center, were evaluated.

RESULTS

The Pre-CP and Post-CP groups had similar risk factors, postoperative morbidity rates, and mortality rates. Furthermore, they had similar mean POD (Pre-CP, 6.0 +/- 0.5 days; Post-CP, 5.7 +/- 0.6 days; p = 0.79) and COH. However, only 85 of the Post-CP (63%) patients were actually placed on the CP (CP-starters); the mean POD was 3.4 +/- 0.3 days among these CP-starters (p < 0.0001) and 2.8 +/- 0.1 days among the 74 Post-CP patients (55%) that remained on the pathway (CP-finishers; p < 0.0001). The mean COH was reduced from $12,881 (Pre-CP) to $9701 for the CP-starters (p = 0.01) and to $8572 for the CP-finishers (p = 0.0001). However, we found that only 47 of the Pre-CP patients (70%) would have been eligible for the CP, and the mean POD among those cases was 4.2 +/- 0.4 days, which was not different than the mean POD among the CP-starters (p = 0.17). The mean COH of the eligible Pre-CP cases, $9508, was not significantly different from the COH of the CP-starters (p = 0.97).

CONCLUSIONS

This subset analysis emphasizes the importance of establishing an accurate "control" group when studying a CP, because using all of the Pre-CP cases as the "control" group in the original analysis, including patients who would not have been candidates for the CP, clearly overstated the beneficial impact of the CP.

Predictors of long-term patient survival after in situ vein leg bypass

PURPOSE

The objective was to determine the long-term survival rates of patients who undergo distal arterial bypass surgery and to identify the preoperative factors that are predictive of survival.

METHODS

Three hundred fifty-eight consecutive in situ distal leg bypass procedures were performed between July 1986 and December 1995. The relationship between 13 preoperative variables and late survival were determined using both univariate (Kaplan-Meier) and multivariate (Cox regression) statistical techniques.

RESULTS

The cumulative survival rates at 1, 3, 5, and 7 years were 86.6% +/- 2.0%, 63.2% +/- 3.0%, 46.9% +/- 3.4%, and 35.3% +/- 3.8%, respectively. Using Cox regression, four significant variables were found to be associated with lower late survival rates: male gender, diabetes, chronic renal insufficiency (patients with creatinine levels greater than or equal to 1.7 mg/dl or 150 SI units), and a history of cerebrovascular disease (p < 0.001 for model). When none of these four variables were present, the predicted 5-year survival rate was 71%, whereas the survival rate was reduced to 43% to 60% when one was present, 23% to 42% when two were present, 8% to 22% when three were present, and 2% when all four were present.

CONCLUSIONS

This study defines the long-term survival rates in a cohort of patients after undergoing distal bypass surgery and demonstrates that certain preoperative factors are predictive of late survival. Knowledge of these factors may be useful to assist in individual operative decisions between aggressive attempts at distal revascularization versus primary amputation.

Functional outcome after infrainguinal bypass for limb salvage

PURPOSE

Functional outcome after infrainguinal bypass (IB) has recently been assessed with global health status questionnaires but not by criteria specific to the objectives of IB (i.e., maintenance of independent living and ambulation). Preoperative and postoperative living situation and ambulatory status were evaluated in patients who underwent IB for limb salvage (LS) indications.

METHODS

For patients in whom IB was performed for LS from January 1980 to July 1995, living situation (independent or dependent) and ambulatory status were assessed before the onset of the need for LS surgery and 6 months after surgery. The importance of risk factors (age, sex, diabetes, heart disease, hypertension, renal insufficiency or failure, previous leg bypass, indication for surgery, postoperative morbidity, graft patency) was assessed by multivariate analysis.

RESULTS

IB for LS was performed in 513 patients. Before the development of the indication for LS surgery, 92% lived independently and 91% were ambulatory. The operative mortality rate was 2.7%. At 6 months, 86% were alive and the assisted primary graft patency rate was 92%. Ninety-nine percent of survivors who lived independently before developing the need for LS surgery remained independent 6 months after surgery, and 97% of those who were ambulatory before developing the need for LS surgery were ambulatory 6 months after surgery. Only one of 25 survivors (4%) who were not living independently before surgery achieved independent living 6 months after surgery. Twenty-one percent of nonambulatory patients (6 of 29) became ambulatory. Multivariate analysis confirmed the importance of preoperative living situation and ambulatory status in predicting outcome at 6 months (p < 0.0001). Amputation and loss of primary patency were predictive of poor ambulatory status at 6 months (p < 0.0001, p = 0.025, respectively). The overall 5-year survival rate was 48.1%.

CONCLUSIONS

Preoperative independence and ambulation best predict postoperative independence and ambulation after IB for LS indications. IB procedures performed for limb salvage have a low operative mortality rate and maintain independent living and ambulation in 99% and 97% of patients, respectively. Poor overall long-term outcome and survival in LS patients results from intercurrent illness and not from IB.

Operations, total hospital stay and costs of critical leg ischemia. A population-based longitudinal outcome study of 321 patients

In a longitudinal analysis of all 321 patients in a defined population having surgery for critical leg ischemia during 1 year in Malmöhus county (0.53 million inhabitants), Sweden, we investigated all vascular procedures and amputations on both legs, total hospital stay and hospital costs from the first procedure in each patient until death or at follow-up at least 6 years postoperatively. The first (key) operation during the inclusion year was a reconstructive vascular procedure in 96 patients, a restorative vascular procedure in 111 and a major amputation in 114 patients. One third of those with a reconstructive and half of those with a restorative key procedure had an ipsilateral major amputation. The mean number of surgical procedures and length of hospital stay among all patients were 3 (1-19) procedures and 117 (1-1097) days, respectively. Of the total number of days in hospital, less than half were in surgical departments, 10% in other acute-care departments and almost half in rehabilitation clinics and nursing homes. The total hospital and surgical costs among all patients were USD 15.1 million (mean USD 47,000/patient), with no significant differences in relation to the key operation. We conclude that patients who have undergone surgery for critical leg ischemia accumulate very high total long-term hospital costs due to the need for repetitive surgery and long hospital stays. Our findings also show that a longitudinal study, including hospital stay in departments other than surgical, is necessary for a correct cost-and-outcome analysis.

Impact of clinical pathways on hospital costs and early outcome after major vascular surgery

PURPOSE

The purpose of this study was to determine whether major vascular surgery could be performed safely and with significant hospital cost savings by decreasing length of stay and implementation of vascular clinical pathways.

METHODS

Morbidity, mortality, readmission rates, same-day admissions, length of stay, and hospital costs were compared between patients who were electively admitted between September 1, 1992, and August 30, 1993 (group 1), and January 1 to December 31, 1994 (group 2), for extracranial, infrarenal abdominal aortic, and lower extremity arterial surgery. For group 2 patients, vascular critical pathways were instituted, a dedicated vascular ward was established, and outpatient preoperative arteriography and anesthesiology-cardiology evaluations were performed. Length-of-stay goals were 1 day for extracranial, 5 days for aortic, and 2 to 5 days for lower extremity surgery. Emergency admissions, inpatients referred for vascular surgery, patients transferred from other hospitals, and patients who required prolonged preoperative treatment were excluded.

RESULTS

With this strategy same-day admissions were significantly increased (80% [145/177] vs 6.2% [9/145]) (p < 0.0001), and average length of stay was significantly decreased (3.8 vs 8.8 days) (p < 0.0001) in group 2 versus group 1, respectively. There were no significant differences between group 1 and group 2 in terms of overall mortality rate (2.1% [3/145] vs 2.3% [4/177]), cardiac (3.4% [5/145] vs 4.0% [7/177]), pulmonary (4.1% [6/145] vs 1.7% [3/177]), or neurologic (1.4% [2/145] vs 0% [0/177]) complications, or readmission within 30 days (11.3% [16/142] vs 9.2% [16/173]) (p > 0.05). There were also no differences in morbidity or mortality rates when each type of surgery was compared. Annual hospital cost savings totalled $1,267,445.

CONCLUSION

Same-day admission and early hospital discharge for patients undergoing elective major vascular surgery can result in significant hospital cost savings without apparent increase in morbidity or mortality rates.

Cost-efficacy issues in the treatment of peripheral vascular disease: primary amputation or revascularization for limb-threatening ischemia

Controlling rising health care costs represents a major challenge to our society. Due to the aging of the population and the increasing number of patients with vascular disease, vascular specialists will be under mounting pressure by the managed care industry to provide the most cost-effective care for these patients. One particular controversy is whether to attempt revascularization in the patient with limb-threatening ischemia or to proceed directly with primary amputation. Although it has been assumed that the operative risk for revascularization procedures is high in elderly patients with a severely ischemic limb, mortality rates in the sickest patients are actually higher for amputation. It is also incorrect to assume that the duration of hospitalization is shorter for patients undergoing amputation than for patients undergoing revascularization. For both types of procedures, it is complications that prolong the length of hospital stay, and the rate of secondary amputation following a revascularization attempt is low (8.5%), compared with the rate of operative revision in patients following primary below-knee amputation (23%). The costs for revascularization and primary amputation are similar when the costs of a prosthesis and rehabilitative therapy are included in the calculations for amputation. The rationale for primary amputation assumes that patients will ambulate successfully with a prosthesis; however, many do not, and thus costs for institutionalization must be included in the equation. Long-term costs following revascularization were $28,374 in patients with a viable limb, compared with $56,809 in those undergoing secondary revascularization. The key to minimizing health care costs in this population is careful patient selection for initial revascularization, with aggressive long-term surveillance to ensure graft patency and limb viability.

Autologous saphenous vein popliteal-tibial artery bypass for limb-threatening ischemia: a reassessment

BACKGROUND

The purpose of this review was to ascertain the cumulative primary and secondary graft patency rates, the cumulative limb salvage rate, and the frequency of atherosclerotic disease progression proximal to the graft origin, in patients with autologous saphenous vein popliteal-tibial artery bypass grafts whose operative indication was limb-threatening ischemia.

PATIENTS AND METHODS

Forty-three short autologous saphenous vein grafts originating from the popliteal artery were retrospectively reviewed. The life-table method was used to determine primary and secondary graft patency and limb salvage rates. Atherosclerotic disease progression proximal to the graft origin was assessed via follow-up arteriography, segmental limb pressures, or pulse-volume recordings. All other data were compared by chi-square analysis.

RESULTS

The cumulative primary graft patency rate at 1, 3, and 5 years (86%, 66%, 58%) was similar to the cumulative secondary patency rate (90%, 70%, 62%) and the cumulative limb salvage rate (80%, 55%, 55%). No patient developed hemo-dynamically significant atherosclerotic disease proximal to the graft origin during the follow-up period.

CONCLUSIONS

The similarity of the life-table data suggests graft-dependent, poorly collateralized limbs; it is therefore not uncommon for these patients to require major amputations shortly after bypass failure. There was no evidence of critical proximal disease progression that might warrant a more proximal graft origin. Poplitealtibial artery bypass grafts are durable, with acceptable graft patency and limb salvage rates.

Preoperative factors that predict hospital length of stay after distal arterial bypass

PURPOSE

The purpose of this study was to identify the preoperative factors that are predictive of prolonged hospital length of stay (LOS) and to discuss strategies that might assist in minimizing LOS for this select group of patients.

METHODS

Two hundred seventy-five arterial bypass procedures with the in situ technique were performed between 1986 and 1993. The relationship between 14 preoperative variables and hospital LOS was analyzed with both univariate (Kaplan-Meier) and multivariate (Cox regression) statistical techniques. A model was developed to determine the significant preoperative variables that were associated with prolonged LOS.

RESULTS

The primary and secondary patency rates and limb salvage rates at 4 years were 73.3% +/- 3.2%, 78.9% +/- 2.9%, and 81.9% +/- 3.2%, respectively. The median postoperative LOS was 15 days, with a mean +/- SD of 17.8 +/- 12.3 days (range 4 to 93 days). With Cox regression analysis, the variables that were significant predictors of LOS (with a model p value < 0.002) were age (greater than 74 years vs less than 75), history of cerebrovascular disease (transient ischemic attack, stroke, past carotid endarterectomy vs nil), and operative indication (limb salvage vs disabling claudication).

CONCLUSIONS

This study illustrates that certain preoperative variables are predictive of prolonged postoperative LOS after in situ bypass. The significant preoperative factors identified should be used to direct specific care and discharge planning for these individuals.

Vascular disease in the elderly patient

At a time of potentially dramatic changes in health care policy in this country, and in view of the necessity for health care cost containment, physicians are expected to exercise serious introspection in the selection of treatment for the elderly patient with peripheral arterial disease. These decisions should be made while acknowledging that it is the goal of the health-care provider "to postpone chronic illness, to maintain vigor, and to slow social and psychological involution." For the elderly patient with an abdominal aortic aneurysm, with significant carotid disease, or with limb-threatening peripheral ischemia, the evidence is compelling that timely surgical intervention in properly selected patients is well tolerated and will satisfy this goal.

Infrainguinal revascularization in end-stage renal disease

Patients with end-stage renal disease are being maintained for longer periods with dialysis or renal transplantation. Although renal failure itself is associated with occlusive peripheral vascular disease, such patients often have additional comorbid risk factors. In this series, 88% of patients were diabetic, 93% were hypertensive, and 44% were smokers, all factors that exacerbate the severity of their vasculopathy. As a consequence, the vascular surgeon is increasingly being confronted with limb-threatening peripheral vascular disease in this population. We performed 34 infrainguinal bypasses in 27 patients during a 8-year period from 1986 to 1993. Fifty percent of these were bypasses to the infrapopliteal level. The 12- and 48-month graft patency was 64% and 38%, respectively, by life-table analysis. The limb salvage rate was 65% and 58% at 12 and 48 months. The perioperative mortality rate was 5.9% and the morbidity rate was 37%. Most of the limb loss (66%) occurred during the first 3 months after surgery as a result of acute graft occlusion or nonhealing of an ulcer or minor amputation site. We believe that this reflects an increasingly aggressive approach to limb salvage in patients with end-stage renal disease. Four limbs were lost despite a patent graft. Infrainguinal bypass is a viable management option for limb salvage in patients with end-stage renal disease. These procedures can be undertaken with acceptable perioperative mortality and with a 12-month limb salvage rate of 65%.

Rehabilitation of lower limb amputees and some implications for surgical management

Aspects of peri-operative management, amputation level and rehabilitation of the lower limb amputee are reported in the context of a review of a rehabilitation service for amputees which includes an integrated prosthetic service. Two hundred admissions were reviewed and some complex cases described. It is concluded that: a very close liaison between the surgeon and the rehabilitation team (ideally with preoperative consultation) is in the patient's best interests; any person previously walking (or a potential walker) should be considered for a trial of prosthetic walking; an integrated prosthetic service enhances the efficiency of the rehabilitation service; and that modification of the current Artificial Limb Scheme to allow manufacture of first definitive limbs in prosthetic rehabilitation units would further enhance service to patients.