Risk prediction of 30-day mortality after lower extremity major amputation

Predicting Functional Outcomes Following Dysvascular Lower Limb Amputation: An Evidence Review of Personalizing Patient Outcomes

Most research on people undergoing lower limb amputations for dysvascular disease summarizes average patient outcome risks and average associations between patient factors and these outcomes. More recently, the importance of predicting patient-specific outcomes based on individual factors (ie, personalized rehabilitation) has become evident. This article reviews the evidence and discusses the importance of the following: (1) predicting outcomes to facilitate amputation-level and prosthesis prescription decisions and (2) how prediction models can be leveraged to develop decision support tools to facilitate provider/patient shared decision-making to ensure decisions considering each individual patient's priorities and preferences. Examples of these tools are discussed and referenced.

Prosthetic outcomes after amputation and the impact of mobility level on survival

OBJECTIVE

Lower extremity amputation continues to be necessary in a significant number of patients with peripheral vascular disease. The 5-year survival following lower limb loss is markedly reduced. Many of these patients are never fitted with a prosthesis, and there is a dearth of knowledge regarding the barriers to prosthetic attainment. The goal of this study was to identify the risk factors for not receiving a prosthesis and the effect of mobility level on survival following major amputation.

METHODS

This was a retrospective analysis of all patients that underwent lower extremity amputation by surgeons in our practice from January 1, 2010, to December 31, 2019. Abstracted data included: age, sex, race, body mass index, comorbidities, American Society of Anesthesiologists score, statin use, level of amputation, stump revision, fitting for prosthesis, type of prosthesis, and the United States' Medicare Functional Classification Level, also called K level. Survival was determined using a combination of sources, including the Social Security Death Master File, searches of multiple genealogic registries, and general internet searches. Multivariable logistic regression was used to determine risk factors associated with prosthesis attainment. Multivariable Cox proportional hazard regression with time-dependent covariates was performed to assess risk factors associated with 5-year mortality.

RESULTS

A total of 464 patients were included in this study. The mean age was 65 years, and mean body mass index was 27 kg/m2. The majority of patients were male (68%), White (56%), diabetic (62%), and hypertensive (76%), and underwent below-the-knee amputation (69%). Prosthetic attainment occurred in 185 (40%). On multivariable analysis, age >81 years and current tobacco use were associated with no prosthetic fitting. Overall 5-year survival was 41.9% (95% confidence interval [CI], 37.6%-46.6%) (below-the-knee amputation, 47.7% [95% CI, 42.5%-53.5%]; above-the-knee amputation, 28.7% [95% CI, 22.1%-37.2%]). On multivariable analysis, age >60 years, congestive heart failure, above-the-knee amputation, and no prosthetic attainment were associated with decreased survival. Increasing K level was incrementally associated with improved survival.

CONCLUSIONS

This study has identified several patient factors associated with prosthetic attainment, as well as multiple factors predictive of reduced survival after amputation. Being referred for prosthetic fitting was associated with improved survival not explained by patient characteristics and comorbidities. The Medicare Functional Classification Level K level predicts survival. More research is needed to determine the barriers to prosthetic attainment and if improving a patients K level will improve survival.

Factors Affecting 30-Day Outcomes in Patients Undergoing Nontraumatic Upper Extremity Amputation: A Retrospective Descriptive Longitudinal Study

BACKGROUND

Current literature concerning upper extremity amputations (UEAs) is very sparse. In this study, we conducted the first multicenter retrospective analysis aiming to identify risk factors associated with unfavorable outcomes in patients undergoing nontraumatic UEAs.

METHODS

A retrospective cohort study was conducted using the National Surgical Quality Improvement Program database. Adult patients who underwent nontraumatic UEAs between 2005 and 2021 were divided into two cohorts based on whether they experienced 30-day major morbidity (MM). Thereafter, multivariable binary logistic regression analysis was used to identify risk factors of MM.

RESULTS

From a total of 2984 cases, MM was observed in 8.7% of patients. Factors associated with MM included American Society of Anesthesiologists classes 3 (odds ratio [OR], 2.974 [1.862 to 4.748]) and 4 (OR, 4.736 [2.857 to 7.848]), being underweight (OR, 2.370 [1.251 to 4.491]), and suffering from insulin-dependent diabetes (OR, 1.390 [1.018 to 1.898]). In addition, an infectious surgical indication was associated with an increased risk of MM compared with having a benign (OR, 0.648 [0.488 to 0.682]) or malignant (OR, 0.205 [0.091 to 0.462]) indication. Moreover, patients undergoing shoulder amputations were at an increased risk of MM compared with those undergoing amputations of the forearm/wrist (OR, 0.243 [0.072 to 0.819]) and hands/fingers (OR, 0.286 [0.095 to 0.861]).

CONCLUSION

The risk factors identified for MM after nontraumatic UEAs should guide surgeons toward appropriately identifying high-risk patients and adequately counseling them preoperatively.

Predicting wound complications following lower extremity revascularization

OBJECTIVE

The aim of this study was to create a simple risk score to identify factors associated with wound complications after infrainguinal revascularization.

METHODS

The Veterans Affairs Surgical Quality Improvement Program national data set was queried from 2005 to 2021 to identify 22,114 patients undergoing elective open revascularization for peripheral arterial disease (claudication, rest pain, tissue loss) or peripheral aneurysm. Emergency and trauma cases were excluded. The data set was divided into a two-thirds derivation set and one-third validation set to create a risk prediction model. The primary end point was wound complication (wound dehiscence, superficial/deep wound surgical site infection). Eight independent risk factors for wound complications resulted from the model and were assigned whole number integer risk scores. Summary risk scores were collapsed into categories and defined as low (0-3 points), moderate (4-7 points), high (8-11 points), and very high (>12 points).

RESULTS

The wound complication rate in the derivation data set was 9.7% (n = 1428). Predictors of wound complication included age ≤73 (odds ratio [OR], 1.25; 95% confidence interval [CI], 1.08-1.46), body mass index ≥35 kg/m2 (OR, 1.99; 95% CI, 1.68-2.36), non-Hispanic White (vs others: OR, 1.48; 95% CI, 1.30-1.69), diabetes (OR, 1.23; 95% CI, 1.10-1.37), white blood cell count >9900/mm3 (OR, 1.18; 95% CI, 1.03-1.35), absence of coronary artery disease (OR, 1.27; 95% CI, 1.03-1.35), operative time >6 hours (OR, 1.20; 95% CI, 1.05-1.37), and undergoing a femoral endarterectomy in conjunction with bypass (OR, 1.34; 95% CI, 1.14-1.57). In both the derivation and validation sets, wound complications correlated with risk category. Among the defined categories in the derivation set, wound complication rates were 4.5% for low-risk patients, 8.5% for moderate-risk patients, 13.8% for high-risk patients, and 23.8% for very high-risk patients, with similar results for the internal validation data set. Operative indication did not independently associate with wound complications. Patients with wound complications had higher rates of reoperation and graft failure.

CONCLUSIONS

This risk prediction model uses easily obtainable clinical metrics that allow for informed discussion of wound complication risk for patients undergoing open infrainguinal revascularization.

Predictive Factors for Mortality Following Major Lower Extremity Amputation

BACKGROUND

Despite advances in techniques and care, major amputation bears a high risk for mortality. Previously identified factors associated with increased risk of mortality include amputation level, renal function, and pre-operative white cell count.

METHODS

A single center retrospective chart review was conducted identifying patients who had undergone a major amputation. Chi-squared, t-testing, and Cox proportional hazard modeling were performed examining death at 6 months and 12 months.

RESULTS

Factors associated with an increased risk of six-month mortality include age (OR 1.01-1.05, P < .001), sex (OR 1.08-3.24, P < .01), minority race (OR 1.18-18.19, P < .01), chronic kidney disease (OR 1.40-6.06, P < .001), and use of pressors at the induction of anesthesia for index amputation (OR 2.09-7.85, P < .000). Factors associated with increased risk of 12 month mortality were similar.

DISCUSSION

Patients undergoing major amputation continue to suffer high mortality. Those patients who received their amputation under physiologically stressful conditions were more likely to die within 6 months. Reliably predicting six-month mortality can assist surgeons and patients in making appropriate care decisions.

[Objective measurement tools that predict success in the fitting of major unilateral lower limb amputations patients]

The profile of the patient who most frequently suffers lower limb amputations is usually an elderly patient with high comorbidity. Physiatrists need objective tools in the assessment of these patients that predict the results of prosthetic programs to increase patient safety and efficiency of prosthetic rehabilitation programs. Given the need to update scientific knowledge in this field, we have carried out a review of the literature with the aim of defining a proposal for tools that facilitate decision-making in the indication of prosthetic rehabilitation in these patients. A bibliographic search strategy has been carried out using the scientific databases PubMed, Web of Science, Scopus and Cochrane Library. The quality of the selected articles has been assessed according to the tools proposed by CASPe.

Short-term risk prediction after major lower limb amputation: PERCEIVE study

BACKGROUND

The accuracy with which healthcare professionals (HCPs) and risk prediction tools predict outcomes after major lower limb amputation (MLLA) is uncertain. The aim of this study was to evaluate the accuracy of predicting short-term (30 days after MLLA) mortality, morbidity, and revisional surgery.

METHODS

The PERCEIVE (PrEdiction of Risk and Communication of outcomE following major lower limb amputation: a collaboratIVE) study was launched on 1 October 2020. It was an international multicentre study, including adults undergoing MLLA for complications of peripheral arterial disease and/or diabetes. Preoperative predictions of 30-day mortality, morbidity, and MLLA revision by surgeons and anaesthetists were recorded. Probabilities from relevant risk prediction tools were calculated. Evaluation of accuracy included measures of discrimination, calibration, and overall performance.

RESULTS

Some 537 patients were included. HCPs had acceptable discrimination in predicting mortality (931 predictions; C-statistic 0.758) and MLLA revision (565 predictions; C-statistic 0.756), but were poor at predicting morbidity (980 predictions; C-statistic 0.616). They overpredicted the risk of all outcomes. All except three risk prediction tools had worse discrimination than HCPs for predicting mortality (C-statistics 0.789, 0.774, and 0.773); two of these significantly overestimated the risk compared with HCPs. SORT version 2 (the only tool incorporating HCP predictions) demonstrated better calibration and overall performance (Brier score 0.082) than HCPs. Tools predicting morbidity and MLLA revision had poor discrimination (C-statistics 0.520 and 0.679).

CONCLUSION

Clinicians predicted mortality and MLLA revision well, but predicted morbidity poorly. They overestimated the risk of mortality, morbidity, and MLLA revision. Most short-term risk prediction tools had poorer discrimination or calibration than HCPs. The best method of predicting mortality was a statistical tool that incorporated HCP estimation.

Surgical risk calculators in veterans following lower extremity amputation

OBJECTIVE

To evaluate the accuracy of multiple risk calculators for 30-day mortality on patients undergoing major lower extremity amputation.

METHODS

The actual 30-day mortality at a single Veterans Affairs institution was compared to the predicted outcome from the following risk calculators: ACS-NSQIP, VASQIP, amputation scoring tool (AST), and POTTER elective.

RESULTS

The overall calculated 30-day mortality was similar to the actual mortality with the VASQIP and POTTER elective risk calculators, while the NSQIP and AST over-estimated the 30-day mortality. The predictive accuracy of the POTTER and NSQIP risk calculators were moderate (AUC >0.7), and fair for the VASQIP and AST.

CONCLUSION

Risk assessment tools can provide adjunctive data on predicted 30-day mortality in patients undergoing major lower extremity amputation. In our study, there were differences in predictability of the risk calculators for lower extremity amputation that should be considered when utilizing a risk assessment tool to improve physician-patient shared decision-making.

The PERCEIVE quantitative study: PrEdiction of Risk and Communication of outcome following major lower-limb amputation: protocol for a collaboratiVE study

BACKGROUND

Accurate prediction of outcomes following surgery with high morbidity and mortality rates is essential for informed shared decision-making between patients and clinicians. It is unknown how accurately healthcare professionals predict outcomes following major lower-limb amputation (MLLA). Several MLLA outcome-prediction tools have been developed. These could be valuable in clinical practice, but most require validation in independent cohorts before routine clinical use can be recommended. The primary aim of this study is to evaluate the accuracy of healthcare professionals' predictions of outcomes in adult patients undergoing MLLA for complications of chronic limb-threatening ischaemia (CLTI) or diabetes. Secondary aims include the validation of existing outcome-prediction tools.

METHOD

This study is an international, multicentre prospective observational study including adult patients undergoing a primary MLLA for CLTI or diabetes. Healthcare professionals' accuracy in predicting outcomes at 30-days (death, morbidity and MLLA revision) and 1-year (death, MLLA revision and ambulation) will be evaluated. Sixteen existing outcome-prediction tools specific to MLLA will be examined for validity. Data collection began on 1 October 2020; the end of follow-up will be 1 May 2022. The C-statistic, Hosmer-Lemeshow test, reclassification tables and Brier score will be used to evaluate the predictive performance of healthcare professionals and prediction tools, respectively.

STUDY REGISTRATION AND DISSEMINATION

This study will be registered locally at each centre in accordance with local policies before commencing data collection, overseen by local clinician leads. Results will be disseminated to all centres, and any subsequent presentation(s) and/or publication(s) will follow a collaborative co-authorship model.

Sex, age, and other barriers for prosthetic referral following amputation and the impact on survival

BACKGROUND

Despite advances in peripheral vascular disease treatment, lower extremity amputation continues to be necessary in a significant number of patients. Up to 80% of amputees are not referred for prosthetic fitting. The factors contributing to referral decisions have not been adequately investigated, nor has the impact of prosthetic referral on survival. We characterized differences between patients who were successfully referred to our in-house prosthetists and those who were not, and identified factors associated with prosthetic referral and predictive of survival.

METHODS

This was a retrospective analysis of all patients who underwent lower extremity amputation by surgeons in our practice from January 1, 2010, to June 30, 2017. Data regarding age, sex, race, body mass index (BMI), diabetes, hypertension, hyperlipidemia, end-stage renal disease, prior coronary artery bypass graft surgery, congestive heart failure, tobacco use, American Society of Anesthesiologists (ASA) score, previous arterial procedure, chronic obstructive pulmonary disease, statin use, postoperative ambulatory status, level of amputation, stump revision, and referral for prosthesis were collected. Survival was determined from a combination of sources, including the Social Security Death Master Index, multiple genealogic registries, and internet searches. Multivariable logistic regression was used to determine risk factors associated with prosthesis referral. Multivariable Cox proportional hazard regression with time-dependent covariates was performed to assess risk factors associated with 5-year mortality.

RESULTS

There were 293 patients included in this study. Mean age was 66 years, and mean BMI 27 kg/m². The majority of patients were male (69%), white (53%), with diabetes (65.4%) and hypertension (77.5%), and underwent below-the-knee amputation (BKA) (73%). Prosthetic referral occurred in 123 (42.0%). Overall 5-year survival was 61.7% (95% confidence interval [CI], 55.9%-68.1%) (BKA 64.7% [95% CI, 57.9%-72.3%]; above-the-knee amputation 53.8% [95% CI, 43.4%-66.6%]). On multivariate analysis, age >70 years, female sex, diabetes, ASA score 4 or 5, and current tobacco use were associated with no referral for prosthetic fitting. Patients with BMI 25 to 30, a previous arterial procedure, BKA, and history of stump revision were more likely to be referred. Factors associated with decreased survival were increasing age, higher ASA class, black race, and BMI; prosthetic referral was seen to be protective.

CONCLUSIONS

We identified multiple patient factors associated with prosthetic referral, as well as several characteristics predictive of reduced survival after amputation. Being referred for prosthetic fitting was associated with improved survival not explained by patient characteristics and comorbidities. Further research is needed to determine whether the factors identified as associated with nonreferral are markers for patient characteristics that make them clinically unsuitable for prosthetic fitting or if they are symptoms of unconscious bias or of the patient's access to care.

A Systematic Review and Narrative Synthesis of Risk Prediction Tools Used to Estimate Mortality, Morbidity, and Other Outcomes Following Major Lower Limb Amputation

OBJECTIVE

The decision to undertake a major lower limb amputation can be complex. This review evaluates the performance of risk prediction tools in estimating mortality, morbidity, and other outcomes following amputation.

METHODS

A systematic review was performed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The MEDLINE, Embase, and Cochrane databases were searched to identify studies reporting on risk prediction tools that predict outcomes following amputation. Outcome measures included the accuracy of the risk tool in predicting a range of post-operative complications, including mortality (both short and long term), peri-operative morbidity, need for re-amputation, and ambulation success. A narrative synthesis was performed in accordance with the Guidance on the Conduct of Narrative Synthesis In Systematic Reviews.

RESULTS

The search identified 518 database records. Twelve observational studies, evaluating 13 risk prediction tools in a total cohort of 61 099 amputations, were included. One study performed external validation of an existing risk prediction tool, while all other studies developed novel tools or modified pre-existing generic calculators. Two studies conducted external validation of the novel/modified tools. Nine tools provided risk estimations for mortality, two tools provided predictions for post-operative morbidity, two for likelihood of ambulation, and one for re-amputation to the same or higher level. Most mortality prediction tools demonstrated acceptable discrimination performance with C statistic values ranging from 0.65 to 0.81. Tools estimating the risk of post-operative complications (0.65 - 0.74) and necessity for re-amputation (0.72) also performed acceptably. The Blatchford Allman Russell tool demonstrated outstanding discrimination for predicting functional mobility outcomes post-amputation (0.94). Overall, most studies were at high risk of bias with poor external validity.

CONCLUSION

This review identified several risk prediction tools that demonstrate acceptable to outstanding discrimination for objectively predicting an array of important post-operative outcomes. However, the methodological quality of some studies was poor, external validation studies are generally lacking, and there are no tools predicting other important outcomes, especially quality of life.

The effect of deep vein thrombosis on major adverse limb events in diabetic patients: a nationwide retrospective cohort study

Little is known about the association between deep vein thrombosis (DVT) and arterial complications in patients with type 2 diabetes (T2DM). The aim of this retrospective cohort study was to assess the influence of prior DVT on major adverse limb events (MALEs) and major adverse cardiovascular events (MACEs) in T2DM. A total of 1,628,675 patients with T2DM with or without a history of DVT from 2001 to 2013 were identified in the National Health Insurance Research Database of Taiwan. Before matching, the patients in the DVT group (n = 2020) were older than the control group (66.3 vs. 58.3 years). Patients in the DVT group were more likely to be female than the control group (54.3% vs. 47.5%). Before matching, the DVT group had higher prevalence of most comorbidities, more prescription of antiplatelet, antihypertensive agents and insulins, but less prescription of metformin and sulfonylurea. During a mean follow-up of 5.2 years (standard deviation: 3.9 years), the matched DVT group (n = 2017) have a significantly increased risk of MALE (8.4% vs. 5.2%; subdistribution hazard ratio [SHR] 1.60, 95% CI 1.34-1.90), foot ulcer (5.2% vs. 2.6%, SHR 1.96, 95% CI 1.57-2.45), gangrene (3.4% vs. 2.3%, SHR 1.44, 95% CI 1.10-1.90) and amputation (2.5% vs. 1.7%; SHR 1.42, 95% CI 1.03-1.95) than the 10,085 matched controls without DVT. They also tended to have a greater risk of all-cause mortality (38.1% vs. 33.1%; hazard ratio [HR] 1.18, 95% CI 1.09-1.27) and systemic thromboembolism (4.2% vs. 2.6%; SHR 1.56, 95% CI 1.22-1.99), respectively. We showed the presence of DVT may be associated with an increased risk of MALEs, major amputation, and thromboembolism, contributing to a higher mortality rate in T2DM.

Reducing Nontraumatic Lower-Extremity Amputations by 20% by 2030: Time to Get to Our Feet: A Policy Statement From the American Heart Association

Nontraumatic lower-extremity amputation is a devastating complication of peripheral artery disease (PAD) with a high mortality and medical expenditure. There are ≈150 000 nontraumatic leg amputations every year in the United States, and most cases occur in patients with diabetes. Among patients with diabetes, after an ≈40% decline between 2000 and 2009, the amputation rate increased by 50% from 2009 to 2015. A number of evidence-based diagnostic and therapeutic approaches for PAD can reduce amputation risk. However, their implementation and adherence are suboptimal. Some racial/ethnic groups have an elevated risk of PAD but less access to high-quality vascular care, leading to increased rates of amputation. To stop, and indeed reverse, the increasing trends of amputation, actionable policies that will reduce the incidence of critical limb ischemia and enhance delivery of optimal care are needed. This statement describes the impact of amputation on patients and society, summarizes medical approaches to identify PAD and prevent its progression, and proposes policy solutions to prevent limb amputation. Among the actions recommended are improving public awareness of PAD and greater use of effective PAD management strategies (eg, smoking cessation, use of statins, and foot monitoring/care in patients with diabetes). To facilitate the implementation of these recommendations, we propose several regulatory/legislative and organizational/institutional policies such as adoption of quality measures for PAD care; affordable prevention, diagnosis, and management; regulation of tobacco products; clinical decision support for PAD care; professional education; and dedicated funding opportunities to support PAD research. If these recommendations and proposed policies are implemented, we should be able to achieve the goal of reducing the rate of nontraumatic lower-extremity amputations by 20% by 2030.

Risk Factors for Major Amputation in Diabetic Foot Ulcer Patients

BACKGROUND

The purpose of our study was to identify the new and the more specific risk factors for major amputation in patients with diabetic foot ulcer (DFU).

METHODS

We used data from the Electronic Medical Record (EMR) database of our hospital from February 2014 to July 2020. Patients with DFU and amputation were included in the study. The logistic regression model was adjusted for demographic characteristics and related comorbidities between major and minor amputation groups.

RESULTS

Among 3654 patients with DFU, 363 (9.9%) were amputated. Patients with major versus minor amputation, in multivariable logistic regression models, major amputation independent factors included previous amputation history (odds ratio [OR] 2.31 [95% CI 1.17-4.53], p = 0.02), smoking (2.58 [1.31-5.07], p = 0.01), coronary artery disease (CAD) (2.67 [1.35-5.29], p = 0.03), ankle brachial index (ABI) <0.4 (15.77 [7.51-33.13], p < 0.01), Wagner 5 (5.50 [1.89-16.01], p < 0.01), activated partial thromboplastin time (APTT) (1.23 [1.03-1.48], p = 0.01), glycosylated hemoglobin A1c (HbA1c) (1.23 [1.03-1.48], p = 0.03), hemoglobin (Hb) (0.98 [0.96-1.00], p = 0.01), plasma albumin (ALB) (0.88 [0.81-0.95], p < 0.01) and white blood cell (WBC) (1.10 [1.04-1.16], p < 0.01).

CONCLUSION

Major amputation was associated with previous amputation history, smoking, CAD, Wagner 5, ABI <0.4, HbA1c, Hb, ALB, WBC, and APTT might be a new independent factor. In view of these factors, early prevention and guidance promptly orientated by multidisciplinary is of great significance to reduce the disability rate and economic burden.

Ambulatory Status following Major Lower Extremity Amputation

BACKGROUND

The ability to ambulate following major lower extremity amputation, either below (BKA) or above knee (AKA), is a major concern for all prospective patients. This study analyzed ambulatory rates and risk factors for nonambulation in patients undergoing a major lower extremity amputation.

METHODS

A retrospective review of 811 patients who underwent BKA or AKA at our institution between January 2009 and December 2014 was conducted. Demographic information and co-morbid conditions, including the patients' functional status prior to surgery, at 6 months, and at latest follow up were recorded. Following exclusion criteria, 538 patients were included. Patients who were either independent or used an assistive device were considered ambulatory, while those who were completely wheelchair-dependent or bed-bound were considered nonambulatory.

RESULTS

Pre-operatively, 83.1% of BKA patients were ambulatory, significantly more so than those undergoing AKA (44.9%, P < 0.0001). At 6-month follow-up these percentages dropped to 58.0% and 25.2%, respectively, for all patients. For patients who were ambulatory pre-operatively, 182/246 (73.9%) of BKA and 32/51 (62.7%) of AKA remained so post-amputation. Of those patients with both 6-month and greater than 1-year follow-up, there was no change in ambulatory status between the 2 time periods. On multivariable logistic regression, age greater than 70 years and female sex were associated with nonambulation post-operatively (P = 0.001, P = 0.015, respectively). None of the co-morbid conditions recorded (diabetes, renal insufficiency, end-stage renal disease, peripheral vascular disease, or body mass index > 35) was found to have a statistically significant correlation with post-operative ambulation using multivariable analysis.

CONCLUSIONS

The majority of ambulatory patients undergoing a major amputation were able to remain ambulatory. Patients who failed to ambulate 6 months after their amputation, failed to resume ambulating. Age greater than 70 and female sex were found to have a statistically significant association with becoming nonambulatory following surgery.