Access-related Hand Ischemia Research Articles

Contemporary outcomes of distal radial artery ligation for access related hand ischemia.

Access related hand ischemia (ARHI) is a rare albeit morbid complication of hemodialysis access creation. Distal radial artery ligation (DRAL) has been described as a strategy to improve perfusion to the hand while maintaining the access. The objective of this study was to report longitudinal outcomes of DRAL for ARHI. Retrospective cohort study (2015-2021) of all patients who underwent DRAL for ARHI at a tertiary care vascular center. Subjects were identified using the Mass General Brigham clinical data warehouse and data collection was supplemented with chart adjudication. Outcomes captured included 30-day complications and improvement in ARHI-related symptoms at 1 year. Thirty-one patients were included. Mean (SD) age was 59.9 (14.5) and 67.7% were male. Wrist radial-cephalic (74.2%) and proximal radial-cephalic (9.7%) configurations were most common. ARHI severity was: 9.7% stage 1 (retrograde flow without symptoms); 38.7% stage 2 (pain during exercise or dialysis); 41.9% stage 3 (pain at rest); and 9.7% stage 4 (tissue loss). High flow was present in 35.5% of patients at baseline with median (IQR) flow of 1670 ml/min (1478-1954). After DRAL, median (IQR) flow reduction in the high flow group was 953 ml/min (645-993); concurrent precision banding was performed in 29% to reduce flow. The 30-day risk of complication was 3.2% (n = 1 access thrombosis). During follow-up, 82.1% showed improvement in symptoms and 3.6% of patients needed an additional procedure for ARHI. Carpal tunnel surgery was required for improvement in 7.1% of patients and was suspected as the culprit of symptoms in 7.1%. Distal radial artery ligation for ARHI is safe and can improve ischemic symptoms in most patients while salvaging access function. Precision banding can serve as a useful adjunct in high flow accesses. Carpal tunnel syndrome should be considered as part of the differential diagnosis of hand pain in this population.

Contemporary Outcomes of Distal Radial Artery Ligation for Access-related Hand Ischemia

Access-related hand ischemia (ARHI) is a rare albeit morbid complication of hemodialysis access creation. Distal radial artery ligation (DRAL) has been described as a potential strategy to improve perfusion to the hand while maintaining the access. However, data for the safety and efficacy of this technique are limited to small case reports with limited follow-up. The objective of this study was to report longitudinal outcomes of distal radial artery ligation for ARHI in a contemporary cohort. We performed a retrospective cohort study (2015-2021) of all patients who underwent DRAL for ARHI or high flow at a tertiary care vascular center. Patients were identified using the Mass General Brigham clinical data registry and data collection was supplemented with chart adjudication. Outcomes captured included 30-day complications, and 1-year rates of improvement in ARHI-related symptoms. The cohort consisted of 31 patients. Mean age was 59.9 ± 14.5 years and 67.7% were male. Median follow-up was 335 days (interquartile range [IQR], 285-360 days). Wrist radial-cephalic (74.2%) and proximal radial-cephalic (9.7%) configurations were the most common. At baseline, ARHI severity was as follows: 38.7% stage 2 (pain during exercise or dialysis); 41.9% stage 3 (pain at rest); and 9.7% stage 4 (tissue loss). High flow was present in 35.5% of patients at baseline with median flow of 1670 mL/min (IQR, 1478-1954mL/min). After DRAL, median flow reduction in the high-flow group was 953 mL/min(IQR, 645-993mL/min) (Table); concurrent precision banding was performed in 29%. The 30-day complication rate after distal radial artery ligation was 3.2% (n = 1 access thrombosis). During longitudinal follow-up, 75% showed improvement in symptoms and 10.7% patients needed an additional procedure for ARHI. Carpal tunnel surgery was required for improvement in 7.1% of patients and was suspected as the culprit of symptoms in an additional 7.1% (Figure). Distal radial artery ligation for access related hand ischemia and or high flow is safe and can improve ischemic symptoms in most patients while salvaging access function. Carpal tunnel syndrome can explain access-related hand symptoms in approximately 15% of patients, and should be considered as a differential diagnosis in the assessment of this challenging patient population.TableIntraoperative details and postoperative outcomes after distal radial artery ligation (DRAL)CharacteristicTotal N (%) (n = 31)Concurrent procedure performed Banding9 (29.0) Side branch ligation7 (22.6) Angioplasty1 (3.2) Aneurysmorrhaphy2 (6.5)Follow-up, days333 (285-360)Flow reduction in high-flow group (mL/min) (n = 8)953 (645-993)30-Day complications Infection0 (0) Bleeding0 (0) Fistula thrombosis1 (3.2) Tissue loss healed if present (n = 3)2 (66.6)ARHI, Access-related hand ischemia.Data reported as counts (percentages) or median interquartile range. Open table in a new tab

Skin perfusion pressure for predicting access-related hand ischemia following arteriovenous fistula surgery based on the brachial artery.

Access-related hand ischemia (ARHI) is a major complication of arteriovenous fistula (AVF). This study aimed to assess the predictive efficacy of skin perfusion pressure (SPP) measurement for ARHI by examining the relationship between SPP and ARHI development and progression after AVF surgery. Twenty-five patients (16 men and 9 women) who underwent AVF surgery based on the brachial artery between January 2018 and December 2018 were included. The pre- and postoperative SPP values were measured on the day of surgery. ARHI occurrence and severity were measured within 3 days and at 6 months after surgery. Receiver operating characteristic curve analysis was used to evaluate the prediction model of ARHI, and the cutoff points for the calculated coefficients were determined. There was a significant correlation between the occurrence of immediate ARHI and the SPP gradient (p = 0.024). An SPP gradient value >50 mmHg had sensitivity and specificity values of 53.85% and 91.67%, respectively, in predicting the occurrence of immediate ARHI. A postoperative SPP <48 mmHg was significantly correlated with the occurrence of 6-month ARHI (p = 0.005), with sensitivity and specificity values of 71.43% and 83.33%, respectively. The SPP gradient and postoperative SPP values may be effective clinical predictors of ARHI occurring immediately and 6 months after surgery, respectively, with high specificity. These findings could allow clinicians to diagnose and begin early interventions to help prevent ischemic tissue damage in hemodialysis patients following AVF surgery.

Access-related hand ischemia and the Hemodialysis Fistula Maturation Study

Access-related hand ischemia (ARHI) is a major complication after hemodialysis access construction. This study was designed to prospectively describe its incidence, predictors, interventions, and associated access maturation. The Hemodialysis Fistula Maturation Study is a multicenter prospective cohort study designed to identify predictors of autogenous arteriovenous access (arteriovenous fistula [AVF]) maturation. Symptoms and interventions for ARHI were documented, and participants who received interventions for ARHI were compared with other participants using a nested case-control design. Associations of ARHI with clinical, ultrasound, vascular function, and vein histologic variables were each individually evaluated using conditional logistic regression; the association with maturation was assessed by relative risk, Pearson χ(2) test, and multiple logistic regression. The study cohort included 602 participants with median follow-up of 2.1years (10th-90th percentiles, 0.7-3.5years). Mean age was 55.1± 13.4 (standard deviation) years; the majority were male (70%), white (47%), diabetic (59%), smokers (55%), and on dialysis (64%) and underwent an upper arm AVF (76%). Symptoms of ARHI occurred in 45 (7%) participants, and intervention was required in 26 (4%). Interventions included distal revascularization with interval ligation (13), ligation (7), banding (4), revision using distal inflow (1), and proximalization of arterial inflow (1). Interventions were performed ≤7days after AVF creation in 4 participants (15%), between 8 and 30days in 6 (23%), and >30days in 16 (63%). Female gender (odds ratio, 3.17; 95% confidence interval, 1.27-7.91; P= .013), diabetes (13.62 [1.81-102.4]; P= .011), coronary artery disease (2.60 [1.03-6.58]; P= .044), higher preoperative venous capacitance (per %/10mm Hg, 2.76 [1.07-6.52]; P= .021), and maximum venous outflow slope (per [mL/100mL/min]/10mm Hg, 1.13 [1.03-1.25]; P= .011) were significantly associated with interventions; a lower carotid-femoral pulse wave velocity and the outflow vein diameter in the early postoperative period (days 0-3) approached significance (P< .10). Intervention for ARHI was not associated with AVF maturation failure (unadjusted risk ratio, 1.18 [0.69-2.04], P=.56; adjusted odds ratio, 0.97 [0.41-2.31], P= .95). Remedial intervention for ARHI after AVF construction is uncommon. Diabetes, female gender, capacitant outflow veins, and coronary artery disease are all associated with an increased risk of intervention. These higher risk patients should be counseled preoperatively, their operative plans should be designed to reduce the risk of hand ischemia, and they should be observed closely.

A comparison of revision using distal inflow and distal revascularization-interval ligation for the management of severe access-related hand ischemia

Access-related hand ischemia (ARHI) is a potentially limb-threatening complication of arteriovenous access for dialysis. The distal revascularization-interval ligation (DRIL) and revision using distal inflow (RUDI) procedures both allow treatment of ischemic symptoms while maintaining fistula patency. Although outcomes with the DRIL are well established, experience with the RUDI for ARHI remains preliminary. We compared outcomes in these procedures with respect to cumulative patency, resolution of symptoms, and patient survival. A large, prospectively maintained database was used to identify all patients after autogenous arteriovenous fistula construction at two hospitals between 2005 and 2015. Patients with severe Society for Vascular Surgery grade 3 ARHI were included for analysis. A total of 2035 autogenous accesses were created during the study period, and 58 (3%) developed grade 3 ARHI. Of this cohort, RUDI was performed in 20 and DRIL in 21. The indication for intervention was tissue loss (61%) or ischemic rest pain (39%). Mean age was 57.5years, and 54% of patients were female. Most patients had diabetes (86%) and symptomatic peripheral arterial disease (63%). The mean preoperative digital-brachial index was 0.25± 0.12. There were no preoperative differences in patient comorbidities between the RUDI and DRIL cohorts. Primary patency between the RUDI and DRIL cohorts at 12months (58%± 11% vs 55%± 12%) and 36months (51%± 12% vs 41%± 12%) were similar (P= .841). Cumulative secondary patency at 12months (84%± 8% vs 94%± 6%) and 36months (78%± 9% vs 86%± 9%) showed no significant difference (P= .398). Resolution of ischemic symptoms, including resolution or improvement in pain or healing ofischemic ulcers or amputations, occurred in 90% with RUDI and in 81% with DRIL (P= .131). Survival for patients who underwent RUDI or DRIL procedures at 1 and 3years was 85% vs 86% (P= .948) and 55% vs 49% (P= .278). In this preliminary study, the RUDI demonstrated similar patency, symptom resolution, and survival compared with the DRIL for patients with severe ARHI. All-cause mortality after any procedure for severe steal syndrome is high, and the particular intervention for management of steal must account for anatomic-, patient-, and disease-related considerations.

A Comparison of RUDI and DRIL for the Management of Severe Access-Related Hand Ischemia

A Comparison of RUDI and DRIL for the Management of Severe Access-Related Hand Ischemia

Digital pressure and oxygen saturation measurements in the diagnosis of chronic hemodialysis access-induced distal ischemia

Hemodialysis access-induced distal ischemia (HAIDI) can be classified as acute (on the first postoperative day), subacute (≤1 month), or chronic (>1 month), based on the time of onset after access creation. The diagnosis is mainly clinical. However, performing additional tests is beneficial in further assessment of patients. The purpose of this study was to evaluate the use of finger pressure and oxygen saturation measurements for the diagnosis of chronic HAIDI. A total of 20 patients with chronic HAIDI (cases) and 40 asymptomatic hemodialysis patients (controls) were matched for age, sex, etiology of end-stage renal disease, and type of arteriovenous access. Basal digital pressure (BDP), digital pressure during manual compression of access, digital brachial index (DBI), change in digital pressure with access compression (CDP), digital pressure of the contralateral side, and bilateral oxygen saturation (O2 Sat) were measured in all patients. In the case group, compression of the arteriovenous fistula (AVF) increased mean BDP from 61 ± 26 to 118 ± 28 mm Hg (P < .001), which failed to reach the non-AVF side mean digital pressure of 151 ± 25 mm Hg (P < .001). In addition, O2 Sat of the AVF side was significantly lower than the contralateral side (92.9% ± 2.1% vs 95.6% ± 1.4%; P = .001). Among the controls, manual AVF compression raised the mean BDP from 114 ± 36 mm Hg to 133 ± 29 mm Hg (P < .001), which was still significantly lower than the contralateral side mean digital pressure of 141 ± 30 mm Hg (P = .002). In addition, O2 Sat values of the two sides were different (96.7% ± 2.1% vs 97.1% ± 1.9%; P = .01). Comparing the cases and controls, the mean BDP (61 ± 26 mm Hg vs 114 ± 36 mm Hg; P < .001), DBI (0.44 ± 0.16 vs 0.82 ± 0.19; P < .001), and O2 Sat (92.9% ± 2.1% vs 96.7% ± 2.1%; P < .001) were significantly lower and CDP (57 ± 24 mm Hg vs 19 ± 17 mm Hg; P < .001) was significantly higher in the cases than in the controls. The optimal discriminatory thresholds of 80 mm Hg for BDP, 0.7 for DBI, 40 mm Hg for CDP, and 94% for O2 Sat were determined. Digital pressure and O2 Sat measurements are useful additional methods to assist in the clinical evaluation of hemodialysis patients with access-related hand ischemia. BDP <80 mm Hg, DBI <0.7, CDP >40 mm Hg, and O2 Sat <94% are associated with chronic HAIDI.

Far Infrared Therapy as a Novel Treatment for Hand Ischemia Following Arteriovenous Graft for Hemodialysis

Introduction Hand ischemia following vascular access surgery is an uncommon complication. A clinical dilemma exists between prioritizing the preservation of vascular access and the need for surgical intervention to rescue the ischemic hand. Report An 80 year old man who had hand ischemia following creation of a polytetrafluoroethylene arteriovenous graft with clinical evidence of ischemic pain of the left hand and Doppler ultrasound evidence of diastolic flow reversal is described. Far infrared therapy (FIR) was applied over the distal part of the affected limb, and the symptoms and signs of ischemia improved remarkably. Follow up ultrasonography also revealed the disappearance of diastolic flow reversal. Discussion FIR therapy is a promising and non-invasive therapeutic modality to treat vascular access related hand ischemia by decreasing vascular resistance and improving hand perfusion

Prevention of vascular access hand ischemia using the axillary artery as inflow

Avoiding dialysis access-associated ischemic steal syndrome (DASS) in patients with upper extremity peripheral vascular occlusive disease while creating a functional hemodialysis vascular access may be challenging. We constructed an autogenous access with primary proximalization of the arterial inflow to prevent hand ischemia in patients at high risk for this complication. Patients requiring hemodialysis access with physical findings suggesting a high risk of access-related hand ischemia (absent radial, ulnar, and brachial palpable pulses associated with small calcified vessels by ultrasound examination) underwent a primary arteriovenous fistula transposition procedure utilizing the axillary artery for inflow. The arteriovenous fistula was either a reversed flow basilic vein transposition supplemented by valvulotomy (n = 22); a translocated reversed basilic vein (n = 4); a cephalic vein harvested into the forearm and placed in a loop configuration for axillary artery inflow (n = 3); or a translocated reversed saphenous vein (n = 1). Thirty patients with a mean age of 60 years (range, 31-83 years) underwent successful primary axillary artery inflow procedures during a 3-year period. Of these, 23 (77%) were female and 25 (83%) were diabetic. Twenty-one (70%) had previous vascular access procedures and 10 (33%) were obese. No patient developed postoperative ischemia. Three individuals died 2, 14, and 19 months following surgery, none related to vascular access. Three accesses failed after 1, 5, and 7 months and could not be salvaged. Life-table primary, primary assisted, and cumulative patency rates were 57%, 78%, and 87% respectively at 1 year with a mean follow-up of 7 months (range, 1-25 months). Cephalic vein outflow was associated with fewer access failures, fewer interventions postoperatively, and lower rates of arm swelling (P < .01). Creating a basilic vein transposition for vascular access utilizing axillary artery inflow is a good option for patients with severe peripheral vascular disease. It offers a high patency rate and the prevention of DASS. Retrograde basilic vein outflow through the median cubital and cephalic vein is associated with the best outcome and is the recommended configuration.

Prediction of graft patency and mortality after distal revascularization and interval ligation for hemodialysis access-related hand ischemia

The treatment goals of access-related hand ischemia (ARHI) are to reverse symptoms and salvage the access. Many procedures have been described, but the optimal treatment strategy remains unresolved. In an effort to guide clinical decision making, this study was undertaken to document our outcomes for distal revascularization and interval ligation (DRIL) and to identify predictors of bypass patency and patient mortality. A retrospective review was performed of all patients who underwent DRIL at the University of Florida from 2002 to 2011. Diagnosis of ARHI was based primarily upon clinical symptoms with noninvasive studies used to corroborate in equivocal cases. Patient demographics, procedure-outcome variables, and reinterventions were recorded. Bypass patency and mortality were estimated using cumulative incidence and Kaplan-Meier methodology, respectively. Cumulative incidence and Cox regression analysis were performed to determine predictors of bypass patency and mortality, respectively. A total of 134 DRILs were performed in 126 patients (mean [standard deviation] age, 57 [12] years) following brachial artery-based access. The postoperative complication rate was 27% (19% wound), and 30-day mortality was 2%. The wrist-brachial index and digital brachial index increased 0.31 (0.25) and 0.25 (0.29), respectively. Symptoms resolved in 82% of patients, and 85% continued to use their access. Cumulative incidences (± standard error of the mean) of loss of primary and primary-assisted patency rates were 5%± 2% and 4%± 2% at 1 year and 22%± 5% and 18%± 5% at 5 years, respectively, with mean follow-up of 14.8 months. Univariate predictors of primary patency failure were DRIL complications (odds ratio [OR], 3.3; 95% confidence interval [CI], 1.2-8.9; P= .02), configuration other than brachiobasilic/brachiocephalic autogenous access (OR, 3.4; 95% CI, 1.4-8.3; P= .009), and two or more prior access attempts (OR, 4.1; 95% CI, 1.6-10.4; P= .004). Brachiocephalic access configuration (OR, 0.2; 95% CI, 0.04-0.8; P=.02) and autogenous vein conduit (OR, 0.2; 95% CI, 0.06-0.58; P= .004) were predictors of improved bypass patency. All-cause mortality was 28% and 79% at 1 and 5 years, respectively. Multivariable predictors of mortality were age >40 (hazard ratio [HR], 8.3; 95% CI, 2.5-33.3; P= .0004), grade 3 ischemia (HR, 2.6; 95% CI, 1.5-4.6; P= .0008), complication from DRIL (HR, 2.4; 95% CI, 1.3-4.5; P= .004), and smoking history (HR, 2.2; 95% CI, 1.3-4; P=.007). Patients with no prior access attempts had lower predicted mortality (HR, 0.5; 95% CI, 0.3-0.9; P= .02). The DRIL procedure effectively improves distal perfusion and reverses the symptoms of ARHI while salvaging the access, but the long-term survival of these patients is poor. Given the poor survival, preoperative risk stratification is critical. Patients at high risk for DRIL failure and mortality may be best served with alternate remedial procedures.

Prediction of Graft Patency and Mortality After Distal Revascularization and Interval Ligation for Hemodialysis Access-Related Hand Ischemia

The goals for management of access-related hand ischemia (ARHI) are to reverse symptoms and salvage the access. Many procedures have been described, but the optimal treatment remains unresolved. In an effort to guide clinical decision making, this study was undertaken to document our outcomes for distal revascularization and interval ligation (DRIL) and identify predictors of bypass patency and patient mortality. A retrospective review was performed of all patients who underwent DRIL (1997-2010). Bypass patency and mortality were determined using life-table analysis, and predictors were determined using univariate and multivariate analyses. A total of 132 DRILs were performed in 126 patients (59% female, 69% diabetic; mean ± SD age, 57 ± 12 years) after brachial artery-based access with a 27% (19% wound) morbidity and a 2% 30-day mortality. Mean follow-up was 15 months. The wrist/brachial and digital/brachial indices increased 0.31 ± 0.25 and 0.25 ± 0.29, respectively. Symptoms resolved in 82% of patients, and 85% were able to continue using their access. Primary and primary-assisted patency was 77% and 79% at 1 year and 68%, 70% at 5 years. Univariate predictors of patency failure were cryopreserved conduit, pre-operative ASA + Coumadin use, a nonbrachial basilic/cephalic access configuration, and two or more prior access attempts. Preoperative statin therapy, saphenous vein conduit, and brachiocephalic access were predictors of improved bypass patency (Table). Mortality was 28% at 1 year and 79% at 5 years. Multivariate predictors of mortality were composite conduit, complication from DRIL, and an indication of grade 3 ischemia. DRIL effectively improves distal perfusion and reverses the symptoms of ARHI while salvaging the access. However, given the high mortality of this patient population, preoperative risk stratification is critical for optimal utilization of this remedial strategy.

Treatment Strategies for Access-Related Hand Ischemia

Access-related hand ischemia, commonly known as "steal syndrome," is one of the most challenging and worrisome complications for the access surgeon. The construction of an arteriovenous access results in a predictable decrease in the perfusion pressure distal to the anastomosis, which can result in ischemia if the compensatory mechanisms are inadequate. Several preoperative clinical features have been shown to identify patients at risk. The diagnosis of access-related hand ischemia is largely a clinical one that can be aided in equivocal cases with noninvasive vascular laboratory studies. The treatment goals are to reverse the hand ischemia and to preserve the access. There are a variety of different remedial treatments, including access ligation, correction of the inflow lesion, limiting the flow through the access, proximalization of arterial inflow, revision using distal inflow, and distal revascularization with interval ligation. The optimal choice is predicated on the timing and severity of symptoms in conjunction with the access type, its anticipated durability, patient comorbidities, distribution of occlusive disease, and availability of venous conduit. The distal revascularization with interval ligation procedure has emerged as our optimal treatment and reverses the ischemic symptoms and salvages the access in approximately 90% of the cases. It is incumbent on all access surgeons to be familiar with the management of access-related hand ischemia. A review of the underlying pathophysiology and treatment options will be provided along with our current treatment algorithm.

Midterm outcome after the distal revascularization and interval ligation (DRIL) procedure

The distal revascularization and interval ligation (DRIL) procedure has evolved as the optimal treatment for access-related hand ischemia despite concerns about its durability. This study was designed to review our institutional experience and objectively define its mid-term outcome. A retrospective review of all patients undergoing the DRIL procedure was performed. The diagnosis of severe hand ischemia was made based primarily upon clinical presentation, but confirmed with noninvasive imaging in select cases. The DRIL conduit was selected based upon noninvasive imaging (vein conduit criteria: saphenous > arm; diameter >/=3 mm) and the proximal anastomosis was positioned >/=7 cm from the access anastomosis. The DRIL bypasses were followed in a graft surveillance protocol and remedial procedures performed as dictated by clinical or ultrasound scan findings. Sixty-four DRIL procedures were performed in 61 patients (age - 58 +/- 13 standard deviation [SD], female - 62%, diabetic - 72%). The index access procedures included: autogenous brachiocephalic - 46%, autogenous brachiobasilic - 31%, autogenous brachioaxillary translocated femoral vein - 20%, other -3%. The precipitating symptoms were pain (25%), paresthesia (34%), motor dysfunction (24%), and tissue loss (17%); a pre-emptive DRIL was performed in 5 patients. The timing of the DRIL relative to the index access was dictated by the symptoms: <24 hrs - 19%; 1 day </= DRIL </=7 days - 29%; 7 days </= DRIL </=30 days - 8%; >30 days - 44%. Perioperative mortality rate was 3% and the complication rate was 22% (wound - 14%). The DRIL procedure relieved the ischemic symptoms in 78% of the cases (residual symptoms: paresthesia - 13%; pain - 5%; tissue loss - 4%; motor - 2%). The DRIL also resulted in significant (P < .05) increases in both the wrist/brachial index (WBI) and digital/brachial index (DBI) with the mean increases of 0.34 +/- 0.26 and 0.41 +/- 0.21, respectively. The primary DRIL patency rates (+/- standard error of the mean [SEM]) were 77 +/- 8%, 74 +/- 9%, and 71 +/- 9% at 1 year, 3 years, and 5 years, respectively, while the corresponding secondary patency rates were 81 +/- 7%, 76 +/- 9%, and 76 +/- 9%, and the survival rates were 71 +/- 6%, 59 +/- 7%, and 33 +/- 9%. The index access procedure went on to mature sufficiently for cannulation in 68% of the cases when the DRIL was performed early (ie, <3 months from index access); all accesses functional at the time of the DRIL were used for dialysis throughout the perioperative period. The DRIL procedure safely and effectively relieves the symptoms of severe access-related hand ischemia while preserving the access. The midterm results suggest that the DRIL bypasses are durable, although long-term graft surveillance may be justified given the observed failures.