Henry Baele

Infrainguinal bypass in patients with end-stage renal disease

BACKGROUND This study was undertaken to evaluate the outcome of infrainguinal arterial reconstruction in a high-risk subset of patients with end-stage renal disease. METHODS We reviewed the medical records of 44 patients requiring maintenance dialysis and undergoing 57 infrainguinal bypass procedures for limb salvage from 1986 to 1992. These included 16 (28%) femoropopliteal and 41 (72%) tibial or pedal bypasses with autogenous (82%), prosthetic (12%), or composite (6%) graft materials. The principal indications for operation were ischemic ulceration or gangrene (79%) and rest pain (21%). Angiographic evaluation most frequently showed single-vessel runoff (56%). Risk factors included age (mean, 63 years), diabetes (75%), hypertension (93%), coronary artery disease (52%), smoking (39%), previous myocardial infarction (20%), and contralateral amputation (18%). Infection was present in 22 limbs (39%). RESULTS Early (30-day) surgical morbidity rate was 39%, including wound breakdown (19%), graft thrombosis (9%), and major amputation (4%). Perioperative mortality rate was 9%. Cumulative primary graft patency rates were 71% and 63%, secondary patency rates were 80% and 66%, and limb salvage rates were 70% and 52% at 1 and 2 years, respectively. Limb loss correlated most highly with the presence of preoperative infection (p = 0.036; log-rank method). Patient survival rate was 52% at 2 years. CONCLUSIONS Life-table analysis confirms a poor life expectancy for this population but indicates that an acceptable level of limb salvage may be achieved with arterial reconstruction in properly selected patients.

Popliteal-to-distal bypass for limb-threatening ischemia

In a subset of patients requiring lower extremity revascularization, the popliteal artery may be used for inflow, thereby minimizing dissection and the length of vein required for bypass. This retrospective study was done to define the risks and benefits of arterial reconstruction in a population of patients having popliteal-to-distal bypass procedures. Between 1986 and 1990, 32 surgical procedures were performed on 29 patients. The patients ages ranged from 46 to 86 years, with a mean age of 68 years. Twenty-four of 29 (83%) were men and 19 of the 29 (66%) had diabetes. Most patients had multiple indications for surgical intervention, and these included rest pain (54%), nonhealing ulcers (64%), and gangrene (29%). Arterial bypass with use of the popliteal artery for the proximal anastomosis was performed with in situ saphenous vein (50%), reversed saphenous vein (41%), and orthograde autologous vein (9%). Distal anastomoses were to the posterior tibial artery in 11 bypasses (33%), the peroneal artery in 10 (30%), the anterior tibial artery in two (6%), and the dorsal pedal artery in 10 (30%). Two deaths occurred in the perioperative period for an operative mortality rate of 6.9%. With use of life-table analysis, the cumulative graft patency rate was 97% at 1 year, 97% at 2 years, and 63.5% at 4 years. The overall cumulative limb salvage rate was 90.1% at 1 year, 90.1% at 2 years, and 78.8% at 4 years.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparative occupational radiation exposure between fixed and mobile imaging systems.

OBJECTIVE Endovascular intervention exposes surgical staff to scattered radiation, which varies according to procedure and imaging equipment. The purpose of this study was to determine differences in occupational exposure between procedures performed with fixed imaging (FI) in an endovascular suite compared with conventional mobile imaging (MI) in a standard operating room. METHODS A series of 116 endovascular cases were performed over a 4-month interval in a dedicated endovascular suite with FI and conventional operating room with MI. All cases were performed at a single institution and radiation dose was recorded using real-time dosimetry badges from Unfors RaySafe (Hopkinton, Mass). A dosimeter was mounted in each room to establish a radiation baseline. Staff dose was recorded using individual badges worn on the torso lead. Total mean air kerma (Kar; mGy, patient dose) and mean case dose (mSv, scattered radiation) were compared between rooms and across all staff positions for cases of varying complexity. Statistical analyses for all continuous variables were performed using t test and analysis of variance where appropriate. RESULTS A total of 43 cases with MI and 73 cases with FI were performed by four vascular surgeons. Total mean Kar, and case dose were significantly higher with FI compared with MI. (mean ± standard error of the mean, 523 ± 49 mGy vs 98 ± 19 mGy; P < .00001; 0.77 ± 0.03 mSv vs 0.16 ± 0.08 mSv, P < .00001). Exposure for the primary surgeon and assistant was significantly higher with FI compared with MI. Mean exposure for all cases using either imaging modality, was significantly higher for the primary surgeon and assistant than for support staff (ie, nurse, radiology technologist) beyond 6 feet from the X-ray source, indicated according to one-way analysis of variance (MI: P < .00001; FI: P < .00001). Support staff exposure was negligible and did not differ between FI and MI. Room dose stratified according to case complexity (Kar) showed statistically significantly higher scattered radiation in FI vs MI across all quartiles. CONCLUSIONS The scattered radiation is several-fold higher with FI than MI across all levels of case complexity. Radiation exposure decreases with distance from the radiation source, and is negligible outside of a 6-foot radius. Modern endovascular suites allow high-fidelity imaging, yet additional strategies to minimize exposure and occupational risk are needed.

Effects of nifedipine on the hemodynamic response to clamping and declamping of the abdominal aorta in dogs.

Clamping and declamping of the infrarenal abdominal aorta may adversely affect cardiovascular function, particularly in the presence of heart disease. This effect may be further altered by drugs used in the treatment of symptomatic coronary artery disease. The effect of nifedipine on the hemodynamic response to aortic clamping and declamping was determined in 12 dogs anesthetized with 50% nitrous oxide and 0.6% end-tidal isoflurane and monitored with aortic, left ventricular (LV), and thermodilution pulmonary artery catheters. Six dogs received a nifedipine bolus of 100 micrograms/kg followed by an infusion of 4 micrograms/kg/min. Six dogs did not receive any nifedipine and served as controls. Before clamping, nifedipine produced immediate decreases in arterial pressure, systemic vascular resistance (SVR), and LV dP/dt, and a modest increase in cardiac output (CO). During aortic clamping, nifedipine-treated dogs demonstrated marked increases in heart rate (HR), dP/dt, and CO while maintaining a low SVR. There were no significant changes upon declamping. The nifedipine-treated animals maintained a high CO and low SVR. Thus, nifedipine greatly altered the hemodynamic responses to aortic clamping and declamping. Awareness of these alterations is important when caring for patients being treated with nifedipine who are undergoing aortic surgery.

Increased risk of renal dysfunction with percutaneous mechanical thrombectomy compared with catheter-directed thrombolysis

Objective: Percutaneous mechanical thrombectomy (PMT) is regularly used in the treatment of both venous and arterial thrombosis. Although there has been no formal report, PMT has been linked to cases of reversible postoperative acute kidney injury (AKI). The purpose of this study is to evaluate the risk of renal dysfunction in patients undergoing PMT vs catheter‐directed thrombolysis (CDT) for treatment of an acute thrombus. Methods: This study is a retrospective review of all patients in a single institution with a Current Procedural Terminology code for PMT or CDT from January 2009 through December 2014. Each patient was grouped into one of the four following procedural categories: PMT only, PMT with tissue plasminogen activator (tPA) pulse‐spray, PMT with CDT, or CDT only. Preoperative and postoperative creatinine and glomerular filtration rate (GFR) values were obtained for each patient. The RIFLE (Risk, Injury, Failure, Loss, and End‐stage renal disease) criteria were used to categorize the extent of renal dysfunction. χ2 analysis, one‐way analysis of variance, and unpaired t‐test were used to assess significance. Results: A total of 227 patients were reviewed, of which 82 were excluded due to either existence of preoperative AKI, history of end‐stage renal disease, or lack of clinical data. Of the remaining 145 patients, 53 (37%) presented with arterial thrombosis (mean age, 62 years; 43% male) and 92 (63%) presented with venous thrombosis (mean age, 48 years; 45% male). The incidence of renal dysfunction was highest in the PMT/tPA pulse group (21%), followed by the PMT group (20%) and the PMT/CDT group (14%). CDT was not associated with renal dysfunction. PMT (P = .046), and PMT/tPA pulse (P = .033) were associated with higher rates of renal dysfunction than the CDT controls. The average preoperative GFR for the 22 patients who developed AKI was 53.7 ± 9.4 mL/min/1.73 m2. The minimum postoperative GFR within 48 hours was an average of 35 ± 16 mL/min/1.73 m2. Stratified by the RIFLE criteria, 13 (9%) patients progressed to the risk category, 6 (4%) progressed to the injury category, and 3 (2%) progressed to the failure category. None of the patients who developed renal dysfunction from PMT progressed to dialysis within the same admission period. Conclusions: The use of PMT as a treatment for vascular thrombosis is associated with renal dysfunction. Patients treated with PMT require postoperative vigilance and renal protective measures.

Evaluating strategies for reducing scattered radiation in fixed-imaging hybrid operating suites

Objective: High‐resolution fixed C‐arm fluoroscopic systems allow high‐quality endovascular imaging but come at a cost of greater scatter radiation generation and increased occupational exposure for surgeons. The purpose of this study was to evaluate the efficacy of two methods in reducing scattered radiation exposure. Methods: There were 164 endovascular cases analyzed in three phases. In phase 1 (P1), baseline radiation exposure was calculated. In phase 2 (P2), staff used real‐time radiation dose monitoring (dosimetry badges [RaySafe; Unfors, Hopkinton, Mass]). In phase 3 (P3), a software imaging algorithm was installed that reduced radiation (EcoDose software; Philips Healthcare, Best, The Netherlands). Results: A total of 72 cases in P1, 34 cases in P2, and 58 cases in P3 were analyzed. Total mean dose‐area product decreased across each phase, with statistical significance achieved for P1 vs P3 (mean ± standard error of the mean, 186,173 ± 16,754 mGy/cm2 vs 121,536 ± 11,971 mGy/cm2; P = .002) and P2 vs P3 (171,921 ± 26,276 mGy/cm2 vs 121,536 ± 11,971 mGy/cm2; P = .04), whereas total mean fluoroscopy time did not significantly differ across any phase. The radiation exposure to the primary operator did not change significantly from P1 to P2 but fell significantly in P3 (0.08 ± 0.02 mSv vs 0.03 ± 0.01 mSv; P = .02). The addition of dose reduction software had the most impact on endovascular aneurysm repair, with reductions in median room dose (P = .03) and primary operator exposure (P2 vs P3; 0.19 ± 0.04 mSv vs 0.03 ± 0.02 mSv; P < .01). Conclusions: Dose reduction software may be an effective technique to lower radiation exposure. Implementation of system‐based strategies to reduce radiation is needed to reduce lifetime occupational radiation exposure for endovascular staff and to improve patient safety.

Characterizing tissue perfusion after lower extremity intervention using two-dimensional color-coded digital subtraction angiography

Objective Digital subtraction angiography (DSA) of the peripheral arterial vasculature provides lumenographic information but only a qualitative assessment of blood flow. The ability to quantify adequate tissue perfusion of the lower extremities would enable real‐time perfusion assessment during DSA of patients with peripheral arterial disease (PAD). In this study, we used a novel real‐time imaging software to delineate tissue perfusion parameters in the foot in PAD patients. Methods Between March 2015 and June 2016, patients (N = 31) underwent lower extremity angiography using a two‐dimensional perfusion (2DP) imaging protocol (Philips Healthcare, Andover, Mass). Of the 31 enrolled patients, 16 patients received preintervention and postintervention DSA images (18 angiograms), while contrast agent injection settings and the position of the foot, catheter, and C‐arm were kept constant. The region of interest for perfusion measurements was taken at the level of the medial malleolus. Perfusion parameters included arrival time (AT) of contrast material, wash‐in rate (WIR), time to peak (TTP) contrast intensity, and area under the curve (AUC). Results Patients (mean age, 67 years; male, 61%) undergoing 2DP had limbs classified as Rutherford class 3 (n = 9 limbs), class 4 (n = 11), and class 5 (n = 14) ischemia with a mean ankle‐brachial index of 0.63. For the whole cohort, median (interquartile range) AT measured 5.20 (3.10‐7.25) seconds; WIR, 61.95 (43.53‐86.43) signal intensity (SI)/s; TTP, 3.80 (2.88‐4.50) seconds; peak intensity, 725.00 (613.75‐1138.00) SI; and AUC, 12,084.00 (6742.80‐17,059.70) SI*s. A subset of patients had 2DP performed before and after intervention (n = 18 cases). A detectable improvement in SI and two‐dimensional flow parameters was seen after intervention. Average AT of contrast material to the region of interest shortened after intervention with percentage decrease of 30.1% ± 49.1%, corresponding decrease in TTP of 17.6% ± 24.7%, increase in WIR of 68.8% ± 94.2% and in AUC of 10.5% ± 37.6%, decrease in mean transit time of 18.7% ± 28.1%, and increase in peak of 34.4% ± 42.2%. Conclusions The 2DP imaging allows measurement of blood flow in real time as an adjunct to DSA. The AT may be the most sensitive marker of perfusion change in the lower extremity. Quantitative thresholds based on 2DP hold promise for immediate treatment effectiveness assessment in patients with PAD.