Distribution of Flow in an Arteriovenous Fistula Using Reduced-Order Models.

The creation of a communication between an artery and a vein (arteriovenous fistula or AVF), to speed up the blood purification during hemodialysis of patients with renal insufficiency, induces significant rheological and mechanical modifications of the vascular network. In this study, we investigated the impact of the creation of an AVF with a zero-dimensional network model of the vascular system of an upper limb and a one-dimensional model around the anastomosis. We compared the simulated distribution of flow rate in this vascular system with Doppler ultrasound measurements. We studied three configurations: before the creation of the AVF, after the creation of the AVF, and after a focal reduction due to a hyper flow rate. The zero-dimensional model predicted the bounds of the diameter of the superficial vein that respects the flow constraints, assuming a high capillary resistance. We indeed highlighted the importance of knowing the capillary resistance as it is a decisive parameter in the models. We also found that the model reproduced the Doppler measurements of flow rate in every configuration and predicted the distribution of flow in cases where the Doppler was not available. The one-dimensional model allowed studying the impact of a venous constriction on the flow distribution, and the capillary resistance was still a crucial parameter.

Elective extra corporeal membrane oxygenation for high-risk rigid bronchoscopy.

The use of extracorporeal membrane oxygenation for high-risk rigid bronchoscopy has been reported in few urgent cases. We report our experience with this approach which was planned electively in five cases on 202 procedures (2.5%). It was proposed because of the potential inability to ventilate the lungs using conventional techniques due to extensive tracheobronchial lesions or the risk of major intraoperative bleeding related to disease characteristics. There were no intraoperative complications and postoperative course was favourable in all patients. With a maximum follow-up of 3 years and 7 months, all patients are alive with no tracheostomy despite major morbidities.

Preliminary experimental study of a mechanical connector allowing vascular anastomosis.

BACKGROUND: Aortic clamping time needed to carry out anastomosis during aortic surgery is one of the major predictive factors of morbidity/mortality. Because of the difficulties inherent in this technique, the duration of aortic clamping can be increased significantly with laparoscopy, which may explain why this kind of surgery is not often undertaken. We designed an original connector that will help us perform automated end-to-end vascular anastomoses. This anastomotic device was tested on a cadaver, test benches, and finally on pigs. METHODS: The connector consists of a bare-metal stent with spikes covering its outer surface. Once the prosthesis has been introduced into the arterial lumen over a 15-mm length, the connector is placed into the prosthesis; then, upon inflating a balloon and employing stent spikes, the prosthesis can be anchored in the artery. A feasibility study was carried out, first on cadaveric arteries and then on bench tests. In vivo, using this connector, the infrarenal aorta of 7 pigs was replaced with a 6-8-mm-diameter prosthesis. One to 42 days after implantation, angiography was performed before explanting the prosthesis. Evaluation criteria included anastomosis performance time, leakproofing capacity, tensile strength, patency, and histologic changes induced by the device. RESULTS: On the cadavers, manual traction tests showed that the anastomoses were satisfactory. Median force needed to rupture an automated anastomosis was 15.85 N. No leakage was seen under a systolic/diastolic pressure of up to 250/180 mm Hg. All pigs benefited from automated anastomosis. Once the designed device had been assessed, the median connection time was 2 minutes. In 4 cases, aortic thrombosis was found, 1 of which was septic. The implanting ancillary was responsible for 2 posterior aortic wall perforations, which extended the clamping time; therefore, this device should be modified. Anastomosis patency and tensile strength tests were satisfactory. Histologic results showed the connector incorporation, integration of the spikes in the arterial wall, and the absence of inflammation in the aortic wall. CONCLUSIONS: These preliminary studies confirm that the connector is quick and reliable for performing in vivo arterioprosthetic anastomoses. Further studies are needed to improve the ancillary device, which will enable its use it in laparoscopic and conventional surgery.

Open repair of vertebral artery: a 7-year single-center report.

BACKGROUND: To report the long-term results of proximal and distal VA open repairs. METHODS: From January 2002 to December 2009, 74 cases of VA open repair were performed (73 patients, 41 men; mean age, 66.5 ± 15.2 years). Symptoms of vertebrobasilar insufficiency were present in 61 cases (82.4%). Forty-seven have had a proximal VA repair, and 27, a distal one. Bypass grafting using a saphenous vein graft was performed in 21 cases (28.3%). Direct transposition was used in 48 (64.8%), mostly into the common carotid artery. RESULTS: Mean duration of follow-up was 39.5 ± 31.3 months. A stroke was present in three patients (4.1%), two hemispheric (2.7%) and one vertebrobasilar (1.3%), which turned lethal. The two hemispheric strokes occurred in the subgroup of 35 procedures combined with a carotid artery reconstruction. A transient Horner syndrome was found in 16 cases (21.6%), and a transient vocal palsy, in six (8.1%). Early postoperative occlusion occurred in two cases (2.7%). A total of seven (9.4%) patients died during follow-up, one from a stroke. Cumulative Kaplan-Meier survival rate was 90.7 ± 4.8% at 3 years and 77.3 ± 12.2% at 6 years. Assessment of late patency was obtained in 54 (84.3%) of 64 survivals by duplex scanning (70.3%) or angiography (10.9%). Significant vertebrobasilar symptom-free rate was 87.7 ± 9.2% at 6 years. Primary patency rate was 94.8 ± 3.8% at 3 years and 90.8 ± 9.4% at 6 years. CONCLUSIONS: VA open repair provides excellent long-term results. Patients with combined carotid and VA reconstruction are at higher risk of postoperative stroke than patients undergoing isolated repair of the VA.

Experimental study of a novel mechanical connector for sutureless open arterial anastomosis.

OBJECTIVES: This study assessed the feasibility and efficacy of a new sutureless connector for end-to-end arterial anastomosis. METHODS: The anastomotic device is a connector consisting of a bare-metal stent with spikes covering its outer surface, which is introduced through the prosthesis. The seal of the anastomosis is obtained by inflating a balloon anchoring the stent with the spikes in the prosthesis and in the receiving artery. This experiment was conducted in three phases: (1) A feasibility study was done on four cadaveric femoral arteries using a polytetrafluoroethylene prosthesis, with measurement of the penetration of the spikes into the layers of the arterial wall. (2) Bench tests were conducted in seven automated and in seven sutured anastomoses. Anastomosis sealing was tested using a pump system (≤250 mm Hg) in a water-filled closed circuit. (3) The infrarenal aorta of seven pigs was replaced with a 6- to 8-mm diameter prosthesis, using this automated device for the proximal anastomosis. The distal anastomosis was handsewn on the aortic bifurcation. After completion angiography, animals were euthanized for macroscopic and histologic studies of the aorta, connector, and prosthesis. Explantations were done immediately (2 pigs), and at 15 (2 pigs), at 30 (2 pigs), and 42 days (1 pig). Study end points were the automated anastomosis time compared with manual suturing, leakage, mechanical strength, and patency of the anastomosis together with the histologic changes of the aortic wall in contact with the spiked stent. RESULTS: Tests performed on four cadaveric arteries showed complete penetration of the spikes into the arterial wall layers without metal fracture. Tests of traction showed that the median force needed to rupture the automated anastomosis was 18.3 N (interquartile range [IQR], 17.7-19.9 N), with no significant difference from the handmade anastomosis (19.5 N; IQR, 17.9-20.2 N, P = .33). No leakage was demonstrated in vitro with a pulsatile flow and a pressure up to 250 mm Hg. The median automated anastomosis time on pig aorta was 2.4 minutes (IQR, 1.4-3.3 min) vs 17.0 minutes (IQR, 15.1-17.2 minutes) for the handmade aortic anastomosis performed on the same animals (P = .002). There was no anastomotic leak. Histology showed incorporation of the connector spikes in the aortic wall, without intimal hyperplasia or false aneurysm. CONCLUSIONS: This preliminary study confirms the feasibility of this sutureless system, suggesting its usefulness for a faster and simpler anastomosis in hybrid arterial surgery.