Monitoring of the Progression of the Perioperative Serum Lactate Concentration Improves the Accuracy of the Prediction of Acute Mesenteric Ischemia Development After Cardiovascular Surgery.

OBJECTIVES: To examine the sensitivity and specificity of perioperative lactate gradients for the prediction of subsequent acute mesenteric ischemia development in patients undergoing cardiovascular surgery. DESIGN: Retrospective, single-center, case-control study. SETTING: University hospital. PARTICIPANTS: The study comprised 108 (1.15%) patients with acute mesenteric ischemia who were selected from 9,385 patients who underwent cardiovascular surgery and were matched to 324 control patients by age and surgery type. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Univariate and logistic regression analyses were used to examine intraoperative and early postoperative lactate levels in patients with and without mesenteric ischemia after cardiac surgery. Late intraoperative lactate concentrations were significantly greater in patients who subsequently developed mesenteric ischemia (p < 0.001). Patients with lactate levels >3 mmol/L had a four-fold increased risk of mesenteric ischemia development (odds ratio [OR] 4.2, 95% confidence interval [CI] 2.4-7.5; area under the curve [AUC] 0.597; p < 0.002). Patients whose lactate levels remained >3 mmol/L on the first postoperative day had a nearly eight-fold increased risk (OR 7.8, 95% CI 4.6-13.3; AUC 0.68; p < 0.001), indicating that mesenteric ischemia developed at an early stage in almost every second patient (p < 0.001). For patients with normal or less elevated lactate levels, similar results were obtained for a >200% increase between the intraoperative and early postoperative periods (OR 4.1, 95% CI 2.4-6.8; AUC 0.62; p < 0.001). CONCLUSION: Late intraoperative and early postoperative lactate levels >3 mmol/L and increases >200%, even when remaining within the normal range, should raise the suspicion of subsequent mesenteric ischemia development.

Hybrid Procedure with Debranching from the Descending Aorta for Aortic Arch Aneurysm after Previous Open Repair.

Aortic arch aneurysms can be treated with hybrid procedures by endovascular exclusion and prior debranching of supra-aortic arteries. We report on a case of symptomatic arch aneurysm following previous supracoronary ascending aorta and hemiarch replacement with a very short proximal landing zone. A successful reconstruction was performed by retrograde revascularization of supra-aortic vessels from the descending aorta and subsequent endovascular repair deploying a proximal stent graft directly above the sinotubular junction with good results in the 4-year follow-up. Retrograde supra-aortic debranching may constitute a suitable approach for hybrid endovascular repair of aneurysms of the aortic arch and the ascending aorta in selected cases.

Autonomic outcome is better after endarterectomy than after stenting in patients with asymptomatic carotid stenosis.

OBJECTIVE: Carotid endarterectomy and stenting have comparable efficacy in stroke prevention in asymptomatic carotid stenosis. In patients with carotid stenosis, cardiac events have a more than threefold higher incidence than cerebrovascular events. Autonomic dysfunction predicts cardiovascular morbidity and mortality, and carotid stenosis interferes with baroreceptor and chemoreceptor function. We assessed the effect of elective carotid revascularization (endarterectomy vs stenting) on autonomic function as a major prognostic factor of cardiovascular health. METHODS: In 42 patients with ≥70% asymptomatic extracranial carotid stenosis, autonomic function was determined by analysis of heart rate variability (total band power [TP], high frequency band power [HF], low-frequency band power [LF], very low frequency band power [VLF]), baroreflex sensitivity (αHF, αLF), respiratory chemoreflex sensitivity (central apnea-hypopnea index), and cardiac chemoreflex sensitivity (hyperoxic TP, HF, LF, and VLF ratios) before and 30 days after revascularization. RESULTS: Patients with endarterectomy were older than patients with stenting (69 ± 7 vs 62 ± 7 years; P ≤ .008) but did not differ in gender distribution and preintervention autonomic function. Compared with stenting, postintervention heart rate variability was higher (ln TP, 6.7 [95% confidence interval (CI), 6.3-7.0] vs 6.1 [95% CI, 5.8-6.5; P ≤ .009]; ln HF, 4.5 [95% CI, 4.1-5.0] vs 4.0 [95% CI, 3.4-4.5; P ≤ .05]; ln VLF, 6.0 [95% CI, 5.7-6.4] vs 5.5 [95% CI, 5.2-5.9; P ≤ .02]); respiratory chemoreflex sensitivity (central apnea-hypopnea index, 5.5 [95% CI, 2.8-8.2] vs 10.0 [95% CI, 6.9-13.1; P ≤. 01]) and cardiac chemoreflex sensitivity (TP ratio, 1.2 [95% CI, 1.1-1.3] vs 1.0 [95% CI, 0.9-1.0; P ≤ .0001]; HF ratio, 1.4 [95% CI, 1.2-1.5] vs 0.9 [95% CI, 0.8-1.1; P ≤ .001]; LF ratio, 1.5 [95% CI, 1.3-1.6] vs 1.0 [95% CI, 0.8-1.1; P ≤ .0001]; VLF ratio, 1.2 [95% CI, 1.1-1.3) vs 1.0 [95% CI, 0.9-1.1; P ≤ .002]) were lower after endarterectomy. Postintervention baroreflex sensitivity did not differ after endarterectomy and stenting. CONCLUSIONS: Autonomic function was better after endarterectomy than after stenting. Better autonomic function after endarterectomy was based on restoration of chemoreceptor but not baroreceptor function and may improve cardiovascular long-term outcome.

Unusual course of an abdominal aortic aneurysm in a patient treated with chemotherapy for gastric cancer.

Most aortic aneurysms have a degenerative genesis and show a slow expansion over years. Only a few patients with a rapid progression of mycotic or inflammatory aneurysm during some weeks or months have been reported. We report a patient with a rapidly growing symptomatic infrarenal aneurysm with a maximal diameter of 53 mm, which developed over a 5-month period from a normal aorta and did not feature typical signs of degenerative, inflammatory, or mycotic aneurysm. The aneurysm was successfully treated by endovascular repair. A complete shrinking of the aneurysm sac was demonstrated during a few weeks postoperatively. Because the patient received chemotherapy with docetaxel, cisplatin, and 5-fluorouracil for metastatic gastric carcinoma 1 year before the aneurysm occurred, we postulate that chemotherapy induced a rapid expansion of the aorta in this patient.

Treatment of perigraft seroma in expanded polytetrafluoroethylene grafts by sequential fibrin sealing of the outer graft surface.

BACKGROUND: The recommended standard for treatment of perigraft seroma (PS) is the graft removal and the reconstruction using an alternative prosthesis. We assumed that a fibrin sealing of the outer surface of expanded polytetrafluoroethylene (ePTFE) grafts would prevent leakage and used this technique in the treatment and prevention of PS. METHODS: Over a 10-year period, 24 patients were treated for PS after subcutaneous implantation of ePTFE grafts (14 arterial bypasses and 10 arteriovenous grafts). Affected graft segments were temporarily removed and underwent sequential fibrin sealing technique before reimplantation. In addition, an in vitro experiment was carried out to demonstrate the efficacy of fibrin sealing to prevent leakage through the ePTFE graft wall, after its hydrophobic barrier was destroyed by filling with saline solution under pressure. RESULTS: A cure of PS was observed in 20 patients (84%) at a follow-up period of 37 ± 18 months. A later graft infection was not seen in any patient. The patency rate of reconstructed grafts appears to be unaffected. In the performed experiment we have demonstrated an elimination of leakage through the graft wall by the fibrin sealing technique. CONCLUSIONS: Sequential fibrin sealing of the outer surface is an effective way to treat PS in ePTFE grafts. However, failure of this treatment cannot be precluded. Further studies are necessary that may provide further insights into the causes and best treatment of PS and the possibly important role of PS in the aneurysm enlargement after complete endovascular exclusion with ePTFE endografts.

Experimental study of hemodynamics in procedures to treat access-related ischemia.

OBJECTIVE: This experimental study investigated the hemodynamic effect of corrective procedures for arteriovenous access-related ischemia in pulsatile flow. METHODS: Silicone models of an emulated tapered and bifurcated arterial tree of the upper arm and forearm were integrated into a pulsatile flow circuit. The model allowed the study of hemodynamics of simulated arteriovenous fistulas, including collateral circulation, as well as the study of different simulated procedures to improve distal hypoperfusion. Flow rates and arterial pressure were measured simultaneously during simulation of corrective procedures and correlated to hemodynamic values of uncorrected ischemia. RESULTS: It was demonstrated that the more proximally localized an arteriovenous anastomosis is, the higher the distal arterial pressure will be at any given fistula flow. Reduction of the fistula flow resulted in a significant improvement of distal perfusion. Ligation of the artery distal to the arteriovenous fistula to prevent retrograde flow increased the distal perfusion only slightly in simulated ischemia. In contrast, the simulated corrective procedures of distal revascularization interval ligation and proximalization of arterial inflow resulted in a significant improvement. The most significant improvement of distal perfusion was observed with the simulated proximalization technique, whereas the effect of distal revascularization technique was less pronounced at higher fistula flow. Arterial ligation after distal revascularization increased the distal pressure only by 10%. CONCLUSION: A more centrally localized arteriovenous anastomosis and a reduction of fistula flow significantly increase distal perfusion. The procedure of proximalization of arterial inflow is at least equivalent to the distal revascularization interval ligation technique for the correction of distal ischemia, but does not sacrifice a patent axial artery. The moderate effect of interval ligation of the latter technique should be evaluated by further intraoperative measurements.

Flow reduction in high-flow arteriovenous access using intraoperative flow monitoring.

PURPOSE: This study used intraoperative monitoring of the access flow to evaluate the results of flow reduction in the management of high-flow arteriovenous access-related symptoms of distal ischemia and cardiac insufficiency. METHODS: A retrospective study was conducted of 95 patients (78 with ischemia, 17 with cardiac failure) who underwent flow reduction between 1999 and 2005. A preoperatively measured access flow-volume rate > 800 mL/min for autogenous accesses (n = 77) and > 1200 mL/min for prosthetic accesses (n = 18) was the selection criterion for the use of a flow reduction procedure. Flow reduction was achieved using a spindle-like narrowing suture near the anastomosis and final placement of a polytetrafluoroethylene strip while a flow meter was used for intraoperatively measuring the access flow. The desired postoperative flow was 400 mL/min for autogenous and 600 mL/min for prosthetic accesses. RESULTS: The mean preoperative access flow was 1469 +/- 633 mL/min in patients with ischemia and 2084 +/- 463 mL/min in patients with cardiac failure, without significant differences between access types. The flow was reduced to 499 +/- 175 mL/min for autogenous accesses and to 676 +/- 47 mL/min for prosthetic accesses. The mean follow-up was 25 months (range, 1 to 73 months). Complete long-term relief of symptoms was observed in 86% of patients with ischemia and in 96% of patients with cardiac failure. Reconstruction significantly increased the digital-brachial index (0.41 +/- 0.12 vs 0.74 +/- 0.11; P < .05) and mean distal arterial pressure (47 +/- 17 mm Hg vs 79 +/- 21 mm Hg; P < .05) in patients with ischemia. Primary patency rates were significantly better for reconstructed autogenous accesses compared with rates of prosthetic accesses (91% +/- 4% vs 58% +/- 12% at 12 months; 81% +/- 6% vs 41% +/- 14% at 36 months; P < .001). The low patency of reconstructed prosthetic accesses is due to the high thrombosis risk of accesses that have a flow < 700 mL/min. CONCLUSIONS: Flow reduction using intraoperative access flow monitoring is an effective and durable technique allowing for the correction of distal ischemia and cardiac insufficiency in patients with a high-flow autogenous access. The desired postoperative access flow of 400 mL/min is not associated with an increased risk of thrombosis. Flow reduction of prosthetic access is as effective; however, a higher access flow than the desired 600 mL/min seems to be necessary to achieve an acceptable patency in prosthetic accesses.

Arterioarterial prosthetic loop: a new approach for hemodialysis access.

OBJECTIVES: In this report we present a novel procedure that uses an arterioarterial prosthetic loop (AAPL) with the proximal axillary or the femoral artery as a vascular access for hemodialysis in patients who have inadequate vascular conditions for creating an arteriovenous fistula or graft. METHODS: Between April 1996 and September 2004, 34 patients received 36 AAPLs as vascular access, either as an axillary chest loop (n = 31) or as a femoral loop (n = 5). In this procedure the artery is ligated between the anastomoses to direct flow through the AAPL. Data from all patients undergoing the procedure were prospectively collected. RESULTS: The indication for an AAPL was the unsuitability of large deep veins in 64%, steal syndrome in 11%, the combination of only a suitable femoral vein and severe peripheral arterial disease in 22%, and congestive heart failure in 3%. All AAPLs were cannulated 18 +/- 4 days postoperatively. Mean follow-up was 31 months (range, 1 to 83). Primary patency was 73% and secondary patency was 96% at 1 year; these rates at 3 years were 54% and 87%, respectively. The rate of all interventions for the maintenance of AAPL function was 0.47 procedures per patient year. Four grafts were abandoned. More than 11,000 hemodialyses with proven efficiency were performed. CONCLUSIONS: The AAPL is an unusual but useful and easy-to-perform alternative procedure to create vascular access for hemodialysis. It can provide survival for strictly selected patients in whom conventional vascular access is not possible. The axillary chest AAPL is preferred.

Computational fluid dynamics and vascular access.

Anastomotic intimal hyperplasia caused by unphysiological hemodynamics is generally accepted as a reason for dialysis access graft occlusion. Optimizing the venous anastomosis can improve the patency rate of arteriovenous grafts. The purpose of this study was to examine, evaluate, and characterize the local hemodynamics and, in particular, the wall shear stresses in conventional venous end-to-side anastomosis and in patch form anastomosis (Venaflo) by three-dimensional computational fluid dynamics (CFD). We investigated the conventional form of end-to-side anastomosis and a new patch form by numerical simulation of blood flow. The numerical simulation was done with a finite volume-based algorithm. The anastomotic forms were constructed with usual size and fixed walls. Subdividing the flow domain into multiple control volumes solved the fundamental equations. The boundary conditions were identical for both forms. The velocity profile of the patch form is better than that for the conventional form. The region of high static pressure caused by flow stagnation is reduced on the vein floor. The anastomotic wall shear stress is decreased. The results of this study strongly support patch form use to reduce the incidence of intimal hyperplasia and venous anastomotic stenoses.