The impact of selective visceral perfusion on intestinal macrohemodynamics and microhemodynamics in a porcine model of thoracic aortic cross-clamping

Intraoperative Hemoadsorption (Cytosorb™) during Open Thoracoabdominal Aortic Repair: A Pilot Randomized Controlled Trial

BACKGROUND

The efficacy of cytokine adsorption in controlling the early inflammation cascade after open thoracoabdominal aortic (TAAA) repair has not been investigated. The aim of this pilot randomized controlled trial was to assess the feasibility and effect of perioperative hemoadsorption during open TAAA repair.

METHODS

Patients scheduled for open TAAA repair with the use of cardiopulmonary bypass (CPB) were included. The patients were randomized the day before surgery to either intraoperative hemoadsorption during CPB or standard of care.

RESULTS

A total of 10 patients were randomly assigned to the intervention group, whereas the control group consisted of 17 patients (mean age of the total cohort, 51.1 ± 11.2 years, 67% male, 3 patients not randomized). The majority of baseline and perioperative characteristics were similar, and no device-related adverse events were reported. A trend to shorter ventilation times in the intervention group was observed (median 88 h vs. 510 h, p = 0.08, Δ422). Severe acute respiratory distress syndrome was significantly less in the intervention patients (p = 0.02).

CONCLUSIONS

This is the first pilot study showing that the intraoperative use of hemoadsorption in open TAAA repair patients may be feasible and safe, yet larger trials are needed to evaluate whether intraoperative hemoadsorption is associated with improved clinical outcomes.

Onset of Adverse Abdominal Events Due to Intestinal Ischemia-Reperfusion Injury after Aortic Cross-Clamping Is Associated with Elevated HSP70 Serum Levels in the Early Postoperative Phase

Tissue injury of the viscera during open thoracoabdominal aortic (TAA) reconstructions has been reported as the aftermath of the ischemia-reperfusion mechanism following supracoeliac aortic cross-clamping. Abdominal complications after open aortic reconstructions, although rare through the intraoperative implementation of selective visceral artery blood perfusion, are associated with high rates of reinterventions and a poor prognosis. Recent animal experiments demonstrated that provoking mesenteric ischemia in rats induces the leukocyte-mediated transcription of heat-shock protein 70 (HSP70), a chaperone belonging to the danger-associated molecular pattern proteins (DAMPs). Translating these findings clinically, we investigated the serum levels of HSP70 in patients undergoing open aortic reconstructions with supracoeliac clamping. We postoperatively observed a relevant induction of HSP70, which remained significantly elevated in cases of postoperative abdominal complications (paralytic ileus, abdominal compartment syndrome, and visceral malperfusion). The receiver-operator curve analysis revealed the reliable prognostic accuracy of HSP70 as a biomarker for these complications as soon as 12 h post-operation (AUC 0.908, sensitivity 88.9%, specificity 83.3%). In conclusion, measuring HSP70 serum levels in the early postoperative phase may serve as a further adjutant in the diagnostic decision making for both the vascular surgeon and intensivist for the timely detection and management of abdominal complications following open TAA surgery.

Visceral and renal protection in thoracoabdominal aortic surgery

Ischemic renal failure and visceral ischemia are two serious complications of the surgery for thoracoabdominal aortic aneurysm. The introduction of left atrial bypass, partial bypass, total circulatory arrest, and selective visceral perfusion has reduced the incidence of these complications over the past two decades. Yet these complications still persist, suggesting the sub-optimal nature of the available strategies.

The protective effects of topiramate on intestinal injury induced with infrarenal aortic occlusion via oxidative stress and apoptosis

Purpose: Prolonged surgical procedures and some clinical conditions such as surgeries of thoracoabdominal aorta, mesenteric ischemia, cardiopulmonary bypass, strangulated hernias and neonatal necrotizing enterocolitis may cause decreased perfusion and injury of relevant organs and tissues. After reperfusion, injuries may get worse, leading to ischemia-reperfusion (I/R) injury. Reperfusion following arterial clamping allows oxygen to ischemic tissues and produce injury by multiple mechanisms, including neutrophilic infiltration, intracellular adhesion molecules, and generation of reactive oxygen radicals. In this study with the analysis of SOD, MDA and Caspase-3 levels, we aimed to investigate the effect of topiramate on the outcome of I/R occured after abdominal aorta clamping on rats.Materials and Methods: Totaly 24 Sprague-Dawley male rats were randomly divided into three experimental groups; the control group (n = 8), I/R (n = 8) and I/R+ topiramate (n = 8). Topiramate (100 mg/kg/day); 50 mg/kg (single dose) was administered intraperitoneally after being diluted with saline 5 days before I/R.Results: The intestinal tissue of the ischemia group displayed hemorrhage, Crypts of Lieberkuhn degeneration, ulceration, vascular congestion and edematous fields as a result of aortic occlusion. We also observed that MDA levels and Caspase-3 positivity increased and SOD levels decreased in the small intestine. However, topiramate administration decreased Crypts of Lieberkuhn degeneration, ulceration, vascular congestion and edematous fields, Caspase-3 positivity, and MDA levels.Conclusion: Our findings suggest that topiramate is effective against aortic occlusion-induced intestinal injury by reducing oxidative stress and apoptosis.

Protocol of supra-visceral aortic ischemic preconditioning for open surgical repair of thoracoabdominal aortic aneurysm : The EPICATA study (Evaluation of the Efficacy of Ischemic PreConditioning on morbidity and mortality in open ThoracoAbdominal Aortic surgery)

Background

Open surgical repair (OSR) for thoracoabdominal aortic aneurysms (TAA) is associated with a high pulmonary and renal morbidity rate. Ischemic preconditioning (IPC) is a mechanism of protection against the deleterious effects of ischemia-reperfusion. To our knowledge IPC has never been tested during OSR for TAA.

Methods

The primary objective of the study is to evaluate the efficacy of IPC during OSR for TAA with respect to acute kidney injury (AKI) according to KDIGO and pneumonia/prolonged ventilation-time during the first 8 postoperative days. The secondary objectives are to compare both arms with respect to cardiac complications within 48 h, renal and pulmonary complications within 21 days and mortality at 60 days.

To assess the efficacy of IPC with respect to pulmonary and renal morbidity, a cox model for competing risks will be used. Assuming that the event occurs among 36% of the patients when no IPC is performed, the allocation of 55 patients to each arm should allow detecting a hazard ratio of at least 2.75 with a power of 80% when admitting 5% for an error of first kind. This means that 110 patients, enrolled in this multicenter study, may be randomised within 36 months of the first randomization.

Randomization will be performed to allocate patients either to surgery with preconditioning before aortic cross clamping (Arm 1) or to surgery without preconditioning before aortic cross clamping (Arm 2).

Randomization takes place during the intervention after intravenous injection of heparin, or after the start of femoral assistance. The procedure for IPC will be a supra-visceral thoracic aortic cross clamping for 5 min followed by an unclamping period of 5 min. This procedure will be repeated twice before starting thoracic aortic cross clamping needed to perform surgery.

Conclusions

Our hypothesis is that ischemic preconditioning could reduce clinical morbidity and the incidence of lung damage associated with supra-visceral aortic clamping.

Trial registration

EPICATAStudy registered in ClinicalTrial.gov / number: NCT03718312 on Oct.24.2018 URL number

New Large Animal Model for Aortic Aneurysms in the Viscerorenal Segment

BACKGROUND

Aortic aneurysms in the viscerorenal-segment are nowadays treatable by endovascular means. Previously, new endograft techniques were only tested in healthy animals. We aimed to establish a new large animal model for testing complex endovascular stent techniques preclinically.

METHODS

In sheep, four juxtarenal and two type IV thoracoabdominal aortic aneurysms were surgically created via a retroperitoneal approach. Two pieces out of a 10 × 15-cm bovine pericardial patch were sewn with the healthy aorta longitudinally. The viscerorenal segment was clamped, and the aorta was incised longitudinally. Then, the patches were longitudinally sewn together. In the meantime, antegrade flow through the native part of the aorta was already established by tangential clamping. Computed tomography angiography was performed after 4, 8, and 52 wk.

RESULTS

Technical success was 100%. The median surgical procedure time was 3 h, the median blood loss was 210 mL, and the viscerorenal-segment clamping time was 2-4 min. The animals started drinking 1 h after arousal from anesthesia. One animal died after 1 wk because of delayed bleeding and another died after 1 y because of aneurysm rupture by a secondary bacterial infection. Four animals survived. The proximal landing zone diameter and the clock position of the vessel were stable over 52 wk.

CONCLUSIONS

Surgical creation of an aortic aneurysm in the viscerorenal-segment in sheep was successful, without an ischemia/reperfusion injury. This animal model offers a new platform for evaluating innovative endovascular therapy options in vivo.

Evaluation of the NMR-MOUSE as a new method for continuous functional monitoring of the small intestine during different perfusion states in a porcine model

Objective

The study aim was to evaluate a small low-field NMR (nuclear magnetic resonance) scanner, the NMR-MOUSE^®, for detecting changes in intestinal diffusion under different (patho-) physiological perfusion states.

Methods

Laparotomy was performed on 8 female landrace pigs (body weight 70±6 kg) and the feeding vessels of several intestinal loops were dissected. Successively, the intestinal loops were examined using O2C (oxygen to see, LEA Medizintechnik GmbH, Giessen, Germany) for microcirculatory monitoring and the NMR-MOUSE^® for diffusion measurement (fast and slow components). On each loop the baseline measurement (physiological perfusion) was followed by one of the following main procedures: method 1 –ischemia; method 2 –flow reduction; method 3 –intraluminal glucose followed by ischemia; method 4 –intraluminal glucose followed by flow reduction. Additionally, standard perioperative monitoring (blood pressure, ECG, blood gas analyses) and histological assessment of intestinal biopsies was performed.

Results

There was no statistical overall time and method effect in the NMR-MOUSE measurement (fast component: p_time = 0.6368, p_method = 0.9766, slow component: p_time = 0.8216, p_method = 0.7863). Yet, the fast component of the NMR-MOUSE measurement showed contrary trends during ischemia (increase) versus flow reduction (decrease). The slow-to-fast diffusion ratio shifted slightly towards slow diffusion during flow reduction. The O2C measurement showed a significant decrease of oxygen saturation and microcirculatory blood flow during ischemia and flow reduction (p < .0001). The local microcirculatory blood amount (rHb) showed a significant mucosal increase (p_{Clamping(method 1)} = 0.0007, p_{Clamping(method 3)} = 0.0119), but a serosal decrease (p_{Clamping(method 1)} = 0.0119, p_{Clamping(method 3)} = 0.0078) during ischemia. The histopathological damage was significantly higher with increasing experimental duration and at the end of methods 3 and 4 (p < .0001,Fisher-test).

Conclusion

Monitoring intestinal diffusion changes due to different perfusion states using the NMR-MOUSE is feasible under experimental conditions. Despite the lack of statistical significance, this technique reflects perfusion changes and therefore seems promising for the evaluation of different intestinal perfusion states in the future. Beforehand however, an optimization of this technology, including the optimization of the penetration depth, as well as further validation studies under physiological conditions and including older animals are required.

A 30-Minute Supraceliac Aortic Clamping in the Rat Causes Death Due to an Inflammatory Response and Pulmonary Lesions

BACKGROUND

The treatment of thoracoabdominal aortic aneurysms through an open approach has general and pulmonary consequences of multiple etiologies. Our assumption was that the supraceliac aortic clamping needed for this operation causes a systemic inflammatory response associated with a pulmonary attack.

METHODS

We developed a model of 30-min supraceliac aortic clamping in Wistar rats weighing 300 g. After 90 min of reperfusion, the rats were sacrificed. The effects on the digestive tract wall were analyzed by measurement of the mucosal thickness/total thickness ratio. The effects on the mesenteric endothelial function were determined by an ex situ measurement of the arterial pressure/volume curves (third branch). The systemic consequences of the procedure were analyzed by dosing tumor necrosis factor alpha (TNFα), interleukin (IL)1β, and IL10 in the blood. The pulmonary consequences were analyzed by the measurement of macrophages, polymorphonuclear neutrophils (PNs), T lymphocyte infiltration, pulmonary apoptosis (TUNEL) and active caspase 3. The experimental scheme included 20 rats with ischemia-reperfusion (IR) and 20 control rats. An analysis of survival was carried out on 20 other rats (10 IR and 10 controls).

RESULTS

The results were expressed as average ± standard error of the mean. The statistical tests were Student's t-test and Mann-Whitney test. This visceral IR model decreased the ratio of the thickness of the intestinal mucosa compared with that of the control rats (0.77 ± 0.008 vs. 0.82 ± 0.009 [P < 0.001]). This local effect was not accompanied by any mesenteric endothelial dysfunction (P = 0.91). On a systemic level, IR increased TNFα (37.9 ± 1.5 vs. 28.2 ± 0.6 pg/mL; P < 0.0001), IL1β (67.1 ± 9.8 vs. 22.5 ± 5.6 pg/mL; P < 0.001), and IL10 (753.3 ± 96 vs. 3.7 ± 1.7 pg/mL; P < 0.0001). As regards the lungs, IR increased the parenchymal cellular infiltration by macrophages (6.8 ± 0.8 vs. 4.5 ± 0.4 cells per field; P < 0.05) and PNs (7.4 ± 0.5 vs. 6.2 ± 03 cells per field; P < 0.05). There was no increase in the pulmonary cellular apoptosis measured by TUNEL (P = 0.77) or in the caspase 3 activity (P = 0.59). The mortality of the visceral IR rats was 100% at 36 hr vs. 0% in the animals without IR.

CONCLUSIONS

This work showed that the inflammatory response to visceral IR had systemic and pulmonary effects which always results in the death in the rat.

State-of the-art review on the renal and visceral protection during open thoracoabdominal aortic aneurysm repair

During open thoracoabdominal aortic aneurysm repair (OTAAAR), there is an inevitable organ ischemic period that occurs when the abdominal arteries are being reattached to the aortic graft. Despite various protective techniques, the incidence of renal and visceral complications remains substantial. This state-of-the-art review gives an overview of the current and most evidence-based organ protection methods during OTAAAR, based on the most recent publications and personal experience. An electronic search was performed in four medical databases, using the following MeSH terms: thoracoabdominal aneurysm, TAAAR, visceral protection, renal protection, kidney, perfusion, and intestines. Every publication type was considered. The literature search was ended on August 31st, 2017. The left heart bypass (LHB) is currently the most frequent adjunct to provide distal aortic perfusion (DAP) during aortic clamping. Together with systemic hypothermia, it forms the cornerstone in organ protection during aortic clamping. Further renal protection can be obtained by selective renal perfusion (SRP) with cold blood or cold crystalloid solution, the latter enriched with mannitol. The perfusion should be administered in a volume- and pressure-controlled way and, if possible, by use of a pulsatile pump. Selective visceral perfusion (SVP) is not routinely used, as it does not provide adequate blood flow for visceral protection. The best way to protect the intestines is by minimizing the ischemic time. The preservation of renal and visceral function after OTAAAR can only be obtained with specific strategies before, during, and after the operation. This involves a series of measures, including selective digestive decontamination (SDD), avoidance of nephrotoxic drugs, minimizing the renal and intestinal ischemic time, systemic cooling, avoidance of hemodynamic instability, and regional protective perfusion of the kidneys. Future innovations in catheters, cardiac bypass flow types, mechanical components, hybrid vascular grafts, and pharmaceutical protection measures will hopefully further reduce organ complications.

Assessment of Blood Flow Patterns Distal to Aortic Occlusion Using CT in Patients with Resuscitative Endovascular Balloon Occlusion of the Aorta

BACKGROUND

Resuscitative endovascular balloon occlusion of the aorta (REBOA) is used to decrease hemorrhage below the level of aortic occlusion (AO); however, the amount of collateral blood flow below the level of occlusion is unknown. Our aim was to investigate blood flow patterns during complete AO in patients who underwent CT scan after REBOA.

STUDY DESIGN

Between February 2013 and January 2017, patients who received REBOA and underwent CT scan with intravenous contrast during full AO were included. Patients were excluded if they had a CT scan performed with the balloon partially or fully deflated.

RESULTS

Nine patients (8 men) were included; all had blunt trauma. Mean Injury Severity Score (±SD) was 48 ± 8 and mean age was 45 ± 19 years. Four had supra-celiac AO, and 5 had infra-renal AO. Arterial contrast enhancement was noted below the level of AO in all patients, and distal to REBOA sheath placement in 5. Collateralization from arteries above and below the AO was identified in all patients. Contrast extravasation distal to AO was identified in 4 patients, and hematomas in 8. Distal vascular enhancement patterns varied by level of AO and contrast administration site.

CONCLUSIONS

Aortic occlusion appears to dramatically decrease, but does not completely impede, distal perfusion during REBOA due to multiple pathways of collateralization. Active extravasation and hematomas can still be detected in the setting of full AO, with purposefully timed contrast and image acquisition. Blood flow persists below the level of both the AO and in-dwelling sheath. Dynamic flow studies are needed to determine the contribution of AO and sheath placement to distal tissue ischemia.

Passive Temporary Visceral Shunt from the Axillar Artery as an Adjunct Method during the Open Treatment of Thoracoabdominal Aortic Aneurysm

BACKGROUND

Distal aortic retrograde perfusion systems like the left heart bypass or femoro-femoral extracorporeal circulation are the methods of reference for organ protection during direct approaches to thoracoabdominal aortic aneurysms. The aim of this work was to evaluate the use of a passive arterial shunt to reduce visceral ischemia during aortic operations when occlusive diseases of the iliac arteries make distal aortic retrograde perfusion inappropriate.

METHODS

Ten patients affected by a Crawford type III thoracoabdominal aneurysm (TAA) were operated on between January 2013 and January 2015 with the use of a temporary shunt inserted onto the left axillar artery that allows visceral perfusion immediately after the aorta is opened. The operation was performed after a single dose of heparin (50 UI/kg). The sera lactate levels were measured 2 hr after the last aortic clamp was removed and compared with those obtained from a group of 19 patients operated on for a Crawford type IV TAA during the same period without any arterial shunt.

RESULTS

Neither mortality nor paraplegia occurred. The sera lactate levels were lower in the group of patients operated on for a type III TAA (2.57 ± 1) than for a type IV TAA (3.68 ± 1) (P < 0.01, Student's t-test).

CONCLUSION

This method was effective for low mesenteric ischemia, easy to perform, and did not require high doses of anticoagulants.

Extracorporeal circulation increases proliferation in the intestinal mucosa in a large animal model

OBJECTIVE

Extracorporeal circulation induces ischemia/reperfusion injury in the small intestinal wall. One reason for this damage is a perfusion shift from the muscular toward the mucosal layer. This study investigated the effect of this perfusion shift on the small-intestinal apoptosis and proliferation.

METHODS

Twenty-eight pigs were randomly assigned to the following cohorts and underwent a thoracolaparotomy and a 1 hour main procedure: cohort I: control; cohort II: thoracic aortic cross-clamping (TAC) without perfusion; cohort III: TAC and distal aortic perfusion (DAP); cohort IV: TAC, DAP, and selective visceral perfusion. The main procedure was followed by 2 hours of reperfusion in all cohorts. Tissue samples were taken during the experiment, stained, and analyzed for apoptosis and proliferation (caspase-3, annexin-V, terminal deoxynucleotide transferase-mediated deoxy uridine triphosphate nick-end labeling, and proliferating cell nuclear antigen). Six animals died unexpectedly during the experiment and were excluded from the analysis.

RESULTS

Extensive tissue damage and necrosis was only found in cohort II after the main procedure. In the mucosa, the proliferation was increased in cohort III at the end of the experiment (P = .0157 cohort I vs II). In contrast, the annexin-V/proliferating cell nuclear antigen ratio was significantly higher in cohorts II and IV than in cohorts I and II at the end of the experiment (P = .0034). Furthermore, the caspase-3/annexin-V ratio was increased in all cohorts at the end of the experiment (P = .0015).

CONCLUSIONS

Mucosal proliferation is the early repair mechanism of the limited small intestinal ischemia/reperfusion injury after DAP. Furthermore, the extensive surgical trauma shifted the mucosal apoptosis into an advanced state.

Microcirculatory perfusion shift in the gut wall layers induced by extracorporeal circulation

OBJECTIVE

Extracorporeal circulation (ECC) is regularly applied to maintain organ perfusion during major aortic and cardiovascular surgery. During thoracoabdominal aortic repair, ECC-driven selective visceral arterial perfusion (SVP) results in changed microcirculatory perfusion (shift from the muscularis toward the mucosal small intestinal layer) in conjunction with macrohemodynamic hypoperfusion. The underlying mechanism, however, is unclear. Therefore, the aim of this study was to assess in a porcine model whether ECC itself or the hypoperfusion induced by SVP is responsible for the mucosal/muscular shift in the small intestinal wall.

METHODS

A thoracoabdominal aortic approach was performed in 15 healthy pigs divided equally into three groups: group I, control; group II, thoracic aortic cross-clamping with distal aortic perfusion; and group III, thoracic aortic cross-clamping with distal aortic perfusion and SVP. Macrocirculatory and microcirculatory blood flow was assessed by transit time ultrasound volume flow measurement and fluorescent microspheres. In addition, markers for metabolism and intestinal ischemia-reperfusion injury were determined.

RESULTS

ECC with a roller pump induced a significant switch from the muscularis and mucosal layer of the small intestine, even with adequate macrocirculation (mucosal/muscular perfusion ratio: group I vs II, P = .005; group I vs III, P = .0018). Furthermore, the oxygen extraction ratio increased significantly in groups II (>30%) and III (>40%) in the beginning of the ECC compared with the control (group I vs II, P = .0037; group I vs III, P = .0062). Lactate concentrations and pH values did not differ between groups I and II; but group III demonstrated a significant shifting toward a lactate-associated acidosis (lactate: group I vs III, P = .0031; pH: group I vs III, P = .0001).

CONCLUSIONS

We demonstrated a significant shifting between the small intestinal gut wall layers induced by roller pump-driven ECC. The shift occurs independently of macrohemodynamics, with a significant effect on aerobic metabolism in the gut wall. Consequently, an optimal intestinal perfusion cannot be guaranteed by a roller pump; therefore, perfusion techniques need to be optimized.