Suppressing antagonistic bioengineering feedbacks doubles restoration success.

In a seagrass restoration project, we explored the potential for enhancing the restoration process by excluding antagonistic engineering interactions (i.e., biomechanical warfare) between two ecosystem engineers: the bioturbating lugworm Arenicola marina and the sediment-stabilizing seagrass Zostera noltii Hornem. Applying a shell layer underneath half of our seagrass transplants successfully reduced adult lugworm density by over 80% and reduced lugworm-induced microtopography (a proxy for lugworm disturbance) at the wave-sheltered site. At the wave-exposed site adult lugworm densities and microtopography were already lower than at the sheltered site but were further reduced in the shell-treated units. Excluding lugworms and their bioengineering effects corresponded well with a strongly enhanced seagrass growth at the wave-sheltered site, which was absent at the exposed site. Enhanced seagrass growth in the present study was fully assigned to the removal of lugworms' negative engineering effects and not to any (indirect) evolving effects such as an altered biogeochemistry or sediment-stabilizing effects by the shell layer. The context-dependency implies that seagrass establishment at the exposed site is not constrained by negative ecosystem-engineering interactions only, but also by overriding physical stresses causing poor growth conditions. Present findings underline that, in addition to recent emphasis on considering positive (facilitating) interactions in ecological theory and practice, it is equally important to consider negative engineering interactions between ecosystem-engineering species. Removal of such negative interactions between ecosystem-engineering species can give a head start to the target species at the initial establishment phase, when positive engineering feedbacks by the target species on itself are still lacking. Though our study was carried out in a marine environment with variable levels of wave disturbance, similar principles may be expected to apply to other ecosystems that are inhabited by ecosystem engineers.

Recent trend reversal for declining European seagrass meadows.

Seagrass meadows, key ecosystems supporting fisheries, carbon sequestration and coastal protection, are globally threatened. In Europe, loss and recovery of seagrasses are reported, but the changes in extent and density at the continental scale remain unclear. Here we collate assessments of changes from 1869 to 2016 and show that 1/3 of European seagrass area was lost due to disease, deteriorated water quality, and coastal development, with losses peaking in the 1970s and 1980s. Since then, loss rates slowed down for most of the species and fast-growing species recovered in some locations, making the net rate of change in seagrass area experience a reversal in the 2000s, while density metrics improved or remained stable in most sites. Our results demonstrate that decline is not the generalised state among seagrasses nowadays in Europe, in contrast with global assessments, and that deceleration and reversal of declining trends is possible, expectingly bringing back the services they provide.

Laboratory performance testing of venous cannulae during inlet obstruction.

Venous cannulae undergo continuous improvements to achieve better and safer venous drainage. Several cannula tests have been reported, though cannula performance during inlet obstruction has never been a test criterion. In this study, five different cannulae for proximal venous drainage were tested in a mock circulation that enabled measurement of hydraulic conductance after inlet obstruction by vessel collapse. Values for hydraulic conductance ranged from 1.11 x 10(-2) L/min/mm Hg for a Thin-Flex Single Stage Venous Cannula with an open-end lighthouse tip to 1.55 x 10(-2) L/min/mm Hg for a DLP VAD Venous Cannula featuring a swirled tip profile, showing a difference that amounts to nearly 40% of the lowest conductance value. Excessive venous drainage results in potentially dangerous high-negative venous line pressures independent of cannula design. Cannulatip design featuring swirled and grooved tip structures increases drainage capacity and enhances cannula performance during inlet obstruction.

Living in the intertidal: desiccation and shading reduce seagrass growth, but high salinity or population of origin have no additional effect.

The limiting effects of stressors like desiccation, light and salinity on seagrass growth and distribution are well-studied. However, little is known about their interactive effects, and whether such effects might differ among populations that are adapted to different local conditions. In two laboratory experiments we tested (a) if growth and development of intertidal, temperate Zostera noltii is affected by emergence time (experiment 1 and 2), and (b) how this is affected by an additional, second stressor, namely shading (experiment 1) or high salinity (25, 30 and 35, experiment 2). In addition, we tested (c) whether the effects of emergence time and salinity varied between three different European seagrass populations (Saint-Jacut/France, Oosterschelde/The Netherlands, and Sylt/Germany), which are likely adapted to different salinity levels (experiment 2). In both experiments, emergence of 8 h per tidal cycle (of 12 h) had a negative effect on seagrass relative growth rate (RGR), and aboveground biomass. Emergence furthermore reduced either rhizome length (experiment 1) or belowground biomass (experiment 2). Shading (experiment 1) resulted in lower RGR and a two-fold higher aboveground/belowground ratio. We found no interactive effects of emergence and shading stress. Salinity (experiment 2) did not affect seagrass growth or morphology of any of the three populations. The three tested populations differed greatly in morphology but showed no differential response to emergence or salinity level (experiment 2). Our results indicate that emergence time and shading show an additive negative effect (no synergistic or antagonistic effect), making the plants still vulnerable to such combination, a combination that may occur as a consequence of self-shading during emergence or resulting from algal cover. Emergence time likely determines the upper limit of Z. noltii and such shading will likely lower the upper limit. Shading resulted in higher aboveground/belowground ratios as is a general response in seagrass. Z. noltii of different populations originating from salinity 30 and 35 seem tolerant to variations in salinity within the tested range. Our results indicate that the three tested populations show morphotypic rather than ecotypic variation, at least regarding the salinity and emergence, as there were no interactive effects with origin. For restoration, this implies that the salinity regime of the donor and receptor site of Z. noltii is of no concern within the salinity range 25-35.

Perioperative strategy in colonic surgery; LAparoscopy and/or FAst track multimodal management versus standard care (LAFA trial).

BACKGROUND: Recent developments in large bowel surgery are the introduction of laparoscopic surgery and the implementation of multimodal fast track recovery programs. Both focus on a faster recovery and shorter hospital stay. The randomized controlled multicenter LAFA-trial (LAparoscopy and/or FAst track multimodal management versus standard care) was conceived to determine whether laparoscopic surgery, fast track perioperative care or a combination of both is to be preferred over open surgery with standard care in patients having segmental colectomy for malignant disease. METHODS/DESIGN: The LAFA-trial is a double blinded, multicenter trial with a 2 x 2 balanced factorial design. Patients eligible for segmental colectomy for malignant colorectal disease i.e. right and left colectomy and anterior resection will be randomized to either open or laparoscopic colectomy, and to either standard care or the fast track program. This factorial design produces four treatment groups; open colectomy with standard care (a), open colectomy with fast track program (b), laparoscopic colectomy with standard care (c), and laparoscopic surgery with fast track program (d). Primary outcome parameter is postoperative hospital length of stay including readmission within 30 days. Secondary outcome parameters are quality of life two and four weeks after surgery, overall hospital costs, morbidity, patient satisfaction and readmission rate. Based on a mean postoperative hospital stay of 9 +/- 2.5 days a group size of 400 patients (100 each arm) can reliably detect a minimum difference of 1 day between the four arms (alfa = 0.95, beta = 0.8). With 100 patients in each arm a difference of 10% in subscales of the Short Form 36 (SF-36) questionnaire and social functioning can be detected. DISCUSSION: The LAFA-trial is a randomized controlled multicenter trial that will provide evidence on the merits of fast track perioperative care and laparoscopic colorectal surgery in patients having segmental colectomy for malignant disease.

Neurological complications after coronary artery bypass grafting related to the performance of cardiopulmonary bypass.

STUDY OBJECTIVES: Neurologic disorders belong among the most serious complications of cardiac surgery. We tested the hypothesis that combinations of hemodynamic events from apparently normal cardiopulmonary bypass (CPB) procedures are related to the development of postoperative neurologic complications and affect the impact of common clinical risk factors. DESIGN: Retrospective study. SETTING: Cardiothoracic surgery department in a university hospital. METHODS AND PATIENTS: A multivariate statistical procedure (ie, cluster analysis) was applied to a data set of automatically recorded perfusions from 1,395 patients who had undergone coronary artery bypass grafting. One-way analysis of variance was used to select five parameters with the strongest significant correlation to postoperative neurologic complications for further cluster analysis. The dependencies in the clusters were tested against common clinical risk factors. To our knowledge, this is the first study of its kind. RESULTS: The following five parameters emerged for cluster analysis: mean arterial pressure (MAP); dispersion of MAP; dispersion of systemic vascular resistance; dispersion of arterial pulse pressure; and the maximum value of mixed venous saturation. Using these parameters, we found four clusters that were significantly different by CPB performance (first cluster, 389 patients; second cluster, 431 patients; third cluster; and fourth cluster, 229 patients). The frequency of postoperative neurologic complications was 0.3% in the first cluster and increased to 3.9% in the fourth cluster. Importantly, the impact of common clinical risk factors for postoperative neurologic complications was affected by the performance of the CPB procedure. For example, the frequency of neurologic complications among patients with cerebrovascular disease in their medical history was 22% in the fourth cluster, whereas it was zero in the second cluster. CONCLUSIONS: This study shows that apparently normal CPB procedures affect the impact of common clinical risk factors on postoperative neurologic complications. Patients who underwent CPB procedures with large fluctuations in hemodynamic parameters particularly showed an increased risk for the development of postoperative neurologic complications.

"Components separation technique" for the repair of large abdominal wall hernias.

BACKGROUND: The "components separation technique" is a method for abdominal wall reconstruction in patients with large midline hernias that cannot be closed primarily. The early and late results of this technique were evaluated in 43 patients. METHODS: Records of 43 patients, 11 women and 32 men, with a mean age of 49.7 (range 22 to 78), were reviewed for body length and weight, size and cause of the hernia, intra- and postoperative mortality and morbidity, with special attention given to wound and pulmonary complications. Patients were invited to attend the outpatient clinic afterward for at least 12 months for physical examination of the abdominal wall. RESULTS: The defect resulted after elective surgery in 19 patients and after acute surgery in 24 patients. In 11 patients, the defect was a result of open treatment of generalized peritonitis, and 13 patients had a recurrent incisional hernia. One patient died on the sixth postoperative day from mesenteric thrombosis. The postoperative course was complicated in 17 patients: fascial dehiscence in one, hematoma in five, seroma in two, wound infection in six, skin necrosis in one, and respiratory insufficiency in two. Thirty-eight patients were seen for followup. After a mean followup of 15.6 months (range 12 to 30 months), a recurrent hernia was found in 12 of the 38 patients (32%). The remaining four patients had no recurrent hernia after 1, 1, 3, and 4 months, respectively. CONCLUSIONS: The "components separation technique" is useful for the reconstruction of large abdominal wall hernias, especially under contaminated conditions in which the use of prosthetic material is contraindicated. Further research is needed to reduce the relatively high reherniation rate.

Thrombin generation during cardiopulmonary bypass: the possible role of retransfusion of blood aspirated from the surgical field.

BACKGROUND: In spite of using heparin-coated extracorporeal circuits, cardiopulmonary bypass (CPB) is still associated with an extensive thrombin generation, which is only partially suppressed by the use of high dosages of heparin. Recent studies have focused on the origins of this thrombotic stimulus and the possible role of retransfused suctioned blood from the thoracic cavities on the activation of the extrinsic coagulation pathway. The present study was designed to find during CPB an association between retransfusion of suctioned blood from the pericardium and pleural space, containing activated factor VIIa and systemic thrombin generation. METHODS: Blood samples taken from 12 consenting patients who had elective cardiac surgery were assayed for plasma factor VIIa, prothrombin fragment 1+2 (F1+2), and thrombin-antithrombin (TAT) concentrations. Blood aspirated from the pericardium and pleural space was collected separately, assayed for F1+2, TAT, and factor VIIa and retransfused to the patient after the aorta occlusion. RESULTS: After systemic heparinization and during CPB thrombin generation was minimal, as indicated by the lower than base line plasma levels of F1+2, and TAT after correction for hemodilution. In contrast, blood aspirated from the thoracic cavities had significantly higher levels of factor VIIa, F1+2, and TAT compared to the simultaneous samples from the blood circulation (P < 0.05). Furthermore, after retransfusion of the suctioned blood (range, 200-1600 mL) circulating levels of F1+2, and TAT rose significantly from 1.6 to 2.9 nmol/L (P = 0.002) and from 5.1 to 37.5 µg/L (P = 0.01), respectively. The increase in both F1+2, and TAT levels correlated significantly with the amount of retransfused suctioned blood (r = 0.68, P = 0.021 and r = 0.90, P = 0.001, respectively). However, the circulating factor VIIa levels did not correlate with TAT and F1+2 levels. CONCLUSIONS: These data suggest that blood aspirated from the thoracic cavities during CPB is highly thrombogenic. Retransfusion of this blood may, therefore, promote further systemic thrombin generation during CPB.

[Round ligament varicosities mimicking inguinal hernia during pregnancy]. / Een reponibele zwelling in de lies bij een zwangere: varicositas van het ligamentum teres uteri.

3 pregnant women, aged 34, 28, and 39 years respectively, presented with an inguinal swelling. In one patient the swelling was bilateral and painful. Reposition was possible and ultrasound examination revealed round ligament varicosities, the most common cause of an inguinal swelling during pregnancy. Expectative treatment is advised as the condition usually disappears after parturition. It is concluded that in every pregnant woman with an inguinal swelling, sonography with doppler imaging must be performed to confirm the diagnosis of round ligament varicosities to avoid unnecessary surgery.

Dynamic filling index: a novel parameter to monitor circulatory filling during minimized extracorporeal bypass.

OBJECTIVE: To evaluate the dynamic filling index, a novel parameter to monitor changes in venous return and drainable volume, in circulatory assisted patients. Minimized extracorporeal bypass systems lack volume buffering capacity, demanding tight control of drainable volume to maintain bypass flow. Therefore, with patients on minimized bypass quantitative assessment of venous drainable volume is crucial. METHODS: In seven patients undergoing coronary artery bypass grafting using minimized extracorporeal bypass we utilized luxation of the heart to induce a reduction in venous return. The speed of the centrifugal pump was transiently and periodically reduced to monitor resultant changes in bypass flow. The dynamic filling index, a measure of drainable volume, was calculated as Deltaflow/Deltaspeed. RESULTS: With luxation, the dynamic filling index was significantly reduced (from 2.4 +/- 0.2 to 2.0 +/- 0.2 ml/rotation, p = 0.001; 95% confidence interval of mean difference: 0.23-0.46 ml/rotation), whereas routinely recorded parameters, like bypass flow, pump inlet and arterial line pressure, did not change significantly. The intra-measurement reproducibility for the dynamic filling index was 0.5 ml/rotation (20% of the mean), suggesting good potential for this parameter to monitor on-pump venous return in patients. CONCLUSION: The dynamic filling index can detect small changes in venous return and drainable volume which remain unrevealed by routinely recorded parameters. This index could be a valuable tool to monitor and control circulatory filling in individual patients supported by minimized extracorporeal bypass.

An in vitro and in vivo study of the detection and reversal of venous collapse during extracorporeal life support.

The objective of this study was to investigate venous collapse (VC) related to venous drainage during the use of an extracorporeal life support circuit. A mock circulation was built containing a centrifugal pump and a collapsible vena cava model to simulate VC under controlled conditions. Animal experiments were performed for in vivo verification. Changing pump speed had a different impact on flow during a collapsed and a distended caval vein in both models. Flow measurement in combination with pump speed interventions allows for the detection and quantitative assessment of the degree of VC. Additionally, it was verified that a quick reversal of a VC situation could be achieved by a two-step pump speed intervention, which also proved to be more effective than a straightforward decrease in pump speed.

Border screening for SARS.

With the rapid international spread of severe acute respiratory syndrome (SARS) from March through May 2003, Canada introduced various measures to screen airplane passengers at selected airports for symptoms and signs of SARS. The World Health Organization requested that all affected areas screen departing passengers for SARS symptoms. In spite of intensive screening, no SARS cases were detected. SARS has an extremely low prevalence, and the positive predictive value of screening is essentially zero. Canadian screening results raise questions about the effectiveness of available screening measures for SARS at international borders.

Evaluation of a new condensed extra-corporeal circuit for cardiac surgery: a prospective randomized clinical pilot study.

This prospective randomized clinical pilot study was conducted to evaluate a recently introduced reduced volume CPB system that is coated with the biopassive Xcoating. Twenty-two patients undergoing coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB), either with a fully heparin-coated CPB circuit (control, n=11) or with an Xcoating coated condensed extra-corporeal circuit (CondECC, n=11), were included. We examined activation of the complement system (C3bc and C4bc), activation of neutrophils (BPI), the acute phase response (interleukin (IL)-6, and acute phase proteins (LBP, AGP, and CRP)), myocardial tissue injury (troponin T), hemolysis (free hemoglobin (FHb)), and clinical outcome parameters. Preoperative risk profiles were identical for both patient groups. All patients went through the procedure without major complications and were discharged from the hospital. FHb and BPI levels at the end of pump support (p < 0.01) and at 15 min after the administration of protamine (p < 0.05) were significantly higher in the control group. In addition, FHb levels were still significantly elevated upon arrival on the cardiothoracic intensive care unit (CICU) in the control group (p < 0.05). C3bc and C4bc, acute phase proteins, IL-6, and troponin T concentrations, and clinical outcome variables were identical in both patient groups. In conclusion, the evaluated condensed extracorporeal circuit is a flexible and multifunctional CPB sytem that offers safe procedures. Furthermore, the results indicate improved biocompatibility of this option for extracorporeal circulation.

Prevention of renal failure in patients undergoing thoracoabdominal aortic aneurysm repair.

OBJECTIVE: Renal failure is a potential complication after thoracoabdominal aortic aneurysm (TAAA) repair and is a significant risk factor for postoperative mortality. We assessed the results of distal aortic perfusion and continuous volume-controlled and pressure-controlled blood perfusion of the kidneys during TAAA repair in patients with preoperative normal and impaired renal function. METHODS: Surgical repair of TAAA was performed in 279 consecutive patients (type I, n = 90; type II, 117; type III, 42; type IV, 30). In 195 patients preoperative renal function was normal; however, in 84 patients renal insufficiency was diagnosed (serum creatinine concentration [SCr], 1.4-2.0 mg/dL, n = 46; SCr, 2.0-2.5 mg/dL, n = 20; and SCr, >2.5 mg/dL, n = 18). Renal perfusion was established with catheters connected to the left-sided heart bypass. Volume flow was assessed with ultrasound, and pressure channels in the catheters enabled pressure- controlled perfusion of the kidneys. RESULTS: Selective renal artery perfusion was achieved in all patients without technical problems or complications. In each catheter, mean arterial pressure was 69 mm Hg and volume flow was 275 mL/min. During aortic cross-clamping, urine output was uninterrupted, irrespective of clamp time. Most patients demonstrated limited or moderate increase in SCr concentration. In 17 patients (6%) SCr doubled, and peaked above 3 mg/dL, but returned to baseline levels within several days. Three patients (1%) required temporary dialysis but were discharged without further need for dialysis. In general, preoperative renal impairment did not worsen. CONCLUSION: Distal aortic and selective renal blood perfusion is an effective measure to protect renal function during TAAA repair, but only if perfusion is provided with adequate volume and pressure. This technique also averts dialysis in most patients with preoperative renal failure.