Reinforcement learning for patient-specific optimal stenting of intracranial aneurysms.

Developing new capabilities to predict the risk of intracranial aneurysm rupture and to improve treatment outcomes in the follow-up of endovascular repair is of tremendous medical and societal interest, both to support decision-making and assessment of treatment options by medical doctors, and to improve the life quality and expectancy of patients. This study aims at identifying and characterizing novel flow-deviator stent devices through a high-fidelity computational framework that combines state-of-the-art numerical methods to accurately describe the mechanical exchanges between the blood flow, the aneurysm, and the flow-deviator and deep reinforcement learning algorithms to identify a new stent concepts enabling patient-specific treatment via accurate adjustment of the functional parameters in the implanted state.

[POSSIBLE REACTION TO SUTURE MATERIALS].

INTRODUCTION: The use of sutures is a common practice in plastic surgical procedures. The potential risk of developing an allergic reaction to suture materials exists. To the best of the authors' knowledge, this is the first case reported in the literature of such a reaction in aesthetic breast surgery. The aim of this review is to raise the awareness of possible allergic and infective or inflammatory reactions to the suture material and to expand the knowledge of the management and interventions which are critical for patient safety and satisfaction. More research is needed to study this challenging topic.

Importance of the biofilm matrix for the erosion stability of Bacillus subtilis NCIB 3610 biofilms.

Production and secretion of biomolecules can provide new emergent functionalities to the synthesizing organism. In particular, the secretion of extracellular polymeric substances (EPS) by biofilm forming bacteria creates a biofilm matrix that protects the individual bacteria within the biofilm from external stressors such as antibiotics, chemicals and shear flow. Although the main matrix components of biofilms formed by Bacillus subtilis are known, it remains unclear how these matrix components contribute to the erosion stability of B. subtilis biofilms. Here, we combine different biophysical techniques to assess this relation. In particular, we quantify the importance of specific biofilm matrix components on the erosion behavior of biofilms formed by the well-studied Bacillus subtilis NCIB 3610. We find that the absence of biofilm matrix components decreases the erosion stability of NCIB 3610 biofilms in water, largely by abolishing the hydrophobic surface properties of the biofilm and by reducing the biofilm stiffness. However, the erosion resistance of NCIB 3610 biofilms is strongly increased in the presence of metal ions or the antibiotic ciprofloxacin. In the first case, unspecific ionic cross-linking of biofilm components or individual bacteria seems to be responsible for the observed effect, and in the second case there seems to be an unspecific interaction between the antibiotic and the biofilm matrix. Taken together, our results emphasize the importance of the biofilm matrix to reduce biofilm erosion and give insights into how the specific biomolecules interact with certain chemicals to fulfill this task.

Synchronous subcutaneous granular cell tumours, a rare presentation.

We describe a unique presentation of a rare disease presentation of a granular cell tumour. A 36-year-old woman presents with a large symptomatic left flank mass that had been slowly increasing in size. Multiple synchronous subcutaneous masses were found at presentation on the left breast, right auricle and right cheek. After diagnosis of granular cell tumour by core needle biopsy, the masses were excised with histopathological and immunohistochemical analysis of both specimens confirming the presence of non-malignant granular cell tumours. Granular cell tumours are rare Schwann cell derived tumours that are typically asymptomatic and benign. These tumours are most often located in the head and neck, with multifocal disease present in approximately 5-16% of patients. Final pathology is necessary for diagnosis and frozen section is rarely helpful. Malignancy is present in approximately 2% of cases and can be diagnosed by the presence of a high mitotic rate, large nucleoli, necrosis, spindling and pleomorphism are other suspicious features. Granular cell tumours do not generally require adjuvant treatment. The mainstay of therapy is surgical resection with surveillance.

De Novo Reconstruction of a Hybrid Patella by Staged Fabrication of a Microvascular Bone Transplant with an Osteointegrated Prosthetic Socket.

Total patellectomy is sometimes unavoidable but usually results in severely impaired function, pain, and instability in the affected knee. Any patellar prosthetic solutions rely on a certain amount of remaining bone and therefore are not applicable after total patellectomy. Traditionally, reconstruction of a neopatella by avascular or allogeneic bone grafts is hampered by mechanical failure, resorption, or infection. We developed a new, 3-stage approach to reconstruct a hybrid patella composed of a revascularized scapula tip transplant fabricated with a prosthetic socket. The procedure is safe and provides optimal healing and prosthetic osteointegration through viable bone and dynamic stability to the considerable load a patella has to bear in unrestricted mobility. The technique also demonstrates successful integration of orthopedic prosthetic devices into current flap fabrication concepts.

Patient-specific reconstruction plates are the missing link in computer-assisted mandibular reconstruction: A showcase for technical description.

INTRODUCTION: Preoperative planning of mandibular reconstruction has moved from mechanical simulation by dental model casts or stereolithographic models into an almost completely virtual environment. CAD/CAM applications allow a high level of accuracy by providing a custom template-assisted contouring approach for bone flaps. However, the clinical accuracy of CAD reconstruction is limited by the use of prebent reconstruction plates, an analogue step in an otherwise digital workstream. TECHNICAL REPORT: In this paper the integration of computerized, numerically-controlled (CNC) milled, patient-specific mandibular plates (PSMP) within the virtual workflow of computer-assisted mandibular free fibula flap reconstruction is illustrated in a clinical case. Intraoperatively, the bone segments as well as the plate arms showed a very good fit. Postoperative CT imaging demonstrated close approximation of the PSMP and fibular segments, and good alignment of native mandible and fibular segments and intersegmentally. Over a follow-up period of 12 months, there was an uneventful course of healing with good bony consolidation. CONCLUSION: The virtual design and automated fabrication of patient-specific mandibular reconstruction plates provide the missing link in the virtual workflow of computer-assisted mandibular free fibula flap reconstruction.

Oncological long-term outcome of 4772 patients with prostate cancer undergoing radical prostatectomy: does the anaesthetic technique matter?

INTRODUCTION: Recent data suggest that using additional neuroaxial anaesthesia during oncological surgery is associated with favourable recurrence-free survival, when compared with general anaesthesia alone. We assessed the impact of adjunctive perioperative spinal anaesthesia and dose of opioids on the oncological long-term outcome of patients following radical prostatectomy. METHODS: We selected patients from our institutional review board-approved database who consecutively underwent radical prostatectomy between 2002 and 2007. Patients were stratified by type of anaesthesia, administered as general anaesthesia alone, or spinal anaesthesia in addition to general anaesthesia. Biochemical recurrence-free survival, metastasis-free survival and overall survival were analysed by a multivariate Cox regression model and by Kaplan-Meier analysis in propensity-score based matched cohorts, adjusted for standard clinico-pathological variables and year of surgery. RESULTS: Overall, 4772 patients were analysed. Regarding the type of anaesthesia no significant difference for biochemical recurrence-free survival, metastasis-free survival and overall survival was analysed by a multivariate Cox regression model (p = 0.5, 0.8 and 0.7). The Kaplan-Meier analyses after propensity-score matched based comparisons revealed no significant difference depending on type of anaesthesia for biochemical recurrence-free survival, metastasis-free survival and overall survival (p = 0.6, 0.1 and 0.4). The same accounted for a propensity-score matched model adjusted for the year of surgery on biochemical recurrence-free survival (p = 0.7). CONCLUSIONS: The oncological outcome after radical prostatectomy was not affected by the adjunctive use of spinal anaesthesia.

Right ventricular stroke volume variation: a tool to assess right ventricular volume responsiveness.

BACKGROUND: So far, only left ventricular functional preload indices are used as a routine to assess volume responsiveness. Right ventricular (RV) functional preload indices have been described, but offer no continuous monitoring. METHODS: Following ethical approval, a pressure-induced right ventricular failure (RVF) was induced with continuous infusion of a thromboxane-A2-analogue (U46619) in 15 anesthetized and ventilated pigs. Before and after increasing mean pulmonary artery pressure (MPAP) by 50%, right ventricular stroke volume variation (RVSVV) was assessed with an ultrasonic pulmonary artery flow probe. Measurements were repeated following volume depletion (- 300 mL) and stepwise retransfusion (200 mL of whole blood and 200 mL of a colloid solution). RESULTS: A significant and systematic increase in RVSVV during induction of RVF was observed. Volume depletion led to an increase in RVSVV and re-transfusion led to a decrease in RVSVV. RVSVV was higher and a significant decrease in RVSVV was present in all animals experiencing an increase in CO by more than 5% during retransfusion. CONCLUSION: RVSVV seems to reflect volume requirement of the right ventricle and it might prove a reliable parameter to assess volume responsiveness in RVF.

Mechanotransduction in the lungs.

Mechanical ventilation may induce or aggravate lung injury, a phenomenon known as ventilator induced lung injury (VILI). On a macroscopic level, the effects of mechanical stress and strain on lung tissue are well described. Increased tidal volumes may lead to volutrauma, raised airway pressures may cause barotrauma and cyclic collapse and reopening of alveolar units contributes to atelectrauma. These three harmful mechanisms may lead to local and systemic pulmonary inflammatory response known as biotrauma. The purpose of this review was to elucidate fundamental mechanisms involved in the mechanotransduction of mechanical stimuli on a cellular level. Bronchial epithelial cells in the distal airways as well as alveolar epithelial cells are exposed to a variety of mechanical forces. These cells are involved in sensing and translation of mechanical stimuli into an inflammatory response. This review provides insight into current knowledge of cellular and molecular pathways during the process of pulmonary epithelial mechanosensation and mechanotransduction under different mechanical conditions. Since evidence for specific pathways is generally lacking in some fields of alveolar epithelial mechanotransduction, this article aims at providing reasonable hypothesis for further investigation.

[Pharmacogenetics. Clinical relevance in anesthsiology]. / Pharmakogenetik. Klinische Bedeutung in der Anästhesiologie.

BACKGROUND: Pharmacogenetics deals with hereditary factors which influence the pharmacodynamics and pharmacokinetics of drugs leading to individual diverse reactions. Also in anesthesiology differences in the pharmacogenetics of patients can lead to relevant alterations in the pharmacodynamics of drugs. AIM: This article provides a summary of polymorphisms relevant to commonly used anesthetic agents and the clinical relevance in patients treated with these compounds. It describes the possibilities, the problems and limits of pharmacogenetic diagnostics and therapy and explains how this follows the target of individualized medicine. MATERIAL AND METHODS: This article describes in detail the alterations in pharmacodynamics and pharmakokinetics relevant for anesthesia and their clinical significance. Based on the results of current studies, an overview of the most important drugs in anesthesiology with significant polymorphisms is given. These include opioids, muscle relaxants, volatile anesthetic agents, non-steroidal anti-inflammatory drugs (NSAIDs), benzodiazepines, antiemetics and cardiovascular drugs as well as platelet aggregation inhibitors, anticoagulants and the so-called new oral anticoagulants. RESULTS: Genetic alterations can lead to substantial modifications in the effectiveness of drugs. Genetic alterations of opioid receptors and the enzyme cytochrome P450 (CYP) 2D6 can result in a failure of analgesia after administration of opioids. Alterations in plasma cholinesterase activity are associated with a prolonged effectiveness of muscle relaxants. Polymorphisms in ryanodine receptors can contribute to the development of the feared MH in patients after administration of volatile anesthetics or succinylcholine. CONCLUSION: The study results presented here emphasize that these days knowledge on pharmacogenetics should not be missing in modern induction of anesthesia. In the future a blood sample could enable physicians to identify pharmacologically relevant markers. And these could guide the decision on the prescription of drugs and their appropriate dose, in order to achieve the lowest risk of side effects and the highest effectiveness of the active substance.

Comparison of an automated respiratory systolic variation test with dynamic preload indicators to predict fluid responsiveness after major surgery.

BACKGROUND: Predicting the response of cardiac output to volume administration remains an ongoing clinical challenge. The objective of our study was to compare the ability to predict volume responsiveness of various functional measures of cardiac preload. These included pulse pressure variation (PPV), stroke volume variation (SVV), and the recently launched automated respiratory systolic variation test (RSVT) in patients after major surgery. METHODS: In this prospective study, 24 mechanically ventilated patients after major surgery were enrolled. Three consecutive volume loading steps consisting of 300 ml 6% hydroxyethylstarch 130/0.4 were performed and cardiac index (CI) was assessed by transpulmonary thermodilution. Volume responsiveness was considered as positive if CI increased by >10%. RESULTS: In total 72 volume loading steps were analysed, of which 41 showed a positive volume response. Receiver operating characteristic (ROC) curve analysis revealed an area under the curve (AUC) of 0.70 for PPV, 0.72 for SVV and 0.77 for RSVT. Areas under the curves of all variables did not differ significantly from each other (P>0.05). Suggested cut-off values were 9.9% for SVV, 10.1% for PPV, and 19.7° for RSVT as calculated by the Youden Index. CONCLUSION: In predicting fluid responsiveness the new automated RSVT appears to be as accurate as established dynamic indicators of preload PPV and SVV in patients after major surgery. The automated RSVT is clinically easy to use and may be useful in guiding fluid therapy in ventilated patients.

Changes in sevoflurane plasma concentration with delivery through the oxygenator during on-pump cardiac surgery.

BACKGROUND: It is unclear what factors affect the uptake of sevoflurane administered through the membrane oxygenator during cardiopulmonary bypass (CPB) and whether this can be monitored via the oxygenator exhaust gas. METHODS: Stable delivery of sevoflurane was administered to 30 elective cardiac surgery patients at 1.8 vol% (inspiratory) via the anaesthetic circuit and ventilator. During CPB, sevoflurane was administered in the oxygenator fresh gas supply (Compactflo Evolution™; Sorin Group, Milano, Italy). Sevoflurane plasma concentration (SPC) was measured using gas chromatography. Changes were correlated with bispectral index (BIS), patient temperature, haematocrit, plasma albumin concentration, oxygenator fresh gas flow, and the sevoflurane concentration in the oxygenator exhaust at predefined time points. RESULTS: The mean SPC pre-bypass was 54.9 µg ml(-1) [95% confidence interval (CI): 50.6-59.1]. SPC decreased to 43.2 µg ml(-1) (95% CI: 40.3-46.1; P<0.001) after initiation of CPB, and was lower still during rewarming and weaning from bypass, 39.4 µg ml(-1) (95% CI: 36.6-42.3; P<0.001). BIS did not exceed a value of 55. SPCs were higher during hypothermia (P<0.001) and with an increase in oxygenator fresh gas flow (P=0.015), and lower with haemodilution (P=0.027). No correlation was found between SPC and the concentration of sevoflurane in the oxygenator exhaust gas (r=-0.04; 95% CI: -0.18 to 0.09; P=0.53). CONCLUSIONS: The uptake of sevoflurane delivered via the membrane oxygenator during CPB seems to be affected by hypothermia, haemodilution, and changes in the oxygenator fresh gas supply flow. Measuring the concentration of sevoflurane in the exhaust from the oxygenator is not useful for monitoring sevoflurane administration during bypass.

The functional peroneus brevis as a third muscle component in the osteomyocutaneous fibula free-flap system.

Up to now, the peroneus brevis muscle was harvested as a non-functional pedicled muscle flap for defects around the ankle and the anterior lower leg. It has a reliable dual segmental vascularisation from the peroneal and the anterior tibial artery and a long, single motor nerve entering proximally. We report of a free microvascular transfer of the peroneus brevis as a neurotised functional muscle component in a composite osteo-musculo-cutaneous flow-through fibula flap. The flap components were used to reconstruct extensive radial and soft-tissue defects in a severely damaged forearm, whereas the peroneus brevis nerve was coapted to the proper flexor carpi radialis (FCR) motor nerve to counterbalance ulnar abduction, as all radial abductors were lost in the injury. Thirteen months later, the arm was fully reconstructed and an active radial abduction of 15° by the contracting peroneus muscle was achieved. Donor-site complications were absent. The peroneus brevis can expand the versatility of the peroneal-vessel-flap system as a third muscular component in four possible ways: a) addition of plain muscle bulk in the middle- and lower third of the fibula if left attached to the bone, b) as a reinnervated functional muscle as presented here, c) as a distally based muscle component if released from its origin from the middle third of the fibula and pedicled on its distal segmental branches from the peroneal vessels or d) as a distally pedicled osteomuscular flap permitting individual placement of a middle fibula segment.

Surgical angiogenesis with short-term immunosuppression maintains bone viability in rabbit allogenic knee joint transplantation.

BACKGROUND: Vascularized composite allotransplantation has the potential for reconstruction of joint defects but requires lifelong immunosuppression, with substantial risks. This study evaluates an alternative, using surgical angiogenesis from implanted autogenous vessels to maintain viability without long-term immunotherapy. METHODS: Vascularized knee joints were transplanted from Dutch Belted donors to New Zealand White rabbit recipients. Once positioned and revascularized microsurgically, a recipient-derived superficial inferior epigastric fascial flap and a saphenous arteriovenous bundle were placed within the transplanted femur and tibia, respectively, to develop a neoangiogenic, autogenous circulation. There were 10 transplants in group 1. Group 2 (n = 9) consisted of no-angiogenesis controls with ligated flaps and arteriovenous bundles. Group 3 rabbits (n = 10) were autotransplants with patent implants. Tacrolimus was used for 3 weeks to maintain nutrient flow during angiogenesis. At 16 weeks, the authors assessed bone healing, joint function, bone and cartilage mechanical properties, and histology. RESULTS: Group 1 allotransplants had more robust angiogenesis, better healing, improved mechanical properties, and better osteocyte viability than ligated controls (group 2). All three groups developed knee joint contractures and arthritic changes. Cartilage thickness and quality were poorer in allograft groups than in autotransplant controls. CONCLUSIONS: Surgical angiogenesis from implanted autogenous tissue improves bone viability, healing, and material properties in rabbit allogenic knee transplants. However, joint contractures and degenerative changes occurred in all transplants, regardless of antigenicity or blood supply. Experimental studies in a larger animal model with improved methods to maintain joint mobility are needed before the merit of living joint allotransplantation can be judged.

[When the resting membrane potential becomes restless. Acute hyperkalemia in the perioperative phase]. / Wenn das Ruhemembranpotenzial aus der Ruhe kommt. Akute Hyperkaliämie in der perioperativen Phase.

Acute hyperkalemia is a life-threatening event and often occurs abruptly and without warning in the perioperative field. Risk factors are found on multiple levels as they can derive from a patients pre-existing condition or result from the surgical intervention or management of anesthesia. The therapy of hyperkalemia depends on the dimensions of electrolyte disturbance and a distinction can be made between therapeutic measures with a rapid and those with a long-term effect.

[Intraoperative electrophysiological monitoring with evoked potentials]. / Intraoperatives elektrophysiologisches Monitoring mit evozierten Potenzialen.

During the last 30 years intraoperative electrophysiological monitoring (IOEM) has gained increasing importance in monitoring the function of neuronal structures and the intraoperative detection of impending new neurological deficits. The use of IOEM could reduce the incidence of postoperative neurological deficits after various surgical procedures. Motor evoked potentials (MEP) seem to be superior to other methods for many indications regarding monitoring of the central nervous system. During the application of IOEM general anesthesia should be provided by total intravenous anesthesia with propofol with an emphasis on a continuous high opioid dosage. When intraoperative MEP or electromyography guidance is planned, muscle relaxation must be either completely omitted or maintained in a titrated dose range in a steady state. The IOEM can be performed by surgeons, neurologists and neurophysiologists or increasingly more by anesthesiologists. However, to guarantee a safe application and interpretation, sufficient knowledge of the effects of the surgical procedure and pharmacological and physiological influences on the neurophysiological findings are indispensable.