Quantitative analysis of intestinal perfusion with indocyanine green (ICG) and methylene blue (MB) using a single clinically approved fluorescence imaging system: a demonstration in a porcine model.

BACKGROUND: Near-infrared fluorescence (NIRF) angiography with intraoperative administration of indocyanine green (ICG) has rapidly disseminated in clinical practice. Another clinically approved, and widely available dye, methylene blue (MB), has up to now not been used for this purpose. Recently, we demonstrated promising results for the real-time evaluation of intestinal perfusion using this dye. The primary aim of this study was to perform a quantitative analysis of bowel perfusion assessment for both ICG and MB. METHODS: Four mature female Landrace pigs underwent laparotomy under general anesthesia. An ischemic bowel loop with five regions of interest (ROIs) with varying levels of perfusion was created in each animal. An intravenous (IV) injection of 0.25 mg/kg-0.50 mg/kg MB was administered after 10 min, followed by NIRF imaging in MB mode and measurement of local lactate levels in all corresponding ROIs. This procedure was repeated in ICG mode (IV dose of 0.2 mg/kg) after 60 min. The quest spectrum fluorescence camera (Quest Medical Imaging, Middenmeer, The Netherlands) was used for NIRF imaging of both MB and ICG. RESULTS: Intraoperative NIRF imaging of bowel perfusion assessment with MB and ICG was successful in all studied animals. Ingress (i/s) levels were calculated and correlated with local lactate levels. Both MB and ICG ingress values showed a significant negative correlation (r = - 0.7709; p = < 0.001; r = - 0.5367, p = 0.015, respectively) with local lactate levels. This correlation was stronger for MB compared to ICG, although ICG analysis showed higher absolute ingress values. CONCLUSION: Our fluorescence quantification analysis validates the potential to use MB for bowel perfusion assessment besides the well-known and widely used ICG. Further human studies are necessary to translate our findings to clinical applications.

Simultaneous, Multi-Channel, Near-Infrared Fluorescence Visualization of Mesenteric Lymph Nodes Using Indocyanine Green and Methylene Blue: A Demonstration in a Porcine Model.

Near-infrared fluorescence (NIRF) image-guided surgery is a useful tool that can help reduce perioperative complications and improve tissue recognition. Indocyanine green (ICG) dye is the most frequently used in clinical studies. ICG NIRF imaging has been used for lymph node identification. However, there are still many challenges in lymph node identification by ICG. There is increasing evidence that methylene blue (MB), another clinically applicable fluorescent dye, can also be useful in the intraoperative fluorescence-guided identification of structures and tissues. We hypothesized that MB NIRF imaging could be used for lymph node identification. The aim of this study was to evaluate the feasibility of intraoperative lymph node fluorescence detection using intravenously (IV) administered MB and compare it to ICG via a camera that has two dedicated near-infrared (NIR) channels. Three pigs were used in this study. ICG (0.2 mg/kg) was administered via a peripheral venous catheter followed by immediate administration of MB (0.25 mg/kg). NIRF images were acquired as video recordings at different time points (every 10 min) over an hour using the QUEST SPECTRUM® 3 system (Quest Medical Imaging, Middenmeer, The Netherlands), which has two dedicated NIR channels for simultaneous intraoperative fluorescence guidance. The 800 nm channel was used to capture ICG fluorescence and the 700 nm channel was used for MB. The target (lymph nodes and small bowel) and the background (vessels-free field of the mesentery) were highlighted as the regions of interest (ROIs), and corresponding fluorescence intensities (FI) from these ROIs were measured. The target-to-background ratio (TBR) was then computed as the mean FI of the target minus the mean FI of the background divided by the mean FI of the background. In all included animals, a clear identification of lymph nodes was achieved at all time points. The mean TBR of ICG in lymph nodes and small bowel was 4.57 ± 1.00 and 4.37 ± 1.70, respectively for the overall experimental time. Regarding MB, the mean TBR in lymph nodes and small bowel was 4.60 ± 0.92 and 3.27 ± 0.62, respectively. The Mann-Whitney U test of the lymph node TBR/small bowel TBR showed that the TBR ratio of MB was statistically significantly higher than ICG. The fluorescence optical imaging technology used allows for double-wavelength assessment. This feasibility study proves that lymph nodes can be discriminated using two different fluorophores (MB and ICG) with different wavelengths. The results suggest that MB has a promising potential to be used to detect lymphatic tissue during image-guided surgery. Further preclinical trials are needed before clinical translation.

Simultaneous fluorescence imaging of bowel perfusion and ureter delineation using methylene blue: a demonstration in a porcine model.

BACKGROUND: Intraoperative near-infrared fluorescence imaging (NIRF) with preoperative optical dye administration is a promising technique for quick and easy intraoperative visualization of the ureter and for an improved, real-time assessment of intestinal perfusion. During colorectal surgery, there is a need for simultaneous non-invasive ureteral imaging and bowel perfusion assessment, using one single camera system. The purpose of this study is to investigate the feasibility of simultaneous intestinal perfusion and ureteral imaging using a single commercially available NIRF imaging system. METHODS: Six Landrace pigs underwent laparotomy under general anesthesia in this experiment. An intravenous (IV) dose of 0.2 mg/kg indocyanine green (ICG) was given to assess bowel perfusion. Two pairs received a methylene blue (MB) iv injection of 0.75, 0.50 or 0.25 mg/kg respectively to investigate ureteral visualization. Quest Spectrum Fluorescence Camera (Quest Medical Imaging, Middenmeer, The Netherlands) was used for NIRF imaging. RESULTS: Ureter visualization and bowel perfusion under NIRF imaging was achieved in all animals. All ureters were visible after five to ten minutes and remained clearly visible until the end of every experiment (120-420 min). A mixed model analysis did not show any significant differences neither between the three groups nor over time. Importantly, we demonstrated that bowel perfusion could be visualized with methylene blue (MB) as well. We observed no interference between ICG and MB and a faster washout of MB. CONCLUSION: We successfully demonstrated simultaneous fluorescence angiography with ICG and ureteral imaging with MB in the same surgical procedure, with the same commercially available NIRF imaging equipment. More importantly, we showed that the use MB is adequate for bowel perfusion assessment and ureter visualization with this NIRF imaging system. Besides, MB showed an earlier washout time, which can be clinical beneficial as a repeated dye injection may be necessary during a surgical procedure.

SOLVe: a closed-loop system focused on protective mechanical ventilation.

BACKGROUND: Mechanical ventilation is an essential component in the treatment of patients with acute respiratory distress syndrome. Prompt adaptation of the settings of a ventilator to the variable needs of patients is essential to ensure personalised and protective ventilation. Still, it is challenging and time-consuming for the therapist at the bedside. In addition, general implementation barriers hinder the timely incorporation of new evidence from clinical studies into routine clinical practice. RESULTS: We present a system combing clinical evidence and expert knowledge within a physiological closed-loop control structure for mechanical ventilation. The system includes multiple controllers to support adequate gas exchange while adhering to multiple evidence-based components of lung protective ventilation. We performed a pilot study on three animals with an induced ARDS. The system achieved a time-in-target of over 75 % for all targets and avoided any critical phases of low oxygen saturation, despite provoked disturbances such as disconnections from the ventilator and positional changes of the subject. CONCLUSIONS: The presented system can provide personalised and lung-protective ventilation and reduce clinician workload in clinical practice.

MRI for the Detection of Small Bowel Ischemic Injury in Arterial Acute Mesenteric Ischemia: Preclinical Study in a Porcine Model.

BACKGROUND: MRI is the reference for the diagnosis of arterial cerebral ischemia, but its role in acute mesenteric ischemia (AMI) is poorly known. PURPOSE: To assess MRI detection of early ischemic bowel lesions in a porcine model of arterial AMI. STUDY TYPE: Prospective/cohort. ANIMAL MODEL: Porcine model of arterial AMI obtained by embolization of the superior mesenteric artery (seven pigs). FIELD STRENGTH/SEQUENCE: A 5-T. T1 gradient-echo-weighted-imaging (WI), half-Fourier-acquisition-single-shot-turbo-spin-echo, T2 turbo-spin-echo, true-fast-imaging-with-steady-precession (True-FISP), diffusion-weighted-echo-planar (DWI). ASSESSMENT: T1-WI, T2-WI, and DWI were performed before and continuously after embolization for 6 hours. The signal intensity (SI) of the ischemic bowel was assessed visually and quantitatively on all sequences. The apparent diffusion coefficient (ADC) was assessed. STATISTICAL TESTS: Paired Student's t-test or Mann-Whitney U-test, significance at P < 0.05. RESULTS: One pig died from non-AMI-related causes. The remaining pigs underwent a median 5 h53 (range 1 h24-6 h01) of ischemia. Visually, the ischemic bowel showed signal hyperintensity on DWI-b800 after a median 85 (57-276) minutes compared to the nonischemic bowel. DWI-b800 SI significantly increased after 2 hours (+19%) and the ADC significant decrease within the first hour (-31%). The ischemic bowel was hyperintense on precontrast T1-WI after a median 87 (70-171) minutes with no significant quantitative changes over time (P = 0.46-0.93). The ischemic bowel was hyperintense on T2-WI in three pigs with a significant SI increase on True-FISP after 1 and 2 hours. DATA CONCLUSION: Changes in SI and ADC can be seen early after the onset of arterial AMI with DWI. The value of T2-WI appears to be limited. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY: Stage 2.

International survey among surgeons on the perioperative management of rectal cancer.

BACKGROUND: Several pivotal studies and international guidelines on the perioperative management of rectal cancer have been published. However, little is known about the current state of perioperative management of rectal cancer patients in clinical practice worldwide. METHODS: An online survey including 13 questions focusing on key topics related to the perioperative management of patients with rectal cancer was conducted among colorectal surgeons registered within the database of the Research Institute Against Digestive Cancer (IRCAD). RESULTS: A total of 535 respondents from 89 countries participated in the survey. Most surgeons worked in the European region (40.9%). Two hundred and fifty-four respondents (47.5%) performed less than 25% of surgical procedures laparoscopically. The most commonly used definition of the upper limit of the rectum was a fixed distance from the anal verge (23.4%). Magnetic resonance imaging was used to define the upper limit of the rectum by 258 respondents (48.2%). During total mesorectal excision (TME), 301 respondents (56.3%) used a high-tie technique. The most commonly constructed anastomosis was an end-to-end anastomosis (68.2%) with the majority of surgeons performing a leak test intraoperatively (88.9%). A total of 355 respondents (66.4%) constructed a diverting ostomy, and the majority of these surgeons constructed an enterostomy (82%). A total of 208 respondents (39.3%) closed a stoma within 8 weeks. Lastly, 135 respondents (25.2%) introduced a solid diet on postoperative day 1. CONCLUSION: There is considerable heterogeneity in the perioperative management of rectal cancer patients worldwide with several discrepancies between current international practice and recommendations from international guidelines. To achieve worldwide standardization in rectal cancer care, further research is needed to elucidate the cause of this heterogeneity and find ways of improved implementation of best practice recommendations.

Experimental evaluation of laparoscopic laser speckle contrast imaging to visualize perfusion deficits during intestinal surgery.

BACKGROUND: Ischemia at the site of an intestinal anastomosis is one of the most important risk factors for anastomotic leakage (AL). Consequently, adequate intestinal microperfusion is essential for optimal tissue oxygenation and anastomotic healing. As visual inspection of tissue viability does not guarantee an adequate objective evaluation of intestinal microperfusion, surgeons are in dire need of supportive tools to decrease anastomotic leakage after colorectal surgery. METHODS: In this feasibility study, laparoscopic laser speckle contrast imaging (LSCI) was used to evaluate intestinal microperfusion in an experimental ischemic bowel loop model. Both large and small ischemic loops were created from the small intestine of a pig; each loop was divided into 5 regions of interest (ROI) with varying levels of ischemia. Speckle contrast and local capillary lactate (LCL) was measured in all ROIs. RESULTS: Both real-time visualization of intestinal microperfusion and induced perfusion deficits was achieved in all bowel loops. As a result, the emergence of regions of intestinal ischemia could be predicted directly after iatrogenic perfusion limitation, whereas without LSCI signs of decreased intestinal viability could only be seen after 30 minutes. Additionally, a significant relation was found between LCL and LSCI. CONCLUSION: In conclusion, LSCI can achieve real-time intraoperative visualization of intestinal microperfusion deficits, allowing for accurate prediction of long-term postoperative ischemic complications. With this revealing capacity, LSCI could potentially facilitate surgical decision-making when constructing intestinal anastomoses in order to mitigate ischemia-related complications such as AL.

Diagnostic Performance of Magnetic Resonance Imaging for Parathyroid Localization of Primary Hyperparathyroidism: A Systematic Review.

Accurate preoperative localization is crucial for successful minimally invasive parathyroidectomy in primary hyperparathyroidism (PHPT). Preoperative localization can be challenging in patients with recurrent and/or multigland disease (MGD). This has led clinicians to investigate multiple imaging techniques, most of which are associated with radiation exposure. Magnetic resonance imaging (MRI) offers ionizing radiation-free and accurate imaging, making it an attractive alternative imaging modality. The objective of this systematic review is to provide an overview of the diagnostic performance of MRI in the localization of PHPT. PubMed and Embase libraries were searched from 1 January 2000 to 31 March 2023. Studies were included that investigated MRI techniques for the localization of PHPT. The exclusion criteria were (1) secondary/tertiary hyperparathyroidism, (2) studies that provided no diagnostic performance values, (3) studies published before 2000, and (4) studies using 0.5 Tesla MRI scanners. Twenty-four articles were included in the systematic review, with a total of 1127 patients with PHPT. In 14 studies investigating conventional MRI for PHPT localization, sensitivities varied between 39.1% and 94.3%. When employing more advanced MRI protocols like 4D MRI for PHPT localization in 11 studies, sensitivities ranged from 55.6% to 100%. The combination of MR imaging with functional techniques such as 18F-FCH-PET/MRI yielded the highest diagnostic accuracy, with sensitivities ranging from 84.2% to 100% in five studies. Despite the limitations of the available evidence, the results of this review indicate that the combination of MR imaging with functional imaging techniques such as 18F-FCH-PET/MRI yielded the highest diagnostic accuracy. Further research on emerging MR imaging modalities, such as 4D MRI and PET/MRI, is warranted, as MRI exposes patients to minimal or no ionizing radiation compared to other imaging modalities.

Computer-Assisted Differentiation between Colon-Mesocolon and Retroperitoneum Using Hyperspectral Imaging (HSI) Technology.

Complete mesocolic excision (CME), which involves the adequate resection of the tumor-bearing colonic segment with "en bloc" removal of its mesocolon along embryological fascial planes is associated with superior oncological outcomes. However, CME presents a higher complication rate compared to non-CME resections due to a higher risk of vascular injury. Hyperspectral imaging (HSI) is a contrast-free optical imaging technology, which facilitates the quantitative imaging of physiological tissue parameters and the visualization of anatomical structures. This study evaluates the accuracy of HSI combined with deep learning (DL) to differentiate the colon and its mesenteric tissue from retroperitoneal tissue. In an animal study including 20 pig models, intraoperative hyperspectral images of the sigmoid colon, sigmoid mesentery, and retroperitoneum were recorded. A convolutional neural network (CNN) was trained to distinguish the two tissue classes using HSI data, validated with a leave-one-out cross-validation process. The overall recognition sensitivity of the tissues to be preserved (retroperitoneum) and the tissues to be resected (colon and mesentery) was 79.0 ± 21.0% and 86.0 ± 16.0%, respectively. Automatic classification based on HSI and CNNs is a promising tool to automatically, non-invasively, and objectively differentiate the colon and its mesentery from retroperitoneal tissue.

Laparoscopic Laser Speckle Contrast Imaging Can Visualize Anastomotic Perfusion: A Demonstration in a Porcine Model.

BACKGROUND: Intestinal resection causes inevitable vascular damage, which cannot always be seen during an intraoperative clinical assessment of local intestinal perfusion. If left unaltered, impaired perfusion can lead to complications, such as anastomotic leakage (AL). Therefore, we demonstrate the use of a novel laparoscopic laser speckle contrast imaging (LSCI)-based approach in order to assess local intestinal perfusion during the construction of intestinal anastomoses. METHODS: Three segments were isolated from the small intestine of a pig, while the perfusion of each was compromised by coagulating 7-8 mesenteric arteries. Both clinical assessments and LSCI were used to detect the induced perfusion deficits and to subsequently guide a transection in either a well perfused, marginally perfused, or poorly perfused tissue area within the segment. Bowel ends were then utilized for the creation of three differently perfused anastomoses: well perfused/well perfused (anastomosis segment 1), well perfused/poorly perfused (anastomosis segment 2), and poorly perfused/poorly perfused (anastomosis segment 3). After construction of the anastomoses, a final perfusion assessment using both clinical assessment and LSCI was executed in order to evaluate the vascular viability of the anastomosis. RESULTS: Laparoscopic LSCI enabled continuous assessment of local intestinal perfusion and allowed for detection of perfusion deficits in real time. The imaging feedback precisely guided the surgical procedure, and, when evaluating the final anastomotic perfusion, LSCI was able to visualize the varying degrees of perfusion, whereas standard clinical assessment yielded only minor differences in visual appearance of the tissue. CONCLUSIONS: In this technical note, we demonstrate a novel LSCI-based approach for intraoperative perfusion assessment. With its ability to continuously visualize perfusion in real time, laparoscopic LSCI has significant potential for the optimization of anastomotic surgery in the near future.

In Vivo Imaging Evaluation of Fluorescence Intensity at Tail Emission of Near-Infrared-I (NIR-I) Fluorophores in a Porcine Model.

Over the last decade fluorescence-guided surgery has been primarily focused on the NIR-I window. However, the NIR-I window has constraints, such as limited penetration and scattering. Consequently, exploring the performance of NIR-I dyes at longer wavelengths (i.e., the NIR-II window) is crucial to expanding its application. Two fluorophores were used in three pigs to identify the mean fluorescence intensity (MFI) using two commercially available NIR-I and NIR-II cameras. The near-infrared coating of equipment (NICE) was used to identify endoluminal surgical catheters and indocyanine green (ICG) for common bile duct (CBD) characterization. The NIR-II window evaluation showed an MFI of 0.4 arbitrary units (a.u.) ± 0.106 a.u. in small bowel NICE-coated catheters and an MFI of 0.09 a.u. ± 0.039 a.u. in gastric ones. In CBD characterization, the ICG MFI was 0.12 a.u. ± 0.027 a.u., 0.18 a.u. ± 0.100 a.u., and 0.22 a.u. ± 0.041 a.u. at 5, 35, and 65 min, respectively. This in vivo imaging evaluation of NIR-I dyes confirms its application in the NIR-II domain. To the best of our knowledge, this is the first study assessing the MIF of NICE in the NIR-II window using a commercially available system. Further comparative trials are necessary to determine the superiority of NIR-II imaging systems.

Induction of severe hypoxemia and low lung recruitability for the evaluation of therapeutic ventilation strategies: a translational model of combined surfactant-depletion and ventilator-induced lung injury.

BACKGROUND: Models of hypoxemic lung injury caused by lavage-induced pulmonary surfactant depletion are prone to prompt recovery of blood oxygenation following recruitment maneuvers and have limited translational validity. We hypothesized that addition of injurious ventilation following surfactant-depletion creates a model of the acute respiratory distress syndrome (ARDS) with persistently low recruitability and higher levels of titrated "best" positive end-expiratory pressure (PEEP) during protective ventilation. METHODS: Two types of porcine lung injury were induced by lung lavage and 3 h of either protective or injurious ventilation, followed by 3 h of protective ventilation (N = 6 per group). Recruitment maneuvers (RM) and decremental PEEP trials comparing oxygenation versus dynamic compliance were performed after lavage and at 3 h intervals of ventilation. Pulmonary gas exchange function, respiratory mechanics, and ventilator-derived parameters were assessed after each RM to map the course of injury severity and recruitability. RESULTS: Lung lavage impaired respiratory system compliance (Crs) and produced arterial oxygen tensions (PaO2) of 84±13 and 80±15 (FIO2 = 1.0) with prompt increase after RM to 270-395 mmHg in both groups. After subsequent 3 h of either protective or injurious ventilation, PaO2/FIO2 was 104±26 vs. 154±123 and increased to 369±132 vs. 167±87 mmHg in response to RM, respectively. After additional 3 h of protective ventilation, PaO2/FIO2 was 120±15 vs. 128±37 and increased to 470±68 vs. 185±129 mmHg in response to RM, respectively. Subsequently, decremental PEEP titration revealed that Crs peaked at 36 ± 10 vs. 25 ± 5 ml/cm H2O with PEEP of 12 vs. 16 cmH2O, and PaO2/FIO2 peaked at 563 ± 83 vs. 334 ± 148 mm Hg with PEEP of 16 vs. 22 cmH2O in the protective vs. injurious ventilation groups, respectively. The large disparity of recruitability between groups was not reflected in the Crs nor the magnitude of mechanical power present after injurious ventilation, once protective ventilation was resumed. CONCLUSION: Addition of transitory injurious ventilation after lung lavage causes prolonged acute lung injury with diffuse alveolar damage and low recruitability yielding high titrated PEEP levels. Mimicking lung mechanical and functional characteristics of ARDS, this porcine model rectifies the constraints of single-hit lavage models and may enhance the translation of experimental research on mechanical ventilation strategies.

Perioperative Hyperspectral Imaging to Assess Mastectomy Skin Flap and DIEP Flap Perfusion in Immediate Autologous Breast Reconstruction: A Pilot Study.

Mastectomy skin flap necrosis (MSFN) and partial DIEP (deep inferior epigastric artery perforator) flap loss represent two frequently reported complications in immediate autologous breast reconstruction. These complications could be prevented when areas of insufficient tissue perfusion are detected intraoperatively. Hyperspectral imaging (HSI) is a relatively novel, non-invasive imaging technique, which could be used to objectively assess tissue perfusion through analysis of tissue oxygenation patterns (StO2%), near-infrared (NIR%), tissue hemoglobin (THI%), and tissue water (TWI%) perfusion indices. This prospective clinical pilot study aimed to evaluate the efficacy of HSI for tissue perfusion assessment and to identify a cut-off value for flap necrosis. Ten patients with a mean age of 55.4 years underwent immediate unilateral autologous breast reconstruction. Prior, during and up to 72 h after surgery, a total of 19 hyperspectral images per patient were acquired. MSFN was observed in 3 out of 10 patients. No DIEP flap necrosis was observed. In all MSFN cases, an increased THI% and decreased StO2%, NIR%, and TWI% were observed when compared to the vital group. StO2% was found to be the most sensitive parameter to detect MSFN with a statistically significant lower mean StO2% (51% in the vital group versus 32% in the necrosis group, p < 0.0001) and a cut-off value of 36.29% for flap necrosis. HSI has the potential to accurately assess mastectomy skin flap perfusion and discriminate between vital and necrotic skin flap during the early postoperative period prior to clinical observation. Although the results should be confirmed in future studies, including DIEP flap necrosis specifically, these findings suggest that HSI can aid clinicians in postoperative mastectomy skin flap and DIEP flap monitoring.

International survey among surgeons on laparoscopic right hemicolectomy: the gap between guidelines and reality.

INTRODUCTION: To assess the current approaches and perioperative treatments of laparoscopic right hemicolectomy (LRHC) and to highlight similarities and differences with international guidelines and scientific evidence, we conducted a survey for surgeons across the globe. METHODS: All digestive and colorectal surgeons registered with the database of the Research Institute against Digestive Cancer (IRCAD) were invited to take part in the survey via email and through the social media networks of IRCAD. RESULTS: There were a total of 440 respondents from 78 countries. Most surgeons worked in the European region (38.6%) followed by the Americas (34.1%), the Eastern Mediterranean region (13.0%), the South-East Asian region (5.9%), the Western Pacific region (4.8%), and Africa (3.2%) respectively. Over half of the respondents performed less than 25% of right hemicolectomies laparoscopically where 4 ports are usually used by 68% of the surgeons. The medial-to-lateral, vessel-first approach is the approach most commonly used (74.1%). The most common extraction site was through a midline incision (53%) and an abdominal drain tube is routinely used by 52% of the surgeons after surgery. A total of 68.6% of the responding surgeons perform the majority of the anastomoses extracorporeally. Finally, we found that the majority of responders (60.7%) routinely used mechanical bowel preparations prior to LRHC. CONCLUSION: Regarding several topics related to LRHC care, a discrepancy was observed between the current medical practice and the recommendations from RCTs and international guidelines and significant regional differences were observed.

Extracorporeal Membrane Oxygenation Blood Flow and Blood Recirculation Compromise Thermodilution-Based Measurements of Cardiac Output.

The contribution of veno-venous (VV) extracorporeal membrane oxygenation (ECMO) to systemic oxygen delivery is determined by the ratio of total extracorporeal blood flow () to cardiac output (). Thermodilution-based measurements of may be compromised by blood recirculating through the ECMO (recirculation fraction; Rf). We measured the effects of and Rf on classic thermodilution-based measurements of in six anesthetized pigs. An ultrasound flow probe measured total aortic blood flow () at the aortic root. Rf was quantified with the ultrasound dilution technique. was set to 0-125% of and was measured using a pulmonary artery catheter (PAC) in healthy and lung injured animals. PAC overestimated () at all settings compared to . The mean bias between both methods was 2.1 L/min in healthy animals and 2.7 L/min after lung injury. The difference between and increased with an of 75-125%/ compared to QEC <50%/. Overestimation of was highest when resulted in a high Rf. Thus, thermodilution-based measurements can overestimate cardiac output during VV ECMO. The degree of overestimation of depends on the EC/ ratio and the recirculation fraction.

Near infrared fluorescence imaging of the urethra: a systematic review of the literature.

BACKGROUND: Urethral injury is a dreaded complication during laparoscopic, perineal and transanal surgery and is mainly a result of a failed visualization of the urethra. The aim of this systematic review is to provide an overview of the available literature on the near-infrared fluorescence (NIRF) imaging technique using contrast agents for the intra-operative visualization of the urethra. MATERIAL AND METHODS: A systematic review of the literature was conducted including studies on NIRF imaging using contrast agents to visualize the urethra. All studies describing a NIRF imaging technique and demonstrating visual findings of the urethra were included. RESULTS: Five studies were identified. Four studies examined indocyanine green, one of which also studied the IRDye® 800BK agent and one examined the CP-IRT dye. All studies showed that the NIRF imaging technique was feasible for an early identification of the urethra. No complications related to NIRF imaging were reported. CONCLUSION: We conclude that the use of a NIRF imaging technique is feasible and that it can contribute to prevent iatrogenic injury to the urethra. However, based on the limited available data, no solid conclusion can yet be drawn and further translation to the clinical practice is necessary.

In vitro validation and characterization of pulsed inhaled nitric oxide administration during early inspiration.

PURPOSE: Admixture of nitric oxide (NO) to the gas inspired with mechanical ventilation can be achieved through continuous, timed, or pulsed injection of NO into the inspiratory limb. The dose and timing of NO injection govern the inspired and intrapulmonary effect site concentrations achieved with different administration modes. Here we test the effectiveness and target reliability of a new mode injecting pulsed NO boluses exclusively during early inspiration. METHODS: An in vitro lung model was operated under various ventilator settings. Admixture of NO through injection into the inspiratory limb was timed either (i) selectively during early inspiration ("pulsed delivery"), or as customary, (ii) during inspiratory time or (iii) the entire respiratory cycle. Set NO target concentrations of 5-40 parts per million (ppm) were tested for agreement with the yield NO concentrations measured at various sites in the inspiratory limb, to assess the effectiveness of these NO administration modes. RESULTS: Pulsed delivery produced inspiratory NO concentrations comparable with those of customary modes of NO administration. At low (450 ml) and ultra-low (230 ml) tidal volumes, pulsed delivery yielded better agreement of the set target (up to 40 ppm) and inspiratory NO concentrations as compared to customary modes. Pulsed delivery with NO injection close to the artificial lung yielded higher intrapulmonary NO concentrations than with NO injection close to the ventilator. The maximum inspiratory NO concentration observed in the trachea (68 ± 30 ppm) occurred with pulsed delivery at a set target of 40 ppm. CONCLUSION: Pulsed early inspiratory phase NO injection is as effective as continuous or non-selective admixture of NO to inspired gas and may confer improved target reliability, especially at low, lung protective tidal volumes.

Robotic endoscopic cooperative surgery for colorectal tumors: a feasibility study (with video).

BACKGROUND: Laparoscopic endoscopic cooperative colorectal surgery (LECS-CR) is a promising technique to achieve full-thickness resection of colorectal tumors. This approach has shown good rates of complete resection and low local recurrence, especially for large laterally spreading tumors, which are difficult to remove via endoscopy alone. However, it is often difficult to prevent peritoneal leakage of intestinal content, causing infections and risks of cancer spreading. It was hypothesized that a robotic assistance could make the procedure easier and decrease intestinal fluid leakage. This preclinical trial aims to assess the feasibility of robotic and endoscopic cooperative colorectal surgery (RECS-CR). METHODS: LECS-CR was performed in five female pigs and RECS-CR was also performed in five female pigs. With the animal under general anesthesia, pseudotumors were created on the colonic mucosa at a distance comprised between 20 and 25 cm from the anal verge. Desired resection margins were marked endoscopically and two stay sutures were placed either robotically or laparoscopically. A mucosa-to-submucosa dissection was performed endoscopically along the markings. Complete full-thickness dissection was performed cooperatively. The specimen was withdrawn endoscopically. The colon was closed using a self-fixating running suture. Abdominal contaminations, operating times, complications, and complete resections were evaluated and compared between LECS-CR and RECS-CR. RESULTS: The mean number of colonies of Escherichia coli in the RECS group was significantly lower than in the LECS group (36.7 ± 30.2 vs. 142.2 ± 78.4, respectively, p < 0.05). Operating time was comparable (118 ± 11.2 vs. 98.6 ± 25.7, respectively, p = 0.22). Two stenoses occurred in the LECS group. R0 resection was achieved in all cases. CONCLUSION: This study suggests that RECS-CR is feasible and has the potential to reduce intestinal content leakage, potentially preventing postoperative infections.

Automatic Liver Viability Scoring with Deep Learning and Hyperspectral Imaging.

Hyperspectral imaging (HSI) is a non-invasive imaging modality already applied to evaluate hepatic oxygenation and to discriminate different models of hepatic ischemia. Nevertheless, the ability of HSI to detect and predict the reperfusion damage intraoperatively was not yet assessed. Hypoxia caused by hepatic artery occlusion (HAO) in the liver brings about dreadful vascular complications known as ischemia-reperfusion injury (IRI). Here, we show the evaluation of liver viability in an HAO model with an artificial intelligence-based analysis of HSI. We have combined the potential of HSI to extract quantitative optical tissue properties with a deep learning-based model using convolutional neural networks. The artificial intelligence (AI) score of liver viability showed a significant correlation with capillary lactate from the liver surface (r = -0.78, p = 0.0320) and Suzuki's score (r = -0.96, p = 0.0012). CD31 immunostaining confirmed the microvascular damage accordingly with the AI score. Our results ultimately show the potential of an HSI-AI-based analysis to predict liver viability, thereby prompting for intraoperative tool development to explore its application in a clinical setting.

Influence of intraoperative vasopressor use on indocyanine green fluorescence angiography: first evaluation in an experimental model.

Intraoperative indocyanine green (ICG) fluorescence angiography has gained popularity and acceptance in many surgical fields for the real-time assessment of tissue perfusion. Although vasopressors have the potential to preclude an accurate assessment of tissue perfusion, there is a lack of literature with regards to its effect on ICG fluorescence angiography. An experimental porcine model was used to expose the small bowel for quantitative tissue perfusion assessment. Three increasing doses of norepinephrine infusion (0.1, 0.5, and 1.0 µg/kg/min) were administered intravenously over a 25-min interval. Time-to-peak fluorescence intensity (TTP) was the primary outcome. Secondary outcomes included absolute fluorescence intensity and local capillary lactate (LCL) levels. Five large pigs (mean weight: 40.3 ± 4.24 kg) were included. There was no significant difference in mean TTP (in seconds) at baseline (4.23) as compared to the second (3.90), third (4.41), fourth (4.60), and fifth ICG assessment (5.99). As a result of ICG accumulation, the mean and the maximum absolute fluorescence intensity were significantly different as compared to the baseline assessment. There was no significant difference in LCL levels (in mmol/L) at baseline (0.74) as compared to the second (0.82), third (0.64), fourth (0.60), and fifth assessment (0.62). Increasing doses of norepinephrine infusion have no significant influence on bowel perfusion using ICG fluorescence angiography.