Assessment of Intestinal Ischemia-Reperfusion Injury Using Diffuse Reflectance VIS-NIR Spectroscopy and Histology.

A porcine model was used to investigate the feasibility of using VIS-NIR spectroscopy to differentiate between degrees of ischemia-reperfusion injury in the small intestine. Ten pigs were used in this study and four segments were created in the small intestine of each pig: (1) control, (2) full arterial and venous mesenteric occlusion for 8 h, (3) arterial and venous mesenteric occlusion for 2 h followed by reperfusion for 6 h, and (4) arterial and venous mesenteric occlusion for 4 h followed by reperfusion for 4 h. Two models were built using partial least square discriminant analysis. The first model was able to differentiate between the control, ischemic, and reperfused intestinal segments with an average accuracy of 99.2% with 10-fold cross-validation, and the second model was able to discriminate between the viable versus non-viable intestinal segments with an average accuracy of 96.0% using 10-fold cross-validation. Moreover, histopathology was used to investigate the borderline between viable and non-viable intestinal segments. The VIS-NIR spectroscopy method together with a PLS-DA model showed promising results and appears to be well-suited as a potentially real-time intraoperative method for assessing intestinal ischemia-reperfusion injury, due to its easy-to-use and non-invasive nature.

Utilization of dielectric properties for assessment of liver ischemia-reperfusion injury in vivo and during machine perfusion.

There is a shortage of donor livers and patients consequently die on waiting lists worldwide. Livers are discarded if they are clinically judged to have a high risk of non-function following transplantation. With the aim of extending the pool of available donor livers, we assessed the condition of porcine livers by monitoring the microwave dielectric properties. A total of 21 livers were divided into three groups: control with no injury (CON), biliary injury by hepatic artery occlusion (AHEP), and overall hepatic injury by static cold storage (SCS). All were monitored for four hours in vivo, followed by ex vivo plurithermic machine perfusion (PMP). Permittivity data was modeled with a two-pole Cole-Cole equation, and dielectric properties from one-hour intervals were analyzed during in vivo and normothermic machine perfusion (NMP). A clear increasing trend in the conductivity was observed in vivo in the AHEP livers compared to the control livers. After four hours of NMP, separations in the conductivity were observed between the three groups. Our results indicate that dielectric relaxation spectroscopy (DRS) can be used to detect and differentiate liver injuries, opening for a standardized and reliable point of evaluation for livers prior to transplantation.

Small intestinal viability assessment using dielectric relaxation spectroscopy and deep learning.

Intestinal ischemia is a serious condition where the surgeon often has to make important but difficult decisions regarding resections and resection margins. Previous studies have shown that 3 h (hours) of warm full ischemia of the small bowel followed by reperfusion appears to be the upper limit for viability in the porcine mesenteric ischemia model. However, the critical transition between 3 to 4 h of ischemic injury can be nearly impossible to distinguish intraoperatively based on standard clinical methods. In this study, permittivity data from porcine intestine was used to analyze the characteristics of various degrees of ischemia/reperfusion injury. Our results show that dielectric relaxation spectroscopy can be used to assess intestinal viability. The dielectric constant and conductivity showed clear differences between healthy, ischemic and reperfused intestinal segments. This indicates that dielectric parameters can be used to characterize different intestinal conditions. In addition, machine learning models were employed to classify viable and non-viable segments based on frequency dependent dielectric properties of the intestinal tissue, providing a method for fast and accurate intraoperative surgical decision-making. An average classification accuracy of 98.7% was obtained using only permittivity data measured during ischemia, and 96.2% was obtained with data measured during reperfusion. The proposed approach allows the surgeon to get accurate evaluation from the trained machine learning model by performing one single measurement on an intestinal segment where the viability state is questionable.

Association between patient classification systems and nurse staffing costs in intensive care units: An exploratory study.

OBJECTIVES: Nurse staffing costs represent approximately 60% of total intensive care unit costs. In order to analyse resource allocation in intensive care, we examined the association between nurse staffing costs and two patient classification systems: the nursing activities score (NAS) and nine equivalents of nursing manpower use score (NEMS). RESEARCH METHODOLOGY/DESIGN: A retrospective descriptive correlational analysis of nurse staffing costs and data of 6390 patients extracted from a data warehouse. SETTING: Three intensive care units in a university hospital and one in a regional hospital in Norway. MAIN OUTCOME MEASURES: Nurse staffing costs, NAS and NEMS. RESULTS: For merged data from all units, the NAS was more strongly correlated with monthly nurse staffing costs than was the NEMS. On separate analyses of each ICU, correlations were present for the NAS on basic costs and external overtime costs but were not significant. The annual mean nurse staffing cost for 1% of NAS was 20.9-23.1 euros in the units, which was comparable to 53.3-81.5 euros for 1 NEMS point. CONCLUSION: A significant association was found between monthly costs, NAS, and NEMS. Cost of care should be based on individual patients' nursing care needs. The NAS makes nurses' workload visible and may be a helpful classification system in future planning and budgeting of intensive care resources.

Open versus laparoscopic liver resection for colorectal liver metastases (the Oslo-CoMet Study): study protocol for a randomized controlled trial.

BACKGROUND: Laparoscopic liver resection is used in specialized centers all over the world. However, laparoscopic liver resection has never been compared with open liver resection in a prospective, randomized trial. METHODS/DESIGN: The Oslo-CoMet Study is a randomized trial into laparoscopic versus open liver resection for the surgical management of hepatic colorectal metastases. The primary outcome is 30-day perioperative morbidity. Secondary outcomes include 5-year survival (overall, disease-free and recurrence-free), resection margins, recurrence pattern, postoperative pain, health-related quality of life, and evaluation of the inflammatory response. A cost-utility analysis of replacing open surgery with laparoscopic surgery will also be performed. The study includes all resections for colorectal liver metastases, except formal hemihepatectomies, resections where reconstruction of vessels/bile ducts is necessary and resections that need to be combined with ablation. All patients will participate in an enhanced recovery after surgery program. A biobank of liver and tumor tissue will be established and molecular analysis will be performed. DISCUSSION: After 35 months of recruitment, 200 patients have been included in the trial. Molecular and immunology data are being analyzed. Results for primary and secondary outcome measures will be presented following the conclusion of the study (late 2015). The Oslo-CoMet Study will provide the first level 1 evidence on the benefits of laparoscopic liver resection for colorectal liver metastases. TRIAL REGISTRATION: The trial was registered in ClinicalTrals.gov (NCT01516710) on 19 January 2012.

The assessment of potentially interfering metabolites and dietary components in blood using an osmotic glucose sensor based on the concanavalin A-dextran affinity assay.

Continuous surveillance of blood glucose is a prerogative of maintaining a tight glycaemic control in people suffering from diabetes mellitus. Implantable sensor technology offers the potential of conducting direct long term continuous glucose measurements, but current size restrictions and operational challenges have limited their applications. The osmotic sensor utilises diffusion to create a hydrostatic pressure that is independent of sensor operation and power consumption. This permits ultra-low power architectures to be realized with a minimal start-up time in a package suitable for miniaturization. In contrast, osmotic sensors suffer from the inability of their membranes to discriminate between different constituents in blood or the interstitial fluid that are of comparable size to glucose. By implementing an affinity assay based on the competitive bonding between concanavalin A and dextran, the selectivity of the membrane can be transferred to the glucose specific recognition of the affinity assay. The osmotic effect from the physiological levels of several key metabolites and nutritional components has been addressed identifying in particular ethanol, lactate and amino acids as potential interfering constituents. Both ascorbic acid and mannose would have a normal physiological concentration that is too low to be detected. The studies shows that an osmotic glucose sensor equipped with the con A-dextran affinity assay, is able to filter out potential interfering constituents present in blood, plasma and the interstitial fluid yet retaining a pressure that is proportional to glucose only.

Detection of ischemia and new insight into left ventricular physiology by strain Doppler and tissue velocity imaging: assessment during coronary bypass operation of the beating heart.

BACKGROUND AND OBJECTIVES: Detection of myocardial ischemia in humans by strain Doppler and tissue velocity imaging was validated in a novel, experimentally designed study model during coronary bypass operation of the beating heart. METHODS: Assessment of ischemia was made with an opened chest and pericardium inherent in the operative procedure. Longitudinal strain and tissue velocity of interventricular septal regions were measured by transesophageal echocardiography during occlusion of the left anterior descending coronary artery (LAD). RESULTS: Unexpectedly, baseline velocities demonstrated that the apical and basal septum moved toward each other during systole. This occurred when the apex was dislodged from the pericardial sac to obtain access to the LAD, without any change in strain. The preceding motion of all septal regions toward the apex was reestablished after the heart was repositioned within the pericardium. In 16 patients with antegrade LAD flow, strain Doppler detected ischemia during LAD occlusion by disclosing systolic lengthening of the apical septum ( P <.01) and reduced shortening of the mid septum ( P <.05). The location and degree of ischemic changes coincided with the concomitant deterioration of wall motion. Tissue velocity changed in the basal and mid septum ( P <.05) but not in the apical region, explained by tethering effects and the distinctive motion pattern at baseline. There was no evidence of ischemia by invasive hemodynamic measures. In 7 patients with retrograde LAD flow, there were no significant changes in strain or tissue velocity measurements during LAD occlusion. CONCLUSIONS: Strain by Doppler is a sensitive means for detecting myocardial ischemia, also capable of correctly localizing the ischemia, as opposed to tissue velocity assessment. However, velocity measurements provided new physiological information by disclosing the normal longitudinal motion of the heart to be dependent on the pericardial sac enveloping the apex, irrespective of the structural integrity of the pericardium.