Zero-Heat-Flux Thermometry for Non-Invasive Measurement of Core Body Temperature in Pigs

Hypothermia is a severe, unpleasant side effect during general anesthesia. Thus, temperature surveillance is a prerequisite in general anesthesia settings during experimental surgeries. The gold standard to measure the core body temperature (T-core) is placement of a Swan-Ganz catheter in the pulmonary artery, which is a highly invasive procedure. Therefore, T-core is commonly examined in the urine bladder and rectum. However, these procedures are known for their inaccuracy and delayed record of temperatures. Zero-heat-flux (ZHF) thermometry is an alternative, non-invasive method quantifying T-core in human patients by applying a thermosensoric patch to the lateral forehead. Since the porcine cranial anatomy is different to the human's, the optimal location of the patch remains unclear to date. The aim was to compare three different patch locations of ZHF thermometry in a porcine hypothermia model. Hypothermia (33.0 degrees C T-core) was conducted in 11 anesthetized female pigs (26-30kg). T-core was measured continuously by an invasive Swan-Ganz catheter in the pulmonary artery (T-pulm). A ZHF thermometry device was mounted on three different defined locations. The smallest average difference between T-pulm and T-ZHF during stable temperatures was 0.21 +/- 0.16 degrees C at location A, where the patch was placed directly behind the eye. Also during rapidly changing temperatures location A showed the smallest bias with 0.48 +/- 0.29 degrees C. Location A provided the most reliable data for T-core. Therefore, the ZHF thermometry patch should be placed directly behind the left temporal corner of the eye to provide a non-invasive method for accurate measurement of T-core in pigs

In vivo application of tissue-engineered blood vessels of bacterial cellulose as small arterial substitutes: proof of concept?

Background: Tissue-engineered blood vessels (TEBVs) represent an innovative approach for overcoming reconstructive problems associated with vascular diseases by providing small-caliber vascular grafts. This study aimed to evaluate a novel biomaterial of bacterially synthesized cellulose (BC) as a potential scaffold for small-diameter TEBV. Methods: Small-diameter blood vessels with a supramolecular fiber network structure consisting of tubular hydrogels from biodesigned cellulose were created using Gluconacetobacter strains and Matrix reservoir technology. BC tubes (length: 100 mm, inner diameter: 4.0-5.0 mm) were applied to replace the carotid arteries of 10 sheep for a period of 3 mo to gain further insights into (a) functional (in vivo) performance, (b) ability of providing a scaffold for the neoformation of a vascular wall and (c) their proinflammatory potential, and the (d) technical feasibility of the procedure. Results: Preoperative analysis revealed a bursting strength of the grafts of approximately 800 mm Hg and suture retention strength of 4-5 N. Postexplantation analysis showed a patency rate of 50% (n = 5) and physiological performance of the patent grafts at 4, 8, and 12 wk postoperatively, compared with native arteries. Histologic analysis revealed a neoformation of a vascular wall-like structure along the BC scaffold consisting of immigrated vascular smooth muscle cells and a homogeneous endothelialization of the inner graft surface without signs of prothrombogenic or inflammatory potential. Scanning electron microscopy revealed a confluent luminal endothelial cell layer and the immigration of vascular smooth muscle cells into the BC matrix. Conclusions: BC grafts provide a scaffold for the neoformation of a three-layered vascular wall exhibit attractive properties for their use in future TEBV programs for cardiovascular surgery. (C) 2014 Elsevier Inc. All rights reserved

Morphological characterization and immunohistochemical detection of the proinflammatory cytokines IL-1 beta, IL-17A, and TNF-alpha in lung lesions associated with contagious bovine pleuropneumonia

Contagious bovine pleuropneumonia (CBPP), a severe respiratory disease, is characterized by massive inflammation of the lung especially during the acute clinical stage of infection. Tissue samples from cattle, experimentally infected with Mycoplasma mycoides subsp. mycoides Afad,, were subjected to histopathological and immunohistochemical examination in order to provide insight into innate immune pathways that shape inflammatory host responses. Lung lesions were characterized by vasculitis, necrosis, and increased presence of macrophages and neutrophils, relative to uninfected animals. The presence of three cytokines associated with innate inflammatory immune responses, namely, IL-1 beta, IL-17A, and TNF-alpha, were qualitatively investigated in situ. Higher cytokine levels were detected in lung tissue samples from CBPP-affected cattle compared to samples derived from an uninfected control group. We therefore conclude that the cytokines TNF-alpha and IL-1 beta, which are prevalent in the acute phase of infections, play a role in the inflammatory response seen in the lung tissue in CBPP. IL-17A gets released by activated macrophages and attracts granulocytes that modulate the acute phase of the CBPP lesions

Patency and in vivo compatibility of bacterial nanocellulose grafts as small-diameter vascular substitute

Objective: Despite the clinical success of large-diameter vascular grafts, synthetic grafts in small-diameter vessels are of limited use because of their poor patency rates. Previous experiments of our group provided evidence for good biocompatibility of bacterial nanocellulose (BNC) as a small-vessel graft in the carotid artery in sheep. However, the patency rate of our first-generation tubes after 3 months was only 50%. To advance our concept, we now used modified second-generation tubes with diminished wall thickness and a smoother inner surface to reduce the thrombogenic potential. The aim was to investigate mechanical characteristics of modified second-generation BNC tubes, to evaluate in vivo performance and biocompatibility, and to analyze patency rates. Methods: We replaced the right carotid artery of 23 sheep with second-generation BNC tubes. Compared with our first-generation tubes, tubes were modified with different surface properties and diminished wall thickness (inner diameter, 4.0-5.0 mm; wall thickness, 1.0-2.5 mm; length, 100 mm) to generate a smoother inner surface with reduced thrombogenic potential and a more porous outer zone, allowing easier cell immigration. Results: At the end of the investigational period, BNC tubes were explanted and grafts were processed for histopathologic analysis. Histologic analysis revealed no acute signs of foreign body reaction such as immigration of giant cells or other acute inflammatory reaction and therefore provided evidence for good biocompatibility of the second-generation tubes. However, all grafts of the sheep without antiplatelet therapy were occluded after 9 months, whereas grafts in sheep receiving dual platelet inhibition showed a patency rate of 67% (six of nine grafts). Further modified grafts revealed a patency rate of 80% (four of five grafts remained open). Conclusions: Patency rates of the second-generation tubes could be substantially improved compared with our first-generation tubes. However, poor patency rates of tissue-engineered blood vessels still limit their use in clinical studies. Further efforts in terms of in vitro and in vivo studies are essential to improve grafts of BNC. (J Vasc Surg 2018;68:177S-87S.) Clinical Relevance: Despite the clinical success of large-diameter vascular grafts, synthetic grafts in small-diameter vessels (<6 mm) are rarely used because of poor patency rates, which limit their application in peripheral and coronary vascular bypass graft procedures. Hence, nonthrombogenic materials with good biocompatibility and favorable mechanical characteristics that mimic the compliance and strength of the native vessels are required. One promising concept is the use of the hydrogel bacterial nanocellulose designed in tubular shape

A new device to prevent fascial retraction in the open abdomen - proof of concept in vivo

BackgroundAn open abdomen is often necessary for survival of patients after peritonitis, compartment syndrome, or in damage control surgery. However, abdominal wall retraction relieves delays and complicates abdominal wall closure. The principle of the newly fascia preserving device (FPD) is the application of anteriorly directed traction on both fascial edges over an external support through a longitudinal beam to relieve increased abdominal pressure and prevent fascial retraction.MethodsTwelve pigs were randomly divided into two groups. Both groups underwent midline laparotomy under general anesthesia. Group one was treated with the new device, group two served as controls. The tension for closing the abdominal fascia was measured immediately after laparotomy as well as at 24 and 48h. Vital parameters and ventilation pressure were recorded. Post mortem, all fascial tissues were histologically examined.ResultsAll pigs demonstrated increases in abdominal circumference. In both groups, forces for closing the abdomen increased over the observation period. Concerning the central closing force after 24h we saw a significant lower force in the FPD group (14.43N) vs. control group (21.6 +/- 5.7N, p<0.001). By testing the main effects using an ANOVA analysis we found a significant group related effect concerning closing force and abdominal circumference of the FDP-group vs. control group (p<0.001; p<0.001). The placement of the device on chest and pelvis did not influence vital parameters and ventilation pressure. Histologic exam detected no tissue damage.Conclusions This trial shows the feasibility to prevent fascial retraction during the open abdomen by using the new device. Thus, it is expected that an earlier closure of the abdominal wall will be possible, and a higher rate of primary closure will be attained

Experimental Studies for Small Diameter Grafts in an In Vivo Sheep Model-Techniques and Pitfalls

Background Scientific attempts to create the ideal small diameter vascular graft have been compared with the search of the holy grail. Prosthetic material as expanded polytetrafluoroethylene or Dacron shows acceptable patency rates to large caliber vessels, while small diameter (< 6 mm) prosthetic conduits present unacceptably poor patency rates. Vascular tissue engineering represents a promising option to address this problem. Material and Methods Thirty-two female Texel-sheep aged 6 months to 2 years underwent surgical common carotid artery (CCA) interposition using different tissue-engineered vascular substitutes. Explantation of the grafts was performed 12 ( n = 12) and 36 ( n = 20) weeks after surgery. Ultrasound was performed on postoperative day 1 and thereafter every 4 weeks to evaluate the graft patency. Results The average length of implanted substitutes was 10.3 +/- 2.2 cm. Anesthesia and surgical procedure could be performed without major surgical complications in all cases. The grafts showed a systolic blood flow velocity (BFV) of 28.24 +/- 13.5 cm/s, a diastolic BFV of 9.25 +/- 4.53 cm/s, and a mean BFV of 17.85 +/- 9.25 cm/s. Native vessels did not differ relevantly in hemodynamic measurements (systolic: 29.77 cm/s; diastolic: 7.99 cm/s +/- 5.35; mean 15.87 +/- 10.75). There was no incidence of neurologic complications or subsequent postoperative occlusion. Perioperative morbidity was low and implantation of conduits was generally well tolerated. Conclusion This article aims to give a precise overview of in vivo experiments in sheep for the evaluation of small diameter vascular grafts performing CCA interposition, especially with regard to pitfalls and possible perioperative complications and to discuss advantages and disadvantages of this approach

Evaluation of small intestinal damage in a rat model of 6 Minutes cardiac arrest

Abstract Background Contribution of the small intestine to systemic inflammation after cardiac arrest (CA) is poorly understood. The objective was to evaluate whether an in vivo rat model of 6 min CA is suitable to initiate intestinal ischaemia-reperfusion-injury and to evaluate histomorphological changes and inflammatory processes in the small intestinal mucosa resp. in sera. Methods Adult male Wistar rats were subjected to CA followed by cardio-pulmonary resuscitation. Proximal jejunum and serum was collected at 6 h, 24 h, 72 h and 7 d post return of spontaneous circulation (ROSC) and from a control group. The small intestine was evaluated histomorphologically. Cytokine concentrations were measured in jejunum lysates and sera. Results Histomorphological evaluation revealed a significant increase in mucosal damage in the jejunum at all timepoints compared to controls (p < 0.0001). In jejunal tissues, concentrations of IL-1α, IL-1β, IL-10, and TNF-α showed significant peaks at 24 h and were 1.5- to 5.7-fold higher than concentrations at 6 h and in the controls (p < 0.05). In serum, a significant higher amount of cytokine was detected only for IL-1β at 24 h post-ROSC compared to controls (15.78 vs. 9.76 pg/ml). Conclusion CA resulted in mild small intestinal tissue damage but not in systemic inflammation. A rat model of 6 min CA is not capable to comprehensively mimic a post cardiac arrest syndrome (PCAS). Whether there is a vital influence of the intestine on the PCAS still remains unclear