In-vitro and in-vivo measurement of the animal's middle ear acoustical response by partially implantable fiber-optic sensing system.

The main obstacle in realization of a totally implantable hearing aid is a lack of reliable implantable microphone. In this paper we have described a potentially miniature fiber-optic vibrometer based on a modified Michelson interferometer, designed to serve as a middle-ear microphone for totally implantable cochlear- or middle-ear hearing aids. A model of the sensing system was used for in-vitro and in-vivo investigation of acoustical response of sheep's middle-ear ossicles. Surgical and implantation procedure of introducing the sensing optical fiber into the middle-ear and its aiming at the incus was investigated and described here in detail. The frequency responses of the incus was measured while a cadaver and living sheep was exposed to the sinusoidal acoustical excitation of 40-90dB SPL, in the frequency range from 100Hz to 10kHz. The amplitude of the incus vibration was found to be in the range between 10pm to 100nm, strongly depending on the frequency, with a lot of resonant peaks, corresponding mainly to the natural outer ear canal gain. The noise floor in the experiments was about 2pm/Hz1/2, but recently we have decreased it to < 0.5pm/Hz1/2, which corresponds to a minimal detectable sound level of 31-35dB(A) SPL for humans. The histological examination of temporal bones of cadaver animals and the intensity of in-vivo optical signal demonstrated that the aiming of the sensing fiber to the target has been preserved for five months after the implantation.

Bioelectrical signals improve cardiac function and modify gene expression of extracellular matrix components.

AIMS: Beyond the influence of stimulating devices on cardiac excitation, their use in treating patients with heart failure has positive effects on the myocardium at the molecular level. Electrical signals can induce a wide spectrum of effects in living tissue. Therefore, we sought to determine whether applying electrical microcurrent directly to failing hearts leads to functional improvement. METHODS AND RESULTS: Sixteen male spontaneously hypertensive rats (SHRs) with heart failure underwent application of a patch electrode to the left ventricular epicardium and placement of a subcutaneous counter electrode. The electrode delivered a 0.35 µA microcurrent to nine of the SHRs for 45 ± 3 days; the other seven SHRs were used as controls. At baseline and before the SHRs were humanely put to death, we measured the left ventricular ejection fraction (LVEF) and the thickness of the LV posterior wall during systole and diastole (LVPWs/d). We used quantitative PCR to determine extracellular matrix parameters [collagen I-III, matrix metalloproteinase (MMP)-2, MMP-9, tissue inhibitor of metalloproteinases 3 (TIMP3), TIMP4, connexins (Cxs) 40/43/45, transforming growth factor (TGF)-ß, and interleukin (IL)-6]. Among SHRs undergoing microcurrent application, LVEF normalized (mean decrease, 22.8%; P = 0.009), and LVPWs decreased (mean, 35.3%; P = 0.001). Compared with the control group, the SHRs receiving microcurrent exhibited a mean decrease in the gene expression of collagen I (10.6%, P = 0.003), TIMP3 (18.5%, P = 0.005), Cx43 (14.3%, P = 0.003), Cx45 (12.7%, P = 0.020), TGF-ß (13.0%, P = 0.005), and IL-6 (53.7%, P = 0.000). Microcurrent application induced no changes in the expression of collagen III, MMP-2, MMP-9, TIMP4, or Cx40. CONCLUSIONS: Applying microcurrent to the LV epicardium of SHRs leads to statistically significant functional improvement and alterations in the levels of inflammatory and extracellular matrix components.

Microcurrent stimulation promotes reverse remodelling in cardiomyocytes.

AIMS: It has been shown that electrical stimulation can improve tissue repair in patients. Imbalances in the extracellular matrix composition induce manifestation of heart failure. Here we investigated the application of microcurrent (MC) to modulate the expression of matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) in cardiomyocytes in vitro and in vivo to reverse remodelling in the heart in spontaneous hypertensive rats (SHR). METHODS: Cardiomyocytes from young SHR (7 months) and old SHR (14 months) were stimulated in vitro and in vivo with MC. MMP and TIMP expression were analysed by qPCR and immunofluorescence to evaluate the modulation of MC treatment. RESULTS: Modulation of cardiomyocytes with MC enhances proliferation with no morphological changes in vitro. By electrical stimulation dual effects, increase and decrease, on MMP-2, MMP-9, TIMP-3, and TIMP-4 mRNA as well as protein expression were observed, depending on the age of the cardiomyocytes. In our in vivo study, MC down-regulated MMP-2, MMP-9, and TIMP-4 and increased TIMP-3 in young SHR. In old SHR MMP-2, MMP-9, and TIMP-4 were up-regulated, whereas TIMP-3 was unaffected. CONCLUSIONS: Our data indicate that treatment of MC can modulate the expression of MMPs and TIMPs in vitro and in vivo in SHR. Based on these results new treatments for heart failure could be developed.

Establishment and characterization of a primary and a metastatic melanoma cell line from Grey horses.

The Grey horse phenotype, caused by a 4.6 kb duplication in Syntaxin 17, is strongly associated with high incidence of melanoma. In contrast to most human melanomas with an early onset of metastasis, the Grey horse melanomas have an extended period of benign growth, after which 50% or more eventually undergo progression and may metastasize. In efforts to define changes occurring during Grey horse melanoma progression, we established an in vitro model comprised of two cell lines, HoMel-L1 and HoMel-A1, representing a primary and a metastatic stage of the melanoma, respectively. The cell lines were examined for their growth and morphological characteristics, in vitro and in vivo oncogenic potential, chromosome numbers, and expression of melanocytic antigens and tumor suppressors. Both cell lines exhibited malignant characteristics; however, the metastatic HoMel-A1 showed a more aggressive phenotype characterized by higher proliferation rates, invasiveness, and a stronger tumorigenic potential both in vitro and in vivo. HoMel-A1 displayed a near-haploid karyotype, whereas HoMel-L1 was near-diploid. The cell lines expressed melanocytic lineage markers such as TYR, TRP1, MITF, PMEL, ASIP, MC1R, POMC, and KIT. The tumor suppressor p53 was strongly expressed in both cell lines, while the tumor suppressors p16 and PTEN were absent in HoMel-A1, potentially implicating significance of these pathways in the melanoma progression. This in vitro model system will not only aid in understanding of the Grey horse melanoma pathogenesis, but also in unraveling the steps during melanoma progression in general as well as being an invaluable tool for development of new therapeutic strategies.

Rapid induction of hypothermia with a small volume aortic flush during cardiac arrest in pigs.

PURPOSE: The induction of deep cerebral hypothermia (15°C) via large-volume cold (4°C) saline aortic flush during cardiac arrest and resuscitation with cardiopulmonary bypass improves neurologic outcome in pigs. We hypothesized that induction of mild cerebral hypothermia (33°C) via smaller volume and resuscitation without bypass will improve survival and neurologic outcome after 15 minutes of cardiac arrest as compared with conventional resuscitation attempts. BASIC PROCEDURES: Twenty-four pigs (29-38 kg) underwent ventricular fibrillation cardiac arrest for 15 minutes. Conventional resuscitation (n=8) was compared with hypothermic (4°C, n=8) and normothermic (38.5°C, n=8) aortic flush (30 mL/kg) at the beginning of resuscitation efforts, with defibrillation attempts 2 minutes later. Outcomes after 9 days were compared. MAIN FINDINGS: In the hypothermic flush group, brain temperature decreased from 38.3°C±0.5°C to 33°C±0.5°C within 277±112 seconds. We observed considerably higher mean coronary perfusion pressures in the normothermic and hypothermic flush groups (hypothermic vs conventional, P=.023; normothermic vs conventional, P=.041). Three animals of each flush group, compared with none of the conventional group, achieved restoration of spontaneous circulation (P=.2); and 3 pigs of the hypothermic flush group and 2 pigs of the normothermic flush group survived to 9 days without differences in neurologic outcome. PRINCIPAL CONCLUSION: A smaller volume, cold saline aortic flush during prolonged cardiac arrest rapidly induces mild cerebral hypothermia to 33°C and improves coronary perfusion pressure but does not result in a significant improvement in outcome as compared with conventional resuscitation attempts.

Electrospun small-diameter polyurethane vascular grafts: ingrowth and differentiation of vascular-specific host cells.

No small-diameter synthetic graft has yet shown comparable performance to autologous vessels. Synthetic conduits fail due to their inherent surface thrombogenicity and the development of intimal hyperplasia. In addressing these shortcomings, electrospinning offers an interesting alternative to other nanostructured, cardiovascular substitutes because of the close match of electrospun materials to the biomechanical and structural properties of native vessels. In this study, we investigated the in vivo behavior of electrospun, small-diameter conduits in a rat model. Vascular grafts composed of polyurethane were fabricated by electrospinning. Prostheses were implanted into the abdominal aorta in 40 rats for either 7 days, 4 weeks, 3 months, or 6 months. Retrieved specimens were evaluated by histology, immunohistochemical staining, confocal laser scanning microscopy, and scanning electron microscopy. At all time points, we found no evidence of foreign body reaction or graft degradation. The overall patency rate of the intravascular implants was 95%. Within 7 days, grafts revealed ingrowth of host cells. CD34+ cells increased significantly from 7 days up to 6 months of implantation (P < 0.05). Myofibroblasts and myocytes showed increasing cell numbers up to 3 months (P < 0.05). Ki67 staining indicated unaltered cell proliferation during the whole follow-up period. Besides biomechanical benefits, electrospun polyurethane grafts exhibit excellent biocompatibility in vivo. Cell immigration and differentiation seems to be promoted by the nanostructured artificial matrix.

New conventional long-term survival normovolemic cardiac arrest pig model.

AIM OF THE STUDY: A reproducible long-term intensive care and outcome cardiac arrest model for exploring new cerebral preservation strategies is needed. We tried to determine effects and limitations of current therapies after different 'no-flow' times. METHODS: Thirty-five female Large White Breed pigs (26-37kg) were included in the study. Three pigs served as sham animals without cardiac arrest (CA). Ventricular fibrillation (VF) CA was induced in 32 animals for 0, 7, 10 and 13min (each group consisting of 8 animals), followed by 8min of chest compressions, mechanical ventilation and vasopressors. Thereafter, up to 3 defibrillations were delivered. After restoration of spontaneous circulation (ROSC), the animals underwent intensive care for 20h. Neurologic examination was performed at designated time points using a neurologic deficit (ND) and an overall performance category (OPC) score. RESULTS: Restoration of spontaneous circulation was achieved in 8 of 8 animals in the 0min-group, 6 of 8 in the 7min-group, 7 of 8 in the 10min-group and 0 of 8 in the 13min-group. All animals of the sham-group and 0min-group were neurologically intact survivors; the 7 and 10min-groups showed a median ND of 55%(26;94) and 73%(58;78), respectively. There were no significant differences between the 7 and 10min-groups regarding OPC and NDS. Coronary perfusion pressure during CPR decreased concordantly with 'no-flow' times with a tendency towards significance. CONCLUSION: This study established a reproducible cardiac arrest and resuscitation model in pigs which will be used to test novel resuscitation strategies to improve neurologic outcome after cardiac arrest.

The importance of surface area for the cooling efficacy of mild therapeutic hypothermia.

AIM OF THE STUDY: Mild hypothermia after cardiac arrest should be induced as soon as possible. There is a need for improved feasibility and efficacy of surface cooling in ambulances. We investigated which and how much area of the body surface should be covered to guarantee a sufficient cooling rate. METHODS: Each of five adult, human-sized pigs (88-105kg) was randomly cooled in three phases with pads that covered different areas of the body surface corresponding to humans (100% or 30% [thorax and abdomen] or 7% [neck]). The goal was to quickly lower brain temperature (Tbr) from 38 to 33°C within a maximum of 120min. Linear regression analysis was used to test the association between cooling efficacy and surface area. Data are presented as mean±standard deviation. RESULTS: The 100% and 30% cooling pads decreased the pigs' Tbr from 38 to 33°C within 33±7min (8.2±1.6°C/h) and 92±24min (3.6±1.1°C/h). The 7% achieved a final Tbr of 35.8±0.7°C after 120min (1.1±0.4°C/h). The 30% and 7% cooling surface areas achieved 37±11% and 15±7% of the cooling rate compared to the 100% cooling pads. For every additional percent of surface area cooled, the cooling rate increased linearly by 0.07°C/h (95% CI 0.05-0.09, p=0.001). No skin lesions were observed. CONCLUSIONS: The cooling pads were effective and safe for rapid induction of mild hypothermia in adult, human-sized pigs, depending on the percentage of body surface area covered. Covering only the neck, chest, and abdomen might achieve satisfactory cooling rates.

Comparison of surface cooling and invasive cooling for rapid induction of mild therapeutic hypothermia in pigs--effectiveness of two different devices.

AIM OF THE STUDY: The effectiveness and safety of non-invasive surface cooling was compared to invasive endovascular cooling in an animal model. METHODS: Eight healthy pigs (29-38 kg) were cooled twice, starting in the first 4 pigs with unique surface cooling pads followed by endovascular cooling. In the second 4 pigs the order was reversed. The goal was to quickly lower pulmonary artery temperature from 38 to 33°C. A paired t-test was used to compare cooling rates (°C/h, mean±standard deviation) between both cooling techniques. RESULTS: Mean non-invasive surface cooling rate (11.9±3.8°C/h) significantly exceeded mean invasive cooling rate (3.9±0.7°C/h; p<0.001). The mean difference in cooling rates was 8.0±3.6°C/h. No surface cooling related adverse skin reactions were observed. CONCLUSIONS: Surface cooling is a simple method for achieving fast cooling rates. In our animal model, non-invasive cooling was three times faster than rapid endovascular cooling without overshoot.

Distribution of neuropathological lesions in pig brains after different durations of cardiac arrest.

AIM OF THE STUDY: To evaluate all brain regions reported to be selectively vulnerable to global ischaemia in a pig cardiac arrest model with different durations of no-flow by establishing a semi-quantitative brain histopathologic scoring system and to compare histological damage with neurological deficits. METHODS: In a prospective randomised laboratory investigation, 35 female Large White pigs weighing 35-45 kg underwent ventricular fibrillation cardiac arrest for 0, 7, 10 or 13 min. In the brains of all animals that survived until the final endpoint (72 h post-arrest), 22 distinct regions were evaluated on paraffin-embedded sections in terms of type and extent of lesions. The results of the histological examination were compared to the results of a neurological outcome evaluation after 72 h. RESULTS: Significant differences were found in all cortex regions, the caudate nucleus and putamen, the hippocampal formation, the cerebellar cortex, and the thalamus between the ischaemic groups (7- and 10-min groups) and the control group (0-min group). No 13-min group animal survived. The main findings were neuronal necrosis and oedema. In animals from the 10-min group, many neurons were reabsorbed in the cerebral cortex, caudate nucleus and cerebellar granule cell layer. There was a highly significant correlation between histological damage and neurological deficits. CONCLUSIONS: The pattern of neuronal lesions in this pig model bear good resemblance to the pattern known in humans and other animal models. The amount of histological lesions in selectively vulnerable brain regions correlates to neurological outcome.

Cold aortic flush and chest compressions enable good neurologic outcome after 15 mins of ventricular fibrillation in cardiac arrest in pigs.

OBJECTIVE: The induction of deep cerebral hypothermia via ice-cold saline aortic flush during prolonged ventricular fibrillation cardiac arrest, followed by hypothermic stasis and delayed resuscitation (emergency preservation and resuscitation), improved neurologic outcome after cardiac arrest in pigs, as compared to conventional resuscitation. We hypothesized that emergency preservation and resuscitation with chest compressions would further improve outcome in the same model. DESIGN: Prospective experimental study. SETTING: University research laboratory. SUBJECTS: : Twenty-four female, large, white breed pigs (27-37 kg). INTERVENTIONS: Fifteen minutes of ventricular fibrillation cardiac arrest were followed by 20 mins of resuscitation with chest compressions (control, n = 8), deep cerebral hypothermia via 200 mL/kg 4 degrees C saline aortic flush and hypothermic stasis (emergency preservation and resuscitation, n = 8), and emergency preservation and resuscitation combined with chest compressions (emergency preservation and resuscitation plus chest compressions, n = 8). At 35 mins after cardiac arrest, cardiopulmonary bypass was initiated, followed by defibrillation. Mild hypothermia was continued for 20 hrs. Pigs were evaluated after 9 days using a neurologic deficit (neurologic deficit score: 100% = brain dead; 0%-10% = normal) and an overall performance category score (overall performance category score: 1 = normal; 2 = slightly handicapped; 3 = severely handicapped; 4 = comatose; 5 = dead/brain dead). MEASUREMENTS AND MAIN RESULTS: Brain temperature decreased from 38.5 degrees C to 15.3 degrees C +/- 3.3 degrees C in the emergency preservation and resuscitation group, and to 11.3 degrees C +/- 1.2 degrees C in the emergency preservation and resuscitation plus chest compressions group. In the control group, restoration of spontaneous circulation was achieved in four out of eight pigs, and one survived to 9 days. In the emergency preservation and resuscitation group, restoration of spontaneous circulation was achieved in seven out of eight pigs and five survived; in the emergency preservation and resuscitation plus chest compressions group, all had restoration of spontaneous circulation and seven survived (restoration of spontaneous circulation, p = .08). Neurologic outcome for (median and interquartile range) the control group included overall performance category score of 3, neurologic deficit score of 45%; for the emergency preservation and resuscitation group, overall performance category score was 3 (2-5) and neurologic deficit score was 45% (36; 50) and in the emergency preservation and resuscitation plus chest compressions group, overall performance category score was 2 (1-3) and neurologic deficit score was 13% (5; 21) (overall performance category score, p = .04; neurologic deficit score emergency preservation and resuscitation vs. emergency preservation and resuscitation plus chest compressions, p = .003). CONCLUSIONS: Emergency preservation and resuscitation by deep cerebral hypothermia combined with chest compressions during prolonged cardiac arrest in pigs are feasible and improve neurologic outcome.

Tracheal temperature for monitoring body temperature during mild hypothermia in pigs.

AIM OF THE STUDY: Out-of-hospital induction of mild therapeutic hypothermia after cardiac arrest needs easy to use and accurate body temperature monitoring. The aim of the study was to evaluate the best temperature probe position on a specially designed tracheal tube, as compared to pulmonary artery temperature (Tpa) during cooling to mild hypothermia in pigs. METHODS: Eight swine (29-38 kg) were anesthetized and intubated with an endotracheal tube with three temperature probes: T1 was attached to the wall of the tube, 1cm proximal to the cuff-balloon, without contact to the mucosa; T2 and T3 were placed on the cuff-balloon with tight contact to the mucosa, T3 was covered by a small plastic tube to protect the mucosa against mechanical alterations. Body temperature was measured with a pulmonary artery catheter. Pigs were cooled from Tpa 38.5 to 33.0 degrees C with fast surface and slow endovascular cooling in a crossover design. To assess hysteresis, areas under the curve (AUC) were compared. Data are presented as mean and 95% confidence intervals. RESULTS: Temperatures were not different either during fast surface (T1-Tpa: 0.1[-0.3 to 0.5] degrees C, T2-Tpa: 0.2[0.0 to 0.4] degrees C, T3-Tpa: 0.4[0.1 to 0.7] degrees C) or slow endovascular (T1-Tpa: -0.3[-0.5 to 0.2] degrees C, T2-Tpa: -0.1[-0.3 to 0.0] degrees C, T3-Tpa: -0.1[-0.5 to 0.3] degrees C) cooling. There was no difference in hysteresis related to the location of the temperature probes. Faster surface cooling correlated with a larger but not significantly different hysteresis between the probes. CONCLUSIONS: Tracheal temperature is an accurate surrogate for body temperature during fast and slow cooling to mild hypothermia in pigs and regardless of the location of the temperature probe on the tube.

Outcome after resuscitation using controlled rapid extracorporeal cooling to a brain temperature of 30 degrees C, 24 degrees C and 18 degrees C during cardiac arrest in pigs.

AIM OF THE STUDY: To identify the optimal level of hypothermia during cardiac arrest, just prior to resuscitation with an extracorporeal cooling system and without fluid overload, for neurological outcome at day 9 in pigs. METHODS: In a prospective randomised laboratory investigation, 24 female Large White pigs (31-38 kg) underwent ventricular-fibrillation cardiac arrest for 15 min, followed by 1 min, 3 min or 5 min (n=8 per group) of 4 degrees C cooling with an extracorporeal cooling system via an aortic balloon catheter and resuscitation with cardiopulmonary bypass. Sixty minutes following induction of cardiac arrest, defibrillation attempts were started. Mild hypothermia (34.5 degrees C) and intensive care were continued for 20 h and final outcome was evaluated after 9 days. RESULTS: Brain temperature decreased from 38.5 degrees C to 30.4+/-1.6 degrees C within 221+/-81 s in the 1-min group; to 24.2+/-4.6 degrees C within 375+/-127 s in the 3-min group; and to 18.8+/-4.0 degrees C within 450+/-121 s in the 5-min group. Restoration of spontaneous circulation was achieved in seven (1-min group), six (3-min group) and six (5-min group) animals (p=0.78), whereas survival to 9 days was only achieved in six, three and three animals in each group (p=0.22), respectively. CONCLUSIONS: An extracorporeal cooling system rapidly induced brain hypothermia following prolonged normovolaemic cardiac arrest in pigs. Difference in outcome was not statistically significant amongst the three groups with various levels of hypothermia (30 degrees C, 24 degrees C and 18 degrees C) during cardiac arrest prior to resuscitation; however, the animals with the least temperature reduction showed a trend to better survival at 9 days. Further studies are necessary to investigate optimised methods for induction, as well as level, of cerebral hypothermia.

Decellularized, xenogeneic small-diameter arteries: transition from a muscular to an elastic phenotype in vivo.

Reports regarding the biocompatibility of xenogeneic, decellularized bioprosthetic implants differ between bioinertness and complete graft degradation. We investigated heparin-crosslinked and nonheparinized, xenogeneic vascular substitutes in a rat model. Porcine arteries (15 x 1.5 mm) were decellularized by multistep detergent and enzymatic techniques, which were followed by heparin-crosslinking in 50% of the implants. Prostheses were implanted into the abdominal aorta of 76 rats for 1 day and up to 6 months. Retrieved specimens were evaluated by histology, immunohistochemistry, laser scanning, and scanning electron microscopy. Graft patency did not differ between groups (97.3%). Heparinized grafts showed a statistically significant lower rate of aneurysm formation (p = 0.04 %). Implants revealed infiltration with granulocytes and macrophages up to 3 months. Recellularization with endothelial cells and myofibroblasts was detectable within 1 month. After 6 months elastin biosynthesis and complete graft remodeling toward an elastic vessel was evident. These results indicate that temporary inflammation does not interfere with long-term vascular remodeling.

Therapeutic hypothermia with a novel surface cooling device improves neurologic outcome after prolonged cardiac arrest in swine.

OBJECTIVE: Devices for rapid induction of mild hypothermia after cardiac arrest are needed. We hypothesized that the Life Recovery Systems' ThermoSuit System provides effective core cooling by pumping ice water over the skin surface and improves neurologic outcome after prolonged cardiac arrest. DESIGN: Prospective experimental study. SETTING: University research laboratory. SUBJECTS: Large White breed pigs (29 to 35 kg). INTERVENTIONS: Swine were anesthetized and mechanically ventilated. Ten minutes of untreated ventricular fibrillation, 3 mins of basic life support, and 5 mins of advanced cardiac life support, including two 0.4 IU/kg doses of vasopressin, were followed by up to three countershocks. After restoration of spontaneous circulation, swine were randomized to two groups (normothermic control, hypothermia). The hypothermia group was cooled from a pulmonary artery temperature of 38.5 +/- 0.5 degrees C to 33.0 degrees C and kept for 14 hrs. At day 9 of the experiment, overall performance categories scores (1, normal; 2, slightly disabled; 3, severely disabled; 4, comatose; 5, dead, brain dead) and neurologic deficit scores (0%, normal; 100%, brain dead) were assessed. Data are presented as median and interquartile range; group comparison was done with a Mann-Whitney U test. MEASUREMENTS AND MAIN RESULTS: In total, 16 of 22 animals were randomized. Time to target temperature in the hypothermia group (n = 8) was 9.0 (5.3-11.9) mins (cooling rate 0.4 [0.3-0.8] degrees C/min), and all animals achieved an overall performance categories score of 1. In the control group, one swine achieved an overall performance categories score of 1, three achieved a score of 2, and four achieved a score of 3 (p = .002). Neurologic deficit score was 0% (0%-4%) in the hypothermia group and 39% (19%-55%) in the control group (p = .001). No harmful side effects could be observed. CONCLUSIONS: The Life Recovery Systems' ThermoSuit System rapidly and safely induced mild therapeutic hypothermia. Hypothermia improved neurologic outcome in swine after cardiac arrest as compared with normothermia. Further studies are warranted to compare the device with established cooling methods.

Experimental stent-graft treatment of ascending aortic dissection.

BACKGROUND: This study assessed the feasibility of stent graft treatment of ascending aortic dissections in a porcine in vitro model. METHODS: The entire thoracic aortic aorta including the supraaortic branches was harvested from 12 adult pigs and an intimal tear was artificially created. The aortic annulus was then sewn into a silicon ring of a driving chamber. The distal aorta was connected to tubing with adjustable resistance elements. The circulation was driven by a hydraulic motor piston pump to mimic aortic flow and pressure. After creating a dissection by elevating the systolic aortic pressure to 180 mm Hg, a 2- x 2.6-cm covered stent graft was inserted through the brachiocephalic trunk using a specially designed delivery system. Stent graft placement was performed under continuous ultrasound control. RESULTS: The longitudinal length of the created ascending aortic dissection was 1.8 +/- 0.39 cm. Ultrasound studies revealed successful deployment of the stent graft and closure of the false lumen in all 12 cases. Diameter and area of the true lumen increased from 0.52 +/- 0.15 cm to 2.54 +/- 0.36 cm (p < 0.05) and from 0.78 +/- 0.27 cm2 to 5.13 +/- 1.35 cm2 (p < 0.05), respectively. The circumference of the true lumen increased from 4.50 +/- 0.52 cm to 7.96 +/- 1.2 cm (p < 0.05). Ultrasound studies also revealed uncompromised function of the aortic valve in all cases. No dislodging of stent grafts was observed. CONCLUSIONS: Given ideal anatomy, experimental stent graft placement for ascending aortic dissection is feasible and achieves complete closure of the false lumen.

S-nitroso human serum albumin reduces ischaemia/reperfusion injury in the pig heart after unprotected warm ischaemia.

AIMS: Uncoupled endothelial nitric oxide synthase (eNOS) is a major contributor to vascular reactive oxygen species generation in ischaemia/reperfusion (I/R) injury. Supplementation of NO by the novel NO donor S-nitroso human serum albumin (S-NO-HSA) may inhibit uncoupling of eNOS (feedback inhibition). METHODS AND RESULTS: Pigs (n = 14; 33.1 +/- 1.7 kg) were continuously monitored for heart rate (HR), mean arterial pressure (MAP), left ventricular systolic pressure (LVSP), and coronary flow (CF). Infusion of either human serum albumin (n = 8; controls) or S-NO-HSA (n = 6) lasted 60 min (0.1 micromol/kg/h) starting 15 min prior to ischaemia. After clamping the aorta under cardiopulmonary bypass (CPB), the hearts underwent 15 min of warm, unprotected ischaemia (37 degrees C). Reperfusion lasted 150 min (30 min under CPB; 15 min weaning; additional 105 min reperfusion). In biopsies from non-ischaemic hearts and myocardial biopsies taken after 150 min of reperfusion, high-energy phosphates were measured and the calcium ionophore-stimulated release of NO, superoxide, and peroxynitrite (ONOO(-)) were monitored with nanosensors. Compared with non-ischaemic hearts, the NO level decreased from 930 +/- 25 to 600 +/- 15 nmol/L (P < 0.001) while the superoxide level increased from 45 +/- 5 to 110 +/- 10 nmol/L (P < 0.001) after ischaemia. S-NO-HSA restored the NO level to 825 +/- 20 nmol/L, shifted favourably the [NO]/[ONOO(-)] balance (a marker of eNOS uncoupling) from 1.36 +/- 0.06 (ischaemia) to 3.59 +/- 0.18, significantly improved CF (65 +/- 10 vs. control, 43 +/- 5 mL/min, P < 0.05), MAP (57 +/- 5 vs. 39 +/- 3 mm Hg, P < 0.01), LVSP (106 +/- 5 vs. 81 +/- 4 mm Hg, P < 0.01) and phosphocreatine (PCr) content (41.5 +/- 7.3 vs. 18.0 +/- 5.6 micromol/g protein; P < 0.01) at 150 min of reperfusion. CONCLUSION: Long-lasting release of NO by S-NO-HSA prevented uncoupling of eNOS and thereby improved systolic and diastolic function, myocardial perfusion, and the energetic reserve of the heart after I/R injury.

Rapid non-invasive external cooling to induce mild therapeutic hypothermia in adult human-sized swine.

AIM OF THE STUDY: Mild therapeutic hypothermia is a promising new therapy for patients resuscitated from cardiac arrest. Early and fast induction of hypothermia seems to be crucial for best results. The aim of the study was to investigate the feasibility and safety of a new surface cooling method using cold metal plates. SUBJECTS AND METHODS: Twelve adult human-sized swine (79+/-9 kg) were cooled from 38 to 33 degrees C brain temperature. The skin surface was covered with -20 degrees C metal plates (M), as compared to ice packs, alcohol rubs, and fans used in a control group (C). Each method was tested during spontaneous circulation and, after re-warming, during cardiac arrest. Temperatures were recorded continuously. Data are given as mean+/-standard deviation or as median (interquartile range), if not normally distributed. Comparisons between the treatment groups were performed with the independent samples t-test, or the Mann-Whitney rank-sum test. RESULTS: During spontaneous circulation, cooling rates were 9.3+/-1.4 degrees C/h (M), and 6.1+/-1.4 degrees C/h (C) (p=0.003); no skin lesions were observed. During cardiac arrest, cooling rates were 4.1 degrees C/h (1.8-4.8) (M), and 3.7 degrees C/h (3.1-5.3) (C) (p=0.9); no skin lesions were observed. CONCLUSION: Cooling with cold metal plates was an effective method for rapid induction of mild therapeutic hypothermia in adult human-sized swine during spontaneous circulation, without any signs of skin damage. This new surface-cooling device, independent of energy supply during use, should be further investigated.

The presence of MOMA-2+ macrophages in the outer B cell zone and protection of the splenic micro-architecture from LPS-induced destruction depend on secreted IgM.

The role secretory IgM has in protecting splenic tissue from LPS-induced damage was assessed in mice incapable of secreting IgM but able to express surface IgM and IgD. Within seconds after LPS challenge, 99% of the (131)I-labeled LPS was found in the liver and the spleen of both sIgM-deficient and wild-type mice. In the spleen FITC-labeled LPS was found on the surface of 2F8(+) scavenger receptor macrophages localized in the outer marginal zone, while none of the labeled LPS could be detected on marginal zone ER-TR9(+) and MOMA-1(+) macrophages. An additional population of macrophages, MOMA-2(+), were capable of producing C3 locally in the T and B cell zone after LPS challenge. Local C3 production was regulated, as no C3 was found in splenic tissue of unchallenged mice. Interestingly, in the absence of circulating and locally produced secretory IgM, MOMA-2(+) macrophages of the T and B cell zone failed to establish an additional ring of C3-producing macrophages in the outer B cell zone close to the marginal zone upon LPS challenge. The consequence was a massive destruction of the microarchitecture of the spleen where marginal zones disorganized, lymphoid follicles and T cell zones disrupted and follicular DC (FDC) networks disappeared.

Emergency preservation and resuscitation improve survival after 15 minutes of normovolemic cardiac arrest in pigs.

OBJECTIVE: Outcome after prolonged normovolemic cardiac arrest is poor, and new resuscitation strategies have to be found. We hypothesized that the induction of deep hypothermia for emergency preservation and resuscitation (EPR) during prolonged cardiac arrest, before the start of reperfusion, will mitigate the deleterious cascades leading to neuronal death and will thus improve outcome. DESIGN: Prospective experimental study. SETTING: University research laboratory. SUBJECTS: Thirteen pigs, Large White breed (27-37 kg). INTERVENTIONS: After 15 mins of ventricular fibrillation, pigs were subjected to 1) EPR (n = 6), 20 mins of hypothermic stasis induced with a cold saline aortic flush; or 2) 20 mins of conventional resuscitation (n = 7). Then cardiopulmonary bypass was initiated in both groups, followed by defibrillation. Controlled ventilation and mild hypothermia were continued for 20 hrs; survival was for 9 days. For neurologic evaluation, neurologic deficit score (100% = brain dead, 0-10% = normal), overall performance category (1 = normal, 5 = dead or brain dead), and brain histologic damage score were used. MEASUREMENTS AND MAIN RESULTS: In the EPR group, brain temperature decreased from 38.5 degrees C +/- 0.2 degrees C to 16.7 degrees C +/- 2.5 degrees C within 235 +/- 27 secs. Five animals achieved restoration of spontaneous circulation and survived to 9 days: two pigs with overall performance category 2 and three pigs with overall performance category 3. Their neurologic deficit score was 45% (interquartile range 35, 50) and histologic damage score was 142 (interquartile range 109, 159). In the control group, four pigs achieved restoration of spontaneous circulation: one survived to 9 days with overall performance category 3, neurologic deficit score 45%, and histologic damage score 226 (restoration of spontaneous circulation, p = .6; survival, p = .03; overall performance category, p = .02). CONCLUSIONS: EPR is feasible in an experimental pig model and improves survival after prolonged cardiac arrest in pigs. Further experimental studies are needed before this concept can be brought into clinical practice.