[Establishment of an adaptable acute pain model for induction of nociceptive stimuli of defined intensity and duration using thermal stimulation]. / Etablierung eines adaptierbaren Akutschmerzmodells zur Induktion nozizeptiver Stimuli definierter Intensität und Dauer mittels thermischer Reize.

BACKGROUND: In previous years numerous acute pain models to investigate the pathophysiological mechanisms of pain and to validate treatment procedures have been described. Due to the specific questions addressed by different trials standardized protocols are often missing. Therefore, the research results obtained are only comparable or reproducible to a limited extent. The transferability of acquired knowledge to clinical pain is limited by the mostly short test duration of already established models. METHOD: The aim of this study was to establish a standardized protocol for an acute pain model that induces nociceptive thermal stimuli of defined intensity and variable duration using a device for quantitative sensory testing (QST). The greatest possible exclusion of factors influencing pain perception was achieved. In order to reduce the risk of thermal tissue damage a capsaicin cream was applied to the test area, which led to a significant increase in the perceived pain intensity of heat stimuli. RESULTS: From previously performed experiments on thermal pain thresholds and temporal aspects of pain adaptation, the parameters for stimulus lengths and thermode temperatures for a cold and heat pain model could be derived. The acute pain model established here was able to induce significant heat and cold pain stimuli over variable periods of time. An average pain intensity of NRS ≥ 6 was reported by the test participants. Among the 30 subjects no tests were terminated due to intolerance. CONCLUSION: The established acute pain model in this study is characterized by the induction of thermal pain stimuli of defined intensity and variable duration. There is no danger of significant thermal tissue damage and the pain was tolerated by all study participants. The pain model can easily be established using a device for quantitative sensory testing.

Daptomycin for the treatment of major gram-positive infections after cardiac surgery.

BACKGROUND: Infection is a main cause of morbidity and mortality after heart surgery, with multi-resistant pathogens increasingly representing a challenge. Daptomycin provides bactericidal activity against gram-positive organisms that are resistant to standard treatment including vancomycin. METHODS: A cohort of cardiac surgical patients, treated with daptomycin for major infection at two tertiary care centers, were retrospectively studied with a particular focus on the type of infection, causative pathogens and co-infections, daptomycin dosage, adverse events and outcome in order to provide evidence for the efficiency and safety of daptomycin in a distinct high-risk patient population. RESULTS: Sixty-five patients (87.7 % males, 60.4 ± 13.5 years) who had undergone aortic surgery (20.0 %), ventricular assist device (VAD) implantation (21.5 %), combined procedures (21.5 %), coronary artery bypass grafting (12.3 %), isolated valve surgery (15.4 %) and heart transplantation (7.7 %) were diagnosed with catheter-related infection (26.1 %), valve endocarditis (18.8 %), sternal wound (13.0 %), VAD-associated (11.6 %), cardiac implantable electrophysiological device (CIED)-associated (4.1 %), respiratory tract (4.3 %), bloodstream (4.3 %) and other infection (4.3 %). In 13.0 %, no focus of infection was identified though symptoms of severe infection were present. The most frequent pathogens were Staphylococcus epidermidis (30.4 %), Staphylococcus aureus (23.1 %) and Enterococcus species (10.1 %). Daptomycin doses ranging from 3 mg/kg every 48 h to 10 mg/kg every 24 h were administered for 15.4 ± 11.8 days. 87.0 % of the cases were classified as success, 7.2 % as treatment failure and 5.8 as non-evaluable. Adverse events were limited to one case of mild and one case of moderate neutropenia with recovery upon termination of treatment. CONCLUSION: Daptomycin proved safe and effective in major infection in high-risk cardiac surgical patients.

[Quality of postoperative pain therapy: evaluation of an established anesthesiology acute pain service]. / Qualität der postoperativen Schmerztherapie : Evaluation eines etablierten anästhesiologischen Akutschmerzdiensts.

BACKGROUND: Despite well-designed concepts of perioperative pain management, recent studies have revealed that a large number of patients still suffer from unacceptable pain after surgery. The purpose of this prospective evaluation was to critically analyze postoperative pain treatment provided by a routinely established, DIN certified acute pain service (APS) at the University Hospital Großhadern in Munich. MATERIALS AND METHODS: A total of 1,000 consecutive patients received one of the following analgesic procedures: continuous epidural analgesia (EA, n = 401), continuous and patient-controlled epidural analgesia (PCEA, n = 305), intravenous patient-controlled analgesia with opioids (PCA, n = 169) or continuous peripheral nerve block (CPNB, n = 125). For EA and PCEA, ropivacaine 0.2 % and sufentanil 0.24 µg/ml were administered while peripheral regional analgesia was performed with infusion of ropivacaine 0.2 % only. Patients with PCEA were allowed a 3 mg bolus once per hour on demand. Standardized intravenous PCA was performed with piritramide 2.5 mg/ml, a bolus of 2.5 mg, a lock-out time of 15 min, a maximum of 25 mg/4 h and no background infusion. During the daily visits the APS assessed pain intensity at rest and during movement on a numerical rating scale from 0 (no pain) to 10 (maximum pain), acceptance of pain, satisfaction with the analgesic procedure, demand of additional non-opioid analgesics, the need for optimization including bolus applications and changes of the infusion rate or retraction of the epidural catheter. The duration of the procedures, side effects and complications were documented. The catheter insertion sites were inspected daily for redness and tenderness on palpation. RESULTS: In general, epidural and peripheral regional analgesic techniques were superior in terms of postoperative analgesia to intravenous opioid PCA and were associated with fewer side effects, such as sedation, nausea, vomiting, obstipation and sensorimotor deficits. A subgroup analysis revealed that in major upper abdominal surgery, EA provided significantly better analgesia at rest and during movement than PCA. In lower abdominal surgery PCEA induced significantly better analgesia than both PCA and EA, especially during movement. Patient satisfaction was generally high and was best with PCEA (95 %) followed by CPNB (94 %), EA (91 %) and PCA (88 %). On the first postoperative day analgesic procedures had to be optimized (e.g. by bolus administration, retraction of catheters or changes to standardized PCA) in 23 % of EA patients, 10 % of PCEA patients, 6 % of PCA patients and 12 % of CPNB patients. Major complications, such as neuraxial hematoma, infections or respiratory depression were not observed. CONCLUSIONS: As described in many prospective studies, this evaluation revealed that for postoperative pain control, regional anesthesia is superior to intravenous patient-controlled analgesia with strong opioids in terms of analgesia and side effects. In the setting of a well-organized acute pain service with frequent education and training of all members involved, postoperative pain management is safe and effective. However, regular re-evaluation of the defined and certified procedures is necessary.

[Daptomycin for the treatment of gram-positive infections after cardiac surgery]. / Daptomycin zur Behandlung grampositiver Infektionen nach herzchirurgischen Eingriffen.

BACKGROUND AND METHOD: Surgical infection remains a main cause of death after heart surgery, despite advances in pharmacological therapy. Daptomycin is a cyclic lipopeptide antibiotic, useful in gram-positive organisms resistant to standard treatment, including vancomycin. The aim of this study was to describe the use of daptomycin regarding efficacy, efficiency and safety in patients with gram-positive infections after heart surgery using a retrospective analysis on 49 adult patients. CONCLUSION: Daptomycin shows excellent in vitro and in vivo activity against gram-positive organisms, such as Enterococcus faecalis, Enterococcus faecium, Staphylococcus aureus, especially MRSA. Daptomycin is also effective against increasing vancomycin-resistant or vancomycin-intermediate S. aureus.

Stress doses of hydrocortisone reduce systemic inflammatory response in patients undergoing cardiac surgery without cardiopulmonary bypass.

BACKGROUND: Systemic inflammatory response occurs after cardiac surgery (CS) and leads to a worse outcome in many cases. Stress doses of hydrocortisone have been successfully used to reduce SIRS and to improve outcome of patients after CS with cardiopulmonary bypass grafting (on-pump CABG), but the effect of hydrocortisone on patients undergoing CS without cardiopulmonary bypass grafting (off-pump CABG) is unclear. Therefore, we evaluated the effect of stress doses of hydrocortisone in this group of patients. METHODS: A total of 305 patients undergoing off-pump CABG were enrolled in a prospective randomized trial according to the study protocol. The patients either received stress doses of hydrocortisone or placebo. We measured various laboratory and clinical variables characterizing the patients' outcomes. RESULTS: The two study groups did not differ with regard to demographic data. Patients receiving hydrocortisone had an increased Higgins score and a decreased ejection fraction. Furthermore, patients from the hydrocortisone group had significantly lower levels of IL-6 (275 [162/677] pg/mL vs. 450 [320/660] pg/mL, P=0.001) and a shorter stay in the ICU (1 [1/3] day vs. 2 [2/3] days, P=0.04). Both groups did not differ in regard to catecholamine support, duration of mechanical ventilation, incidence of postoperative atrial fibrillation, blood loss, and mortality rate. CONCLUSION: We conclude that intravenous stress doses of hydrocortisone lead to a reduction of systemic inflammation and to a potential improvement in the early outcome of patients undergoing off-pump CABG.

Evaluation of murine liver transmission electron micrographs by an innovative object-based quantitative image analysis system (Cellenger).

BACKGROUND: Transmission electron micrographs are widely used to demonstrate tissue damage. However, the results are qualitative and dependent on the experience of the investigator. Recently, a new multiscale object-based quantitative image analyzing systems (Cellenger) has been introduced to study highly textured black-and-white images. It is unknown, whether this system permits the quantitative image analysis of electron micrographs of parenchymal tissue. Therefore, we analyzed whether the Cellenge system permits the quantitative evaluation of electron micrographs of murine liver under normal conditions and after ischemia-reperfusion injury. The results were compared with those obtained by conventional qualitative classification. - METHOD: Transmission electron micrographs from murine liver that had been exposed to isolated reversible ischemia at hypothermic conditions of 4 degrees C, 15 degrees C, 26 degrees C and 37 degrees C, and of sham-operated animals, which served as controls (2 images per animal, n = 3 in each group), were analyzed qualitatively by an investigator with experience in electron microscopy. For quantitative analysis, the Cellenger was used and the following damage parameters were studied: ratio of area of endothelial cell nucleus to area of endothelial cell (N/C ratio), ratio of area of hepatocellular vacuoles to area of total hepatocyte cytoplasm (V/C ratio) and ratio of area of microvilli in the space of Disse to area of the sinusoids (M/S ratio). All values were sampled within one group (n=6) and the data given in [%] (MW +/- SEM). P-values were accepted as significant below 0.05. RESULTS: After normothermic ischemia, all quantitative damage parameter were significantly altered as compared to sham-operated animals (N/C 15 +/- 9% vs. 37 +/- 7%, V/C 18 +/- 4% vs. 0, and M/S 0 vs. 10 +/- 1%) and all hypothermia groups. The qualitative electron micrograph section analysis corresponded very well with these results. CONCLUSION: We demonstrate that an multiscale object-based quantitative analysis of transmission electron micrographs from mouse liver under control conditions and after I/R provide accurate classification of relevant tissue damage parameter. The system is now ready to use for further applications within the field of highly textured electron micrographs.

The influence of organ temperature on hepatic ischemia-reperfusion injury: a systematic analysis.

BACKGROUND: Although hepatic ischemia-reperfusion (I/R) injury can be reduced by cooling of the ischemic organ, a systematic in vivo analysis of the influence of organ temperature in I/R injury is missing. The aim of this study was to systematically investigate the impact of defined temperatures of the ischemic liver tissue on microvascular I/R injury. METHODS: Ischemia of the left liver lobe was induced in C57BL/6 mice for 90 min. The ischemic lobe was placed in a polyethylene well and the temperature was adjusted to 37 degrees C, 26 degrees C, 15 degrees C, and 4 degrees C by superfusion with cooled/warmed saline solution. The ischemia groups (n=7 each) were compared with a sham-operated group (n=7). The sinusoidal perfusion index and the number of leukocytes firmly adherent to the endothelium of postsinusoidal venules were assessed using intravital fluorescence microscopy at 30 min, 120 min, and 240 min of reperfusion, respectively. At the end of the experiment, serum activities of the liver enzymes aspartate aminotransferase/alanine aminotransferase were determined, and tissue specimens were examined by electron microscopy. RESULTS: Core body temperature did not differ significantly between the groups. In the 37 degrees C group, the sinusoidal perfusion index was significantly reduced and the number of adherent leukocytes was significantly increased compared with the sham group. In all hypothermia groups, however, the microcirculatory parameters did not differ from the sham group. Serum activities of aspartate aminotransferase/alanine aminotransferase were significantly increased and hepatocellular integrity was severely affected in the 37 degrees C group as compared with all other groups. CONCLUSIONS: These findings demonstrate that in the mouse liver the known protective effect of hypothermia is already encountered at 26 degrees C. Further reduction of temperature did not generate additional protection from I/R injury.

Ischemia at 4 degrees C: a novel mouse model to investigate the effect of hypothermia on postischemic hepatic microcirculatory injury.

Hypothermia of the ischemic organ at 4 degrees C protects hepatic microcirculation from ischemia-reperfusion (IR) injury. The effect of hypothermia during ischemia was investigated in animal models using liver transplantation and storage of the harvested organ in cold preservation solutions. No investigation of the isolated influence of hypothermia at 4 degrees C of the ischemic organ on hepatic IR injury exists, due to the lack of an appropriate animal model. Therefore, the aim of our present study was to develop such a model using intravital video fluorescence microscopy (IVM). In C57BL/6 mice, a reversible isolated ischemia of the left liver lobe was induced for 90 min, followed by 240 min of reperfusion. The temperature of the ischemic organ was adjusted to either 4 degrees C or 37 degrees C by superfusion with 0.9% NaCl. Sham-operated animals without IR served as controls. The hepatic microcirculation was analyzed using IVM at 30 min and 240 min after reperfusion by quantifying sinusoidal perfusion and leukocyte-endothelial cell interaction in postsinusoidal venules. At the end of the experiment, blood and tissue samples were taken for measurement of liver enzyme activities and light and electron microscopy. Mean arterial pressure and body temperature were kept constant throughout the experiment, while the temperature of the ischemic liver lobe was adjusted to predefined levels. After normothermic ischemia, hepatic microvascular perfusion was significantly impaired compared with sham-operated animals. Perfusion failure was significantly reduced in hypothermic livers and did not differ from livers of the sham-group. Liver enzyme activities in the normotherimic group were significantly higher than in the sham and hypothermic groups. Light and electron microscopy revealed severe histological alterations at 37 degrees C ischemia, whereas at 4 degrees C ischemia only minimal lesions were encountered. Our novel model allows for isolated adjustment of ischemic liver lobe temperature without changing body temperature and systemic macrohemodynamic parameters. Hypothermia at 4 degrees C largely attenuates postischemic microvascular perfusion injury of the liver.

In vivo assessment of colon microcirculation: comparison of the new OPS imaging technique with intravital microscopy.

BACKGROUND: The Orthogonal Polarization Spectral (OPS) imaging technique has been introduced for in vivo assessment of microcirculation in humans. Unclear remains, whether the new technique would allow for accurate investigations of the colon microcirculation with respect to the unique conditions of the microvasculature in that particular tissue. Therefore, the aim of this study was to validate the new technique against intravital fluorescence microscopy (IFM) for the visualization of colon microcirculation in a murine model of inflammatory bowel disease (IBD). METHOD: IBD was induced in Balb/c mice by dextran sulfate sodium (DSS), controls received normal water. In each animal, both the CYTO-SCAN A/R and IFM were used to image the microcirculation (n = 7 in each group). Postcapillary venular diameter, venular red blood cell velocity (RBC-V) and functional capillary density (FCD) were analyzed on the colon muscularis and mucosa and compared to each other using linear regression analysis and Bland-Altman plots. RESULTS: All parameters correlated significantly between the both methods. The venular diameters and the RBC-V were significantly different between control and colitis group in contrast to FCD; these results were present while using both methods. CONCLUSION: Our study demonstrates that the new technique for visualization of microcirculation without use of fluorescent dyes, the OPS-imaging, allows for quantitative measurement of the key microcirculatory parameters of the mouse colon.