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排序方式: 共有190条查询结果,搜索用时 28 毫秒
21.
HY Chan XQ Yao SY Tsang BP Bourreau FL Chan Y Huang . 《Journal of cardiac surgery》2002,17(6):562-562
Background: Calcitonin gene-related peptide (CGRP) is known to have an extremely potent and prolonged vasodilator effect on the coronary arteries. Studies have shown that CGRP increased coronary blood flow and alleviated reperfusion injury in vitro. It is still unknown, however, whether exogenous CGRP has a protective effect on the reperfusion heart associated with cardiopulmonary bypass (CPB). Methods: An in vivo porcine model of CPB was established. Twenty pigs, 10 controls and 10 CGRP used animals (CGRP group), were performed a median sternotomy followed by a standard CPB. All the hearts were arrested for 45 minutes. In the CGRP group, 1mg/kg CGRP was added into the cardioplegia, and another 1mg/kg was reperfused just before the aortic cross-clamp was removed. In both groups, myocardial microvascular perfusion, coronary arterial microvessel diameter and microvessel blood flow were detected by a laser doppler flowmeter and a contact microscope with TV monitor on five consecutive time perioperatively. Result: Myocardial microvascular perfusion was significantly higher and coronary arterial microvessel diameter was larger in the CGRP group on every point of time of reperfusion compared to those in the control group. In the CGRP group, microvessel blood flow also improved significantly than that in the control group during reperfusion. Conclusion: CGRP improves myocardial microcirculation during cardiac ischemia-reperfusion associated with CPB and could become a new, potent myocardial protector. 相似文献
22.
Applying tidal volumes of less than 6 mL/kg might improve lung protection in patients with acute respiratory distress syndrome. In a recent article, Retamal and colleagues showed that such a reduction is feasible with conventional mechanical ventilation and leads to less tidal recruitment and overdistension without causing carbon dioxide retention or auto-positive end-expiratory pressure. However, whether the compensatory increase in the respiratory rate blunts the lung protection remains unestablished.Further reducing tidal volumes beyond the standard 6 mL/kg is an appealing goal in patients with acute respiratory distress syndrome (ARDS) [1]. Such reduction could decrease the tidal stretch imposed on the lung, potentially attenuating further the ventilator-induced lung injury [2]. In fact, tidal volumes of less than 6.5 mL/kg and as low as 4 mL/kg were recently associated with increased survival in patients with ARDS [3]. One of the main obstacles to such a strategy is the potential for carbon dioxide (CO2) retention and severe acidosis. To avoid this, specialized techniques, such as high-frequency oscillatory ventilation and extracorporeal CO2 removal, have been previously tested with mixed results [4-6].In the previous issue of Critical Care, Retamal and colleagues proposed that lower tidal volumes could be used with conventional positive-pressure ventilation without leading to CO2 retention [1]. A reduction in tidal volume from 6 to 4 mL/kg was feasible with a decrease in the instrumental dead space and an increase in the respiratory rate. In patients with ARDS, the dead space is a marker of disease severity [7]. Consequently, very low tidal volumes can be difficult to use in practice, especially in very sick patients, because the necessary increase in respiratory rate might cause significant auto-positive end-expiratory pressure (auto-PEEP). Luckily, patients with severe ARDS also tend to have low lung compliance [8], making their lungs inflate and deflate fast. Therefore, this restrictive ventilatory pattern allows the safe use of high respiratory rates without leading to significant auto-PEEP.Retamal and colleagues [1] should be congratulated for their careful design of the ventilator protocol in the 4 mL/kg phase, which allowed an effective CO2 elimination. The bottom line is that if one decides to use very low tidal volumes with high respiratory rates, attention to the details is invaluable. First, the removal of any dispensable dead space, including substituting an external heated humidifier by the heat-moisture exchanger, is imperative. Second, the use of volume-controlled ventilation helps to keep short inspiratory times. Peak airway pressures may increase, but the preserved expiratory time guarantees low auto-PEEP and, consequently, low plateau pressures. For safety, plateau pressures and auto-PEEP should be measured periodically. Third, in selected cases with high recruitability, the alveolar dead space can be minimized through recruitment maneuvers and higher PEEP values. Finally, the use of a short end-inspiratory pause is encouraged to improve the CO2 elimination [9]. These measures will improve the safety and optimize the CO2 elimination of a strategy with very low tidal volumes, even with higher-than-normal respiratory rates.However, even successfully avoiding CO2 retention, this strategy has yet to be proven effective in terms of further lung protection. We believe that two aspects should be taken into consideration. The first is whether the strategy attenuated the mechanisms of lung injury. The authors performed computed tomography scans in all patients at tidal volumes of both 4 and 6 mL/kg and showed that the amount of cyclic recruitment-derecruitment and hyperinflation decreased after reducing the tidal volume. Although the absolute reduction was small (less than 1% of the lung weight), this finding is suggestive of decreased injury per breath. The second aspect is that an increased respiratory rate can be injurious per se [10]. It would be important to know whether the compensatory increase of the respiratory rate blunted the protective effect per breath of the tidal volume reduction.This tradeoff was emphasized recently in a model of the energy delivered by the ventilator as a surrogate for the potential lung damage [11]. Decreases in tidal volume require disproportionate increases in respiratory rate to maintain alveolar ventilation, and so more energy can be delivered to the lungs even at reduced stress and strain per breath. Though purely theoretical, this hypothesis helps reconcile our expectation of a further protective effect of very low tidal volumes with the recent findings of harmful or null effect of oscillatory high-frequency ventilation [5,6]. In these trials, it is possible that the reduction in lung injury per breath was offset by the very high respiratory rates applied.Finally, Retamal and colleagues [1] followed their patients for 5 to 30 minutes only. Since lower tidal volumes tend to promote atelectasis, especially under insufficient PEEP [12], a longer observation time perhaps would have shown an increase in atelectasis and driving pressures, opposing the benefits initially achieved.In conclusion, we are convinced that a strategy with very low tidal volumes (4 mL/kg) is feasible with conventional positive-pressure ventilation. This strategy could be used in patients with high plateau pressures or high driving pressures with standard 6 mL/kg tidal volumes, but we need more data in terms of lung protection before we can recommend this strategy to every patient with ARDS. 相似文献
23.
24.
Robertson RT; Gallardo KA; Claytor KJ; Ha DH; Ku KH; Yu BP; Lauterborn JC; Wiley RG; Yu J; Gall CM; Leslie FM 《Cerebral cortex (New York, N.Y. : 1991)》1998,8(2):142-155
The role of basal forebrain-derived cholinergic afferents in the
development of neocortex was studied in postnatal rats. Newborn rat pups
received intraventricular injections of 192 IgG-saporin. Following survival
periods ranging from 2 days to 6 months, the brains were processed to
document the cholinergic lesion and to examine morphological consequences.
Immunocytochemistry for choline acetyltransferase (ChAT) and in situ
hybridization for ChAT mRNA demonstrate a loss of approximately 75% of the
cholinergic neurons in the medial septum and nucleus of the diagonal band
of Broca in the basal forebrain. In situ hybridization for glutamic acid
decarboxylase mRNA reveals no loss of basal forebrain GABAergic neurons.
Acetylcholinesterase histochemistry demonstrates a marked reduction of the
cholinergic axons in neocortex. Cholinergic axons are reduced throughout
the cortical layers; this reduction is more marked in medial than in
lateral cortical areas. The thickness of neocortex is reduced by
approximately 10%. Retrograde labeling of layer V cortico-collicular
pyramidal cells reveals a reduction in cell body size and also a reduction
in numbers of branches of apical dendrites. Spine densities on apical
dendrites are reduced by approximately 20-25% in 192 IgG- saporin-treated
cases; no change was detected in number of spines on basal dendrites. These
results indicate a developmental or maintenance role for cholinergic
afferents to cerebral cortical neurons.
相似文献
25.
Trimetrexate (TMTX) is an anticancer drug with potential advantages over the more commonly used antifolate, methotrexate (MTX); however, its use has been limited by severe myelosuppression. Retroviral vectors containing mutant dihydrofolate reductase (DHFR) genes have been used to protect bone marrow cells from MTX, suggesting a similar approach could be used for TMTX. We first screened six variants of human DHFR to determine which allowed maximal TMTX resistance in fibroblasts. A variant enzyme containing a Leu-to-Tyr mutation in the 22nd codon (L22Y) was best, allowing a 100-fold increase in resistance over controls. Murine hematopoietic progenitor cells transduced with an L22Y- containing retroviral vector also showed high-level TMTX resistance in vitro. Mice reconstituted with L22Y-transduced bone marrow cells were challenged with a 5-day course of TMTX to determine whether hematopoiesis could be protected in vivo. Transfer of the L22Y vector resulted in consistent protection from TMTX-induced neutropenia and reticulocytopenia at levels that correlated with the proviral copy number in circulating leukocytes. We conclude that the L22Y vector is highly effective in protecting hematopoiesis from TMTX toxicity and may provide a means for increasing the therapeutic utility of TMTX in certain cancers. 相似文献
26.
27.
AY Neziri M Curatolo A Limacher E Nüesch B Radanov OK Andersen L Arendt-Nielsen P Jüni 《Pain》2012,153(10):2083-2091
Low back pain is associated with plasticity changes and central hypersensitivity in a subset of patients. We performed a case-control study to explore the discriminative ability of different quantitative sensory tests in distinguishing between 40 cases with chronic low back pain and 300 pain-free controls, and to rank these tests according to the extent of their association with chronic pain. Gender, age, height, weight, body mass index, and psychological measures were recorded as potential confounders. We used 26 quantitative sensory tests, including different modalities of pressure, heat, cold, and electrical stimulation. As measures of discrimination, we estimated receiver operating characteristics (ROC) and likelihood ratios. Six tests seemed useful (in order of their discriminative ability): (1) pressure pain detection threshold at the site of most severe pain (fitted area under the ROC, 0.87), (2) single electrical stimulation pain detection threshold (0.87), (3) single electrical stimulation reflex threshold (0.83), (4) pressure pain tolerance threshold at the site of most severe pain (0.81), (5) pressure pain detection threshold at suprascapular region (0.80), and (6) temporal summation pain threshold (0.80). Pressure and electrical pain modalities seemed most promising and may be used for diagnosis of pain hypersensitivity and potentially for identifying individuals at risk of developing chronic low back pain over time. 相似文献
28.
29.
王茹 《岭南心血管病杂志》2005,11(5):320-320
本文总结了用于预防和终止心房颤动的起搏器的类型。窦房结功能异常的病人,心室起搏与较高的心房颤动的发生率相关。有鉴于此,有心房颤动病史、因心动过缓而需要安装起搏器的病人,应该安装双腔或心房起搏生理性起搏器,而不应安装单腔的心室起搏器。 相似文献
30.
Marcelo BP Siqueira Deepak Ramanathan Alison K Klika Carlos A Higuera Wael K Barsoum 《World journal of orthopedics》2016,7(1):30-37
Negative-pressure wound therapy(NPWT) has been a successful modality of wound management which is in widespread use in several surgical fields. The main mechanisms of action thought to play a role in enhancing wound healing and preventing surgical site infection are macrodeformation and microdeformation of the wound bed, fluid removal, and stabilization of the wound environment. Due to the devastating consequences of infection in the setting of joint arthroplasty, there has been some interest in the use of NPWT following total hip arthroplasty and total knee arthroplasty. However, there is still a scarcity of data reporting on the use of NPWT within this field and most studies are limited by small sample sizes, high variability of clinical settings and end-points. There is little evidence to support the use of NPWT as an adjunctive treatment for surgical wound drainage, and for this reason surgical intervention should not be delayed when indicated. The prophylactic use of NPWT after arthroplasty in patients that are at high risk for postoperative wound drainage appears to have the strongest clinical evidence. Several clinical trialsincluding single-use NPWT devices for this purpose are currently in progress and this may soon be incorporated in clinical guidelines as a mean to prevent periprosthetic joint infections. 相似文献