摘要:

ObjectiveIntrathoracic pressure changes are of particular importance under hypovolemic conditions, especially when central venous blood pressure is critically low. Accordingly, the purpose of this study was to assess the feasibility of transcutaneous phrenic nerve stimulation, used in conjunction with an inspiratory impedance threshold, on hemodynamic variables during hemorrhagic shock.DesignProspective, randomized laboratory investigation using a porcine model for measurement of hemodynamic variables, left and right ventricular diameter, and transmitral, transpulmonary, and transaortic blood flow employing transesophageal echo-Doppler technique.SettingUniversity hospital laboratory.SubjectsThirteen female pigs weighing 28–36 kg.InterventionsThe anesthetized pigs were subjected to profound hemorrhagic shock by withdrawal of 55% of estimated blood volume over 20 mins. After a 10-min recovery period, the diaphragm was stimulated with a prototype transcutaneous phrenic nerve stimulator at a rate of ten per minute while the airway was intermittently occluded with an inspiratory threshold valve between positive pressure ventilations. Hemodynamic variables were monitored for 30 mins.Measurements and Main ResultsPhrenic nerve stimulation in combination with the inspiratory threshold valve significantly (p< .001) improved right and left ventricular diameter compared with hypovolemic shock values by 34 ± 2.5% and 20 ± 2.5%, respectively. Moreover, phrenic nerve stimulation together with the inspiratory threshold valve also increased transaortic, transpulmonary, and transmitral valve blood flow by 48 ± 6.6%, 67 ± 13.3, and 43 ± 8.2%, respectively (p< .001 for comparisons within group). Mean ± sem coronary perfusion and systolic aortic blood pressures were also significantly (p< .001) higher compared with values before stimulation (30 ± 2 vs. 20 ± 2 mm Hg, and 37 ± 2 vs. 32 ± 3 mm Hg, respectively).ConclusionsThis feasibility study suggests that phrenic nerve stimulation with the inspiratory threshold valve may improve cardiac preload and, subsequently, key hemodynamic variables in porcine model of severe hemorrhagic shock.

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

ObjectiveMeasurements of steady-state adenosine-5′-triphosphate (ATP) levels in tissue samples from patients or experimental animals with sepsis or endotoxemia provide little information about the rate of ATP production and consumption in these conditions. Accordingly, we sought to use anin vitro“reductionist” model of sepsis to test the hypothesis that proinflammatory cytokines modulate ATP turnover rate.DesignIn vitro“reductionist” model of sepsis.SettingUniversity laboratory.SubjectsCultured rat enterocyte-like cells.InterventionsIEC-6 nontransformed rat enterocytes were studied under control conditions or following incubation for 24 or 48 hrs with cytomix, a mixture of tumor necrosis factor-&agr; (10 ng/mL), interleukin-1&bgr; (1 ng/mL), and interferon-&ggr; (1000 units/mL). To measure ATP turnover rate, ATP synthesis was acutely blocked by adding to the cells a mixture of 2-deoxyglucose (10 mM), potassium cyanide (8 mM), and antimycin A (1 &mgr;M). ATP content was measured at baseline (before metabolic inhibition) and 0.5, 1, 2, 5, and 10 mins later. Log-linear ATP decay curves were generated and the kinetics of ATP utilization thereby calculated.Measurements and Main ResultsATP consumption rate was higher in cytomix-stimulated compared with control cells (3.11 ± 1.39 vs. 1.25 ± 0.66 nmol/min, respectively;p< .01). Similarly, the half-time for ATP disappearance was shorter in cytomix-stimulated compared with control cells (2.63 ± 1.00 vs. 6.21 ± 3.49;p< .05). In contrast to these findings, the rate of ATP disappearance was similar in cytokine-naïve and immunostimulated IEC-6 cells when protein and nucleic acid synthesis were inhibited by adding 50 &mgr;g/mL cycloheximide and 5 &mgr;g/mL actinomycin D to cultures for 4 hrs. The rates of glucose consumption and lactate production were significantly greater in cytomix-stimulated compared with controls cells.ConclusionsIncubation of IEC-6 cells with cytomix significantly increased ATP turnover. Increased ATP turnover rate was supported by increases in the rate of anaerobic glycolysis. These findings support the view that proinflammatory mediators impose a metabolic demand on visceral cells. In sepsis, cells may be more susceptible to dysfunction on the basis of diminished oxygen delivery and/or mitochondrial dysfunction.

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

ObjectiveIncreased pulmonary blood flow is believed to contribute to the development of pulmonary hypertension. We investigated the effect of overcirculation via an aortocaval fistula, on the development of monocrotaline-induced pulmonary hypertension in rats. Monocrotaline was administered 1 wk after the creation of an aortocaval fistula.DesignRandomized, controlled study.SettingResearch laboratory of an academic institution.SubjectsMale Sprague-Dawley rats.InterventionsOvercirculation was induced by pneumonectomy and by surgical creation of aortocaval fistula. Pulmonary artery hypertension was induced by administration of monocrotaline.Measurements and Main ResultsAortic blood flow, Pao2, and pulmonary arterial pressure were measured 4 wks later. A blinded investigator quantified pulmonary arterial neointimal formation in small pulmonary arteries. Compared with animals that received monocrotaline and/or underwent pneumonectomy but did not undergo aortocaval fistula, the presence of a surgical aortocaval fistula was associated with increased aortic blood flow (p< .001), increased Pao2(p< .001), and lower mean pulmonary arterial pressure (p< .001). In addition, rats with aortocaval fistula had less pulmonary arterial neointimal formation than matched animals without an aortocaval fistula (p= .034).ConclusionsThe presence of a surgical aortocaval fistula attenuates, rather than worsens, the development of monocrotaline-induced pulmonary hypertension in rats.

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

ObjectiveThis study was designed to compare the effects of continuous venovenous hemofiltration (CVVH) with two different membranes, polysulphone and polyacrylonitrile (AN69), on global and regional hemodynamics, plasma lactate, tumor necrosis factor-&agr; levels, and plasma nitrite/nitrate during endotoxic shock in dogs.MethodsFifteen pentobarbital anesthetized and mechanically ventilated dogs were randomized into three groups of five dogs each. One group served as an endotoxin alone, time matching group and, 1 hr after endotoxin administration, the two other groups received CVVH at 3 L/hr for 270 mins, with either a polysulphone membrane or an polyacrylonitrile membrane.ResultsAt 90 mins after endotoxin administration, dogs receiving CVVH with polyacrylonitrile membranes had a higher cardiac output, stroke volume, and left-ventricular stroke work index than the endotoxin alone and the polysulphone groups. CVVH with either polyacrylonitrile or polysulphone membranes prevented the rise in pulmonary artery pressure and pulmonary vascular resistance compared with the endotoxin alone group. Plasma lactate levels were not significantly altered, but the fall in bicarbonate seen in the endotoxin alone group did not occur in the two CVVH groups. Tumor necrosis factor levels in the plasma were not significantly altered by CVVH and remained very low (<50 pg/mL) in the ultrafiltrate fluid.ConclusionIn this acute endotoxic shock model, CVVH with the polyacrylonitrile membrane improved cardiac performance when compared with the polysulphone membrane. These effects could be caused by a more effective adsorption of inflammatory mediators other than tumor necrosis factor. Whether the polyacrylonitrile membrane should be preferred over the polysulphone membrane for CVVH in severe sepsis warrants further experimental and clinical study.

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

ObjectiveTo examine neuropsychological function, depression, and quality of life 6 months after discharge in patients who received mechanical ventilation in the intensive care unit.DesignProspective cohort study.SettingTertiary care, medical and coronary intensive care unit of a university-based medical center.Study PopulationA total of 275 consecutive, mechanically ventilated patients from a medical intensive care unit were prospectively followed. At 6 months, 157 were alive, of whom 41 (26%) returned for extensive follow-up testing.Measurement and Main ResultsNeuropsychological testing and assessment of depression and quality of life were performed at 6-month follow-up. Seven of 41 patients were excluded from further analysis due to preexisting cognitive impairment determined via surrogate interviews using the Modified Blessed Dementia Rating Scale and a review of medical records. On the basis of strict criteria derived from normative data, we found that 11 of 34 patients (32%) were neuropsychologically impaired. Impairment was generally diffuse but occurred primarily in areas of psychomotor speed, visual and working memory, verbal fluency, and visuo-construction. The rate of neuropsychological deficits in the study population was markedly higher than population norms for mild dementia. Scores on the Geriatric Depression Scale–Short Form were significantly more abnormal in the neuropsychologically impaired group than in the nonimpaired group at hospital discharge (p= .04) and at 6-month follow-up (p= .02), and clinically significant depression was found in 27% of impaired subjects at hospital discharge and in 36% at 6-month follow-up. No differences were observed between groups in quality of life as measured with the Short Form Health Survey-12 at discharge or 6-month follow-up.ConclusionsProlonged neuropsychological impairment is common among survivors of the medical intensive care unit and occurs with greater than anticipated frequency when compared with relevant normative data. Future investigations are warranted to elucidate the nature of the association between critical illness, neuropsychological impairment, depression, and decreased quality of life.

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

ObjectiveTo determine the validity of predictive equations in calculating oxygen consumption (Vo2) in ventilated patients with congenital heart disease.DesignProspective study.SettingCardiac catheterization laboratories and intensive care units of two university teaching hospitals.PatientsA total of 126 patients with congenital heart disease were studied. Of these, 75 patients received anesthesia in the pediatric cardiac catheterization laboratory, and 51 were deeply sedated in the intensive care unit after open heart surgery.Measurements and Main ResultsVo2was measured directly in all patients using respiratory mass spectrometry. Estimated values for absolute Vo2(mL/min) and indexed Vo2(mL·min−1·m−2) were calculated from the four predictive equations published by LaFarge and Miettinen, Lundell et al., Wessel et al., and Lindahl. The agreement between measured and estimated Vo2was evaluated by calculating their bias and limits of agreement. A failure of agreement between measured and estimated Vo2was noted in both groups of patients, irrespective the equation used, and the agreement was poorer in patients in the intensive care unit. The equation by LaFarge and Miettinen produced the closest estimation in patients at cardiac catheterization with a bias of 4.5 mL/min for absolute Vo2and 6.9 mL·min−1·m−2for indexed Vo2. A systematic error of overestimating lower and underestimating higher indexed Vo2mL·min−1·m−2was introduced in both groupsConclusionPredictive equations do not accurately estimate Vo2in ventilated patients with congenital heart disease.

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

ObjectiveTo review case reports of pregnant women who have been supported after brain death until successful delivery of their infants. From these reports and other literature about brain death, normal physiologic changes of pregnancy, and specific needs for fetal development, recommendations were made to assist in supporting pregnant women after brain death until delivery of a mature fetus who is likely to survive.Data SourcesPersonal files and experiences, MEDLINE review of case reports and publications about physiologic changes present during normal pregnancy and after brain death, and the critical needs for fetal development were included.Data ExtractionEleven reports of ten patients comprise the accumulated clinical experience. Hypotension, requiring fluid administration and inotropic/vasopressor therapy, occurred in all the mothers, and in six cases, was the reason for urgent delivery. The longest period of support was 107 days, from 15 to 32 wks of gestation. Two mothers also became organ donors. Recurrent infections, thermolability, and other complications common to prolonged ICU care were encountered. All infants survived. One had congenital abnormalities caused by phenytoin use by the mother. When followed, all others developed within normal growth and mental variables. These cases plus literature citations noted above were used to develop recommendations for maternal/fetal care.ConclusionPreservation of uterine/placental blood flow is the most important priority during somatic support. Imprecise autoregulation of the uterine vasculature during maternal hypoxemia or hypotension makes this goal a significant challenge. Special considerations for nutrition; medication use; cardiovascular, respiratory, or endocrine therapy; fetal monitoring; hormone replacement; and ethical concerns are discussed.

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

ObjectiveIn 1991, the American College of Chest Physicians (ACCP) and the Society of Critical Care Medicine (SCCM) convened a “Consensus Conference,” the goals of which were “to provide a conceptual and a practical framework to define the systemic inflammatory response to infection, which is a progressive injurious process that falls under the generalized term ‘sepsis’ and includes sepsis-associated organ dysfunction as well.” The general definitions introduced as a result of that conference have been widely used in practice and have served as the foundation for inclusion criteria for numerous clinical trials of therapeutic interventions. Nevertheless, there has been an impetus from experts in the field to modify these definitions to reflect our current understanding of the pathophysiology of these syndromes.DesignSeveral North American and European intensive care societies agreed to revisit the definitions for sepsis and related conditions. This conference was sponsored by the SCCM, The European Society of Intensive Care Medicine (ESICM), The American College of Chest Physicians (ACCP), the American Thoracic Society (ATS), and the Surgical Infection Society (SIS).MethodsThe conference was attended by 29 participants from Europe and North America. In advance of the conference, five subgroups were formed to evaluate the following areas: signs and symptoms of sepsis, cell markers, cytokines, microbiologic data, and coagulation parameters. The subgroups corresponded electronically before the conference and met in person during the conference. A spokesperson for each group presented the deliberation of each group to all conference participants during a plenary session. A writing committee was formed at the conference and developed the current article based on executive summary documents generated by each group and the plenary group presentations. The present article serves as the final report of the 2001 International Sepsis Definitions Conference.ConclusionThis document reflects a process whereby a group of experts and opinion leaders revisited the 1992 sepsis guidelines and found that apart from expanding the list of signs and symptoms of sepsis to reflect clinical bedside experience, no evidence exists to support a change to the definitions. This lack of evidence serves to underscore the challenge still present in diagnosing sepsis in 2003 for clinicians and researchers and also provides the basis for introducing PIRO as a hypothesis-generating model for future research.

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

ObjectivesPalliative care is an important component of critical care medicine. Few fellowship programs have developed a curriculum designed to teach palliative care precepts to trainees. We describe our 2-yr experience in teaching palliative care to multidisciplinary critical care medicine fellows.DesignTwo-consecutive-year palliative care training for unselected critical care medicine fellows at a large, urban, university, tertiary care medical center.InterventionsWe 1) identified palliative care skills and knowledge that first-year critical care fellows should acquire; 2) developed a curriculum to teach those skills and knowledge, including required readings, small group lectures and skills sessions that included role-playing to modify skills and attitudes, and (in year 2) experiential learning on a hospital-based palliative care rotation; and 3) attempted to evaluate the curriculum with attitude and knowledge assessments.ResultsA total of 35 fellows participated in the palliative care training during the 2 yrs reported. Seven fellows participated in a clinical rotation in palliative care. Fellows evaluated usefulness of the small group sessions between 4.4 and 4.9 on a 5-point Likert scale. Four of seven fellows rated the clinical rotation quality at 3/5. Pretest and posttest knowledge mean scores were 58% and 69%, respectively. Problems included providing time for fellows to participate in the clinical rotation and negative attitudes regarding the relevance of palliative care to their future in critical care.ConclusionsPalliative care training for critical care fellows is feasible. Fellows value skills training more than a clinical rotation in palliative care. Baseline knowledge of palliative care is low.

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

ContextEnd-of-life care remains a challenging and complex activity in critical care units. There is little information concerning the influence of administrative models of care delivery on end-of-life care.ObjectiveTo compare and contrast end-of-life care delivery in intensive care units using “semiclosed,” “open,” and “closed” administrative models.DesignEthnographic study of three critical care units.SettingUniversity hospitals in the United States and New Zealand.SubjectsApproximately 600 physicians, nurses, allied health personnel, patients, family members, and friends.Measurements and Main ResultsEthnographic observations were made at three sites for 75, 3, and 10 wks, respectively. Eighty end-of-life care episodes were observed. The interactions among care personnel and families varied according to the administrative model, depending on whether surgeons or intensivists had primary patient responsibility. This led to differential timing on the shift from “cure” to “comfort,” and differential decision-making power for families.ConclusionsEnd-of-life care varies according to the administrative model. When surgeons have primary responsibility for the patient, the most important goal is defeating death. When intensivists have sole patient responsibility, scarce resources are considered and quality of life is a significant variable. Discussions about improving the way end-of-life decisions are carried out in intensive care units rarely consider the administrative models and personal, professional, and national values affecting such decisions. To improve care at the end of life, we must critically examine these features.

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID