摘要:

ObjectiveTo evaluate the blood flow and perfusion pressure differences observed during open- vs. closed-chest cardiopulmonary resuscitation (CPR), including the effects of epinephrine and sodium bicarbonate administration.DesignProspective, randomized, controlled trial.SettingExperimental animal laboratory in a university hospital.SubjectsA total of 35 anesthetized piglets.InterventionsAfter tracheostomy and insertion of arterial, right atrial, and pulmonary arterial catheters, thoracotomy was performed with placement of a pulmonary arterial flow probe and left atrial catheter. Ventricular fibrillation was induced and followed by 15 mins of either open-chest (n = 14) or closed-chest (n = 21) CPR. A 4-min infusion of 50 mmol of sodium bicarbonate or saline was added at the start of CPR. After 8 mins of CPR, 0.5 mg of epinephrine was given intravenously, and after 15 mins, direct current (DC) shocks were used to revert the heart to sinus rhythm.Measurements and Main ResultsBlood flow was studied using transit-time ultrasound flowmetry. In an extended group, intrathoracic pressure was measured for calculation of transmural pressure. Before epinephrine administration, mean pulmonary arterial flow (cardiac output) was reduced: a) during closed-chest CPR relatively more than pulmonary perfusion pressure but in proportion to systemic perfusion pressure; b) during open-chest CPR relatively less than pulmonary perfusion pressure but still in proportion to systemic perfusion pressure. Epinephrine administration temporarily increased systemic perfusion pressure during both closed- and open-chest CPR but temporarily decreased pulmonary perfusion pressure only during closed-chest CPR. After epinephrine administration, cardiac output temporarily decreased during both closed- and open-chest CPR.ConclusionsOpen-chest CPR resulted in better cardiac output and systemic perfusion pressure than closed-chest CPR. However, cardiac output values obtained with both methods were much lower than previously reported. After epinephrine administration, cardiac output became extremely low with both methods.(Crit Care Med 1995; 23:715-725)

ISSN:0090-3493    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

ObjectiveTo validate a new application of the modified acetylene rebreathing method for pulmonary capillary blood flow in a swine extracorporeal membrane oxygenation (ECMO) model.DesignProspective, sequential measurements of pulmonary capillary blood flow, using a rebreathing technique, as affected by different flows through the ECMO circuit.SettingA cardiovascular hemodynamic research laboratory at a university medical center.SubjectsFifteen young mature farm swine (48 to 52 kg).InterventionsPulmonary capillary blood flow was measured using a modified rebreathing technique, and this measurement repeated at different flow rates through the extracorporeal membrane oxygenation circuit. Pulmonary artery flow rates were measured using both thermodilution and echo-Doppler techniques for comparison purposes.Measurements and Main ResultsPulmonary capillary blood flow measurements, as assessed by modified acetylene rebreathing, compared well with both the thermodilution cardiac output measurement during normal circulation and the pulmonary artery flow probe measurement while the subjects received ECMO. Mean pulmonary capillary blood flow measured by acetylene rebreathing decreased from 89.72 +/- 6.97 (baseline) to 43.59 +/- 5.66 mL/kg/min as ECMO flow was maximized to 56.22 +/- 3.62 mL/kg/min. Decreasing the ECMO flow rate by half (to 28.23 +/- 3.45 mL/kg/min) caused an increase in mean pulmonary capillary blood flow to 53.79 +/- 6.16 mL/kg/min. When ECMO flow was discontinued, pulmonary capillary blood flow returned to a near baseline value of 71.68 +/- 7.05 mL/kg/min (mean values of pooled data for both closed-and open-chest animals [n = 15]). These measurements correlated well with both thermodilution cardiac output and pulmonary artery ultrasonic flow probe measurements.ConclusionsThe modified acetylene rebreathing method is a valid and accurate method for the measurement of pulmonary capillary blood flow in the presence of ECMO flows. Pulmonary blood flow decreases as ECMO flow is increased, and the extent of decrease is directly proportional to the amount of flow through the extracorporeal circulation.(Crit Care Med 1995; 23:726-732)

ISSN:0090-3493    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

ObjectiveMyocardial metabolic requirements during reperfusion of ventricular fibrillation are poorly understood. The objective of this study was to determine if controlled reperfusion after a clinically relevant global ischemia period of 10 mins was sufficient to prevent or reverse myocardial ischemia as indicated by changes in myocardial high energy phosphates, myocardial intracellular pH, and great cardiac vein lactate.DesignProspective laboratory study with controlled reperfusion.SettingResearch laboratory at a university medical center.SubjectsFive swine weighing 19 +/- 3 kg.InterventionsTen minutes of nonperfused ventricular fibrillation followed by reperfusion with cardiopulmonary bypass (flow 30 mL/kg/min) for 50 mins.Measurements and Main ResultsMyocardial adenosine triphosphate (ATP), phosphocreatine, and intracellular pH were determined using in vivo31P nuclear magnetic resonance. Myocardial blood flow, measured by 15-mu radiolabeled microspheres, was significantly increased above baseline during reperfusion. Phosphocreatine was depleted during the 10 mins of nonperfused ventricular fibrillation, but recovered to 122 +/- 18% of baseline with reperfusion and was 112 +/- 18% at 60 mins (p < .005). ATP concentrations decreased to 51 +/- 16% of baseline after 10 mins of nonperfused ventricular fibrillation, improved to 67 +/- 9% of baseline with early reperfusion, and were 65 +/- 9% of baseline at 60 mins (p < .02). Myocardial intracellular pH improved from 6.11 +/- 0.18 after 10 mins of nonperfused ventricular fibrillation, to 6.89 +/- 0.20 with early reperfusion, and then decreased to 6.85 +/- 0.35 at 60 mins ventricular fibrillation (p < .001). Despite myocardial blood flows higher than baseline during the reperfusion period, great cardiac vein/aortic lactate gradient increased over the reperfusion period.ConclusionProlonged reperfusion with supranormal myocardial blood flow does not restore normal myocardial aerobic metabolism in the fibrillating myocardium after a 10-min nonperfused ventricular fibrillation period.(Crit Care Med 1995; 23:733-739)

ISSN:0090-3493    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

ObjectiveTo determine the hemodynamic responses to dopamine and epinephrine infusions in newborn piglets during normoxia and hypoxia.DesignProspective, randomized, blind cross-over study.SubjectsNewborn piglets (n = 7).InterventionsAnimals were acutely instrumented for measurements of cardiac output, pulmonary and systemic pressures, carotid and coronary artery blood flow, and coronary artery oxygen consumption. Dopamine at infusion rates of 2 to 16 micro gram/kg/min and epinephrine 0.2 to 1.6 micro gram/kg/min were administered during normoxia. Six piglets were similarly prepared and were then made hypoxic to an arterial O2saturation of 45% to 50%. Epinephrine at infusion rates of 0.2 to 3.2 micro gram/kg/min and dopamine at rates of 2 to 32 micro gram/kg/min were administered in random order during hypoxia.Measurements and Main Results0.4 and 4 micro gram/kg/min, respectively. Increases of both variables were greater with epinephrine than with dopamine. Myocardial extraction ratio was unaffected by dopamine and reduced at 0.2 and 1.6 micro gram/kg/min of epinephrine.Hypoxia caused significant increases in cardiac index, systemic blood pressure, pulmonary arterial pressure, carotid artery blood flow, coronary artery blood flow, coronary oxygen consumption, coronary oxygen extraction ratio, and the pulmonary/systemic vascular resistance ratio.Mean systemic arterial blood pressure increased significantly with 1.6 and 3.2 micro gram/kg/min of epinephrine, but was not significantly affected by dopamine at any infusion rate. Cardiac index was not affected significantly by either of the medications. Thus, there was a significant increase in the calculated systemic vascular resistance index with the highest dose of epinephrine, in contrast to the slight, statistically significant, decrease in calculated systemic vascular resistance index with the highest dose of dopamine. Epinephrine significantly reduced pulmonary arterial pressures at 0.2, 0.4, and 0.8 micro gram/kg/min. Dopamine had no effect on this variable. The pulmonary/systemic vascular resistance ratio was significantly reduced by epinephrine at doses of 0.2 and 3.2 micro gram/kg/min, whereas the highest dose of dopamine caused a significant increase in the pulmonary/systemic vascular resistance ratio.Conclusionsor=to8 micro gram/kg/min, and furthermore, produces a more appropriate hemodynamic profile in the presence of hypoxic pulmonary hypertension than dopamine infusion, in the acutely operated anesthetized piglet.(Crit Care Med 1995; 23:740-748)

ISSN:0090-3493    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

ObjectiveTo determine whether airway hyperresponsiveness contributes to the development of lower airway obstruction in infants recovering from severe meconium aspiration syndrome treated with extracorporeal membrane oxygenation (ECMO).DesignProspective comparison study of the response to bronchodilator during the acute and convalescent phase of severe meconium aspiration.SettingPediatric/neonatal intensive care unit in a tertiary care hospital.PatientsSeven neonates with severe meconium aspiration syndrome that was refractory to conventional mechanical ventilation, requiring ECMO treatment.InterventionsEvaluation of the effect of bronchodilator treatment on the airway function at a postnatal age of 14 +/- 2.7 (SEM) days, after the patients had been off ECMO for 4.6 +/- 1.4 days, and comparison with the response the same patients had shown at a postnatal age of 2.7 +/- 0.6 days, when they had been on ECMO for 1.3 +/- 0.6 days. Lung mechanics and lower airway function were measured and compared before and after administration of aerosolized isoetharine early in the course of ECMO and again several days after ECMO. Maximum expiratory flow-volume curves produced by the deflation flow-volume curve technique were used for evaluating the lower airway function, and partial passive flow-volume curves were used for measuring respiratory system compliance and resistance.Measurements and Main ResultsDuring the first test, isoetharine produced a mild increase in maximum expiratory flows at 25% (MEF25) of forced vital capacity (FVC) (48 +/- 27% compared with baseline values), without significant change in the MEF25to FVC ratio. During the second test approximate 2 wks later (post-ECMO), isoetharine increased MEF25by 123 +/- 29% and increased the MEF25/FVC by 40 +/- 13% compared with baseline values. The percent change in both indices was significantly higher during the second test (p < .05) than in the first test.ConclusionsAirway obstruction in infants recovering from severe meconium aspiration syndrome is partially reversible with aerosolized isoetharine, indicating that airway hyperresponsiveness contributes to the pathogenesis of airway obstruction.(Crit Care Med 1995; 23:749-754)

ISSN:0090-3493    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

ObjectivesTo describe the pulmonary pathology and clinical outcome in children with acute hypoxemic respiratory failure after bone marrow transplantation.DesignReview of medical records and pathologic material of patients diagnosed with acute hypoxemic respiratory failure after bone marrow transplantation.SettingPediatric intensive care unit (ICU) of a teaching hospital.Patients and MethodsRetrospective review of a consecutive cohort of children, with a history of bone marrow transplantation admitted to the pediatric ICU during a 7-yr study period, and who met a published definition of acute hypoxemic respiratory failure. For each admission, the pediatric ICU course and outcome were reviewed. Pathologic material that was obtained from the patients was reexamined and assigned to one of the following categories: acute or organizing diffuse alveolar damage, pulmonary hemorrhage, nonspecific interstitial pneumonitis, or infectious pneumonia.InverventionsNone.Measurements and Main ResultsForty-three patients satisfied criteria for inclusion in the study group. Indications for bone marrow transplantation were: solid tumor (30%), leukemia (44%), congenital immunodeficiency (19%), and aplastic anemia (7%). Patients were admitted to the pediatric ICU a median of 1 month (range 0 to 126) after bone marrow transplantation. Thirty-eight (88%) patients died in the pediatric ICU. Tissue histologic material was available from 21 (49%) patients. Six (29%) of 21 patients had acute diffuse alveolar damage; one (5%) had organizing diffuse alveolar damage; three (14%) had nonspecific interstitial pneumonitis; and two (10%) had pulmonary hemorrhage. Infectious pneumonia occurred in nine (43%) cases (five fungal; four viral).ConclusionsThe acute mortality rate (88%) for children with acute hypoxemic respiratory failure after bone marrow transplantation is similar to that reported for adults with this combination of conditions. Diffuse alveolar damage, the histologic hallmark of adult respiratory distress syndrome, was present in a minority (33%) of patients. Infectious pneumonia was the most frequent cause of acute hypoxemic respiratory failure in patients who had pathologic tissue available, emphasizing the need for aggressive diagnostic studies and early institution of antifungal and antiviral therapy.(Crit Care Med 1995; 23:755-759)

ISSN:0090-3493    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

ObjectiveThis article was written to argue that physicians are not ethically obligated to provide care which they consider futile, unreasonable, or both, either voluntarily or in response to patient or surrogate demands.Data SourcesData used to prepare this article were drawn from published articles, including original investigations, position papers, and editorials in the author's personal files.Study SelectionArticles were selected for their relevance to the subjects of medical ethics, the concepts of futility and medical reasonableness, case law, and healthcare reform.Data ExtractionThe author extracted all applicable data.Data SynthesisPhysicians may feel obligated to provide care in all clinical circumstances due to the single master view of medicine and the ethical principle of autonomy. However, care may be considered futile according to several definitions of that word, including that which describes futile treatment as something that does not benefit the patient as a whole. Furthermore, care may be considered unreasonable if it is excessive and not generally agreed upon. Physician refusal to provide futile or unreasonable care is supported by the ethical principles of nonmaleficence, beneficence, and distributive justice. The last principle is particularly relevant in the current climate of healthcare reform.ConclusionsAlthough the issue of physician refusal of requested care has not been resolved by case law or legal statute, it is supported by compelling ethical principles. Physicians are not ethically required to provide futile or unreasonable care, especially to patients who are brain dead, vegetative, critically or terminally ill with little chance of recovery, and unlikely to benefit from cardiopulmonary resuscitation.(Crit Care Med 1995; 23:760-766)

ISSN:0090-3493    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

ObjectiveTo determine the attitude of pediatric critical care physicians concerning the use of ribavirin in children with respiratory syncytial virus lung disease in light of the revised American Academy of Pediatrics practice guidelines.DesignA questionnaire was sent to 145 pediatric critical care doctors in the United States.Measurements and Main ResultsSeventy-seven percent of questionnaires were returned. The vast majority (91%) of the respondents think that the available literature does not support the Academy's recommendations for the administration of ribavirin to critically ill children with respiratory syncytial virus pneumonia. The largest single group of respondents (42%) does not usually prescribe ribavirin for these patients, but may be persuaded to use it by colleagues or consultants in individual cases. Twenty-six percent of all respondents stated that they do not use ribavirin at any time, even in severely ill patients with documented infection. Twenty-two percent of the respondents say that they will prescribe ribavirin, not because they believe it is efficacious, but because they believe the Academy guidelines compel them to do so as a standard of care. The respondents reported adverse effects of the drug, most notably exacerbations of bronchospasm (92%), far more often than the Academy document asserts. When solicited for general comments, the respondents were frequently concerned that critical care physicians were not involved in the development of the guidelines, the guidelines were based on a paucity of reliable data, and that the guidelines could put them at risk of malpractice litigation should they choose to not use ribavirin.ConclusionsPractice guidelines are increasingly being incorporated into patient care and quality improvement regimens, and it is imperative both that appropriate experts be included in their development, and that they be based on valid scientific data. The pediatric critical care community currently treats most of the severely ill patients with respiratory syncytial virus pneumonia. As a group, they remain unconvinced about the efficacy and safety of this drug, and many pediatricians are concerned about the ramifications of individualizing ribavirin therapy in their patients in light of the revised Academy recommendations.(Crit Care Med 1995; 23:767-772)

ISSN:0090-3493    

出版商:OVID    

年代:1995

数据来源: OVID

ISSN:0090-3493    

出版商:OVID    

年代:1995

数据来源: OVID

ISSN:0090-3493    

出版商:OVID    

年代:1995

数据来源: OVID