摘要:

ObjectiveTo test the hypothesis that in a swine model of acute respiratory distress syndrome (ARDS) with permissive hypercapnia, inhaled nitric oxide would improve transpulmonary vascular mechanics and right ventricular workload while not changing intrinsic right ventricular contractility.DesignProspective, randomized, controlled laboratory trial.SettingUniversity research laboratory.SubjectsEleven swine (30 to 46 kg).InterventionsThe swine were anesthetized, intubated, and paralyzed. After median sternotomy, pressure transducers were placed in the right ventricle, pulmonary artery, and left atrium. An ultrasonic flow probe was placed around the pulmonary artery. Ultrasonic dimension transducers were sutured onto the heart at the base, apex, left ventricle (anterior, posterior, free wall), and right ventricle (free wall). An additional transducer was placed in the interventricular septum. A surfactant depletion model of ARDS was created by saline lung lavage. Nitric oxide was administered at 2, 4, and 6 parts per million (ppm), in a random order, under the condition of permissive hypercapnia (Paco255 to 75 torr [7.3 to 10.0 kPa]).Measurements and Main ResultsWe evaluated the pulmonary vascular and right ventricular effects of permissive hypercapnia, with and without inhaled nitric oxide, by measuring variables of transpulmonary vascular mechanics and right ventricular function. These variables included mean pulmonary arterial pressure, right ventricular total power, right ventricular stroke work, transpulmonary vascular efficiency, and right ventricular intrinsic contractility. Data were obtained after lung injury under the following conditions: a) normocapnia (Paco235 to 45 torr [4.7 to 6.0 kPa]) and nitric oxide at 0 ppm; b) hypercapnia and nitric oxide at 0 ppm; c) hypercapnia and nitric oxide at 2, 4, and 6 ppm; and d) repeat measurements with hypercapnia and nitric oxide at 0 ppm.In ARDS with permissive hypercapnia, inhaled nitric oxide therapy (2 to 6 ppm) improved transpulmonary vascular mechanics and right ventricular workload by lowering pulmonary arterial pressure (29.6 +/- 1.3 vs. 24.6 +/- 1.0 mm Hg, p = .0001), increasing transpulmonary vascular efficiency (13.9 +/- 0.5 vs. 16.1 +/- 0.7 L/W-min, p = .0001), decreasing right ventricular total power (142 +/- 9 vs. 115 +/- 9 mW, p = .001), and decreasing right ventricular stroke work (653 +/- 37 vs. 525 +/- 32 ergs times 103, p = .001). Inhaled nitric oxide did not change right ventricular contractility, as measured by preload-recruitable stroke work.ConclusionsInhaled nitric oxide ameliorated any negative effects of hypoxic and hypercapnic pulmonary vasoconstriction. The beneficial effects of inhaled nitric oxide are related to alterations in right ventricular afterload and not intrinsic right ventricular contractility. The improved cardiopulmonary effects of inhaled nitric oxide with permissive hypercapnia potentially expand the use of nitric oxide in ARDS and other conditions in which this strategy is employed.(Crit Care Med 1996; 24:1554-1561)

ISSN:0090-3493    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo analyze the effect of different levels of positive end-expiratory pressure (PEEP) on extravascular lung water and on lymphatic drainage through the thoracic duct during hydrostatic pulmonary edema.DesignRandomized, controlled, experimental study.SettingResearch laboratory of a tertiary care hospital.SubjectsEighteen beagle dogs weighing between 10 and 19 kg.InterventionsDogs were anesthetized and cannulated via a thoracic duct. Hydrostatic pulmonary edema was provoked by inflating the balloon of a Foley catheter in the left atrium. Different amounts of PEEP were applied.Measurements and Main ResultsExtravascular lung water was determined by the double indicator dilution method (indocyanine green in glucoside solution at 0 degrees C), and lymphatic drainage was measured every 30 mins. After a baseline measurement, the left atrial pressure was increased to 24 to 26 mm Hg, and measurements were recorded after 30, 60, 90, and 120 mins. The animals were divided into three groups. Group I (n = 6): PEEP of 20 cm H2O was instituted at 120 mins, and the other determinations were made without PEEP; group II (n = 7): PEEP of 10 cm H2O was instituted at 60 and 90 mins; group III (n = 5): PEEP of 20 cm H2O was instituted at 60 and 90 mins. Extravascular lung water increased after the increase of left atrial pressure in all three groups. After 90 mins, the extravascular lung water was significantly greater (p < .01) in group I (no PEEP application) at 21.2 +/- 5.1 mL/kg than in groups II and III (with 10 and 20 cm H2O of PEEP) at 12.8 +/- 2.01 and 14.8 +/- 4.8 mL/kg, respectively.Lymphatic drainage tended to increase over time in all three groups.Ninety minutes after the left atrial pressure increase, lymphatic drainage was significantly greater (p < .05) in group II, at 6.06 +/- 2.53 mL/kg/30 mins, than in group I, at 2.83 +/- 0.76 mL/kg/30 mins.Conclusionsa) The application of PEEP levels of between 10 and 20 cm H2O limits the increase of extravascular lung water in cases of hydrostatic pulmonary edema; and b) the application of 10 cm H2O of PEEP increases the lymphatic flow through the thoracic duct.(Crit Care Med 1996; 24:1562-1567)

ISSN:0090-3493    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo predict extubation success and failure in mechanically ventilated infants and children using bedside measures of respiratory function.DesignProspective collection of data.SettingA university-affiliated children's hospital with a 51-bed critical care unit.PatientsAll infants and children who were mechanically ventilated for at least 24 hrs, except neonates <or=to37 wks gestation and patients with neuromuscular disease.InterventionsBedside measurements of cardiorespiratory function were obtained immediately before extubation.Measurements and Main ResultsExtubation failure was defined as reintubation within 48 hrs of extubation in the absence of upper airway obstruction. Failure rates were calculated for different ranges (selected a priori) of preextubation measures of breathing effort, ventilatory support, respiratory mechanics, central inspiratory drive, and integrated indices useful in adults. Effort of spontaneous breathing was assessed by the respiratory rate standardized to age, the presence of retractions and paradoxical breathing, inspiratory pressure, maximal negative inspiratory pressure (maximal negative inspiratory pressure), inspiratory pressure/maximal negative inspiratory pressure ratio, and tidal volume indexed to body weight of a spontaneous breath. Ventilatory support was measured by the fraction of inspired oxygen (FIO2), mean airway pressure, oxygenation index, and the fraction of total minute ventilation provided by the ventilator. Respiratory mechanics were assessed by determination of peak ventilatory inspiratory pressure and dynamic compliance. Central inspiratory drive was assessed by mean inspiratory flow. Frequency to tidal volume ratio and the compliance, rate, oxygenation, and pressure indexed to body weight, the integrated indices useful in predicting extubation failure in adults, were also calculated.Thirty-four of the 208 patients who were studied were reintubated for an overall failure rate of 16.3% (95% confidence interval 11.3% to 21.4%). The reasons for reintubation were poor effort (n = 8), excessive effort (n = 14), altered mental status or absent airway reflexes (n = 2), cardiovascular instability (n = 3), inadequate oxygenation (n = 3), respiratory acidosis (n = 3), and undocumented (n = 1). Extubation failure increased significantly with decreasing tidal volume indexed to body weight of a spontaneous breath, increasing FIO2or=to25%) of extubation failure could be determined for tidal volume indexed to body weight of a spontaneous breath, FIO2, mean airway pressure, oxygenation index, fraction of total minute ventilation provided by the ventilator, peak ventilatory inspiratory pressure, dynamic compliance, and mean inspiratory flow. Neither a low nor a high risk of failure could be defined for frequency to tidal volume ratio or the compliance, rate, oxygenation, and pressure (CROP) index.ConclusionsBedside measurements of respiratory function can predict extubation success and failure in infants and children. Both a low risk and a high risk of failure can be determined using these measures. Integrated indices useful in adults do not reliably predict extubation success or failure in infants and children.(Crit Care Med 1996; 24:1568-1579)

ISSN:0090-3493    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectivesTo summarize the available data on anterior pituitary function in critical illness and to focus on the endocrine effects of dopamine infusion. The analogy with anterior pituitary function in the elderly is highlighted, and the potential importance of these observations for recovery from critical illness is discussed.Data SourcesComputerized search of published research and reference list review.Study SelectionReview of 178 citations. Included are seven original studies on the effect of dopamine on pituitary function in adult and pediatric critical illness performed by the authors.Data ExtractionStudies on the endocrinology of illness, chronic stress, aging, and dopamine, or on the clinical importance of endocrine changes.Data SynthesisThe different pituitary axes are important determinants of normal anabolism and immune function. Continuously increased serum cortisol concentrations, insulin resistance, blunted prolactin release, and attenuated pulsatility of growth hormone and luteinizing hormone secretory patterns, as well as multiple anomalies in the thyroid axis, characterize the endocrine profile of prolonged critical illness. Dopamine, a natural catecholamine with hypophysiotropic properties, which has been used for more than two decades as an inotropic and vasoactive drug in intensive care, suppresses the circulating concentrations of all anterior pituitary-dependent hormones, except for cortisol. Available evidence suggests that the major effect of dopamine administration on the endocrine system is unlikely to be beneficial for the threatened metabolic and immunologic homeostasis of the severely ill patient. This pattern of hypopituitarism induced by chronic, severe illness and exogenous dopamine administration is reminiscent of the hormonal profiles obtained in experimental models of chronic stress, suggesting that endogenous dopamine may play a role in the endocrine and metabolic response to critical illness.ConclusionsThe dopamine-induced or aggravated pituitary dysfunction in critical illness warrants caution with prolonged infusion of this catecholamine as a so-called supportive agent, particularly in early life. The potential of combined hormonal therapy to improve the metabolic and immune status of the critically ill patient deserves thorough investigation.(Crit Care Med 1996; 24:1580-1590)

ISSN:0090-3493    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo determine the extent to which economic evaluations published in the critical care literature provide information that can help us to improve the efficiency of our unit.Data SourcesWe searched computerized bibliographic databases and manually searched key critical care journals to retrieve all economic evaluations.Study SelectionWe included economic evaluations that dealt with clinical problems relevant to the practice of adult critical care and that compared competing healthcare interventions.Data AbstractionIncluded articles were further evaluated using criteria for minimal methodologic soundness, adopted from the literature, and criteria that we developed to assess the generalizability of results to our clinical setting.Data Synthesis450 abstracts and titles in our computer search. One hundred fifty-one papers were retrieved for further evaluation; 29 papers met our inclusion criteria. Of these 29 papers, only 14 (48%) adequately described competing healthcare interventions, 17 (59%) provided sufficient evidence of clinical efficacy, six (21%) identified, measured, and valuated costs appropriately, and three (10%) performed a sensitivity analysis. None of the papers met all four of these criteria for a minimum level of methodologic soundness. Four (14%) of 29 studies which adequately dealt with issues of cost and efficacy were evaluated using our generalizability criteria. Different costing methods precluded the application of the results of three of the four studies to our intensive care unit.ConclusionsIn the critical care literature, very little useful economic information exists to help decision-makers maximize efficiency in their own setting.(Crit Care Med 1996; 24:1591-1598)

ISSN:0090-3493    

出版商:OVID    

年代:1996

数据来源: OVID

ISSN:0090-3493    

出版商:OVID    

年代:1996

数据来源: OVID

ISSN:0090-3493    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

ObjectiveTo review the efficacy of pressure-support ventilation in the management of children with status asthmaticus requiring mechanical ventilation.DesignA case series.SettingA university hospital.SubjectsChildren requiring mechanical ventilation due to respiratory failure despite medical therapy during an episode of acute asthma.InterventionsMechanical ventilation with pressure-support ventilation.Measurements and Main ResultsRespiratory parameters (ventilatory settings, minute ventilation, respiratory rate, airway pressures) and blood gases were determined before, on initiation, and for 6 hrs after pressure-support ventilation. Spontaneous ventilation with an initial respiratory rate of 45 breaths/min (range 31 to 46) and an inspiration/expiration ratio (I/E) of 1:1.2 (range 1:1.1 to 1:2) was readily established in each patient. Arterial pH normalized (7.41, range 7.39 to 7.43) within 6 hrs (4.25, range 2 to 6) of the time at which ventilation was begun and the Paco2decreased (p < .02) to 44 torr (range 39 to 47) (5.9 kPa, range 5.2 to 6.3) during pressure-support ventilation.ConclusionPressure-support ventilation permitted patient-cycled spontaneous ventilation in children with asthma. The ability of patients to determine their own respiratory pattern and to maintain forced exhalation during pressure-support ventilation may have important advantages in children with severe asthma who require mechanical ventilation. (Crit Care Med 1996; 24:1603-1605)

ISSN:0090-3493    

出版商:OVID    

年代:1996

数据来源: OVID

ISSN:0090-3493    

出版商:OVID    

年代:1996

数据来源: OVID

ISSN:0090-3493    

出版商:OVID    

年代:1996

数据来源: OVID