摘要:

ObjectiveWe hypothesized that an artificial neural network, interconnected computer elements capable of adaptation and learning, could accurately estimate pulmonary artery occlusion pressure from the pulsatile pulmonary artery waveform.SettingUniversity medical center.SubjectsNineteen closed-chest dogs.InterventionsPulmonary artery waveforms were digitally sampled before conventional measurements of pulmonary artery occlusion pressure under control conditions, during infusions of serotonin or histamine, or during volume loading. Individual beats were parsed or separated out. Pulmonary artery pressure, its first time derivative, and the beat duration were used as neural inputs. The neural network was trained by using 80% of all samples and tested on the remaining 20%. For comparison, the regression between pulmonary artery diastolic pressure and pulmonary artery occlusion pressure was developed and tested using the same data sets. As a final test of generalizability, the neural network was trained on data obtained from 18 dogs and tested on data from the remaining dog in a round-robin fashion.Measurements and Main ResultsThe correlation coefficient between the pulmonary artery diastolic pressure estimate of pulmonary artery occlusion pressure and measured pulmonary artery occlusion pressure was .75, whereas that for the neural network estimate of pulmonary artery occlusion pressure was .97 (p< .01 for difference between pulmonary artery diastolic pressure and pulmonary artery occlusion pressure estimates). The pulmonary artery diastolic pressure estimate of pulmonary artery occlusion pressure showed a bias of 0.097 mm Hg (limits of agreement −7.57 to 7.767 mm Hg), whereas the neural network estimate of pulmonary artery occlusion pressure showed a bias of −0.002 mm Hg (−2.592 to 2.588 mm Hg). There was no significant change in the bias of the neural network estimate over the range of values tested. In contrast, the bias for the pulmonary artery diastolic pressure estimate significantly increased with the increasing magnitude of the pulmonary artery occlusion pressure. During round-robin testing, the neural network estimate of pulmonary artery occlusion pressure showed suboptimal performance (correlation coefficient between estimated and measured pulmonary artery occlusion pressure .59).ConclusionsA neural network can accurately estimate pulmonary artery occlusion pressure over a wide range of pulmonary artery occlusion pressure under conditions that alter pulmonary hemodynamics. We speculate that artificial neural networks could provide accurate, real-time estimates of pulmonary artery occlusion pressure in critically ill patients.

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

ObjectiveTo study the relationship between arterial blood pressure, intracranial pressure, directly measured brain tissue oxygenation (Ptio2), and middle cerebral artery blood flow velocity in severely head-injured patients.DesignProspective study.SettingNeurosurgical intensive care unit.PatientsA total of 14 patients with severe head injury.InterventionsPharmacologic blood pressure manipulations using norepinephrine.Measurements and Main ResultsWe assessed the magnitude of Ptio2related to changes in cerebral perfusion pressure in 12 of the patients. We calculated in all the static rate of regulation, which is an index to describe the change of cerebrovascular resistance, using cerebral artery blood flow velocity in relation to changing cerebral perfusion pressure. Finally, we calculated the rate of change in Ptio2, which quantifies the percentage of change in Ptio2divided by the percentage of change in cerebral perfusion pressure. It is a new marker for cerebral tissue oxygen regulation based on direct measurement of Ptio2. There was a plateau phase for the cerebral perfusion pressure–Ptio2relation that was similar to the autoregulatory plateau seen in the relationship between cerebral perfusion pressure and cerebral artery blood flow velocity. The rate of change in Ptio2demonstrated a significant correlation with the static rate of regulation (R= −.61,p< .05). A decrease in intracranial pressure when arterial blood pressure increased from 70 to 90 mm Hg was strongly correlated with static rate of regulation (R= .79,p< .001).ConclusionsCerebral tissue Po2demonstrates a plateau phase similar to what is known about cerebral blood flow velocity, which suggests a close link between cerebral blood flow and oxygenation. Static cerebral autoregulation is significantly correlated with cerebral tissue oxygen reactivity.

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

ObjectiveTo determine the time interval between symptom onset and neurologic deterioration related to cerebral edema in patients with massive middle cerebral artery infarction. The time period between onset and neurologic deterioration represents the window for surgical intervention.DesignMulticenter retrospective chart review.SettingsFive university-affiliated medical centers.PatientsFifty-three patients with massive middle cerebral artery infarction who experienced neurologic deterioration defined by a decrease in the Glasgow Coma Scale score of two or more points attributable to mass effect.Measurements and Main ResultsA total of 53 patients (mean age, 62 ± 18 yrs; 25 [47%] were men) with neurologic deterioration were identified by using International Classification of Diseases (9th revision) codes and local registries. Medical records and neuroimaging studies were reviewed by a stroke neurologist or neurointensivist to identify the time of neurologic deterioration. Thrombolytics were used at presentation in 19 (35%) patients. A total of 19 (36%) patients had neurologic deterioration within 24 hrs of symptom onset. By 48 hrs, 36 (68%) patients had manifested clinical deterioration. A few patients had later neurologic deterioration on day 3 (n = 10), day 4 (n = 2), day 5 (n = 2), and day 6 or after (n = 3). A total of 25 (47%) of the 53 patients died during hospitalization. The highest frequency of deaths occurred on day 3.ConclusionsNeurologic deteriorations related to cerebral edema after massive middle cerebral artery infarction occur in most patients within 48 hrs of symptom onset.

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

ObjectiveAlthough mechanical ventilation is required in 30% of patients with Guillain-Barré syndrome, early predictors of this treatment remain unknown.DesignAnalysis of two cohorts of patients enrolled in two multicenter randomized clinical trials.SettingFrench intensive care and neurologic units.MeasurementsDemographic, neurologic, and biologic data; vital capacity; and time of onset, admission, and endotracheal mechanical ventilation were collected.ResultsAmid 722 consecutive adults not ventilated at admission, endotracheal mechanical ventilation was required in 313 (43%) patients. Multivariate analyses identified six predictors of endotracheal mechanical ventilation: time from onset to admission of <7 days (odds ratio, 2.51), inability to cough (odds ratio, 9.09), inability to stand (odds ratio, 2.53), inability to lift the elbows (odds ratio, 2.99) or head (odds ratio, 4.34), and liver enzyme increases (odds ratio, 2.09). In the 196 (27%) patients whose vital capacity was measured, time from onset to admission of <7 days (odds ratio, 5.00), inability to lift the head (odds ratio, 5.00), and vital capacity <60% (odds ratio, 2.86) predicted endotracheal mechanical ventilation.ConclusionsPatients with at least one of these predictors should be monitored in an intensive care unit. Mechanical ventilation was required in >85% of patients with at least four predictors from the first multivariate model and in 85% of patients with all three predictors from the second multivariate model. In these patients at high risk of respiratory failure, the value of early mechanical ventilation may deserve investigation.

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

ObjectiveThe aim of the present study was to characterize pulmonary surfactant properties in children undergoing cardiovascular surgery with cardiopulmonary bypass.DesignProspective clinical trial.SettingUniversity hospital pediatric intensive care unit.PatientsFifty pediatric patients with congenital cardiac defects undergoing cardiovascular surgery with (n = 35) and without (n = 15) cardiopulmonary bypass procedure.InterventionsTracheal aspirates were collected by saline lavage during routine suctioning before (baseline) and after cardiopulmonary bypass, as well as 4, 8, and 24 hrs after admission to the pediatric intensive care unit.Measurements and Main ResultsTotal protein and phospholipid concentrations were assessed in native tracheal aspirates, in large surfactant aggregates, and in small surfactant aggregates. Phospholipid profiles and phosphatidylcholine fatty acids; surfactant apoproteins SP-A, SP-B, and SP-C (enzyme-linked immunosorbent assay); and surface activity (Pulsating Bubble Surfactometer) were all analyzed in large surfactant aggregates. With cardiopulmonary bypass, an initial increase in total protein content was followed by an increase in phospholipid concentration in tracheal aspirates. Large surfactant aggregates decreased 4 hrs after cardiopulmonary bypass (4 hrs, 22.6 ± 5.6%; mean ± sem;p< .01 compared with baseline, 55.4 ± 9.2%) but recovered within 24 hrs. The phospholipid-protein ratio of large surfactant aggregates 24 hrs after cardiopulmonary bypass (1.2 ± 0.2;p< .01) was significantly decreased compared with baseline (2.9 ± 0.6). The relative amount of phosphatidylglycerol content in the large surfactant aggregates-fraction dropped linearly over time but other phospholipids remained mainly unchanged. Phosphatidylcholine fatty acid profiles remained unaffected by cardiopulmonary bypass. The relative content of SP-B and SP-C in large surfactant aggregates increased approximately three-fold compared with baseline. Altogether, our findings with recovered large surfactant aggregate/small surfactant aggregate ratios and increased phospholipid in tracheal aspirates after 24 hrs represent an approximately ten-fold increase in large surfactant aggregate-associated SP-B and SP-C compared with baseline. Only minor changes were detected in biophysical properties of large surfactant aggregates throughout the observation period.ConclusionsCardiopulmonary bypass procedure in children induces profound changes in the surfactant system involving both phospholipid and protein components; biophysical function may have been maintained by compensatory increase in SP-B and SP-C.

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

ObjectiveTo identify a consensus of opinion regarding the content of an intensive care core syllabus for undergraduate medical students and factors that may limit its teaching.DesignCross-sectional postal survey containing 35 items ranging from department structure to curriculum content and factors that limit the teaching of intensive care.SettingEnglish-speaking medical schools (n = 210) listed in the 1986 World Health Organization Directory.Measurements and Main ResultsOf 122 (58%) returned questionnaires, a 45% return was achieved from the United States and 86% from non-U.S. countries. Most respondents (84%) considered teaching undergraduate intensive care to be essential; however, teaching intensive care was compulsory in only 31% of schools. Many schools (43%) reported recent changes to their intensive care curriculum. Most respondents (60%) thought that intensive care specialists should teach and that each student required a median (interquartile range) of 20 (10–80) hrs of teacher contact time. Resuscitation skills were taught in 98% of schools. In comparison, 63% of schools had no intensive care syllabus. More than 90% of respondents thought that the intensive care syllabus should include the following: cardiopulmonary resuscitation, assessment and management of the acutely ill patient; management of respiratory, circulatory, and multiple organ system failure (including systemic inflammatory response syndrome and sepsis); management of the unconscious patient; early postoperative care; and communication skills and ethics as they relate to end-of-life issues. Factors that limited intensive care teaching were lack of staff, funding, and time dedicated to teaching and excessive clinical workload. Student performance in intensive care was assessed by 66% of schools, but only 28% used a written or oral examination.ConclusionsBy surveying a wide range of medical schools internationally, we have been able to define an undergraduate intensive care syllabus that could be delivered in 20 hrs or 1 wk of dedicated teaching time. Factors that impede the provision of undergraduate intensive care teaching are a lack of staff, funding, and dedicated teaching time.

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID

摘要:

ObjectivesTo summarize and compare different prognostic criteria used to determine need for liver transplantation in patients with fulminant hepatic failure secondary to acetaminophen poisoning.Data SourcesStudies published in the literature that investigated criteria for hepatic transplantation secondary to acetaminophen-induced liver failure as identified by a preestablished MEDLINE strategy (1966 through October 2001).Study SelectionStudies were included if 2 × 2 tables could be reconstructed and if they did not assume that patients undergoing transplantation would have eventually died had they not received the transplant.Data ExtractionRelevant articles were reviewed by two authors independently. Discrepancies or disagreements, if any, on the inclusion or exclusion of studies were resolved by consulting the third author.Data SynthesisKing’s criteria (pH < 7.30 or prothrombin time of >100 secs plus creatinine of >300 &mgr;mol/L plus encephalopathy grade of ≥3) were evaluated in nine studies, pH < 7.30 in four, prothrombin time of >100 secs in three, prothrombin time of >100 secs plus creatinine of >300 &mgr;mol/L plus encephalopathy grade of ≥3 in three, creatinine of >300 &mgr;mol/L in two, and one each for increase in prothrombin time day 4, factor V of <10%, Acute Physiology and Chronic Health Evaluation (APACHE) II score of >15, and Gc-globulin of <100 mg/L. King’s criteria were more sensitive than pH: 69% (95% confidence interval, 63–75) vs. 57% (95% confidence interval, 44–68). Their specificities were, however, comparable: 92% (95% confidence interval, 81–97) vs. 89% (95% confidence interval, 62–97). APACHE II score of >15 had the highest positive likelihood ratio (16.4) and the lowest negative likelihood ratio (0.19) but was evaluated in only one study. The accuracy measures of all other criteria were lower than that of King’s criteria or pH < 7.30.ConclusionsPresently, available criteria are not very sensitive and may miss patients requiring transplantation. Future studies should further evaluate the efficacy of the APACHE II criteria.

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID

ISSN:0090-3493    

出版商:OVID    

年代:2003

数据来源: OVID