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Biomedical subjects

B L Short

Publications and source records attributed to B L Short.

At least 73 records · Page 4Linked to original sources
PubMed1989

Cardiac determinants of cerebral blood flow during extracorporeal membrane oxygenation.

Doppler recordings of the pericallosal artery (PCA) and echocardiographic examinations were performed on nine infants before, and at 24-, 72-, and 96-hour intervals during extracorporeal membrane oxygenation (ECMO). Systolic indices of left ventricular (LV) function, as well as mean blood flow velocity and pulsatility in the PCA, were measured. Arterial blood gases and blood pressure were monitored. LV cardiac output and LV stroke volume decreased during early ECMO and returned toward baseline as ECMO flow rates decreased. In the PCA, changes in pulsatility paralleled changes in ventricular performance. Pulsatility decreased during early ECMO and returned toward baseline with time. There was an inverse relationship between mean blood flow velocity in the PCA and ventricular function during early ECMO. Mean blood flow velocity increased during early ECMO and returned toward baseline as ECMO flow rates decreased. Early changes in mean blood flow velocity were associated with an initial increase in arterial pO2, pCO2, and mean blood pressure. Total aortic flow (ECMO flow + LV cardiac output in cc/kg), arterial blood gases, and mean blood pressure remained unchanged during prolonged ECMO. These data suggest that the pulsatility of cerebral blood flow is related to cardiac function during partial bypass and that the regulation of cerebral blood flow during prolonged bypass may be dependent on the presence of pulsatile flow.

Aorta, Thoracic↗
PubMed1989

CT of cerebrovascular injury after neonatal extracorporeal membrane oxygenation: implications for neurodevelopmental outcome.

One hundred forty-six neonates treated with extracorporeal membrane oxygenation (ECMO) were evaluated with cranial sonography and CT at different times in the course of their disease. Cranial sonography was performed during treatment with ECMO, and CT was done 3-14 days after cessation of ECMO bypass. In 66 (45%), intracranial abnormalities were detected with either sonography or CT. Thirty neonates had hemorrhages only, 24 had nonhemorrhagic abnormalities, and 12 had combined lesions. CT provided additional information in 44 (67%) of the 66 neonates. Sonography was normal in 37 neonates, showed fewer lesions in 10 neonates, and was concordant with CT findings in 14 neonates. It cannot be established whether these lesions went undetected with sonography during ECMO, or occurred after cessation of ECMO bypass. Neurodevelopmental evaluation was performed in 71 of 90 survivors 1 year of age or older. Forty-three infants (61%) were normal; developmental delay was suspected in 12 (17%) and present in 16 (23%). The severity of intracranial abnormality as determined by a neuroimaging score correlated well with short-term developmental outcome. Mean neuroimaging scores were significantly higher, with increasing degree of neurodevelopmental delay (p less than .001 by Kruskal-Wallis rank order test). Although cranial sonography remains the primary technique for the detection of life-threatening hemorrhage during ECMO, cranial CT after ECMO is important in defining the total degree of intracranial injury present in these high-risk neonates.

Cerebral Hemorrhage↗
PubMed1989

Cerebrovascular accidents in neonates treated with extracorporeal membrane oxygenation: sonographic-pathologic correlation.

Neonates treated with extracorporeal membrane oxygenation are at high risk for the development of intracranial hemorrhage and infarction. The appearance of these lesions on cranial sonography is often unusual and may be confusing. We compared the findings at autopsy with premorbid cranial sonograms in 17 nonsurviving neonates to define better the anatomic basis for the sonographic appearance of these lesions. Macroscopic abnormalities were identified at autopsy in 13 of the 17 neonates. Five neonates had multifocal hemorrhagic white-matter infarcts, three had large parenchymal hemorrhages with adjacent areas of parenchymal necrosis, three had hemorrhagic infarcts of the cerebellum, one had a germinal matrix and intraventricular hemorrhage, and one had bilateral periventricular cysts with surrounding gliosis. All 17 neonates had abnormalities on microscopic examination. Although sonography was accurate in the detection of macroscopic lesions (11 of 13 lesions detected with sonography), the nature and extent of these abnormalities were difficult to judge because of the variable echogenicity of unclotted blood and the presence of focal areas of abnormal echogenicity associated with microscopic calcification and gliosis. Sonography is excellent for the detection of acute cerebrovascular complications during extracorporeal membrane oxygenation, but the appearance of these lesions is variable and nonspecific.

Brain↗
PubMed1988

Doppler echocardiographic evaluation of cardiac performance in infants on prolonged extracorporeal membrane oxygenation.

Cardiac performance was evaluated by Doppler echocardiography in 19 infants with persistent pulmonary hypertension before, during and after prolonged extracorporeal membrane oxygenation (ECMO). Systemic arterial pressure was normal before ECMO (67 +/- 12 mm Hg), increased during ECMO (78 +/- 13 mm Hg) and decreased to baseline after ECMO (p less than or equal to 0.01). Heart rate was normal before ECMO and did not change during or after ECMO. The left ventricular shortening fraction was normal before ECMO (37 +/- 11%), decreased after beginning ECMO (25 +/- 11%) and returned to baseline 72 hours after beginning ECMO (p less than or equal to 0.01). Pulmonary arterial and aortic blood flow velocities were normal before ECMO, decreased 30 to 50% during ECMO and increased to baseline 72 hours after beginning ECMO (p less than or equal to 0.01). Stroke volume had an identical trend (p less than or equal to 0.01). Left ventricular velocity of circumferential shortening--an index of contractility--decreased after beginning ECMO (p less than or equal to 0.05). Left ventricular systolic wall stress--an index of systemic afterload--increased after beginning ECMO (p less than or equal to 0.01). A patent ductus arteriosus was present in 13 of 19 infants before ECMO, 16 of 19 infants during ECMO and in none of 19 infants after ECMO. Pulmonary arterial systolic pressure was high before ECMO (72 +/- 25 mm Hg), began to decrease after 48 hours on ECMO (59 +/- 24 mm Hg) and was normal after ECMO (38 +/- 18 mm Hg), p less than or equal to 0.05.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1988

Cerebral hemodynamics in infants undergoing extracorporeal membrane oxygenation: further observations.

Intracranial Doppler ultrasonographic examinations were performed on 64 infants treated with extracorporeal membrane oxygenation (ECMO). Serial studies were performed on the anterior cerebral artery in 55 infants before and during ECMO bypass, and on the middle cerebral arteries (MCAs) and internal carotid arteries (ICAs) on an additional nine infants. The onset of ECMO was associated with changes in character of pulsatile flow, direction of flow, and mean blood-flow velocity. Pulsatility decreased in all patients, and mean blood-flow velocity increased in 73% of patients (mean change from baseline, 87%). Despite retrograde flow in the right ICA in five of nine infants, antegrade flow to the right MCA was preserved in all cases. We found no correlation between alterations in mean blood-flow velocity and overall mortality, frequency of intracranial hemorrhage, and neuro-developmental outcome. These data suggest that wide variations in cerebral blood flow occur with ECMO therapy, and that these changes appear to be well tolerated.

Blood Flow Velocity↗
PubMed1988

Group B streptococcal (GBSS) newborn septic shock model: the role of prostaglandins.

Group B beta hemolytic streptococcal sepsis has many of the characteristics of gram negative sepsis (Hellerqvist, et al., 1981). This is further shown in the model developed for this study. The newborn piglet septic model developed for this study appears to be an adequate model for group B, beta-streptococcal sepsis characterized by the development of significant hypotension by six hours. As with human sepsis, this model develops hypoglycemia, hemoconcentration as noted by the increased hematocrit, thrombocytopenia and a significant drop in WBC with an increase in immature forms (Wilson, 1986). The only finding not correlated to the septic newborn is the development of DIC as characterized by an increased PT/PTT and increased FSP. As with other animal models for both gram positive and negative sepsis, the cyclooxygenase inhibitor, indomethacin significantly increased survival out to 72 hours. Previous studies with thromboxane synthetase inhibitors have not shown increased survival, but shunting into the prostacyclin pathway has occurred and the effect of this on survival could not be ruled out (Short, et al., 1983). The use of a thromboxane receptor site antagonist should not cause this shunt, and thus may help to evaluate the effect of thromboxane blockade. In this model no effect of the receptor site antagonist was noted, but due to the short half-life of this compound, a different dosing schedule may be needed before its efficacy can be determined. In summary, the cyclooxygenase inhibitors do appear to have a protective effect in gram positive sepsis, but the mechanisms of action are still to be determined.

Animals↗
PubMed1987

Lung compliance as a measure of lung function in newborns with respiratory failure requiring extracorporeal membrane oxygenation.

Extracorporeal membrane oxygenation (ECMO) can now be used as an alternative mode of therapy for infants 2.0 kg or more with life-threatening respiratory failure. Current criteria for removal from ECMO are limited. We attempted to determine whether lung compliance (CL) could be used as a sensitive indicator of the neonates' lung improvement while they are on ECMO, as well as a predictor of their ability to tolerate removal from bypass. We obtained serial CL measurements in 13 infants, all of whom weaned successfully from ECMO. All had an initial CL on ECMO of 0.5 ml/cm H2O X kg or less (mean = 0.3), with a final CL of 0.8 ml/cm H2O X kg or more (mean = 1.7). The average change in CL from the initial to the final measurement was 0.6 ml/cm H2O X kg or more (mean = 1.5). CL findings correlated well with estimated bypass, expressed as a percent of cardiac output, and a radiographic score of pulmonary abnormality (r = -.66, p less than .0001, and r = -.52, p less than .0001, respectively). We conclude that CL measurements can be used to monitor clinical improvement in infants on ECMO, to predict their successful removal from bypass, and ultimately to shorten their total time spent on bypass.

Cardiac Output↗
PubMed1987

Intracranial flow patterns in infants undergoing extracorporeal membrane oxygenation: preliminary observations with Doppler US.

Transcutaneous Doppler ultrasound was used to monitor changes in intracranial hemodynamics in 13 infants undergoing extracorporeal membrane oxygenation (ECMO). Recordings for the pericallosal portion of an anterior cerebral artery were obtained before ECMO and daily during ECMO bypass, with use of a range-gated, pulsed Doppler imaging system. Obvious changes occurred with the onset of ECMO: the systolic phase broadened, and diastolic flow velocities markedly increased. The mean pulsatility value, as measured with the Pourcelot pulsatility index, decreased significantly at the start of ECMO and over time during ECMO bypass. Marked increases in the area under the velocity curve (AUTC) were also observed with the institution of ECMO bypass (mean percentage change in AUTC from baseline, 133%). Factors that appeared to affect AUTC included PCO2, mean blood pressure, and ECMO bypass rate. AUTC tended to decrease during the course of ECMO. Although the clinical significance of these findings remains unclear, the data indicate that ECMO bypass is associated with marked changes in intracranial hemodynamics.

Cerebrovascular Circulation↗
PubMed1987

Intracranial abnormalities in infants treated with extracorporeal membrane oxygenation: imaging with US and CT.

Findings at neuroimaging in 100 consecutive infants treated with extracorporeal membrane oxygenation (ECMO) are presented. Imaging in these infants consisted of pretreatment cranial ultrasonography (US), daily US studies while on ECMO, and follow-up cranial computed tomography (CT) after treatment. There were findings of abnormalities in 43 patients. Thirty had intracranial bleeding, often of unusual extent and distribution. Thirteen additional infants had nonhemorrhagic abnormalities alone. Bleeding considered to be major was seen in 12% of infants. Large parenchymal hemorrhages and infarcts, cerebellar hemorrhages, and diffuse edema were the most significant abnormalities, with a 50% mortality (eight of 16 patients). No lateralization was noted with respect to distribution of bleeding sites or areas of nonhemorrhagic abnormalities. US was a sensitive but imperfect screening tool for intracranial abnormalities. Abnormalities missed with US included peripheral and small parenchymal lesions, subarachnoid hemorrhage, cerebral atrophy, and sagittal sinus thrombosis.

Brain↗
PubMed1986

Criteria for extracorporeal membrane oxygenation in a population of infants with persistent pulmonary hypertension of the newborn.

Extracorporeal membrane oxygenation (ECMO) has been available since 1975 as a therapy of last resort to provide adequate oxygenation for term infants with acute lung disorders that do not respond to maximal medical therapy. Virtually all term infants with serious lung disease have persistent pulmonary hypertension of the newborn (PPHN) characterized by significant right-to-left shunting of blood and severe diffusion defects manifested as increased alveolar-arterial oxygen gradients (AaDO2). Criteria for initiation of ECMO therapy have been developed in several institutions but at the present time there are no universal criteria applicable to all infants with PPHN. We have attempted to establish entry criteria that may be used for different populations of infants with PPHN. Based on a retrospective review of 30 infants with PPHN in our institution, we have defined standards of maximal medical therapy. An alveolar-arterial oxygen difference (AaDO2) of greater than or equal to 610 for 8 hours has been shown to be associated with 79% mortality in this population. This AaDO2/time interval is established as a major criterion for institution of extracorporeal membrane oxygenation.

Carbon Dioxide↗
PubMed1986

Diffuse pulmonary opacification in infants undergoing extracorporeal membrane oxygenation: clinical and pathologic correlation.

Diffuse pulmonary opacification is commonly seen on chest radiographs from infants with severe respiratory failure treated with extracorporeal membrane oxygenation (ECMO). The chest radiographs and clinical records of 18 such infants were reviewed to determine the correlation among degree of abnormality on chest radiograph (as determined by a radiographic score), clinical severity of disease (as measured by ECMO requirements [ECMO flow rate]), and dynamic lung compliance determinations. Increasing lung compliance and decreasing ECMO flow rates correlated well with decreasing (improving) radiographic score. Pathologic changes were mainly those associated with intensive respiratory support and the underlying pulmonary condition. One patient had diffuse pulmonary hemorrhage. Other than bleeding, no distinctive pathologic features could be attributed to therapy with ECMO. We conclude that the degree of pulmonary opacification seen in infants undergoing ECMO therapy is an accurate reflection of markedly decreased lung compliance and lung volumes caused by hyaline membrane formation, pulmonary edema, and atelectasis associated with the various causes of severe respiratory failure.

Extracorporeal Circulation↗
PubMed1986

Extracorporeal membrane oxygenation: radiographic appearance of the neonatal chest.

The chest radiographs of 26 newborns treated with extracorporeal membrane oxygenation (ECMO) for intractable respiratory failure were reviewed. The typical radiographic appearance of the lungs in these patients is that of diffuse pulmonary opacification with variable volume loss. Air bronchograms and patchy basilar atelectasis are also common findings. Generally, decreasing ECMO requirements were reflected in improving chest radiographs with radiographic improvement lagging behind clinical improvement. Of 167 chest radiographs available for evaluation, 105 (62.8%) reflected changes in ECMO flow rates. Radiographs in patients with individual diagnoses of hyaline membrane disease, meconium aspiration syndrome and sepsis showed the best correlation with clinical improvement (95 [69%] of 137 radiographs). Those obtained in patients with congenital diaphragmatic hernia and persistent pulmonary hypertension of the newborn alone showed the poorest correlation (10 [30%] of 30 of radiographs). Neither the absolute degree of radiographic abnormality nor degree of radiographic improvement correlated well with ECMO requirements. Initial radiographs were useful in confirming the position of bypass cannulae and respiratory tubes. Routine daily examinations did not reveal unexpected abnormalities. However, radiographs taken during periods of increased ECMO requirements due to patent ductus arteriosus or volume overload showed worsening lung opacification.

Humans↗