The risk and burden of thromboembolic and hemorrhagic events in patients with malignant gliomas receiving bevacizumab.

PURPOSE: Bevacizumab has evolved as an integral treatment option for patients with high-grade gliomas. Little is known about clinical risk factors that predispose patients with high-grade gliomas receiving bevacizumab to VTE or ICH. We sought to characterize the clinical risk factors associated with risk of either event. METHODS: In this multi-institutional retrospective study, we first evaluated patients with high-grade gliomas who were treated with bevacizumab at University of Texas MD Anderson Cancer Center from 2015-2021. We compared clinical and treatment-related factors among three cohorts: those who developed VTE, ICH, or neither. We further compared survival outcomes of these patients from the time of bevacizumab initiation. Then to further confirm our results in a non-cancer center hospital setting we evaluated patients from two Ascension Seton Hospitals in Austin, Texas which are affiliated with Dell Medical School at the University of Texas at Austin from 2017-2022. RESULTS: We found that the presence of cerebral macrobleeding, defined as a magnetic susceptibility of > 1 cm3 on magnetic resonance imaging, was highly associated with risk of developing ICH after initiation of bevacizumab. Development of ICH was significantly associated with poorer survival outcomes. We did not find a statistically significant effect of VTE on survival after bevacizumab initiation. CONCLUSION: In order to stratify the risk for developing ICH before the initiation of bevacizumab, we recommend to assess for the presence of cerebral macrobleeding as it is associated with ICH development.

Recent Therapeutic Advances in Pituitary Carcinoma.

Pituitary carcinoma (PC) is a rare, aggressive malignancy that comprises 0.1-0.2% of all pituitary tumors. PC is defined anatomically as a pituitary tumor that metastasizes outside the primary intrasellar location as noncontiguous lesions in the central nervous system or as metastases to other organs. Similar to pituitary adenoma, PC originates from various cell types of the pituitary gland and can be functioning or nonfunctioning, with the former constituting the majority of the cases. Compression of intricate skull-based structures, excessive hormonal secretion, impaired pituitary function from therapy, and systemic metastases lead to debilitating symptoms and a poor survival outcome in most cases. PC frequently recurs despite multimodality treatments, including surgical resection, radiotherapy, and biochemical and cytotoxic treatments. There is an unmet need to better understand the pathogenesis and molecular characterization of PC to improve therapeutic strategies. As our understanding of the role of signaling pathways in the tumorigenesis of and malignant transformation of PC evolves, efforts have focused on targeted therapy. In addition, recent advances in the use of immune checkpoint inhibitors to treat various solid cancers have led to an interest in exploring the role of immunotherapy for the treatment of aggressive refractory pituitary tumors. Here, we review our current understanding of the pathogenesis, molecular characterization, and treatment of PC. Particular attention is given to emerging treatment options, including targeted therapy, immunotherapy, and peptide receptor radionuclide therapy.

Characterization of recurrence patterns and outcomes of medulloblastoma in adults: The University of Texas MD Anderson Cancer Center experience.

Background: Medulloblastoma in adults is rare and treatment decisions are largely driven from pediatric literature. We sought to characterize recurrent medulloblastoma in adults. Methods: From a single-institution dataset of 200 adult patients diagnosed with medulloblastoma during 1978-2017, those with recurrence were analyzed for clinical features, treatment, and outcome. Results: Of the 200 patients, 82 (41%) with median age of 29 years (18-59) had recurrence after a median follow-up time of 8.4 years (95% CI = 7.1, 10.3). Of these, 30 (37%) were standard-risk, 31 (38%) were high-risk, and 21 (26%) had unknown-risk diseases at the time of initial diagnosis. Forty-eight (58%) presented with recurrence outside the posterior fossa, of whom 35 (43%) had distant recurrence only. Median Progression-free survival (PFS) and OS from initial surgery were 33.5 and 62.4 months, respectively. Neither PFS nor OS from initial diagnosis differed between the standard-risk and high-risk groups in those who experience recurrence (P = .505 and .463, respectively). Median OS from first recurrence was 20.3 months, also with no difference between the standard-risk and high-risk groups (P = .518). Recurrences were treated with combinations of re-resection (20 patients; 25%), systemic chemotherapy (61 patients; 76%), radiation (29 patients; 36%), stem cell transplant (6 patients; 8%), and intrathecal chemotherapy (4 patients; 5%). Patients who received radiation at recurrence had better OS (32.9 months) than those who did not (19.2 months) (P = .034). Conclusions: Recurrent medulloblastoma in adults has a poor prognosis irrespective of initial risk stratification. Recurrence commonly arises outside the posterior fossa years after initial diagnosis.

Impact of neurofibromatosis type 1 in an adult community population.

Background: Neurofibromatosis type 1 (NF1) is a common tumor predisposition syndrome with varying manifestations and severity. Adult NF1 patients often experience fragmented care, so we sought to characterize the health and demographic features of a community-based population of adults with NF1 and hypothesized that lack of a specialty clinic for adult NF1 patients correlates with unmet needs. Methods: Retrospective case-control study of all adult cases of NF1 among 4.06 million medical records in a Pacific Northwest population. 122 case charts were reviewed to ascertain NF1 disease features, comorbidities, and severity of disease. A 1:1 control cohort was selected by matching case/control by age, sex, and ZIP code to compare demographic features and health status. Results: Adult NF1 patients were less likely to have private insurance, be employed, and have children, but were equally likely to be married. One half of cases had disease features compromising health and well-being, and care involved 26 different specialties. Excluding neurofibromas, 43% of cases had cancer compared to 10% of controls [P < .0001, OR 5.38 (2.53-11.4)]. Only 27% of women ages 30-50 had undergone age-appropriate enhanced breast cancer surveillance. Behavioral health problems were found in 60% of NF1 patients compared to 37% of controls [P < .001, OR 2.61 (1.52-4.50)]. 93% of cases referred to a NF1 specialty center underwent a change in management upon establishing care. Conclusions: NF1 patients may benefit from coordinated management of care in a specialty center.

Adult pilocytic astrocytoma in the molecular era: a comprehensive review.

Adult pilocytic astrocytoma (PA) is less prevalent than pediatric PA and is associated with a worse prognosis. In a literature review, we found that 88.3% of the molecular alterations in adult PA are associated with MAPK pathway dysregulation. The most common alterations are fusions of BRAF. Understanding of the mechanisms underlying this pathway has evolved substantially, heralding advancements in specific targeted therapy. Here, we review clinical and molecular features of adult PA, characteristics predicting aggressive behavior and approaches to standard and investigational therapies. We highlight epigenetic profiling and integrated diagnosis as an essential component of classifying PA.

Patient-specific 3D-printed Splint for Mallet Finger Injury.

Despite the frequency of mallet finger injuries, treatment options can often be costly, time-consuming, and ill-fitted. Three-dimensional (3D) printing allows for the production of highly customized and inexpensive splints, which suggests potential efficacy in the prescription of casts for musculoskeletal injuries. This study explores how the use of engineering concepts such as 3D printing and topology optimization (TO) can improve outcomes for patients. 3D printing enables the direct fabrication of the patient-specific complex shapes while utilizing finite element analysis and TO in the design of the splint allowed for the most efficient distribution of material to achieve mechanical requirements while reducing the amount of material used. The reduction in used material leads to significant improvements in weight reduction and heat dissipation, which would improve breathability and less sweating for the patient, greatly increasing comfort for the duration of their recovery.

Primordial formation of major silicates in a protoplanetary disc with homogeneous 26Al/27Al.

Understanding the spatial variability of initial 26Al/27Al in the solar system, i.e., (26Al/27Al)0, is of prime importance to meteorite chronology, planetary heat production, and protoplanetary disc mixing dynamics. The (26Al/27Al)0 of calcium-aluminum-rich inclusions (CAIs) in primitive meteorites (~5 × 10-5) is frequently assumed to reflect the (26Al/27Al)0 of the entire protoplanetary disc, and predicts its initial 26Mg/24Mg to be ~35 parts per million (ppm) less radiogenic than modern Earth (i.e., Δ'26Mg0 = -35 ppm). Others argue for spatially heterogeneous (26Al/27Al)0, where the source reservoirs of most primitive meteorite components have lower (26Al/27Al)0 at ~2.7 × 10-5 and Δ'26Mg0 of -16 ppm. We measured the magnesium isotope compositions of primitive meteoritic olivine, which originated outside of the CAI-forming reservoir(s), and report five grains whose Δ'26Mg0 are within uncertainty of -35 ppm. Our data thus affirm a model of a largely homogeneous protoplanetary disc with (26Al/27Al)0 of ~5 × 10-5, supporting the accuracy of the 26Al→26Mg chronometer.

Subacute combined degeneration: a case of pernicious anaemia without haematological manifestations.

Vitamin B12 deficiency can be caused by a diverse group of aetiologies. One of the less common of these is an autoimmune condition pernicious anaemia, so named after the most common physiological manifestation of B12 deficiency: anaemia. However, B12 is also necessary for nervous system function and its depletion can lead to dysfunction of the posterior columns of the spinal cord resulting in subacute combined degeneration (SCD). This disease, while debilitating in its acute phase, can usually be mostly if not fully reversed if caught early and treated appropriately. Early detection can prove challenging if there are no haematological manifestations of B12 deficiency and the only guidance is the high index of suspicion. We present a case of pernicious anaemia leading to SCD without any clinical or laboratory findings of anaemia in this report.

Deposition of Aerosolized Lucinactant in Nonhuman Primates.

Background: Lucinactant for inhalation is an investigational noninvasive, aerosolized surfactant replacement therapy for treatment of preterm neonates with respiratory distress syndrome. Lucinactant for inhalation consists of lyophilized lucinactant and the Aerosurf® Delivery System (ADS). The objective of this study was to characterize the total and regional pulmonary deposition of lucinactant delivered by the ADS in nonhuman primates (NHPs). Methods: Lucinactant was radiolabeled by the addition of technetium-99m (99mTc)-sulfur colloid. The radiolabeled aerosol was characterized and validated using a Mercer cascade impactor. An in vivo deposition study was performed in three cynomolgus macaques. Radiolabeled lucinactant was aerosolized using the ADS and delivered via nasal cannula under 5 cm H2O nasal continuous positive airway pressure (nCPAP) for 5-9 minutes. A two-dimensional planar image was acquired immediately after aerosol administration, followed by a three-dimensional single-photon emission computed tomography (SPECT) image and a second planar image. The images were analyzed to determine the pulmonary (lungs) and extrapulmonary (nose + mouth, trachea, stomach) distribution. The SPECT data were used to determine regional deposition. Results: The radiolabed lucinactant aerosol had a mass median aerodynamic diameter = 2.91 µm, geometric standard deviation (GSD) = 1.81, and an activity median aerodynamic diameter = 2.92 µm, GSD = 2.06. Aerosolized lucinactant was observed to deposit in the lungs (11.4%), nose + mouth (79.9%), trachea (7.3%), and stomach (1.4%). Analysis of the SPECT image demonstrated that the regional deposition within the lung was generally homogeneous. Aerosolized lucinactant was deposited in both the central (52.8% ± 1.2%) and peripheral (47.2% ± 1.2%) regions of the lungs. Conclusion: Aerosolized lucinactant, delivered using the ADS via constant flow nCPAP, is deposited in all regions of the lungs demonstrating that surfactant can be aerosolized and delivered noninvasively to NHPs.

Hemiencephalitis: a hyperaemic presentation of Hashimoto's encephalopathy.

There are many examples in the literature of Hashimoto's encephalopathy (HE) presenting with heterogeneous manifestations to include stroke-like episodes, seizures, myoclonus and psychiatric symptoms. The pathogenesis is poorly understood but is thought to involve an autoimmune-mediated vasculitis. Here, we present a novel case showing hemispheric hyperaemia which created a diagnostic challenge and insinuated a vascular mechanism for the condition. The patient presented with left-sided stroke-like symptoms and had head CT angiography notable for asymmetric vasculature initially interpreted radiographically as decreased left middle cerebral artery (MCA) flow. An MRI brain demonstrated right-sided holohemispheric fluid-attenuatedinversion recovery (FLAIR) hyperintensity with right insula contrast enhancement. She was found to have elevated anti-thyroid peroxidase (TPO) antibodies with an otherwise negative encephalitis workup. The patient was diagnosed with HE and acutely progressed to have focal seizures during a prolonged intensive care unit stay. She ultimately required intravenous Ig and antiepileptic medications to gain control of her disease. This case appears to be the first described presentation of hemiencephalitis with local hyperaemia, and may represent local autoregulatory loss as a result of vasculitis. This supports the existing literature implicating inflammatory microvascular infiltration in the mechanism of the disease. HE must be considered in a broad range of unexplained neurological symptoms.

Prospective observational study of early respiratory management in preterm neonates less than 35 weeks of gestation.

BACKGROUND: Current guidelines for management of respiratory distress syndrome (RDS) recommend continuous positive airway pressure (CPAP) as the primary mode of respiratory support even in the most premature neonates, reserving endotracheal intubation (ETI) for rescue surfactant or respiratory failure. The incidence and timing of ETI in practice is poorly documented. METHODS: In 27 Level III NICUs in the US (n = 19), Canada (n = 3) and Poland (n = 5), demographics and baseline characteristics, respiratory support modalities including timing of ETI, administration of surfactant and caffeine/other methylxanthines, and neonatal morbidities were prospectively recorded in consecutive preterm neonates following written parental consent. Infants were divided into three groups according to gestational age (GA) at birth, namely 26-28, 29-32 and 33-34 weeks. Statistical comparisons between groups were done using Chi-Square tests. RESULTS: Of 2093 neonates (US = 1507, 254 Canada, 332 Poland), 378 (18%) were 26-28 weeks gestational age (GA), 835 (40%) were 29-32 weeks, and 880 (42%) were 33-34 weeks. Antenatal steroid use was 81% overall, and approximately 89% in neonates ≤32 weeks. RDS incidence and use of ventilatory or supplemental oxygen support were similar across all sites. CPAP was initiated in 43% of all infants, being highest in the 29-32-week group, with a lower proportion in other GA categories (p < 0.001). The overall rate of ETI was 74% for neonates 26-28 weeks (42% within 15 min of birth, 49% within 60 min, and 57% within 3 h), 33% for 29-32 weeks (13 16 and 21%, respectively), and 16% for 33-34 weeks (5, 6 and 8%, respectively). Overall intubation rates and timing were similar between countries in all GAs. Rates within each country varied widely, however. Across US sites, overall ETI rates in 26-28-week neonates were 30-60%, and ETI within 15 min varied from 0 to 83%. Similar within 15-min variability was seen at Polish sites (22-67%) in this GA, and within all countries for 29-32 and 33-34-week neonates. CONCLUSION: Despite published guidelines for management of RDS, rate and timing of ETI varies widely, apparently unrelated to severity of illness. The impact of this variability on outcome is unknown but provides opportunities for further approaches which can avoid the need for ETI.

Pleistocene diversification in an ancient lineage: a role for glacial cycles in the evolutionary history of Dioon Lindl. (Zamiaceae).

PREMISE OF THE STUDY: Recent estimates of crown ages for cycad genera (Late Miocene) challenge us to consider what processes have produced the extant diversity of this ancient group in such relatively little time. Pleistocene climate change has driven major shifts in species distributions in Mexico and may have led to speciation in the genus Dioon by forcing populations to migrate up in elevation, thereby becoming separated by topography. METHODS: We inferred orthologs from transcriptomes of five species and sequenced these in 42 individuals representing all Dioon species. From these data and published plastid sequences, we inferred dated species trees and lineage-specific diversification rates. KEY RESULTS: Analyses of 84 newly sequenced nuclear orthologs and published plastid data confirm four major clades within Dioon, all of Pleistocene age. Gene tree analysis, divergence dates, and an increase in diversification rate support very recent and rapid divergence of extant taxa. CONCLUSIONS: This study confirms the Pleistocene age of Dioon species and implicates Pleistocene climate change and established topography in lineage spitting. These results add to our understanding of the cycads as evolutionarily dynamic lineages, not relicts or evolutionary dead ends. We also find that well-supported secondary calibration points can be reliable in the absence of fossils. Our hypothesis of lineage splitting mediated by habitat shifts may be applicable to other taxa that are restricted to elevation specific ecotones.

Aerosolized KL4 surfactant improves short-term survival and gas exchange in spontaneously breathing newborn pigs with hydrochloric acid-induced acute lung injury.

BACKGROUND: Surfactant therapy may be beneficial in acute lung injury (ALI). In spontaneously breathing newborn pigs with ALI supported with continuous positive airway pressure (CPAP), we evaluated the hypothesis that aerosolized KL4 surfactant (AERO KL4 S) would provide a similar therapeutic effect as intratracheal KL4 surfactant (ETT KL4 S) when compared to controls. METHODS: We randomized pigs with HCl-induced ALI to: (1) 175 mg/kg KL4 surfactant via endotracheal tube (ETT); (2) AERO KL4 S (22.5 mg/min phospholipid) for 60 min via continuous positive airway pressure (CPAP); or (3) sham procedure on CPAP. We obtained physiologic data and arterial blood gases throughout the 3-hr study. At study end, lungs were excised for analysis of interleukin-8 (IL-8), myeloperoxidase (MPO) levels and histomorphometric data. RESULTS: Pigs treated with ETT KL4 S and AERO KL4 S had improved survival and sustained pO2 compared to controls. The AERO KL4 S group had higher pH compared to controls. Lung IL-8 levels were lower in the AERO KL4 S group compared to controls. Histomorphometric analysis showed less hemorrhage in the ETT and AERO KL4 S groups compared to controls. The AERO KL4 S group had more open lung units per fixed-field than the ETT KL4 S or controls. CONCLUSIONS: AERO KL4 S produced similar improvements in survival, physiology, inflammatory markers, and morphology as ETT KL4 S in an ALI model.

Aerosolized albuterol sulfate delivery under neonatal ventilatory conditions: in vitro evaluation of a novel ventilator circuit patient interface connector.

BACKGROUND: Aerosolized medications that have been used in infants receiving ventilatory support have not been shown to be effective clinically among the smallest patients. The aim of this study was to characterize the delivery of aerosolized albuterol sulfate in vitro under simulated neonatal ventilatory conditions using a novel ventilator circuit/patient interface connector. METHODS: A Babylog(®) ventilator (VN500(®); Draeger), a novel ventilator circuit/patient interface (VC) connector (Afectair(®); Discovery Laboratories, Inc.), a TwinStar(®) HME (Draeger) low-volume filter, and either a test lung (Draeger) or lung simulator ASL 5000(®) (IngmarMed) were used. Intermittent mandatory ventilation conditions were set to replicate the most typical ventilation conditions for premature infants. Continuous positive airway pressure was also used to measure aerosol delivery with active respiratory drive from the patient. Albuterol sulfate (0.5 mg/mL) was loaded into the drug reservoir of a Misty Finity(®) nebulizer (Airlife(®); Cardinal Health) and connected to the ventilator circuit either via a "T" connector as described by the manufacturer [standard of care (SoC)] or via the VC connector. Albuterol extracted from the filters was analyzed using qualified high-performance liquid chromatography. In addition, a laser diffraction spectrometry (Spraytec(®); Malvern) and white-light spectrometry (Welas model 2100; Palas GmbH) were used to determine particle size distribution (PSD). RESULTS: Compared with SoC, the amount of albuterol delivered using the VC connector was significantly greater (p<0.001) under simulated neonatal ventilatory conditions. Additionally, the PSD profile of albuterol sulfate delivered using the VC connector was more representative of the PSD profile directly from the nebulizer. CONCLUSIONS: The use of the VC connector increased the delivery of albuterol sulfate and resulted in a PSD profile at the patient interface that is more consistent with the PSD profile of the selected nebulizer when compared with SoC. This VC connector may be a useful, new approach for the delivery of aerosolized medications to neonates requiring positive pressure ventilatory support.

Differences in response initiation and behavioral flexibility between adolescent and adult rats.

Adolescence is a period of increased vulnerability to psychiatric illnesses such as addiction, mood disorders, and schizophrenia. Rats provide a useful animal model for investigating the differences in behavior and biology between adults and adolescents that stem from ongoing brain development. We developed the Cued Response Inhibition Task, or CRIT, to assess response inhibition and initiation processes by measuring the ability of rodents to withhold a response during an inhibitory cue and then to respond promptly after cue termination. We found no difference between adult and adolescent rats in the ability to appropriately inhibit a response during cue presentation. Adolescents, however, were unable to initiate a response as quickly as adults after cue termination. Further, we observed that this difference in responding was abolished after adolescent rats aged to adulthood with no additional training. In a separate experiment, adult and adolescent rats were trained in CRIT and then trained in another protocol in which the response inhibitory cue from CRIT was used as a Pavlovian cue predictive of reward. Adolescents demonstrated more reward-seeking behavior during the previously inhibitory Pavlovian cue than adults, indicative of greater behavioral flexibility. Taken together, these data suggest that, compared with adults, adolescent rats (a) are less able to initiate a response after response inhibition, (b) equally inhibit behavioral responses, and (c) are more adept at flexibly switching behavioral patterns. Furthermore, this study characterizes a task that is well suited for future pharmacological and electrophysiological investigations for assessing neuronal processing differences between adolescents and adults.

Lucinactant attenuates pulmonary inflammatory response, preserves lung structure, and improves physiologic outcomes in a preterm lamb model of RDS.

BACKGROUND: Acute inflammatory responses to supplemental oxygen and mechanical ventilation have been implicated in the pathophysiological sequelae of respiratory distress syndrome (RDS). Although surfactant replacement therapy (SRT) has contributed to lung stability, the effect on lung inflammation is inconclusive. Lucinactant contains sinapultide (KL4), a novel synthetic peptide that functionally mimics surfactant protein B, a protein with anti-inflammatory properties. We tested the hypothesis that lucinactant may modulate lung inflammatory response to mechanical ventilation in the management of RDS and may confer greater protection than animal-derived surfactants. METHODS: Preterm lambs (126.8 ± 0.2 SD d gestation) were randomized to receive lucinactant, poractant alfa, beractant, or no surfactant and studied for 4 h. Gas exchange and pulmonary function were assessed serially. Lung inflammation biomarkers and lung histology were assessed at termination. RESULTS: SRT improved lung compliance relative to no SRT without significant difference between SRT groups. Lucinactant attenuated lung and systemic inflammatory response, supported oxygenation at lower ventilatory requirements, and preserved lung structural integrity to a greater degree than either no SRT or SRT with poractant alfa or beractant. CONCLUSION: These data suggest that early intervention with lucinactant may more effectively mitigate pulmonary pathophysiological sequelae of RDS than the animal-derived surfactants poractant alfa or beractant.

Comparison of poractant alfa and lyophilized lucinactant in a preterm lamb model of acute respiratory distress.

INTRODUCTION: A lyophilized formulation of lucinactant has been developed to simplify preparation and dosing. Endotracheal administration of surfactant can be associated with potentially harmful transient hemodynamic changes including decreases in cerebral blood flow and delivery of O2 to the brain. Efficacy and peri-dosing effects of poractant alfa and a lyophilized form of lucinactant were compared in this study. METHODS: Premature lambs (126-129 d gestation) were delivered by c-section, tracheostomized, ventilated, and instrumented with cerebral laser Doppler flowmetry and tissue PO2 probes. Pulmonary compliance and tidal volumes were monitored continuously and surfactant lung distribution was assessed. Lambs received either poractant alfa or lyophilized lucinactant and were monitored for 3 h after treatment. RESULTS: Both groups showed significant improvements in arterial pCO2, pH, pulmonary compliance, and tidal volume (all P < 0.01), a similar intra-pulmonary distribution profile, and no significant changes in arterial blood pressure or cerebral blood flow. Administration of poractant alfa was associated with higher mean airway pressures from 75 min post-dosing and transiently decreased heart rate and increased brain tissue PO2 during the first 30 min after treatment. DISCUSSION: In this newborn lamb model of respiratory distress, lyophilized lucinactant results in improved lung function as compared with poractant alfa.

Pulmonary distribution of lucinactant and poractant alfa and their peridosing hemodynamic effects in a preterm lamb model of respiratory distress syndrome.

Tracheal instillation of surfactant to premature newborns improves their survivability but may transiently obstruct airways resulting in undesirable acute effects on cerebral blood flow (CBF) and oxygenation. The acute peridosing hemodynamic effects of surfactant administration may be avoided by minimizing the volume of surfactant administered, but smaller surfactant volumes may also result in less even distribution of surfactant throughout the lung. These experiments were undertaken to compare responses to two surfactants with different dose volumes (porcine-derived poractant alfa, 2.5 mL/kg vs peptide-based synthetic lucinactant, 5.8 mL/kg) given to newly delivered lambs at 85% gestation. Both surfactants resulted in similar improvements in blood gas values, a doubling of dynamic compliance, increases in brain tissue oxygen tension, and stable blood pressure with no significant change in CBF. Distribution of surfactant throughout the lungs was more uniform with lucinactant than poractant alfa when assessed by labeled microspheres. We conclude that improvements in lung mechanics, gas exchange, and changes in CBF are comparable for a porcine-derived and peptide-containing synthetic surfactant, despite instilled volumes differing by 2-fold. Intrapulmonary distribution of surfactant is more uniform after a larger volume is instilled.