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Point-of-care laboratory testing (POCT) is associated with a reduced time to testing results and critical decision making within emergency departments. POCT is an essential clinical assessment tool because laboratory data are used to support timely critical decisions regarding acute medical conditions onditions ; however, there is currently limited research to support the use of POCT in the critical care transport environment. Few studies have evaluated the changes in patient care that occur after POCT during critical care transport. This study aims to contribute to the limited data available correlating prehospital POCT and changes in patient care.After institutional review board approval, a retrospective review of patients transported by a critical care transport team between October 1, 2013 and September 31, 2015 was completed. During the study period, 11,454 patients were transported, and 632 (5.51%) received POCT testing.Patient care changes were noted in 244 (38.6%) patient tests. The most frequent patient care alterations were ventilator settings (10.9%), electrolyte changes (10.4%), and unit bed upgrades (7.1%). POCT most frequently altered care for patients with post-cardiac arrest syndrome (64.7%), sepsis/septic shock (61.8%), diabetic ketoacidosis (54.5%), or pneumonia (49.3%).Patient care alterations occurred in 38.6% of patients undergoing POCT. Patient care was most frequently changed when patients were diagnosed with post-arrest, sepsis/septic shock, diabetic ketoacidosis, and pneumonia.

Myofascial release techniques at the time of complex hernia repair allow for tension-free closure of the midline fascia. Two common techniques are the open external oblique release (EOR) and the transversus abdominis release (TAR). Each technique has its reported advantages and disadvantages, but there have been few comparative studies. The purpose of this project was to compare the outcomes of these two myofascial release techniques. The Americas Hernia Society Quality Collaborative (AHSQC) database was queried and produced a data set on 24 May 2018. All patients undergoing open incision hernia repair with an open EOR or TAR were evaluated, and outcomes were compared including hernia recurrence, quality of life, and 30-day wound-related complications. 3610 patients met the inclusion criteria of undergoing open incisional hernia repair (501 undergoing EOR and 3109 undergoing TAR). Seventy surgeons from 50 institutions contributed EOR patients, and 124 surgeons from 89 institutions contributed TAR patients with no differences between the two groups in surgeons’ affiliation. Comparing open EOR and TAR showed no significant differences in hernia recurrence, quality of life, or 30-day surgical site infection rate. EOR had a significantly higher rate of surgical site occurrences compared with TAR (p

Many meshes are available for use in laparoscopic inguinal hernia repair. The surgeon must consider several factors when choosing a mesh for hernia repair including clinical outcomes, cost, and ease of use. The purpose of this study was to compare two different lightweight polypropylene meshes for laparoscopic and robotic inguinal hernia repairs. Subjects were randomized immediately before surgery. Data were reported in N (%) and median [Q1–Q3], comparisons of mesh insertion time were tested using a 2 × 2 ANOVA on the ranked times, comparisons between categorical variables were tested with Fisher’s Exact, and all data were analyzed using SAS® 9.4 (SAS Institute, Inc.). Between January 2015 and June 2016, 50 subjects were enrolled; two were excluded. Of 48 eligible subjects, most were Caucasian (N = 42, 88%), male (N = 37, 77%), with a median age of 63, and were randomized evenly between 3DMax™ mesh and Ultrapro® mesh. Robotic mesh placement significantly increased insertion time regardless of mesh type (p

A lack of research has become a barrier to the common use of prehospital antibiotics. The objective of this study is to further the limited research of prehospital antibiotics through evaluating the clinical impact, safety, and reliability of prehospital cefazolin administration in trauma patients.We completed a retrospective evaluation of adult trauma patients who were transported by a single air and ground critical care transport program between January 1, 2014, and June 30 2017. Two hundred eighty-two patients received prehospital cefazolin for deep wounds or open fractures before their arrival at a single level 2 trauma center during the study period. Patient demographics, mechanism of injury, injury type, infection rate, and identification of allergic reactions to cefazolin were also collected.Of 278 patients in the final analysis, 35.3% (n = 98) were diagnosed with an open fracture and 58.6% (n = 163) had a deep tissue injury. Eighty-two percent of prehospital open fracture diagnoses were confirmed in the emergency department. The overall infection rate was 6%; 31.3% of patients received a second dose of cefazolin in the emergency department during the study period. No patients receiving prehospital cefazolin had allergic or anaphylactic reactions. The overadministration rate was 5% (n = 14).Prehospital providers reliably identified open fractures, and prehospital cefazolin administration was not associated with anaphylactic reactions. This study population's infection rate of open fractures caused by traumatic injury was found to be 6%, and there was a low inappropriate administration rate.

Objective Rapid sequence intubation (RSI) is often required in managing critically ill patients in the prehospital setting. Although etomidate is a commonly used induction agent for RSI, ketamine has gained new interest in prehospital management with reported neutral hemodynamic effects. Limited data exist to support ketamine as an alternative to etomidate, particularly in the prehospital setting. The purpose of this study was to evaluate hemodynamic changes after the administration of ketamine versus etomidate in prehospital RSI. Methods This retrospective study evaluated adult patients undergoing prehospital RSI over 13 months within a regional emergency transport medicine service. Hypotension was defined as a 20% decrease in systolic blood pressure (SBP) within 15 minutes of receiving ketamine or etomidate. Hemodynamic data were collected 15 minutes before and 15 minutes after administration or until additional sedative medications were given. Data were analyzed using SPSS software (Version 21; IBM Corp, Armonk, NY), with P Results One hundred thirteen patients met the inclusion criteria (ketamine, n = 33; etomidate, n = 80), with the primary reasons for intubation being respiratory failure and trauma. There was no difference between the incidence of patients who experienced a 20% decrease in SBP (16% etomidate vs. 18% ketamine, P = .79). There were no significant differences in SBP pre- to postadministration between ketamine and etomidate. Conclusion No hemodynamic differences occurred between patients who received ketamine versus etomidate for prehospital RSI. Neither drug was associated with an increased need for additional sedatives, and neither drug was associated with an increased first-pass intubation success rate. Larger, prospective, powered studies are required to identify patients who may benefit from either ketamine or etomidate.

Background Surgical strategies are being adapted to face the COVID‐19 pandemic. Recommendations on the management of acute appendicitis have been based on expert opinion, but very little evidence is available. This study addressed that dearth with a snapshot of worldwide approaches to appendicitis. Methods The Association of Italian Surgeons in Europe designed an online survey to assess the current attitude of surgeons globally regarding the management of patients with acute appendicitis during the pandemic. Questions were divided into baseline information, hospital organization and screening, personal protective equipment, management and surgical approach, and patient presentation before versus during the pandemic. Results Of 744 answers, 709 (from 66 countries) were complete and were included in the analysis. Most hospitals were treating both patients with and those without COVID. There was variation in screening indications and modality used, with chest X‐ray plus molecular testing (PCR) being the commonest (19·8 per cent). Conservative management of complicated and uncomplicated appendicitis was used by 6·6 and 2·4 per cent respectively before, but 23·7 and 5·3 per cent, during the pandemic (both P, The COVID‐19 pandemic required reorganization of surgical services, affecting patients with common surgical diseases including acute appendicitis. No evidence is available on the topic. This study found global variation in screening policies, use of personal protective equipment and intraoperative directives. There has been increased adoption of non‐operative management and open appendicectomy. Hands off

Tension is one of the most discussed terms related to hernia surgery and repair. Despite the universally accepted opinion that tension and reduction of tension are important concepts in hernia repair, there is very little known about the physiologic tension of the abdominal wall related to ventral hernia repair. The purpose of this project was to attempt to measure physiologic tension in patients without hernia repair and help determine a normal baseline tension. Patients were enrolled in a prospective institutional review board–approved protocol to measure abdominal wall tension from February 2014 to present. Patients undergoing abdominal surgery without hernia repair were included. Demographic information and operative details were documented. Abdominal wall tensions were measured using scales attached to Kocher clamps that are clamped to the fascia and then brought together in the midline. Total tension, surgeon's estimation of tension, and grading of the fascia were recorded. Descriptive statistics were calculated. Eleven patients met the inclusion criteria and had tension measurements performed during surgery. The average age was 58 years, with 55 per cent of them being white and 82 per cent being male, with an average BMI of 27. Operations included exploratory laparotomy for small bowel pathology in six patients, colorectal surgery in three patients, and splenectomy in a trauma patient. Average tension measurements for these patients were 1.9 lbs. Surgeon grading of tension was an average of 2.2 (range, 1–5). Obtaining tension measurements is feasible during abdominal surgery. Physiologic tension seems to be approximately 2 pounds. Further study is needed with a larger sample of patients.

Background Donated platelets are stored at 22°C and discarded within 5 days because of diminished function and risk of bacterial contamination. Decline of platelet function has been attributed to decreased mitochondrial function and increased oxidative stress. Resveratrol (Res) and cytochrome c (Cyt c), in combination with hypothermic storage, may extend platelet viability. Methods Platelets from 20 donors were pooled into four independent sets and stored at 22°C or 4°C in the absence or presence of Res (50 μM) or Cyt c (100 μM) for up to 10 days. Sequential measurement of platelet counts, coagulation function (thromboelastography), oxygen consumption, lipid peroxidation, glucose-lactate levels, pH, TCO2, and soluble platelet activation markers (CD62P/PF-4) was performed. Results Platelet function diminished rapidly over time at 22°C versus 4°C (adenosine diphosphate, day 10 [0.6 ± 0.5] vs. [7.8 ± 3.5], arachidonic acid: day 10 [0.5 ± 0.5] vs. [30.1 ± 27.72]). At 4°C, storage treatment with Res or Cyt c limited deterioration in platelet function up to day 10, an effect not observed at 22°C (day 10, 4°C, Con [7.8 ± 3.5] vs. Res [37.3 ± 24.19] vs. Cyt c [45.83 ± 43.06]). Mechanistic analysis revealed oxygen consumption increased in response to Cyt c at 22°C, whereas neither Cyt c or Res affected oxygen consumption at 4°C. Lipid peroxidation was only reduced at 22°C (day 7 and day 10), but remained unchanged at 4°C, or when Res or Cyt c was added. Cytosolic ROS was significantly reduced by pretreatment with Res at 4°C. Total platelet count and soluble activation markers were unchanged during storage and not affected by Res, Cyt c, or temperature. Glucose concentration, pH and TCO2 decreased while lactate levels increased during storage at 22°C but not 4°C. Conclusion Platelet function is preserved by cold storage for up to 10 days. This function is enhanced by treatment with Res or Cyt c, which supports mitochondrial activity, thus potentially extending platelet shelf life.

Many meshes are available for use in laparoscopic inguinal hernia repair. The surgeon must consider several factors when choosing a mesh for hernia repair including clinical outcomes, cost, and ease of use. The purpose of this study was to compare two different lightweight polypropylene meshes for laparoscopic and robotic inguinal hernia repairs.Subjects were randomized immediately before surgery. Data were reported in N (%) and median [Q1-Q3], comparisons of mesh insertion time were tested using a 2 × 2 ANOVA on the ranked times, comparisons between categorical variables were tested with Fisher's Exact, and all data were analyzed using SAS® 9.4 (SAS Institute, Inc.).Between January 2015 and June 2016, 50 subjects were enrolled; two were excluded. Of 48 eligible subjects, most were Caucasian (N = 42, 88%), male (N = 37, 77%), with a median age of 63, and were randomized evenly between 3DMax™ mesh and Ultrapro® mesh. Robotic mesh placement significantly increased insertion time regardless of mesh type (p .0001). When comparing NASA-TLX self-assessment surveys, there was no significant difference between the meshes in difficulty of placement. The type of mesh did not significantly impact the insertion time regardless of robot use (p = 0.523).Our data demonstrate that mesh insertion times comparing two different lightweight polypropylene meshes were not significantly different. Increased insertion times associated with robotic repair are likely due to the mechanics of robotic suturing and associated learning curve. Our data suggest that these meshes can be used interchangeably based on the surgeon's preference.NCT01825187.

Tension is one of the most discussed terms related to hernia surgery and repair. Despite the universally accepted opinion that tension and reduction of tension are important concepts in hernia repair, there is very little known about the physiologic tension of the abdominal wall related to ventral hernia repair. The purpose of this project was to attempt to measure physiologic tension in patients without hernia repair and help determine a normal baseline tension. Patients were enrolled in a prospective institutional review board-approved protocol to measure abdominal wall tension from February 2014 to present. Patients undergoing abdominal surgery without hernia repair were included. Demographic information and operative details were documented. Abdominal wall tensions were measured using scales attached to Kocher clamps that are clamped to the fascia and then brought together in the midline. Total tension, surgeon's estimation of tension, and grading of the fascia were recorded. Descriptive statistics were calculated. Eleven patients met the inclusion criteria and had tension measurements performed during surgery. The average age was 58 years, with 55 per cent of them being white and 82 per cent being male, with an average BMI of 27. Operations included exploratory laparotomy for small bowel pathology in six patients, colorectal surgery in three patients, and splenectomy in a trauma patient. Average tension measurements for these patients were 1.9 lbs. Surgeon grading of tension was an average of 2.2 (range, 1-5). Obtaining tension measurements is feasible during abdominal surgery. Physiologic tension seems to be approximately 2 pounds. Further study is needed with a larger sample of patients.

A common technique for ventral and incisional hernia repair is the retrorectus repair (Rives-Stoppa). The posterior rectus sheath is incised bilaterally, and mesh is placed retromuscularly. There is little information on how this component separation technique affects abdominal wall tension. We evaluated abdominal wall tension in patients undergoing retrorectus repair of abdominal wall hernias. Patients undergoing retrorectus repair of their ventral hernias were enrolled in a prospective, Institutional Review Board-approved protocol to measure abdominal wall tension from 8/1/2013 to 8/2/2017. Demographic information and operative details were documented. Abdominal wall tensions were measured using scales attached to Kocher clamps that were clamped to the fascia and brought together in the midline. Measurements were made before and after incising the posterior rectus sheaths. Data were analyzed with a repeated measures analysis of variance (ANOVA), and differences between individual groups were analyzed by least square differences. Forty-five patients had tension measurements. Average age was 58 years (range 29-81)-78% Caucasian, 51% female, an average body mass index (BMI) of 35 kg/m2 (range 20-62), and 38% recurrent hernias. The average hernia defect was 121.9 cm2, and the average mesh size was 607.8 cm2. There was a significant reduction in tension after bilateral posterior rectus sheath incision (3.1 lbs vs. 5.6 lbs, p0.0001). In this evaluation, abdominal wall tension measurements are shown to be a feasible adjunct during open hernia repair with retrorectus repair. Transection of the posterior rectus sheath decreases tension during hernia repair and may help guide surgeons regarding when to use this procedure.

Obesity increases the incidence of mortality in trauma patients. Current Advanced Trauma Life Support guidelines recommend using a 5-cm catheter at the second intercostal (ICS) space in the mid-clavicular line to treat tension pneumothoraces. Our study purpose was to determine whether body mass index (BMI) predicted the catheter length needed for needle thoracostomy.We retrospectively reviewed trauma patients undergoing chest computed tomography scans January 2004 through September 2006. A BMI was calculated for each patient, and the chest wall thickness (CWT) at the second ICS in the mid-clavicular line was measured bilaterally. Patients were grouped by BMI as underweight (≤ 18.5 kg/m2), normal weight (18.6-24.9 kg/m(2)), overweight (25-29.9 kg/m(2)), or obese (≥ 30 kg/m(2)).Three hundred twenty-six patients were included in the study; 70% were male. Ninety-four percent of patients experienced blunt trauma. Sixty-three percent of patients were involved in a motor vehicle collision. The average BMI was 29 [SD 7.8]. The average CWT was 6.2 [SD 1.9]cm on the right and 6.3 [SD 1.9]cm on the left. As BMI increased, a statistically significant (p0.0001) CWT increase was observed in all BMI groups. There were no significant differences in ISS, ventilator days, ICU length of stay, or overall length of stay among the groups.As BMI increases, there is a direct correlation to increasing CWT. This information could be used to quickly select an appropriate needle length for needle thoracostomy. The average patient in our study would require a catheter length of 6-6.5 cm to successfully decompress a tension pneumothorax. There are not enough regionally available data to define the needle lengths needed for needle thoracostomy. Further study is required to assess the feasibility and safety of using varying catheter lengths.

Management of the open abdomen has been recorded since the 1900s. Trauma, abdominal sepsis, the need for re-exploration, the need for ongoing resuscitation, and control of abdominal compartment syndrome continue to be management dilemmas that require the general surgeon to have knowledge of managing patients with an open abdomen. As with all surgical procedures, complications are inherent to the management of the open abdomen and all measures should be taken to minimize morbidity. Future directions of management of the open abdomen should include distinguishing best practices of management of patient types (e.g., trauma, emergency general surgery, and abdominal compartment syndrome) and best practices for managing complications associated with the open abdomen such as hernia formation and entero-atmospheric fistula formation. The open abdomen is often life-saving, but should be implemented under appropriate circumstances to minimize complications in this challenging patient population.

As a control engineer (and proud of it!), I know that controlling through transition—the transient response—is the most difficult part of a control problem but also the part where you learn the most. So, I would like to reflect on the “lessons learned” during the transitions and uncertainties that have occurred during my career and hope they help some of you think about your future. My life breaks down nicely into roughly 20-year segments. My first 20 were dedicated to getting a driver’s license, getting out of high school, and getting into the University of Florida. The next 20 were dedicated to getting out of college, getting married, raising a family, and working in aerospace and academia. The next 20 were dedicated to enjoying my family, except when my children got their driver’s licenses, and working in the automotive industry, retiring when I turned 60. I am now 67 years old, so I am seven plus years into my next 20 year segment (I hope)! I am doing something different from the prior 60 years because I believe that age is a state of mind and that learning totally new subjects makes life exciting and youthful. An education in control systems allows one to tackle almost anything (isn’t life just a near-optimal nonlinear, stochastic control problem?!). My working engineering career started in 1960 when I became a co-op student at the Army Ballistic Missile Agency in Huntsville, Alabama; later in the year it became the NASA Marshall Space Flight Center. I was assigned to the group that was struggling with the problem of controlling rockets with a new technology: the digital computer. And that leads to the first lesson.

The American Association for the Surgery of Trauma developed an Organ Injury Scale for management of patients with splenic, kidney, or liver injuries. Despite widespread use of the guidelines, the person who determines the injury grade varies among institutions. Our purpose was to determine the accuracy and interobserver agreement between surgical residents and a radiologist in grading solid organ injuries. We retrospectively reviewed patients with solid organ injuries from January 2009 to May 2010 and compared the grade of solid organ injuries by a single resident with grades by a single blinded radiologist using a paired t test, analysis of variance, or Kruskal-Wallis. Computed tomography scans of 58 patients with splenic injuries, 43 with liver injuries, and 16 with kidney injuries were reviewed. Average grades for splenic injuries were 2.5 and 2.4 (radiologist/resident); liver injuries, 2.6 and 2.1; and kidney injuries, 2.7 and 2.8. There were no significant differences in grading by the radiologist and resident for splenic and kidney injuries; however, equal values were only achieved in 43 and 38 per cent, respectively. There was a significant difference (average rating difference 0.54, P = 0.0002) in grading between the radiologist and resident for liver injuries with only 35 per cent having equal values and the radiologist grading on average 0.5 points higher than the resident. No demographic, injury, or outcome variables were significantly associated with interobserver variability ( P > 0.05). Despite a significant difference for liver injury grading, interobserver agreement between residents and a single radiologist was low. Clinical implications and the impact on outcomes related to interobserver variations require further study.

In 1996, 52 million vehicles were produced worldwide. By 2005, many predict that over 65 million will be produced because of the strengthening economies throughout the world and the individual's desire for personal mobility. The automobiles of the 1990s are at least 10 times cleaner and twice as fuel efficient as the vehicles of the 1970s. These advancements were due in large part to distributed microprocessor-based control systems. Furthermore, the resultant vehicles are safer, more comfortable, and more maneuverable. The environmental challenges of the 21st century will require advances of the same order of magnitude. In particular, next generation vehicles will be more “electrified” and designed by total systems approaches, involving new materials, alternative fuels, and new powertrains — all enabled by modern control systems and design techniques.

Field measurements associated with the behavior of ten low-pressure grouted anchors installed with a hollow stem auger at the National Geotechnical Experimentation Site at Texas AM the shear strength of the soil-grout interface compared to engineering soil properties; the relationships between the ultimate load, the creep failure load, the creep threshold load, and the design load; the creep movement rate under load; and the load loss as a function of time. The results show that anchors with shorter tendon bond lengths have higher ultimate capacities and lower creep rates, and transfer the load further away from the supported structure.

We report the absolute and relative risks for neonatal and infant death, low and very low birth weight, and delivery at33 and35 weeks' gestation in twin pregnancy stratified by maternal race and age, as well as gender pair combinations of the twins.Data on 324,141 twin infants were obtained from the 1985 to 1988 U.S. Linked Birth/ Infant, Death Data Sets. In this observational cohort study, we analyzed the outcomes of 138,779 twin pregnancies of white and black women that ended with the delivery of two live-born infants.Rates for the aforementioned outcomes are increased for black infants, for male-male pairs compared with male-female pairs (with female-female pairs being intermediate), and for young mothers. For male-male twins born to young (or = 22 years old) black women, relative risks range from 2.1 for both pair members being low birth weight (2500 gm) to 5.0 for both pair members dying in infancy, when male-female pairs born to older (or = 28 years) white women served as the reference group.Although all twin pregnancies are at higher risk than singletons, risk is influenced by maternal race and age, as well as gender pair combination. These analyses provide useful information for counseling women pregnant with twins. Furthermore, they suggest that failure to consider variations in baseline risk may have seriously flawed studies evaluating prophylactic interventions in twin pregnancy.

Background: Guidelines for optimal endoscopic training for surgical residents have not been formally integrated into modern teaching programs. Our purpose was to apply two endoscopic evaluation tools (EE-1 and EE-2) designed to measure surgical resident competency in the performance of esophagogastroduodenoscopy (EGD). Methods: Prospectively collected data were reviewed from consecutive EGDs in a single institution by a single attending surgeon over 3 years (July 2008 to July 2011). Demographic, procedural, and outcome data were collected. Residents were graded at the completion of each procedure by the attending surgeon using EE-1 and EE-2. Descriptive statistics were calculated, and comparisons based on PGY levels were made using Fisher’s exact and Kruskal-Wallis tests . P < 0.05 was considered significant. Results: All procedures (N = 50) were performed by residents under the direct attending surgeon supervision. Average patient age was 51 years (range, 31-79 years), 66% were women, and 66% were Caucasian. PGY-3 residents performed 62% of the procedures. Average resident participation was 84% of each procedure. Biopsies were performed in 80% of patients and dilatations in 16%. All EGDs were successfully completed (average time, 13.1 min). EE-1 results demonstrated significantly different grades (P < 0.05) among PGY levels in seven of eight variables. EE-2 grades were significantly different (P < 0.05) among PGY levels in all 10 variables with a general trend of improvement as PGY level increased. There were no mortalities or morbidities. Conclusions: Residents can perform EGDs safely and expeditiously with appropriate supervision. Methods to assess competency continue to evolve and should remain an area of active research. doi: http://dx.doi.org/10.4021/gr520w

The American Association for the Surgery of Trauma developed an Organ Injury Scale for management of patients with splenic, kidney, or liver injuries. Despite widespread use of the guidelines, the person who determines the injury grade varies among institutions. Our purpose was to determine the accuracy and interobserver agreement between surgical residents and a radiologist in grading solid organ injuries. We retrospectively reviewed patients with solid organ injuries from January 2009 to May 2010 and compared the grade of solid organ injuries by a single resident with grades by a single blinded radiologist using a paired t test, analysis of variance, or Kruskal-Wallis. Computed tomography scans of 58 patients with splenic injuries, 43 with liver injuries, and 16 with kidney injuries were reviewed. Average grades for splenic injuries were 2.5 and 2.4 (radiologist/resident); liver injuries, 2.6 and 2.1; and kidney injuries, 2.7 and 2.8. There were no significant differences in grading by the radiologist and resident for splenic and kidney injuries; however, equal values were only achieved in 43 and 38 per cent, respectively. There was a significant difference (average rating difference 0.54, P = 0.0002) in grading between the radiologist and resident for liver injuries with only 35 per cent having equal values and the radiologist grading on average 0.5 points higher than the resident. No demographic, injury, or outcome variables were significantly associated with interobserver variability (P0.05). Despite a significant difference for liver injury grading, interobserver agreement between residents and a single radiologist was low. Clinical implications and the impact on outcomes related to interobserver variations require further study.

Study objective: To measure the association between the development of air leak (pneumothorax or pulmonary interstitial emphysema) during the first 27 postnatal days and neonatal death or chronic lung disease, as determined on day 28, among very low birth weight infants who required mechanical ventilation from the first day of life. Design: Prospective, multicenter cohort study. Patients: Two hundred sixty inborn, very low birth weight (501 to 1500 gm) infants given ventilatory support from the first day of life. Results: The risk of an adverse outcome (death or chronic lung disease)changed with postnatal age at the time of diagnosis of the air leak. The association between air leak and an adverse outcome, as measured by gestational age-adjusted odds ratio (95% confidence interval), was 13.9 (1.7 to 114.6) for those in whom an air leak developed on day 0 or 1 (early), decreased to 1.7 (0.7 to 4.1) for those whose air leak developed on day 2 or 3 (intermediate), and increased to 16.6 (2.1 to 130.4) for those whose air leak developed on days 4 to 27 (late). The association with neonatal death showed even more striking fluctuations with postnatal age at occurrence of an air leak, ranging from an odds ratio of 40.3 (3.5 to 464.8) for the early group to 7.5 (2.3 to 25.0) for the intermediate group and 78.3 (6.9 to 889.5) for the late group. Conclusions: Air leak in newborn infants requiring mechanical ventilation is associatedwith increased risks of death or future morbidity, but the magnitude of these risks changes with postnatal age at the time of diagnosis of the air leak. Failure to consider the age at which the air leak is detected may miss changes in its prognostic implications and may partly explain inconsistent results in previous studies.

To determine whether multiple doses of bovine surfactant would improve neonatal mortality in very premature neonates, we conducted two multicenter controlled trials under identical protocols; the results were combined for analysis. Four hundred and thirty neonates born between 23 and 29 weeks gestation and weighing 600 to 1250 g at birth were assigned randomly at birth to receive either 100 mg of phospholipids/kg of Survanta, a modified bovine surfactant (n = 210), or a sham air placebo (n = 220) within 15 minutes of birth. Neonates who developed respiratory distress syndrome and required mechanical ventilation with at least 30% oxygen could be given up to three more doses in the first 48 hours after birth. Dosing was performed by investigators not involved in the clinical care of the neonates; nursery staff were kept blinded as to the treatment assignment. Cause of death was determined by a panel of three independent, board-certified neonatologists after blindly reviewing case report forms and autopsy reports. Fewer Survanta-treated neonates died of any cause (11.4% vs 18.8%, P = .031), died of respiratory distress syndrome (1.9% vs 15.6%, P < .001), and either died or developed bronchopulmonary dysplasia due to respiratory distress syndrome (39.5% vs 49.1%, P = .044). The incidence of respiratory distress syndrome was also lower in Survanta-treated neonates (28.0% vs 56.9%, P < .001), and the Survanta-treated neonates' oxygenation and ventilatory status were improved significantly at 72 hours. Survanta-treated neonates were also at lowered risk of developing pulmonary interstitial emphysema (23.3% vs 36.9%, P = .002) and other forms of pulmonary air leaks (9.6% vs 20.8%, P .002). We conclude that multiple doses of Survanta reduce mortality and morbidity due to respiratory distress syndrome during the neonatal period.

Linked Birth/Infant Death Files available from the National Center for Health Statistics identify an infant as a twin, but do not identify twin pairs. An algorithm based on maternal, paternal, and infant characteristics has been used to identify twin pairs, but the validity of this algorithm has never been tested. The Missouri linked birth/infant death file from 1980 to 1990 identifies twin pairs by a sequence number. The authors tested the rate and accuracy with which the algorithm identified true pairs in the Missouri file and whether estimates of risk and possible risk factors calculated from pairs of twins identified by the algorithm agreed with these characteristics as calculated from known twin pairs. The algorithm identified 96% (8,273 of 8,620) of true pairs and one false pair. Despite incomplete pair identification, and even identification of a false pair, estimates from the subset identified by the algorithm generally agreed well with characteristics measured from all twin pairs. Nonetheless, incorporation of a multiple birth sequence number into Linked Birth/Infant Death Files would enhance their utility.

OBJECTIVES: Our objectives were twofold: (1) to report the relative risks and population-attributable risks of twins compared with singletons for several adverse pregnancy outcomes and (2) to describe the association between having been of low or very low birth weight and death in the neonatal, postneonatal, and infant periods for twins compared with singletons. STUDY DESIGN: We performed population-based analysis of all live births and infant deaths from 1985 to 1986 birth cohorts, as reported in the U.S. Linked Birth/Infant Death Data Sets. RESULTS: With singletons as the referent group, twins of all races had relative risks for very low birth weight, low birth weight, and neonatal, postneonatal, and infant death of 9.97, 8.61, 7.06, 2.75, and 5.43, respectively. Although twins make up only 2.09% of live births, the population-attributable risks of twins (the proportion of the population's adverse outcome associated with being a twin) for very low birth weight, low birth weight, and neonatal, postneonatal, and infant death was 15.8%, 13.7%, 11.2%, 3.4%, and 8.4%, respectively. CONCLUSIONS: These population-based data show that although twins are relatively infrequent they account for a disproportionately large share of adverse pregnancy outcomes. Given the relative ease with which twins can be identified early in the course of pregnancy, development and testing of interventions to postpone preterm delivery in twin pregnancy should become a national public health priority. (AM J OBSTET GYNECOL 1994;170:456-61.)

GENDER PAIR COMBINATION, AND MATERNAL AGE AND RACE MODERATE RISKS CONFRONTING TWINS. † 1637

A retargeting procedure is developed for use as a nonlinear low thrust guidance scheme. The selection of a control program composed of a sequence of inertially fixed thrust-acceleration vectors permits all trajectory computations to be made with closed form expressions, and allows the controls to be represented by constant parameters, thrust-acceleration vectors and thrusting times. By requiring each trajectory to be time optimal, the guidance problem is transformed into a parameter optimization problem which is solved by the conjugate gradient method. The scheme is applied to a low thrust capture mission, and the results of computer simulations are presented.

To minimize the selection bias inherent in reporting results gathered only in neonatal intensive care units, this study presents survival and respiratory course data on all 299 infants of birthweight 501 to 1500 gm liveborn to residents of the North Central Illinois Perinatal Region in 1985-1986. The survival rate was 86.8% (171 of 197) for infants between 1001 and 1500 gm, but only 35.3% (36 of 102) for infants weighing less than 1001 gm. In all, 207 infants (69.2%) survived. One hundred eighty-six infants (62.2%) required mechanical ventilation, and 122 (65.6%) ventilated infants survived. Seventy-five (40.3%) ventilated infants developed lung rupture and 54 (29%) developed chronic lung disease (CLD), as manifest by a supplemental oxygen requirement at 28 days of age. Lung rupture significantly predicted death in the first 7 days, the development of CLD, and fatal CLD. These data portray an accurate picture of the survival and ventilatory course of this group of babies because every member of the entire regional cohort is included.

The convergence properties of the gradient, conjugate gradient, and Davidon-Fletcher-Powell methods for the singular, finite-dimensional quadratic minimization problem are developed. It is shown that for all of the methods, except the gradient method, that the minimum is obtained in at most m iterates, where m is the dimension of the range of the Hessian matrix, as opposed to n >m iterates for nonsingular problems. A class of associated nonsingular quadratic problems is defined to show that the gradient method has slower convergence on singular problems than on corresponding nonsingular approximations to the singular problems while the conjugate direction methods have more rapid convergence. This implies that slow convergence attributed to singular problems is actually a property of the gradient method as opposed to the singularity of the problem.

One hundred twenty-two preterm infants were enrolled in a placebo-controlled, double-blind trial using intravenous indomethacin for the prevention of periventricular-intraventricular hemorrhage (PVH-IVH). Before random assignment, data on the infants were stratified according to low-weight (500 to 999 g) or high-weight (1000 to 1500 g) subgroups. Cranial sonography was used to document the absence of PVH-IVH before enrollment and the occurrence of PVH-IVH during the 7-day protocol. Indomethacin, 0.1 mg/kg, or placebo was administered before 12 hours of age and at 24, 48, and 72 hours of age. Five patients receiving indomethacin and six receiving placebo were withdrawn before completion of the study. In the remaining 111 patients, the indomethacin and placebo groups were comparable with respect to gestational ages, maternal complications, Apgar scores, ventilatory requirements, complications of prematurity, and mortality rate. PVH-IVH developed in six of 56 infants who received indomethacin and 11 of 55 infants who received placebo (P = 0.174). Analysis of the individual strata showed that the indomethacin-treated infants in the low-weight subgroup sustained a higher mortality rate (11/17 vs 3/16; P = 0.008) without a reduction in the incidence of PVH-IVH. Infants in the indomethacin-treated high-weight subgroup demonstrated a significantly lower incidence of PVH-IVH (2/39 vs 8/39; P = 0.04), but the frequency of high-grade hemorrhages was comparable for both indomethacin- and placebo-treated groups. In summary, the prophylactic administration of intravenous indomethacin for the prevention of PVH-IVH cannot be recommended for infants less than 1000 g. In preterm infants between 1000 and 1500 g birth weight, indomethacin significantly reduced the incidence of PVH-IVH.

Future space missions to the outer planets may depend upon the use of low-thrust propulsion systems. As these planets are decidedly oblate, the question of the effect of that oblateness on a low-thrust trajectory is of some interest. In this paper the problem of optimal energy increase is attacked under the assumption that the coefficients for the second zonal harmonic, i.e.,J 2, and the nondimensional thrust acceleration are the same order of magnitude. Using a two variable asymptotic expansion technique, a near optimal control program is generated and the first order uniformly valid approximation for the corresponding trajectory is obtained. Tangential thrust is shown to be a good near-optimal thrust program even in the presence of oblateness effects. The optimal control program is found to be oscillatory and quite similar to the optimal control for energy increase in an inverse square gravitational field.

A quadratic functional version of the linear quadratic optimal control problem is employed to develop insights into the computation and theory of singular optimal controls. It is shown that sufficiency, existence, and uniqueness conditions and convergence conditions for gradient-type algorithms require the same basic assumption, namely a positivity assumption on the second-variation operator and an inclusion requirement with regard to the range space of the second variation operator. The theory is interpreted for both the nonsingular and singular problems to show the inherent differences between the two problems. It is shown that the gradient, conjugate gradient, and Davidon-Fletcher-Powell (DFP) algorithms converge if the existence conditions for the optimal control are satisfied, and that the rate of convergence is superlinear for the DFP method applied to nonsingular problems. Operational aspects for improving the rate of convergence on singular problems are discussed along with an informative comparison of the behavior of gradient and accelerated gradient methods on singular problems.

Stimulated blood flow was measured in the legs of 28 infants who had undergone umbilical arterial catheterization in the neonatal period. Catheter tips were positioned in the region of the aortic bifurcation, and only an isotonic saline/dextrose solution was continuously pumped through the catheter. The catheters were in place for an average of 58.3 hours (range, 4 to 144), and the infants were studied between 29 and 135 days of age (mean, 67 days). Blood flow in both legs was measured simultaneously by venous occlusion plethysmography using a mercury-in-rubber strain gauge. Analysis of peak stimulated blood flow in each leg and simultaneous flow in the opposite leg showed no difference between flow in the leg whose iliac artery had been catheterized in the neonatal period and flow in the opposite leg (paired t-test = 0.17; P > .50). No chronic, subclinical flow deficiencies of umbilical arterial catheterization were demonstrable. We see no new reason to curtail the judicious use of the umbilical artery catheter.