Biomedical subjects

Mark P Johnson

Publications and source records attributed to Mark P Johnson.

At least 19 recordsLinked to original sources

PubMed2004

Acute cardiovascular effects of fetal surgery in the human.

BACKGROUND: Prenatal surgery for congenital anomalies can prevent fetal demise or alter the course of organ development, resulting in a more favorable condition at birth. The indications for fetal surgery continue to expand, yet little is known about the acute sequelae of fetal surgery on the human cardiovascular system. METHODS AND RESULTS: Echocardiography was used to evaluate the heart before, during, and early after fetal surgery for congenital anomalies, including repair of myelomeningocele (MMC, n=51), resection of intrathoracic masses (ITM, n=15), tracheal occlusion for congenital diaphragmatic hernia (CDH, n=13), and resection of sacrococcygeal teratoma (SCT, n=4). Fetuses with MMC all had normal cardiovascular systems entering into fetal surgery, whereas those with ITM, CDH, and SCT all exhibited secondary cardiovascular sequelae of the anomaly present. At fetal surgery, heart rate increased acutely, and combined cardiac output diminished at the time of fetal incision for all groups including those with MMC, which suggests diminished stroke volume. Ventricular dysfunction and valvular dysfunction were identified in all groups, as was acute constriction of the ductus arteriosus. Fetuses with ITM and SCT had the most significant changes at surgery. CONCLUSIONS: Acute cardiovascular changes take place during fetal surgery that are likely a consequence of the physiology of the anomaly and the general effects of surgical stress, tocolytic agents, and anesthesia. Echocardiographic monitoring during fetal surgery is an important adjunct in the management of these patients.

Adult↗

PubMed2004

North Atlantic right whales (Eubalaena glacialis) ignore ships but respond to alerting stimuli.

North Atlantic right whales were extensively hunted during the whaling era and have not recovered. One of the primary factors inhibiting their recovery is anthropogenic mortality caused by ship strikes. To assess risk factors involved in ship strikes, we used a multi-sensor acoustic recording tag to measure the responses of whales to passing ships and experimentally tested their responses to controlled sound exposures, which included recordings of ship noise, the social sounds of conspecifics and a signal designed to alert the whales. The whales reacted strongly to the alert signal, they reacted mildly to the social sounds of conspecifics, but they showed no such responses to the sounds of approaching vessels as well as actual vessels. Whales responded to the alert by swimming strongly to the surface, a response likely to increase rather than decrease the risk of collision.

Acoustics↗

PubMed2004

Prenatally diagnosed giant omphaloceles: short- and long-term outcomes.

OBJECTIVES: To review prenatal findings, short- and long-term outcomes of giant omphaloceles (GO) managed at a single institution (1996-2001). METHODS: Prenatal findings and early postnatal outcomes were retrospectively reviewed. Clinical short- and long-term outcomes were analyzed in eight and five children respectively. Parents and physicians of the children were surveyed by written questionnaires about the children's subsequent health issues. (IRB 2002-2-2683). RESULTS: Seventeen pregnancies with GO were identified: Eight fetuses were live born, four ended in (terminations), two died in utero and three were lost to follow-up. Live-born fetuses had prenatal ascites, extreme levocardia and were delivered by cesarean section at a mean of 37 weeks' gestation with a mean birth weight of 2903 g. All neonates required intubation. Two infants (2/8) died within one year. Four of the six survivors had respiratory insufficiency with a mean ventilation time of 76 days. Respiratory and feeding problems complicated the early neonatal course. Long-term follow-up was available for five patients (mean age of 33.2 months). Asthma, recurrent pulmonary infections, feeding problems, gastroesophageal reflux and failure to thrive were the major problems. CONCLUSIONS: Respiratory and feeding problems were the most common neonatal and long-term medical management issues. Parents need to be counseled prenatally about the probability of multiple surgeries and long hospitalization following birth.

Adolescent↗

PubMed2004

Sacrococcygeal teratoma: prenatal assessment, fetal intervention, and outcome.

PURPOSE: To understand the natural history and define indications for fetal intervention in sacrococcygeal teratoma (SCT), the authors reviewed all cases of fetal SCT presenting for evaluation. METHODS: Prenatal diagnostic studies including ultrasound scan, magnetic resonance imaging (MRI), echocardiography and pre- and postnatal outcomes were reviewed in 30 cases of SCT that presented between September 1995 and January 2003. RESULTS: The mean gestational age (GA) at presentation was 23.9 weeks (range, 19 to 38.5) with 3 sets of twins (10%). Overall outcomes included 4 terminations, 5 fetal demises, 7 neonatal deaths, and 14 survivors. Significant obstetric complications occurred in 81% of the 26 continuing pregnancies: polyhydramnios (n = 7), oligohydramnios (n = 4), preterm labor (n = 13), preeclampsia (n = 4), gestational diabetes (n = 1), HELLP syndrome (n = 1), and hyperemesis (n = 1). Fetal intervention included cyst aspiration (n = 6), amnioreduction (n = 3), amnioinfusion (n = 1), and open fetal surgical resection (n = 4). Indications for cyst aspiration and amnioreduction were maternal discomfort, preterm labor, and prevention of tumor rupture at delivery. Although 15 SCTs were solid causing risk for cardiac failure, only 4 fetuses met criteria for fetal debulking based on ultrasonographic and echocardiographic evidence of impending high output failure and favorable anatomy at 21, 23.6, 25, and 26 weeks' gestation. Intraoperative events included maternal blood transfusion (n = 1), fetal blood transfusion (n = 2), chorioamniotic membrane separation (n = 2), and fetal arrest requiring successful cardiopulmonary resuscitation (CPR) (n = 1). In the fetal resection group, 3 of 4 survived with mean GA at delivery of 29 weeks (range, 27.6 to 31.7 weeks), mean birth weight of 1.3 kg, hospital stay ranging from 16 to 34 weeks, and follow-up ranging from 20 months to 6 years. Postnatal complications in the fetal surgery group included neonatal death (n = 1, secondary to premature closure of ductus arteriosus with cardiac failure), embolic event (n = 1, resulting in unilateral renal agenesis, jejunal atresia), chronic lung disease (n = 1), and tumor recurrence (n = 1). CONCLUSIONS: For fetal SCT, the rapidity at which cardiac compromise can develop and the high incidence of obstetric complications warrant close prenatal surveillance. Amnioreduction, cyst aspiration, and surgical debulking are potentially life-saving interventions.

Adolescent↗

PubMed2004

Right congenital diaphragmatic hernia: Prenatal assessment and outcome.

PURPOSE: To understand the natural history of right congenital diaphragmatic hernia (CDH), the authors retrospectively reviewed 27 cases of right CDH that presented for prenatal evaluation or postnatal treatment. METHODS: Between 1995 and September 2002, a total of 194 cases of fetal CDH were evaluated and included 22 right-sided defects. The authors reviewed prenatal diagnostic studies (ultrasound scan, magnetic resonance imaging [MRI] echocardiography) and pre- and postnatal outcomes in these 22 cases of right CDH. Five additional cases of right CDH without a prenatal diagnosis were reviewed. RESULTS: The mean gestational age at evaluation was 26.1 weeks. The lung area to head circumference ratio (LHR) ranged from 0.32 to 2.5. In all cases, the fetal liver was herniated into the right chest. Associated anomalies were common. There were no karyotype abnormalities (17 of 22 tested). There were 4 terminations. Nine of the 18 (50%) continuing pregnancies had polyhydramnios, premature rupture of membranes, or preterm labor. The mean gestational age at birth was 36.8 weeks. One patient underwent tracheal occlusion at 27 weeks, and 2 patients died before postnatal repair. Overall survival rate (22 prenatal plus 5 postnatal diagnoses) was 19 of 27 (70%). Postnatal survival rate was 19 of 23 (83%). A Gore-tex (W. L. Gore and Associates, Flagstaff, AZ) patch was utilized in 14 of 21 neonates undergoing surgery. Twelve of 23 (52%) required extracorporeal membrane oxygenation (ECMO) with a 75% survival rate. Significant morbidity occurred in 10 of 19 survivors and included neurologic sequelae in 6 of 19 (32%). CONCLUSIONS: MRI was helpful in the determination of liver position and confirmation of diagnosis. The high incidence of preterm complications, frequent need for ECMO, and high prevalence of comorbidities are indicative of the severity of this CDH population and warrant close prenatal surveillance and delivery at a tertiary care center with ECMO capability.

Extracorporeal Membrane Oxygenation↗

PubMed2004

Swimming gaits, passive drag and buoyancy of diving sperm whales Physeter macrocephalus.

Drag and buoyancy are two primary external forces acting on diving marine mammals. The strength of these forces modulates the energetic cost of movement and may influence swimming style (gait). Here we use a high-resolution digital tag to record depth, 3-D orientation, and sounds heard and produced by 23 deep-diving sperm whales in the Ligurian Sea and Gulf of Mexico. Periods of active thrusting versus gliding were identified through analysis of oscillations measured by a 3-axis accelerometer. Accelerations during 382 ascent glides of five whales (which made two or more steep ascents and for which we obtained a measurement of length) were strongly affected by depth and speed at Reynold's numbers of 1.4-2.8x10(7). The accelerations fit a model of drag, air buoyancy and tissue buoyancy forces with an r(2) of 99.1-99.8% for each whale. The model provided estimates (mean +/- S.D.) of the drag coefficient (0.00306+/-0.00015), air carried from the surface (26.4+/-3.9 l kg(-3) mass), and tissue density (1030+/-0.8 kg m(-3)) of these five animals. The model predicts strong positive buoyancy forces in the top 100 m of the water column, decreasing to near neutral buoyancy at 250-850 m. Mean descent speeds (1.45+/-0.19 m s(-1)) were slower than ascent speeds (1.63+/-0.22 m s(-1)), even though sperm whales stroked steadily (glides 5.3+/-6.3%) throughout descents and employed predominantly stroke-and-glide swimming (glides 37.7+/-16.4%) during ascents. Whales glided more during portions of dives when buoyancy aided their movement, and whales that glided more during ascent glided less during descent (and vice versa), supporting the hypothesis that buoyancy influences behavioural swimming decisions. One whale rested at approximately 10 m depth for more than 10 min without fluking, regulating its buoyancy by releasing air bubbles.

Acceleration↗

PubMed2003

Fetal surgery for myelomeningocele.

INTRODUCTION: Although in utero treatment of myelomeningocele shows promise in decreasing the morbidity of this disease, the risks to the fetus are significant, and the benefits are unproven. TRIAL: The upcoming trial represents one of the few times that the pediatric neurosurgical community has come together to test a new procedure.

Cerebrospinal Fluid Shunts↗

PubMed2003

In utero limb salvage: fetoscopic release of amniotic bands for threatened limb amputation.

The natural history of extremity amniotic band syndrome (ABS) is a progression to deformity or amputation. Fetoscopic laser release of amniotic bands in extremity ABS offers the potential to prevent limb amputation. The authors report on 2 patients with isolated extremity ABS who underwent fetoscopic release. Both patients had isolated extremity ABS with compromised extremity perfusion and no other significant structural abnormality diagnosed sonographically. The first patient underwent fetoscopic release of bands of the left wrist, and the second patient underwent lysis of bands around the right wrist and an unsuspected band around the right lower extremity. Both patients had restoration of blood flow by color Doppler to the affected extremity. There were no perioperative complications. In select patients with isolated extremity ABS, early fetoscopic release may prevent amputation and allow improved limb development.

Adult↗

PubMed2003

Congenital high airway obstruction syndrome: natural history and management.

BACKGROUND: Congenital high airway obstruction syndrome (CHAOS) is a life-threatening condition with a poorly understood natural history. METHODS: A retrospective review of five patients with CHAOS between 1997 and 2002 was performed. RESULTS: All fetuses had large echogenic lungs, dilated airways, inverted diaphragms, and massive ascites. One fetus with a laryngeal cyst was terminated at 22 weeks. A twin fetus with findings suggestive of a tracheal web had progressive hydrops, which led to fetal demise. The remaining 3 patients delivered via the ex utero intrapartum treatment (EXIT) procedure survived. The first patient tolerated progressive hydrops for 12 weeks in utero. He had tracheal atresia but underwent laryngotracheoplasty successfully. He is the first long-term CHAOS survivor and is speaking at 5 years of age. The 2 patients with relatively stable lung volumes prenatally have laryngeal atresia with a pinpoint posterior laryngeal fistula. Their postnatal clinical courses were much more benign than the first survivor. CONCLUSIONS: The prenatal natural history and postnatal course of CHAOS depends on whether the airway obstruction is complete. The EXIT procedure offers the potential for salvage of this otherwise lethal condition. Hydrops may be well tolerated prenatally for weeks with potential resolution if airway fistulization is present.

Abortion, Eugenic↗

PubMed2003

Prenatal ultrasound guided percutaneous shunts for obstructive uropathy and thoracic disease.

The authors reviewed the status of closed ultrasound-guided fetal therapy using a pigtail shunt to create vesicoamniotic or thoracoamniotic decompression of the fluid-filled space. This review includes published and textbook reports of in utero therapy for bladder obstruction, pleural effusion, and macrocystic adenomatoid malformation from 1985 through 2002. For fetuses affected by lower urinary tract obstruction, the key component is identifying those fetuses that have retained renal function and are most likely to benefit from in utero shunting. This good prognosis group has been shown to have improved survival rate and a lower incidence of renal failure. Complications of fetal loss are estimated at 5% owing to the shunt procedure, and the risk of shunt displacement varies from 30% to 50%. Hydrops secondary to primary PE has been shown to be associated with low fetal and neonatal survival at 21% to 23%. Treatment by thoracoamniotic shunting increases survival rate to 75%. The fetus with a macrocystic CCAM and secondary hydrops should be considered a candidate for thoracoamniotic shunt to decrease CCAM volume, reverse hydrops, and improve survival rate. Thoracoamniotic shunt and thoracocentesis pregnancy loss risks for pleural effusion (PE) and macrocystic adenomatoid malformation of the lung (CCAM) are 5% and 0.5% to 1.0%, respectively.

Cystic Adenomatoid Malformation of Lung, Congenita↗

PubMed2003

Fetal myelomeningocele repair: short-term clinical outcomes.

OBJECTIVE: The study was undertaken to evaluate short-term clinical outcomes with antenatal myelomeningocele (MMC) repair. STUDY DESIGN: Retrospective review of 50 fetuses that underwent open fetal MMC closure was performed. Inclusion criteria included less than 26 weeks' gestation, thoracic to S1 level defect, absent clubfoot deformity, Arnold-Chiari malformation, ventriculomegaly less than 17 mm, normal karyotype, and no other anomalies. RESULTS: Perinatal survival was 94% (47/50 fetuses). Mean age at delivery was 34 weeks 3 days. All fetuses demonstrated reversal of hindbrain herniation. Forty-three percent of the 50 fetuses have required ventriculoperitoneal shunting compared with 100% thoracic, 88% lumbar, and 68% sacral (85% overall) in 297 historic controls. Better-than-predicted leg function was seen in 57% of thoracic and lumbar level lesion patients. CONCLUSION: Early experience with fetal MMC repair suggests a decreased need for ventriculoperitoneal shunting, arrest or slowing of progressive ventriculomegaly, and consistent resolution of hindbrain herniation. However, further long-term follow-up is needed to evaluate neurodevelopment and bladder and bowel function.

Adult↗

PubMed2003

Fetoscopic surgery.

Explore the source record for details and available documents.

Diseases in Twins↗

PubMed2002

Magnetic resonance imaging of fetal urinoma.

Extrarenal collections of urine have long been associated with obstructive uropathy and may preserve renal function by acting as a "popoff" valve. Although urinary extravasation manifested as urinary ascites carries a favorable prognosis, perinephric urinomas occurring prenatally are associated with poor renal function in most cases. We report the case of a baby girl with a urinoma diagnosed by fetal magnetic resonance imaging and discuss the significance of this radiologic finding.

Abnormalities, Multiple↗

PubMed2002

Fetal therapy.

Over the past 40 years, a small but increasing number of fetal genetic and congenital anomalies has become amenable to in utero treatment. Successful fetal therapies have included open procedures for congenital diaphragmatic hernia, cystadenomatoid malformation of the lung and saccrococygeal teratoma, shunts for uropathies and thoracic fluids, pharmacological therapies for congenital adrenal hyperplasia and neural tube defect prevention, and the stem cell treatment of severe combined immunodeficiency disorder.

Adrenal Hyperplasia, Congenital↗

PubMed2002

The natural history of prenatally diagnosed conjoined twins.

BACKGROUND/PURPOSE: Accurate prenatal diagnosis of complex anatomic connections and associated anomalies has only been possible recently with the use of ultrasonography, echocardiography, and fetal magnetic resonance imaging (MRI). To assess the impact of improved antenatal diagnosis in the management and outcome of conjoined twins, the authors reviewed their experience with 14 cases. METHODS: A retrospective review of prenatally diagnosed conjoined twins referred to our institution from 1996 to present was conducted. RESULTS: In 14 sets of conjoined twins, there were 10 thoracoomphalopagus, 2 dicephalus tribrachius dipus, 1 ischiopagus, and 1 ischioomphalopagus. The earliest age at diagnosis was 9 weeks' gestation (range, 9 to 29; mean, 20). Prenatal imaging with ultrasonography, echocardiography, and ultrafast fetal MRI accurately defined the shared anatomy in all cases. Associated anomalies included cardiac malformations (11 of 14), congenital diaphragmatic hernia (4 of 14), abdominal wall defects (2 of 14), and imperforate anus (2 of 14). Three sets of twins underwent therapeutic abortion, 1 set of twins died in utero, and 10 were delivered via cesarean section at a mean gestational age of 34 weeks. There were 5 individual survivors in the series after separation (18%). In one case, in which a twin with a normal heart perfused the cotwin with a rudimentary heart, the ex utero intrapartum treatment procedure (EXIT) was utilized because of concern that the normal twin would suffer immediate cardiac decompensation at birth. This EXIT-to-separation strategy allowed prompt control of the airway and circulation before clamping the umbilical cord and optimized control over a potentially emergent situation, leading to survival of the normal cotwin. In 2 sets of twins in which each twin had a normal heart, tissue expanders were inserted before separation. CONCLUSIONS: Advances in prenatal diagnosis allow detailed, accurate evaluations of conjoined twins. Careful prenatal studies may uncover cases in which emergent separation at birth is lifesaving.

Female↗

PubMed2002

The EXIT procedure: experience and outcome in 31 cases.

BACKGROUND: The EXIT (ex utero intrapartum treatment) procedure, although initially designed for reversal of tracheal occlusion in fetuses with congenital diaphragmatic hernias (CDH), has been adapted to treat a variety of fetal conditions. METHODS: A retrospective chart review of all consecutive EXIT procedures since 1996 was conducted. RESULTS: Thirty-one women underwent the EXIT procedure, with an average maternal age of 29 years (range, 20 to 38), and average gestational age of 34 weeks (range, 29 to 40). The indication was airway obstruction from fetal neck mass in 13, and reversal of tracheal occlusion from in utero clipping in 13. Singular indications included an EXIT-to-ECMO (extracorporeal membrane oxygenation) procedure for a fetus with CDH and a cardiac defect (n = 1), congenital high airway obstruction syndrome (CHAOS, n = 1), resection of a very large congenital cystic adenomatoid malformation of the lung (CCAM) on uteroplacental bypass (n = 1), unilateral pulmonary agenesis (n = 1), and thoracoomphalopagus conjoined twins. The mean duration on uteroplacental bypass (from uterine incision to umbilical cord clamping) was 30.3 plus minus 14.7 minutes (range, 8 to 66). No fetus experienced hemodynamic instability during uteroplacental bypass as recorded by fetal heart rate (FHR), pulse oximeter, and fetal echocardiography, except for one instance of reversible bradycardia from umbilical cord compression. The mean FHR and fetal saturation were 153.0 plus minus 38.5 beats per minute and 71.2% plus minus 19.9%, respectively. Five fetuses required a tracheostomy. Only 1 death occurred during an EXIT procedure because of inability to secure the airway secondary to extensive involvement by a lymphangioma. The average cord pH and pCO(2) were, respectively, 7.20 plus minus 0.11 and 63.2 plus minus 14.6. Two maternal complications occurred: bleeding from a hysterotomy site and dehiscence of an old hysterotomy scar noticed at a subsequent cesarean section. The average maternal blood loss was 848.3 plus minus 574.1 mL. CONCLUSION: The EXIT procedure was used successfully to ensure uteroplacental gas exchange and fetal hemodynamic stability during a variety of surgical procedures performed to secure the fetal airway or ensure successful transition to postnatal environment.

Adult↗

PubMed2002

Influence of congenital heart disease on survival in children with congenital diaphragmatic hernia.

OBJECTIVE: We sought to assess outcome in patients with CDH and HD to determine if LHR is also predictive of outcome in this subset of patients. STUDY DESIGN: We carried out a retrospective review (April 1996-October 2000) of patients with isolated CDH (n = 143, 82.2%) and patients with HD (n = 31, 17.8%) to determine the incidence of additional anomalies, survival to term, CDH repair, cardiac repair, and survival to discharge. Survival based on LHR was analyzed in a subset of fetuses. RESULTS: The risk of death from birth to last follow-up was 2.9 times higher for patients with CDH plus HD than for patients with CDH alone (P <.0001). Of 11 patients with CDH plus HD who had CDH repair (5 of whom also had HD repair), 5 survived. All 10 patients with an LHR <1.2 died; 3 of 6 with an LHR >1.2 survived (Fisher exact test, P =.04). CONCLUSION: Heart disease remains a significant risk factor for death in infants with CDH. The LHR helps predict survival in this high-risk group of patients.

Abnormalities, Multiple↗

PubMed2002

Fetal therapy: state of the art.

OBJECTIVE: To review our experience with the use of sonography in evaluating potential candidates for in utero fetal therapy performed at The Center for Fetal Diagnosis and Treatment at The Children's Hospital of Philadelphia. METHODS: This review article was designed to discuss open hysterotomy for the 4 fetal surgical procedures that have been performed at our institution. The procedures included surgical repair of myelomeningocele, resection of sacrococcygeal teratoma in fetuses with nonimmune hydrops, resection of an enlarging congenital cystic adenomatoid malformation that is not amenable to thoracoamniotic shunting, and tracheal clip occlusion for severe left congenital diaphragmatic hernia. RESULTS: For each surgical procedure, the use of sonography in the prenatal diagnosis of the congenital anomaly was detailed, as were indications for surgery and surgical procedures, postoperative monitoring and finally delivery, postnatal treatment, and long-term follow-up. Three of the procedures have been reasonably successful with rather dramatic results in some cases such that these techniques are still being performed. The 1 exception was open hysterotomy for the tracheal clip procedure for congenital diaphragmatic hernia, which has been abandoned. CONCLUSIONS: Fetal therapy is a rapidly evolving specialty, which is being practiced at several centers in this country. Sonography is an integral part of this specialty practice and has been used extensively in the diagnosis of some congenital anomalies that have debilitating or lethal consequences for the fetus. Technologic improvements in both sonography and magnetic resonance imaging have assisted tremendously in the many advances herein reported in the diagnosis and treatment of the above-described 4 congenital anomalies.

Cystic Adenomatoid Malformation of Lung, Congenita↗