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Biomedical subjects

A R Cohen

Publications and source records attributed to A R Cohen.

At least 55 records · Page 3Linked to original sources
PubMed1997

Superior in vivo response of recombinant factor VIII concentrate in children with hemophilia A.

OBJECTIVE: Our previous experience with highly purified plasma-derived factor VIII (pdFVIII) concentrates showed that adult dosage recommendations were not applicable to children. In this study, we compared the in vivo response and recovery of recombinant factor VIII (rFVIII) with those of highly purified pdFVIII concentrate in children with hemophilia A. STUDY DESIGN: Ten boys with severe factor VIII deficiency and no concurrent bleeding episodes participated in a masked, prospective, crossover study comparing factor VIII coagulant activity after infusion of 50 units of pdFVIII and rFVIII products per kilogram of body weight. RESULTS: Mean peak factor VIII response with rFVIII was 1.91% +/- 0.14%, significantly better than the response observed with highly purified pdFVIII of 1.5% +/- 0.15% (p = 0.007). Mean peak factor VIII recovery was 100.5% with rFVIII versus 78.7% with pdFVIII (p = 0.007). Positive correlations between response to rFVIII and body surface area (r = 0.734, p = 0.015), body weight (r = 0.762, p = 0.01), and plasma volume (r = 0.659, p = 0.03) were observed. CONCLUSIONS: Infusion of rFVIII produced a significantly better response and recovery in vivo than infusion of highly purified pdFVIII in children. The response in children after infusion of rFVIII was similar to the response previously observed in adults.

Adult↗
PubMed1997

Screening for hereditary spherocytosis by use of automated erythrocyte indexes.

OBJECTIVE: To determine whether the mean corpuscular hemoglobin concentration (MCHC) or other erythrocyte indexes, as determined by automated cell counters, remains a useful screening test for identifying patients with hereditary spherocytosis (HS). METHODS: Erythrocyte indexes from 112 children with HS who had not undergone splenectomy were compared with those measured in an equal number of healthy, age-matched children. All indexes were derived from measurements obtained by aperture impedance. RESULTS: Mean corpuscular hemoglobin concentration in the HS group was 35.9 gm/dl, significantly higher than in normal control subjects (34.3 gm/dl; p < 0.001). Mean erythrocyte distribution width also was significantly higher in patients with HS (19.3 vs 12.6; p < 0.001). The MCHC distinguishes individuals with HS, with an area under the receiver operating characteristic curve of 0.86. Although not disease specific, an erythrocyte distribution width > 14 has 85% sensitivity and 97% specificity and an area under the receiver operating characteristic curve of 0.92. An MCHC > 35 gm/dl has a sensitivity of 70% and a specificity of 86%. Combining the MCHC and erythrocyte distribution width increases the area under the receiver operating characteristic curve to 0.97. Specificity is 100% and likelihood ratio is infinite when both the MCHC and erythrocyte distribution width are elevated. CONCLUSIONS: The automated MCHC is an effective screening test to identify children with HS. An elevated erythrocyte distribution width adds additional specificity and is itself a powerful screening tool. The combination of the two tests is an excellent predictor for the diagnosis of HS.

Adolescent↗
PubMed1997

Neurologic complications of treatment of childhood acute immune thrombocytopenic purpura with intravenously administered immunoglobulin G.

We studied the incidence, associated morbidity, and impact on health care charges of neurologic complications in 38 children with acute immune thrombocytopenic purpura (ITP) treated with intravenously administered IgG. Thirteen patients (34%) had transient neurologic complications, manifested by severe headache, nausea, and, rarely, aseptic meningitis. Computed tomography was performed in nine patients. Twelve patients were hospitalized longer than was required for their ITP alone. Neurologic complications caused by the IgG preparations used in the treatment of childhood ITP occur more frequently than has previously been suggested and may substantially increase the cost of treatment.

Acute Disease↗
PubMed1997

The role of neuroendoscopy in the treatment of pineal region tumors.

The authors describe a technique for the initial management of patients with pineal region neoplams and symptomatic hydrocephalus. Endoscopic third ventriculostomy and, if possible, tumor biopsy are performed through a single precoronal burr hole. When indicated, formal tumor resection can be performed nonemergently, without the need for ventricular drainage or shunting.

Adult↗
PubMed1997

Pearl jam.

Explore the source record for details and available documents.

Arnold-Chiari Malformation↗
PubMed1997

The presurgical management with erythrocytapheresis of a patient with a high-oxygen-affinity, unstable Hb variant (Hb Bryn Mawr).

BACKGROUND: Hemoglobin (Hb) Bryn Mawr is an unstable Hb variant resulting in congenital hemolytic anemia. This variant Hb also has an increased affinity for oxygen. The perioperative transfusion management of this disorder is described, and the first genomic analysis of this Hb variant is given. CASE REPORT: An 11-year-old boy, heterozygous for Hb Bryn Mawr, was referred for cholecystectomy. Sequence analysis of genomic DNA confirmed that the patients was heterozygous for a T-->C transition in the codon for amino acid 85, causing a substitution of serine for phenylalanine in the beta-globin chain. On the basis of whole-blood O2 dissociation studies, projected tissue O2 delivery would have been suboptimal during general anesthesia; therefore, a partial red cell exchange transfusion was performed to lower variant Hb and prevent tissue hypoxia during surgery. The red cell mass to be exchanged (50%) was determined from the calculated increase in O2 delivery capacity required to maintain an O2 extraction of 4 to 5 mL of O2 per dL of whole blood. The p50 of whole blood from the patients immediately after the exchange transfusion was 16.0 torr. At the time of surgery, the p50 was normal (25.9 torr). The patient's whole blood 2,3 DPG levels were 4.70 mmol per mL of red cells (before transfusion) (normal range = 4.8 +/- 0.3 mmol/mL red cells), 4.07 mmol per mL of red cells (immediately after transfusion), and 4.55 mmol per mL of red cells (48 hours after transfusion). CONCLUSION: This patient with Hb Bryn Mawr was prepared for surgery with a partial exchange transfusion to prevent tissue hypoxia during anesthesia. Decreased 2,3 DPG levels immediately after transfusion resulted in increased O2 affinity of whole blood; however, 48 hours after exchange transfusion, a normal p50 (due to both removal of variant Hb and regeneration of 2,3, DPG) was observed. Partial exchange transfusion is useful in the preoperative management of patients with Hb variants characterized by increased O2 affinity.

2,3-Diphosphoglycerate↗
PubMed1997

Early experience with biodegradable fixation for congenital pediatric craniofacial surgery.

We describe early experience using a polymeric bioresorbable bone fixation system in a consecutive series of eight pediatric patients for the correction of craniofacial malformations. Indications for surgical treatment included craniosynostosis (7) and encephalocele (1). All patients underwent bifrontal craniotomies with cranial vault or orbital reconstruction or both. Segments were then stabilized using bioresorbable fixation systems. Patients were evaluated pre- and postoperatively clinically and with radiographs and photographs. Mean follow-up was 4.5 months, with a minimum follow-up of 3 months. In seven of eight patients, there was no incidence of infection, extrusion, exposure, erythema, instability of the advanced segments, relapse, hematoma, seroma formation, or adverse inflammatory reaction. One patient experienced difficulty with respect to system imperfections (i.e., drill holes after tapping were too large for screws). This study demonstrated the efficacy of bioresorbable plates and screws for the growing pediatric craniofacial patient; excellent short-term results were achieved. Prospective studies and longer longitudinal follow-up of larger numbers of patients are desirable to confirm these findings.

Absorbable Implants↗
PubMed1997

Neoadjuvant chemotherapy for hypervascular malignant brain tumors of childhood.

Some large hypervascular brain tumors pose an exceptional challenge to surgical resection, particularly in young children with small blood volumes. To limit blood loss during resection of hypervascular tumors, the authors used upfront chemotherapy as the primary treatment modality in 2 young children. This produced a dramatic reduction in tumor size and vascularity and greatly facilitated definitive surgical removal.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

Serum HIV-1 RNA levels and time to development of AIDS in the Multicenter Hemophilia Cohort Study.

OBJECTIVE: To determine if the long-term incidence of the acquired immunodeficiency syndrome (AIDS) is related to human immunodeficiency virus type 1 (HIV-1) RNA levels measured early in HIV-1 infection. DESIGN: Epidemiologic cohort study. SETTING: Five hemophilia treatment centers in the United States. SUBJECTS: A total of 165 subjects with hemophilia and HIV-1 infection (age at HIV-1 seroconversion, 1-66 years) followed from 1979 to 1995. METHODS: The HIV-1 RNA level was measured by polymerase chain reaction over a range of 200 to 1 million or more HIV-1 RNA copies/mL in archived serum specimens collected 12 to 36 months (median, 27 months) after the estimated date of HIV-1 seroconversion. Kaplan-Meier methods were used to examine the risk of AIDS and proportional hazards models were used to estimate relative hazards. RESULTS: The HIV-1 RNA values were similar in subjects younger than 17 years at seroconversion (median, 5214 copies/mL) and those 18 to 34 years old (median, 4693 copies/mL), but higher in those 35 years or older (median, 12069 copies/mL) (P = .02 compared with each younger group). At 10 years after seroconversion, the proportions of subjects with AIDS were 72% among subjects with 100,000 or more HIV-1 RNA copies/mL measured 12 to 36 months after HIV-1 seroconversion (n = 9), 52% among subjects with 10,000 to 99,999 copies/mL (n = 55), 22% among subjects with 1000 to 9,999 copies/mL (n = 82), and 0% among subjects with fewer than 1000 copies/mL (n = 19) (P < .001). The age-adjusted relative hazard for AIDS for subjects with 10,000 or more copies/mL was 14.3 (95% confidence interval, 1.9-105.6) compared with subjects with fewer than 1000 copies/mL. CONCLUSIONS: The HIV-1 RNA level during early chronic HIV-1 infection is a strong, age-independent predictor of clinical outcome; low levels define persons with a high probability of long-term AIDS-free survival.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Osteolysis circumscripta evanescans.

A circumscribed radiolucent skull abnormality was detected on plain radiographs obtained to evaluate minor cranial trauma in a young boy. The lesion disappeared on follow-up X-rays performed later in the day. Analysis of the case revealed that the lesion was an artifact resulting from a superimposed hole in a wooden backboard on which the patient was X-rayed initially. Radiographs shot through a protective backboard may be misleading, and not all abnormalities identified belong to the patient.

Artifacts↗
PubMed1996

The changing profile of homozygous beta-thalassemia: demography, ethnicity, and age distribution of current North American patients and changes in two decades.

BACKGROUND: The age of patients with homozygous beta-thalassemia is increasing because of better treatment and decreased births. A countering influence is immigration of ethnic groups with a high prevalence of thalassemia. METHODS: a questionnaire sent to 48 North American centers requested information about current patients with homozygous beta-thalassemia: age, clinical severity, and ethnicity. An 83% response was obtained. Twelve reference hospitals that participated in similar surveys in 1972 and 1984 were included. RESULTS: Five hundred eighteen patients with homozygous beta-thalassemia represent most North American patients. Four hundred forty-three (86%) of these had transfusion-dependent thalassemia major (TM); 75 (14%) had thalassemia intermedia (TI). Sixty-two percent were of Greek and Italian ancestry. There were approximately equal numbers of patients with TM in 5-year intervals between 0 and 25 years of age. Thereafter, the numbers of patients fell sharply. The mean age (+/- SD) of the patients with TM was 16.1 +/- 9.2 years. Striking differences were seen in Italian and Greek patients compared with those of other ancestries. Sixty-six percent of the 271 Italian and Greek patients with TM were older than 16 years of age, whereas 77% of the 172 patients of other ethnic groups with TM were younger than 15 years of age. The mean age of the 75 patients with TI was greater than that of the patients with TM. Seventy-three percent of African-American patients had TI, compared with 0% of Southeastern Asian patients. Comparisons of patients with TM from the 12 reference hospitals for two decades show increasing mean ages of TM patients (1973, 11.4 +/- 6.7 years; 1985, 14/2 +/- 7.3 years; and 1993, 16.1 +/- 9.2 years). CONCLUSIONS: There are probably only 750 to 1000 patients with homozygous beta-thalassemia in North America. Only about 15 to 20 new cases are diagnosed each year. The increasing mean age and age distribution indicate that modern therapies are effective, but immigration of non-Mediterranean ethnic groups with thalassemia has resulted in more, younger patients. TM is increasingly becoming a disease of young adults.

Adolescent↗
PubMed1995

The use of capnography for recognition of esophageal intubation in the neonatal intensive care unit.

Failure to recognize esophageal intubation can result in severe hypoxia and permanent neurologic injury. Capnography is a standard monitoring modality in the operating room but has not been utilized fully in other environments. We used capnography at the time of endotracheal intubation in the neonatal intensive care unit (NICU) to determine whether capnography could more quickly and accurately identify endotracheal tube position than other clinical indicators of endotracheal tube position. One hundred intubation episodes were studied in 55 neonates. Capnograms were obtained 15 and 120 sec following tube placement. Intubating personnel were blinded to the capnographic data and determined endotracheal tube location (trachea vs. esophagus) by clinical criteria only. The sensitivity and specificity of capnography and clinical examination for identification of tube position were analyzed, and the time required for establishing by clinical confirmation whether the tube was in the trachea or not was compared to that required for capnography. Forty of 100 intubation attempts resulted in esophageal intubation. Capnography correctly identified these errant tube placements in 39 of 40 instances and did so in 1.6 sec (SD +/- 2.4). Capnography failed to identify successful endotracheal intubation on only one occasion. Clinical indicators of tube position required 97.1 sec (SD +/- 92.6) to identify an esophageal intubation and failed to identify successful endotracheal intubation in 5 of 60 cases. We conclude that capnography is a valuable adjunct to clinical examination to demonstrate whether an endotracheal tube is placed correctly in the trachea of neonates in the NICU.

Blood Gas Monitoring, Transcutaneous↗
PubMed1995

Loss of detectable antibody to hepatitis B surface antigen in immunized patients with hemophilia but without human immunodeficiency virus infection.

We investigated the loss of detectable antibody directed against the hepatitis B surface antigen after immunization with hepatitis B vaccine in 55 patients who were seronegative for the human immunodeficiency virus and had hemophilia. Twenty percent of patients lost detectable antibody at a mean of 4.6 years after completion of immunization. Monitoring of hepatitis B serostatus or routine revaccination may be necessary.

Child↗
PubMed1995

Human immunodeficiency virus (HIV) type 1 infection status and in vitro susceptibility to HIV infection among high-risk HIV-1-seronegative hemophiliacs.

Blood samples were obtained from 16 hemophiliacs who had a 50%-94% defined risk of human immunodeficiency virus (HIV) type 1 infection on the basis of treatment history and from 14 controls not at risk for HIV infection. HIV-1 was not detected in any of 12 patient samples by cocultivation nor in 14 patient samples by the polymerase chain reaction. Peripheral blood cells from 7 seronegative hemophiliacs at highest risk of seroconversion (94%) were less susceptible to HIV-1 infection in vitro than were cells from healthy controls (P < .025, one-tailed Wilcoxon rank sum test). In contrast, the susceptibility to HIV-1 infection of lymphocytes from 6 seronegative hemophiliacs at moderate risk (50%-56%) of seroconversion did not differ from that of cells from controls or from high-risk hemophiliacs. Therefore, prolonged periods of seronegative HIV-1 infection are not common in this high-risk population. In addition, among hemophiliacs there may exist heterogeneity in susceptibility to HIV-1 infection in vitro and in vivo.

Adult↗
PubMed1995

Endoscope-assisted craniotomy: approach to the rostral brain stem.

We describe a surgical technique to improve visualization of deep brain structures during craniotomy. The technique, developed in a cadaveric model, combines the use of an operating microscope and a solid-rod lens endoscope. Addition of the endoscope during craniotomy allows the operator to visualize structures that otherwise might not have been seen. An approach to the brain stem is demonstrated.

Brain Stem↗
PubMed1995

Caudal agenesis and associated caudal spinal cord malformations.

Caudal agenesis is a rare congenital anomaly resulting from an insult to the structures of the caudal eminence. It may be associated with anomalies of other structures derived from the caudal eminence: the hindgut and the urogenital system. Patients are more likely to present first to the pediatric surgeon (for evaluation of gastrointestinal anomalies), the urologist (for urogenital malformation or dysfunction), or the orthopedic surgeon (for lower extremity abnormalities), than to the neurosurgeon. Characteristic external features of the buttocks, hips, and lower extremities may suggest the diagnosis. MR imaging is the diagnostic modality of choice and should be used in all patients with suggestive external features or other caudal anomalies. The level of bone anomaly corresponds well to the level of weakness but not sensory loss. Sensation is usually relatively preserved. The caudal spinal cord is often truncated in cases of high bone lesions and tethered, with occasional association with a dysraphic lesion, in cases of low bone lesions. Early neurosurgical intervention is preferred in all cases of recognized occult spinal dysraphism. Progressive neurologic deficits may develop later in life in patients with unrecognized tethered cord or dural stenosis and require neurosurgical repair on diagnosis. A better understanding of the embryology of the caudal region and investigation of the teratogens that may interfere with this stage of development should lead to more effective treatment and prevention of caudal agenesis and the associated caudal anomalies.

Abnormalities, Multiple↗
PubMed1994

Risks of immunodeficiency, AIDS, and death related to purity of factor VIII concentrate. Multicenter Hemophilia Cohort Study.

In HIV-infected subjects with haemophilia, CD4 counts seem to fall more slowly in those on high-purity factor VIII (FVIII) than on intermediate-purity product. We evaluated whether risks for AIDS or death were associated with either product among 411 HIV-infected individuals. The relative hazard of AIDS was slightly elevated for both current (1.34) [corrected] and cumulative (1.01 per month) use of high-purity products (neither significant). The corresponding hazards for death were 1.49 and 1.03 (neither significant). Thus we found no evidence that high-purity FVIII concentrates retard the development of AIDS.

Acquired Immunodeficiency Syndrome↗