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Biomedical subjects

A K Brown

Publications and source records attributed to A K Brown.

At least 37 records · Page 2Linked to original sources
PubMed1995

Glucose-6-phosphate dehydrogenase deficiency and carboxyhemoglobin concentrations associated with bilirubin-related morbidity and death in Nigerian infants.

Our objective was to determine whether glucose-6-phosphate dehydrogenase (G6PD) deficiency and elevated carboxyhemoglobin (COHb) levels correlated with bilirubin-related morbidity and mortality rates. For this purpose, we studied 55 clinically jaundiced infants admitted to a rural mission hospital in southern Nigeria. Total serum bilirubin levels (range, 80 to 1016 mumol/L (4.7 to 59.4 mg/dl)) correlated with the percentage COHb concentrations (COHb = 0.45 + 0.08 Total serum bilirubin; r = 0.72). Infants were divided into two groups of equal size around the median COHb concentration (COHb range, 0.43% to 5.93% (median = 1.40%), with ambient carbon monoxide of 0.65 +/- 0.03 microL/L). The COHb levels > or = 1.40% were associated with the need for exchange transfusion (15/28, or 54%, vs 5/27, or 19%; p < 0.01) and with an increased incidence of clinical findings compatible with kernicterus (9/28, or 32%, vs 0/27, or 0%; p < 0.01). Mortality rate was 29% (8/29) among infants with higher COHb levels, and 7% (2/28) in those with lower levels (p = 0.08). Thirty-one percent (14/45) of the clinically jaundiced infants tested had G6PD deficiency. Thirty-six percent of the infants with G6PD deficiency died with presumed kernicterus, compared with only 3% (1/31) of the infants with a normal G6PD screening test result (p < 0.01). These data suggest that G6PD deficiency and increased bilirubin production, as indexed by COHb, are associated with jaundice-related morbidity and death in Nigerian infants.

Bilirubin↗
PubMed1994

Reference values and hematologic changes from birth to 5 years in patients with sickle cell disease. Cooperative Study of Sickle Cell Disease.

OBJECTIVE: To examine hematologic changes from birth to 5 years of age and establish hematologic reference values for infants and children with sickle cell disease. RESEARCH DESIGN: Prospective natural history study. SETTING: Nineteen pediatric sickle cell centers across the United States. PATIENTS: Six hundred ninety-four infants with sickle cell disease (sickle cell anemia, sickle cell-hemoglobin C disease, and sickle-beta-thalassemia) who were enrolled in the Cooperative Study of Sickle Cell Disease at younger than 6 months of age. Median follow-up time through 5 years of age was 4.1 years. MEASUREMENTS AND RESULTS: We present longitudinal analyses of total hemoglobin concentration, percent fetal hemoglobin values, mean corpuscular volumes, total bilirubin concentration, and red blood cell (RBC), "pocked" RBC, white blood cell, platelet, and reticulocyte counts. Anemia was apparent by 10 weeks of life in infants with sickle cell anemia (SS infants). This anemia was associated with a rising reticulocyte count consistent with a hemolytic process. The reticulocyte count of SS infants increased steadily, exceeding 12% at 5 years of age. The fetal hemoglobin concentration of SS infants declined more slowly than that of infants with sickle cell hemoglobin C disease (SC infants). Pocked RBC counts rose sharply after 6 months of age, and by 1 year, 28% of SS infants had abnormal counts, above 3.5%, indicating poor splenic function. At 3 years of age, 78% of SS patients and 32% of SC patients had abnormal pocked RBC counts. The SS patients with concurrent alpha-thalassemia had, after 6 months of age and throughout early childhood, a slightly higher mean total hemoglobin concentration and lower mean pocked RBC and reticulocyte counts than SS patients without alpha-thalassemia. The hematologic profile of SC infants more closely resembled that of normal black infants, but there was mild anemia (10.5 g/dL) and slightly elevated mean values for reticulocytes (3%) and fetal hemoglobin (3%) during early childhood.

Age Factors↗
PubMed1994

The influence of infant and maternal sickle cell disease on birth outcome and neonatal course.

OBJECTIVE: To compare the influence of maternal hemoglobin phenotype as well as that of the infant on birth outcome and neonatal complications. RESEARCH DESIGN: Prospective, natural history study with retrospective chart review for neonatal complications. SETTING: Nineteen pediatric sickle cell centers across the United States. PATIENTS: Four hundred eighty infants with sickle cell disease (SCD) who were enrolled in the Cooperative Study of Sickle Cell Disease at less than 6 months of age, as well as a comparison cohort of 118 infants with sickle cell trait born to women with sickle cell anemia in the Cooperative Study. RESULTS: In the SCD cohort, overall rates of preterm (< 37 weeks), low-birth-weight (< 2500 g), and small-for-gestational age births were 9%, 10%, and 8%, respectively; no significant differences were found according to infant hemoglobin phenotype. Term births accounted for 59% of the infants with low birth weight, significantly higher than the 41% US rate for black low-birth-weight infants (P = .014). Expectant mothers with sickle cell anemia are 2.5 times more likely to bear newborns who are small for gestational age than are women with other types of sickle cell disease, sickle trait, or C-trait. The most common prepartum and neonatal complications in infants with SCD were jaundice (25%), fetal distress (13%), anemia (10%), and respiratory distress (6%). Complication rates did not differ significantly by hemoglobin phenotype in the infants with SCD, but infants born to women with sickle cell anemia had higher rates of jaundice (P < .0001). CONCLUSIONS: Rates of adverse birth outcomes and neonatal complications in infants with SCD are similar to the rates for normal infants, although preterm birth accounts for fewer of the low-birth-weight outcomes among newborns with SCD relative to US black newborns. The hemoglobin phenotype of infants with SCD does not influence birth outcome and neonatal course, but infants born to women with sickle cell anemia are at greater risk of preterm birth, low birth weight, being small for gestational age, and neonatal jaundice.

Anemia, Sickle Cell↗
PubMed1992

Effects of delayed reinforcement on infant vocalization rate.

Three previous studies have failed to demonstrate conditioning in infants using a 3-s delay of reinforcement. The effects of a delayed reinforcement schedule on vocalization rates therefore were explored in a single-subject repeated-reversal experimental design for 3 4- to 6-month-old normally developing infants. Each infant received delayed social reinforcement from his or her parent for vocalizing. The comparison condition was a schedule of differential reinforcement of behavior other than vocalizations to control for elicitation by social stimulation. An operant level of infant vocalizations was the initial condition, after which the differential reinforcement schedule was implemented in an across-subjects multiple baseline design. Infants' vocalization rates increased above levels measured during differential reinforcement following onset of the delayed reinforcement condition. Also, vocalization rates decreased during differential reinforcement compared to operant levels. The successful use of delayed reinforcement schedules with infants in this study, as opposed to others, is discussed in terms of procedural differences among them.

Arousal↗
PubMed1990

Newborn screening for sickle cell disease. When is an infant 'lost to follow-up'?

Success of programs to screen newborns for sickle cell disease depends on timely follow-up. Education regarding fever and splenic palpation, and initiation of prophylactic penicillin therapy, will reduce morbidity and mortality and should occur prior to 4 months of age. However, contacting parents to permit implementation of care may be difficult, particularly in large urban populations; only nine (36%) of 25 infants recently identified as having sickle cell disease arrived at our institution for initial appointments. Medical providers must be aware of medical and legal obligations related to follow-up of newborns with sickle cell disease to prevent untoward events in "missed cases."

Follow-Up Studies↗
PubMed1990

The use of radiotelemetry after discharge from the coronary care unit.

Forty-six of 110 consecutive admissions to the coronary care unit (CCU) were monitored by telemetry after discharge from the unit. One of three patients with sudden cardiac death was resuscitated successfully and four patients developed atrial fibrillation which resulted in investigation by echocardiography and treatment with anticoagulants. Significant ventricular ectopic activity was detected in four other patients. Arbitrary selection of patients resulted in those with complicated courses in the CCU being more likely to be monitored by telemetry after transfer to the ward than those which were uncomplicated. There were no cases of sudden cardiac death in patients who did not have telemetry. The cost of telemetry was 2,775 pounds per system. All 19 districts in the North-West region of the UK responded to a questionnaire. Five of the 19 used telemetry but only two of these used the technique routinely after discharge from the CCU whereas four used radiotelemetry to monitor patients on the ward when coronary care beds were unavailable. Eight districts wanted telemetry but needed funds. We conclude that radiotelemetry is an inexpensive way to detect serious arrhythmias in patients transferred from the CCU to the general ward. Monitored from the CCU, cardiac arrest can be immediately detected and treated by experienced staff. Asymptomatic atrial fibrillation leads to prompt investigation by echocardiography and possible treatment with anticoagulants. The importance of noticing major ventricular ectopic activity is likely to increase with the possibility of selecting patients with a high risk of life-endangering arrhythmias so that antiarrhythmic drugs or techniques such as automatic defibrillators can be used appropriately.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Gunshot wounds then and now.

This review is a study of the development of the bullet and its effects, and the surgical treatment of gunshot wounds from John Hunter's time to the present day.

Art↗
PubMed1988

Oral dantrolene sodium for tonsillectomy pain: a double-blind study.

Tonsillectomy in adults and older children is typically accompanied by 7 to 14 days of pain. On the basis of clinical observations of patients treated perioperatively with dantrolene sodium for malignant hyperthermia, we hypothesized that pharyngeal muscle spasms are a major factor in tonsillectomy pain. We entered 113 patients, 11 years of age and older, into a double-blind, placebo-controlled study to evaluate the effectiveness of dantrolene sodium in reduction of tonsillectomy pain. Patients were randomly assigned either dantrolene (1.5 mg/kg per day) or placebo orally four times a day for 5 days postoperatively. On a standardized questionnaire, the patient recorded pain, diet, activity level, analgesics, and side effects, daily for 2 weeks. Also, alkaline phosphatase (alk phos) and serum aspartate aminotransferase (SGOT) levels were determined before the operation and 2 weeks after. Patients who received dantrolene had no significant differences in subjective pain, diet, or activity level scores from those of patients who received placebo. Dantrolene patients did, however, require significantly less analgesic use than placebo patients (p = 0.034, 0.015, and 0.005 for postoperative days 2, 3, and 4, respectively). There was no significant difference in side effects or changes in liver enzyme between the dantrolene and placebo groups. We conclude that dantrolene sodium, given in the dosage noted, is effective in reduction of analgesic requirements after tonsillectomy.

Administration, Oral↗
PubMed1987

Salvage mechanisms for regeneration of adenosine triphosphate in rat cardiac myocytes.

Since mitochondrial oxidative phosphorylation does not produce sufficient adenosine triphosphate for rapid restoration of contractile function in myocardium reoxygenated after ischaemia alternative non-oxidative routes by which purine nucleosides or bases may be used to increase the cytoplasmic adenine nucleotide pool were studied. Comparative rates of uptake and salvage of adenosine, adenine, and hypoxanthine were determined using myocytes isolated from adult rat heart. For each precursor reactions limiting the overall rate at which substrate in the extracellular fluid is incorporated into the intracellular adenosine triphosphate pool were identified. Adenosine was salvaged at twice the rate seen with adenine in the presence of ribose, whereas the rate of salvage of hypoxanthine, in the presence of ribose, was only 5% of that for adenosine. Adenine may be an advantageous substrate since high concentrations of adenine are not inhibitory to salvage and do not influence cardiac haemodynamics. Salvage of hypoxanthine appeared to be limited by the rate of adenylosuccinate synthetase, which was present at less than 1% of the adenylosuccinase rate in rat, rabbit, and beef heart. In addition, since salvage of bases is dependent on the availability of phosphoribosylpyrophosphate rates of synthesis of phosphoribosylpyrophosphate were measured in whole myocytes from ribose and in cytoplasmic extracts from ribose and from ribose-5-phosphate. Metabolic sites were identified at which interventions designed to accelerate salvage rates might best be directed.

Adenine↗