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Biomedical subjects

D W Green

Publications and source records attributed to D W Green.

At least 37 records · Page 2Linked to original sources
PubMed2000

Congenital scoliosis.

Congenital scoliosis is a deformity of the developing spine that results from defects in vertebral development. The developmental etiologies may be classified as either a failure of formation, a failure of segmentation, or a mixture of these two modes of maldevelopment. Early detection and close surveillance of congenital scoliosis is critical, as a rapidly progressive curve may lead to significant deformity, pulmonary restriction, and neurologic problems if not treated. Early surgical treatment is often necessary for rapidly progressive curves.

Cervical Vertebrae↗
PubMed2000

Anaesthesia, perioperative management and outcome of correction of extrahepatic biliary atresia in the infant: a review of 50 cases in the King's College Hospital series.

Extrahepatic biliary atresia (EHBA) is an uncommon condition presenting in the first few weeks of life. It has an incidence of 0. 5-1 per 10 000 live births and is the end result of a destructive inflammatory process involving the extrahepatic biliary system of unknown aetiology occurring in utero. The net result is neonatal jaundice due to bile stasis, with subsequent hepatocellular damage and cirrhosis. In the untreated, patient death is inevitable within 2 years. Precise diagnosis (or exclusion) of EHBA in the persistently jaundiced infant must be made urgently and major surgery (hepatic portoenterostomy: Kasai procedure) carried out as soon as possible, preferably before 6-8 weeks of age. This review is concerned with anaesthesia for correction of EHBA in 50 consecutive patients and also outlines the experience gained in the largest European centre for correction of EHBA where the number of cases now approaches 500.

Anesthesia↗
PubMed1999

The modified Fontan procedure: morphometry and surgical implications.

BACKGROUND: The modified Fontan procedure for patients with only one well-formed ventricle is now widely regarded as palliative, not curative. METHODS: To improve the surgical management and postoperative follow-up of such patients, a morphometric study of 33 postmortem cases was done. RESULTS: The three main causes of death were congestive heart failure (82%), arrhythmias (12%), and central nervous system dysfunction (6%). The cross-sectional area of the Fontan anastomosis (FA) relative to the systemic venous area (SVA) and relative to the body surface area (BSA) revealed that the Fontan pathway was often obstructive. The mean FA/SVA index was 73% less than normal: 0.54 +/- 0.22, range 0.13 to 0.98. The mean FA/BSA index was 70% less than normal: 143.52 +/- 50.01 mm2/M2, range 55.09 to 261.67 mm2/M2. CONCLUSIONS: The main surgical challenge is to minimize or eliminate prepulmonary stenosis. Although significant postoperative obstruction was often not evident hemodynamically because of small or absent gradients, the presence of important obstruction of the Fontan pathway was clearly revealed by morphometry.

Adolescent↗
PubMed1999

Nucleated red blood cells in infants of smoking mothers.

OBJECTIVE: To evaluate whether the absolute nucleated red blood cell (RBC) count is elevated in term, appropriate for gestational age (AGA) infants born to smoking women. METHODS: We compared absolute nucleated RBC counts taken during the first 12 hours of life in two groups of term, vaginally delivered, AGA infants, one group born to mothers who smoked during pregnancy (n = 30) and the other born to mothers who did not smoke (n = 30). We excluded infants of women with diabetes, hypertension, or alcohol or drug abuse, and infants with heart rate abnormalities, hemolysis, blood loss, or chromosomal anomalies. RESULTS: There were no differences between the groups in birth weight, gestational age, maternal age, gravidity, parity, maternal analgesia during labor, 1- and 5-minute Apgar scores, corrected white blood cell counts, lymphocyte counts, or hematocrits. The median absolute nucleated RBC count in infants of smoking mothers was 0.5 x 10(9)/L (range 0 to 5.0) versus 0.0005 x 10(9)/L (range 0 to 0.6) in nonsmoking controls (P < .002). Regression analysis that included Apgar scores, gestational age, and number of cigarettes smoked per day showed a significant correlation of absolute nucleated RBC count only with the number of cigarettes smoked per day (P < .001). CONCLUSION: At birth, term AGA infants born to smoking mothers have increased circulating absolute nucleated RBC counts compared with controls. The absolute nucleated RBC count in newborns correlates with the number of cigarettes smoked during pregnancy.

Adult↗
PubMed1999

A functional imaging study of translation and language switching.

The neural systems underlying translation and language switching were investigated using PET. Proficient German-English adult bilinguals were scanned whilst either translating or reading visually presented words in German (L1), English (L2) or alternating L1/L2. We refer to alternating L1/L2 as 'switching'. The results revealed contrasting patterns of activation for translation and switching, suggesting at least partially independent mechanisms. Translation, but not switching, increased activity in the anterior cingulate and subcortical structures whilst decreasing activation in several other temporal and parietal language areas associated with the meaning of words. Translation also increased activation in regions associated with articulation (the anterior insula, cerebellum and supplementary motor area) arguably because the reading response to the stimulus must be inhibited whilst a response in a different language is activated. In contrast, switching the input language resulted in activation of Broca's area and the supramarginal gyri, areas associated with phonological recoding. The results are discussed in terms of the cognitive control of language processes.

Adult↗
PubMed1999

Orthopedics.

Explore the source record for details and available documents.

Child↗
PubMed1999

Scheuermann's kyphosis.

Scheuermann's disease is a kyphotic deformity of the spine that develops in early adolescence. This condition has been reported to occur in 0.4% to 8% of the general population, with an equal distribution between sexes. Diagnosis of Scheuermann's disease is suggested on clinical examination; however, parents of children affected often confuse it with poor posture. Radiographs are the standard imaging modality used to confirm the diagnosis of Scheuermann's disease. Classic signs include vertebral end plate irregularity, disk space narrowing, and anterior wedging of involved vertebral bodies. Other diagnostic tools such as CT scans or magnetic resonance imaging may also be of value in the evaluation of Scheuermann's disease. The mode of treatment for this condition depends upon the severity of the deformity, remaining growth, and presence or absence of symptoms. Early treatment may be limited to observation and exercises, whereas patients who have kyphosis of up to 75 degrees and how have growth remaining may benefit from bracing. Surgical correction is reserved for severe cases that are symptomatic and refractory to conservative management.

Adolescent↗
PubMed1998

Mivacurium compared with succinylcholine in children with liver disease.

We have compared mivacurium and succinylcholine in 27 paediatric patients with mild (Child's A) to moderate (Child's B) liver disease undergoing oesophagogastroduodenoscopy (OGD) and injection of oesophageal varices, with 10 healthy children receiving mivacurium for ENT procedures. With mivacurium 0.2 mg kg-1, the severity of liver disease did not correlate with duration of block compared with controls (time from bolus to T1 25%, P = 0.74; T1 25% to T4:T1 > 0.7, P = 0.545). However, initial recovery (time to T1 25%, P = 0.002) and overall recovery (bolus to T4:T1 > 0.7, P = 0.004) from mivacurium-induced neuromuscular block correlated inversely with pre-existing concentrations of plasma cholinesterase. Conditions for tracheal intubation at 2 min with mivacurium were comparable with conditions at 1 min with succinylcholine in the liver patients.

Child↗
PubMed1998

Preconditioning in rat hearts is independent of mitochondrial F1F0 ATPase inhibition.

Mitochondrial F1F0 adenosinetriphosphatase (ATPase) is responsible for the majority of ATP synthesis during normoxic conditions, but under ischemic conditions it accounts for significant ATP hydrolysis. A previous study showed that preconditioning in isolated rat hearts is mediated by inhibition of this ATPase during ischemia. We tested this hypothesis in our isolated rat heart model of preconditioning. Preconditioning was accomplished by three 5-min periods of global ischemia separated by 5 min of reperfusion. This was followed by 20 min of global ischemia and 30 min of reperfusion. Preconditioning significantly enhanced reperfusion contractile function and reduced lactate dehydrogenase release but paradoxically reduced the time to onset of contracture during global ischemia. Myocardial ATP was depleted at a faster rate during the prolonged ischemia in preconditioned than in sham-treated hearts, which is consistent with the reduced time to contracture. ATP during reperfusion was repleted more rapidly in preconditioned hearts, which is consistent with their enhanced contractile function. Preconditioning significantly reduced lactate accumulation during the prolonged ischemia. We were not able to demonstrate that mitochondrial F1F0 ATPase (measured in submitochondrial particles) was inhibited by preconditioning before or during the prolonged ischemia. The mitochondrial ATPase inhibitor oligomycin significantly conserved ATP during ischemia and increased the time to the onset of contracture, which is consistent with inhibition of the mitochondrial ATPase. Our results show that preconditioning in rat hearts can be independent of mitochondrial ATPase inhibition as well as ATP conservation.

Adenosine Triphosphate↗
PubMed1997

Hazard assessment of boric acid in toys.

Boric acid (H3BO3) has been used in a wide variety of applications--medication, pesticides, and household products. Reports of child poisoning by H3BO3 were common in the clinical literature before 1975. However, a decline in its use as a bacteriostatic agent coupled with increased regulatory control has almost eliminated poisonings by accidental ingestion. Schedule I (Part I, Item 8) of the Hazardous Products Act of Canada, proclaimed in the late 1960s, followed in the wake of concerns about accidental poisoning and prohibits its use in toys. Since that time, scientific knowledge has increased and has led to a reevaluation of the hazard associated with H3BO3. A maximum tolerated dose (MTD) was sought for children in the most susceptible age range, with a view to determine a maximum acceptable concentration (MAC) in toys. The effects of H3BO3 in a variety of exposure scenarios were evaluated. Precedence was given to clinical data in humans, particularly children, since there is no suitable animal model of boric acid intoxication. An extensive search of the pediatric literature was conducted to find a no-observed-adverse-effect level (NOAEL) or a lowest-observed-adverse-effect level (LOAEL). An analysis of the pivotal study to the present assessment resulted in the application of an uncertainty factor of 100 to account for variations in sensitivity among children and for the use of a LOAEL. Based on a pediatric LOAEL of 300 mg/kg body wt, we derived a MTD of 3 mg H3BO3/ kg body wt and a MAC of 9.1 mg H3BO3/g of toy. These results compared favorably with calculations from other human and animal NOAELs/LOAELs.

Administration, Oral↗
PubMed1997

Nucleotide regulation and characteristics of potassium channel opener binding to skeletal muscle membranes.

[3H]P1075 binding to membrane preparations of rabbit skeletal muscle were observed in the presence of nucleotide triphosphates or diphosphates but not AMP, cAMP, adenosine, tripolyphosphate, or pyrophosphate. Nonhydrolyzable or poorly hydrolyzable ATP analogs inhibited MgATP-supported binding. The EC50 value for MgATP-supported binding (0.4 mM) was decreased approximately 10-fold in the presence of an ATP-regenerating system, and significant metabolism by membrane nucleotidases was confirmed by high performance liquid chromatographic analysis. [3H]P1075 bound to skeletal muscle with a Kd value of 37 +/- 3 nM and a Bmax value of 280 +/- 14 fmol/mg of protein. [3H]P1075 binding to subcellular fractions was highest in membranes enriched in T tubules. Specific binding was reversible, trypsin-sensitive, maximal at pH 8, and stereoselective for the (3S,4R)-enantiomer of cromakalim. Potassium channel openers exhibited a rank order of potency of P1075 > pinacidil > levcromakalim = BMS-180448 > nicorandil > diazoxide = BRL 38226. Fluorescein analogs (ethyleosin, phloxine B, and rose bengal) were relatively potent inhibitors of binding (Ki = 200-300 nM). The potassium channel openers cromakalim and BMS-180448 were competitive inhibitors of [3H]P1075 binding. In contrast, rose bengal and the ATP-regulated potassium channel antagonist glyburide increased the rate of [3H]P1075 dissociation in a manner consistent with noncompetitive interaction.

Adenosine Triphosphate↗
PubMed1996

Accuracy of color doppler velocity in the flow field proximal to a regurgitant orifice: implications for color doppler quantitation of valvular incompetence.

Color Doppler is routinely used in estimates of valvular regurgitation. Velocity and subsequently flow measurements are made at about 7-10 cm from the ultrasonic transducer. Error in velocity measurement may occur due to spatial broadening of the color Doppler beam in the axial, azimuthal and lateral directions. Error in velocity may also occur due to wall filters since the filtering process is not uniform throughout the velocity range indicated by the color bar. An attempt to estimate this error was made using an in vitro orifice model, a numerical finite element model (FEM), and information from the manufacturer. We found that the acoustic beam spatial expansion, wall filter sensitivity and Nyquist limit (NYL) have to be considered simultaneously to account for errors. The combined spatial expansion and wall filter effect on velocity was estimated as a weighted average over the sample volume. The error distributions are not universal but depend on orifice size and flow. For a 3-mm orifice and 100 cm s NYL the overall effect was overestimation of low velocities and significant underestimation of high velocities due to the high velocity gradients inside the sample volume. For the 5- and the 10-mm orifice the effect was less accentuated. Based on this overall error distribution, a correction was incorporated on color Doppler obtained data. The incorporated correction yielded better agreement with numerical velocity data. This correction is important in the application of the proximal isovelocity surface area (PISA) technique and the evaluation of regurgitant flowrates.

Blood Flow Velocity↗
PubMed1996

A rare variant of mirror hand: a case report.

Mirror hand is one of the rarest congenital differences of the upper extremity. Typically, there is absence of the radius, duplication of the ulna, and 7 digits in mirrored symmetry about the middle finger. We report a case of a rarer subset of hand duplication in which there is a normal radius and ulna and a hand with 8 digits. The patient underwent surgery to excise the radial 3 digits and to reconstruct the remaining radial digit to function as an opposable, 2 phalanx thumb. Wrist extension was augmented by transferring the digital extensors from the excised fingers to the radial wrist extensors.

Hand Deformities↗
PubMed1996

Use of a neonatal noninvasive blood pressure module on adult patients.

A clinical and statistical comparison of systolic, mean and diastolic arterial blood pressures was made between a non-invasive technique using a neonatal oscillometric blood pressure monitor attached to the thumb versus an invasive technique using a catheter inserted into the ipsilateral radial artery in 18 patients undergoing general anaesthesia for major surgery. In 1258 readings, the mean differences between the pressures obtained (invasive versus non-invasive) were +9.1, -7.9, and -0.7 mmHg for systolic, diastolic and mean pressures respectively. Oscillometric blood pressure measurement using the thumb appears to be an acceptable method for monitoring blood pressure during anaesthesia and has advantages over conventional cuff placement on the upper arm.

Adult↗
PubMed1996

Are visual search procedures adapted to the nature of the script?

Letters are processed differently from other shapes in a visual search task where subjects have to decide whether or not a predesignated target symbol is present in a subsequently presented string of five such symbols. If the M-shaped letter search function, which relates correct reaction time to target position, reflects an efficient strategy used in word recognition, it should be produced by skilled readers of English who also read a logographic script. A cross-linguistic study of biscriptal Mandarin/English and monoscriptal English readers (Expt 1) provided evidence of the generality of a basic search strategy for alphabetic targets. Hand-of-response affected the search function in an asymmetric fashion for both groups of readers, and although case differences between target and string increased reaction times overall, the classic M-shaped function remained. In Expt 2, we used a within-subjects design and examined the extent to which biscriptal Mandarin/English readers produced different search functions for letters and logographs. Consistent with expectation, these readers showed an M-shaped function for letters but a more U-shaped function for logographs. Hand-of-response exerted a consistent effect for both types of material. Taken together, these experiments support the view that skilled readers develop script-specific procedures.

Adult↗