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Biomedical subjects

S Bower

Publications and source records attributed to S Bower.

At least 55 records · Page 3Linked to original sources
PubMed1994

Fetal hyperechogenic bowel following intra-amniotic bleeding.

OBJECTIVE: To test the hypothesis that increased echogenicity of the fetal bowel at second-trimester scans results from intra-amniotic bleeding. METHODS: We studied 726 patients undergoing second-trimester amniocentesis for advanced maternal age. Three groups were identified according to the color of the amniotic fluid (AF) obtained: clear fluid, blood-stained fluid, and dark brown fluid. Two to 4 weeks after the amniocentesis, all patients had a targeted ultrasound examination for the detection of fetal structural anomalies and markers of chromosomal abnormalities, which included a survey of the fetal bowel. The incidence of hyperechogenic bowel in each group was compared by Fisher exact test. P < .05 was considered significant. RESULTS: In 694 cases, the AF was clear (95%), in 20 blood-stained (3%), and in 12 dark brown (2%). Hyperechogenic bowel was detected in 14 fetuses with clear fluid (2%), in two with blood-stained fluid (10%), and in three with dark brown fluid (25%). Fetuses with proven intra-amniotic bleeding (ie, dark brown or blood-stained AF at amniocentesis) had a significantly higher incidence of hyperechogenic bowel compared to those with clear AF (five of 32 [15.6%] and 14 of 694 [2.0%], respectively; P < .001, 95% confidence interval for the difference in proportions 6.3-17.6%). CONCLUSIONS: Our study demonstrates that intra-amniotic bleeding is associated with an increased incidence of fetal hyperechogenic bowel at second-trimester ultrasound scans. This sonographic phenomenon may be due to the presence of blood in the fetal bowel caused by fetal swallowing of bloody AF.

Amniocentesis↗
PubMed1994

Long-term prognosis of transient lone bilateral blindness in adolescents and young adults.

We describe a group of 14 patients aged 8-38 years at presentation who had one or more sudden transient attacks of bilateral blindness. Eight patients described bilateral blindness as their only symptom whereas six others experienced some mild associated symptoms. Visual loss always developed within seconds and attacks were often precipitated by exercise, stress, or postural change. Of 13 patients available for review, none suffered a major vascular event during a mean follow up of 10 years. When adolescents and young adults present with transient bilateral blindness, investigations are unlikely to reveal a cause and the long-term prognosis appears benign.

Adolescent↗
PubMed1993

Doppler ultrasound screening as part of routine antenatal scanning: prediction of pre-eclampsia and intrauterine growth retardation.

OBJECTIVE: To assess the value of incorporating continuous wave Doppler ultrasound of the uterine arteries into the routine scan as a screening test in an unselected population. DESIGN: A cross sectional study by multiple operators using continuous wave Doppler ultrasound to obtain flow velocity waveforms (FVW) from both uterine arteries of all women attending for routine anomaly scan at 18 to 22 weeks over a period of 12 months. An abnormal FVW in either uterine artery was used to predict intrauterine death, antepartum haemorrhage and three different degrees of severity of pre-eclampsia and growth retardation, singly and in combination. SETTING: King's College Hospital, London. SUBJECTS: Two thousand, four hundred and thirty women attending for routine anomaly ultrasound scan. RESULTS: A total of 2430 women were scanned with a 90% follow up rate. The results demonstrate higher sensitivities than previous studies, but with a high proportion of false positive tests. By including an early diastolic notch in the definition of an abnormal FVW the prediction of pre-eclampsia is markedly improved; the relative risk to a woman with an abnormal waveform of developing moderate or severe pre-eclampsia is increased 24-fold. Although the positive predictive value for babies less than the 5th centile for gestation is only 15%, those at risk of neonatal complications may be identified. CONCLUSION: This simple test can be performed at a routine visit and a group of women can be identified for further assessment and possible therapeutic intervention.

Blood Flow Velocity↗
PubMed1993

Antiplatelet and anticoagulant therapy.

Antiplatelet therapy is clearly indicated for long-term secondary prevention after transient ischemic attack and ischemic stroke. In stroke-free patients with atrial fibrillation, oral anticoagulants reduce the risk of stroke, and antiplatelet agents may be a lower risk alternative. For the early treatment of the acute phase of ischemic stroke, the role of antiplatelet and anticoagulant therapy is unclear, but is being evaluated in large clinical trials.

Aspirin↗
PubMed1993

Improved prediction of preeclampsia by two-stage screening of uterine arteries using the early diastolic notch and color Doppler imaging.

OBJECTIVE: To assess the value of the early diastolic notch and color Doppler imaging of the uterine arteries at 24 weeks' gestation in a two-stage Doppler screening test for preeclampsia. METHODS: Two thousand fifty-eight unselected women had an initial screening study with continuous-wave Doppler at 18-22 weeks' gestation. Color Doppler imaging was used at 24 weeks' gestation to examine both uterine arteries in 273 women with initial abnormal results (high resistance index or diastolic notch). RESULTS: Three hundred twenty-nine women (16%) had abnormal flow velocity waveforms at the first stage and 104 (5.1%) at the second stage of Doppler screening. The presence of an early diastolic notch in the flow velocity waveform was significantly better than a high resistance index at predicting preeclampsia at both 20 and 24 weeks; the relative risk of developing significant preeclampsia for a woman with a persistent notch at 24 weeks was increased 68-fold. All women delivered before 34 weeks because of severe preeclampsia had abnormal waveforms at both stages of screening. CONCLUSION: An early diastolic notch in the flow velocity waveform is a better predictor of preeclampsia than are conventional impedance indices. Preeclampsia can be predicted effectively by two-stage Doppler screening.

Adult↗
PubMed1992

Color Doppler imaging of the uterine artery in pregnancy: normal ranges of impedance to blood flow, mean velocity and volume of flow.

In a cross-sectional study of 215 healthy women with singleton pregnancies at 18-42 weeks' gestation, color Doppler imaging was used to identify the main uterine arteries for subsequent pulsed Doppler studies. Flow velocity waveforms were obtained and indices of impedance, mean blood velocity and vessel diameter were measured, and the total volume of blood flow to the uterus was calculated. Impedance to flow decreased, I whereas blood velocity and volume flow increased significantly with gestation. Furthermore, impedance to flow was lower and velocity higher in the placental uterine artery, i.e. closest to the main bulk of the placenta, than in the non-placental artery.

Journal Article↗
PubMed1992

Effects of different hepatic pathologies on disposition of alfentanil in anaesthetized patients.

We have studied the influence of different hepatic pathologies on the disposition of alfentanil in 23 unpremedicated patients (six healthy control subjects, six patients with liver dysfunction of alcoholic aetiology and 11 patients with non-alcohol related liver disease). All patients received a bolus of alfentanil 500 micrograms i.v. as supplement to 67% nitrous oxide and isoflurane in oxygen anaesthesia. Plasma drug concentrations were measured in venous blood samples at intervals up to 24 h by radio-immunoassay and protein binding was determined by equilibrium dialysis. Kinetic estimates were determined using non-compartmental analysis. Patients with non-alcoholic liver disease had lesser plasma clearance (114.8 (range 66.8-213.5) ml min-1) than the alcoholic group (158.8 (100.0-220.7) ml min-1) or controls (187.4 (125.2-269.5) ml min-1). In all three groups, there was considerable intersubject variability, with a bimodal distribution in the non-alcoholic group. This group also had a smaller apparent volume of distribution at steady state. Mean residence time was prolonged in the alcoholic group compared with controls (284.9 (217.8-362.2) min vs 226.8 (201.2-250) min). Protein binding was decreased in the alcoholic group compared with controls (84.9 (SD 4.2)% vs 89.3 (2.1)%); this was attributable to a lesser plasma alpha 1-acid glycoprotein concentration (0.55 (0.18) g litre-1 vs 0.89 (0.21) g litre-1). Free drug clearance was reduced in both liver dysfunction groups compared with controls.

Adult↗
PubMed1991

Braxton-Hicks contractions can alter uteroplacental perfusion.

Color flow imaging was used to study the effect of spontaneous low-amplitude uterine contractions (Braxton-Hicks) on flow velocity waveforms obtained from the main uterine artery in 13 women between 26 and 34 weeks' gestation. Eight women had abnormal waveforms, as defined by the presence of an early diastolic notch, and five women had normal waveforms. In the former group, three women with chronic hypertension were started on the calcium antagonist nifedipine during this study. Contractions, which were monitored by external tocography, occurred more frequently in the group with abnormal waveforms and were temporally associated with an increase in impedance to blood flow. This effect occurred to the same degree in both normal and abnormal groups, but in the abnormal group the already impaired blood flow to the intervillous space was further diminished, resulting in absence of forward flow in diastole. Such acute reductions of flow in response to frequent, impalpable uterine contractions may cause a prolonged and silent insult to uteroplacental perfusion, which could hasten fetal compromise. This effect appeared to be abolished in patients on nifedipine, suggesting a possible therapeutic role for this drug in uteroplacental insufficiency.

Journal Article↗
PubMed1991

Plasma concentrations of bupivacaine following combined sciatic and femoral 3 in 1 nerve blocks in open knee surgery.

We administered combined femoral 3 in 1 and sciatic nerve blocks to provide postoperative pain relief in 22 consecutive patients undergoing elective knee replacement surgery under spinal anaesthesia. The patients were allocated randomly to two groups. In group A (n = 11) the blocks were performed with 0.5% bupivacaine (with adrenaline) 3 mg/kg body weight and in group B (n = 11) 0.5% plain bupivacaine in the same dose was used. Serial plasma concentrations of bupivacaine were measured for up to 2 h and the duration of postoperative analgesia was measured in both groups. No significant differences were found between the two groups. There were no clinical signs or symptoms of bupivacaine toxicity in each group. This study demonstrated that, after combined sciatic and 3 in 1 femoral block, concentrations of bupivacaine associated with toxicity were not reached, even though the dose of bupivacaine administered exceeded the manufacturer's recommended dose by 50%.

Anesthesia, Spinal↗
PubMed1991

Doppler velocimetry studies of the uterine artery in the early prediction of pre-eclampsia and intra-uterine growth retardation.

Pre-eclampsia/proteinuric pregnancy-induced hypertension (PPIH) and intra-uterine growth retardation (IUGR) are associated with incomplete trophoblastic invasion of the uterus in the first half of pregnancy. The uteroplacental circulation can be observed using Doppler ultrasound. We have performed two mid pregnancy screening studies of our antenatal population in the last three years, to assess the use of Doppler velocimetry studies at that time in predicting the subsequent development of PPIH and IUGR. In the first study continuous wave Doppler ultrasound was used to study the uterine circulation. The Resistance Index (RI) was measured once in both uterine arteries in 925 patients between 16 and 24 weeks gestation. There was a significant association between an abnormal RI (greater than 95th centile) and the subsequent development of PPIH, IUGR and severe complications of pregnancy. However, even though the specificity (95%) was high the sensitivity was low (25%). There was no significant association with nonproteinuric hypertension. In an attempt to improve the sensitivity for the second study, colour flow imaging and the use of a diastolic notch as well as an elevated RI were introduced. 2437 patients had continuous-wave Doppler studies of the uterine circulation performed at 20 weeks gestation. 16% had abnormal waveforms, persisting in 5.4% at 24 weeks and 4.6% at 26 weeks when measured with colour/pulsed Doppler. The high sensitivity (76%) of this innovation at 20 weeks is retained at 24 and 26 weeks, while the specificity (from 86% to 97%) and positive predictive value (13% to 44%) improve progressively with gestation.(ABSTRACT TRUNCATED AT 250 WORDS)

Arteries↗
PubMed1990

Middle cerebral artery flow velocity waveforms in fetal hypoxaemia.

In 81 small-for-gestational age fetuses (SGA) colour flow imaging was used to identify the fetal middle cerebral artery for subsequent pulsed Doppler studies. Impedence to flow (pulsatility index; PI) was significantly lower, and mean blood velocity was significantly higher, than the respective reference ranges with gestation. Fetal blood sampling by cordocentesis was performed in all SGA fetuses and a significant quadratic relation was found between fetal hypoxaemia and the degree of reduction in the PI of FVWs from the fetal middle cerebral artery. Thus, maximum reduction in PI is reached when the fetal PO2 is 2-4 SD below the normal mean for gestation. When the oxygen deficit is greater there is a tendency for the PI to rise, and this presumably reflects the development of brain oedema.

Blood Flow Velocity↗
PubMed1989

Disposition of alfentanil in patients receiving a renal transplant.

The disposition of alfentanil has been investigated in 10 anaesthetized patients with chronic renal failure undergoing kidney transplantation and compared with eight age matched anaesthetized patients with normal renal function. Plasma samples were collected to 660 min following intravenous administration of alfentanil 3-5 mg (50 micrograms kg-1). Drug concentrations were measured by RIA; and alfentanil binding to plasma proteins by equilibrium dialysis against 0.1 M phosphate buffer, pH 7.4. Alfentanil binding to plasma proteins was 87.6% (s.d. 2.0) in the patients with chronic renal failure, and 89.7% (1.2) in patients with normal renal function (P = 0.025). There was no correlation between alfentanil binding and plasma albumin, total plasma proteins, plasma urea or plasma creatinine concentrations. In both groups, the drug concentration-time profile decayed in a curvilinear manner; in the chronic renal failure patients, restoration of function did not influence the decay profile. Elimination half life, mean residence time and apparent volume of distribution at steady state were not different in the two groups of patients (mean values: 142.4 and 120.2 min; 128.5 and 136.0 min; and 40.5 and 27.6 L, respectively in chronic renal failure patients and patients with normal renal function). Total drug clearance and Vd area were significantly increased in the chronic renal failure patients: 341.9 vs 211.8 mL min-1; and 69.3 and 35.5 L. There were no differences in intrinsic clearance or apparent volume of distribution at steady state for unbound drug between the two patient groups.

Adult↗
PubMed1988

The pharmacokinetics and clinical effects of a low dose of alfentanil in elderly patients.

Alfentanil is a potent short-acting opioid analgesic which depresses respiration and can cause cardiovascular depression. The elderly can show greater sensitivity to opioid drugs which may be related to pharmacokinetic differences. The pharmacokinetics and clinical effects of alfentanil were studied in 10 elderly patients aged 68-86 years who were undergoing cystoscopy or urethrotomy under general anesthesia. After induction with thiopentone, and while the patient was breathing nitrous oxide with halothane 0.5% (enflurane 1.0% was given to one patient), a dose of alfentanil 4 micrograms/kg was given 15, 20, 30, 45 and 60 minutes after the alfentanil administration, and then every 30 minutes for 6 hours. Pulse rate (PR), systolic blood pressure (SBP), and minute volume (MV, calculated from the respiratory rate and the tidal volume) were measured at 1, 3, 5, 7 and 9 minutes after the alfentanil injection. Pharmacokinetic analysis showed Vc 82 (+/- S.D. 26) ml/kg; VDSS 277 (+/- S.D. 71) ml/kg; clearance 2.01 (+/- S.D. 0.64) ml/kg/min; t1/2 beta 117 (+/- S.D. 24) min. Comparison of these results with the results of other studies supports the view that older patients eliminate alfentanil less rapidly than younger patients, with prolongation of t1/2 beta and decreased clearance. The clinical results showed a decrease in minute volume from a mean value of 5944 ml before alfentanil to 1240 ml 1 minute after alfentanil (P less than 0.001). The minute volume was still significantly lower at 3 and 5 minutes, but had returned to the pre-alfentanil value by 7 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗