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Biomedical subjects

D G Hughes

Publications and source records attributed to D G Hughes.

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

MR imaging appearances of cervical epidural abscess.

Epidural abscess of the cervical spine is an uncommon disorder. The presentation is often non-specific and the diagnosis unsuspected. Magnetic resonance (MR) imaging is now considered the imaging investigation of choice. We report six patients with cervical epidural abscess diagnosed on MR imaging. The MR imaging showed the abscess to have a variable appearance and enhancement characteristics. Follow-up MR examinations confirmed resolution of the abscess and, in five cases, allowed conservative management.

Abscess↗
PubMed1994

Quantitative characterization of the eddy current fields in a 40-cm bore superconducting magnet.

The temporal and spatial dependence of the eddy current fields, generated by switching off x, y, and z gradients in a 40-cm bore Bruker superconducting magnet, have been studied by measuring the offset frequency of the proton FID obtained from a small spherical sample. The measurements were made with the pre-emphasis unit deactivated. The data obtained at each location were well fitted to a sum of four exponentially decaying components. The shortest decay is, in each case, associated with the decay of the current in the gradient coil itself, while the other decays are associated with three eddy currents with decay times ranging from 13 to 480 ms. Each of the three eddy currents generates an essentially uniform gradient for at least 4 cm on either side of the isocenter. However, when the eddy currents are generated by either the vertical transverse gradient or the longitudinal gradient, the eddy current gradients are also accompanied by a field shift.

Magnetic Resonance Imaging↗
PubMed1994

Influence of droperidol on nausea and vomiting during patient-controlled analgesia.

We have studied the addition of droperidol to morphine during patient-controlled analgesia (PCA) in 57 patients using PCA after abdominal hysterectomy. Patients in group 1 (control group) received placebo at induction of anaesthesia and a PCA containing morphine; those in group 2 received droperidol 1.25 mg and a PCA containing morphine and those in group 3 droperidol and a PCA containing droperidol 0.05 mg mg-1 of morphine. Patients in the control group suffered 51 episodes of nausea compared with 35 in the droperidol bolus group and 18 in the droperidol PCA group (P < 0.01). In the droperidol PCA group, only 10 doses of additional antiemetic therapy were required compared with 24 in the droperidol bolus group and 28 in the control group (P < 0.05). We did not observe side effects attributable to droperidol. We conclude that droperidol added to morphine in PCA reduces nausea and antiemetic requirements after abdominal hysterectomy.

Adult↗
PubMed1994

Technical note: the influence of using an atraumatic needle on the incidence of post-myelography headache.

The aim of this study was to investigate whether the incidence of headaches following myelography could be reduced by using a needle with an atraumatic tip. 107 patients were studied in a trial of 22 gauge atraumatic versus 22 gauge bevel tipped needles. In the first 3 days after myelography, there was a significant reduction in the incidence of headaches in patients in whom an atraumatic needle had been used.

Adult↗
PubMed1994

Comparison of hand injection with mechanical injection for digital subtraction selective cerebral angiography.

100 patients undergoing digital subtraction cerebral angiography were randomized to have contrast delivered by either hand or mechanical injection. We compared the two modes of injection for image quality, the presence of vertebral reflux, possible complications and radiation exposure to the radiologist. There was no statistical difference between the two modes of contrast delivery for image quality and vertebral reflux. Only one definite temporary neurological complication was recorded. However, radiation exposure to the radiologist's hand and body were reduced by up to 70% by using a mechanical injector for contrast delivery during selective cerebral angiography with digital subtraction. We advocate use of the mechanical injector by radiologists who perform regular angiography to reduce their exposure to radiation.

Adolescent↗
PubMed1993

Epidural anaesthesia through caudal catheters for inguinal herniotomies in awake ex-premature babies.

Ex-premature babies are at risk of apnoea after surgery. Regional anaesthesia has been used as an alternative to general anaesthesia for some surgical procedures in the belief that it may be safer. However, single dose caudal epidural and subarachnoid anaesthetics have a duration of action which may be insufficient for some operations. The level and duration of anaesthesia can be extended if local anaesthetic is given through an epidural catheter. In addition, the dose needed to provide adequate anaesthesia may be lower because the local anaesthetic is given at an appropriate segmental level. We report our experience of caudal epidural anaesthesia in nine, awake ex-premature babies who were having inguinal herniotomies. The anaesthesia was excellent in six babies. Two babies cried briefly with peritoneal or spermatic cord traction. One other baby needed supplementation with nitrous oxide in oxygen in order to complete the surgery. The majority of babies slept throughout surgery. There were no reported postoperative complications.

Anesthesia, Caudal↗
PubMed1992

Analysis of the temporal and spatial dependence of the eddy current fields in a 40-cm bore magnet.

Eddy current fields, generated in an animal-size superconducting NMR magnet by a nominally rectangular pulsed transverse gradient applied in the vertical direction, have been studied by measuring the offset frequency of the proton NMR signal obtained from a small spherical sample. Measurements were made, after various time delays, at nine different locations in the sample space. Analysis of the data shows that the time-dependent fields at all nine locations are quite well accounted for by the superposition of only four independent exponentially decaying components that have time constants in the range from 9 to 400 ms. Two of these were found to be caused by eddy currents generated in the magnet structure. They generate primarily linear gradients, though one of them also produces a B0 shift, indicating a significant asymmetry about the isocenter of the conducting structure in which the eddy current flows. The other two exponentially decaying components, which had very different time constants from the eddy currents and also initial amplitudes of the opposite sign, were generated by the preemphasis unit. This calls into question the procedure used to adjust the preemphasis unit and an alternative method is proposed.

Artifacts↗
PubMed1992

Intensity artifacts in MRI caused by gradient switching in an animal-size NMR magnet.

The switching of magnetic field gradients in MRI gives rise to eddy currents in the structural components of superconducting magnet systems. The associated magnetic fields cause intensity artifacts which are particularly severe in some animal-size systems. We treat theoretically three mechanisms which cause intensity artifacts in one-dimensional projection images obtained by a spin-echo technique. The first is an off-resonance effect, caused by applying the refocusing pulse before the read compensation gradient pulse has decayed sufficiently. The other two mechanisms are caused by a spatial dependence of the phase accumulated by the spins at the time of formation of the echo, as a result of the eddy current fields. First, interference causes a loss of transverse magnetization because of a variation in the phase of spins which lie on the same isochromat during the read gradient pulse. Second, a variation of the phase of the spins in a direction orthogonal to the isochromats causes spins throughout the sample to refocus at different times. These two mechanisms are fundamentally different, since interference can occur even if the main magnetic field is homogeneous, whereas improper refocusing does not. It is shown that there is no loss of intensity by the interference mechanism if phase encoding is used to form two-dimensional images. This may well be a major reason why images obtained by 2DFT have been found to be generally superior to those obtained by projection reconstruction. Experimentally, the distribution of intensity in one-dimensional projection images of a square slice phantom is compared with theoretical intensities, estimated using eddy current field reported in the preceding paper.

Artifacts↗
PubMed1992

How frequent is chronic lumbar arachnoiditis following intrathecal Myodil?

Chronic lumbar arachnoiditis has numerous causes, including the introduction of contrast media into the lumbar subarachnoid space. The oily contrast medium Myodil (iophendylate) is often cited but the true incidence of symptomatic lumbar arachnoiditis due solely to the presence of Myodil is unknown. A retrospective review of 98 patients in whom Myodil was introduced by ventriculography or cisternography, i.e. remote from the lumbar spine, revealed no cases of chronic lumbar arachnoiditis. All patients were monitored closely for periods ranging from 1 to 28 years. We conclude that, in these circumstances, it is rare for Myodil to produce symptomatic arachnoiditis.

Adult↗
PubMed1990

Obstetric anaesthesia in dystrophia myotonica.

Two patients with dystrophia myotonica presented for urgent Caesarean section. Their per- and postoperative courses illustrate the anaesthetic problems posed by this disease. Respiratory difficulties are compounded by pregnancy and there is increased susceptibility to uterine haemorrhage. Choice of anaesthetic agent is discussed. Both had general anaesthetics; muscle relaxation was achieved with vecuronium.

Adult↗
PubMed1989

Cardiovascular effects of H2-receptor antagonists.

The type II histamine receptor antagonists, cimetidine and ranitidine, widely used in treatment of peptic ulcer disease have been reported to cause bradycardia. To evaluate the cardiovascular effects of H2 antagonists nineteen healthy volunteers were entered into a double-blind crossover comparison of cimetidine 300 mg qid, ranitidine 150 mg bid, and placebo. Subjects ingested study medicine for 7 days prior to being tested by the Bruce Exercise Test. Heart rate, blood pressure, oxygen consumption, expiratory volume, and fractional expiration of CO2 and O2 were measured at rest, exercise and recovery. A plasma sample for determination of cimetidine and ranitidine levels were obtained prior to the exercise period. Multivariate analysis and paired t test revealed no significant differences for the cardiovascular or pulmonary variables. However, in 5 subjects, the heart rate at 25% maximum VO2 was depressed 8% (P less than or equal to 0.03). This effect in a small percentage of the population suggests that further studies are needed to determine if subpopulations are affected.

Adult↗
PubMed1988

Skeletal hyperostosis and extraosseous calcification in patients receiving long-term etretinate (Tigason).

In an ongoing study of patients on long-term etretinate (Tigason) therapy, 13 patients with a congenital or inherited disorder of keratinization and 10 patients with psoriasis were examined to investigate the incidence of, and the factors associated with, skeletal hyperostosis. Skeletal scintigraphy, plain radiographs, haematological and biochemical analyses were performed. Using all criteria, 7 of 13 patients with a congenital or inherited disorder of keratinization showed evidence of hyperostosis. No single investigation was able to detect all these cases; in particular, skeletal scintigraphy was positive in only nine of the 13 patients who showed hyperostosis. Eleven of the 13 patients with hyperostosis gave a history of musculoskeletal symptoms compared with three of the 10 patients without hyperostosis. There was no clear association with total dose or duration of treatment. Serum chemistry and haematological studies were normal. In two patients the 24-h urinary calcium excretion was significantly elevated, an abnormality which has not been described previously. Annual lateral thoracic spine radiographs with additional views of symptomatic areas are recommended for patients on long-term etretinate therapy.

Adult↗
PubMed1987

Clinical assessment of the neonatal Dinamap 847 during anesthesia in neonates and infants.

Direct measurements of systolic, diastolic, and mean arterial blood pressure and electrocardiogram-derived heart rates were compared with indirect arterial blood pressure measurements using the Dinamap 847XT noninvasive monitor. A total of 260 paired comparisons from 16 patients were analyzed. A regression analysis of paired data over a wide range of blood pressure values gave the following results: for heart rate r = 0.97, for systolic arterial pressure r = 0.84, for mean arterial pressure r = 0.73, and for diastolic arterial pressure r = 0.52. The 95% confidence limits for systolic, mean, and diastolic arterial pressure were +/- 16 mm Hg, +/- 18 mm Hg, and +/- 21 mm Hg, respectively. The Dinamap monitor was found to be an accurate trend recorder of heart rate and blood pressure during anesthesia in neonates and small infants.

Anesthesia, General↗