Biomedical subjects

N D Pugh

Publications and source records attributed to N D Pugh.

17 recordsLinked to original sources

PubMed1997

Follicular vascularity--the predictive value of transvaginal power Doppler ultrasonography in an in-vitro fertilization programme: a preliminary study.

The aim of this prospective study was to investigate the ability of transvaginal power Doppler ultrasonography to assess the relationship between follicular vascularity and outcome in women undergoing in-vitro fertilization. Each of 38 subjects underwent a single transvaginal power Doppler ultrasound scan on the day of oocyte collection, where the vascularity of individual ovarian follicles was assessed, using a subjective system, and graded 1 to 4. In addition, conventional pulsatility indices (PI) of the uterine and intra-ovarian (stromal) arteries were calculated, which showed no significant differences between the pregnant and non-pregnant groups. Using power Doppler ultrasonography, a total of 188 follicles was studied. The follicular vascularity grade was found to be independent of follicular size and there was no significant difference in fertilization rates with different degrees of vascularity, although there was a trend towards higher fertilization rates with higher grade vascularity. There were 10 pregnancies, giving a pregnancy rate of 26.3% per embryo transfer. Pregnancies were confined to those women whose embryos were derived from follicles with grade 3 and 4 vascularity (pregnancy rates per embryo transfer of 12.5 and 61.5% respectively), with only those from grade 4 follicles resulting in livebirths. This preliminary study suggested that high grade follicular vascularity is associated with increased pregnancy rate and that there is a possible link between follicular vascularity and implantation potential.

Adult↗

PubMed1996

Haemodynamic and rheological effects of contrast media: the role of viscosity and osmolality.

All currently available iodinated contrast media (CM) produce some form of haemodynamic or rheological change when injected. These effects are thought to be due primarily to the osmolality and viscosity of the CM. The new hexa-iodinated contrast agent Visipaque has the advantage of being iso-osmotic with blood at all clinically relevant concentrations, but is more viscous than the monomers at equivalent iodine concentrations. The purpose of this review is to discuss the relative importance of osmolality and viscosity in the clinical situation.

Animals↗

PubMed1996

Duplication of the superficial femoral vein: recognition with duplex ultrasonography.

Duplication of the superficial femoral vein (SFV) is a normal variant seen in 20% of contrast phlebograms. Failure to identify thrombus in one limb of a SFV may lead to inappropriate management and subsequent complications. Colour Doppler imaging (CDI) is now the imaging technique of choice in the diagnosis of a deep vein thrombosis (DVT). The purpose of this study was to identify the prevalence of duplication of the SFV at CDI and to compare this with the known prevalence at contrast phlebography. CDI was performed on 58 healthy volunteers (116 limbs examined). Duplication of the SFV was present in 29 examinations (25%). Ultrasonic measurement of the diameter of the SFV was performed in all patients. In the presence of duplication a significant reduction in the diameter of both limbs of the SFV was noted when compared with an unduplicated vessel. The prevalence of duplication of the SFV at CDI is comparable to that at contrast phlebography. Recognition of this variant may help reduce false negative CDI examinations.

Adult↗

PubMed1995

Carotid artery duplex scanning: does plaque echogenicity correlate with patient symptoms?

In this study we have investigated the relationship between plaque sonolucency and ipsilateral hemispheric symptoms in 116 patients at risk of cerebrovascular disease (75 symptomatic patients, 41 asymptomatic patients). Our results indicate that plaque sonolucency is significantly associated with the incidence of patient symptoms at presentation. Twice as many symptomatic vessels contained the predominantly sonolucent plaque types (types 1 and 2) compared to contralateral asymptomatic vessels (p = 0.039, odds ratio = 2.9). Vessel stenosis also had a significant association with patient symptoms. No significant interaction was shown between vessel stenosis and plaque sonolucency (p = 0.15, odds ratio = 1.0). A model using vessel stenosis and plaque echogenicity as independent variables showed that degree of vessel stenosis had a closer association with incidence of symptoms (p = 0.03, odds ratio = 1.04) than plaque type (p = 0.13, odds ratio = 0.51).

Aged↗

PubMed1995

Effects of iodinated contrast media on peripheral blood flow.

All types of clinically employed iodinated roentgen contrast media (CM) cause vasodilatation after i.a. and i.v. administration, regardless of precise molecular structure. It is now apparent, however, that at iodine concentrations which provide equivalent angiographic contrast, this is significantly less with newer hexa-iodinated dimers, such as iodixanol and iotrolan, than older generations of compounds. The cellular mechanisms that underly the vasodilator effects of CM still remain to be fully elucidated but may include a) effects attributable to hyperosmolality; b) stimulation of the release of endogenous vasoactive mediators; and c) direct relaxant effects upon vascular smooth muscle. This review will discuss the possible contributions of these mechanisms to the vasodilatation observed in the clinical situation.

Animals↗

PubMed1995

Angiographic contrast media relax isolated rabbit aorta through an endothelium-independent mechanism that may not depend on the presence of the iodine atom.

Systemically administered iodinated angiographic contrast media evoke vasodilatation through mechanisms that are at present poorly understood. In the current investigation we have evaluated the role of the vascular endothelium in responses to an iso-osmolar formation of the non-ionic dimer iodixanol and a hyperosmolar formulation of the non-ionic monomer iopromide. Isolated rabbit aortic ring preparations with endothelium intact or removed by gentle abrasion were mounted in organ baths containing oxygenated Holman's solution, and cumulative concentration-response curves for relaxation to the contrast media were constructed after pre-constriction by phenylephrine (300 nM) in the presence of indomethacin to inhibit prostaglandin synthesis. Endothelial denudation did not influence the ability of either iodixanol or iopromide to relax the aortic ring preparations. Iopromide was significantly more potent than iodixanol when expressed in terms of iodine concentration (mg I ml-1), but both agents were equipotent when expressed in terms of molarity (mM). We conclude that relaxation of isolated rabbit aortic rings to iodixanol and iopromide under conditions where there is no fluid flow is endothelium-independent, and therefore not mediated by release of the potent endogeneous nitrovasodilator endothelium-derived relaxing factor (EDRF). Furthermore, their relaxant activity under the in vitro experimental conditions employed is attributable to a direct action on vascular smooth muscle by factors in addition to osmolality, and may depend on features that are not specifically associated with the presence of the iodine atom.

Angiography↗

PubMed1995

Stress, steroids, and "ojas": neuroendocrine mechanisms and current promise of ancient approaches to disease prevention.

Recent research on causes of disease and aging has increasingly supported the importance of stress. One theory of the relationship between stress and disease is based on the concept of homeostasis, a term coined by Cannon over 50 years ago to signify those states and mechanisms responsible for the "staying power of the body". Bernard, Cannon, Selye and other leading researchers held that full, normal function of the self-regulating or homeostatic power of the body maintains the balanced, integrated condition we recognize as health. Failures in this capacity, such as those produced by frequent stressful experiences, can result in disease or death. Theories of health and disease surprisingly similar to this have existed since ancient times, and in widely different cultures. This review discusses both the fundamental elements of these theories and the current neuroendocrine research supporting their validity and immediate relevance. The connections between ancient and modern knowledge described herein were made possible largely by the work of Maharishi Mahesh Yogi, a scholar and teacher of the ancient vedic tradition of India. A key part of Ayurveda that has been obscure to modern science is the substance "ojas", which the classical texts say maintains balance of the physiology. In this article, specific steroids or steroid classes are proposed as likely candidates for both the "ordinary" and the "superior" types of ojas described in Ayurveda. Current evidence for the functions of these steroids, as well as their role in stress, disease and the maintenance of health, is reviewed. The knowledge of Ayurveda, as recently brought to light by Maharishi, includes methods for recovering and maintaining optimal function of steroidal systems. Such effects may help mediate the improvements in health and increased longevity attributed to Ayurveda and other ancient methods.

Aging↗

PubMed1993

Iodixanol in femoral arteriography (phase III): a comparative double-blind parallel trial between iodixanol and iopromide.

Iodixanol is a new non-ionic, dimeric contrast medium (CM) which is formulated to be isotonic with blood in all clinically relevant concentrations. This is a report of a parallel, double-blind study comparing the safety and efficacy of iodixanol with iopromide (Ultravist) in aortofemoral arteriography. One hundred consecutive, eligible patients scheduled to undergo peripheral arteriography were entered into the study and randomly allocated to receive one or other CM. Radiographic quality, discomfort, adverse events, femoral blood flow and renal function were examined. Ninety-five patients were successfully included in the study. Radiographic quality (efficacy) was found to be similar in both groups. Three patients (6%) in the iodixanol group and five patients (11%) in the iopromide group reported adverse events. In this respect there was no statistically significant difference between the two groups (P = 0.48), and all adverse events were mild and transient. Forty-six (97%) patients in the iodixanol group and 45 (100%) patients in the iopromide group experienced a sensation of warmth (discomfort) in connection with one or more of the injections. There was no statistically significant difference in the frequency of discomfort in the two groups. However, the intensity of warmth was significantly milder following iodixanol than after iopromide (P = 0.003, two-sided Mantel-Haenszel test). The mean percentage increase in femoral blood flow was found to be less with iodixanol (43.4%) than with iopromide (96.3%) (P < 0.05, Student's t-test). Renal function was affected slightly after administration of both CM. Serum creatinine and creatinine clearance were affected more by iodixanol than by iopromide, while the excretion of tubular enzymes was more affected by iopromide. In conclusion, this comparison between iodixanol and iopromide showed both contrast media to be safe, effective and well tolerated and the only major difference between them was in their effect on femoral blood flow.

Aged↗

PubMed1992

The effect of iodixanol, a new isotonic contrast agent, on femoral blood flow in man.

Both ionic and non-ionic contrast media (CM) injected intra-arterially produce peripheral vasodilatation and a sensation of heat or even pain. This effect has been considered to be predominantly related to the osmolality of the CM used. Iodixanol is a non-ionic dimeric CM which can be made isotonic with blood at iodine concentrations up to 400 mg/ml. To assess the degree of peripheral vasodilatation following aortic injection of iodixanol, the change in femoral artery blood flow has been assessed non-invasively. Dupex ultrasound flow-velocity records were taken from the contralateral femoral artery in 10 patients undergoing transfemoral aortography. Volume flow, mean velocity, pulsatility index and peak systolic velocity were continuously recorded before and up to 2 min after injection of 60 ml of iodixanol at an iodine concentration of 320 mg/ml (iodixanol 320). Transient changes consistent with vasodilatation were observed in all patients. The greatest changes were observed during the time period 18-24 s after injection. Volume flow, mean velocity and pulsatility index all changed significantly from baseline (mean changes of 80.6%, 73% and -42.7% respectively). Peak systolic velocity did not change significantly. Intra-arterial injections of isotonic iodixanol 320 produces a significant increase in femoral blood flow in man. Factors other than hypertonicity must therefore be implicated in the vasodilatory effect of contrast media.

Adult↗

PubMed1992

Salivary gland tumours: is colour Doppler imaging of added value in their preoperative assessment?

Using a Toshiba SSA-270A Colour Duplex Scanner, 15 patients with suspected parotid and submandibular gland tumours had preoperative duplex scanning done. Peak systolic doppler shifts (fmax) were recorded and their vascularity was also subjectively scored. There were no arteries identified within the substance of contralateral normal glands. All recordings were analysed retrospectively and an independent histological assessment of tumours was made. Pleomorphic adenomas (n = 9) had a median peak systolic frequency (fmax) of 0.8 kHz, while adenolymphomas (n = 4) had a fmax of 1.65 and the two malignant tumours had fmax of 4.5 (P = 0.007 Kruskal-Wallis test). There appears to be a strong correlation between the fmax and the subjective vascular score (Corr 0.92). Colour duplex scanning is a non-invasive procedure which may be of help in the preoperative assessment of salivary gland tumours.

Adenolymphoma↗

PubMed1990

Temporal instabilities associated with a planar high purity germanium detector.

Experiments have been performed which show that a grooved planar high purity germanium semiconductor detector may give rise to time variant counting rates in energy regions below prominent spectral peaks. It is postulated that this effect is due to prolonged or incomplete charge collection in the vicinity of the bottom of the groove, and is caused by distortions in the applied electric field in this region. Such effects may lead to changes in the minimum detectable count rate in x-ray fluorescence measurements; these can be reduced by collimating incident photons on the central region of the detector but the resulting reduction in efficiency lowers the overall sensitivity.

Radiometry↗

PubMed1987

Effects of atracurium and vecuronium on the latency and the duration of the negative deflection of the evoked compound action potential of the adductor pollicis.

The effect of atracurium or vecuronium on the depolarization phase of the evoked compound action potential of the adductor pollicis has been investigated in 30 adult patients. Patients were studied using single supramaximal stimulation of the ulnar nerve at the wrist. The evoked compound action potential was measured over the adductor pollicis muscle. When blockade by atracurium exceeded 80%, a significant decrease in latency was recorded (P less than 0.05). There was no significant change in latency after vecuronium. During the onset of blockade, depression of the amplitude of the evoked compound action potential was associated with a prolongation of its duration (P less than 0.05). The mean maximum increase in the negative deflection time was found to be similar after atracurium and after vecuronium. However, this phase was prolonged to a greater extent for a given degree of amplitude depression during the onset of blockade by atracurium (P less than 0.05).

Action Potentials↗

PubMed1987

Changes in the power spectrum of the evoked compound action potential of the adductor pollicis with the onset of neuromuscular blockade.

The effects of neuromuscular blockade by atracurium and vecuronium on the power spectrum of the evoked compound action potential (ECAP) of the adductor pollicis were investigated in 30 adult patients undergoing elective surgery. The changes in amplitude and mean power frequency (MPF) of the ECAP were measured. Ten patients received an ED95 (0.23 mg kg-1) of atracurium and 10 received an ED95 (0.055 mg kg-1) of vecuronium. The remaining 10 patients did not receive any neuromuscular blocking drug, and were monitored for 6 min to exclude any time-related changes in the ECAP. Neuromuscular blockade produced a decrease in total power and a shift towards lower frequencies. This was reflected in a decrease in the MPF in those patients receiving atracurium or vecuronium. There was no significant difference (P less than 0.05) between the atracurium and vecuronium groups in the magnitude of the change in MPF. These findings suggest that the previously reported increase in the duration of the negative deflection of the ECAP is predominantly the result of a change in its frequency components.

Action Potentials↗

PubMed1986

Atracurium and vecuronium: effect of dose on the time of onset.

The time intervals measured from the administration of either atracurium or vecuronium to maximum or 95% neuromuscular blockade (Tmax) were compared in 70 patients using the evoked compound action potential of the adductor pollicis muscle. Equipotent doses, calculated from the relationship between dose and response for both drugs obtained in an earlier study, were compared. The doses of atracurium and vecuronium ranged from 0.135 to 0.5 mg kg-1 and from 0.02 to 0.1 mg kg-1, respectively. The dose range for both drugs included the ED50, ED95 and the dose required to produce 100% blockade (ED"100"). No significant changes in mean Tmax occurred for doses of atracurium in the range 0.135-0.2 mg kg-1 and in the range 0.24-0.5 mg kg-1. Similarly, no change in Tmax occurred at doses of vecuronium in the range 0.02-0.05 mg kg-1 and 0.06-0.1 mg kg-1. Tmax changed significantly in the dose ranges atracurium 0.2-0.24 mg kg-1 and vecuronium 0.05-0.06 mg kg-1. There was no significant difference in Tmax when equipotent doses of atracurium and vecuronium were compared.

Adolescent↗

PubMed1985

Neuromuscular block: atracurium and vecuronium compared and combined.

The neuromuscular blocking action of atracurium and vecuronium acting separately and in combination have been compared using the evoked EMG of the adductor pollicis muscle. Dose response curves have been drawn for the drugs given separately and found to be nonparallel (P less than 0.05). Atracurium was calculated to be 5.25 and 4.1 times less potent than vecuronium, ED50 and ED95 respectively. The effect on neuromuscular transmission of a combined medication using equipotent doses of atracurium and vecuronium, determined from the dose response plots, was found to be greater than would be expected by addition of their separate actions. The combination of small doses resulted in significant neuromuscular blockade.

Anesthesia, General↗

PubMed1984

Myasthenia gravis and atracurium. A case report.

The degree, duration of and recovery from neuromuscular blockade induced by atracurium in a patient with myasthenia gravis were monitored and recorded using the evoked compound muscle action potentials (EMG). The anaesthetic and perioperative management were simplified by the use of this technique. The significance of the behaviour of atracurium is discussed.

Action Potentials↗

PubMed1984

Electromyography in anaesthesia. A comparison between two methods.

Two instruments measuring evoked compound muscle action potentials (EMG) produced by train of four stimulation of the ulnar nerve were compared. The neuromuscular transmission section of a Datex Anaesthesia and Brain Monitor (ABM), which utilises an integration technique to measure the EMG, and the Medelec MS6 , by which amplitude of the EMG was recorded and measured were attached to the same electrodes placed over adductor pollicis. Eight patients scheduled for surgery requiring non-depolarising neuromuscular blockade were studied. The changes in neuromuscular transmission measured by the two methods correlated well, with no statistically significant difference in results. The ABM provides a simple and accurate automatic measurement of evoked EMG for use in the study of neuromuscular transmission.

Action Potentials↗