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Biomedical subjects

C Cousins

Publications and source records attributed to C Cousins.

At least 19 recordsLinked to original sources
PubMed2005

Hepatitis B virus (HBV) DNA screening of blood donations in minipools with the COBAS AmpliScreen HBV test.

BACKGROUND: The risk of hepatitis B virus (HBV) transmission by blood transfusion (estimated at 1 in 63,000-1 in 205,000 units in the United States) exceeds that of hepatitis C virus (HCV) or human immunodeficiency virus (HIV). Reduction of window-period HBV transmissions through detection of HBV DNA-positive units by minipool nucleic acid testing (MP NAT) would be expected to decrease this risk. STUDY DESIGN AND METHODS: A large multicenter study of the COBAS AmpliScreen HBV test (Roche Molecular Systems) was conducted on minipools of 24 blood donation specimens. The yield of HBV DNA-positive, hepatitis B surface antigen (HBsAg)-negative window-period donations was determined relative to current and newly licensed HBsAg assays. Donors with selected HBV DNA, HBsAg, and anti-hepatitis B core antigen (HBc) results were further evaluated. RESULTS: The detection rate of window-period units was 1 in 352,451 (95% confidence interval, 1 in 2,941,176-1 in 97,561). Assay specificity was high (99.9964%). HBV DNA was detected in 84 percent of HBsAg-positive, anti-HBc-positive donations by MP NAT and in 94 percent when individual-donation (ID) NAT was added. HBV DNA was detected in 0.03 percent of HBsAg-negative, anti-HBc-positive donations by MP NAT and in 0.41 percent when ID NAT was added. CONCLUSIONS: Implementation of HBV MP NAT will provide an increment in safety relative to HBV serologic screening, similar to that for HCV and in excess of that for HIV. Our data indicate that the implementation of HBV MP NAT would likely interdict 39 HBV window-period units and prevent 56 cases of transfusion-transmitted HBV infection annually. The current data indicate that HBV MP NAT should not lead to discontinuation of anti-HBc testing but that discontinuation of HBsAg testing with retention of anti-HBc testing may be possible.

Blood Donors↗
PubMed2004

Medical interventional procedures-reducing the radiation risks.

Over the last 40 years, the number of percutaneous interventional procedures using radiation has increased significantly, with many secondary care clinicians using fluoroscopically guided techniques. Many procedures can deliver high radiation doses to patients and staff, with the potential to cause immediate and delayed radiation effects. The challenge for interventionists is to maximize benefit, whilst minimizing radiation risk to patients and staff. Non-radiologist clinicians are often inadequately trained in radiation safety and radiobiology. However, clinical governance and legislation now requires a more rigorous approach to protecting patients and staff. Protection can be ensured, and risks can be controlled, by appropriate design, procurement and commissioning of equipment; quality assurance; and optimal operational technique, backed by audit. Interventionists need knowledge and skills to reduce the risks. Appropriate training should include awareness of the potential for radiation injury, equipment operational parameters, doses measurement and recording methods and dose reduction techniques. Clinical governance requires informed consent, appropriate patient counselling and follow-up.

Eye↗
PubMed2003

Idiopathic intracranial hypertension: 12 cases treated by venous sinus stenting.

BACKGROUND: The high pressures documented in the intracranial venous sinuses in idiopathic intracranial hypertension (IIH) could be the result of focal stenotic lesions in the lateral sinuses obstructing cranial venous outflow. OBJECTIVE: To explore the relation between venous sinus disease and IIH. METHODS: 12 patients with refractory IIH had dilatation and stenting of the venous sinuses after venography and manometry had shown intracranial venous hypertension proximal to stenoses in the lateral sinuses. Intrasinus pressures were recorded before and after the procedure and correlated with clinical outcome. RESULTS: Intrasinus pressures were variably reduced by stenting. Five patients were rendered asymptomatic, two were improved, and five were unchanged. CONCLUSIONS: The importance of venous sinus disease in the aetiology of IIH is probably underestimated. Lateral sinus stenting shows promise as an alternative treatment to neurosurgical intervention in intractable cases.

Adult↗
PubMed2002

Ultrasound enhanced detection of individual meningococcal serogroups by latex immunoassay.

AIMS: To examine A, C, Y, and W135 Neisseria meningitidis serogroup characterisation by ultrasonic standing wave enhanced latex agglutination tests (USELATs) of clinical samples. In addition, to determine USELAT enhancement of detection sensitivity for the individual antigens compared with conventional card latex agglutination tests (LATs). METHODS: Wellcogen (Abbott Murex), Slidex meningite kit 5 (bioMerieux), and Pastorex (Sanofi) kits and beads coated in house with antibodies to Y and to W135 alone were tested. Positive control antigens consisted of A and C polysaccharide preparations and the Pastorex Y/W135 kit sample. The limiting concentrations of antigen detection were determined by USELAT and by LAT. Thirty five clinical samples (plasma), previously characterised by the polymerase chain reaction (PCR) and culture, were tested by USELAT and, when sample volume allowed, by LAT. RESULTS: USELAT enhancement of control antigen detection ranged from 16 to 128 fold for the different latex systems. Enhancements for the different control antigens were comparable between kits. USELAT tests of clinical (A/C/Y/W135) samples (n = 15) with the Wellcogen (A/C/Y/W135) and Slidex meningite (A/C/Y/W135) kits showed comparable specificities. A set (n = 22) of Y and W135 samples gave 18, 19, and 17 positive results for Wellcogen (A/C/Y/W135), Pastorex (A/C/Y/W135), and in house beads (Y/W135), respectively. Positive USELAT PCR and culture results were concordant. A typical sensitivity for the commercial kits was 80% (Wellcogen). CONCLUSIONS: USELAT identified serogroups for 80% of samples, whereas LATs identified only 40%. The USELAT detection of the A, C, Y, and W135 antigen serogroups showed comparable enhancement for the kits tested. The commercial availability of latex beads coated with antibody to the Y and W135 serogroups would expedite their identification.

Antigens, Bacterial↗
PubMed2001

Detection of pelvic lymph node metastases in gynecologic malignancy: a comparison of CT, MR imaging, and positron emission tomography.

OBJECTIVE: Accurate assessment of lymph node status before treatment is critical in the treatment of gynecologic cancers because the 5-year survival and treatment of women is influenced by lymph node involvement. The aims of this study were to investigate the ability of X-ray CT, MR imaging, and (18)F-FDG positron emission tomography (PET) to detect pelvic lymph node metastases by comparing imaging with histopathologic findings after lymph node dissection. MATERIALS AND METHODS: Eighteen patients with gynecologic cancers were studied by all three imaging methods before surgery. The images were initially reviewed with routine diagnostic conditions and then, subsequently, by two observers who were unaware of the clinical and histopathologic findings of the patients. The nodal sites were split into upper (aortic to common iliac bifurcations) and lower (common iliac bifurcations to inguinal ligament) iliac chains. All observers' results were statistically analyzed with specificity, sensitivity, positive and negative predictive values, Fisher's exact test (individual observers) or chi-square test (combined observers), and Cohen's kappa test. RESULTS: Eight of 18 patients had lymph node metastases at histology. Findings of all three modalities agreed in full in only one patient. CT correctly revealed 10 node-negative patients, whereas MR imaging was correct in eight of these patients. (18)F-FDG PET correctly depicted one patient with lymph nodes negative for tumor. CT was the most specific imaging modality (97.0%), with MR imaging and PET rendering values of 90.7% and 77.3%, respectively, but sensitivity of all modalities was low (CT, 48.1%; MR imaging, 53.7%; PET, 24.5%). Observer agreement for each modality was good; kappa values among all observers were 0.88 for CT, 0.85 for MR imaging, and 0.72 for PET. CONCLUSION: CT is the most specific modality for detecting lymph nodes positive for tumor in gynecologic cancers, whereas MR imaging is the most sensitive. The poor results of PET in the pelvis are attributed to urinary (18)F-FDG in the ureters or bladder, which may mask or imitate lymph node metastases.

Adult↗
PubMed2000

A comparison of the time required by radiologists for the preparation of clinico-radiological meetings when film and PACS are used.

The hypothesis was that when a hospital-wide Picture Archive and Communications System (PACS) is used, preparation for clinico-radiological meetings is faster, and more images are available, than when a conventional film system is used. This paper reports a study which compared the preparation time by radiologists when film was used with the time for the same activity when a hospital-wide PACS was used at Hammersmith Hospital for the preparation of the respirator medicine and hepato-biliary meeting. It was found that when PACS was used the time per patient to prepare for the respiratory medicine session was reduced by 11.1 min and that similarly, 16 min per patient was saved in the preparation of the hepato-biliary sessions. The number of images which were unavailable for the session was reduced when PACS was in operation, but this reduction was not shown to be statistically significant. The introduction of PACS at Hammersmith Hospital has significantly reduced the time spent by radiologists in preparing for the two clinico-radiological sessions studied and, if this is extended to the other numerous sessions held each week, contributes to a considerable saving of staff time within the radiology department.

Communication↗
PubMed1999

Clearance kinetics of solutes used to measure glomerular filtration rate.

Agents used to measure glomerular filtration rate (GFR) give a biexponential plasma disappearance curve on multiple peripheral venous sampling between 20 min and 4 h after intravenous injection. These two exponentials are generally regarded to represent equilibration of agent throughout the extracellular fluid (ECF) space and renal clearance, respectively. In seven subjects undergoing diagnostic arteriography, arterial and antecubital venous plasma samples were obtained up to 60 min in five and up to 120 min in two following simultaneous intravenous injection of 99Tcm-diethylene triamine pentaacetate (99Tcm-DTPA) and inulin. The count rate from 99Tcm was simultaneously recorded over the calf with a collimated scintillation probe in five subjects up to 60 min post-injection. The arterial and venous time-concentration curves were interpolated and subtracted to give a curve of the arterio-venous (A-V) concentration difference, which was then integrated. Arterial time-concentration curves display three exponentials, the first of which has the largest amplitude and disappears by about 20 min. The A-V concentration difference becomes zero at about the same time. The integral of the A-V concentration difference, which represents activity in the interstitial space of the forearm, has a time course consistent with the second compartment of a model of two compartments in series (the first being plasma) and a time course that is reciprocally similar to the first exponential of the triexponential arterial plasma curve. The curve externally recorded by scintillation probe has a shape consistent with a signal that is the composite of interstitial 99Tcm-DTPA and plasma 99Tcm-DTPA activities. The arterial plasma clearance curve of GFR agents is triexponential; the first exponential reflects equilibration of agent between plasma and the interstitial space of carcass tissue (mainly muscle and skin). The second exponential is minor compared with the first; it is not clear what it represents. The third exponential reflects renal clearance.

Adult↗
PubMed1997

Comparative kinetics of microvascular inulin and 99mTc-labelled diethylenetriaminepenta-acetic acid exchange.

1. After simultaneous intravenous injection as a mixture, 99mTc-labelled diethylenetriaminepentaacetic acid (99mTc-DTPA; molecular mass 492 Da) and inulin (approximately 6000 Da) gave arterial plasma clearance curves consisting of three exponentials, the time courses of which were not significantly different between the two solutes. 2. The ratio of 99mTc-DTPA to inulin concentration in antecubital venous plasma (normalized to the ratio in arterial plasma at 30 s) was 0.6, significantly less than unity, within 2 min after intravenous injection, but increased to reach unity by 60 min. The minimum concentration ratio of 99mTc-DTPA to inulin in arterial plasma was 0.75 at 4 min, also rising to just above unity at 60 min. 3. The extraction fraction from plasma to interstitial space was higher for 99mTc-DTPA (approximately 0.5) than for inulin (approximately 0.2). For both solutes, the net extraction fraction decreased with time, becoming negative at about 25 min after injection. Thereafter, the net extraction fractions remained negative, between -0.05 and -0.1, and not significantly different between the two solutes. 4. 99mTc-DTPA time-activity curves recorded over the limbs with scintillation probes were biphasic, with an initial phase corresponding closely in time with the first exponential of the arterial 99mTc-DTPA plasma clearance curve. The second phase corresponded in time to the intermediate exponential of the arterial 99mTc-DTPA plasma clearance curve. 5. The time course of net 99mTcm-DTPA extraction fraction across the forearm vascular bed was bi-exponential, with phases corresponding in time with the two phases of the limb uptake curves. 6. Deconvolution analysis of the limb time-activity curves, using the arterial time-concentration curve as the input function, gave bi-exponential 99mTc-DTPA impulse response curves in which the time courses of the exponentials corresponded with the first and intermediate exponentials of the arterial 99mTc-DTPA clearance curve. 7. The bi-exponential nature of the equilibrium of 99mTc-DTPA between vascular and interstitial compartments suggests the presence of two separate functional volumes within the interstitial space. Although 99mTc-DTPA and inulin clearly diffuse at different rates across the endothelium, as would be expected from their disparate sizes, the similarity in the time courses of their initial exponentials and simultaneous equalization of transfer rates (i.e. when net extraction fraction was zero) is consistent with the hypothesis that inulin moves initially into a smaller functional interstitial fluid volume than 99mTc-DTPA. The total distribution volumes, however, are not significantly different between the two solutes.

Adult↗
PubMed1995

Assessment of the value of the immediate postoperative chest radiograph after cardiac operation.

The value of the immediate postoperative chest radiograph upon a patient's return to the intensive care unit after a cardiac surgical procedure is uncertain. This study represents a prospective analysis of the immediate postoperative radiograph in 100 consecutive adult patients undergoing cardiac operations. In 11 patients it was found that the routine postoperative radiograph was of value when it was necessary either to clarify or confirm clinical findings or to check the position of an intraaortic balloon catheter. For those chest radiographs that were deemed unnecessary, only one of 89 were found to be of clinical value. Furthermore, in those situations in which an emergency radiograph was obtained, the routine radiograph was not found to be contributory to patient management. We conclude that the policy of obtaining routine, immediate postoperative chest radiographs in the absence of a specific clinical indication provides virtually no additional clinical yield. Residents should therefore request radiographs only to check the position of an intraaortic balloon catheter, and to clarify or confirm a clinical diagnosis.

Adult↗
PubMed1995

Non-invasive measurement of microvascular permeability to a small solute in man: validation of the technique.

1. The purpose of the study was to evaluate a non-invasive technique for measurement of microvascular permeability to a small hydrophilic solute. 2. The technique measures the clearance of 99mTc-labelled diethylenetriaminepenta-acetic acid (99mTc-DTPA) from plasma into interstitial fluid in a limb after intravenous injection and uses a scintillation probe and a technique of graphical analysis called the Patlak plot, the uptake constant of which reflects 99mTc-DTPA transfer from plasma to interstitial fluid. Using deconvolution analysis, the retention function in the limb of intravenous 99mTc-DTPA was also measured. 3. The clearance values given by these two analytical techniques were compared with clearance from the same vascular bed after bolus femoral intra-arterial injection of 99mTc-DTPA. 4. Sixteen patients undergoing routine diagnostic arteriography were studied: six received sequential femoral intra-arterial injections of 99mTc-labelled human serum albumin (HSA) and 99mTc-DTPA, two received sequential intra-arterial and intravenous injections of 99mTc-HSA and eight received sequential intra-arterial and intravenous injections of 99mTc-DTPA. Tissue uptake and clearance were recorded from the limb with a scintillation probe and plasma clearance by arterial blood sampling. Tracer recirculation was addressed using a second scintillation probe over the contralateral limb. 5. After intra-arterial injection, 99mTc-HSA clearance was monoexponential, reflecting intravascular transit, and was completed by 2-5 min in seven subjects and in about 10 min in one. The corresponding 99mTc-DTPA clearance curves in the six subjects who also received intra-arterial DTPA were biexponential, analysis of which yielded a 99mTc-DTPA extraction fraction of about 0.6. By comparison with 99mTc-HSA clearance, the first exponential clearly corresponded to intravascular transit of unextracted 99mTc-DTPA. 6. In the eight patients given sequential intra-arterial and intravenous injections of 99mTc-DTPA, the second exponential recorded after intra-arterial injection, representing 99mTc-DTPA clearance from the interstitial fluid, agreed well with (a) the Patlak uptake constant recorded over the limb after intravenous injection, representing clearance from plasma into the interstitial fluid and (b) the retention function of 99mTc-DTPA in a limb calculated by deconvolution analysis. The mean clearance following intra-arterial injection (expressed in relation to extracellular fluid volume) was 9.6 (SD 2.4) ml min-1 100 ml-1, while the corresponding mean clearance after intravenous injection was 8.8 (2.1) ml min-1 100 ml-1 calculated by Patlak analysis and 10.5 (2.7) ml min-1 100 ml-1 by deconvolution analysis.(ABSTRACT TRUNCATED AT 400 WORDS)

Capillary Permeability↗
PubMed1995

Effect of arterial cannulation and contrast agents on blood coagulation.

RATIONALE AND OBJECTIVES: Nonionic contrast media have been considered by some to have thrombogenic properties. We prospectively assessed the effect of femoral artery catheterization and both nonionic and ionic contrast media on the coagulation parameters--fragment 1 + 2 (F1 + 2) and fibrinopeptide A (FpA)--during clinical angiography. METHODS: Seventeen patients undergoing aortography were included. Blood samples were obtained before and after arterial puncture and before and up to 30 min after contrast administration. RESULTS: An increase in FpA was observed after arterial puncture (range = 8.4 +/- 1.9 to 13.6 +/- 2.3 ng/ml, p < .004; data are written as mean +/- standard error of the mean). There was an observed increase in F1 + 2 after arterial puncture that was not statistically significant (2.0 +/- 0.4 to 2.3 +/- 0.4 nmol/l). No further increase was observed in either FpA or F1 + 2 levels after nonionic or ionic contrast media administration. CONCLUSION: The increased activity of the coagulation system during angiography is related to the arterial puncture, and nonionic and ionic contrast media have no thrombogenic potential in vivo.

Adolescent↗
PubMed1994

Xanthogranulomatous pyelonephritis in childhood: ultrasound and CT diagnosis.

Four cases of diffuse xanthogranulomatous pyelonephritis (XPN) in young children are presented. In three patients the clinical picture was one of weight loss, anaemia and neutrophilia with a large renal mass. The fourth presented with haematuria. Ultrasound (US) and CT findings were almost identical in all four patients. US showed the affected kidney was massively enlarged but retained a reniform shape. Dilated fluid spaces containing calculi were present. CT confirmed the US findings and revealed peripheral enhancement without contrast excretion, with dilated calyceal spaces producing the "bear paw sign". Extrarenal extension into abdominal wall and psoas muscle is typical and was well demonstrated by CT. The affected kidneys were non-functioning and nephrectomy was required. Typical US and CT features allow a confident diagnosis of XPN and appropriate early treatment.

Child, Preschool↗
PubMed1994

Technical note: radiological insertion of an implantable drug delivery system.

A fully implantable drug delivery system has been shown to overcome many of the problems of long-term venous access. Traditionally these have required surgical implantation but we describe a simple, cost-effective and successful technique for the percutaneous insertion of an implantable vascular device (Vascuport, Ohmeda) in the angiography suite under local anaesthesia. It was successful in all 19 patients in whom it was attempted, with only one minor complication. We recommend that the procedure should be performed in X-ray departments using screening and conventional guidewire techniques.

Anesthesia, Local↗
PubMed1993

The clotting issue: etiologic factors in thromboembolism. II. Clinical considerations.

RATIONALE AND OBJECTIVES: The authors analyze the origins of the "clotting issue," the controversy that began in the 1980s when contrast media, once perceived as good flushing agents for catheters because of their assumed anticoagulant properties, came under attack for allegedly causing thromboembolism. Laboratory studies as well as a number of clinical reports seemed to substantiate this charge. Nonionic agents in particular were accused by some clinicians of being more likely to cause clots to form in syringes contaminated with blood than were ionic agents. The authors wanted to determine whether some lapse in operator technique rather than a fault in the contrast agent might be to blame. The theory that the syringe and catheter materials, and not the contrast agent itself, could be the source of thromboembolic problems in angiography also is examined. METHODS: The authors reviewed studies and reports on both sides of the issue and conducted laboratory and clinical studies of their own. For the syringe materials analysis, they used a fibrinopeptide A (FpA) enzyme-linked immunosorbent assay (ELISA) test to monitor levels as a marker of activation of coagulation. They tested catheter materials using the same technique. RESULTS: Clots were found only in nonionic agents, but under nonclinically relevant circumstances. If the anticoagulant effect of the nonionic contrast agent was maximized by mixing rather than layering blood and agent, clots did not form. In their materials analysis, the authors demonstrated that glass syringes are thrombogenic, causing vigorous contact activation, and that plastic is less so. Polyurethane catheters are more thrombogenic, polyethylene less so. One survey conducted in the 1970s on the clinical incidence of thromboembolism in coronary angiography suggested that the single most important factor in the etiology is poor angiographic technique. The authors' studies supported their thesis. CONCLUSIONS: In terms of the findings from laboratory studies, misinterpretation of data by nonclinicians is one problem. No evidence suggests that nonionic contrast agents are in any way prothrombotic or thrombogenic. On the contrary, in line with their greater inertness, nonionic agents have weaker effects. Ionic contrast media may cause more endothelial injury and associated localized platelet deposition than nonionic contrast media, and more anticoagulant contrast agents are more toxic. If anticoagulation is required, therefore, it should be achieved by such procedures as carefully controlled systemic heparinization rather than by resorting to more toxic materials. The activation of coagulation is caused by endothelial injury and by prolonged contact between blood and foreign surfaces such as syringes or catheters, but is inhibited by the contrast agent. Because a thrombus may form inside the catheter, whatever contrast agent is used, flushing is important. The authors agree with the findings of one study that the incidence of thromboembolism in coronary angiography, and probably in other catheter procedures, is markedly operator dependent. The materials of the syringes and catheters used, as well as the state of the patient's intrinsic clotting, are more important factors than the contrast agent. The authors conclude that materials other than the contrast agents are the cause of thromboembolic problems; and that, being anticoagulant, contrast agents are entirely helpful, if variably so, in angiographic procedures.

Blood Coagulation↗
PubMed1991

Case report: duodeno-pericardial fistula.

A case of spontaneous duodeno-pericardial fistula is described. An elderly female presented with pericarditis. The chest radiograph demonstrated a pneumopericardium. The patient died before further investigation and a duodeno-pericardial fistula was found at necropsy. This condition has not previously been described.

Aged↗
PubMed1991

Lymphatic abnormalities in Alagille's syndrome.

Chylous pleural effusions developed in a patient with Alagille's syndrome who had dysplasia of the lymphatic system. Lymphatic abnormalities are not a recognised feature of Alagille's syndrome.

Adult↗