Review of standard paediatric neuroradiology MRI protocols from 12 UK tertiary paediatric hospitals: is there much variation between centres?

AIM

To investigate how magnetic resonance imaging (MRI) examinations are protocolled in tertiary paediatric neuroradiology centres around the UK for some of the more common presentations encountered in paediatric neuroradiology, and to identify any variations of note.

MATERIALS AND METHODS

All 19 UK tertiary paediatric neuroradiology centres registered with the British Society of Neuroradiologists-Paediatric Group were contacted and asked if they could provide a copy of their standard MRI protocols. Twelve responded (63%) and 10 of the more common presentations were selected and the standard acquired sequences obtained at each participating centre were compared. Where available the collated protocols were also compared against current published guidance.

RESULTS

The basic sequences carried out by centres around the UK are similar; however, there are lots of variations overall. The only standardised protocol currently being implemented nationally in paediatric imaging is that for brain tumours. Otherwise, chosen protocols are generally dependent on the preferences and technical capabilities of individual centres. Suggested published protocols also exist for non-accidental injury (NAI), multiple sclerosis, epilepsy, and head and neck imaging.

CONCLUSIONS

The differences in MRI protocolling depend in part on technical capabilities and in part on the experience and preferences of the paediatric neuroradiologists at each centre. For most presentations, there is no consensus as to what constitutes the perfect protocol. The present results will be useful for specialist centres who may wish to review their current protocols, and for more generalist centres to use as a reference to guide their MRI protocolling.

524 QUALITY IMPROVEMENT PROJECT: INCORPORATING COMPREHENSIVE GERIATRIC ASSESSMENT INTO COMMUNITY HOSPITAL CLERKING

Elderly patients transferred to community hospitals often have complex medical, social, psychological, functional and pharmacological backgrounds that require careful assessment in order to create and deliver a high quality, patient-centred care plan. Unfortunately, time pressures experienced by staff in acute hospitals can make Comprehensive Geriatric Assessment (CGA) unfeasible for every patient. Moreover, junior members of the medical team may be unsure as to which aspects of a patient’s background and presentation constitute important elements of a CGA. Failure to recognise and document pertinent issues can lead to prolonged admissions, disjointed care and failed discharges.

Admission to a community hospital presents a convenient ‘checkpoint’ in the patient’s hospital journey at which to undertake a CGA. Recording the relevant information in an effective clerking proforma when the patient is admitted ensures that this information is displayed clearly and in a way that is accessible to all members of the multidisciplinary team. The pre-existing clerking proforma at Amersham Community Hospital omitted several important elements of CGA (such as examination of feet and gait, assessment of mood, FRAX-UK score, creation of a problem list etc.) The aim of this quality improvement project was to create a thorough, yet user-friendly and time-efficient clerking proforma which incorporated the important components of CGA.

Using BGS guidance and NICE quality standards, alongside suggestions from the medical team, the existing clerking proforma was adapted and reformed. After one month, feedback from the team was used to further improve the clerking proforma, ensuring that it was user-friendly, whilst meeting the standards set out by NICE and BGS. This was repeated as part of a second PDSA cycle.

The improved clerking proforma enables junior doctors to undertake a thorough and holistic assessment, promoting efficient detection of issues and the delivery of a higher quality of care.

A risky business: Teaching clinical risk assessment in the midst of a global pandemic

Introduction

Assessing risk is an important core skill yet there is not a consensus as to how to teach it. Clinically, there has been a move away from using risk prediction tools in favour of clinical judgement.We describe an iterative process to develop high quality, online teaching around risk assessment for medical undergraduates.

Objectives

To teach the clinical skill of risk assessment to enable medical students to evaluate and manage risk when encountering patients with mental health issues.

Methods

A half day tutorial was designed and refined in an iterative process using feedback from participants on this session and other concurrent teaching occurring in the department. Sessions were also reviewed by external medical educators to ensure quality and learning objectives were met.

Results

The average rating from 62 students was 4.4/5. Students commented that the session was well organised and delivered. Following feedback, the use of actors was prioritised to simulate evolving clinical situations. Students placed a high value on this: “simulated patients were amazing! They were really interesting and I was able to practice the skills I learnt over placement”. Logistical changes e.g. more breaks, followed appreciation of the exhausting nature of the session and maintained student engagement. There was increased emphasis on promoting group interaction through functions like a ‘break-out room’.

Conclusions

This session may give educators confidence that they can take risks when teaching the skill of risk assessment. Students were receptive and meaningfully engaged with concepts such as clinical judgement and bio-psycho-social formulations as opposed to ‘tick box’ assessments.

Effects of route of administration on oxytocin-induced changes in regional cerebral blood flow in humans

Could nose-to-brain pathways mediate the effects of peptides such as oxytocin (OT) on brain physiology when delivered intranasally? We address this question by contrasting two methods of intranasal administration (a standard nasal spray, and a nebulizer expected to improve OT deposition in nasal areas putatively involved in direct nose-to-brain transport) to intravenous administration in terms of effects on regional cerebral blood flow during two hours post-dosing. We demonstrate that OT-induced decreases in amygdala perfusion, a key hub of the OT central circuitry, are explained entirely by OT increases in systemic circulation following both intranasal and intravenous OT administration. Yet we also provide robust evidence confirming the validity of the intranasal route to target specific brain regions. Our work has important translational implications and demonstrates the need to carefully consider the method of administration in our efforts to engage specific central oxytocinergic targets for the treatment of neuropsychiatric disorders.

Shortage of paediatric radiologists acting as an expert witness: position statement from the British Society of Paediatric Radiology (BSPR) National Working Group on Imaging in Suspected Physical Abuse (SPA)

One of the most challenging areas of radiological imaging in children is the diagnosis of physical abuse. There is a dearth of paediatric radiologists willing to act as expert witnesses, particularly in the family courts. There are a number of reasons why radiologists may not be interested or willing to put themselves forward to work as expert witnesses in this field. A group of imaging experts recently formed the "British Society of Paediatric Radiology (BSPR) Working Group on Imaging in Suspected Physical Abuse (SPA)". The group comprises radiologists and neuroradiologists with current or previous experience of providing expert witness reports to the court in cases of SPA. The group met in January 2019 to explore pragmatic solutions to the chronic inefficiencies in both medical and legal practices and the challenges that arise from working in a legal arena with different structures, goals, and assessment criteria. Key issues concerned organisational inefficiencies, variable support from National Health Service Trusts and the Royal College of Radiologists to conduct this work, and the risk/benefit of involvement. This work is important for the patient, parents, and society in general, and highly rewarding for clinical practitioners who are involved, but there are several issues with current practices that discourage active participation. With several members of the group either retired or close to retirement, the shortage of experts is becoming a pressing issue within the UK, which requires an engaged multidisciplinary group to come up with creative solutions. Here, the group provide a consensus opinion highlighting the current barriers and potential facilitators to increasing the number of radiologists willing to provide opinions to the court.

Measurement of Activated Factor IX in Factor IX Concentrates: Correlation with In Vivo Thrombogenicity

Current in vitro tests for thrombogenicity of FIX concentrates used for prothrombin complex concentrates (PCCs), are of little value when applied to high purity FIX (HP FIXs). In the present study, we have developed a chromogenic assay for activated FIX (FIXa) and evaluated its ability to predict in vivo thrombogenic potential of HP FIXs in a modified Wessler stasis model. Among the HP FIXs, only 1 out of 7 products had no detectable FIXa; this product also showed no in vivo thrombogenicity. In the other 6 products, FIXa content ranged from 0.15–1.2 U/1000 iu FIX, and all showed some evidence of in vivo thrombogenicity, with mean thrombus scores ranging from 0.25–4. There was a significant positive correlation (r = 0.55, p <0.02) between FIXa levels and in vivo thrombogenicity of HP FIXs. NAPTT data were not significantly correlated with the in vivo results and the TFCT also showed no direct correlation with the mean thrombus score. These results indicate that HP FIXs may still carry a small residual thrombotic risk and measurement of FIXa content of these products may be a better predictor of thrombogenicity than the current in vitro tests.

Pseudodacryocystitis: paediatric case series of infected atypical ethmoid air cells masquerading as recurrent dacryocystitis

PurposeTo highlight the clinical and surgical considerations in treating patients with apparent recurrent acute dacryocystitis with a patent lacrimal system.MethodsThree children referred to a tertiary unit as recurrent acute dacryocystitis were reviewed retrospectively. Imaging and subsequent surgical intervention revealed the underlying diagnosis.ResultsAll three cases presented with recurrent abscesses in the region of the lacrimal sac that failed to respond to incision and drainage. The lesions were lower and more lateral to the usual location of a sac abscess and closer to the inferior orbital rim. All three cases were found to have patent lacrimal systems on syringing, and all were found to have infected, low-lying, anteriorly placed aberrant ethmoid air cells on computed tomography and magnetic resonance imaging. These were confirmed on subsequent surgical exploration.ConclusionsInfected low-lying ethmoid air cells can mimic dacryocystitis with recurrent abcesses. In cases where a patent nasolacrimal system is demonstrated and a more inferolateral location of the swelling than would be expected in dacryocystitis is seen, imaging is warranted to ensure the appropriate intervention is undertaken. Anterior ethmoidectomy as opposed to dacryocystorhinostomy is the appropriate treatment in these cases.

Mutations in PAX1 may be associated with Klippel-Feil syndrome

Pax genes are a highly conserved family of developmental control genes that encode transcription factors. In vertebrates, Pax genes play a role in pattern formation during embryogenesis. Mutations in Pax genes have been associated with both spontaneous mouse mutants and congenital human diseases. The mouse Pax1 mutant phenotype undulated is characterised by vertebral segmentation defects reminiscent of the human disorder Klippel-Feil syndrome (KFS). To determine whether PAX1 haploinsufficiency plays a role in KFS, we have defined the gene structure of the human PAX1 gene and screened 63 KFS patients for mutations in this gene. Differences in the PAX1 sequence were detected in eight patients. Two patients had a silent change within the paired box that was also seen in 2/303 control chromosomes. The other variants were missense, silent or intronic changes not represented in the control panel tested. The significance of these results and the possible role of PAX1 in the pathogenesis of KFS are discussed.

Inactivation and clearance of viruses during the manufacture of high purity factor IX

Haemophilia is a bleeding disorder characterised by a deficiency in Factor IX. Replacement therapy in the form of a Factor IX concentrate is a widely accepted practice. In this paper we describe a double virus inactivated chromatographic process for producing a high purity Factor IX product, MonoFIX((R))-VF. The process involves separation of the prothrombin complex by cryoprecipitation, fraction I precipitation and DEAE-cellulose adsorption, further ion-exchange chromatography of crude Factor IX, followed by solvent/detergent treatment. Heparin affinity chromatography is then used to further purify Factor IX. Final nanofiltration is sequential through 35 nm then 15 nm membrane filters. The principal virus inactivation/removal steps are solvent/detergent treatment and nanofiltration and the partitioning of relevant and model viruses provides further reduction in virus load through the production process.Solvent/detergent treatment was shown to achieve log reduction factors of 4.5 for HIV-1, 5.1 for Sindbis virus, 6.1 for vesicular stomatitis virus (VSV), 5.1 for bovine viral diarrhoea virus (BVDV) and 5.3 for pseudorabies virus (PRV). BVDV is a model for hepatitis C virus (HCV), and pseudorabies virus (PRV), like hepatitis B virus (HBV) is an enveloped DNA virus. Using scaled down models of the production process, we have also demonstrated the neutralization/partitioning of at least 6 logs of hepatitis A virus (HAV) during cryoprecipitation, Fraction I precipitation, and the DEAE adsorption and elution step, and a further 1.6 log reduction in HAV load as a result of heparin affinity chromatography. The log reduction factors for HAV as a result of the second ion-exchange chromatography step and as a result of enhanced neutralisation associated with solvent/detergent treatment were not significant. Nanofiltration was shown to contribute a further log reduction factor of 6.7 for HAV and 5.8 for BVDV indicating that log reduction factors of this order would be obtained with other viruses of a similar or larger size, such as HIV, HBV and HCV.Overall, these studies indicate that MonoFIX-VF is a product with an extremely high level of viral safety.

Immunotherapy of a viral disease by in vivo production of therapeutic monoclonal antibodies

Continuous and sustained in vivo production of monoclonal antibodies by engineered cells might render long-term antibody-based treatments cost-effective, avoid side effects associated with infusion of massive doses of antibody, and circumvent possible antiidiotypic responses against the therapeutic agent. The FrCasE retrovirus induces a lethal neurodegeneration on infection of newborn mice. We report here that implantation of cellulose sulfate capsules containing cells secreting an ectopic monoclonal antibody neutralizing FrCasE can prevent animals from developing the disease. All treated mice showed reduced or undetectable viremia in addition to a lack of the histopathological lesions characteristic of FrCasE infection. This work paves the way for a novel gene/cell antibody-based immunotherapy of a variety of severe viral and nonviral diseases.

Effects of inter-alpha-inhibitor and several of its derivatives on calcium oxalate crystallization in vitro

The bikunin peptide chain of the protease inhibitor inter-alpha-inhibitor (IalphaI) has been reported to be an inhibitor of calcium oxalate (CaOx) crystallization, and hence has been proposed as having a role in CaOx kidney stone formation. However, further experimental evidence is required to assess if fragments of IalphaI other than bikunin may play a role in the regulation of crystallization events in stone formation. The aim of the present study was to assess the effects of IalphaI and several of its derivatives on CaOx crystallization in a seeded inorganic system and to compare these effects with those of a known inhibitor of crystallization, prothrombin. IalphaI was purified from a preparation of human plasma and fragmented by alkaline hydrolysis, and two of its peptide chains, bikunin and heavy chain 1 (H1), were purified further by HPLC. Their purity was confirmed by SDS/PAGE. Using Coulter counter and [(14)C]oxalate analysis and scanning electron microscopy, IalphaI, its H1 chain and bikunin from urine and from plasma were shown to be relatively weak inhibitors of CaOx crystallization in vitro at expected physiological concentrations. It was concluded that members of the IalphaI family may not be as important in kidney stone formation as has been generally proposed, although further studies are required before a possible role for IalphaI and its fragments in stone formation can be unambiguously discounted.

Cerebral blood volume measured using near-infrared spectroscopy and radiolabels in the immature lamb brain

Near-infrared spectroscopy (NIRS) is a technique that is increasingly being used for the noninvasive measurement of cerebral blood volume (CBV) in newborn infants, but it has not been fully validated against established methods. These experiments in immature lambs (gestation 92+/-1 d, mean+/-SEM) compared CBV measured using NIRS-derived estimates of oxygenated Hb (n = 5) with CBV estimated with radiolabeled indicators (125I-labeled serum albumin and 51Cr-labeled red blood cells, n = 10). Total brain CBV (mL/100 g tissue) measured using NIRS was 2.5+/-0.2 compared with 2.5+/-0.2 using radiolabels (NS). Regional tissue plasma, red blood cells, and whole blood volumes from radiolabels varied significantly (p < or = 0.05) throughout the brain. Whole blood volume (mL/100 g tissue) was largest in choroid plexus (16.2+/-2.1) and least in white matter (0.7+/-0.1) with a significant hierarchy evident among regions: choroid plexus > cerebellum > cortex > brain stem = midbrain > white matter. Regional plasma and red blood cell distributions were similar to whole blood, being highest in choroid plexus (13.0+/-1.6 and 3.2+/-0.9, respectively), and least in white matter (0.8+/-0.1 and 0, respectively). These data from the immature lamb brain indicate that total CBV measured with NIRS is essentially identical with the volumes obtained using intravascular radiolabels. Among cerebral regions, white matter contributes little to the global blood volume measured with NIRS because its red blood cell content is very low.

Inter-alpha-inhibitor in calcium stones

1. A broad spectrum of proteins has been detected within calcium stones. A newcomer to the field of urolithiasis is the blood protein inter-alpha-inhibitor. Inter-alpha-inhibitor comprises three protein chains linked by chondroitin sulphate: two heavy chains, H1 (65 kDa) and H2 (70 kDa) and a light chain (approx. 30 kDa) most commonly known as bikunin. The physiological function of the two heavy chains is unknown; nor has their presence been reported in urine. However, bikunin has been implicated in various renal diseases, including urolithiasis. 2. This study was undertaken to determine which chains of inter-alpha-inhibitor are actually present in calcium kidney stones. Organic extracts were obtained from 10 calcium stones and analysed by SDS/PAGE and Western blotting. The H1 and H2 chains of inter-alpha-inhibitor were detected in 9 of the 10 stones, but only one stone contained a protein with a molecular mass close to that of bikunin (30-35 kDa). 3. These results demonstrate for the first time that H1 and H2 are present in stones and show that the bikunin chain of inter-alpha-inhibitor may not be the only part of the molecule implicated in stone formation.

A new regimen for starting warfarin therapy in out-patients

AIMS

Oral anticoagulation is increasingly used in elderly patients with atrial fibrillation to prevent embolic phenomena. The use of anticoagulants in this population is prophylactic rather than therapeutic and so there is no urgency to establish anticoagulation within the desired therapeutic range. The aim of the study was to develop an out-patient regimen for initiation of oral anticoagulation with warfarin which requires only weekly monitoring of the International Normalized Ratio (INR).

METHODS

The study was undertaken in two phases. In the first phase, factors which predict the final maintenance dosage of warfarin were defined and used to build a decision tree and dosage algorithm. In the second study the algorithm was tested. Patients were given 2 mg warfarin daily for 2 weeks and the INR at this time was used to predict the maintenance dose. Patients then attended for weekly measurements of the INR until steady state had been reached. Dosage adjustments were not made unless the INR was >4.0 or <1.5 for 2 consecutive weeks. The accuracy of the prediction was measured by calculating the mean INR of weeks 6-8 and the number of patients in the target range 2.0-3.0 was determined.

RESULTS

One hundred and seven consecutive out-patients (mean age 70 years range 64-86) completed the first study. The age, sex, height, weight, alcohol intake, number of cigarettes smoked, concomitant medication, clinical evidence of right heart failure, liver failure, abnormalities in liver enzyme estimations, baseline INR and INR after 2 weeks of 2 mg warfarin daily were used in a polytomous logistic regression analysis with stepwise inclusion of factors to determine which factors influenced the eventual maintenance dosage of warfarin. The INR after 2 weeks of 2 mg warfarin therapy predicted 70% of the variability of the maintenance dose. Of other factors only the sex of the patient had a large enough effect to be included in the prediction algorithm. One hundred and six patients (mean age 71 years range 50-85 years) completed the second study. Only one patient needed a dose adjustment in the first 2 weeks of warfarin 2 mg daily (INR 4.4). Overall, 60% patients were in the narrow target range (INR 2.0-3.0) at steady state. In five patients the INR was >4.0 at any visit after the second week and needed dosage adjustment. In four patients the INR was <1.5 at steady state.

CONCLUSIONS

We have developed a method of predicting the maintenance dose of warfarin in an elderly population based on the INR after 2 weeks of warfarin 2 mg daily, and the sex of the patient. This is a safe and convenient way of initiating warfarin therapy as an out-patient which requires only weekly INR checks.

Use of DNA transfer in the induction of metastasis in experimental mammary systems

The metastatic spread of cancer is a little understood process, in part because it is difficult to model the entire process using experimental approaches in vitro. The ability to transfer DNA into non-metastatic mammary cells and to observe the induction of metastasis in vivo provides a means for identifying DNA sequences that are associated with the development of metastatic capability. Using these techniques, a metastasis-associated cytoskeletal calcium binding protein, S100A4 (p9Ka), has been identified as an inducer of metastatic capability in benign rat mammary epithelial cells. Metastasis can also be induced in the rat mammary epithelial cells by fragments of DNA from metastatic, but not from benign, human breast tumour cells. These non-coding fragments of DNA act via the induction of osteopontin, an extracellular, integrin binding, calcium binding protein. Since both osteopontin and S100A4 are thought to be associated with malignancy in human breast cancer specimens, gene transfer techniques can identify genes for metastasis-inducing proteins that may play a role in breast cancer, and further suggest that cell migration/motility might be important in the metastatic process.

Gp130-mediated signal transduction in embryonic stem cells involves activation of Jak and Ras/mitogen-activated protein kinase pathways

The leukemia inhibitory factor/interleukin 6 (LIF/IL6) family of cytokines promotes cell type-specific pleiotropic effects by engaging multimeric receptor complexes that share the common affinity converter/signal transducing subunit gp130. While the maintenance of embryonic stem (ES) cell self-renewal is an activity unique to this family of cytokines, the intracellular signaling events mediated by gp130 remain largely unknown. Here we show a rapid and transient increase in the specific activity of the Src-related kinase Hck as well as of the Janus kinases Jak1, Jak2, and Tyk2 following treatment of ES cells with LIF or a combination of IL6 plus a soluble form of the IL6 receptor. Within 2 min of stimulation, we also observed increased tyrosine phosphorylation of SHC, activation of the guanidine nucleotide exchange activity on p21(ras), and an electrophoretic mobility shift of MAP kinase. Functional involvement of Hck and p21(ras) activation in gp130-mediated signaling is supported by the finding that the introduction of constitutively activated Hck or v-Ha-ras partially alleviates the requirement of ES cells for LIF to remain undifferentiated. In contrast, suppression of Jak1 in ES cells by antisense technology increased the amount of LIF required to retain their pluripotentiality. These results are consistent with the notion that gp130-mediated suppression of ES cell differentiation depends on signaling through at least two cascades, namely a p21(ras)-dependent pathway that possibly involves Hck, as well as a Jak kinase-dependent pathway.

Measurement of activated factor IX in factor IX concentrates: correlation with in vivo thrombogenicity

Current in vitro tests for thrombogenicity of FIX concentrates used for prothrombin complex concentrates (PCCs), are of little value when applied to high purity FIX (HP FIXs). In the present study, we have developed a chromogenic assay for activated FIX (FIXa) and evaluated its ability to predict in vivo thrombogenic potential of HP FIXs in a modified Wessler stasis model. Among the HP FIXs, only 1 out of 7 products had no detectable FIXa; this product also showed no in vivo thrombogenicity. In the other 6 products, FIXa content ranged from 0.15-1.2 U/1000 in FIX, and all showed some evidence of in vivo thrombogenicity, with mean thrombus scores ranging from 0.25-4. There was a significant positive correlation (r = 0.55, p < 0.02) between FIXa levels and in vivo thrombogenicity of HP FIXs. NAPTT data were not significantly correlated with the in vivo results and the TFCT also showed no direct correlation with the mean thrombus score. These results indicate that HP FIXs may still carry a small residual thrombotic risk and measurement of FIXa content of these products may be a better predictor of thrombogenicity than the current in vitro tests.

Stabilization of von Willebrand factor in banked blood by leucocyte depletion

The von Willebrand factor (vWf) activity, as measured by the ristocetin co-factor (vWf:RCo) and collagen binding (vWf:CBA) assays, declined progressively in standard blood units stored at 4 degrees C after a 2-day storage period. This loss of activity was accompanied by a loss and degradation of high molecular weight (HMW) vWf multimers. In studies using a paired design, filtration of blood with a high efficiency leucocyte-removal filter, prior to storage at 4 degrees C, led to significantly improved maintenance of vWf:RCo and vWf:CBA compared with unfiltered units (P < 0.01 after 8 days). Loss and degradation of HMW vWf decreased when blood was filtered prior to 4 degrees C storage. Filtration had no effect on vWf-associated activities when blood was stored at 22 degrees C for 10 days. These results indicate that part of the storage lesion of vWf in banked blood is due to leucocyte-mediated removal and degradation of HMW vWf. This has implications when specifying plasma for the production of vWF concentrates and may also play a role in the haemostatic lesion associated with massive transfusion of stored blood.

Modulation of fibrinogen content in cryoprecipitate by temperature manipulation during plasma processing

In routine blood bank production of single-donation cryoprecipitate, the introduction of a 16-hour hold at 4 degrees C, with the frozen plasma units packed into polystyrene containers, resulted in plasma prethaw temperatures of -4 degrees C to -8 degrees C. This in turn resulted in cryoprecipitate fibrinogen levels that were 214 percent of those obtained when units were thawed immediately after removal from -30 degrees C storage. In scale-model production of factor VIII concentrate, plasma warmed from -30 to -10 to -15 degrees C over 18 hours before pooling and thawing yielded cryoprecipitate fibrinogen levels that were 66 percent of those found in plasma warmed to -2 to -5 degrees C over the same period. Processing -30 degrees C plasma without a warming period led to cryoprecipitate fibrinogen levels that were 40 percent of those obtained from plasma warmed to -2 to -5 degrees C. These differences were accentuated after purification of the cryoprecipitates to an intermediate-purity factor VIII concentrate. These results suggest that simple modifications in production methods allow the fibrinogen content of cryoprecipitate to be tailored to specific uses.

The effects of oxytocin on the pulmonary and systemic circulation in pregnant ewes

The haemodynamic effects of oxytocin on the pulmonary and systemic circulation were studied in six awake, pregnant (greater than 140 days gestation) ewes. Bolus doses of oxytocin 0.2 units/kg and then 0.8 units/kg were administered. A dose of 0.2 units/kg resulted in small but significant increases in mean pulmonary artery pressure (14%, P less than 0.05) and pulmonary vascular resistance (24%, P less than 0.05. A bolus of 0.8 units/kg resulted in a significant increase in mean arterial pressure (20%, P less than 0.05) and systemic vascular resistance (33%, P less than 0.05). Acute pulmonary hypertension was then induced with glass bead microemboli (150-200 microns), with an increase in pulmonary artery pressure of 26 mmHg and pulmonary vascular resistance of 448 dyn. s. cm-5. Boluses of oxytocin 0.2 and 0.8 units/kg were then administered. There were no significant changes, except for a 30% increase in systemic vascular resistance at one minute after oxytocin, 0.8 units/kg (P less than 0.05).

von Willebrand factor characterization of a severe dry-heat treated factor VIII concentrate, AHF (high purity)

Eight batches of a severe dry-heat treated (80 degrees C for 72 hours) Factor VIII concentrate manufactured by the Commonwealth Serum Laboratories (CSL Ltd.) were analysed for the following von Willebrand factor-related (vWf) activities: ristocetin cofactor activity (vWf:RCof), collagen binding activity (CBA), vWf antigen levels (vWf:Ag), vWf multimeric analysis and 2-stage FVIII clotting activity (VIII:C). The average potency per vial of vWf:Ag was 440 +/- 80 units, vWf:RCof 500 +/- 60 units, CBA 350 +/- 50 units and VIII:C 242 +/- 36 International Units. Multimeric analysis indicated the presence of high molecular weight multimers and a triplet structure slightly different to normal plasma. Viral inactivation studies using a marker virus, Sindbis, demonstrated that the terminal severe dry- heating step reduced the viral load in the product by greater than 6 log10TCID50/ml. This CSL Ltd. FVIII concentrate may thus provide a safer, purer and more convenient source of vWf than cryoprecipitate. Clinical studies to establish product efficacy in patients with von Willebrand's disease are underway.

Effect of fetal haemoglobin on the accuracy of pulse oximetry in preterm infants

Pulse oximeters are programmed with a calibration curve derived from studies done in adults. Whether fetal haemoglobin levels affect their reliability is unclear. This study reports the accuracy of pulse oximetry in 22 preterm infants (mean 31 weeks, range 25-36 weeks gestation) between 1 h and 73 days of age. Oxygen saturation obtained from a Nellcor N-200 pulse oximeter (SpO2) was compared with simultaneous arterial values (functional SaO2) measured by a Radiometer OSM3 Hemoximeter over a SpO2 range of 83-99%. Fetal haemoglobin (HbF), carboxyhaemoglobin (HbCO) and methaemoglobin (HbMet) measured by the hemoximeter ranged between 0-100%, 0-3.5% and 0-0.8% respectively. Linear regression analysis revealed a close correlation between SpO2 and functional SaO2 (SpO2 = 0.75 SaO2 + 24.43, r = 0.88, P less than 0.001) over a wide range of values for PCV, heart rate, blood pressure, PaO2, PaCO2 and pH. The mean SpO2-SaO2 difference of 1.3, (s.d. 2.5%, P less than 0.001) was unaffected by HgF, HbCO or HbMet but was increased in infants receiving inotropic support. We conclude that the Nellcor N-200 pulse oximeter gives reliable oxygen saturation measurements unaffected by the HbF level in preterm infants.

Effects of plasma collection systems and processing parameters on the quality of factor IX concentrate

Using pilot-scale production of our present factor IX (II and X) concentrate, we have studied the effects of starting plasma source and processing parameter on two in-vitro indicators of product quality - yield and thrombogenic potential. Plasma source did not affect factor IX yield but had a marked effect on thrombogenic potential. Factor IX concentrates produced from plasma derived through centrifugation-based technology showed significantly higher thrombogenic potential than products derived from plasma derived through a filtration-based system. Removal of Cohn fraction I prior to ion-exchange chromatography resulted in a drop in factor IX yield and thrombogenic potential, as did heat treatment to 80 degrees C for 72 h. We conclude that a membrane-filtration-based plasmapheresis system may be the preferred method of plasma procurement for factor IX concentrate production.

Comparison of two dimensional immunoelectrophoresis and multimer analysis in the study of von Willebrand factor

To assess the validity of the multimeric analysis of von Willebrand factor (vWf), this technique was compared with two dimensional immunoelectrophoresis using samples of purified vWf obtained by gel filtration and plasma samples from a patient with severe von Willebrands disease who was receiving prophylaxis with cryoprecipitate. It is concluded that except for specialised clinical and research purposes, two dimensional immunoelectrophoresis provides a clear picture of the multimeric composition of the vWf molecule, and that this is sufficient for routine research and clinical use, without having to confirm the data by multimeric analysis.