Thermal induced deflection of a porcelain-zirconia bilayer: Influence of cooling rate.

OBJECTIVE: To determine the thermal expansion of a porcelain (VM9) and tetragonal zirconia (Y-TZP) as well as the deflection upon re-heating and cooling of a bilayer fabricated from these two materials after slow and rapid cooling during initial fabrication. METHODS: The coefficient of thermal expansion (CTE) of bulk porcelain and Y-TZP as well as bilayer beam deflection was measured with a novel non-contact optical dilatometer. The influence of cooling rate during initial fabrication of the porcelain-zirconia bilayer and the bulk porcelain during subsequent heating and cooling is investigated. Specimens were heated to 900°C in the dilatometer, well in excess of the glass transition temperature (Tg) and softening temperature (Ts) of the porcelain. RESULTS: The thermal expansion of the porcelain above Tg exhibits a threefold increase in CTE over that observed below Tg. Observations of the bilayer deflection reflect the difference in the CTE of the component materials and enable Tg and Ts temperatures for the porcelain to be estimated. Initial cooling rate of the porcelain and porcelain-YTZP bilayer was found to have a profound influence on the subsequent response to slow reheating and cooling as well as the resultant residual deflection. SIGNIFICANCE: The estimation of the residual stress and potential for chipping of porcelain-zirconia dental restorative systems should not be based solely on thermal expansion data measured below Tg.

Effect of different surface treatments and adhesives on repair bond strength of resin composites after one and 12 months of storage using an improved microtensile test method.

OBJECTIVES: To evaluate the effect of surface treatments and bonding systems on the repair bond strength between composite materials after one and 12 months of storage, using an improved microtensile test method. METHODS: A total of 72 composite cylinders (Tetric Evo Ceram, Ivoclar) were fabricated, stored in distilled water for two weeks followed by thermal cycling (5000 times between 5°C and 55°C), and served as substrate. The cylinders were mechanically roughened using 320-grit silicon carbide sandpaper, etched with 37% phosphoric acid gel, rinsed with water, and divided equally into three experimental groups: group 1, unchanged surface; group 2, sandblasting of the surface (CoJet tribochemical silica sand, 3M ESPE; Microetcher II, Danville Engineering Inc); and group 3, surface silane coating (Bis-Silane, BISCO Inc). Eight control cylinders were prepared and underwent similar aging as the substrate. Each experimental group was divided into subgroups that received the following bonding systems: one-step self-etching adhesive (AdheSE One, Ivoclar Vivadent), two-step self-etching adhesive (Clearfil SE, Kuraray America), and three-step etch-and-rinse adhesive (Adper Scotchbond Multi-Purpose, 3M ESPE). Fresh composite (Tetric Evo Ceram, Ivoclar) was placed and cured on top of the prepared substrate cylinders. The specimens were placed in distilled water for a week and thermocycled the same way as before. Eight composite control cylinders were also stored and thermocycled for the same period of time. Half of the cylinders in each test group were tested at one month and the second half at 12 months. The cylinders were serially sectioned in an automatic cutting machine, producing 10 to 20 1.1 × 1.1-mm test specimen beam from each cylinder. Specimens were prepared for microtensile testing and the tensile strength calculated based on the force at fracture and specimen dimension. The fracture surfaces were examined under a stereomicroscope and the type of fracture noted. RESULTS: The mean tensile strength of composite control was 54.5 ± 6.0 MPa at one month and 49.6 ± 5.1 MPa at 12 months. The mean tensile strength for the repaired groups ranged from 26.4 ± 6.8 MPa to 49.9 ± 10.4 MPa at one month and 21.2 ± 9.9 to 41.3 ± 7.5 at 12 months. There was a statistical difference between all groups (p<0.05) at one month. This difference was less pronounced at 12 months. The highest repair strength was obtained in the group having a silane-coated surface and Clearfil, the two-step self-etching adhesive. Clearfil also had the highest repair strength within each surface treatment group. There was a tendency for lower tensile strength at 12 months compared with one month. Most fractures were of the adhesive type; the highest number of cohesive fractures, 16% at one month and 12% at 12 months, were in groups with the highest tensile strength. CONCLUSION: The best repair bond strength was achieved by using freshly mixed silane solution on the substrate in addition to an adhesive, rendering a thin bonding layer.

Comparison of a Trigger Tool and voluntary reporting to identify adverse events in a paediatric intensive care unit.

Reduction of adverse events depends on accurate detection. The utility of a Trigger Tool to detect and classify severity of adverse events in an intensive care unit of a paediatric university hospital was compared to voluntary reporting. Sixty patient records were randomly selected from 314 admissions over three months. Events detected by the Trigger Tool were classified by two independent investigators as insignificant, minor, moderate, major or catastrophic. Examination of each record required, on average, 40 minutes. Ninety-eight adverse events (1.66/patient) were detected in 59 available records. Mean admission was 2.77 days. The incidence of adverse events was 59.9 per 100 patient days or 0.60 events per patient per day. The number of events detected by the Trigger Tool was related to duration of admission (r=0.70, P <0.0001) and risk of mortality on admission (r=0.50, P=0.0001) but not to age. The inter-rater agreement on detection of adverse events was good. Investigator One detected 66 adverse events while Investigator Two detected 93 events (kappa 0.63). Of the 61 events detected by both investigators, the agreement of classification of severity was very good (kappa 0.89). Of the 56 events rated similarly by both investigators, 13 (23%) were insignificant, 19 (34%) were minor, 17 (30%) were moderate, 4 (7%) were major and 3 (6%) were catastrophic. Only four adverse events had been reported voluntarily, of which two were detected using the Trigger Tool. Whereas the Trigger Tool is a simple, efficient and robust method, voluntary reporting is inadequate and captures very few adverse events in the intensive care unit environment.

Epidemiology of paediatric out-of-hospital cardiac arrest in Melbourne, Australia.

BACKGROUND: Previous studies of paediatric cardiac arrest have reported a low survival rate but there is limited data from Australia. We sought to determine the characteristics and outcomes of paediatric out-of-hospital cardiac arrest in Melbourne, Australia. METHODS: Between October 1999 and June 2007, all cases of out-of-hospital cardiac arrest attended by emergency medical services in Melbourne, Australia were entered into a database (the Victorian Ambulance Cardiac Arrest Registry). Data on patients aged less than 16 years in cardiac arrest on arrival of ambulance paramedics was analysed. RESULTS: There were 209 children in cardiac arrest on arrival of paramedics during the study period. Of these, resuscitation was not attempted in 16 children due to signs of definite death. Of the 193 children who had attempted resuscitation, 143 (74%) had an initial cardiac rhythm of asystole, 36 (18%) were in pulseless electrical activity and 14 (7%) were in ventricular fibrillation. There were 49 patients (25%) with return of spontaneous circulation at arrival to hospital of whom 14 (7%) survived to hospital discharge. Of 138 patients without return of a circulation, 120 were transported to hospital with continuing resuscitation and one survived (0.9%). Survival was higher in patients with an initial cardiac rhythm of ventricular fibrillation (5/14; 35%) compared with other rhythms (10/179; 4%), OR 9.38, 95% CI 2.64-33.2. CONCLUSIONS: Overall, 7.7% of paediatric patients with out-of-hospital cardiac arrest survive to leave hospital. Increased survival was seen if the initial cardiac rhythm was ventricular fibrillation. Survival was very rare (<1%) unless there was return of spontaneous circulation prior to hospital arrival.

Leukocytotic pseudohypoxaemia.

A case of hypoxaemia was concluded to be a pseudo-condition after investigation demonstrated that the hypoxaemia was not related to lung disease, but rather to the time expiring between obtaining and analysing blood samples and to a reduction in the magnitude of the patient's white cell count.

A comparison of Hickman line- and Port-a-Cath-associated complications in patients with solid tumours undergoing chemotherapy.

AIMS: To compare the complication rates of Hickman lines and Port-a-Caths in patients undergoing infusional chemotherapy for solid tumours. MATERIALS AND METHODS: A single institution retrospective analysis comparing complication rates for 30 Hickman lines and 33 Port-a-Caths inserted for chemotherapy in adults with solid tumours was carried out. RESULTS: Patients were well matched in terms of primary site and chemotherapy regimen. In both cases, over 85% were inserted radiologically under local anaesthetic. The total time in situ for Hickman lines and Port-a-Caths was 3539 days (median 83, range 6-585) and 5783 days (median 158, range 20-456), respectively. The complication rate for Hickman lines was 5.09/1000 catheter days, almost five times that for Port-a-Caths, with 1.04/1000 catheter days, a relative risk of 4.9 (confidence interval: 1.9-15.1, P=0.0003). Most (73%) complications occurred within 4 weeks of insertion. However, some arose much later: the range of time to complication was 1-304 days for Hickman lines and 1-132 days for Port-a-Caths. Infection was the most common complication, accounting for nine of 18 Hickman line complications and five of six Port-a-Cath complications, giving an overall infection rate of 2.54/1000 catheter days and 0.86/1000 catheter days, respectively. Additionally, Hickman lines had a 26% leakage rate or displacement rate, which did not occur at all in the Port-a-Cath group. Complications required the removal of 16 Hickman lines and five Port-a-Caths. The rate of removal was five times higher for Hickman lines (Hickman lines=4.52/1000 catheter days, Port-a-Caths=0.86/1000 catheter days, P=0.0027). Overall, the cost of Port-a-Caths was less than that of Hickman lines. CONCLUSION: In this study, Port-a-Caths were shown to be both safer and cheaper than Hickman lines for patients requiring infusional chemotherapy.

Tracheal ulceration and obstruction associated with flexible Bivona tracheostomy tubes.

An adjustable length tracheostomy tube, Bivona, which assumes a curve on insertion, has a tendency to straighten itself in situ. The straightening force, measured electronically, was maximal (0.21 Newton) when a tube was bent 90 degrees. We observed particular clinical disadvantages of these tubes--that of tracheal ulceration (1 case), distortion of soft tracheal graft tissue (1 case) and airway obstruction when the tip embedded into the tracheal wall (1 case).

Upper airway obstruction caused by ingestion of concentrated acetic acid.

We report a case of rapidly progressive severe upper airway obstruction in a small child caused by accidental ingestion of 80% acetic acid. Emergency cricothyrotomy was necessary after both endotracheal intubation and bag-valve-mask ventilation were not possible. Although intubation was eventually achieved, a tracheostomy was necessary. Toxin spilled over the anterior chest and abdomen caused third degree skin burns which required grafting. Mild liver dysfunction was observed. Complete recovery occurred.

Portal vein embolisation prior to hepatic resection for colorectal liver metastases and the effects of periprocedure chemotherapy.

Portal vein embolisation (PVE) is an effective method of increasing future liver remnant (FLR) but may stimulate tumour growth. The effect of periprocedure chemotherapy has not been established. 15 consecutive patients underwent PVE prior to hepatic resection for colorectal liver metastases with a FLR <30% of tumour-free liver (TFL). Liver and tumour volumes pre-PVE and 6 weeks post-PVE were calculated by CT or MRI volumetry and correlated with the periprocedure chemotherapy regimen. PVE increased the FLR from 18+/-5% of TFL to 27+/-8% post-PVE (p<0.01). Post-PVE chemotherapy did not prevent hypertrophy of the FLR but the volume increase with chemotherapy (median 89 ml, range 7-149 ml) was significantly reduced (median 135 ml, range 110-254 ml without chemotherapy) (p = 0.016). Tumour volume (TV) decreased in those receiving post-PVE chemotherapy (median TV decrease 8 ml, range -77 ml to +450 ml) and increased without chemotherapy (median TV increase 39 ml, range -58 ml to +239 ml). Of the 15 patients, eight underwent resection; four were not resected due to disease progression and three due to insufficient hypertrophy of the FLR. PVE increased the FLR by an average of 9% allowing resection in 50% of patients. Periprocedure chemotherapy did not prevent but did reduce hypertrophy. A trend towards tumour regression was observed.

Methylene blue for diagnosis of displaced atrial lines.

Methylene blue (aniline violet, tetra-methylthionine chloride) has several important uses in clinical medicine, including diagnosis of displaced central lines. After cardiac surgery, three infants with suspected displacement of direct atrial lines were given methylene blue. After injection of the dye into the atrial lines, bluish discolouration was identified in their chest drainage. Use of methylene blue in small amounts appears to be a safe and effective way of diagnosing extravasation of fluid from displaced central lines.

Corrosion of dental aluminium bronze in neutral saline and saline lactic acid.

OBJECTIVE: To compare the corrosion behaviours of two aluminium bronze, dental casting alloys during a standard immersion test and for immersion in neutral saline. METHODS: Cast specimens of aluminium bronzes with 1.4 wt% Fe (G) and 4 wt% Fe (N) were subject to progressively longer periods (up to in total 7 days) immersed in 0.1 M saline, 0.1 M lactic acid solutions and examined by scanning electron microscopy with EDX analysis. Immersion in 0.1M neutral saline was for 7 days. RESULTS: In the acidic solution, exposed interdendritic volumes in alloy N corroded completely away in 7 days with dissolution of Ni-enriched precipitate species as well as the copper-rich matrix. Alloy G begins to corrode more slowly but by a similar mechanism. The number density of an Fe-enriched species is insufficient to maintain a continuous galvanic potential to the copper matrix, and dissolution becomes imperceptible. In neutral saline solution, galvanic action alone caused pit-etching, without the dissolution of either precipitate species. SIGNIFICANCE: The upper limit for the total dissolution of metallic ions in the standard immersion test can be set at 200 microg cm(-2). Aluminium bronze dental alloys can be expected to release both copper and nickel ions into an acidic oral environment.

Reduction of paediatric in-patient cardiac arrest and death with a medical emergency team: preliminary results.

AIMS: To determine the impact of a paediatric medical emergency team (MET) on cardiac arrest, mortality, and unplanned admission to intensive care in a paediatric tertiary care hospital. METHODS: Comparison of the retrospective incidence of cardiac arrest and death during 41 months before introduction of a MET service with the prospective incidence of these events during 12 months after its introduction. Comparison of transgression of MET call criteria in patients who arrested and died before and after introduction of MET. RESULTS: Cardiac arrest decreased from 20 among 104 780 admissions (0.19/1000) to 4 among 35 892 admissions (0.11/1000) (risk ratio 1.71, 95% CI 0.59 to 5.01), while death decreased from 13 (0.12/1000) to 2 (0.06/1000) during these periods (risk ratio 2.22, 95% CI 0.50 to 9.87). Unplanned admissions to intensive care increased from 20 (SD 6) to 24 (SD 9) per month. The incidence of transgression of MET call criteria in patients who arrested decreased from 17 to 0 (risk difference 0.16/1000, 95% CI 0.09 to 0.24), and in those who died, decreased from 12 to 0 (risk difference 0.11/1000, 95% CI 0.05 to 0.18) after introduction of MET. CONCLUSIONS: Introduction of a medical emergency team service was coincident with a reduction of cardiac arrest and mortality and a slight increase in admissions to intensive care.

Obstructive jaundice secondary to neuroendocrine tumour in a patient with von Recklinghausen's disease.

Neurofibromatosis type 1 (NF1) is an autosomal dominant genetic disorder, with variable clinical manifestations and unpredictable course, associated with an increased incidence of various tumours. Plexiform neurofibromas are hallmark lesions of NF1; they are slow-growing tumours, which account for substantial morbidity, including disfigurement and functional impairment, and may even be life-threatening. Neuroendocrine tumours (NETs), a rare diverse group of neoplasms, are occasionally associated with neurofibromatosis. Pancreatic NETs are tumours with an incidence of less than 1/100 000 population/year and complex patterns of behaviour, which often need complicated strategies for optimal management. We present the case of a young adult with NF1, having a unique concurrence of plexiform neurofibroma involving the liver with an ampullary NET, and we discuss step by step the management in a specialist centre.

Prospective study of contrast-enhanced computed tomography, computed tomography during arterioportography, and magnetic resonance imaging for staging colorectal liver metastases for liver resection.

BACKGROUND: This study compared the value of contrast-enhanced helical computed tomography (CT), CT during arterioportography (CTAP), and contrast-enhanced magnetic resonance imaging (MRI) for staging patients with colorectal liver metastases. METHODS: One hundred and twenty patients with known or suspected colorectal liver metastases were evaluated prospectively. MRI and CTAP were performed within 3 weeks of CT in patients with potentially resectable tumours. Results of imaging were compared with findings at surgery, intraoperative ultrasonography and histological examination. RESULTS: Twenty patients were not considered for liver resection following CT. The remaining 100 patients underwent CT and CTAP, 85 of whom had CT, CTAP and MRI. The sensitivity and specificity were 73.0 and 96.5 per cent for CT, 87.1 and 89.3 per cent for CTAP, and 81.9 and 93.2 per cent for MRI. Positive predictive values were 89.7, 87.5 and 87.5 per cent respectively. Receiver-operator characteristic analysis gave an accuracy on a segment-by-segment analysis of 0.73 for CT, 0.87 for CTAP and 0.82 for MRI. Combining information from CT and CTAP, CT and MRI, or all three modalities, did not significantly increase the percentage of patients staged correctly (71, 72 and 76 per cent respectively). CONCLUSION: The diagnostic accuracy of spiral CT, MRI and CTAP was similar. Combining modalities did not improve accuracy.

Systematic review of radiological imaging for hepatocellular carcinoma in cirrhotic patients.

We systematically reviewed the evidence for determining the best radiological imaging for characterizing hepatocellular carcinoma (HCC) in cirrhotic patients in 997 articles between 1995 and 2001. We selected only prospective and retrospective cohorts of patients, excluding both case reports and studies without separate data on HCC. Only 29 studies, comprising 918 patients, fulfilled the inclusion criteria: 10 used the explanted liver as the reference standard of diagnosis. All except one, either found no statistically significant difference between imaging modalities or had no direct comparison of sensitivity between different modalities of imaging; 16 studies evaluated HCC among cirrhotic patients and had biopsy or imaging as the reference standard for diagnosis. However, no one imaging technique was shown to be superior. In two studies, data of a HCC subgroup was derived from the studies evaluating different kinds of focal hepatic lesions. No conclusion could be drawn because of the small sample size. One study addressed the issue of therapeutic impact. The evidence for choosing the best modality of imaging for characterizing HCC in cirrhotic patients is inadequate. Large multicentre studies with defined reference standards for diagnosis, and studies evaluating therapeutic impact are needed.

Cardiovascular, haematological and neurological effects of the venom of the Papua New Guinean small-eyed snake (Micropechis ikaheka) and their neutralisation with CSL polyvalent and black snake antivenoms.

Cardiovascular and haematological effects of venom of the small-eyed Snake (Micropechis ikaheka) were examined in ventilated anaesthetised piglets. Neurotoxic effects were examined in chick biventer cervicis nerve-muscle preparations. Immunoreactivity of venom was tested against the monovalent antivenom components in a CSL Ltd Venom Detection Kit. Neutralisation was tested in vivo and in vitro with CSL Ltd polyvalent snake and Black Snake (Pseudechis australis) antivenoms. Venom in 0.1% bovine serum albumin in saline was infused into piglets in doses 1-2000 microg/kg. Pulmonary hypertension (P= 0.0007) and depression of cardiac output (P= 0.002) were observed up to 3 h after 150-160 microg/kg. The concentration of plasma free-haemoglobin increased more than 50-fold, indicating haemolysis. Neither coagulopathy nor thrombocytopenia occurred. Creatine phosphokinase and serum potassium levels did not increase suggesting absence of acute rhabdomyolysis. The venom caused post-synaptic neurotoxicty. Immunoreactivity of venom with Black Snake antivenom was observed at very high venom concentrations. Cardiovascular effects were absent and haemolysis was less after venom was pre-incubated at 37 degrees C for 30 min with polyvalent antivenom. Neutralisation by Black Snake antivenom was less effective. The neurotoxicity was neutralised by polyvalent or Black Snake antivenoms. Human envenomation may be treated with CSL Ltd polyvalent snake antivenom.