Simple and statistically sound recommendations for analysing physical theories

Physical theories that depend on many parameters or are tested against data from many different experiments pose unique challenges to statistical inference. Many models in particle physics, astrophysics and cosmology fall into one or both of these categories. These issues are often sidestepped with statistically unsound ad hoc methods, involving intersection of parameter intervals estimated by multiple experiments, and random or grid sampling of model parameters. Whilst these methods are easy to apply, they exhibit pathologies even in low-dimensional parameter spaces, and quickly become problematic to use and interpret in higher dimensions. In this article we give clear guidance for going beyond these procedures, suggesting where possible simple methods for performing statistically sound inference, and recommendations of readily-available software tools and standards that can assist in doing so. Our aim is to provide any physicists lacking comprehensive statistical training with recommendations for reaching correct scientific conclusions, with only a modest increase in analysis burden. Our examples can be reproduced with the code publicly available at Zenodo.

Search for B^{+}→K^{+}νν[over ¯] Decays Using an Inclusive Tagging Method at Belle II

A search for the flavor-changing neutral-current decay B^{+}→K^{+}νν[over ¯] is performed at the Belle II experiment at the SuperKEKB asymmetric energy electron-positron collider. The data sample corresponds to an integrated luminosity of 63  fb^{-1} collected at the ϒ(4S) resonance and a sample of 9  fb^{-1} collected at an energy 60 MeV below the resonance. Because the measurable decay signature involves only a single charged kaon, a novel measurement approach is used that exploits not only the properties of the B^{+}→K^{+}νν[over ¯] decay, but also the inclusive properties of the other B meson in the ϒ(4S)→BB[over ¯] event, to suppress the background from other B meson decays and light-quark pair production. This inclusive tagging approach offers a higher signal efficiency compared to previous searches. No significant signal is observed. An upper limit on the branching fraction of B^{+}→K^{+}νν[over ¯] of 4.1×10^{-5} is set at the 90% confidence level.

Baseline Urinary Phytoestrogen Levels and the Natural History of Untreated, Localised Prostate Cancer in a British Population

Aim

To determine whether urinary concentrations of phytoestrogens are associated with the rate of disease progression in men with untreated, localised prostate cancer.

Patients and methods

Patients with untreated, localised prostatic adenocarcinoma on a prospective clinical study of active surveillance had urine samples collected at baseline. Patients underwent monitoring with serial PSA levels and repeat octant prostate biopsies. Disease progression was defined as either adverse histology on repeat biopsy (primary Gleason grade ≥4, or >50% positive cores) or radical treatment for PSA velocity >1 ng/mL/year. Time to disease progression was analysed with respect to baseline urinary levels of genistein, enterolactone, daidzein and equol, assayed using liquid chromatography/tandem mass spectrometry.

Results

191 patients were evaluable, with a median follow-up of 2.5 years. 71 patients experienced disease progression. No significant association was seen between time to disease progression and baseline urinary levels of daidzein (p=0.85), genistein (p=0.81), enterolactone (p=0.085) or equol (p=0.33). No significant association was seen between adverse histology on repeat biopsy and urinary levels of either daidzein (p=0.85), genistein (p=0.58), enterolactone (p=0.88) or equol (p=0.71). There was no significant correlation between PSA velocity and urinary levels of daidzein (p=0.90), genistein (p=0.98), enterolactone (p=0.10) or equol (p=0.60).

Conclusion

These data do not support the hypothesis that phytoestrogens prevent disease progression in men with localised prostate cancer.

Greenhouse-gas emissions from stockpiled and composted dairy-manure residues and consideration of associated emission factors

Emissions from stockpiled pond sludge and yard scrapings were compared with composted dairy-manure residues blended with shredded vegetation residues and chicken litter over a 5-month period at a farm in Victoria (Australia). Results showed that methane emissions occurred primarily during the first 30–60 days of stockpiling and composting, with daily emission rates being highest for stockpiled pond sludge. Cumulated methane (CH4) emissions per tonne wet feedstock were highest for stockpiling of pond sludge (969 g CH4/t), followed by composting (682 g CH4/t) and stockpiling of yard scrapings (120 g CH4/t). Sizeable nitrous oxide (N2O) fluxes were observed only when temperatures inside the compost windrow fell below ~45−50°C. Cumulated N2O emissions were highest for composting (159 g N2O/t), followed by stockpiling of pond sludge (103 g N2O/t) and yard scrapings (45 g N2O/t). Adding chicken litter and lime to dairy-manure residues resulted in a very low carbon-to-nitrogen ratio (13 : 1) of the composting mix, and would have brought about significant N2O losses during composting. These field observations suggested that decisions at composting operations, as in many other businesses, are driven more by practical and economic considerations rather than efforts to minimise greenhouse-gas emissions. Total greenhouse-gas emissions (CH4 + N2O), expressed as CO2-e per tonne wet feedstock, were highest for composting (64.4 kg), followed by those for stockpiling of pond sludge (54.5 kg) and yard scraping (16.3 kg). This meant that emissions for composting and stockpiling of pond sludge exceeded the new Australian default emission factors for ‘waste composting’ (49 kg). This paper proposes to express greenhouse-gas emissions from secondary manure-management systems (e.g. composting) also as emissions per tonne wet feedstock, so as to align them with the approach taken for ‘waste composting’ and to facilitate the development of emission-reduction methodologies for improved manure management at the farm level.

Sampling frequency affects estimates of annual nitrous oxide fluxes

Quantifying nitrous oxide (N₂O) fluxes, a potent greenhouse gas, from soils is necessary to improve our knowledge of terrestrial N₂O losses. Developing universal sampling frequencies for calculating annual N₂O fluxes is difficult, as fluxes are renowned for their high temporal variability. We demonstrate daily sampling was largely required to achieve annual N₂O fluxes within 10% of the ‘best’ estimate for 28 annual datasets collected from three continents—Australia, Europe and Asia. Decreasing the regularity of measurements either under- or overestimated annual N₂O fluxes, with a maximum overestimation of 935%. Measurement frequency was lowered using a sampling strategy based on environmental factors known to affect temporal variability, but still required sampling more than once a week. Consequently, uncertainty in current global terrestrial N₂O budgets associated with the upscaling of field-based datasets can be decreased significantly using adequate sampling frequencies.

Improving the statistical preparation for measuring soil N2O flux by closed chamber

Nitrous oxide emissions from soil are known to be spatially and temporally volatile. Reliable estimation of emissions over a given time and space depends on measuring with sufficient intensity but deciding on the number of measuring stations and the frequency of observation can be vexing. The question of low frequency manual observations providing comparable results to high frequency automated sampling also arises. Data collected from a replicated field experiment was intensively studied with the intention to give some statistically robust guidance on these issues. The experiment had nitrous oxide soil to air flux monitored within 10 m by 2.5 m plots by automated closed chambers under a 3h average sampling interval and by manual static chambers under a three day average sampling interval over sixty days. Observed trends in flux over time by the static chambers were mostly within the auto chamber bounds of experimental error. Cumulated nitrous oxide emissions as measured by each system were also within error bounds. Under the temporal response pattern in this experiment, no significant loss of information was observed after culling the data to simulate results under various low frequency scenarios. Within the confines of this experiment observations from the manual chambers were not spatially correlated above distances of 1m. Statistical power was therefore found to improve due to increased replicates per treatment or chambers per replicate. Careful after action review of experimental data can deliver savings for future work.

Improving patient care--the first year in a dedicated surgical assessment unit

A surgical assessment unit (SAU) was established in October 2009 at the Mid-Western Regional Hospital. We assessed this servic in its initial year and compared it to Emergency Department (ED) services. We audited SAU and ED databases and theatre logbooks from November 2009 to October 2010. 1949 patients were referred to the SAU and 857 patients were admitted (44%). Only 44 SAU patients (6%) waited more than 6 hours for a bed compared to 828 patients (68%) admitted through the ED. SAU patients who required emergency surgery had a shorter waiting time before theatre (37 (18.6%) vs 9(6%) waited less than 6 hours, p < 0.05). To summarise, we found that almost 2,000 patients who would otherwise have presented to the ED were referred to the SAU. Waiting times for admission and theatre were significantly shorter. Further resource allocation could expand the service and improve it further, by diverting more patients from the ED.

Demands for vascular access in a renal dialysis unit: Implications for a regional vascular unit

BACKGROUND

The development of regional dialysis units and the expanding indications for dialysis has led to increased demand for vascular access surgery. Consequently, the provision and maintenance of access, and the management of related complications has created a considerable burden on vascular surgical units in hospitals providing renal replacement therapy (RRT).

AIMS

The objectives of our study were to review our experience with a variety of vascular access modalities for haemodialysis and to quantify the associated surgical workload.

METHODS

We reviewed our experience in a consecutive group of dialysis patients who had access surgery for RRT in a regional hospital setting.

RESULTS

Between January 1995 and January 2000, 69 patients entered the long-term dialysis programme in the Mid-Western region (population = 320,000). Of the 158 procedures performed, 138 (87%) were for access creation, and 20 (13%) related to access revision procedures. Twenty patients (29%) developed a total of 30 access related complications. Vascular access procedures accounted for 10% of the vascular surgical workload (1598 procedures) in the five-year period.

CONCLUSION

Vascular access is an important part of the haemodialysis services and surgical expertise should be available at local level to cope with likely demand.

3-D numerical simulation of blood flow through models of the human aorta

A Spiral Computerized Tomography (CT) scan of the aorta were obtained from a single subject and three model variations were examined. Computational fluid dynamics modeling of all three models showed variations in the velocity contours along the aortic arch with differences in the boundary layer growth and recirculation regions. Further down-stream, all three models showed very similar velocity profiles during maximum velocity with differences occurring in the decelerating part of the pulse. Flow patterns obtained from transient 3-D computational fluid dynamics are influenced by different reconstruction methods and the pulsatility of the flow. Caution is required when analyzing models based on CT scans.

Accuracy of admitting diagnosis in acute surgical patients by non consultant hospital doctors

The incidence of accurate diagnosis made by non-consultant hospital doctors (NCHDs) is unknown in acute surgical admissions. There is a common assumption that reliance is made on excessive and inappropriate investigations. The aim of study was to assess the accuracy of admitting diagnosis by the NCHDs and the appropriateness of radiological investigations ordered. Data were collected on 100 consecutive acute surgical admissions. A final diagnosis was made in all the patients. 79 patients had accurate initial diagnosis (NCHDs). 23 scans were performed which confirmed the initial diagnosis. Out of 21 initial inaccurate diagnoses, final diagnosis was made on repeated clinical examination in 10, on imaging alone in 5 and by endoscopy or surgery in the remaining 6 patients. 11 patients had scans and 7 were appropriate. We conclude that 79% of diagnoses made by NCHDs are the accurate final diagnoses. The utilization of diagnostic modalities especially radiological imaging is highly appropriate. Our study suggests that the physical presence of a consultant on site may not lead to significant improvement to the delivery of health care to the Irish population.

Transcendental health care ethics: beyond the medical model

Recent health care ethics literature is heavily weighted in favor [of] examining problems associated with technological and other advances. This article challenges such a narrow focus of inquiry, maintaining that a broader conceptualization of the problems in health care is warranted. In part, this problem of focus can be attributed to the labeling of the field of study as "medical ethics" which reinforces a medical model approach to the exploration of problems. This particular perspective has proven inadequate for the purpose of describing the moral problems associated with health care. The health care professions, including medicine, have responsibilities toward individuals but also have wider responsibilities to society in general. These responsibilities are reflected in their codes of ethics. Thus, the purpose of moral philosophy with regard to health care ethics issues should not be constrained to "medical ethics" but should include broader appraisals of health care and the health care context.

Understanding the underlying causes of chronic leg ulceration

Leg ulcers are debilitating and have a significant negative impact on patients' quality of life. It is particularly important to understand the underlying causes of leg ulcers that are described as 'slow to heal' to ensure they are managed effectively.

Synovial cyst of the hip joint: an unusual cause of a pulsating groin mass

Synovial cysts of the hip joint occur most frequently in patients with rheumatoid arthritis (1). Despite the increasing frequency of arthroplasty of rheumatoid hips, case reports documenting synovial cysts remain extremely rare. This case report emphasizes the need for the surgeon to include a synovial cyst in the differential diagnosis of a painless groin mass, particularly in patients with rheumatoid arthritis.

Treatment of surgical patients is evidence-based

OBJECTIVES

To assess the type of evidence that supported our management of surgical patients.

DESIGN

Retrospective audit.

SETTING

Teaching hospital, Republic of Ireland.

PATIENTS

All 222 patients admitted by two surgical teams during one month. Patients admitted for diagnostic procedures were included if they were treated as a result.

MAIN OUTCOME MEASURES

Diagnosis and treatment were established from the notes. Evidence for each intervention was then sought in MEDLINE 1986-1999, Best Evidence 1991-1999, and the Cochrane Database of Systematic Reviews Issue 3, 1999, and graded into one of five categories: systematic review, meta-analysis, randomised controlled trial, prospective study, or retrospective study.

RESULTS

Treatment was supported by systematic review in 14, by meta-analysis in 12, by randomised controlled trial in 75, by prospective studies in 55, by retrospective studies in 58, and by no evidence in 8.

CONCLUSIONS

Everyday surgical practice in our unit is supported by good quality evidence from recent publications.

Milestones in athletic trainer certification

OBJECTIVE

To summarize the history of athletic trainer certifaction.

BACKGROUND

The single most significant public pronouncement a professional society or organization can bestow upon an individual is certification. One of the underlying goals of professional societies or organizations that certify individuals is to promote the public's reliance on the credential and the individuals who hold that credential. In this paper, I will identify the significant milestones the National Athletic Trainers' Association (NATA) and the NATA Board of Certification (NATABOC) have achieved for the athletic training profession, promoting and sustaining the public's reliance on the certified athletic trainer.

DESCRIPTION

This paper presents the significant milestones in the certification of athletic trainers by the NATA and the NATABOC.

ADVANTAGES

The milestones related to athletic trainer certification that I present in this paper will enhance the reader's understanding of the underlying reasons for the initiation of athletic trainer certification and the development and recognition of the athletic training profession as a credentialing agency for the athletic training profession.

Infrared optoelectronic volumetry, the ideal way to measure limb volume

OBJECTIVES

The aim of the study was to compare a novel infrared optoelectronic system (Perometer) of limb volume measurement with water displacement and two indirect measurement techniques.

DESIGN

A prospective experimental study.

METHODS

In 10 healthy male volunteers (20 limbs) we compared limb volume measurements obtained by water displacement, infrared perometry, the disc model method and the frustrum method. In a further 17 patients with swollen limbs due to lymphatic (9 limbs) or venous (11 limbs) disease, perometry was compared to the disc model method and the frustrum method only.

RESULTS

In normal limbs, mean +/- S.D. limb volume using water displacement was 1802 +/- 268 ml. Perometer values agreed almost exactly (1809 +/- 262 ml, r = 0.97, variation +/- 7% by limits of agreement) but both the disc (1923 +/- 306 ml, r = 0.90, variation +/- 14%) and frustrum (1905 +/- 372 ml, r = 0.72, variation +/- 28%) methods significantly overestimated limb volumes (p < 0.05 (ANOVA, Fisher's Least Significant Difference)). In diseased limbs perometer, disc method and frustrum method results were 2415 +/- 995 ml, 2494 +/- 969 ml, and 2413 +/- 870 ml representing variation of +/- 17% and +/- 23% for disc method and frustrum method respectively compared to perometry.

CONCLUSIONS

Perometry is a novel, extremely accurate and easy method for assessing limb volume. It provides more accurate results than traditional indirect measurement of limb volume and potentially is a very useful clinical and research tool.

Alpha-1-antichymotrypsin is an effective inhibitor of pancreatitis-induced lung injury

BACKGROUND

Pancreatitis-induced adult respiratory distress syndrome (ARDS) may result from an imbalance between leucocyte proteases, produced by infiltrating neutrophils, and endogenous protease inhibitors.

OBJECTIVE

The aim of this study was to evaluate the role of recombinant alpha-1-antichymotrypsin (rACT P3-P3'), an endogenous serine protease inhibitor, in ameliorating lung injury associated with pancreatitis.

DESIGN

Sprague-Dawley rats were randomly divided into control (saline infusion) and pancreatitis groups, which were treated immediately with saline or rACT P3-P3' (50 mg/kg body weight).

METHODS

Myeloperoxidase (MPO) was employed as a monitor of neutrophil traffic in the lung, and wet-dry lung weights as a measure of pulmonary endothelial permeability. Lungs were also evaluated histologically.

RESULTS

Caerulein (5 micrograms/kg body weight/h) induced pancreatitis in all animals, with an increase in serum amylase from 1851 +/- 208 IU (control) to 5198 +/- 924 IU (pancreatitis), P < 0.05. Pancreatitis caused a significant increase in MPO activity (7.8 +/- 1.1 units compared with 2.08 +/- 0.5 units in controls, P < 0.001) and wet-dry lung weight ratios (12.8 +/- 3.3 compared with 3.2 +/- 0.1 in controls, P < 0.001), indicating significant pulmonary neutrophil influx and microvascular leakage, respectively. These increases in MPO activity and wet-dry ratios were decreased in the pancreatitis group treated with rACT P3-P3' (MPO 4.68 +/- 0.7 units, wet-dry ratio 4.2 +/- 0.5, P < 0.05 compared with the untreated pancreatitis group).

CONCLUSION

These data support the hypothesis that deficient endogenous protease inhibition may be responsible for the neutrophil-mediated lung injury observed in pancreatitis and suggest that there may be a therapeutic role for recombinant protease inhibitors such as alpha-1 antichymotrypsin.

An assessment of the Coulter VCS automated differential counter scatterplots in the recognition of specific acute leukaemia variants

The Coulter VCS is an automated differential counter, which derives a five-part differential count on the basis of differences in cell volume, high frequency conductivity and light scatter. A printed scatterplot relating volume and scatter is readily obtained. Other instruments which use automated cytochemistry can distinguish between AML and ALL, and between AML variants. It was our impression that the Coulter VCS might also be capable of such distinction on the basis of the scatterplot patterns. We therefore collected scatterplots produced by Coulter VCS analysis of peripheral blood from 63 patients presenting with acute leukaemia. The scatterplots were inspected and six basic patterns identified. The scatterplots were inspected and six basic patterns identified. The scatterplots could be reproducibly sorted into pattern-specific groups without knowledge of the diagnosis. Precise leukaemic diagnoses were made routinely by conventional morphology, cytochemistry and immunophenotyping. A comparison was then made with the scatterplot patterns. The 51 cases of AML produced examples of all six patterns. The nine cases of ALL produced only three patterns. These were shared with cases of AML, and two were also shared with the three cases of acute mixed lineage leukaemia. Thus, three of the six patterns were specific for AML, whereas no pattern was specific for ALL or acute mixed lineage acute leukaemia. One pattern was produced only by the three cases of AML M6, and another was produced only by five of the 25 cases of primitive (M0 and M1) AML.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdominal aortic aneurysm in the Irish population: a familial screening study

A pilot screening programme was undertaken in Ireland to determine the incidence of abdominal aortic aneurysm (AAA) (diameter 3 cm or greater) in the siblings of 120 patients known to have AAA. There were 621 siblings; 270 of them were dead, 32 were over 80 years old and 85 lived outside Ireland, leaving 234 under 80 years of age still living in Ireland who were invited to attend for ultrasonographic screening. Of the 270 siblings who had died, 102 were women and 168 men; eight men (4.8 per cent) had died from ruptured AAA. Only 125 (53.4 percent) of the 234 siblings agreed to participate in the screening programme, 60 brothers from 31 families and 65 sisters from 35 families. Fifteen (12.0 per cent) of the 125 siblings had an AAA (median size 4.2 (range 3.1-6.8) cm), 13 (22 per cent) of the 60 male siblings and two (3 per cent) of the 65 female siblings. The prevalence of AAA among siblings was not affected by the age or sex of the patient with aneurysm. Seven of the 14 male siblings with hypertension had an AAA, compared with only six of the 46 who were normotensive (P = 0.01). The high incidence of AAA in brothers of affected patients highlights the need to counsel this group on their risk of aneurysm. The relatively low participation rate by siblings in this screening programme indicates that a hospital-based unit is unlikely to be effective in recruiting all patient siblings at risk from an AAA.

Nursing advocacy: an ethic of practice

Advocacy is an important concept in nursing practice; it is frequently used to describe the nurse-client relationship. The term advocacy, however, is subject to ambiguity of interpretation. Such ambiguity was evidenced recently in criticisms levelled at the nursing profession by hospital ethicist Ellen Bernal. She reproached nursing for using 'patient rights advocate' as a viable role for nurses. We maintain that, for nursing, patient advocacy may encompass, but is not limited to, patients rights advocacy. Patient advocacy is not merely the defence of infringements of patient rights. Advocacy for nursing stems from a philosophy of nursing in which nursing practice is the support of an individual to promote his or her own well-being, as understood by that individual. It is an ethic of practice.

The need to retrieve the dropped stone during laparoscopic cholecystectomy

The effect of bile and gallstones on the peritoneal cavity was evaluated in an experimental animal study. Ninety male Sprague-Dawley rats were randomly allocated to one of six groups (n = 15). Groups 1 to 3 received an intraperitoneal injection (2 mL) of saline, sterile bile, and infected bile, respectively. Groups 4 to 6 underwent a lower midline abdominal incision (3 to 5 mm). In groups 4 and 5, a single gallstone (< 3 mm diameter) was placed in the right upper quadrant and, after closure of the wound, the animals were injected with sterile bile and infected bile, respectively. Group 6 animals underwent laparotomy alone, followed by injection of sterile saline (2 mm). All animals were killed at 4 weeks and the peritoneal cavity was carefully examined. No intra-abdominal lesions were noted in groups 1 to 3. Adhesions were noted in 11 (73%) and 10 (67%) animals of groups 4 and 5, respectively. Two intra-abdominal abscesses were noted in group 4 animals. No intra-abdominal lesions were noted in any group 6 animals. This study suggests that bile in combination with gallstones in the peritoneal cavity is associated with an increased risk of intra-abdominal adhesion formation and possible abscess formation, and that every attempt should be made to retrieve stones lost during cholecystectomy.

How much heparin? A simple in vitro test

A simple in vitro test to calculate the dose of heparin required to achieve optimal in vivo anticoagulation during surgery has been assessed in 15 patients who subsequently underwent vascular surgery. Heparin was added to four aliquots of patients blood in vitro to give five solutions with heparin concentrations ranging from 0-0.8 units/ml of plasma. The activated partial thromboblastic times (APTT) of each of these samples was then measured and the natural log (ln) of the APTT calculated. The natural log of the APTT in vitro was then plotted against the in vitro heparin concentration. From this linear correlation the concentration of heparin required to achieve an APTT 2.5 times the normal in vitro (Hc) for the 15 different patients was calculated and ranged from 0.4-0.75 units/ml (median 0.47). Based on an estimate of the plasma volume (PV), the bolus dose of heparin given intravenously to each patient to produce an equivalent anticoagulant response in vivo was calculated (Hc x PB). Heparin boli administered ranged from 1000-2000 units (median 1500). The mean in vivo APTT achieved was 77% of the predicted value (range 62%-123%). Such an estimation of an in vivo response, by means of an in vitro test, should help to more accurately predict the effects of heparin in vivo and individualise anticoagulation dosage.

Spinal cord perfusion pressure in dogs after control of proximal aortic hypertension during thoracic aortic cross-clamping with esmolol or sodium nitroprusside

BACKGROUND

Spinal cord perfusion pressure may be reduced when sodium nitroprusside is used to control proximal aortic hypertension during thoracic aortic clamping. The effect of esmolol infusion on spinal cord perfusion pressure during thoracic aortic clamping is unknown. This study compares spinal cord perfusion pressure following control of proximal hypertension with either sodium nitroprusside or esmolol during thoracic aortic clamping.

METHODS

The thoracic aorta was cross-clamped for 30 min in 18 dogs anesthetized with halothane. A control group (n = 6) received no treatment of proximal hypertension during cross-clamping. In two other groups, proximal arterial pressure was controlled (100 mmHg) by infusion of either sodium nitroprusside (n = 6) or esmolol (n = 6). Brachial and femoral arterial pressures, spinal cord perfusion pressure, pulmonary artery occlusion, central venous pressures, and cardiac output were monitored. Neurologic assessment was performed 24 h following surgery.

RESULTS

Femoral arterial pressure was lower with nitroprusside (14 +/- 3 mmHg) compared to esmolol (24 +/- 4 mmHg) after 15 min of aortic cross-clamping. Cerebrospinal fluid pressure increased during aortic cross-clamping in the sodium nitroprusside group (from 7 +/- 5 to 16 +/- 6 mmHg) but not in esmolol or control groups. Spinal cord perfusion pressure was lower with nitroprusside at 15 min of aortic cross-clamping (2 +/- 4 mmHg) compared to control (15 +/- 7 mmHg) and esmolol groups (17 +/- 11 mmHg). Esmolol infusion reduced cardiac output and increased ventricular filling pressures compared to control and nitroprusside groups.

CONCLUSIONS

Esmolol was associated with greater spinal cord perfusion pressure, but adverse hemodynamic effects, when compared with nitroprusside during thoracic aortic cross-clamping. When only surviving dogs (4 control, 5 esmolol, 6 nitroprusside) are considered, the incidence of neurologic deficit was greater in nitroprusside-treated dogs than in either control or esmolol-treated dogs. No difference in outcome was present when all dogs are considered.

Ankle fracture is associated with prolonged venous dysfunction

Leg swelling is a significant problem following ankle fracture. Venous pump function and femoral and popliteal venous patency were assessed prospectively in 26 patients with ankle fractures requiring open reduction, internal fixation and immobilization in plaster. Functional venous volume, venous filling index (VFI), ejection volume fraction (EVF) and residual volume fraction (RVF) were measured using air plethysmography at 5 days and at 6, 12 and 18 weeks after fracture. The uninjured leg was used as a control. Popliteal and femoral venous patency was determined using duplex ultrasonography. No patient developed deep vein thrombosis during the study. At 5 days after fracture there was a significant reduction in mean(s.d.) EVF, 18.2(12.1) versus 55.9(19.5) per cent, and increase in RVF, 87.0(14.3) versus 42.5(22.2) per cent (both P < 0.001). Analogous values were similar at 6 weeks, EVF 28.5(21.2) versus 55.6(21.9) per cent, RVF 82.2(16.8) versus 48.5(23.8) per cent (both P < 0.001), and at 12 weeks, EVF 39.1(16.0) versus 60.3(14.9) per cent, RVF 64.7(18.8) versus 38.8(13.2) per cent (both P < 0.001). However, by 18 weeks there was no significant difference in venous function between fractured and control limbs. It is concluded that there is a significant and prolonged impairment in venous pump function following ankle fracture.

Aprotinin: the ideal anti-coagulant?

The serine proteinase inhibitor, aprotinin, significantly reduces transfusion requirements during open heart surgery. Whether this benefit is associated with an increased tendency to thrombosis has not been studied. We investigated the effect of aprotinin in an experimental arterial thrombosis model. In 17 male Sprague-Dawley rats, the infrarenal aorta was replaced with 1.0-mm diameter PTFE grafts of varying lengths. The time to graft occlusion, recorded by palpation, Doppler ultrasound and a distal bleeding test, was 20.2 +/- 1.8 min, 35.8 +/- 6.1 min and 43.7 +/- 6.6 min for grafts of 10, 7.5 and 5.0 mm respectively (r = -0.98, p less than 0.05). Following PTFE graft placement 24 Sprague-Dawley rats were given saline (n = 6), aprotinin (n = 6), heparin (n = 6), and heparin + aprotinin (n = 6). The time to occlusion was significantly prolonged in the aprotinin group (71.7 +/- 20.4 min vs. 20.2 +/- 1.8 min, p less than 0.05). The time to thrombosis for heparin + aprotinin and heparin alone was also significantly prolonged (p less than 0.05). Prothrombin times (PT) were 21.9 +/- 3.0 s for control, 29.4 +/- 6.2 s for aprotinin, 40.7 +/- 2.5 s for heparin and 39.9 +/- 14.5 s for heparin + aprotinin (p less than 0.05 vs. control for all values). Bleeding time was not prolonged with aprotinin (3.0 +/- 0.9 min vs. 2.9 +/- 0.7 min). The bleeding time was 18.9 +/- 4.1 min for heparin + aprotinin and 22.5 +/- 2.3 min for heparin alone (p less than 0.05 vs. control for both values).(ABSTRACT TRUNCATED AT 250 WORDS)

Peritoneum-preserving radical nephrectomy in a patient on continuous ambulatory peritoneal dialysis

We describe a pararectus retroperitoneal approach for radical nephrectomy in a patient on chronic ambulatory peritoneal dialysis. This approach allows early ligation of the renal pedicle pre-operatively and immediate resumption of peritoneal dialysis post-operatively.

Laparoscopic cholecystectomy: a hundred consecutive cases

Laparoscopic cholecystectomy is a new, minimaly invasive technique for removing the gallbladder which has several advantages over the traditional laparotomy cholecystectomy. We reviewed our initial experience with 100 consecutive patients in whom laparoscopic cholecystectomy was attempted. The indications for operation were biliary colic, chronic cholecystitis, acute gallbladder and gallstone pancreatitis. Laparoscopic cholecystectomy was successfully performed in 87 patients. Anaesthesia time was 144 +/- 52 min. There was no mortality while overall morbidity was 14%. One patient had a retained common bile duct stone. Postoperative hospital stay was 4.1 +/- 2.2 days and the mean time to full activity in a random sample of 25 patients was 13.7 +/- 11.7 days. Laparoscopic cholecystectomy is a safe effective procedure which removes the gallbladder. We suggest that this technique be considered in all patients undergoing cholecystectomy.