Electronic structure and transport of a carbon chain between graphene nanoribbon leads

The electronic structure and transport property of a carbon chain between two graphene nanoribbon leads are studied using an ab initio tight-binding (TB) model and Landauer's formalism combined with a non-equilibrium Green's function. The TB Hamiltonian and overlap matrices are extracted from first-principles density functional calculations through the quasi-atomic minimal basis orbital scheme. The accuracy of the TB model is demonstrated by comparing the electronic structure from the TB model with that from first-principles density functional theory. The results of electronic transport on a carbon atomic chain connected to armchair and zigzag graphene ribbon leads, such as different transport characters near the Fermi level and at most one quantized conductance, reveal the effect of the electronic structure of the leads and the scattering from the atomic chain. In addition, bond length alternation and an interesting transmission resonance are observed in the atomic chain connected to zigzag graphene ribbon leads. Our approach provides a promising route to quantitative investigation of both the electronic structure and transport property of large systems.

Neurotrauma and the RUB: where tragedy meets ethics and science

Decompressive craniectomy is a technically straightforward procedure whereby a large section of the cranium is temporarily removed in cases where the intracranial pressure is dangerously high. While its use has been described for a number of conditions, it is increasingly used in the context of severe head injury. As the use of the procedure increases, a significant number of patients may survive a severe head injury who otherwise would have died. Unfortunately some of these patients will be left severely disabled; a condition likened to the RUB, an acronym for the Risk of Unacceptable Badness. Until recently it has been difficult to predict this outcome, however an accurate prediction model has been developed and this has been applied to a large cohort of patients in Western Australia. It is possible to compare the predicted outcome with the observed outcome at 18 months within this cohort. By using predicted and observed outcome data this paper considers the ethical implications in three cases of differing severity of head injury in view of the fact that it is possible to calculate the RUB for each case.

Structures of Pb(n) (n = 21-30) clusters from first-principles calculations

Neutral lead clusters Pb(n) (n = 21-30) were studied using a genetic algorithm (GA)/tight-binding (TB) search combined with density functional theory (DFT)-Perdew-Burke-Ernzerhof (PBE) calculations. The calculated results show that the Pb(n) (22 ≤ n ≤ 30) clusters favor endohedral cage structures with two (Pb(22 - 26)) or three (Pb(27 - 30)) endohedral atoms. The binding energies, stabilities, and highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps of the Pb(n) clusters were also discussed. The results from our calculations also indicate that Pb(24) and Pb(28) are especially stable clusters compared with their neighbors.

Risk factors and outcomes of high-dependency patients requiring intensive care unit admission: a nested case-control study

Intermediate-care or high-dependency units can provide a level of care that lies between the intensive care unit (ICU) and general ward, but the patients who are most likely to benefit from such level of care remains uncertain. This nested case-control study assessed the incidence and risk factors of high-dependency patients requiring ICU admission and whether these admissions were associated with a worse outcome when compared to other emergency ICU admissions. Seventy-seven consecutive high-dependency patients requiring ICU admission (cases) were compared with 77 patients who did not require ICU admission (controls) and also 928 emergency ICU admissions from other areas. The incidence of high-dependency patients requiring ICU admission was 6.7% (95% confidence interval 5.3 to 8.2). High-dependency admissions from the ward (odds ratio 4.46, 95% confidence interval 1.55 to 12.78) or emergency department (odds ratio 4.48, 95% confidence interval 1.54 to 13.0) and a need for concurrent non-invasive ventilation, inotrope infusion and acute kidney injury (odds ratio 14.90, 95% confidence interval 3.79 to 58.3) was associated with a higher risk of ICU admission. Hospital mortality of the high-dependency patients requiring ICU admission was not significantly different from other emergency ICU admissions (odds ratio 1.08, 95% confidence interval 0.55 to 2.11). In summary, high-dependency patients requiring ICU admission were uncommon unless they had multi-organ failure and their hospital mortality was not significantly different from other emergency ICU admissions.

Incidence and risk factors for fatal pulmonary embolism after major trauma: a nested cohort study

BACKGROUND

Venous thromboembolism is common after major trauma. Strategies to prevent fatal pulmonary embolism (PE) are widely utilized, but the incidence and risk factors for fatal PE are poorly understood.

METHODS

Using linked data from the intensive care unit, trauma registry, Western Australian Death Registry, and post-mortem reports, the incidence and risk factors for fatal PE in a consecutive cohort of major trauma patients, admitted between 1994 and 2002, were assessed. Non-linear relationships between continuous predictors and risk of fatal PE were modelled by logistic regression.

RESULTS

Of the 971 consecutive trauma patients considered in the study, 134 (13.8%) died after their injuries. Fatal PE accounted for 11.9% of all deaths despite unfractionated heparin prophylaxis being used in 44% of these patients. Fatal PE occurred in those who were older (mean age 51- vs 37-yr-old, P=0.01), with more co-morbidities (Charlson's co-morbidity index 1.1 vs 0.2, P=0.01), had a larger BMI (31.8 vs 24.5, P=0.01), and less severe head and systemic injuries when compared with those who died of other causes. Sites of injuries were not significantly related to the risk of fatal PE. Fatal PE occurred much later than deaths from other causes (median 18 vs 2 days, P=0.01), and the estimated attributable mortality of PE was 49% (95% confidence interval 36-62%).

CONCLUSIONS

Fatal PE appeared to be a potential preventable cause of late mortality after major trauma. Severity of injuries, co-morbidity, and BMI were important risk factors for fatal PE after major trauma.

Genetic Control of Chromosome Elimination during Haploid Formation in Barley

Genetic control over chromosome stability in the interspecific hybrid embryos of Hordeum vulgare and H. bulbosum has been hypothesized to reside on specific chromosomes. In this study, crosses between the primary trisomic lines for the seven different H. vulgare chromosomes and tetraploid H. bulbosum revealed that both chromosomes 2 and 3 of H. vulgare were involved in the control of chromosome elimination. Subsequent crosses using the available monotelotrisomics for chromosomes 2 and 3 led to the conclusion that both arms of chromosome 2 and the short arm of chromosome 3 most likely contain major genetic factors.-From the results of this study and the genome balance observed in the interspecific crosses between H. vulgare and H. bulbosum at the diploid and tetraploid cytotypes, it appears that the factors causing the elimination of the bulbosum chromosomes are located on the H. vulgare chromosome. These factors are offset or balanced by factors on the H. bulbosum chromosomes which, when present in sufficient dosage, either neutralize the effects of the vulgare factors or are able to "protect" the bulbosum chromosomes.

Associations between cerebrospinal fluid protein concentrations, serum albumin concentrations and intracranial pressure in neurotrauma and intracranial haemorrhage

Recent evidence suggests that using intravenous isotonic albumin solution for haemodynamic resuscitation in neurotrauma is associated with adverse outcomes. This study assessed the correlations between cerebrospinal fluid protein concentrations, serum albumin concentrations and intracranial pressure in a cohort of neurosurgical patients. After obtaining ethics committee approval, correlations between concomitant cerebrospinal fluid protein concentrations, serum albumin concentrations and the mean daily intracranial pressure of 63 consecutive neurosurgical patients, grouped as neurotrauma or intracranial haemorrhage, admitted between 1 January and 31 December 2007, were assessed. The mean daily intracranial pressure was significantly associated with cerebrospinal fluid protein concentrations (Spearman correlation coefficient [SCC] = 0.496, P = 0.001), white cell counts (SCC = 0.359, P = 0.001), red cell counts (SCC = 0.399, P = .0O01) and serum albumin concentrations (SCC = 0.431, P = 0.001) in patients with neurotrauma (n=23). Cerebrospinal fluid protein concentrations were also significantly associated with concomitant serum albumin concentrations (SCC = 0.393, P = 0.001) in these patients. In patients with intracranial haemorrhage (n=40), the mean daily intracranial pressure was only significantly associated with cerebrospinal fluid white cell and red cell counts but not cerebrospinal fluid protein and serum albumin concentrations. In summary, intracranial pressure is correlated with cerebrospinal fluid protein and serum albumin concentrations in patients with severe neurotrauma, and these suggest that blood-brain barrier may not be completely intact after severe neurotrauma.

Effect of length of stay in intensive care unit on hospital and long-term mortality of critically ill adult patients

BACKGROUND

Critical illness leading to prolonged length of stay (LOS) in an intensive care unit (ICU) is associated with significant mortality and resource utilization. This study assessed the independent effect of ICU LOS on in-hospital and long-term mortality after hospital discharge.

METHODS

Clinical and mortality data of 22 298 patients, aged 16 yr and older, admitted to ICU between 1987 and 2002 were included in this linked-data cohort study. Cox's regression with restricted cubic spline function was used to model the effect of LOS on in-hospital and long-term mortality after adjusting for age, gender, acute physiology score (APS), maximum number of organ failures, era of admission, elective admission, Charlson's co-morbidity index, and diagnosis. The variability each predictor explained was calculated by the percentage of the chi(2) statistic contribution to the total chi(2) statistic.

RESULTS

Most hospital deaths occurred within the first few days of ICU admission. Increasing LOS in ICU was not associated with an increased risk of in-hospital mortality after adjusting for other covariates, but was associated with an increased risk of long-term mortality after hospital discharge. The variability on the long-term mortality effect associated with ICU LOS (2.3%) appeared to reach a plateau after the first 10 days in ICU and was not as important as age (35.8%), co-morbidities (18.6%), diagnosis (10.9%), and APS (3.6%).

CONCLUSIONS

LOS in ICU was not an independent risk factor for in-hospital mortality, but it had a small effect on long-term mortality after hospital discharge after adjustment for other risk factors.

Benefits and risks of furosemide in acute kidney injury

Furosemide, a potent loop diuretic, is frequently used in different stages of acute kidney injury, but its clinical roles remain uncertain. This review summarises the pharmacology of furosemide, its potential uses and side effects, and the evidence of its efficacy. Furosemide is actively secreted by the proximal tubules into the urine before reaching its site of action at the ascending limb of loop of Henle. It is the urinary concentrations of furosemide that determine its diuretic effect. The severity of acute kidney injury has a significant effect on the diuretic response to furosemide; a good 'urinary response' may be considered as a 'proxy' for having some residual renal function. The current evidence does not suggest that furosemide can reduce mortality in patients with acute kidney injury. In patients with acute lung injury without haemodynamic instability, furosemide may be useful in achieving fluid balance to facilitate mechanical ventilation according to the lung-protective ventilation strategy.

Inflammation, vitamin deficiencies and organ failure in critically ill patients

It is unknown whether biochemical vitamin deficiencies in critical illness are associated with severity of illness, organ dysfunction, inflammation or mortality. This nested cohort study recruited 98 patients admitted as emergencies to the intensive care unit, who had a stay of greater than 48 hours. Patient data were prospectively collected. Within the first 48 hours of admission, concentrations of C-reactive protein, vitamins A, E, B1, B12 and folate were measured on arterial blood. These measures were then repeated at least once during the later (> 48 hours) period of their stay. Seventy patients (71%) had completed vitamin studies eligible for inclusion in the analysis. Ten patients died (14.3%) during their hospital stay and mortality was associated with age, admission source and severity of illness scores. Vitamin B12 concentration was weakly associated with C-reactive protein concentrations on admission to the intensive care unit (r on days one and two = 0.4 [P = 0.002], 0.36 [P = 0.04], respectively) and with the Sequential Organ Failure Assessment score between days two and four (Spearman's r = 0.361 [P = 0.04], 0.42 [P = 0.02] and 0.48 [P = 0.02], respectively). Vitamin A concentration was weakly associated with the C-reactive protein concentrations on days one and five (Spearman's r = -0.5 [P = 0.001], -0.4 [P = 0.03], respectively). Change in deficiency status of any of the vitamins over time in the first week of intensive care admission did not appear to influence mortality. We conclude that while weak correlations were identified between vitamins A and B12 and C-reactive protein and Sequential Organ Failure Assessment scores, the importance of these associations and their relationship to hospital mortality remain to be determined.

Effect of an episode of critical illness on subsequent hospitalisation: a linked data study

Healthcare utilisation can affect quality of life and is important in assessing the cost-effectiveness of medical interventions. A clinical database was linked to two Australian state administrative databases to assess the difference in incidence of healthcare utilisation of 19,921 patients who survived their first episode of critical illness. The number of hospital admissions and days of hospitalisation per patient-year was respectively 150% and 220% greater after than before an episode of critical illness (assessed over the same time period). This was the case regardless of age or type of surgery (i.e. cardiac vs non-cardiac). After adjusting for the ageing effect of the cohort as a whole, there was still an unexplained two to four-fold increase in hospital admissions per patient-year after an episode of critical illness. We conclude that an episode of critical illness is a robust predictor of subsequent healthcare utilisation.

Stabilities and fragmentation energies of Si(n) clusters (n = 2-33)

The structures of Si(n) (n = 2-33) were confirmed by genetic algorithm (GA)/tight binding (TB) search and ab initio calculations at the B3LYP/6- 311++G(2d) and PW91/6-311++G(2d) level, respectively. The fragmentation energies, binding energies, second differences in energy, and highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps in the size range 2≤n≤33 were calculated and analyzed systematically. We extended the cluster size involved in the fragmentation analyses up to Si(33), and studied the multi-step fragmentations of Si(n). The calculated result is similar to the fragmentation behavior of small silicon clusters studied previously, showing that Si(6), Si(7), and Si(10) have relatively larger stabilities and appear more frequently in the fragmentation products of large silicon clusters, which is in good agreement with the experimental observations.

Profound hypocalcaemia in a patient being anticoagulated with citrate for continuous renal replacement therapy

Citrate, as an anticoagulant for continuous renal replacement therapy in critically ill patients, has some potential advantages over heparin, including a prolonged dialysis filter life and reduced risk of bleeding. The key parameter involved in monitoring the adequacy and safety of citrate anticoagulation during continuous renal replacement therapy pertains to the ionised and total plasma calcium levels. We report a case of severe systemic hypocalcaemia during continuous renal replacement therapy with citrate anticoagulation resulting from relentless sequestration of calcium due to undiagnosed evolving rhabdomyolysis. Although excessive systemic citrate accumulation can also cause hypocalcaemia, this complication was not observed in our patient. While an acceptable lower limit of ionised calcium remains unknown, severe rhabdomyolysis needs to be considered when a patient's ionised calcium levels are not responsive to standard calcium replacement therapy during continuous renal replacement therapy using citrate anticoagulation in critically ill patients.

Use of remifentanil as a sedative agent in critically ill adult patients: a meta-analysis

This meta-analysis examined the benefits of using remifentanil as a sedative agent in critically ill patients. A total of 11 randomised controlled trials, comparing remifentanil with another opioid or hypnotic agent in 1067 critically ill adult patients, were identified from the Cochrane controlled trials register and EMBASE and MEDLINE databases, and subjected to meta-analysis. Remifentanil was associated with a reduction in the time to tracheal extubation after cessation of sedation (weighted-mean-difference -2.04 h (95% CI -0.39 to -3.69 h); p = 0.02). Remifentanil was, however, not associated with a significant reduction in mortality (relative risk 1.01 (95% CI 0.67-1.52); p = 0.96), duration of mechanical ventilation, length of intensive care unit stay, and risk of agitation (relative risk 1.08 (95% CI 0.64-1.82); p = 0.77) when compared to an alternative sedative or analgesic agent. The current evidence does not support the routine use of remifentanil as a sedative agent in critically ill adult patients.

A comparison of eosinopenia and C-reactive protein as a marker of bloodstream infections in critically ill patients: a case control study

Diagnosis of bloodstream infections in critically ill patients is difficult. This case control study involved a total of 22 patients with confirmed bloodstream infections and 44 concurrent controls from an intensive care unit in Western Australia. We aimed to assess whether eosinopenia and C-reactive protein are useful markers of bloodstream infections in critically ill patients. The patients with bloodstream infections had a more severe disease and a longer length of intensive care unit (10.7 vs 4.0 days, P = 0.001) and hospital stay (40.9 vs 17.9 days, P = 0.015) than the controls. Univariate analyses showed that C-reactive protein (area under the receiver operating characteristic curve 0.847, 95% confidence interval (CI) 0.721 to 0.973), eosinophil counts (area under the receiver operating characteristic curve 0.849, 95% CI 0.738 to 0.961) and fibrinogen concentrations (area under the receiver operating characteristic curve 0.730, 95% CI 0.578 to 0.882) were significant markers of bloodstream infections. C-reactive protein concentration was, however the only significant predictor in the multivariate analysis (odds ratio 1.21 per 10 mg/l increment, 95% CI 1.01 to 1.39, P = 0.007). C-reactive protein concentration appears to be a better marker of bloodstream infections than eosinopenia in critically ill patients. A large prospective cohort study is needed to assess whether eosinopenia is useful in addition to C-reactive protein concentrations as a marker of bloodstream infections.

Risk factors and outcomes of methicillin-resistant Staphylococcus aureus bacteraemia in critically ill patients: a case control study

Methicillin-resistant Staphylococcus aureus (MRSA) infection is an increasing threat to critically ill patients in many intensive care units. MRSA bacteraemia is an extreme form of MRSA infection and is a significant cause of morbidity and mortality. This case control study aimed to assess the risk factors and outcomes of MRSA bacteraemia compared to methicillin-susceptible Staphylococcus aureus (MSSA) bacteraemia. A total of 21 MRSA bacteraemia and 60 randomly selected MSSA bacteraemia episodes, admitted to the intensive care unit at Royal Perth Hospital between 1997 and 2007, were considered. There was a suggestion that hospitalisation within the preceding six months (P = 0.087) and residence in a long-term care facility (P = 0.065) were associated with a higher risk of MRSA bacteraemia. MRSA bacteraemia was more often treated with antibiotics to which the pathogen was not susceptible in vitro (38.1% vs 0%, P = 0.001), resulting in a longer duration of fever (median 7.0 vs 2.0 days, P= 0.009) and bacteraemia (mean 3.2 vs 0.6 days, P = 0.005) and a higher incidence of metastatic seeding of infection (52.4% vs 21.7%, P = 0.012) as compared to MSSA bacteraemia. While in-hospital mortality between MRSA and MSSA was similarly high (47.6% vs 38.3% for MRSA and MSSA respectively, P = 0.607), a significant proportion of the patients who had MRSA bacteraemia died within five years of hospital discharge (36.4%, hazard ratio 26.0, 95% confidence interval 1.90 to 356.7, P = 0.015). Infections contributed to 75% of the deaths after hospital discharge in patients who had an episode of MRSA bacteraemia. MRSA bacteraemia carries a much worse long-term prognosis than MSSA bacteraemia and that could be explained by recurrent MRSA infections and residual confounding.

A first-principles divide-and-conquer approach for electronic structure of large systems and its application to graphene nanoribbons

We demonstrate an efficient and accurate first-principles method to calculate the electronic structure of a large system using a divide-and-conquer strategy based on localized quasi-atomic minimal basis set orbitals recently developed. Tight-binding Hamiltonian and overlap matrices of a large system can be constructed by extracting the matrix elements for a given pair of atoms from first-principles calculations of smaller systems that represent the local bonding environment of the particular atom pair. The approach is successfully applied to the studies of electronic structure in graphene nanoribbons. This provides a promising way to do the electronic simulation for large systems directly from first principles.

Efficient first-principles simulation of noncontact atomic force microscopy for structural analysis

We propose an efficient scheme to simulate noncontact atomic force microscopy images by using first-principles self-consistent potential from the sample as input without explicit modeling of the atomic force microscopy tip. Our method is applied to various types of semiconductor surfaces including Si(111)-(7x7), TiO2(110)-(1x1), Ag/Si(111)-(sqrt[3]xsqrt[3])R30 degrees, and Ge/Si(105)-(1x2) surfaces. We obtain good agreement with experimental results and previous theoretical studies, and our method can aid in identifying different structural models for surface reconstruction.

High-quality ZnO nanowire arrays directly fabricated from photoresists

We report a simple and effective method for fabricating and patterning high-quality ZnO nanowire arrays using carbonized photoresists to control the nucleation site, density, and growth direction of the nanowires. The ZnO nanowires fabricated using this method show excellent alignment, crystal quality, and optical properties that are independent of the substrates. The carbonized photoresists provide perfect nucleation sites for the growth of aligned ZnO nanowires and they also perfectly connect to the nanowires to form ideal electrodes that can be used in many applications of ZnO nanomaterials.

Ceftibuten resistance and treatment failure of Neisseria gonorrhoeae infection

Neisseria gonorrhoeae infections have been empirically treated in Hong Kong with a single oral 400-mg dose of ceftibuten since 1997. Following anecdotal reports of the treatment failure of gonorrhea with oral extended-spectrum cephalosporins, the current study was undertaken to determine the antimicrobial susceptibility pattern and molecular characteristics of isolates of N. gonorrhoeae among patients with putative treatment failure in a sexually transmitted disease clinic setting. Between October 2006 and August 2007, 44 isolates of N. gonorrhoeae were studied from patients identified clinically to have treatment failure with empirical ceftibuten. The ceftibuten MICs for three strains were found to have been 8 mg/liter. These strains were determined by N. gonorrhoeae multiantigen sequence typing to belong to sequence type 835 (ST835) or the closely related ST2469. The testing of an additional eight archived ST835 strains revealed similarly elevated ceftibuten MICs. The penA gene sequences of these 11 isolates all had the mosaic pattern previously described as pattern X. Of note is that the ceftriaxone susceptibility results of these strains all fell within the susceptible range. It is concluded that ceftibuten resistance may contribute to the empirical treatment failure of gonorrhea caused by strains harboring the mosaic penA gene, which confers reduced susceptibility to oral extended-spectrum cephalosporins. Screening for such resistance in the routine clinical laboratory may be undertaken by the disk diffusion test. The continued monitoring of antimicrobial resistance and molecular characteristics of N. gonorrhoeae isolates is important to ensure that control and prevention strategies remain effective.

Risk factors associated with human immunodeficiency virus (HIV) infection among attendees of public sexually transmitted infection clinics in Hong Kong: implications for HIV prevention

OBJECTIVE

To examine the risk factors for human immunodeficiency virus (HIV) transmission among attendees of public sexually transmitted infection clinics in Hong Kong.

DESIGN

Retrospective matched case-control study.

SETTING

All public sexually transmitted infection clinics in Hong Kong.

PATIENTS

All public sexually transmitted infection clinic attendees' records from January 1995 to December 2002 were reviewed.

MAIN OUTCOME MEASURES

HIV sero-positivity in corresponding clinic attendees.

RESULTS

A total of 196 HIV-positive cases among 149,336 sexually transmitted infection clinic attendees were recruited into the study. Multivariate analysis using conditional logistic regression revealed that HIV infection was associated with the following factors: belonging to non-Chinese ethnic groups (mainly South-East Asian) [odds ratio=9.32; 95% confidence interval, 3.27-26.55], coexisting syphilis (other than primary) [5.67; 1.66-19.36], current non-gonococcal urethritis (2.10; 1.08-4.07), current genital warts (1.94; 1.10-3.43), history of prior sexually transmitted infection (2.19; 1.29-3.72), having casual sex with friends (2.89; 1.07-7.80), and casual sex in Mainland China (1.91; 1.04-3.49). Sexual orientation was also considered to be a potential risk factor, as only those who tested positive reported to be homosexual or bisexual.

CONCLUSION

Sexually transmitted disease patients represent an identifiable group who are at high risk of HIV infection. This study found that there were certain factors which increased the risk of HIV infection among patients attending public sexually transmitted infection clinics. Targeted interventions should therefore be offered to such high-risk individuals, so as to prevent and control HIV transmission.

The effect of aprotinin on risk of acute renal failure requiring dialysis after on-pump cardiac surgery

The use of aprotinin in cardiac surgery to reduce perioperative bleeding and transfusion is controversial. We assessed the effect of aprotinin on the risk of acute renal failure in 423 patients who underwent on-pump cardiac surgery between January 1, 2005 and December 31, 2006. Of these 423 patients, 318 (75.2%) received aprotinin (median dose=3.0 million KIU, standard deviation=2.8 million KIU; interquartile range: 2 million KIU to 4 million KIU). Aprotinin was more likely to be used in patients who did not cease aspirin before surgery, in urgent or emergency surgery, who had impaired left ventricular function, a longer period of bypass and aortic cross-clamp time, and with both coronary artery bypass graft and valvular surgery performed. The overall incidence of acute renal failure requiring dialysis was 2.8%. The use of aprotinin was not associated with a reduction in transfusion nor an increased risk of renal failure requiring dialysis, atrial fibrillation, cerebrovascular accident or mortality in the univarate analyses. In the multivariate analysis, only preoperative serum creatinine concentration (odds ratio [OR] 1.06 per 10 micromol/l increment in creatinine, 95% confidence interval [CI]: 1.01 to 1.14, P=0.029) and urgency of the surgery (urgent vs. scheduled surgery: OR 12.8, CI: 2.3 to 70.8, P=0.004; emergency vs. scheduled surgery: OR 23.1, CI: 3.0 to 180.2, P=0.003) were significantly associated with an increased risk of acute renal failure requiring dialysis. The use of low-dose aprotinin did not significantly reduce perioperative transfusion requirements and was not a significant risk factor for acute renal failure requiring dialysis in our patients.

Bayesian approach to predict hospital mortality of intensive care readmissions during the same hospitalisation

No specific prognostic model has been developed for patients readmitted to the intensive care unit (ICU) during the same hospitalisation. This study assesses the performance of the Acute Physiology and Chronic Health Evaluation (APACHE) II predicted mortality measured at the time of ICU readmission and whether incorporating information prior to the readmission will improve its performance to predict hospital mortality of patients readmitted to ICU during the same hospitalisation. A total of 602 readmissions during the same hospitalisation between 1987 and 2002 were identified. The first admission APACHE II predicted mortality was significantly associated with the hospital mortality only in the subgroup of patients readmitted within seven days of ICU discharge (odds ratio 1.16, 95% confidence interval 1.01 to 1.34; P = 0.035). In the subgroups of patients readmitted within seven days of discharge, the readmission APACHE II predicted mortality was also significantly better than the first admission APACHE II predicted mortality in discriminating between survivors and non-survivors (area under the receiver operating characteristic curve: 0.785 vs. 0.676, z statistic = 2.93; P = 0.003). Incorporating the first admission APACHE II predicted mortality to the readmission APACHE II predicted mortality, either by multilevel likelihood ratios or logistic regression, did not significantly improve its discrimination (area under the receiver operating characteristic curve: 0.792 vs. 0.785, z statistic = 0.52; P = 0.603). Our results suggested that information on prior ICU admission during the same hospitalisation is not as important as the severity of illness measured at the time of readmission in determining the mortality of intensive care readmissions during the same hospitalisation.