Simulation of survivorship bias in observational studies on plasma to red blood cell ratios in massive transfusion for trauma.

BACKGROUND: Observational studies on injured patients requiring massive transfusion have found a survival advantage associated with use of equivalent number of units of fresh frozen plasma (FFP) and packed red blood cells (RBCs) compared with use of FFP based on conventional guidelines. However, a survivorship bias might have favoured the higher use of FFP because patients who died early never had the chance to receive sufficient FFP to match the number of RBC units transfused. METHODS: A Markov model using trauma data from local hospitals was constructed and various FFP transfusion scenarios were applied in Monte Carlo simulations in which the relative risk of death associated with exposure to high FFP transfusion was set at 1.00, so that the FFP : RBC ratio had no influence on mortality outcome. RESULTS: Simulation results showed that the relative risk associated with exposure to high FFP transfusion was less than 1.00 (0.33-0.56 based on programmed delays in achieving an FFP : RBC ratio of 1 : 1-2), thus demonstrating a survivorship bias in favour of FFP : RBC equal to or more than 1 : 1-2 in certain observational trauma studies. This bias was directly proportional to the delay in achieving a FFP : RBC ratio of 1 : 1-2 during resuscitation. CONCLUSION: Some observational studies comparing low and high FFP administration in injured patients requiring massive transfusion probably involve survivorship bias that inflates or creates a survival advantage in favour of a higher FFP : RBC ratio.

The first 5 years since trauma center designation in the Hong Kong Special Administrative Region, People's Republic of China.

BACKGROUND: In 1994, the Hong Kong Special Administrative Region (HKSAR) introduced plans to implement a trauma system based on the recommendations outlined by Professor Donald Trunkey in his report to the local Hospital Authority. Five government-subsidized public hospitals were subsequently designated as trauma centers in 2003. This article reviews the initial experience in these five centers. METHODS: Prospective trauma registries from January 2004 to December 2008 were reviewed. Primary clinical outcome measures were hospital mortality. The Trauma and Injury Severity Score methodology was used for benchmarking with the Major Trauma Outcome Study (MTOS) database. RESULTS: The majority (83.3%) of the 10,462 patients suffered from blunt trauma. Severe injury, defined as Injury Severity Score>15, occurred in 29.7% of patients. The leading causes of trauma were motor vehicle collisions and falls, with crude hospital mortality rates of 6.9% and 10.7%, respectively. The M-statistic was 0.95, indicating comparable case-mix with the MTOS. The worst outcome occurred in the first year. Significant improvement was seen in patients with penetrating injuries. By 2008, these patients had significantly higher survival rates than expected (Z-statistic=0.85). Although the overall mortality rates for blunt trauma were higher than expected, the difference was no longer statistically significant from the second year onward. CONCLUSIONS: The case-mix of trauma patients in the HKSAR is comparable with that of the MTOS. A young trauma system relatively unburdened by dissimilar reimbursement and patient access issues may achieve significant improvement and satisfactory patient outcomes. Our findings may serve as a useful benchmark for HK and other Southeast Asian cities and trauma systems to establish local coefficients for future evaluations.

Experimental study of the temporal profile of breath alcohol concentration in a Chinese population after a light meal.

In forensic science, the Widmark equation is widely used to deduce the blood alcohol concentration (BAC) at different time points. But the linear model specified by Widmark might be deficient in predicting the breath alcohol concentration (BrAC) at different time points, and extrapolating the peak and the corresponding time. In order to establish the temporal profile of alcohol concentration which captures the effects of non-linear nature of alcohol absorption, elimination, and peak, in particular of Chinese population after a light meal, a drinking experiment was conducted in this study. To achieve this, a double-blind drinking experiment was conducted to measure the BrAC of 52 Chinese participants after a light meal in this study. Prior to the experiment, all participants were required to abstain from food for 4 hours, more importantly, from alcohol and sedatives for 24 hours. A standard light meal was provided about 30 minutes prior to the alcohol intake in the experiment. The BrAC was measured at a 10-minute interval during the absorption phase and 30-minute interval during the elimination phase respectively. The measurements were stopped when the BrAC fell to 0.010 mg/100 ml or below, or more than 8 hours after the alcohol intake. Then, the temporal profiles of BrAC, assuming linear and non-linear relationships, were established using Full Bayesian approach. The linear component indicated the alcohol impairment in normal social function, with which a light meal is usually accompanied with drinking. On the other hand, the non-linear (gamma distribution) part replicated the absorption phase, elimination phase, and the peak of alcohol concentration. The proposed model well performed than the conventional regression model. Additionally, the confounding factors including gender, body weight, and dosage were controlled for. Results should be useful for the development of cost-effective enforcement measures that could deter against drink driving.

Risk factors for injury to married women from domestic violence in Hong Kong.

OBJECTIVE: To examine risk factors for injury to married women from domestic violence in Hong Kong. DESIGN: Case control study. SETTING: Regional public hospital, Hong Kong. PATIENTS: All married women aged 18 to 60 years who attended an accident and emergency department for treatment of a domestic violence injury from January 2004 to June 2005. MAIN OUTCOME MEASURES: Social and health characteristics of abused women and their husbands. RESULTS: A total of 293 cases were compared to 313 controls. Eight predictive variables were found to be significant by univariate analysis: woman who is a new immigrant (P = 0.003), woman with no job (P = 0.019), husband with low educational level (P < 0.001), presence of extramarital affairs (P < 0.001), husband's unemployment (P < 0.001), husband's alcohol abuse (P < 0.001), husband's illicit drug abuse (P = 0.032), husband's mental illness (P < 0.001). Five factors were found to be significant in a logistic regression analysis: husband with a low educational level (nil to primary) [adjusted odds ratio = 2.78; 95% confidence interval, 1.149-6.727], husband unemployed (adjusted odds ratio = 9.031; 95% confidence interval, 5.163-15.796), presence of extramarital affairs (adjusted odds ratio = 5.218; 95% confidence interval, 2.899-9.395), husband's alcohol abuse (adjusted odds ratio = 6.089; 95% confidence interval, 3.460-10.716), husband's mental illness (adjusted odds ratio = 9.443; 95% confidence interval, 2.351-37.926). CONCLUSIONS: Several significant risk factors have been identified for injury incurred during domestic violence to married women in Hong Kong. It provides information useful for developing local preventive strategies.

A simulation study of the effects of alcohol on driving performance in a Chinese population.

UNLABELLED: Driving under the influence of alcohol (DUIA) is a significant factor contributing to road traffic crashes, injuries, and fatalities. Although the effects of alcohol on driving performance are widely acknowledged, studies of the effects of alcohol impairment on driving performance and particularly on the control system of Chinese adults are rare. This study attempts to evaluate the effects of alcohol on the driving performance of Chinese adults using a driving simulator. METHOD: A double-blind experimental study was conducted to evaluate the effects of alcohol impairment on the driving performance of 52 Chinese participants using a driving simulator. A series of simulated driving tests covering two driving modules, including emergency braking (EB) and following braking (FB), at 50km/h and 80km/h were performed. Linear mixed models were established to evaluate driving performance in terms of braking reaction time (BRT), the standard deviation of lateral position (SD-LANE), and the standard deviation of speed (SD-SPEED). RESULTS: Driving performance in terms of BRT and SD-LANE was highly correlated with the level of alcohol consumption, with a one-unit increase in breath alcohol concentration (BrAC) degrading BRT and SD-LANE by 0.3% and 0.2%, respectively. Frequent drinkers generally reacted faster in their BRT than less-frequent drinkers and non-drinkers by 10.2% and 30.6%, respectively. Moreover, alcohol impairment had varying effects on certain aspects of the human control system, and automatic action was less likely to be affected than voluntary action from a psychological viewpoint. CONCLUSION: The findings should be useful for planning and developing effective measures to combat drink driving in Chinese communities.

Assessment of quality of life and functional outcome in patients sustaining moderate and major trauma: a multicentre, prospective cohort study.

BACKGROUND: Trauma care systems aim to reduce both death and disability, yet there is little data on post-trauma health status and functional outcome. OBJECTIVES: To evaluate baseline, discharge, six month and 12 month post-trauma quality of life, functional outcome and predictors of quality of life in Hong Kong. METHODS: Multicentre, prospective cohort study using data from the trauma registries of three regional trauma centres in Hong Kong. Trauma patients with an ISS≥9 and aged≥18 years were included. The main outcome measures were the physical component summary (PCS) score and mental component summary (MCS) scores of the Short-Form 36 (SF36) for health status, and the extended Glasgow Outcome Scale (GOSE) for functional outcome. RESULTS: Between 1 January 2010 and 31 September 2010, 400 patients (mean age 53.3 years; range 18-106; 69.5% male) were recruited to the study. There were no statistically significant differences in baseline characteristics between responders (N=177) and surviving non-responders (N=163). However, there were significant differences between these groups and the group of patients who died (N=60). Only 16/400 (4%) cases reported a GOSE≥7. 62/400 (15.5%) responders reached the HK population norm for PCS. 125/400 (31%) responders reached the HK population norm for MCS. If non-responders had similar outcomes to responders, then the percentages for GOSE≥7 would rise from 4% to 8%, for PCS from 15.5% to 30%, and for MCS from 31% to 60%. Univariate analysis showed that 12-month poor quality of life was significantly associated with age>65 years (OR 4.77), male gender (OR 0.44), pre-injury health problems (OR 2.30), admission to ICU (OR 2.15), ISS score 26-40 (OR 3.72), baseline PCS (OR 0.89), one-month PCS (OR 0.89), one-month MCS (OR 0.97), 6-month PCS (OR 0.76) and 6-month MCS (OR 0.97). CONCLUSION: For patients sustaining moderate or major trauma in Hong Kong at 12 months after injury<1 in 10 patients had an excellent recovery, ≤3 in 10 reached a physical health status score≥Hong Kong norm, although as many as 6 in 10 patients had a mental health status score which is≥Hong Kong norm.

Misclassification of injury severity among road casualties in police reports.

This study aims to evaluate the discordance between police reports of injury severity among road casualties and the length of hospital stay and the Injury Severity Scale (ISS) by linking information from the crash records of the Hong Kong Police with the trauma records of a regional hospital. Sensitivity and specificity analyses suggest that police injury grading diverges noticeably from the definition of a 12-h hospital stay. Police reports overestimate injury severity remarkably. The results of logistic regression indicate that age, the ISS, and the position of the victim significantly determine the likelihood of police injury misclassification. Furthermore, an optimal demarcation point of the length of hospital stay for serious injury is estimated.