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The Legal Limit: Differences in Injury Severity Score for Vehicular Crashes

Sorrentino, Christopher J. RN, BS, MS; Schulz, John MD, FACS; Chaudry, Aisha MD; Cohen, Eric RN; Friedman, Yelena MLS, AHIP

doi: 10.1097/JTN.0000000000000214

In 2013, the National Transportation Safety Board advised lawmakers in the United States to reduce the legal limit of blood alcohol content (BAC) from 0.08% to 0.05%. The purpose of this research was to evaluate the rationale for reducing the legal limit of BAC to 0.05% through analysis of the relationship between BAC and injury severity. A correlational study was conducted on patients with positive BAC involved in a motor vehicular collision. Retrospective review of 446 trauma patients (aged 18–80 years) injured in a vehicular collision routinely screened for BAC was conducted. Two groups were compared: Group 1, patients with nonzero blood alcohol concentration (n = 101); and Group 2, patients with zero blood alcohol (n = 345). Standard statistical analyses were utilized. A total of 101 patients (23%) had a detectable BAC on admission. Patients with a detectable BAC were younger (33 and 44 years) and more likely to be male (27% and 16%). There was no statistically significant association between both injury severity score (ISS) and BAC or between ISS and age. There was no significant correlation between higher BAC and a higher ISS. Positive BAC alone may not affect ISS, but the potential for risk-taking behaviors by drivers under the influence may increase injury severity.

Staten Island University Hospital, Staten Island, New York.

Correspondence: Christopher J. Sorrentino, RN, BS, MS, Staten Island University Hospital, 475 Seaview Ave, Staten Island, NY 10305 (

Author contribution: John Schulz, MD, FACS, is an editing contributor. Dr Schulz provided expert review of the data analysis and of the manuscript. Aisha Chaudry, MD, conducted data extraction and contributed to the authorship of the abstract. Eric Cohen, RN, provided research extraction and database review. Mr. Cohen also contributed to manuscript revisions. Yelena Friedman, MLS, AHIP, provided additional editing and formatting.

The authors declare no conflicts of interest.

Driving under the influence (DUI) of alcohol remains associated with up to 40% of traffic fatalities in the United States, despite law enforcement efforts to discourage drunken driving (Hadjizacharia et al., 2010). Currently, driving under a serum alcohol level of 0.08 is illegal in all states, with some states having more stringent laws for those aged 18–21 years (Fell & Voas, 2006). Although a serum alcohol level of less than 0.08 is not litigable in most jurisdictions in the United States, other countries have set lower limits varying from 0.00% to 0.05% (Fell & Voas, 2006). Research in multiple other countries suggests that reducing the legal blood alcohol content (BAC) in drivers to 0.05% correlates directly to decreased alcohol-related fatalities (Fell & Voas, 2006). Political forces in the United States have been advocating a similar reduction in the legal limit for drivers, and in May 2013, the National Transportation Safety Board advised Congress to decrease the legal limit of BAC from 0.08% to 0.05%, a reduction by more than a third (Wald, 2013).

The effect of such a change in the law on deterrence in the United States remains to be seen. Internationally, the policy appears to reduce fatalities, presumably by reducing the incidence of DUI. But what effect, if any, will a change in law have on the severity of injuries in those who drive under the influence? Will the average DUI driver have consumed less alcohol and have a lower BAC? Will DUI drivers with lower BAC be less severely injured than those injured with high BAC? Given the proposal on the table to lower the legal serum alcohol ceiling, we investigated whether among patients who were injured after drinking and driving, a lower admission serum alcohol level correlates to less severe injury than a higher admission serum alcohol level.

To address this question, we reviewed 3.5 years of patients admitted to the trauma center at Staten Island University Hospital with injuries sustained in a motor vehicle crash, comparing those who tested positive for serum alcohol with those who did not. Among those patients with a detectable serum alcohol concentration, we assessed correlation (or lack thereof) of serum alcohol concentration with injury severity. Correlations between serum alcohol concentration and injury severity were not statistically significant. Furthermore, mean injury severity score (ISS) in the group of patients with detectable serum alcohol was not statistically significantly different from that of the group with no alcohol.

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With institutional review board approval, a retrospective review of Trauma Registry patients (18–80 years old) injured in motor vehicle crashes between January 2010 and June 2013, inclusive, was conducted. Two groups were compared, Group 1 included patients with a nonzero blood alcohol concentration (n = 101) and Group 2 included patients with no detectable blood alcohol (n = 345), regarding serum ethanol concentration, injury severity score (ISS), and other demographic variables. Statistical analyses (paired t test, chi-square, and Pearson's coefficient) were used to test for a difference between groups. Patients who did not survive resuscitation in the emergency department were excluded.

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During the study period, the trauma center admitted 446 patients injured in motor vehicle crashes. Of these, 101 patients tested positive for blood alcohol (Table 1). As a group, patients testing positive for blood alcohol were younger (33 and 44 years) and more likely to be male (27% and 16%) than those whose BAC was zero. Interestingly, although one in four (76 of 284) patients injured in an automobile crash tested positive for blood alcohol, the rate for those injured in motorcycle crashes was closer to 10% (seven of 55).



Patients testing positive for blood alcohol were statistically no different from the patients testing negative for blood alcohol regarding ISS (Table 1), length of stay, and mortality (1% in both groups). Moreover, there was no discernible correlation between BAC and injury severity (Figures 1–3).

Figure 1

Figure 1

Figure 2

Figure 2

Figure 3

Figure 3

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Consistent with other reports in the literature, our study finds significant differences in some of the demographic characteristics of a population injured after ethanol consumption versus those injured without prior alcohol consumption. We were unable, however, to find a difference in injury severity between the two groups. Furthermore, among those injured after drinking, we found no dose–response between BAC and injury severity. The proposal to reduce the legal driving BAC is aimed at deterring driving after drinking, rather than reducing severity of injuries sustained while driving after drinking.

Alcohol has been shown to impair judgment. Simulation studies demonstrate a dose–response between BAC and impaired driving performance (Leung et al., 2012), and drivers with impaired judgment are more likely to engage in risky behaviors leading to a crash (Shyhalla, 2014). Lethal motor vehicle collisions (MVCs) account for nearly 36% of traumatic deaths in the age group 16–20 years, and 40% of all trauma-related deaths involve individuals with positive BAC (Hadjizacharia et al., 2010). Alcohol is the single most important personal risk factor for motor vehicle-related fatalities. Fell and Voas (2006) reviewed the international trend of reducing the legal limit of serum alcohol level to 0.05%, finding that reduction in BAC to 0.05% directly correlated to a decrease in alcohol-related fatalities and a decrease in the incidence of drivers under the influence of alcohol involved in motor vehicle crashes. Conversely, decreasing the stringency of deterrence by lowering the legal drinking age to 18 years in New Zealand was associated with a significant increase in alcohol-related MVCs among 18- and 19-year-olds (Huckle & Parker, 2014).

Andreucctti et al. (2011) discussed the reduction of BAC in a time-series analysis from 2001 to 2010 in Brazil. Research revealed that of traffic fatalities, 42.3% of the victims had a BAC greater than 0.06 (p. 2125). Public health officials and lawmakers introduced a new public health law in June 2008 aimed to reduce the legal limit of blood alcohol from 0.06 to 0.02 (p. 2125). Brazilian officials also have taken the law a step further by enacting distinctions between “administrative sanctions” and “criminal sanctions” (p. 2125). Administrative sanctions for BAC of 0.02 carries with it a monetary fine and a temporary driver's license suspension. Criminal sanctions are imposed for individuals with a BAC of 0.06, leading to a full driver's license suspension and imprisonment for 6–36 months (p. 2125). Andreucctti et al. (2011) found that the traffic laws enacted had significantly reduced traffic injury and fatality rates both in the state of São Paulo and in the capital of São Paulo by 0.71 and 0.44 per 100,000, respectively (p. 2128).

Although it is clear that alcohol-impaired drivers are more likely to crash, there are conflicting reports regarding the effect of alcohol on injury severity once the crash occurs. Stübig et al. (2012) reported that individuals involved in MVCs while under the influence of alcohol are two times more likely to be killed when compared with a cohort of individuals involved in an MVC that did not involve alcohol. Unsurprisingly, they found that injury severity varied with the velocity of impact in the alcohol-positive cohort and that the higher the blood alcohol level, the more severe the injuries and the likelihood of mortality. Cheng-Shyuan, Hang-Tsung, Shiun-Yuan, Tzu-Yu, and Ching-Hua (2014) also reported that patients from an MVC with any BAC were more likely to have severe injury (ISS >16) but reported that these patients were more likely to survive than equally injured patients with no BAC (especially in the traumatic brain injury cohort from both groups).

On the contrary Mann, Desapriya, Fujiwara, and Pike (2011) concluded that evaluation of BAC as a predictor of injury severity for victims involved in MVCs may be weak. Mann et al. (2011) further argued that BAC may lead to less severe injuries and have no impact on hospital length of stay or mortality. Friedman (2014) found an inverse dose–response between BAC and in-hospital mortality in patients with ISS of more than 16 and later reported that BAC at time of injury was associated with significantly fewer cardiac and renal complications during subsequent hospitalization. Meanwhile, Cowperthwaite and Burnett (2011), in an analysis of the National Trauma Data Bank, found that alcohol use at time of injury was associated with a 15% increase in infectious complications but had no impact on ultimate outcome of hospitalization.

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Our conclusions are limited by a few weaknesses in the study. First, this is a retrospective study and we did not differentiate between passengers and drivers among the patients. Second, the power of our study to detect differences in injury severity, especially at various BAC concentrations, is limited by relatively low numbers of subjects in each group.

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Alcohol consumption continues to be linked with injuries and deaths across the region, as well as the country. Many of these injuries and deaths occur because of MVCs while drivers are intoxicated or under the influence of alcohol. Numerous studies have been aimed to evaluate relationship of BAC and injury severity only briefly, discussing interventions to reduce alcohol-related motor vehicle injuries and fatalities. A Cochrane Collaborative Review in 2009 examined the literature for strategies aimed at mitigating injuries in recidivist drinkers. The review concluded that alcohol is a major factor worldwide causing unintentional injury and that interventions aimed at reducing these unintentional injuries should remain a public health goal (Dinh-Zarr, Goss, Heitman, Roberts, & DiGuiseppi, 2009). The Cochrane review further concluded that continued alcohol intervention programs “are likely to reduce the incidence of injuries” and additional research is necessary to understand the outcomes that “treating problem drinking may have on injuries” (Dinh-Zarr et al., 2009, p. 8). Available methods include alcohol dependence programs, prescription medication abuse programs, counseling, brief alcohol screening programs, and other inpatient and outpatient modalities to combat this public health problem. The available evidence suggests that health care professionals, law enforcement, educators, and community leaders need to continue the grassroots effort at alcohol prevention strategies. Nurses on the front line can utilize their opportunities to speak with patients and provide routine screenings to identify problem drinkers. Even if just one patient can be reached, potentially saving a life, a difference can be made. Nonetheless, continued evaluation of the evidence is necessary to assess effective programs that can be utilized to help drive down the recidivism of alcohol-related hospitalizations.

Implementing any new program or change is difficult, especially in large organizations or departments. Trauma centers verified by the American College of Surgeons Committee on Trauma (ACS-COT, 2006) require alcohol screening on all injured patients. Therefore, any patient treated at a trauma center with a positive BAC on hospitalization should be given a brief alcohol screen and on the basis of the risk score, the patient may be referred to inpatient detoxification or provided with a number of outpatient resources. Trauma centers can augment these efforts by consistently engaging in “screening, brief intervention and referral for treatment” (SBIRT) as suggested by the ACS-COT.

Hospital leadership, physicians, and nurses alike must be “bought in” in order for there to be an effective alcohol screening and intervention program. Appropriate utilization of evidence, best practices, and knowledge of community resources is paramount to implement such a program. “Champions” should be identified in various units throughout the organization to assist with program implementation at the staff level and will provide the upfront support of new programs.

Health care professionals could argue the merit of such a program in hospital systems that struggle to manage an ever-narrowing operating margin. However, the repeat offenders driving under the influence of alcohol need to be reached each and every time they step foot in an emergency department. The overutilization of emergency departments continues to lead to an increased operating cost without appropriate or adequate reimbursement. Efforts to reduce alcohol-related emergency department visits will not only save lives but potentially drive down the overhead cost of the department in relation to this particular group of patients as well.

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U.S. traffic fatalities have declined significantly over the past 30 years, thanks, in part, to combined efforts of the federal government, state, and local city municipalities. Regardless of the relationship (or lack of relationship) between BAC and severity of injury, there is evidence that lowering the legal limit of BAC and increasing the stringency of the statutory deterrence is likely to reduce the number of drunk drivers on the road and thereby reduce the alcohol-related traumatic injuries and fatalities seen in our trauma centers.

Evidence-based practice has the proven potential to improve health outcomes through public health initiatives and individual patient outcomes whether inpatient or outpatient. The problem of alcohol intoxication, and injuries associated with it, provides the basis for an ongoing evaluation of strategies aimed at prevention. Traumatic injuries are preventable in one form or another. Despite the plethora of available evidence, further research is needed to evaluate the effectiveness of such programs and the effects of alcohol not only on injury severity and outcomes but also on the addition of polysubstance abuse and risk-taking behaviors.

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  • Alcohol, despite law enforcement and community efforts, continues to be a leading factor in vehicular crashes.
  • Lowering the legal limit of BAC does not necessarily reduce the injury severity of victims involved in vehicular crashes.
  • Evidence suggests that lowering the legal limit of BAC and increasing the stringency of statutory deterrence reduces the number of alcohol-impaired drivers.
  • Trauma centers and non-trauma centers alike should strengthen their alcohol screening programs and offer legitimate resources for patients presenting with alcohol-related hospital visits.
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Myriam Kline, PhD, was the statistician for the data analysis.

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        Blood alcohol content; Injury; Motor vehicle; Prevention; Severity; Trauma

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