According to the legal definition, “under the influence” is a term that describes a state of intoxication that is criminal when engaging in certain activities; for instance, public intoxication or driving under the influence.* It is unlawful in all 50 states and the District of Columbia to drive a vehicle when one’s blood alcohol concentration (BAC) is greater than 0.08 percent. On the Centers for Disease Control and Prevention motor vehicle safety web page, under the “BAC Effects” tab, is a table that outlines how much alcohol needs to be consumed to reach certain BAC levels, typical effects, and predictable effects on driving.†
Know your limit
The table uses a standard drink size in the U.S. of 14.0 grams (0.6 ounces) of pure alcohol. This equates to a 12-ounce beer (5 percent alcohol content), eight ounces of malt liquor (7 percent alcohol content), five ounces of wine (12 percent alcohol content), or one-and-one-half ounces (a shot) of 80 proof (40 percent alcohol content) distilled spirits or liquor (for example, gin, vodka, rum, or whiskey).†
If a 160-pound man consumes two alcoholic drinks in one hour, his BAC will reach approximately 0.02 percent. The typical effects are some loss of judgment, relaxation, slight body warmth, and an altered mood. Behind the wheel of a motor vehicle, this individual will experience a decline in visual functions and an inability to perform two tasks at the same time (divided attention). After three drinks in one hour, his BAC approaches 0.05 percent, leading to exaggerated behavior, difficulty focusing his eyes, impaired judgment, lowered alertness, and a release of inhibition. When driving, he will experience reduced coordination, reduced ability to track moving objects, difficulty steering, and a reduced response to emergency driving situations.
At about four alcoholic drinks in an hour, his BAC will reach 0.08 percent, resulting in diminished balance, speech, vision, reaction time, and hearing. It will be harder to detect danger, and his judgment, self-control, reasoning, and memory will be impaired. Getting behind the wheel at this level can be particularly hazardous because of altered concentration, short-term memory loss, difficulty with speed control, reduced information processing capability (for example, signal detection or visual search), and impaired perception. Adding a fifth drink in an hour results in a BAC of approximately 0.1 percent and a reduced ability to maintain lane position and appropriate braking.
Life-altering consequences
To examine the occurrence of injuries in patients under the influence of alcohol in the National Trauma Data Bank® (NTDB®) research admission year 2017, medical records were searched using BAC. Specifically searched were records of individuals who had a BAC of 0.08 percent or greater. A total of 90,642 records were found, of which 73,435 records contained a discharge status, including 57,440 patients discharged to home, 8,131 to acute care/rehab, 957 to law enforcement, 4,192 to skilled nursing facilities; 2,715 died (see Figure 1). Of these patients, 78 percent were men, on average 42.3 years of age, had an average hospital length of stay of 5.8 days, an intensive care unit length of stay of 5.4 days, an average injury severity score of 10.5, and were on the ventilator for an average of 5.4 days. The top three mechanisms of injury accounting for almost two-thirds of all cases were motor vehicle related (34.8 percent), fall (28.7 percent), and struck by/against (as a result of contact made between one person and another person[s] or object[s]) (11.3 percent). See Figure 2 for more information on alcohol-related mechanisms of injury.
Figure 1. Hospital Discharge Status
