Sleepiness, Driving, and Traffic Accidents
Motor vehicle accidents (MVA) remain among the top 10 causes of death in the last decade. Although alcohol is the single greatest contributor to fatal MVA (responsible for about 40%), data from the National Highway Traffic Safety Administration indicates that 4% of MVA fatalities may be attributable to driver sleepiness. Drivers with untreated sleep apnea and narcolepsy are at increased risk for MVA, to the point that numerous states have established guidelines for reporting these disorders to licensing authorities. The huge majority of sleep-related crashes (96%) involve passenger vehicles, rather than commercial vehicles.
The authors point out a role for the physician in preventing sleep-related crashes: Persons with sleep disorders may respond well to intervention. Additionally, many young adults have intermittently disrupted sleep schedules (late-night study, late-night socializing, poor sleep habits). The magnitude of these sleep disruptions is corroborated by the fact that 60% of sleep-related crashes involve persons less than age 30. Physicians may benefit from heightened awareness of the consequences of sleep deprivation on motor vehicle accidents.
Lyznicki JM, et al. JAMA 1998;279: 1908-1913.
Clinical Scenario: The ECG shown in the figure was obtained from a previously healthy young adult admitted to the hospital intensive care unit for TCA (tricyclic antidepressant) overdose. In view of this history, is her initial ECG worrisome? If so, why?
Interpretation: There are several signs present on this patient's initial ECG that are consistent with TCA overdose. These include sinus tachycardia, a relatively vertical (almost rightward) mean QRS axis, non-specific ST-T wave changes, incomplete right bundle branch block (RBBB), and QRS widening. It is of interest that P waves are not well seen in standard lead II. Instead, the diagnosis of sinus tachycardia has to be presumed from inspection of lead V1 (that shows definite P wave activity). This was confirmed on subsequent tracings.
Although QT interval prolongation is probably the most commonly cited ECG sign of TCA overdose, it is not as good of a predictor of potentially lethal complications (from either seizures or arrhythmias) as QRS prolongation (to > or = 0.10 second). Determination of whether or not the QT interval is prolonged is difficult when the heart rate is rapid and the end of the T wave is indistinct (as in this tracing). Regardless, the presence of this degree of sinus tachycardia in a previously healthy young adult with a QRS interval that exceeds 0.10 second should clearly be cause for concern.
Suggested Reading
1. Goldberg RJ, et al. JAMA 1985;254:1772.
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