Use of stimulants in operational settings: Issues and considerations

One of the first duties of the Physician is to educate the masses not to take medicine. Sir William Osler [1] Introduction Use of stimulants in clinical settings is guided by medicine, science, and the goal of benefiting patients with defined illnesses that are known to be responsive to stimulants (e.g., narcolepsy, attention deficit hyperactivity disorder, and shift work sleep disorder – the latter is discussed in Chapter 8, this volume). At the present time, legitimate use of stimulants (specifically, the amphetamines and modafinil) in operational settings in otherwise normal, healthy adults for management of fatigue is limited to the military – and, in particular, the United States Department of Defense (DoD) [2]. Currently within the US DoD, stimulants are approved for use only under restricted circumstances in certain sectors of aviation and in some Special Forces units. In this chapter we explore some of the experience and issues surrounding this use. The definition of “fatigue” is an issue in itself, the scope of which is beyond this chapter. The DoD uses the Human Factors Analysis and Classification System (DoD HFACS) to determine causal factors associated with accidents and mishaps [3]. DoD HFACS defines fatigue as an adverse physiological state in which: the individual's diminished physical or mental capability is due to an inadequate recovery, as a result of restricted or shortened sleep or physical or mental activity during prolonged wakefulness. Fatigue may additionally be described as acute, cumulative or chronic. DoD HFACS also recognizes the contribution of circadian rhythms to degraded performance: Circadian rhythm desynchrony is a factor when the individual's normal, 24-hour rhythmic biological cycle (circadian rhythm) is disturbed and it degrades task performance. This is caused typically by night work or rapid movement (such as one time zone per hour) across several time zones. Referred to as “shift lag” and “jet lag.” (Time in the new time zone will lead to adaptation and recovery; the amount of time depends on the number of time zones crossed and the direction of travel. Recovery from shift lag may never occur.) Throughout this chapter, we use “fatigue” to mean degraded cognitive/mental performance resulting from inadequate sleep, with or without circadian rhythm desynchrony.