Level of Consciousness

Excerpt

The normal state of consciousness comprises either the state of wakefulness, awareness, or alertness in which most human beings function while not asleep or one of the recognized stages of normal sleep from which the person can be readily awakened.

The abnormal state of consciousness is more difficult to define and characterize, as evidenced by the many terms applied to altered states of consciousness by various observers. Among such terms are: clouding of consciousness, confusional state, delirium, lethargy, obtundation, stupor, dementia, hypersomnia, vegetative state, akinetic mutism, locked-in syndrome, coma, and brain death. Many of these terms mean different things to different people, and may prove inaccurate when transmitting and recording information regarding the state of consciousness of a patient. Nevertheless, it is appropriate to define several of the terms as closely as possible.

Clouding of consciousness is a very mild form of altered mental status in which the patient has inattention and reduced wakefulness.

Confusional state is a more profound deficit that includes disorientation, bewilderment, and difficulty following commands.

Lethargy consists of severe drowsiness in which the patient can be aroused by moderate stimuli and then drift back to sleep.

Obtundation is a state similar to lethargy in which the patient has a lessened interest in the environment, slowed responses to stimulation, and tends to sleep more than normal with drowsiness in between sleep states.

Stupor means that only vigorous and repeated stimuli will arouse the individual, and when left undisturbed, the patient will immediately lapse back to the unresponsive state.

Coma is a state of unarousable unresponsiveness.

It is helpful to have a standard scale by which one can measure levels of consciousness. This proves advantageous for several reasons: Communication among health care personnel about the neurologic condition of a patient is improved; guidelines for diagnostic and therapeutic intervention in certain situations can be linked to the level of consciousness; and in some situations a rough estimate of prognosis can be made based partly on the scale score. In order for such a scale to be useful it must be simple to learn, understand, and implement. Scoring must be reproducible among observers. The Grady Coma Scale (Table 57.1) has proved functional in this regard. It has been used for more than 10 years at Grady Memorial Hospital in Atlanta, Georgia, to gauge the level of consciousness of patients in the neurosurgical intensive care unit and elsewhere. The grade I patient is only slightly confused. The grade II patient requires a light pain stimulus (such as a sharp pin tapped lightly over the chest wall) for appropriate arousal, or may be combative or belligerent. The grade III patient is comatose but will ward off deeply painful stimuli such as sternal pressure or nipple twist with an appropriate response. The grade IV patient reacts inappropriately with either decorticate or decerebrate posturing to such deeply painful stimuli, and the grade V patient remains flaccid when similarly stimulated.

Many other coma scales have been developed. Most are tailored to specific subsets of patients and are designed not only to reflect level of consciousness but also to include additional data so that more reliable comparisons can be made for research purposes or more reliable prognostic determinations can be made. An example of such a scale is the Glasgow Coma Scale (Table 57.2). In this scale the normal state merits a score of 15, and as level of consciousness deteriorates, the score becomes less.