Page 206 - Cardiac Nursing

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182 PA R T I I / Physiologic and Pathologic Responses
sleep deprivation is associated with reduced metabolic activity in pital Sleep Questionnaire, 97 Sleep Disorders Questionnaire, 98
the frontal lobes, thalamus, and midbrain, which may be associ- sleep diaries, visual analogue scales, Leed’s Sleep Evaluation Ques-
ated with the state of reduced alertness. 80,81 tionnaire, 99 and interviews. 93,100,101
Daytime sleepiness can also be measured using subjective
Renal Function in Sleep measures such as the Epworth Sleepiness Scale, an instrument that
has been widely used in the clinical and research settings. 102–105
Urine flow is reduced and more concentrated during sleep with a Test scores greater than 10 or 11 have been reported in patients
decreased excretion of sodium, chloride, potassium, and calcium. with sleep disorders that cause excessive daytime sleepiness (EDS);
The mechanisms involved in these changes are complex and in- the average score for control subjects is 6 (possible range of scores
clude changes in renal blood flow, glomerular filtration, hormone is 0 to 24; higher score greater subjective sleepiness). 102,106 Al-
secretion (vasopressin, aldosterone, prolactin, parathormone), and though the results of studies examining the relationship between
sympathetic neural stimulation. 82 Because night-time potassium Epworth Sleepiness Scale scores and sleep apnea severity, for ex-
excretion is reduced, potassium infusions given at night may lead ample, have been equivocal, 11,107,108 improvement in scores after
to higher serum levels than daytime infusions. 83 treatment of apnea with continuous positive airway pressure
From infancy to old age, males have penile erections (nocturnal (CPAP) has been described. 109,110 Thus, the instrument may be
penile tumescence) during REM sleep. Total tumescence time is sensitive to and particularly helpful in evaluating clinical re-
greatest just before and during puberty and then may gradually de- sponses to interventions designed to improve sleep (Display 8-1).
cline. Sleep-related erectile activity can be monitored to aid in dif-
ferentiating physical and psychological components of impotence. 84
Behavioral Assessment
Endocrine Function in Sleep Assessment of behaviors related to sleep and sleepiness are an im-
portant part of a thorough assessment. In fact, observation is con-
Endocrine hormone secretion is influenced by sleep. For example, sidered the “gold standard” for sleep monitoring in infants. 15
growth hormone secretion is highly sleep-dependent and most se- Typically, individuals who are sleepy or sleep-deprived manifest
cretion occurs during the first few hours after sleep onset during characteristic behaviors including yawning, eye rubbing, head
SWS. If sleep is advanced or delayed, growth hormone secretion nodding, ptosis of the eyelids, irritability, and slowed movement.
shifts accordingly. In contrast, thyroid hormone and cortisol se- Other observable waking behaviors that may be noted include au-
cretions have independent circadian rhythms. Thyroid hormone tomatic behavior, unintentional sleep episodes, cataplexy (a
secretion increases in the late evening; cortisol concentration in- stereotypical feature of narcolepsy in which there is a sudden
creases in the latter half of the night and peaks toward the end of decrement in muscle tone and loss of deep tendon reflexes leading
the normal sleep period or soon after awakening. 85 to muscle weakness, paralysis, and/or postural collapse), and sleep
The hormone melatonin, secreted by the pineal gland, induces drunkenness. 10 Although lying quietly in a horizontal position is
sleepiness and has a marked circadian rhythm that is closely linked typical, movements and position changes can occur and are a nor-
to the light–dark cycle, temperature, and cortisol rhythms. A late mal part of sleep behavior. Abnormal sleep-related behaviors in-
evening surge in melatonin begins at darkness, approximately 2 clude bizarre postures, restless sleep, jerking of the extremities,
hours before bedtime, and is considered a marker of the body’s cir- seizure activity, and dream enactment. Video recordings of these
cadian timing system. Secretion peaks at approximately 3:00 AM behaviors during polysomnography (PSG) are often made to as-
but is suppressed by daylight to levels that are barely detectable. sist in the assessment and diagnosis of sleep problems. Observa-
Bright light exposure suppresses melatonin secretion and can be tions of patients’ nocturnal behaviors by health care providers, bed
used to help reset a person’s circadian clock. 86 partners, or parents often play an important role in the diagnosis
and treatment of sleep disorders.
CLINICAL EVALUATION, Objective Measurement
DIAGNOSIS, AND APPROACHES
The structure and timing of sleep stages and cycles can be studied
There are three primary ways in which sleep and sleepiness are objectively using PSG, a procedure involving the simultaneous
measured: subjectively, behaviorally, and objectively. In health, recording of the EEG, the EMG, and the EOG. At the usual record-
these measures are often, but not always, congruent; however, ing speed of 1 cm/s, a standard 30-cm page represents a 30-second
they become much less well associated when impaired sleep or period, or epoch. Each epoch is assigned a single sleep-stage score
other health problems are present. 87–92 based primarily on changes in EEG frequency (in cycles/s, or hertz
[Hz]) and amplitude (in microvolts [ V]), with confirmation by
Subjective Measurement the EOG and EMG patterns. 12 In addition to sleep-staging sig-
nals, PSG often includes the measurement of other physiological
Subjective measures of sleep can be particularly useful for screen- parameters, such as respiratory movements of the chest and ab-
ing, triage, and assessing the effects of treatment. 15,93 Types of in- domen, airflow at the nose and mouth, Sa O2 , electrocardiogram
formation typically obtained include an individual’s assessment of and leg movements (anterior tibialis EMG).
sleep latency (time from lights out to the onset of sleep), number Daytime sleepiness (daytime sleep propensity or tendency) can
of awakenings, depth and length of sleep, refreshing quality of be quantified using the Multiple Sleep Latency Test (MSLT). 105 Be-
sleep, satisfaction with sleep, and soundness of sleep. This infor- ginning 1.5 to 2 hours at the end of a nocturnal polysomnographic
mation can be collected through the use of sleep questionnaires, recording, four to five 20-minute nap opportunities are typically
that is, the Pittsburgh Sleep Quality Index, 94–96 St. Mary’s Hos- given in 2-hour intervals. The sleep latency of any given nap