INTRODUCTION
Sleep is the state of natural rest observed
throughout the animal kingdom, in all mammals and birds, and in many
reptiles, amphibians, and fish. In humans, other mammals, and many
other animals that have been studied - such as fish, birds, ants,
and fruit-flies - regular sleep is necessary for survival. The
capability for arousal from sleep is a protective mechanism and also
necessary for health and survival.
DEFINITION
Sleep can e defined as a normal state of
altered consciousness during which the body rests; it is characterized
by decreased responsiveness to the environment, and a person can be
aroused from it by external stimuli.
INCIDENCE & CHARACTERISTICS:
Sleep is generally characterized by a reduction
in voluntary body movement, temporary blindness, decreased reaction
to external stimuli, loss of consciousness, a reduction in audio
receptivity, an increased rate of anabolism (the synthesis of cell
structures), and a decreased rate of catabolism (the breakdown of cell
structures.
Almost a third of the general population has
some problems with sleep during any given year. More than half of the
9000 participants in a study of sleep in elderly persons (65 years or
older) reported the following as sleep pattern disturbance that they
experience most of the time:
- Trouble falling asleep
-
Frequent awakening
-
Waking too early
-
Needing to nap
-
Not feeling rested
These disturbances may be secondary to
situational, environmental or developmental stressors, or they may be
associated with illness or with pre-existing disorders. The
relationship is often reciprocal, in that the disorder decreases sleep
& the decreased sleep affects the disorder.
CHRONOBIOLOGY
Chronobiology refers to the study of biologic changes as they occur in relation to time. The sleep wake cycle is one of the circadian rhythms of the body. Circadian rhythms
follow an approximate 24 hour cycle through a complex process linked
to light & dark. The effect of illness & hospitalization may
disrupt these rhythms, particularly in older persons. Ultradian cycles
are circadian rhythms of less than 24 hours. The recurrent pattern of
sleep stages, repeating approximately 90 minutes in adults, is an
example. Chronopharmacology refers to the
study of how biorhythms affect the absorption, metabolism, &
excretion of drugs. E.g.the blood level achieved by a continuous
infusion of heparin varies throughout the day.
PHYSIOLOGY OF SLEEP:
The timing of sleep- wake cycle & other
circadian rhythms, such as body temperature, is controlled by the
suprachiasmatic nucleus in the anterior hypothalamus. Located above
the optic chiasm, this area receives input from the retina, which
provides information about darkness & light. The suprachiasmatic
nucleus controls the production of melatonin, which is believed to be a
potent sleep inducer.
Arousal from sleep, wakefulness and the ability to respond to stimuli rely on an intact reticular activating system
(RAS). The RAS is located in the brain stem & contains
projections to the thalamus & the cortex. The diffuse network of
neurons in the RAS is in a strategic position to monitor ascending and
descending stimuli through feedback loops.
Although the RAS provides anatomic framework
for arousal, it is the neurotransmitters that serve as the chemical
messengers. The onset of sleep and of each subsequent sleep stage is
an active process involving delicate shifts in the balance of several
of these neurotransmitters.
The transition from wake state to non- rapid eye movement
(NREM) sleep is marked by decreases in the concentrations of
serotonin, norepinephrine, and acetyl choline. The later transition to
rapid eye movement (REM) sleep is marked by a dramatic
increase in acetylcholine and further decrease in serotonin and
norepinephrine. As REM sleep continues, the concentrations of
serotonin and norepinephrine increase, eventually stopping REM sleep.
Cholinergic activation with the release of acetylcholine seems to
re-establish REM sleep. The continuous interaction of these 2 systems
is thought to produce the normal alterations between NREM and REM
sleep. Other neurotransmitters, such as gamma- amino butyric acid
(GABA) and dopamine are also believed to have a part in the reciprocal
processes involved in shifts in sleep state. All of these
neurotransmitters are actively involved in the waking process as well.
STAGES OF SLEEP
Sleep can be defined behaviorally, functionally
and electro physiologically. Electro physiologic monitoring of sleep
is called Polysomnography includes at least 3 parameters L1)
brain wave activity, (2) eye movements and (3) muscle tone.
Polysomnography shows that sleep can be divided into REM and NREM.
NREM sleep can be further divided into 4 stages. The stages vary in
depth, but are characterized by slow rolling eye movements, low level
and fragmented cognitive activity, maintenance of moderate muscle tone,
and slower, but generally rhythmic respirations and pulse rate.
NREM sleep is characterized as follows:
Stage 1:
- includes lightest level of sleep
-
stage lasts a few minutes
-
decreased physiological activity begins with gradual fall in vital signs and metabolism
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sensory stimuli such as noise, easily arouse sleeper
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if awakened, person feels as though daydreaming has occurred
Stage 2:
- includes period of sound sleep
-
relaxation progresses
-
arousal is still relatively easy
-
stage lasts 10 – 20 mts
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body functions continue to slow
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the brain waves are frequently mixed and low voltage in pattern, with bursts of activity called sleep spindles and large amplitude waves called K complexes
Stage 3:
- it involves initial stages of deep sleep
-
sleeper is difficult to arouse and rarely moves
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oxygen consumption
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muscles are completely relaxed
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vital signs decline, but remain regular
-
stage lasts 15 – 30 mts
Stage 4:
- it is deepest stage of sleep
-
it is very difficult to arouse sleeper
-
If sleep loss has occurred, sleeper will spend considerable portion of night in this stage
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Vital signs are significantly lower than during waking hours
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Stage lasts approximately 15 – 30 mts
-
Sleep walking and enuresis sometimes occur
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Stage 3 and 4 known as slow wave sleep, named for the characteristic high voltage and low – frequency delta waves
REM sleep:
- Vivid, full- color dreaming occurs
-
Stage usually begins about 90 mts after sleep has begun
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Stage typified by autonomic responses of rapidly moving eyes, fluctuating heart and respiratory rates, and increased or fluctuating blood pressure
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Loss of skeletal muscle tone occurs
-
Gastric secretion increase
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It is very difficult to arouse sleeper
-
Duration of REM sleep increases with each cycle and averages 20 mts
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Stage is characterized by low voltage, random fast waves, as in stage 1 NREM
SLEEP CYCLE
Normally an adult’s routine sleep pattern
begins with a pre-sleep period during which the person is aware only
of a gradually developing sleepiness. This period normally lasts 10 –
30 mts. individuals experiencing difficulty in falling asleep often
remain in this stage for an hour or more.
Once asleep, the person passes through 4 – 6
complete sleep cycles; each consists of 4 stages of NREM sleep and a
period of REM sleep. The cyclical pattern usually progresses from
stage 1 through stage 4 of NREM, followed by a reversal from stage 4
to 3 to 2, ending with a period of REM sleep.
With each successive cycle, stages 3 and 4 of
NREM sleep shorten and the period of REM lengthens. REM sleep lasts up
to 60 mts during the last sleep cycle. The number of sleep cycle
depends on the amount of time that the person spends sleeping, in an
average of 90 mts.
FUNCTIONS OF SLEEP
The purpose of sleep is still unclear. Theories suggest that:
- It is a time of restoration and preparation for the next period of wakefulness
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During NREM stage 4 body releases human growth hormone for the repair and renewal of epithelial and specialized cells such as brain cells
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Protein synthesis and cell division for the renewal of tissues occur during rest and sleep
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REM sleep appears to be important for cognitive restoration
The benefits of sleep often go unnoticed until a
person develops a problem resulting from sleep deprivation. A loss of
REM sleep leads to feelings of confusion. Various body functions (
eg. Motor performance, memory and immune function) alter when
prolonged sleep loss occurs
NORMAL SLEEP REQUIREMENTS & PATTERNS
Sleep duration and quality vary among persons of all age groups
- Infants 16 Hours /Day
-
Toddlers 12 Hours /Day
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Preschoolers 11 Hours /Day
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Schoolers 9 - 10 hours /day
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Adolescents 8 – 9 hours /day
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Adults 6 – 8 hours /day
As people age, their circadian clock advances,
causing advanced sleep phase syndrome. The syndrome is common in older
adults and often is the reason behind the complaint of waking early
in the morning and unable to get back to sleep. They get sleepy early
in the evening.
FACTORS AFFECTING SLEEP
A number of factors affect the quality and quantity of of sleep. Often more than one factor combined to cause a sleep problem.
- Physical illness (eg. Nausea, mood disorders, breathing difficulty, pain)
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Drugs and substances (eg. Tryptophan)
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Lifestyle (eg. Daily routines, exercises)
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Usual sleep patterns and excessive daytime sleepiness
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Emotional stress
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Environment ( ventilation)
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Sound
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Exercise and fatigue
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Food and caloric intake
SLEEP DISORDERS
Sleep pattern disturbance
is a nursing diagnosis that is defined as a disruption of sleep time
that causes discomfort or interferes with a desired life cycle. A sleep
pattern disturbance may be related to one of more than 80 sleep
disorders identified in the international classification of sleep
disorders, a partial list of which is given below:
International classification of sleep disorders
|
| Dyssomnias Intrinsic sleep disorders
Parasomnias Arousal disorders
Parasomnias usually associated with REM sleep
Associated with mental disorders Associated with neurologic disorders Associated with medical disorders Proposed sleep disorders |
I, DYSSOMNIAS
The Dyssomnias include sleep disorders
characterized by difficulty in initiating or maintaining sleep
(insomnia) or by excessive sleepiness. These disorders may arise
predominantly from within the body (intrinsic), from external sources
(extrinsic), or from disruption of circadian rhythm.
A. Intrinsic sleep disorders
1. Insomnia:
It is the persistent difficulty in initiating
or maintaining sleep. The difficulty does not respond readily to
improved sleep habits or removal of precipitating factors. Idiopathic insomnia
is a rare disorder characterized by a lifelong history of inability
to obtain adequate sleep. Its cause is thought to be an abnormality in
the neurologic control of sleep. Psycho physiologic insomnia is
more common and is characterized by learned sleep – preventing
associations and heightened physiologic response to stress. It can be
confirmed by polysomnographic recording, which usually shows the same
pattern of long sleep latency or fragmentation that the client
describes. The total sleep time is often within normal range but is
felt to be inadequate. They will fall asleep unintentionally in low
stimulus situations, such as watching TV, but feel increased arousal
when they go to bed. It is difficult to get sleep in places , other
than their usual bedroom.
Management of insomnia is complex. Sleep should
be restricted by curtailing time bed to the minimum believed
necessary with a consistent rising time. Relaxation exercises can be
helpful, but they should initially be practiced at times other than
bedtime so that by the time they are introduced at bedtime, they are
effective. Referral to a sleep specialist or mental health
professional who can work with the client over a period of time should
be considered.
2. Narcolepsy
Narcolepsy is one of the disorders
characterized by excessive daytime sleepiness. The client also
experiences disturbed nocturnal sleep and repeated episodes of almost
irresistible daytime drowsiness followed by brief periods of sleep,
especially when engaged in monotonous activities. Many Narcoleptic
clients also experience cataplexy, a sudden
loss of muscle tone at times of unexpected emotion (eg. Fright).
Malfunctioning of the mechanism controlling REM sleep leads to sleep paralysis for one to several minutes, and hypnagogic hallucinations i.e. Hallucinatory experiences that occur at sleep onset or awakening.
On polysomnography, the most characteristic
finding is sleep onset REM periods. Narcolepsy is genetically related
condition with autosomal dominance in some cases. The effects of
disease on lifestyle are significant- many clients reporting episodes
of having fallen asleep at work, while driving, or both
Medical management consists of low doses of
stimulants to improve alertness and tricyclic antidepressants to
control cataplexy. It is important that they maintain a regular
schedule with adequate nocturnal sleep. Recommend regular naps at
times when clients are prone to increased sleepiness. Safety is the
major issue in these clients.
3, Sleep apnea syndrome:
Sleep apnea is characterized by cessation of
breathing for 10 seconds or longer occuring at least 5 times / hour.
Sleep apnea can be classified as obstructive and central nervous
system apnea. A combination of the two may be seen.
Obstructive Sleep apnea syndrome:
In Obstructive Sleep apnea syndrome, respiratory efforts of the
diaphragm and intercostals muscles are apparent but ineffective against a
collapsed or obstructed upper airway. Snoring indicates partial
obstruction. As hypoxia ensues; the person eventually awakens to
breathe. The frequent awakenings impair the normal sleep cycle.
Repeated micro arousals lead to daytime sleepiness.
Women are less likely than men to develop Obstructive
Sleep apnea syndrome, particularly before menopause. It is common
among males who are obese with short, thick necks, and who are heavy
snorers. A much smaller percentage progresses to the classic
pickwickian syndrome, characterized by obesity, severe sleep apnea,
daytime hypercapnea, and cor pulmonale.
The application of continuous positive airway
pressure (CPAP) by means of a face mask covering the nose is the
treatment of choice for clients with moderate to severe Obstructive Sleep
apnea syndrome. The CPAP device provides room air under increased
pressure, essentially providing a pressure splint to keep the upper
airway open. It should be turned on whenever the client is ready to go
to sleep and should be maintained throughout the sleep period.
Clients may experience nasal congestion, air leak, pressure marks on the
face, or pressure intolerance. People who use CPAP regularly should
bring their units to the hospital with them. These clients need to be
monitored when recovering from anesthesia, and when receiving
narcotics because they are at risk for developing ineffective
breathing patterns.
Uvulopalatopharyngoplasty is a common surgical
procedure for reducing snoring. Resecting the uvula, the posterior
part of the soft palate, tonsils and any excessive pharyngeal tissue,
can reduce the propensity to obstruction. Tracheostomy may be required
in severe Obstructive Sleep apnea syndrome.
Central Sleep apnea syndrome: it
is characterized by apneic periods during which no apparent
respiratory effort occurs. It may be seen in stroke and brain stem
involvement, but it is most commonly mixed with Obstructive Sleep
apnea syndrome. Cheyne- stokes respirations are common, and CPAP is
the usual treatment.
4. Periodic limb movement disorder
It may also contribute to daytime sleepiness
and frequent nocturnal wakening. Originally described as nocturnal
myoclonus, it is characterized by periodic episodes of repetitive,
stereotypic leg movements that occur during sleep, causing partial
arousals. It is common in the elderly population. Clonazepam, a
benzodiazepine, or baclofen, a skeletal muscle relaxant, may be
ordered to diminish the magnitude of the movement and frequency of
arousals. For some clients the use of transcutaneous electrical nerve
stimulation (TENS) before sleep has been helpful.
5. Restless leg syndrome:
Restless leg syndrome involves anything
“crawling”, itching or tingling sensations of the leg while at rest
and causes an almost irresistible urge to move. The syndrome is often
most severe before sleep onset. Clients always have periodic limb
movements during sleep. Treatment is similar to that of Periodic limb
movement disorder.
B. Extrinsic sleep disorders
It encompasses a range of factors, from
environmentally to chemically induced. Some environmental factors
temporarily present during hospitalization.
1. Circadian rhythm sleep disorders
In the general population, the Circadian rhythm sleep disorders, such as time zone change syndrome and shift work sleep disorder
are not uncommon. Elderly and chronically ill clients who live alone
may be vulnerable to irregular sleep- wake patterns. In this disorder,
prolonged ignoring or absence of external cues to time, such as regular
meal timings, work periods and daylight leads to erratic periods of
sleeping and wakefulness. Internal circadian cues may also be damped
as a result of ageing or diffuse brain disease.
Management includes maintenance of regular
schedule and exposure to natural sunlight. Light therapy is being
used to facilitate adjustments in Circadian rhythms. the usual dosage
is about 5000 lux- hours, which may be taken as 2500 lux for 2 hours,
5000 lux for 1 hour, or 10,000 lux for 30 minutes. It should begin
only under the guidance of a physician. Side effects include
eyestrain, headache and irritability. Presence of retinopathy, glaucoma
or cataract is a contraindication.
II. PARASOMNIAS:
The Parasomnias are disorders that occur during
sleep but that usually do not produce insomnia or excessive
sleepiness. It may be due to partial arousal or abnormalities in
sleep-wake transition.
A. Arousal disorders
Partial arousal occur during slow- wave sleep. Sleepwalking, also known as somnambulism,
may include semi purposeful behaviour, such as dressing. However the
behaviour may be lacking in coordination and appropriateness, such as
voiding in the closet. . The occurrence of sleep walking in adults is
associated with anxiety. Sleep terrors are
sudden arousals from slow wave sleep accompanied by screaming,
tachycardia, tachypnea, diaphoresis, and other manifestations of fear.
If awakened, the person is often disoriented and has little recall of
the nature of the dream image. Sleep terrors usually occurs in young
children.
B. Sleep-wake transition disorders
Sleep-wake transition disorders are common in the general population. Sleep starts
refers to the sudden jerking movement of the legs that often occurs
as a person is falling asleep. Nocturnal leg cramps also common. The
frequency andand intensity may be greater with high caffeine intake,
stress, or intense physical activity before going to bed. . Sleep talking also may occur during times of stress.
C. Parasomnias usually associated with REM sleep
Nightmares are frightening dreams that arise in REM sleep and are often vividly recalled on awakening. Sleep [paralysis
is one of the classic signs of narcolepsy, but can occur in
isolation. This effect may be an extension of the normal state of low
muscle tone during REM sleep.
D. Other Parasomnias
Other Parasomnias are not specifically associated with particular sleep stage. Sleep bruxism refers to grinding of the teeth during sleep and may lead to dental damage. Sleep enuresis, or bed wetting, may occur in adult in association with other disorders, such as Obstructive Sleep apnea syndrome. Primary snoring is distinguished from Obstructive Sleep apnea syndrome by its rhythmic nature without episodes of apnea or hypoventilation.
III. SLEEP DISORDERS ASSOCIATED WITH MEDICAL OR PSYCHIATRIC DISORDERS
A. Neurotransmitter imbalances
Neurotransmitter imbalances predispose to sleep
pattern disturbances. It is more common in case of Parkinson’s
disease, depression, and Alzheimer’s disease. These imbalances may be
disease related or drug – induced.
B. Head injury
Head injury of all degrees of severity affects
sleep pattern. For clients in the confused, agitated stage of recovery
that results from more severe head injury, use of environmental cues
(e.g. light and darkness), regularity of daily schedule, and
appropriate daytime exercise and activity can help to restore the
sleep – wake cycle.
C. Hormonal imbalances
Hormonal imbalances also contribute to sleep
pattern disorders. Hyperthyroid clients tend to have fragmented, short
sleep periods with an excess of slow wave sleep. Hypothyroidism is
characterized by excessive sleepiness, and polysomnographic recordings
show a reduction in the proportion of slow- wave sleep. Clients with
type 1 diabetes mellitus may experience hypoglycemic attacks during
the night. Sleep patterns normally vary across the menstrual cycle in
response to estrogen and progesterone levels. Women with premenstrual
syndrome tend to have less slow- wave sleep throughout the menstrual
cycle than their asymptomatic peers. Postmenopausal women are at
higher risk for experiencing snoring and Obstructive Sleep apnea
syndrome.
D. Respiratory disorders
Chronic airway limitations such as asthma and
emphysema contribute to difficulty in initiating sleep, frequent
arousals with shortness of breath or cough, and chronic fatigue. Some
medications such as theophylline preparations may contribute to
insomnia.
E. Cardiovascular disorders
The Cardiovascular diseases such as
hypertension, myocardial infarction, and nocturnal angina leads to
Obstructive Sleep apnea , hypoxemia, frequent arousals, increased
stage 1 sleep ,and reduced total sleep time.
F. Gastrointestinal disorders
In duodenal ulcer, gastric acid secretion is
higher than average and recurrent awakenings with epigastric pain are
common, especially in the first 4 hours and antacids needs to be
administered. Advice to raise the head of the bed on blocks and to
avoid eating within 3 hours of bedtime to avoid gastro esophageal
reflux that may lead to esophagitis in severe cases.
G, Other disorders
Numerous Other disorders such as, skin
conditions (atopic eczema), fibromyalgia, and seizures seem to have an
effect on or an association with sleep.
IV. HOSPITAL ACQUIRED SLEEP DISTURBANCES
Clients in the hospital may report various
types of sleep disturbances. The etiologic mechanism and intervention
may differ from each other.
A. Sleep onset difficulty
It is because of the strange environment and
the anxieties associated with illness and hospitalization.
Environmental control, such as reduction of noiseand interruptions,
and conservative relaxation measures, such as a back rub should be
tried before resorting to a hypnotic agent
B. Sleep maintenance disturbance
It may be associated with substance use or
withdrawal from a variety of medications and related substances.
Alcohol hastens sleep onset but leads to awakening later in the night.
Internal stimuli, such as pain, discomfort, and the urge to void are
frequent disturbers of sleep. External stimuli include environmental
factors, such as light, noise, temperature, as well as disruptions by
other people. Nocturnal stimuli can be reduced by darkening the room,
turn lights off, close curtains, reduce noise, adjust temperature by
providing bed coverings, spacing necessary care giving activities, and
by coordinating the nature and timings of interruptions by other care
givers.
C. Early morning awakening
It occurs frequently among elderly. Sleep is
disturbed in depression and delirium, and is grossly disturbed with
frightening dreams, disorientation and restlessness.
D. Sleep deprivation
The noise level, 24 hour lighting, and
frequency of care giver interruptions create sensory overload and
sleep deprivation, which is thought to be a major factor contributing
to postoperative psychosis.
ASSESSMENT AND MANAGEMENT
Diagnostic assessment:
- Polysomnography
-
Electroencephalogram
-
Multiple sleep latency test (MSLT)
MSLT is performed to assess the impairment of
daytime alertness. It is performed a day after a standard
polysomnogram. The time required for clients to fall asleep when in a
relaxed state is evaluated at 2 hour intervals, with each nap limited
to 20 minutes. The type of sleep also is assessed.
NURSING PROCESS
A. Assessment: Assess
client’s usual sleep habits and recent sleep quality as part of the
initial nursing history. If sleep quality is reported to be poor,
explore the nature of
disturbances by noting the following:
- Usual activities in the hour before retrieving
-
Sleep latency
-
Number and perceived cause of awakenings
-
Regularity of sleep pattern
-
Consistency of rising time
-
Frequency and duration of naps
-
Events associated with initial onset of sleep disturbances
-
Ease of falling asleep in places other than the usual bedroom
-
Situations in which client fights sleepiness
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Daily caffeine intake
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Use of alcohol, sleeping pills,and other medications
-
Incidence of morning headaches
-
Frequency of snoring, apparent pauses in breathing, and kicking movements
-
Objective data may include visible signs of fatigue and lack of sleep, such as circles under the eyes, lack of coordination, drowsiness and irritability.
B. Nursing diagnosis:
1. Disturbed sleep pattern related to changes in routine due to hospitalization and pain
Or
Disturbed sleep pattern related to lack of cues
for day- night schedule; manifested by erratic sleep schedule,
frequent naps and nocturnal wandering
C. Client Outcome criteria:
client increases nocturnal sleep time by 20% over next 2 weeks.
| D. Nursing intervention | Rationale |
| *offer meals at regular times, corresponding to client’s previous pattern *provide active meaningful activities during daytime hours, including exposure to natural light, and an outdoor environment when possible *monitor frequency and duration of naps *create an individualized bedtime ritual that includes a quieting activity, a light carbohydrate snack, going to the bathroom and settling a routine * Do not waken even if incontinent. Change and assist the client to the bathroom when he or she spontaneously awakens *if turning or other care is necessary, try to provide for periods up to 2 hours of undisturbed sleep time whenever possible |
*mealtimes are important social cues, that reinforce circadian rhythms, which tend to weaken with advancing age *light exposure is communicated through the retina to the suprachiasmatic nucleus, helping to set the circadian clock *napping is not contraindicated but is best at the time of day opposite to the midpoint of the nocturnal sleep period. Short naps are preferable to avoid deep sleep *reduced stimulation and rituals associated with sleep enhance sleep onset *older adults who can turn themselves generally do better to have their sleep undisturbed and tend to waken spontaneously if wet when their sleep cycle lightens * Sleep cycles average 90 mts. A sleep latency of 20- 30 mts mean it would take about 2 hours to experience a full sleep cycle. |
SUMMARY
The adequacy of sleep is important factor in
caring for clients with acute and chronic illness. Some sleep
disturbances are temporary and related to the stress of
hospitalization. It is possible that temporary stress problems will be
corrected only after the client’s return home. Clients with sleep
disturbances may need follow –up care with repeated assessments to
determine whether the problem was corrected. Clients with long term
sleep disorders may need ongoing support to maintain the effectiveness
of treatment. The nurse can play a pivotal role in environmental
modification and client teaching to minimize the impact of sleep.
REFERENCES
- Black JM, Hawks JH. Medical Surgical Nursing clinical management for positive outcomes. Vol 1.7th edition. Saunders; India 2005 Pp 461-500.
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Potter PA, Perry AG. Basic nursing- essentials for practice. 6th edition. Missouri: Mosby publishers; 2007
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Brunner. Medical surgical nursing. 6th edition. London: Mosby publishers; 2005.
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Lewis SM, Heitkemper MM, Dirksen SR. Medical surgical nursing. 6th edition. Philadelphia: Mosby publishers; 2004.
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Tylor C, Lillis C, Le Mone P. fundamentals of nursing- the art and science of nursing care. 5th edition. London: Lippincott Williams & Wilkins publishers; 2006
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Lewis, Heitkemper, Dirksen. Medical Surgical nursing.6th edition. Mosby. Page no 131-157
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