Nursing Management of Sleep Disorders

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
  • sensory stimuli such as noise, easily arouse sleeper
  • 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
  • body functions continue to slow
  • 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
  • oxygen consumption
  • muscles are completely relaxed
  • 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
  • Vital signs are significantly lower than during waking hours
  • Stage lasts approximately 15 – 30 mts
  • Sleep walking and enuresis  sometimes occur
  • 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
  • Stage typified by autonomic responses of rapidly  moving eyes, fluctuating heart and respiratory rates, and increased or fluctuating blood pressure
  • Loss of skeletal muscle tone occurs
  • Gastric secretion increase
  • It is very difficult to arouse sleeper
  • Duration of REM sleep increases with each cycle and averages 20 mts
  • 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
  • During NREM stage 4 body releases human growth hormone for the repair and renewal of epithelial and specialized cells such as brain cells
  • Protein synthesis and cell division for the renewal of tissues occur during rest and sleep
  • 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
  • Preschoolers     11 Hours /Day
  • Schoolers         9 - 10 hours /day
  • Adolescents      8 – 9  hours /day
  • 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)
  • Drugs and substances (eg. Tryptophan)
  • Lifestyle (eg. Daily routines, exercises)
  • Usual sleep patterns and excessive daytime sleepiness
  • Emotional stress
  • Environment ( ventilation)
  • Sound
  • Exercise and fatigue
  • 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
  • Psycho physiologic insomnia
  • Narcolepsy
  • Obstructive sleep apnea syndrome
  • Central sleep apnea syndrome
  • Periodic limb movement disorder
  • Restless leg syndrome
Extrinsic sleep disorders
  • Inadequate sleep hygiene
  • Environmental sleep disorder
Circadian rhythm sleep disorders
Parasomnias
Arousal disorders
  • Sleep walking
  • Sleep terrors
Sleep – wake transition disorders
Parasomnias usually associated with  REM sleep
  • Nightmares
  • Sleep paralysis
Other Parasomnias
  • Sleep bruxism
  • Sleep enuresis
  • Primary snoring
Sleep disorders associated with medical or psychiatric disorders
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
  • Daily caffeine intake
  • 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
  1. Black JM, Hawks JH. Medical Surgical Nursing clinical management for positive outcomes. Vol 1.7th edition. Saunders; India 2005 Pp 461-500.
  2. Potter PA, Perry AG. Basic nursing- essentials for practice. 6th edition. Missouri: Mosby publishers; 2007
  3. Brunner. Medical surgical nursing. 6th edition. London: Mosby publishers; 2005.
  4. Lewis SM, Heitkemper MM, Dirksen SR.  Medical surgical nursing. 6th edition. Philadelphia: Mosby publishers; 2004.
  5. 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
  6. Lewis, Heitkemper, Dirksen. Medical Surgical nursing.6th edition. Mosby. Page no 131-157

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