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162 PART 2: General Management of the Patient

increased mortality. 8-10 Up to 25% of patients requiring MV for greater
• Paul T, Lemmer B. Disturbance of circadian rhythms in analgose- than 7 days develop ICUAW, and a systematic review of 24 studies
11
dated intensive care unit patients with and without craniocerebral including patients with sepsis, multiorgan failure, or prolonged MV
injury. Chronobiol Int. 2007;24:45-61. identified neuromuscular dysfunction in 46% of patients. Furthermore,
9
• Rechtschaffen A, Bergmann BM, Everson CA, Kushida CA, long-term follow-up studies of survivors of critical illness have demon-
Gilliland MA. Sleep deprivation in the rat: X. Integration and dis- strated significantly impaired health-related quality of life and physical
cussion of the findings. Sleep. 1989;12(1):68-87. functioning up to 5 years after ICU discharge, with weakness being the
• Silber MH, Ancoli-Israel S, Bonnet MH, et al. The visual scoring of most commonly reported physical limitation. 12,13
sleep in adults. J Clin Sleep Med. 2007;3(2):121-131. Factors such as systemic inflammation, medications (particularly
• Tung A, Lynch JP, Mendelson WB. Prolonged sedation with pro- corticosteroids), electrolyte disturbances, and immobility have been
14,15
pofol in the rat does not result in sleep deprivation. AnesthAnalg. implicated in the pathogenesis of ICU-AW. Although no one has sys-
2001;92:1232-1236. tematically measured immobility during ICU care, clinicians acknowl-
edge its presence during the earliest days of critical illness, particularly
• Watson PL, Pandharipande P, Gehlbach BK, et al. Atypical sleep during deep sedation or neuromuscular blockade, specific MV strategies
in ventilated patients: empirical electroencephalography findings (eg, prone ventilation), and other advanced support (eg, continuous
and the path toward revised ICU sleep scoring criteria. Crit Care hemodialysis).
Med. 2013;41(8):1958-1967.
• Weinhouse GL, Watson PL. Sedation and sleep disturbances in the
ICU. Crit Care Clin. 2009;25:539-549. BED REST AND IMMOBILITY
• Williams K, Hinojosa-Kurtzberg M, Parthasarathy S. Control of Rest is necessary for the natural repair of weakened or damaged tissue
breathing during mechanical ventilation: who is the boss? Respir and remodeling of muscle. Bed rest is most often accompanied by sleep,
Care. 2011;56(2):127-139. a process necessary for normal neurologic, immune, and endocrine
function. The average person rests for 6 to 9 hours per day during sleep
and shorter periods of rest may occur at other times. When people are
REFERENCES ill, they often sleep and rest for longer periods. 16
Prolonging rest has the potential for several benefits during general
Complete references available online at www.mhprofessional.com/hall illness. For the injured body part, rest may avoid pain. By avoiding
unnecessary exertion, metabolic resources may be maximally utilized
for healing. During critical illness, reducing oxygen consumption by
muscles may help preferentially deliver oxygen to injured or hypoxic
CHAPTER Physical Therapy organ systems. Similarly, in patients with respiratory failure, oxygen
requirements and minute ventilation needs may be reduced. For hyper-
24 William Schweickert tensive patients, rest may lower blood pressure, potentially preventing
myocardial ischemia and dysrhythmias. Finally—and perhaps the most
Amy J. Pawlik
John P. Kress common reason for prescribed bed rest in the hospital—confinement
to bed reduces the risk of harmful falls in delirious and weak patients.
Investigations have only found a few select studies demonstrating
KEY POINTS benefits from bed rest. For example, women with preeclampsia had
reduced fetal complications when prescribed bed rest. Additionally,
17
• Survivorship from critical illness may include substantial neuro- bleeding complications after cardiac catheterization and liver biopsy
muscular weakness that can persist for many years following the were reduced with short-term bed rest following the procedure. 18-20
index hospitalization. However, the therapeutic value of sustained bed rest is questionable.
• Immobility can commonly accompany supportive care. Under- Trials of rheumatoid arthritis, low back pain, uncomplicated myocar-
standing the effects of bed rest and immobility on muscle, heart, dial infarction, pulmonary tuberculosis, and deep venous thrombosis
and nervous system is necessary to balance the risks and benefits have demonstrated improved outcomes when bed rest was limited or
21
of early mobilization. avoided. Physical activity has beneficial effects on organ and system
• Early physical therapy can be performed safely despite ongoing function; sustained rest prevents these benefits and risks serious
complications.
critical illness.
• Alternative strategies for mobilization include cycle ergometry and
neuromuscular stimulation. INACTIVITY AND MUSCLE WEAKNESS
• Successful early mobility programs include criteria for safe Experimental models of prolonged physical inactivity include space
mobilization, which focus on the neurologic, cardiovascular, and flight, immobilization of a limb, lower limb suspension, and bed rest.
22
pulmonary criteria. Such experiments carefully controlling activity—modeled in both human
and animal research—yield consistent results. Muscle mass, as assessed
by computed tomography and magnetic resonance imaging, decreases
INTRODUCTION—SURVIVORSHIP by approximately 1.5% to 2.0% per day during the first 2 to 3 weeks of
enforced rest. Although total numbers of muscle fibers seem to remain
In the last quarter century, research developments have led to improve- unchanged as a result of immobilization, reductions in the cross-sectional
ments in diagnosis and resuscitation of critically ill patients, particularly area of the individual muscle fibers, changes in the satellite cells, and
those undergoing mechanical ventilation (MV). With these improve- alterations in the distribution and size of the capillaries and connective
1-4
ments, survival for many populations of critically ill patients has tissue occur. Antigravity muscles have been observed to lose contractile
increased. Accordingly, intensive care unit (ICU) outcomes research proteins, particularly the Type I fibers of myofilaments, with a corre-
4-7
has expanded, documenting substantial morbidity in survivors. ICU- sponding increase in noncontractile tissue content, including collagen.
acquired weakness is a common problem following critical illness and Various measures of muscle strength demonstrate weakness that
is associated with prolonged hospitalization, delayed weaning, and parallels the changes in muscle size. For example, maximal knee extensor

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