Abstract & Commentary
Preventing Long-term Complications in Survivors of Critical Care
By David J. Pierson, MD, Editor, Professor, Pulmonary and Critical Care Medicine, Harborview Medical Center, University of Washington, Seattle, is Editor for Critical Care Alert.
Synopsis: Abnormal pulmonary function, neuromuscular weakness, psychiatric symptoms, impaired cognitive function, and reduced quality of life are common and severe among survivors of critical illness. Practical measures can be identified for their prevention, key among which are minimization of sedation and early mobilization in the ICU.
Source: Desai SV, et al. Long-term complications of critical care. Crit Care Med 2010 Oct 14; Epub ahead of print.
Desai and colleagues carried out a comprehensive review of published studies on long-term complications among survivors of critical illness in an attempt to find common characteristics and themes that might be used in developing strategies for preventing or mitigating them. That a large and expanding evidence base is available on this important aspect of critical care is illustrated by the 145 references cited by the authors in their review.
Although clinicians take justifiable satisfaction in discharging patients from the ICU alive and improving after a bout of life-threatening acute illness, it has become clear that numerous long-term, patient-relevant outcomes are less favorable than those clinicians would wish. Depending on the patient population, during the first year after initially surviving a critical illness, between one-fourth and two-thirds of patients will die. Among most of those who survive the first year, physical and psychosocial impairments interfere substantially with both daily activity and quality of life (QOL). The most studied of these impairments are listed in the table (see below), along with identified risk factors for their development and severity and practical measures for prevention.
Studies on pulmonary function after critical illness have mainly focused on survivors of the acute respiratory distress syndrome (ARDS). Obstructive, restrictive, and pulmonary vascular impairments may occur, with a reduced diffusion capacity for carbon monoxide (indicating loss of functional capillary surface area) the most common finding. Pulmonary function tests typically continue to show improvements for about 6 months. Many patients regain normal values for most measures, although exercise desaturation may persist, and the diffusion capacity may remain abnormal for years. No mechanical ventilation strategy has been shown to impact these findings among ARDS survivors, although patients requiring prolonged ventilatory support appear more likely to have a persistently abnormal diffusion capacity. It stands to reason that anything shortening the duration of mechanical ventilation should reduce the likelihood of long-term pulmonary function impairment. A substantial body of good-quality evidence supports minimizing sedation, with daily "sedation vacations" along with spontaneous ventilation trials to detect readiness for weaning and extubation, in pursuit of this goal.
In the last decade it has become increasingly appreciated that neuromuscular complications in critical illness survivors are both very common occurring in about half of such patients and disabling. While critical illness itself plays an important role, and particularly the systemic inflammatory effects of sepsis and multiple organ dysfunction, evidence points increasingly to immobility and excessive sedation as main predispositions to the several recognized forms of ICU-acquired weakness. Hyperglycemia and hypoglycemia have each been implicated, emphasizing the importance of avoiding both during critical illness. Avoiding the use of systemic corticosteroids and neuromuscular blocking agents, as well as deliberate measures to avoid prolonged immobility, are also key elements in prevention.
Studies of activities of daily living, 6-minute walk distance, and other assessments of physical functioning demonstrate that many ICU survivors suffer severe impairment as they attempt to resume their pre-ICU lives. Pre-existing impairment in these things correlates strongly with its presence and severity after critical illness, as does the development of ICU-acquired illness such as ventilator-associated pneumonia. However, impaired physical functioning is also correlated with prolonged mechanical ventilation and the use of corticosteroids. An increasing body of evidence supports the preventive strategy of early and aggressive mobilization and other physical therapy.
Post-traumatic stress disorder, depression, and anxiety are increasingly recognized long-term complications of critical illness. Their incidence and severity are strongly correlated with the presence of delirium, particularly traumatic or delusional memories of the ICU experience. Although it may seem counterintuitive, psychiatric complications occur most commonly and most severely in patients who have received more not less sedation, as well as in those who have been restrained. As with ICU-acquired weakness, hypoglycemia appears to be an important predisposing factor. Avoidance of hypoglycemia, as well as minimization of sedation, avoidance of physical restraints, and deliberate measures to orient and communicate with the patient throughout the ICU stay, should be emphasized for prevention.
Heavy sedation, delirium, and hypoglycemia have been associated with impaired cognitive function following critical illness, which is present at 1 year in about half of all patients. It is more common and more severe in individuals with lower pre-ICU intelligence. Although there are no specific prospective studies, the avoidance and aggressive treatment of delirium, as well as of hypoglycemia, would appear to be key preventive measures.
Finally, although existing studies are not ideal, it seems clear that QOL is seriously impaired among many if not most ICU survivors. Impairments have been found in all QOL domains except bodily pain, particularly with respect to physical functioning. Reduced QOL in comparison with age-matched population norms has been found as long as 5 years after an acute illness requiring ICU care. Associated factors for incidence and severity include preexisting disease and QOL impairment and the severity of the acute illness, but also the occurrence of ICU-acquired weakness and delusional memories of the ICU. In addition to the prevention of the latter as mentioned above, providing patients with a rehabilitation handbook, including self-directed exercises and a patient diary, has been shown to improve physical function-related QOL after 6 months.
As the authors of this article state, "the goals of critical care must extend beyond patient survival and include shared, multidisciplinary collaboration to prevent and manage the long-term complications of critical care." Fortunately there are practical, evidence-based steps that intensivists and others in the critical care environment can take to further these goals.
In the table (above) are several common threads with respect to both risk factors and preventive measures. Although how glycemic control in critically ill patients should best be accomplished is presently controversial, it is clear that the avoidance of both hypoglycemia and severe hyperglycemia are important for numerous outcomes, including long-term complications among survivors. The avoidance of unnecessary prolongation of mechanical ventilation the prevalence of which has been demonstrated by numerous studies, along with practical, system-type interventions for its mitigation is a general theme. So is the prevention, early detection, and effective management of delirium.
Perhaps the most important steps, vital to achieving the above preventive measures, as well as to preventing virtually all of the complications discussed by Desai et al, are avoidance of excessive sedation and early mobilization. The benefits of both are unquestioned, yet both are easier said than done in the culture of most ICUs today. Needham and colleagues at Johns Hopkins Hospital have demonstrated the feasibility of aggressive physical medicine and rehabilitation in the ICU commencing within one or two days of admission, even while patients are intubated and ventilated and several of their recent publications provide practical guidance for institutions in which this important aspect of critical care has not yet been implemented.1-4
- Needham DM, et al. Technology to enhance physical rehabilitation of critically ill patients. Crit Care Med 2009;37 (10 Suppl):S436-S441.
- Needham DM,et al. Early physical medicine and rehabilitation for patients with acute respiratory failure: A quality improvement project. Arch Phys Med Rehabil 2010;91:536-542.
- Zanni JM, et al. Rehabilitation therapy and outcomes in acute respiratory failure: An observational pilot project. J Crit Care 2010;25:254-262.
- Needham DM, Korupolu R. Rehabilitation quality improvement in an intensive care unit setting: Implementation of a quality improvement model. Top Stroke Rehabil 2010;17:271-281.