Hoffman, Julie E. PT, DPT, CCS; Paschal, Karen A. PT, DPT
The West Nile Virus (WNV) was first identified in the blood of an infected Ugandan woman in 1937.1 Outbreaks of WNV worldwide were somewhat limited until the mid-1990s with the notable exceptions of Israel in the 1950s and South Africa in 1974.2 Since the mid-1990s, there has been a worldwide increase in numbers of human and horse illness and avian deaths, as well as an increase in severity in humans.3–7 This is likely due to the evolution of the WNV.2 The first human cases of WNV in the Western hemisphere were reported in 1999 in the New York City area resulting in 7 deaths.8,9 The spread and exposure to WNV through the United States remained modest until 2002 when individuals in 40 states were impacted, resulting in 284 deaths.10,11 In 2003, the Centers for Disease Control and Prevention reported 9862 cases of WNV in 46 states and 264 deaths.10
Clinical manifestation of WNV varies in individuals from mild flu-like symptoms to acute flaccid paralysis. Although most people infected with WNV are asymptomatic, 20% typically develop a mild febrile illness referred to as West Nile Fever,12–14 and less than 1% develop a more severe infection, such as encephalitis, meningitis, or acute flaccid paralysis, in the central nervous system.15 Advanced age has been shown to be the most significant risk factor for developing severe neurological disease and for death.16,17 Of the 1% of patients with neuroinvasive disease, clinical presentation varies from mild neurological involvement to profound complications.14 This broad range of neurologic manifestations in adults leads to varied impairments and functional limitations, many requiring physical rehabilitation.18
Adults with severe neuroinvasive conditions more frequently require assistance and rehabilitation after the acute hospital stay.19 In a study of 228 adult patients hospitalized with WNV in Colorado, Bode et al20 reported 29% of individuals with West Nile encephalitis (WNE) discharged to a rehabilitation facility, 17% discharged to a long-term care facility, 15% discharged to home with assistance, 20% discharged without assistance, and 18% died. In a study of 57 adult patients with neurological manifestations of WNV infection in Ontario, 23% returned home unassisted, whereas 18% died, 25% were discharged to home with help, 21% were discharged to a rehabilitation hospital, 7% moved in with relatives, 4% were discharged to nursing home facility, and 4% were discharged to another acute care facility.21
Although a description of a comprehensive course of rehabilitation and subsequent functional outcomes for older adults with WNV infection has not been well documented, it has been estimated that 47% to 65% of individuals with WNE require rehabilitation, including physical, occupational, and/or speech therapy.17,22 The physical therapy management of an individual with West Nile neuroinvasive disease (WNND) has been detailed in a case report.23 In addition, a study assessing the long-term outcomes of 59 adults after WNV infection reported that 51% of those surveyed participated in physical therapy within 12 months of their WNV infection.22 Despite these references to physical therapy in the literature, little other description of the rehabilitation process or the functional outcomes of adults following a stay in a rehabilitation hospital exists.
The purpose of this study is to describe the functional impairments upon admission and the functional outcomes at discharge of 48 adult patients with WNV admitted to a rehabilitation facility in the Midwest from 2002 to 2009.
A retrospective chart review of all patients admitted to an inpatient rehabilitation hospital with a diagnosis of WNV as determined by ICD-9 (International Classification of Diseases, Ninth Revision) code after January 1, 2002, and discharged prior to December 31, 2009, was completed (N = 48). There were no children with WNV admitted during this timeframe. The diagnosis of WNV was made prior to admission to the rehabilitation hospital. This study was approved by the Creighton University and Madonna Rehabilitation Hospital institutional review boards.
General information, including sex, age, social history, employment, and living environment, on each patient was obtained. For each patient, a closer look at health-related status including general health and medical history was recorded. In addition, information specific to the current hospitalization was gathered: current conditions, functional status and activity level on admission and discharge, physical therapy care, discharge destination, and follow-up care provisions. The daily physical therapy notes were reviewed and the intervention categories outlined in the Guide to Physical Therapist Practice were utilized to classify the physical therapy interventions provided.24 Lengths of stay (LOSs) in the acute care and rehabilitation hospital as well as discharge destination and need for additional physical therapy services were also recorded.
To measure functional improvements, the Functional Independence Measure (FIM) instrument values for mobility, activities of daily living (ADL), and cognition/reasoning were utilized. FIM values were assigned upon admission and discharge for all patients. The FIM instrument is a 7-point ordinal scale that is widely used to score severity of disability. The value 7 corresponds with complete independence, while 1 is total assistance. This scale ranks 18 items that describe 6 functional areas: (1) The self-care domain includes eating, grooming, bathing, toileting, upper body dressing, and lower body dressing; (2) sphincter control includes bowel and bladder management; (3) the transfer domain reports transfer ability to bed, chair, or wheelchair, to toilet, and to tub or shower; (4) the locomotion domain scores walking or wheelchair propulsion and stair climbing; (5) communication scores comprehension and expression, and finally; 6) the social cognition domain includes social interaction, problem solving, and memory. Possible scores range from 18 to 126.
This scale has been widely utilized in various rehabilitation populations and is recognized as an appropriate indicator of burden of care as well as the need for various rehabilitation services.25,26 As one of the most widely used tools in rehabilitation, it has been studied in multiple populations for reliability and validity. The FIM mean interrater reliability level has been found to be 0.915 to 0.925 at 95% confidence level27 and the test-retest reliability has been firmly established.28 No studies reporting the minimal detectable difference with the FIM instrument in patients with WNV were found. According to Stineman et al,29 the FIM has been found to be the most valid, reliable, and responsive assessment tool for global function because it exceeds all minimal psychometric properties.
The standardized response mean (SRM) was calculated for the total, motor, and cognitive FIM scores to determine the responsiveness of the FIM in this study. Responsiveness is defined as the ability of a measure to detect clinically important change in an outcome measure.30 The SRM is one form of effect size index and is the ratio of change from pretest to posttest divided by the standard deviation of the change in scores.31 Therefore, the larger the SRM or effect size, the greater the difference in the mean amount of change or responsiveness for the instrument.32
The patients admitted to this rehabilitation hospital were assigned to 1 of 3 levels of care: acute rehabilitation, subacute rehabilitation, or the long-term acute care (LTAC) hospital unit based on their medical and physical status. Individuals who were medically stable and able to participate in 3 hours of therapy (physical therapy, occupational therapy, and/or speech therapy) were admitted to acute rehabilitation. Those medically stable but unable to tolerate 3 hours of therapy services were admitted to the subacute unit, whereas patients requiring acute medical care were admitted to LTAC. As a patient's medical and functional status changed, the patient was moved within the facility to the appropriate level of care on the basis of these criteria. Each patient received comprehensive rehabilitation by a team consisting of physical therapists, occupational therapists, speech therapists, respiratory therapists, recreational therapists, registered dieticians, social workers, case managers, spiritual care providers, physicians, nurses, and pharmacists. Individualized physical therapy was provided for each patient on the basis of need and was focused on increasing function and quality of life by improving range of motion (ROM), muscle performance, mobility, ADL, cognitive and social abilities, ease and quality of respiration, and pain reduction. The amount and focus of therapy varied depending upon patient need and level of care.
Physical therapy interventions used to treat the patients with WNV in this study were recorded using classifications identified in the Guide to Physical Therapist Practice.24 In the Guide, interventions are defined as the methods and techniques used to produce change consistent with the examination findings, evaluation, diagnosis, and prognosis of each patient. Interventions expected for all patients include coordination, communication, and documentation and patient-/client-related instruction. Procedural interventions vary and were selected, applied, and modified on the basis of individual needs.
Data were analyzed using descriptive statistics and a paired t test for residence/social support prior to infection, average LOS per patient, PMH and comorbidities, admission and discharge FIM scores, physical therapy interventions, and discharge destination with continued physical therapy. All statistics were calculated using a commercial statistical package, SigmaStat Version 3.1 (Systat Software, Inc, Chicago, Illinois).
Patients were 29 men and 19 women with ages ranging from 24 to 91 years (mean = 67.75, median = 72.5). Prior to diagnosis, the majority of patients lived at home with a spouse (Table 1). All patients were admitted to the rehabilitation from an acute care hospital with a diagnosis of West Nile Fever. The LOS in the acute care facilities ranged from 1 to 62 days.
There was a considerable range in LOS in the rehabilitation hospital, where care was provided in acute rehabilitation, LTAC, subacute care, transitional care, or skilled nursing (Table 2). Patients who were moved between levels of care had a mean LOS per level of care of 33.3 (SD = 36.7, range = 1–269) days. Patients also had significant comorbidities (Table 3). Most prevalent were hypertension (HTN), type 2 diabetes mellitus, acute respiratory failure, ventilator dependency, and pneumonia.
Functional status was measured by using the FIM instrument. Admission FIM scores ranged from 13 to 116, with a mean score of 45.8 (SD = 28.2) points. Discharge FIM scores ranged from 18 to 121, with a mean score of 75.1 ± 34.2. Progress made during inpatient rehabilitation, as documented by the admission and discharge FIM scores was statistically significant (P < 0.001) (Table 4). The SRM for the total FIM scores was 1.06, 1.12 for the motor FIM scores, and 0.79 for the cognitive FIM.
Physical therapists provided a wide range of interventions to enable patients to achieve a higher degree of function (Table 5). In addition to coordination, communication, and documentation and patient-/client-related instruction, most patients also participated in or received therapeutic exercise, functional training in self-care, and the prescription and application of devices and equipment.
The majority of patients were discharged home or to a nursing facility (46%) with skilled or extended care (38%) with a need for continued rehabilitation services (Table 6). Of the 9 patients who lived alone prior to diagnosis, 4 were discharged home and 5 were discharged to a skilled or extended care nursing facility.
Because of the surge in numbers of older adults with complications after WNV infection requiring rehabilitation, understanding functional outcomes is important to patients, families, and the rehabilitation team. This study provides some insight into the rehabilitation of adults with complications related to WNV and with multiple comorbid conditions.
Although no children with a diagnosis of WNV were admitted to this rehabilitation facility during this time period of this study, between the years 1999 and 2007, 5% of all WNV cases and 4% of WNND cases occurred in children younger than 18 years in the United States.33 Between 2004 and 2007, the median annual incidence of WNND for children was 13 times lower in children than in the older adult population older than 50 years.34 This may be because children are more likely to remain asymptomatic or to have milder disease compared with adults.35 Children with WNND were less likely (37%) to be classified as having encephalitis or meningoencephalitis than older adults (59%).34 In the children who did acquire WNND, the clinical symptoms and severity were similar to those seen in adults.36 However, the fatality rate was substantially higher in older adults (14%) than in children (1%).34 Although a large number of individual case reports and series have been published on the clinical manifestation of WNV in children, there have been no studies addressing functional outcomes including time to recover or complications.
The majority of the patients in this study were living at home independently prior to WNV infection. WNV is transmitted through the bite of a mosquito that has fed on an infected bird.37 Because an individual must be exposed to a mosquito bite, adults who are outdoors and more active, such as the patients in this study, are at greater risk for contracting WNV.21
Like previous studies, advanced age (≥65 years) appears to be a risk factor for developing serious complications from WNV infection.9,20,38,39 The mean age of patients in this study was 67.75 years, and the median age was 72.5 years. This is in contrast to a more recent study that found age was less strongly linked as a risk factor once adjustments for HTN, diabetes, and other comorbid illnesses were made.40
Patients in this study had a high number of comorbid conditions (Table 3). This is consistent with several studies that have reported that individuals with a high number of comorbidities have a negative long-term prognosis whereas patients with few preexisting conditions returned to normality more quickly or had a higher rate of physical or mental recovery than those with no underlying conditions.22,41 Patients with multiple premorbid conditions appeared to present with more severe complications, leading to a longer recovery time, likely higher health care cost, and lower overall functional outcomes.14,21
Similar to other studies, a high percentage of the study patients had HTN (43.75%) and diabetes (41.67%). One proposed mechanism to explain how diabetes might influence the development of WNND focuses on the immune impairing nature of diabetes. With diminished immunity, the magnitude and duration of WNV viremia may heighten its impact.13 Because HTN may cause disruption of the blood-brain barrier, it has been suggested that this would allow entry of the virus into the central nervous system.13 Another study found that comorbid illness such as HTN and diabetes were associated with more severe forms of WNV and increased persistence of symptoms.40
In addition to HTN and diabetes, the patients in this study had a high number of cardiovascular complications. This is consistent with previous studies that have also identified cardiovascular disease as an important risk factor for the development of more serious forms of WNV.9,20,38,39,42 In this study, 20.83% of the patients had exacerbation of or new onset of atrial fibrillation, 16.67% had chronic ischemic heart disease, and 16.67% had hyperlipidemia. Involvement with the vagal sympathetic ganglia in patients with WNE may lead to dysautonomia and therefore cardiac arrhythmias.43 Although the relationship between cardiac symptoms and WNV is not certain, clinicians working with this population should consider cardiac monitoring upon admission to a rehabilitation hospital, including measurement of heart rate and blood pressure response to activity and electrocardiogram monitoring to detect new onset and potentially life-threatening arrhythmias.
In this study, 37.5% of the patients developed acute respiratory failure and 33% were mechanically ventilated and/or had a tracheostomy tube after WNV infection. Given the high number of complicating medical factors and preexisting conditions, this study implies that older adults with inpatient rehabilitation needs had a higher level of medical complexity, resulting in an increased LOS (Table 2). This is consistent with a larger population-based study that reported complications of WNV including respiratory failure (12%) and cardiac arrhythmias (6%).20
Compared to other studies, the mortality of these patients was lower (4.17%).21,22,44 This is likely because the patients in this study were evaluated in the postacute phase of WNV infection. More deaths are likely in the acute setting. Predictive studies of patients with WNV state that age, WNE, immunosuppression, endotrachial intubation, and previous history of stroke are associated with fatal outcomes.20
Because adults with WNV infection admitted to a rehabilitation hospital have a varied past medical history and disease-related complications, the comprehensive rehabilitation team must be prepared to address the varied complications in patients with WNV infection. The patients in this study received physical therapy interventions directed at increasing muscle performance, ROM, mobility, and overall function (Therapeutic Exercise (100%), Functional Training in Self-care (95.8%), Functional Training in Work (20.8%)). The Guide24 includes the following interventions in the Therapeutic Exercise category: aerobic conditioning; balance coordination and agility training; body mechanics and postural stabilization; flexibility exercises; gait and locomotion training; neuromotor development training; and strength, power, and endurance training. For functional training, the Guide24 lists ADL training, barrier accommodations or modifications, device and equipment training, functional training programs, IADL training, and injury prevention as interventions. In addition to the functional training listed earlier, the “Functional Training in Work” category also includes leisure and play activities and training. The majority of the patients in this study (62.5%) required training with the use of an assistive device (Prescription and Application of Devices and Equipment).
Patients with WNV infection have been shown to have various movement disorders including postural instability, rigidity, and bradykinesia that may require the use of an assistive device to promote mobility and safety.14,21 In autopsy and magnetic resonance imaging studies, signs of inflammation and degenerative changes have been found in the basal ganglia and cerebellum possibility impacting these movement abnormalities.21,45 Carson et al46 reports that motor speed and manual dexterity were most significantly abnormal in patients 13 months after WNV infection. Although specific details about motor speed and manual dexterity are not known for this population at more than 1-year postinfection, 93.75% of the participants required follow-up physical therapy services.
In addition to functional mobility training, a small percentage of patients required airway clearance techniques (14.6%), manual therapy (6.3%), electrotherapeutic modalities (2.1%), and physical agents (2.1%). Because of the high incidence of respiratory involvement of the patients in this study, the physical therapists individualized therapy interventions to include airway clearance techniques as needed. Manual therapy, modalities, and physical agents were used for pain management and increasing ROM.
Because every clinical presentation of WNV infection is different, the rehabilitation team must focus on individualized care for each patient. All care is aimed at improving function and maximizing each individual's potential. Here is an example: W.M. is a 75-year-old retired farmer who contracted WNV. He was hospitalized for 3 weeks in the acute care hospital because of complications of the WNV infection including respiratory failure. Upon admission to the rehabilitation hospital, W.M. had a tracheotomy placed, and he was on mechanical ventilation for more than 50% of the time, required dependent assistance for all bed mobility and transfers, and moderate assistance to maintain static sitting balance. Because of his poor activity tolerance, he was unable to tolerate three 30-minute evaluations from physical therapy, occupational therapy, and speech therapy, so the team worked together to provide the type and amount of care he needed while still acquiring the vital baseline information from which to write goals. In addition, he required constant monitoring of vital signs and encouragement to participate because of frustration and fatigue. Communication was limited because of the tracheostomy placement. The individualized plan of care for W.M. included cotreatments between disciplines to maximize this patient's potential and not overfatigue him. The team increased the amount and specificity of therapy as the patient tolerated.
Although most of the patients in this study made considerable functional progress as demonstrated by statistically significant improvements in FIM scores (Table 4), none had complete recovery to their premorbid functional status. The variability in both admission and discharge FIM scores demonstrates the significantly different functional levels for this group of patients. This variability is greater than what has been reported in previous studies.47,48 The admission motor FIM scores suggest that most patients required maximum assistance for functional mobility; however, the patients' need for assistance ranged from complete dependence to minimal assistance. At discharge, most patients required minimal assistance for motor tasks; however, this ranged from completely dependent to independent with some supervision required.
The SRMs for the total (1.06) and motor (1.12) FIM scores represent a large change or effect size. The SRM for the cognitive (0.79) FIM score indicate a moderate change. According to Cohen's criteria, an effect size more than 0.8 is large, 0.5 to 0.8 is moderate, and 0.2 to 0.5 is considered small.49 These values indicate the FIM is a responsive instrument in this population and the change in motor and total FIM captured a large change for the WNV patients in this study.
This variability in discharge motor function explains the mixed discharge destinations. After comprehensive rehabilitation, the majority of patients were discharged to home (46%) or to a skilled nursing facility (33%) and required continued physical therapy (72.92%). Only 3 of the 48 patients (6.25%) did not require follow-up physical therapy services. This is consistent with another study that reported 51% of the individuals with WNV required physical therapy within 1-year postinfection.22 The lower discharge FIM scores help explain the need for skilled and acute care for some patients, as the FIM score provides a good indication of burden of care.50
The patients in this study had lower admission and discharge FIM values in comparison to many general neurological populations receiving inpatient rehabilitation. A study of 1502 patients admitted to an inpatient rehabilitation unit between July 2002 and June 2006 had a variety of diagnoses including stroke (57.9%), spinal cord injury (9.7%), musculoskeletal conditions (8.7%), cancer (2.4%), traumatic brain injury (2.1%), and pulmonary conditions (2.1%).51 The mean admission and discharge FIM scores reported by diagnosis were as follows: All patients: FIMAdm 70.3 (SD = 23.2), FIMDC 87.3 (SD = 23.0); Persons with spinal cord injury: FIMAdm 68.5 (SD = 21.1), FIMDC 86.6 (SD = 23.6); Persons with stroke FIMAdm 67.9 (SD = 23. 1), FIMDC 85.9 (SD = 23.0); Persons with traumatic brain injury FIMAdm 60.6 (SD = 25.6) FIMDC 82.7 (SD = 25.9).51 In comparison, the admission and discharge FIM scores for those diagnosed with WNV in this study were FIMAdm 45.8 (SD = 28.2) and FIMDC 75.1 (SD = 34.2). In another study, the outcomes of 433 patients diagnosed with stroke receiving inpatient rehabilitation were reported.52 The mean admission and discharge motor FIM scores for these patients were FIMAdm 50.1 and FIMDC 71.7. The mean admission and discharge cognitive scores were 25.0 and 28.6.52 In this current study, the patients with WNV had mean admission and discharge motor scores of 26.5 and 48.6, and the mean cognitive scores were 19.3 and 26.5. These comparable studies highlight that the individuals with WNV were at a lower functioning level at both admission and discharge in all areas compared to a general neurological population.
The functional outcomes are from a single rehabilitation hospital. Although this provides a snapshot of functional outcomes of individuals post-WNV infection in the Midwest, sampling from one facility allowed for a small number of patients. With a larger sample, correlation studies could be completed for better predictive ability. This study focuses on physical therapy intervention only. As a result, contributions of other disciplines are not specifically identified. In future studies, following up with patients after discharge from the rehabilitation hospital would provide greater insight into the long-term functional outcomes of this population. Because this study was completed retrospectively, the researchers were reliant on information available in the medical record. A prospective study would allow exploration and greater description of the type of impairments and barriers to the rehabilitation process. For example, a few studies highlighted the relationship between alcohol use and WNND. Asking questions around a patients' alcohol consumption may not be a standard line of questioning for patients with WNV admitted to a rehabilitation hospital.16,21 Finally, this rehabilitation hospital did not distinguish between WNE, West Nile meningitis, WNND, or West Nile paralysis. Further exploring these subcategories might provide greater insight into these different presentations and varied functional outcomes.20,40,41
The manifestation of the WNV is variable from patient to patient. Better understanding the impact of HTN, diabetes, and cardiovascular comorbidities on patients with WNV infection will prepare rehabilitation professionals to appropriately manage and monitor this vulnerable population during the rehabilitation process. In addition, understanding the potential outcomes for the WNV population is important to rehabilitation professionals working in a variety of practice settings. A greater understanding of functional outcomes will provide therapists', patients', and families' insight into how to individualize patient care to maximize potential and assist in discharge planning.
The authors thank Ted Kasha for his role in data analysis; Christina K. Dhesi, Amy Freuen, and Megan W. Svee for their roles in data collection; and the staff at Madonna Rehabilitation Hospital in Lincoln, Nebraska, for their assistance.
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Functional Independence Measure (FIM); rehabilitation; functional outcome; West Nile Virus
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