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© 2013 Academy of Geriatric Physical Therapy, APTA