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Skin Integrity and Pressure Injuries

Risk Factors

Pressure injury formation is a complex process that is still not clearly understood despite years of research. While the amount, duration and frequency of the applied pressure, the soft tissue’s response to loading, and the role of shear and/or friction are crucial, individual patient characteristics need to be assessed as well. Intrinsic factors such as diagnosis, history of previous tissue breakdown or surgical repair, body build, posture, muscle atrophy, nutritional status as well as magnitude and distribution of interface pressures must be considered.

Extrinsic factors are also important including number of hours sitting or lying in wheelchair or bed, types of activities performed while sitting, level of functional independence, type of wheelchair, cushion and bed surface used and the support surface microenvironment, environment (climate, continence, temperature), finances; family/caregiver support; living arrangements and ease of follow up (Krouskop et al. 1983; Garber et al. 2007; Fleck & Sprigle 2007; Reger et al. 2007).

Observational study is the typical method of identifying risk factors. The analytical methodology used for each study is highly variable and makes for difficult comparisons between studies. Typically risk factors are categorized into demographic (e.g., sex, age, education, occupation, marriage), physical/medical (e.g., SCI factors, nutritional status, co-morbidities, mobility, pressure injury history, bowel/bladder incontinence/moisture, sensory perception, body build), and psychosocial factors such as mental status, social support, living conditions and financial status. Marin et al. (2013) conducted a systematic review and identified that clinical (e.g., spinal lesion characteristics, pre-existing history of pressure injuries) and functional (e.g., independence in pressure injury management) aspects serve as risk factors specific to the SCI population compared the general population.

Author YearCountry
Research Design
Score
Total Sample Size
Methods Outcome
Systematic Reviews
Marin et al. 2013
United Kingdom
Review of published
articles between 1980-
2011
AMSTAR=8
N=5
Method: A systematic review including prospective cohort, retrospective record reviews and clinical trials that identified risk factors associated with pressure injury development and recurrence in SCI populations using multivariate analytical techniques.
Databases: MEDLINE, EMbase and Cochrane.
Level of evidence: Level 2 (prospective cohort study); level 4 (retrospective cohort study and retrospective record review); level 5 (observational study and longitudinal panel cohort)
Questions/measures/hypothesis: To identify risk factors predictive of pressure injury development in adults with SCI.
1. 18 risk factors were identified and classified into six themes: sociodemographic, neurological, functional clinical, biological and medical care management.
2. Risk factors for both the general and SCI-specific populations were similar but functional and hospital management emerged as specific risk factor domains for the SCI population.
3. Findings were based on a small number of studies highlighting the need for further confirmatory work to reduce pressure injury development and recurrence and to provide a foundation for SCI risk assessment development.
Gelis 2009
France
Review of published
articles between 1966 and
2008
AMSTAR=8
N=6 Studies
Method:
Systematic Review of Literature.
Databases:
Medline (1966), Embase (1980), Pascal (1990), Reedoc (1977).
Level of evidence:
Moderate Level of Evidence
Questions/measures/hypothesis: Determine pressure injury risk factors correlated to the patients with SCI, medical care management during the acute as well as in the rehabilitation and chronic stages. This first part focuses on identifying the risk factors during the acute and rehabilitation stages.
1. Risk factors during the acute stage of an SCI are essentially linked to care management and treatment modalities.
2. There is insufficient evidence to make a recommendation on medical risk factors, however, low blood pressure on admission to the Emergency Room, with a moderate level of evidence.
Interventional Studies
Jan et al. 2011
USA
Prospective Controlled
Trial
N=23
Population: Mean age: 31.3 yr; Gender: males=11, females=12; Level of injury: paraplegia=4, tetraplegia=7, healthy controls=12.
Intervention: Patients underwent thermally induced maximal sacral skin blood flow oscillations (BFO), which were measured by laser Doppler flowmetry.
Outcome Measures: Multifractal detrended fluctuation analysis (MDFA) was used to characterize nonlinear complexity of metabolic (0.0095 to 0.02 Hz), neurogenic (0.02 to 0.05 Hz), and myogenic (0.05 to 0.15 Hz) BFO.
1. Maximal vasodilation was significantly smaller in people with SCI than in nondisabled controls.
2. Metabolic BFO exhibited less complexity in people with SCI.
3. Neurogenic BFO exhibited less complexity in people with complete SCI.
4. Myogenic BFO did not show significant differences between people with SCI and nondisabled
controls.
Li et al. 2011
China
Prospective Controlled
Trial
N=20
Population: Mean age=36.5 yr; Gender: males=14, females=6; Level of injury: patients with SCI=10, health subjects=10.
Intervention: External pressure of 26.6 kPa (200 mmHg) was applied to the sacrum via a specifically designed indentor. The subjects were examined lying face-down. Ultrasound equipment was used to analyze the structure and depth of the tissue on the sacrum area.
Outcome Measures: Tissue oxygenation signal was monitored for 20 min prior to and after the loading period from the tissue over the sacrum area using near-infrared spectroscopy (NIRS). With spectral analysis based on wavelet transform, five frequency intervals were identified (I, 0.005-0.02 Hz, II, 0.02-0.06 Hz, III, 0.06-0.15 Hz, IV, 0.15-0.40 Hz and V, 0.40-2.0 Hz) corresponding to endothelial related metabolic, neurogenic, myogenic, respiratory and cardiac activities, respectively. Waterlow Scale was used for the pressure injury risk assessment.
1. [HbO2] and [Hb] component significantly lower during rest conditions in SCI vs. healthy subjects.
2. During the post-loading period, the response of [HbO2] and [Hb] oscillatory activities were significantly lower in the tissue over the sacrum for persons with SCI than that for normal subjects.
3. Significant negative correlation between oscillatory activities and Waterlow scale in persons with SCI.
Wilczweski et al. 2012
USA
Case Series
N=94
Population: Median age range: 51-65 yr; Gender: males=72, females=21; Level of injury: C1-C4 incomplete injuries=32, unknown=62.
Intervention: Retrospective chart review of patients included in study, to identify potential risk factors for pressure injury development.
Outcome Measures: Primary outcome was the development of a pressure injury. If pressure injury was present, the documented stage was recorded (i.e., stage I, II, III, and IV).
1. Risk factors significantly correlated with development of new pressure injuries:
• Fecal management system
• Incontinent of urine
• Acidosis
• Type of bed surface
• Use of steroids
• Additional equipment
• Prolonged hypotension
2. Prolonged periods of hypotension were the greatest predictor of pressure injuries.
Rabadi et al. 2011
USA
Case Series
N=87
Population: Mean age: 60 yr; Gender: males=85; females=2; Level of injury: cervical=44, thoracic=44, lumbosacral=10; Severity of injury: AISA A=32, B=12, C=21, D=19 and E=3.
Intervention: Retrospective chart review of patients included in study, to identify potential risk factors for pressure injury development.
Outcome Measures: Basic demographics, presence of modifiable risk factors including: Hypertension, diabetes mellitus, hyperlipidemia, current smoking; presence of depression, incontinence and results from
blood drawn from hemoglobin level, blood urea nitrogen, creatinine and albumin levels and lipid profile on initial enrolment.
1. Comparisons between those with and without pressure injuries found no significant differences for the demographic variables of age, gender, age of SCI onset, or SCI duration, but there was a trend for the groups to differ in ethnicity (p=0.05).
2. The presence of modifiable vascular risk factors including hypertension, diabetes mellitus, hyperlipidemia, and current smoking did not differ between those with and without pressure injury.

Summarized Level 5 Evidence Studies

Although Saunders et al. (2010) support the notion of race as a risk factor (Guihan 2008), Saunders et al. (2010) found that African Americans with SCI are at higher risk for pressure injury development when they fall in a lower income level. Similar populations in Canada are not subject to this risk factor likely as a result of universal healthcare (Noreau et al. 2009). Gelis et al. (2009) also reported a similar finding and attributed the primary risk factor to the differing social-medical characteristics (e.g., level of education, access to healthcare) as proxy for the race risk factor (e.g., being African American). Garber et al. (2000) suggested that having a pressure injury in the previous three years raises the risk of a subsequent ulcer, especially if the patient is younger at the age of SCI onset and self-reports as being at higher risk. Verschueren et al. (2011) found that the strongest risk factor for pressure injury occurrence was having had a pressure injury during acute rehabilitation; further, they noted that this is not addressed in any of the seven pressure injury assessment scales reviewed, including those widely adopted such as the Braden, Norton and Waterlow. Eslami et al. (2012) identified that lack of an intimate partner predisposed males with lower education and longer post-SCI periods to pressure injuries. Guihan et al. (2008) suggested that difficulties for visual inspection on darkly pigmented skin may be a proxy for race, in general, as a risk factor. Idowu et al. (2011) found that lower nurse-patient ratios was a risk factor for pressure injury development and suggested an optimum ratio of one nurse to three patients. This is in contrast to the ratio of one nurse to seven patients that resulted in 50% of patients developing pressure injuries after admission into a neurosurgical trauma unit. Body build, as reflected by fat infiltration, scar tissue within muscle and fat, and spasticity were considered by Sopher et al. (2011) to be risk factors for pressure injury development in individuals with SCI.

Discussion

Many studies have found that those most likely to develop pressure injuries fall into a typical demographic population: males who have lower levels of education and are unemployed (Byrne & Salzberg 1996; Schryvers et al. 2000; Ash 2002; Richards et al. 2004).

Physical and medical factors include the biggest range of identified factors. Other physical/medical risk factors that have been identified most often include limitation in activity and mobility, injury completeness, moisture from bowel and bladder incontinence, lack of sensation, muscle atrophy, poor nutritional status and being underweight (DeLisa & Mikulic 1985; Salzberg et al. 1996; Krause et al. 2001). Rabadi et al. (2011) found that only ethnicity (p=0.05) was significantly different between those with and without pressure injuries, other than differences due to severity of the lesion. Gelis et al. (2009) also revealed an important difference to risk factors in the acute versus chronic care stages of SCI in that risk factors are mostly care-related in the acute SCI stage.

Other physical/medical risk factors include smoking (Lamid & Ghatit 1993; Salzberg et al. 1996; Niazi et al. 1997; Krause et al. 2001), number of comorbidities especially renal, cardiovascular, pulmonary disease and diabetes (Salzberg et al. 1996; Niazi et al. 1997; Ash 2002), residing in a nursing home/hospital (Byrne & Salzberg et al. 1996), autonomic dysreflexia (Salzberg et al. 1996), anemia and hypoalbuminemia (DeLisa & Mikulic 1985; Scivoletto et al. 2004), spasticity, a history of previous ulcers (Vidal & Sarrias 1991; Byrne & Salzberg 1996; Guihan et al. 2008), an increase in tissue temperature (Fisher et al. 1978), and race and ethnicity (Guihan et al. 2008; Saladin & Krause 2009). However, Rabadi et al. (2011) did not find that modifiable vascular risk factors such as hypertension, diabetes mellitus, hyperlipidemia and current smoking, were related to the prevalence of pressure injury presence in a group of 87 veterans with SCI. They further showed that the groups were similar for age, gender, age of SCI onset, or SCI duration.

Although some aspects of cardiovascular disease are considered modifiable, the absence of neurogenic control of vascular activity renders blood flow occlusion secondary to unrelieved pressure unmodifiable. This reduced vascular response has been shown to have a negative correlation to the Waterlow scale resulting in early tissue damage (Li 2011). Jan et al. (2011) confirmed this unmodifiable vascular characteristic in people with SCI compared to nondisabled controls. Thomas (2010) further stated that despite pressure relief diligence, tissue perfusion dysfunction in SCI is an unmodifiable intrinsic risk factor that needs special attention for more effective interventions. Wilczweski et al. (2012) identified hypotension as the strongest predictor of pressure injuries.

Psychosocial factors are likely the most difficult to monitor but are similarly important to consider for the prevention of pressure injuries. For example, Gelis et al. (2009) point out that behavioural factors have a bigger impact on pressure injury incidence and prevalence in the chronic stage (especially post-discharge) from both the caregiver and patient perspective. This is a concept that follows on the findings from a structured educational initiative to improve pressure injury prevention in veterans with SCI (Garber et al. 2002).

Even with the numerous risk factors associated with pressure injuries post SCI, there is limited evidence that, with more understanding of these risk factors, a decrease in pressure injury incidence will occur (Salzberg et al. 1996).

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