Logistic Regression Analysis and Nursing Interventions for High-risk Factors for Pressure Sores in Patients in a Surgical Intensive Care Unit

Xin-Ran Wang，Bin-Ru Han

General Surgical Intensive Care Unit，Xuanwu Hospital，Capital Medical University，Beijing 100053，China

Original article

Logistic Regression Analysis and Nursing Interventions for High-risk Factors for Pressure Sores in Patients in a Surgical Intensive Care Unit

Xin-Ran Wang*，Bin-Ru Han

General Surgical Intensive Care Unit，Xuanwu Hospital，Capital Medical University，Beijing 100053，China

A R T I C L E I N F O

Article history：

Accepted 20 April 2015

Published 20 June 2015

Critically ill patients

Pressure sores

Risk factors

Shock

Care

Objective:To investigate the risk factors related to the development of pressure sores in critically ill surgical patients and to establish a basis for the formulation of effective precautions.

Methods:A questionnaire regarding the factors for pressure sores in critically ill surgical patients was created using a case control study with reference to the pertinent literature.After being examined and validated by experts，the questionnaire was used to collect data about critically ill surgical patients in a grade A tertiary hospital.Among the 47 patients enrolled into the study，the 14 who developed nosocomial pressure sores were allocated to the pressure sore group，and the remaining 33 patients who met the inclusion criteria and did not exhibit pressure sores were allocated to the control group.Univariate and multivariate logistic regression analyses were employed to examine the differences in 22 indicators between the two groups in an attempt to identify the risk factors for pressure sores.

Results:According to the univariate analyses，the maximum value of lactic acid in the arterial blood，the number of days of norepinephrine use，the number of days of mechanical ventilation，the number of days of blood purification，and the number of days of bowel incontinence were statistically greater in the pressure sore group than in the control group（P＜0.05）.The multivariate logistic regression analysis revealed that the number of days of norepinephrine use and the level of lactic acid in the arterial blood were high risk-factors for pressure sores（P＜0.05）.

Conclusions:The best method for preventing and control pressure sores in surgical critically ill patients is to strongly emphasize the duration of the critical status and to give special attention to patients in a continuous state of shock.The adoption of measures specific to high-risk patient groups and risk factors，including the active control of primary diseases and the application of decompression measures during the treatment of the patients，are helpful for improving the quality of care in the prevention and control of pressure sores in critically ill patients.

ⓒ2015 Shanxi Medical Periodical Press.Production and hosting by Elsevier B.V.This is an open access article under the CC BY-NC-ND license（http://creativecommons.org/licenses/by-nc-nd/4.0/）.

1.Introduction

Pressure ulcers are skin lesions that are caused by changes in the interior and exterior environments of the skin and its own condition in response to the effects of various factors.The care of pressure ulcers has always been a focus and a difficulty in the nursing field.Because critically ill surgical patients remain in stressed states due to their critical conditions and exhibit incidences of pressure ulcers up to 14.3%-51.0%，1，2they are the key subjects of pressure ulcer prevention and control.

The Braden scale is currently the most commonly used risk assessment scale in clinical practice.This scale focuses on six factors，including perception and sensation，mobility，activity，skin humidity，nutritional status，and friction and shearing forces.However，to benefit from more active risk precautions related to pressure ulcers，the Braden scale must be used in connection the identification of additional risk factors.3Foreign investigators have revealed that there are now more than 100 types of risk factors for pressure ulcers；4therefore，the present study was designed to identify the indicators that best serve an early warning function for pressure ulcers in critical surgical patients.This study investigated the information related to patients with pressure ulcers and critically ill surgical patients who did not experience pressure ulcers during the same period and further analyzed the strong risk factors of pressure ulcers with the purpose of providing evidence for improvements in the prevention and reduction of pressure ulcers.

2.Material and Methods

2.1.Research subjects

The subjects enrolled in this study were critically ill patients who were admitted to the general surgery ICU of a grade A tertiary hospital in Beijing from January 2010 to December 2012.The inclusion criteria were as follows：patients who（1）were at least 18 years old，（2）did not suffer from pressure ulcers outside the hospital and were deemed to be at extreme risk for pressure ulcers in an initial assessment after admission to the ICU（i.e.，a Braden score≤9），（3）were in critical condition and exhibited acute physiology and chronic health evaluation II scores（APACHEⅡ）≥20 within 24 hours of entering ICU，and（4）were patients whose ICU stay was≥14 days.Among the 47 patients enrolled into this study，14 cases with pressure ulcers were allocated to the pressure ulcer group，and the remaining 33 patients without pressure sores were allocated to the control group.In the case group there were 12 males and 2 females with an average age of 70.43±15.30 years，an APACHEⅡ score of 24.29±5.01 within 24 hours in the ICU and an initial Braden score of 7.29±0.99 in the ICU，including 8 cases with severe acute pancreatitis，4 with fecal peritonitis and 2 with other severe surgical infections.According to the standard pressure ulcer classification revised by the National Pressure Ulcer Advisory Panel（NPUAP）in 2007，7 of these patients were classified into PhaseⅡ sacral pressure sores，2 cases with phase III pressure sores，1 case with a suspiciously deep sore，3 cases with phaseⅡ pressure ulcers in the heels of the feet，and 1 case with phaseⅡpressure ulcers on the knees.The average duration of the patients with pressure ulcers in the ICU was 38.57±26.42 days. There were 24 males and 9 females with an average age of 69.18±15.75 years，an average APACHEⅡ score of 23.82±3.38 within 24 hours in the ICU and an average initial Braden score of 7.04±1.07 in ICU，including 20 cases with severe acute pancreatitis，6 cases with faecal peritonitis，and 7 cases with other severe surgical infections.There were no significant differences in gender，age，APACHEⅡ score within 24 hours in the ICU，initial Braden score in the ICU or disease diagnosis between the patients in the two groups（P＞0.05）.The results were comparable.

2.2.Research methods

The methods of a retrospective study were adopted. The questionnaire regarding the pressure ulcer risk factors was self-designed based on the related literature from all countries of the world and proceded through 2 rounds of assessment by 6 clinical nursing specialists prior to its application.The content validity of the questionnaire was 0.91.The authors collected data regarding the 47 participants that included the following 22 indicators：gender，age，body weight，length of ICU stay，APACHEⅡscore within 24 h in the ICU，initial Braden score，the lowest blood albumin value，the highest lactic acid value in the arterial blood，the administration of vasoactive agents（e.g.，noradrenaline），the maxi-mum dose and the total number of days on noradrenaline，the efficacy and number of days on mechanical ventilation，the consciousness of the patient，the administration and number of days on sedatives，the condition and the total number of days of blood purification therapy，the conditions of skin oedema and severe oedema（severe oedema referred to severe oedema in the systematic tissue with tension and lustre of the skin where it drooped on the body），and the number of days of incontinence.Based on the medical records and primary laboratory sheets，the data were investigated and recorded item-by-item and examined via statistical descriptions and analyses following collection.

2.3.Statistical methods

All data were analyzed with SPSS version 18.0 after completing the input into a computer by specially assigned persons.The main statistical analysis methods included rank sum tests，chi-square tests，and single factor and multiple factor non-conditional logistic regression analyses，and P＜0.05 was considered to indicate statistical significance.

3.Results

3.1.Comparisons of the indicators between the two groups

By comparing the clinical data between the 14 patients with pressure ulcers and the 33 patients without pressure ulcers，the peak level of lactic acid in the arterial blood，the number of days on noradrenaline，the number of days of mechanical ventilation，the number of days of blood purification therapy，and the number of days of incontinence in the pressure ulcer group were found to be statistically greater than those in the control group（z values of-2.865，-2.879，-2.224，-1.988 and-1.930，respectively，P＜0.05）.There were no significant differences in the remaining 17 indicators between the two groups，which indicate that the 5 indicators were the ones that were potentially related to the development of pressure ulcers.

3.2.Single-factor logistic regression analyses of pressure ulcer risk factors

Using the development of pressure sores as the dependent variable and the 22 indicators as the independent variables in single-factor non-conditional logistic regression analyses revealed that the 5 indicators that were significantly different between the two groups were closely related to the development of pressure ulcers（P＜0.05）. No significant differences were observed in the remaining variables as listed in Table 1.

3.3.Multivariate logistic regression analysis of the risk factors for pressure ulcers

According to the above analytic results，the factors with significant effects in the single-factor logistic regression analyses were introduced into the multivariate logistic regression model.As shown in the results，the peak level of lactic acid in the arterial blood and the number of days taking noradrenaline contributed as the independent risk factors for pressure ulcers（P＜0.05）as listed in Table 2.

Table 2 Multivariate logistic regression analysis of the risk factors for pressure ulcers.

4.Discussion

4.1.Substantial emphasis should be placed on the durations of patients'critical conditions in the prevention and control of pressure ulcers.

It has been shown that the risk of developing pressure ulcers increases as the APACHEⅡscore increases；therefore，use of pressure ulcer risk assessment scales（e.g.，the Braden score）is needed in clinical practice to predict and prevent pressure ulcers.5The 47 cases in this study were relevant to the prevention and control of pressure sores because all cases conformed to the inclusion criteria in terms of critical conditions，extremely high risks for pressure ulcers and long therapeutic times in the ICU.In the literature，foreign studies have confirmed that the occurrence of pressure ulcers is associated with factors，such as unstable hemodynamics，the use of vasoactive agents，edema，hypoxemia and abnormal weight，6，7and our previous research demonstrated that factors，such as unstable blood circulation（particularly hypotension），renal failure and the use of sedatives are also risk factors for pressure ulcers.8Based on an extensive literature search and our own studies，22 indicators were identified in this study for deep analysis and research.Comparisons of the indicators between the two groups revealed that the level of lactic acid in the arterial blood，the number of days on noradrenaline，the number of days on mechanical ventilation，the number of days receiving blood purification，and the number of days of incontinence were significantly greater in the pressure ulcer groups than in the control group（P＜0.05）.To confirm the correlations of the 5 indicators with the development of pressure ulcers，we conducted single-factor logistic regression analyses of the 22 indicators.The results shown in Table 1 revealed that the 5 indicators were indeed closely related to the occurrence of pressure ulcers（P＜0.05）.These findings suggest that the duration of organ dysfunction in critically ill patients may be a risk factor for pressure ulcers.Therefore，great importance should be attached to the duration of the critical conditions of patients for the care of pressure ulcers，and pressure ulcer prevention and control techniques should continuously，constantly，carefully and earnestly performed every day，every shift and every hour.

4.2.Special attention should be paid to patients in a continuous state of shock for the prevention and controlof pressure ulcers

We found that 5 indicators were highly related to the development of pressure ulcers via the single factor analyses.To further identify the independent risk factors for pressure ulcers，we included these indicators in a multivariate non-conditional logistic regression model and found that a high level of lactic acid in the arterial blood and the time receiving noradrenaline were the high-risk factors for pressure ulcers as shown in Table 2.The 47 cases in this study were all critically ill patients with severe surgical infections；87.5%of these patients concurrently developed septic shock and depended on vasoactive agents（e.g.，noradrenaline）to sustain their blood pressures.Although no significant difference（P＞0.05）existed between the two groups in terms of noradrenaline use（χ2value，2.988）or maximum dose（z value，-1.848），the time of noradrenaline use（P＜0.01）and the lactic acid concentration in the arterial blood（P＜0.01）were significantly greater in the case group than in the control group.The fact that lactic acid concentrations in the arterial blood increased with the duration of the use of vasoactive agents proves that the hypoxic conditions of the tissues and organs and hypoperfusion9were worsened by increasing durations of shock. Shock patients with clammy skin which are piebald and exhibit ischemia and hypoxemia are very likely to develop pressure ulcers，and the continuation of the shock status further increases the risk of skin lesion.Therefore，in addition to patients with Braden scores that indicate risk，special attention should also be paid to patients with high levels of lactic acid and those who have been on vasoactive agents for longer durations，which means that important control and prevention measures should be continuously applied for patients who are in continuous states of shock because this is a high-risk group.

4.3.The key issue of pressure ulcer prevention and control lies in the adoption of measures that are specific to high-risk patients and factors

The fundamental measures of pressure ulcer prevention and control in critically ill surgical patients include the adoption of effective rescue measures by the medical staff，the most rapid possible recoveries of the stabilities of functions such as blood circulation，respiration and kidney activity，and the shortening of the duration of the critical condition while paying special attention to the active treatment of shock，including the immediate correction of hemodynamic disorders through fluid resuscitation，the recovery of effective perfusions of the important organs，improving the microcirculation，reducing the lactic acid levels in the arterial blood and the use of vasoactive drugs.These measures can fundamentally prevent pressure ulcers.

Active interventions can be adopted during the rescue of patients to prevent pressure ulcers.Among these，decompression is the important measure for pressure ulcer prevention and control.Because patients in the supine position cannot achieve decompression by turning over，nurses are required to provide air beds for each patient and to assess the effectiveness of the beds every shift. Once any uninflated or under-inflated air bed is detected，the nurse must determine the problem and solve it immediately.Based on the application of air beds，hydrocolloid or soft silicone dressings can be stuck to the protruding parts of the patients'bones to facilitate blood circulation in the local skin and strengthen the anti-pressure abilities of the skin.Moreover，high molecular polymers can be added between the decompression dressings and air beds at the part of sacrum and the heel that are most vulnerable to pressure ulcers to further relieve the oppression of the body weight.

Furthermore，when identifying patients at high risk for the development of pressure ulcers，the medical staff should be required to implement the disclosure of pressure ulcer risk and prevention measures through positive and repetitive communication with relatives of the patients to prevent nurse-patient disputes.

5.Conclusions

As the development of a pressure ulcer is multifactorial and complex，the identification of the risk factors forthis condition is of great importance to the adoption of the corresponding precautions.This study verified several risk factors related to the development of pressure ulcers in critically ill surgical patients.The enhancement of monitoring and the active implementation of precautions are needed，particularly for patients with these risk factors，which further validates the effects of constant and practical improvements of the quality of critical care.

Conflicts of interest

All contributing authors declare no conflicts of interest.

References

1.Lindgren M，Unosson M，Krantz AM，Ek AC.Pressure ulcer risk factors in patients undergoing surgery.J Adv Nurs.2005；50：605-612.

2.Paul JB，Keller A.Pressure ulcers in intensive care patients：a review of risks and prevention.Intensive Care Med.2002；28：1379-1388.

3.Gerri C，Marjorie F.Factors associated with pressure ulcers in patients in a surgical intensive care unit.J Wound Ostomy Continence Nurs.2010；37：619-626.

4.Tweed C，Tweed M.Intensive care nurses'knowledge of pressure ulcers：Development of on Assessment Tool and Effect of an Educational Program.Am J Crit Care.2008；17：338-346.

5.Ye XH，Peng NH，Jiang FZ，et al.The application of APACHEⅡ score system in SICU nursing supervision.Chin Nurs Manag.2011；2：36-38［in Chinese］.

6.Fernandes LM，Caliri MH.Using the Braden and Glasgow scales to predict pressure ulcer risk in patients hospitalized at intensive care units.Rev Lat Am Enfermagem.2008；16：973-978.

7.McCord S，McElvain V，Sachdeva R，et al.Risk factors associated with pressure ulcers in the pediatric intensive care unit.J Wound Ostomy Continence Nurs.2004；31：179-183.

8.Wang XR，Han BR，Wei JZ.The analysis of pressure ulcer risk factors using Braden score in high risk critically ill patients.Chin J Modern Nurs.2010；16：44-46.

9.Amold RC，Shapiro NI，Jones AE.Multicenter study of early lactate clearance as a determinant of survival in patients with presumed sepsis.Shock.2009；32：35-39.

19 January 2015

in revised form 22 March 2015

.

E-mail address：xwsicu2011@163.com（X.R.Wang）.

Peer review under responsibility of Shanxi Medical Periodical Press.

http：//dx.doi.org/10.1016/j.cnre.2015.04.004.

2095-7718/ⓒ2015 Shanxi Medical Periodical Press.Production and hosting by Elsevier B.V.This is an open access article under the CC BY-NC-ND license（http：//creativecommons.org/licenses/by-nc-nd/4.0/）.