Risk assessment for perioperative pressure injuries*

ABSTRACT Objectives: to evaluate and classify patients according to the Risk Assessment Scale for Perioperative Pressure Injuries; verify the association between sociodemographic and clinical variables and the risk score; and identify the occurrence of pressure injuries due to surgical positioning. Method: observational, longitudinal, prospective and quantitative study carried out in a teaching hospital with 278 patients submitted to elective surgeries. A sociodemographic and clinical characterization questionnaire and the Risk Assessment Scale for Perioperative Pressure Injuries were used. Descriptive, bivariate and logistic regression analyses were applied. Results: the majority of patients (56.5%) presented a high risk for perioperative pressure injury. Female sex, elderly group, and altered body mass index values were statistically significant (p < 0.05) for a higher risk of pressure injuries. In 77% of the patients, there were perioperative pressure injuries. Conclusion: most of the participants presented a high risk for development of perioperative decubitus ulcers. The female sex, elderly group, and altered body mass index were significant factors for increased risk. The Risk Assessment Scale for Perioperative Pressure Injuries allows the early identification of risk of injury, subsidizing the adoption of preventive strategies to ensure the quality of perioperative care.


Introduction
Despite technological advances, pressure injuries (PI) caused by surgical positioning still represent a challenge for clinical practice (1) . Because they are considered complications and have a multifactorial etiology, it is difficult to assess the risk of their occurrence in surgical patients (2) , which often compromises the adoption of adequate protective measures for this clientele.
Various incidence rates of perioperative PI are described in the literature. A systematic review of 17 studies published from 2005 to 2011 that evaluated the incidence of these lesions found results ranging from 0.3% to 57.4% (3) .
International researchers also investigated the incidence of perioperative PI derived from surgical positioning and found the following rates: 12.2% in Portugal (4) , 12.7% in Italy (5) and 13% in the United States of America (USA) (6) .

Effective interventions to prevent skin lesions
involve pressure relief during and immediately after the patient lies on the surgical table, on a standard mattress.
Examples of more effective devices to prevent this type of injury are: micropulse air mattress, viscoelastic dry polymer mattress cover and gel pads (9)(10) .
The incidence of these PI varies significantly according to the clinical environment and the individual and clinical characteristics of the patient (11) . The main the extrinsic risk factors are pressure, friction and shear forces, moisture and heat (12) , and the intrinsic factors are age, body weight, nutritional status, presence of comorbidities, immobility or reduced activity levels, fecal incontinence, infection, low hemoglobin level, and surgical risk (9,(13)(14) .There are also specific intraoperative factors: prolonged surgical time, surgical positioning, use of anesthetic agents, sedation, vasoconstricting medications, type of surgery, body temperature (hypothermia), type of surgical table mattress, use of devices for positioning, and intraoperative heating and hypotension (13)(14)(15) .
Despite the existence of high technology preventive devices and the widespread use of the Braden scale in clinical nursing practice, gaps remain on the identification of factors critical to the occurrence of perioperative PI.
In this scenario, given the scarcity of intraoperative risk assessment scales of decubitus ulcers and the need to recognize the risks for elaborating individualized care plans that guarantee safe and quality perioperative care, the application of the Risk Assessment Scale for Peixoto CA, Ferreira MBG, Felix MMS, Pires PS, Barichello E, Barbosa MH. immediate preoperative period, were excluded from the study.
For sampling calculation, the following parameters were adopted: incidence of perioperative PI of 50%, accuracy of 5% and 95% confidence interval, for a finite population of 1000 surgeries, in a total of 278 participants. The recruitment process was non-probabilistic.
For data collection, we used an instrument addressing sociodemographic variables (age, sex and self-reported skin color) and clinic variables (body mass, hemoglobin values, ASA physical status classification, and atrial temperature) of the patient. The Risk Assessment Scale for Perioperative Pressure Injuries (ELPO) is composed of the following variables: duration of the surgery, type of anesthesia, surgical positioning, support surface, positioning of upper and lower limbs, comorbidities and age of the patient (16) .
Prior to data collection, a pilot test was conducted with 12 patients to verify the applicability and suitability of the instrument, but there was no need for alterations.
The researchers participated in a training moment for consensus in data collection.
Data collection occurred between February and May 2017, in three moments: preoperative, intraoperative and postoperative. In the immediate preoperative period, sociodemographic variables (age, sex, and skin color) were obtained by means of information provided by the patients at the time of admission to the hospital.
Hemoglobin values were consulted in the pre-anesthetic evaluation card or on the Web system of the laboratory of the hospital that was the field of this study. The variable presence of comorbidities was obtained through a verbal report of the patient and confirmation in the physical record. The weight and height of the patient were also collected by means of a digital scale and a vertical stadiometer (adult type Filizola®, previously calibrated) to calculate the BMI.
The Lipschitz classification was adopted for the elderly: low weight for BMI < 22 kg/m 2 , eutrophy for BMI 22-27 kg/m 2 , and obesity for BMI > 27 kg/m 2 (19) . The adoption of different parameters for the elderly is justified by the fact that aging brings changes such as decreased stature, accumulation of adipose tissue, reduction of lean body mass, and decreased amount of water in the body, which directly impact their body composition (19) .
In the intraoperative period, the patient was followed from the entrance into the operating room (OR) until his/her transfer to the post-anesthetic recovery room. The ear temperature was measured in the same ear canal (external ear) with a G-TECH Premium ® infrared tympanic thermometer at the following moments: patient admission to the operating room, beginning of anesthesia, beginning of the surgery, and every hour after the anesthetic induction until the moment of the patient's exit from the OR. The information for the ASA physical status classification was extracted from the anesthetic data in the medical record. It should be noted that the ELPO scale was also applied in this moment; that score 20 was considered as a cut-off point to differentiate the patients' classification. Those with a score ≤ 19 points were classified as having a lower risk for the development of perioperative PI, while patients with a score ≥ 20 were considered to present a higher risk for this event (16) . The NPUAP classifies pressure lesions in stages 1, 2, 3 and 4, unstageable pressure injury, deep tissue pressure injury, medical device related pressure injuries, and to mucous membranes related pressure injuries. PI stage 1 shows intact skin with non-blanchable erythema.
PI stage 2 is characterized by Partial-thickness skin loss with exposed dermis. The wound bed is viable, pink or red, moist, and may also present as an intact or ruptured serum-filled blister. In LPP stage 3 there is full-thickness loss of skin, in which granulation tissue and is often present and slough and/or eschar may be visible. The stage 4 pressure lesion is characterized by full-thickness skin and tissue loss with exposed fascia, muscle, tendon, ligament, cartilage or bone, and there is slough and/or devitalized tissue. Unstageable PI shows full-thickness skin and tissue loss in which the extent of tissue damage within the ulcer cannot be confirmed because it is obscured by slough or eschar. Resulting from friction or shearing, deep tissue PI presents intact or non-intact skin, localized dark red, brown or purple, persistent and nonblanchable area or with separation from the epidermis revealing a dark wound bed or blood-filled blister (20) .
The data collected were analyzed using the SPSS      As for the association between sociodemographic and clinical variables and the ELPO score of the patients submitted to elective surgeries, the female sex, elderly group, and altered BMI were related with a statistically significant greater risk for the development of perioperative PI, with differences (Table 3).
It was observed that 77% (214)  Studies have demonstrated that the nutritional status indicated by albumin levels ≤ 3 g/dL and changes in BMI (low weight, overweight or obesity) may also influence the occurrence of perioperative PI (4,7) . In this study, although albumin levels were not assessed, most participants presented changes in BMI.
In the present sample, approximately 25% of the patients had altered hemoglobin levels. Low levels of hemoglobin deserve attention because they imply less transport of nutrients and oxygen to tissues, and consequently become a significant factor involved in the maintenance of skin integrity (22) .
Most of the patients in this study were classified as ASA II with respect to physical status, corroborating the results of another investigation, whose participants classified as ASA II and III presented higher risk and incidence of perioperative PI when compared to those classified as ASA I (4) .
It was found that the atrial temperature decreased One of the most significant risk factors for the occurrence of perioperative PI is the duration of the anesthetic-surgical procedure because long periods of immobilization and exposure to pressure cause anoxia, tissue necrosis and consequent skin injury (2,13) . One hour of surgery is capable of increasing the patient's risk for developing this type of injury by 1.07 (26) . Surgeries that exceed 2 hours can affect the oxygenation of compressed tissues, favoring the occurrence of PI (27) .
Another important risk factor in the intraoperative phase is the type of anesthesia. This aspect influences the degree of nervous system depression, pain receptors depression, and relaxation of muscles, so that the patient's defense mechanisms do not offer protection against pressure, leading to susceptibility to pressure injury and pain (9) . Studies have shown that the non-use of support surfaces during the intraoperative period increases the risk of perioperative PI (16,30) . However, the literature reports that support surfaces are little used in surgical patients because of the political, economic and social issues faced in the country, that also affect the health are, do not allow the availability of this resources in many public services, with a direct interference in the prevention of PI (9) .
Some of the objectives of nurses in the intraoperative period involve reduction, relief and redistribution of pressure. These are the three guiding principles to minimize the risk of perioperative PI. Nurses may implement them by using support surfaces to Rev. Latino-Am. Enfermagem 2019;27:e3117.
alleviate the pressure as much as possible, considering the specific needs of each patient (31) . It should be emphasized that sheets and blankets should not be used in the positioning of the patient because they decrease the effectiveness of the support surfaces and may actually increase the pressure (15) .
Regarding the presence of comorbidities, diabetes mellitus is considered one risk factor for the occurrence of perioperative PI because its pathophysiology includes a decrease in blood flow that causes tissue perfusion impairment and healing problems due to the difficulty to replace endothelial cells (6,10) .
A longitudinal study of patients undergoing major surgeries in northern Italy showed that diabetes mellitus as well as cardiac and vascular diseases are significant risk factors for the development of decubitus ulcers (5) .
Another study, developed in an American hospital, showed that patients with a history of diabetes mellitus are more likely to develop pressure injury than those without this comorbidity, with a 49% increased risk (26) .
The early identification of perioperative PI risk through the use of risk assessment scales such as ELPO (16) is an important step to prevent this complication, since several factors may contribute to its occurrence (13) .
Perioperative PI risk is a frequent nursing diagnosis in the Surgical Center and, depending on the surgery type, it can be observed in 100% of the patients (10) .
The present study showed that 56.5% of the patients presented a perioperative PI risk, while another study a majority (53.2%) of participants with ELPO score ≤ 19 points, that is, a lower risk for this type of injury (16) . It is emphasized that an increase of one point in in the scale indicates a 44% higher probability of developing PI (16) .
This study revealed that the variables female gender, elderly group, and altered BMI presented statistically significant results, that is, they were significant contributing factors for a greater risk of perioperative PI. Another study identified a higher perioperative PI rate among men than among women (25) .
On the other hand, studies point out that gender is not a significant independent factor for higher PI risk, but it is part of a set of factors that increase the risk of developing these injuries (32)(33) .
Perioperative complications increase with age.
The elderly are, therefore, more exposed to the risk of perioperative PI (16) . A study carried out in a private hospital in the city of São Paulo, Brazil, found that, advancing age was positively related to the occurrence of perioperative PI, with a higher incidence in patients aged 65 years or older (16; 40.0%) (6) .
In contrast to these results, other studies showed that elderly patients did not present a higher risk of developing perioperative PI when compared to adults (4,26) .
Regarding the nutritional status, a study corroborated the results of the present research in the sense that BMI was associated with greater risk for the development perioperative PI. In the said study, BMI > 30 Kg/m 2 was a predisposing factor for the occurrence of PI (p < 0.001) (4) . In turn, another study showed that PI risk was higher in cases of extreme BMI, and lower in eutrophic individuals (34) .
Researchers from a recent literature review found that overweight and low weight increased the perioperative PI risk (10) . Obesity is considered a risk factor for the occurrence of perioperative PI. This happens because more adipose mass can compress blood vessels and dependent nervous structures, reducing tissue perfusion and conducing to injuries (4) . Low weight, on the other hand, can lead to a marked exposure in the patient's bony prominences, leaving these points more susceptible to the appearance of PI (15) . It is important to understand that the incidence of these injuries remains high due to the absence of preventive measures. Moreover, non-compliance or non-observation of norms and/or clinical guidelines and protocols is the main contributory factor (9) .
Due to the variety of surgeries and the peculiarities of each patient, nurses are responsible for assessing the risks to which individuals are exposed in the preoperative phase, as well as the tools and devices available for the implementation of safe and effective actions to prevent complications (13) .
Developing a strategic plan to address risk factors throughout the perioperative period by determining the causes of injury, identifying any barrier that compromises patient safety, and investigating possible interventions Peixoto CA, Ferreira MBG, Felix MMS, Pires PS, Barichello E, Barbosa MH.
that reduce the incidence of this complication may be the key to prevent PI (35) .
A limiting factor in this study was the non-evaluation of the microclimate (heat and moisture of the skin) and the non-follow-up of patients in the postoperative period.
However, this did not compromise the reliability of the results. Another limiting factor was the design of the study; descriptive studies do not allow the establishment

Conclusion
The results of this study showed that the majority of the participants were female, white, adult, overweight, with normal hemoglobin values and classified as ASA II. Regarding intraoperative aspects, most surgeries lasted from one to two hours, and regional anesthesia and Trendelenburg position were the most adopted.