Effect of Soft Silicone Foam Dressings on Intraoperatively Acquired Pressure Injuries: A Randomized Study in Patients Undergoing Spinal Surgery

Pressure injuries are defined as local damage to the skin and underlying tissues caused by pressure and shear forces, mainly over bony prominences; however, they may also be related to medical devices or other objects.¹ Pressure injuries can be painful.² In addition, an increased risk of complications and mortality can often arise.³ Treatment is expensive and can negatively affect the patient’s quality of life.⁴

Pressure injuries are caused by interactions between endogenous and exogenous factors. Endogenous factors are those that regulate patient resistance. In contrast, exogenous factors include friction and shear force.¹ Although pressure injuries can occur in all patient groups, lengthy surgical procedures increase the risk of pressure injuries,⁵ and prone positioning is associated with a higher risk of pressure injuries than other intraoperative positions.⁶

In the supine position, the angle between the spine and the horizontal plane becomes a straight line (180 degrees), allowing friction and pressure to be evenly distributed throughout the body. The force experienced in the prone position using the Wilson frame is different from the force acting parallel to the body surface in the supine position because the load is transmitted from various directions, such as the forehead, chin, shoulder, chest, pelvis, knee, and ankle. In the prone position, more load, pressure, and friction are transmitted to the soft tissue.^7,8 Moreover, by increasing the pressure on the anterior structure, the abdominal and respiratory pressures increase, thus increasing the risk of complications related to these hemodynamic changes.⁹ Spine surgery performed in the prone position is complex, extensive, and time-consuming.¹⁰ It is known that time-consuming surgeries, in particular, can increase the risk of damaged tissues.¹¹ 

The International Clinical Practice Guideline published jointly by the European Pressure Ulcer Advisory Panel, National Pressure Injury Advisory Panel, and Pan Pacific Pressure Injury Alliance recommends that individuals at risk of pressure injuries have prophylactic dressings applied.¹ A preclinical study has shown that, among the formulations used as prophylactic dressings, soft silicone foam dressings provide local cushioning, relieve shear loads in the subcutaneous tissue through shear absorption in the dressing, provide secure adhesion, and reduce friction on the outer surface of the dressing.⁷ A bench test evaluating shear and friction forces, performance of the dressing, characteristics of the dressing, and physical involvement of ulcers for 9 commercially available dressing materials indicated that the Mepilex (Mölnlycke, Gothenburg, Sweden) formulation could relieve shear force and reduce friction.⁹ The results of a controlled study involving 366 patients admitted to an intensive care unit showed a significant reduction in the risk of sacral area pressure injuries among 184 participants randomized to standard interventions and a 5-layer foam dressing compared with standard interventions alone (hazard ratio, 0.12; 95% confidence interval, 0.02-0.98; P = .048).¹⁰ 

An analysis of cohort data from 150 patients who received multi-layer soft silicone foam dressing applications on the heels in the emergency department prior to admission to an intensive care unit showed a low incidence of pressure injuries.¹¹ In a pre-/post-intervention study involving 81 patients undergoing vascular surgery, the odds ratio of sacral pressure injuries was significantly different in the post-intervention, 5-layer foam dressing group (odds ratio, 0.04; 95% confidence interval, 0.00-40; P = .006).¹² Computer modeling and simulations suggest that preventive dressings can reduce shear forces and friction, thereby lowering the tissue load and preventing pressure injuries.¹³ However, the effectiveness of these dressings in the prevention of intraoperatively acquired pressure injuries (IAPIs) remains largely unknown.¹⁴ 

The current study aimed to examine how use of a soft silicone foam dressing affects the development of pressure injuries in patients undergoing spinal surgery to obtain baseline data supporting evidence-based nursing care.

Hypothesis. This study hypothesized the following: the incidence of pressure injuries in the chest and iliac crest areas will be lower immediately after, as well as 30 minutes and 1 week following, spinal cord surgery when prophylactic dressings are applied compared with chest and iliac crest areas that are not covered with a prophylactic dressing.

The authors used a prospective self-controlled study design to investigate the effect of prophylactic dressing on the development of pressure injuries in patients undergoing spinal surgery.

Participants. Sixty-four (64) patients admitted to the neurosurgical clinic of K Tertiary General Hospital in Seoul, South Korea, for surgery of the lumbar or thoracic vertebrae in the prone position between February 12 and September 1, 2018, were recruited for this study (Figure 1). The detailed criteria for participant selection were patients who 1) were age 19 years or older and scheduled for spinal surgery in the prone position on the Wilson frame who agreed to participate in this study, 2) expected to undergo surgery lasting 2.5 hours or longer, 3) had no chest or iliac crest wound when admitted to the hospital, and 4) expected to undergo thoracic or lumbar vertebrae surgery but not cervical vertebrae surgery.

The exclusion criteria were as follows: 1) not agreeing to participate in the study or being younger than 19 years, 2) undergoing cervical spine surgery in the supine position, 3) having an estimated surgery time less than 2.5 hours, and 4) having wounds on the chest or iliac crest. The selection criterion for operative time was determined as 2.5 hours based on the findings of a previous study,¹⁵ which showed that the likelihood of pressure injury doubles if surgery lasts longer than 2.5 hours. 

A significance level of α = .05 and power of .80 were used in G*Power 3.1 (https://gpower.hhu.de) to calculate the proper sample size for 2-group proportion testing (chi-square test). The minimum sample size for this study was determined to be 93.

Instruments and assessment. To assess the degree of postoperative skin damage caused by pressure injury, this study adopted the international guideline on ulcer classification from the European Pressure Ulcer Advisory Panel, National Pressure Injury Advisory Panel, and Pan Pacific Pressure Injury Alliance.¹ The finger-press method was used to distinguish stage 1 pressure injuries from blanchable erythema and non-blanchable erythema. This was performed by gently pressing the reddened area for 10 seconds and observing whether the pressed site turned white. A healthy reaction was recorded if the site turned white immediately; a stage 1 pressure injury was recorded if the site remained red.

Procedures. The skin condition of patients admitted to the operating room was evaluated by an experienced researcher (a neurosurgeon). Then, dice were rolled to determine where to place the dressing. If an odd number appeared, then a preventive dressing (Mepilex border, 15 × 20 cm) was attached to the right chest and right iliac crest area. If an even number appeared, then the preventive dressing was attached to the left chest and iliac crest area (Figure 2). The conventional method was employed at the control site, using a disinfectant cloth to cover the Wilson frame and the memory foam provided with it to prevent contamination by direct contact between the patient’s skin and the Wilson frame as well as to prevent direct pressure on the skin (Figure 3).

Immediately after surgery, the first skin condition evaluation was performed for the chest and iliac crest area. The second skin condition evaluation was conducted 30 minutes after surgery. Participants with a pressure injury that was found in the second skin evaluation underwent a third skin evaluation on all chest and iliac crest areas after 1 week.

Data collection. A total of 64 patients were enrolled. Fourteen (14) patients were excluded, leaving 50 for analysis (Figure 1). 

Blood tests (white blood cell count, hematocrit, platelets, hemoglobin levels, C-reactive protein level, erythrocyte sedimentation rate, creatinine, blood urea nitrogen, glutamic oxaloacetic transaminase [aspartate aminotransferase], glutamic-pyruvic transaminase [alanine aminotransferase], prothrombin time [international normalized ratio], activated partial thromboplastin time, albumin, glucose, hemoglobin A1c, total cholesterol, and low-density lipoprotein) were performed before hospitalization. Systolic blood pressure, diastolic blood pressure, age, height, weight, body mass index, hypertension, heart disease, diabetes mellitus, and Braden scale scores were based on hospitalization records measured by the attending nurse at the time of admission to the hospital.

Surgery-related variables were set based on risk factors that might affect pressure injuries that might occur in the operating room, and were recorded using anesthesia recording paper after surgery.¹⁵ 

Patient age was grouped as follows: 44 years and younger, 45 to 64 years, and 65 years and older. Body mass index was grouped as less than 18.5 kg/m², 18.5 to 22.9 kg/m², 23 to 24.9 kg/m², and ≥ 25 kg/m². The Braden scale scores were grouped as 6 to 12 points, 13 to 14 points, 15 to 18 points, and 19 to 23 points. Additionally, the operative time and anesthesia times were grouped as 150 to 239 minutes, 240 to 400 minutes, and ≥ 401 minutes. All groups were used to evaluate pressure injury risk. 

Data analysis. Data were analyzed using SPSS/WIN 23.0 (IBM SPSS, Inc., Chicago, IL). The participants’ general, disease-related, and surgery-related characteristics were examined using frequency analyses and descriptive statistics. Categorical variables were analyzed according to frequency and percentage, whereas continuous variables were analyzed according to mean and standard deviation. Continuous variables included disease-related characteristics such as blood test results, mean blood pressure during surgery, and heart rate. Finally, a chi-square test or Fisher’s exact test was performed to evaluate the frequency of pressure injuries in the chest and iliac region after surgery. A pressure injury was determined to be present when the ulcer was stage 1 or higher.

Ethical considerations. To protect research participants, an approval from Kangbuk Samsung Hospital’s Institutional Ethics Review Board was obtained before this study (IRB 2018-01-026). Only participants who had submitted written informed consent were included in the study, and they were told that they may withdraw themselves whenever they wished. 

Demographic and health characteristics (Table 1). Of the 50 patients who completed the study, 26 were men (52.0%) and the average age was 62.54 years (SD ± 13.83). Five patients (10.0%) were 44 years or younger, 18 (36.0%) were 45 to 64 years, and 27 (54.0%) were 65 years and older. The average height was 159.32 cm (SD ± 10.22). The average weight was 61.50 kg (SD ± 10.77). The average body mass index was 24.32 kg/m² (SD ± 4.23); 4 patients (8.0%) were underweight, 16 (32.0%) were of healthy weight, 12 (24.0%) were overweight, and 18 (36.0%) were obese. 

Thirty-four (34) patients (32.0%) had hypertension, and 16 (68.0%) did not have hypertension; 8 patients (16.0%) had diabetes, and 42 (84.0%) did not. Two (2) patients (4.0%) had heart disease, and 48 (96.0%) did not. The average Braden scale score was 21.70 (SD ± 2.48) prior to surgery. There were no high-risk patients (0%), 1 (2.0%) medium-risk patient, 6 (12.0%) mild-risk patients, and 43 (86.0%) low-risk patients.

Blood test results showed the following mean values: white blood cell count, 7.76 × 103/mm³ (SD ± 3.09); hematocrit level, 38.75% (SD ± 5.26); platelet count, 272.62 × 103/mm³ (SD ± 84.58); hemoglobin level, 13.06 g/dL (SD ± 1.89); C-reactive protein level, 0.33 mg/dL (SD ± 0.61); erythrocyte sedimentation rate, 27.64 mg/hr (SD ±23.97); creatinine level, 0.77 mg/dL (SD ± 0.21); blood urea nitrogen level, 16.33 mg/dL (SD ± 6.02); glutamic oxaloacetic transaminase (aspartate aminotransferase) level, 27.06 IU/L (SD ± 17.83); glutamic-pyruvic transaminase (alanine aminotransferase) level, 26.10 IU/L (SD ± 22.15); prothrombin time (international normalized ratio) level, 1.08 (SD ± 0.10); activated partial thromboplastin time level, 29.82 sec (SD ± 4); albumin level, 4.37 g/dL (SD ± 0.51); glucose level, 111.98 mg/dL (SD ± 36.11); hemoglobin A1c level, 5.88% (SD ± 0.80); total cholesterol level, 161.98 mg/dL (SD, ± 34.14); low-density lipoprotein level, 107.32 mg/dL (SD ± 33.09). Preoperative blood pressure means were 125.84 mm Hg (SD ± 14.34) (systolic) and 72.44 mm Hg (SD ± 9.53) (diastolic).

Surgery-related characteristics (Table 2). Patients underwent surgery that lasted an average of 218.40 minutes (SD ± 137); 35 (70.0%) underwent surgery that lasted 150 to 239 minutes, 12 (24.0%) underwent surgery that lasted 240 to 400 minutes, and 3 (6.0%) underwent surgery that lasted ≥ 401 minutes. Patients were under anesthesia for an average of 254.80 minutes (SD ± 101.89); 29 (58.0%) received anesthesia for 150 to 239 minutes, 17 (34.0%) for 240 to 400 minutes, and 4 (8.0%) for ≥ 401 minutes. 

During surgery, the mean systolic blood pressure was 110.38 ± 12.12 mm Hg, mean diastolic blood pressure was 66.82 ± 11.25 mm Hg, mean arterial blood pressure was 81.30 ± 10.13 mm Hg, mean heart rate was 75.80 ± 10.81 beats/min, mean body temperature was 35.92 ± 0.69°C, and average blood loss was 600.20 ± 771.45 mL (Table 2).

Outcomes. Immediately following surgery, a total of 16 pressure injuries were observed in the chest area, 2 in areas that had been covered with a dressing, and 14 that were not covered with a dressing (χ² = 10.71; P = .002). The pressure injuries that occurred in the chest area, where the preventive dressing was not applied, were 9 in the first stage and 5 in the second stage. Similarly, in the iliac crest area, 10 pressure injuries were noted, none in the dressing covered and 10 in the control area (P = 0.001). Of those, 9 were stage 1 and 1 was stage 2. (Table 3). 

Thirty (30) minutes after surgery, the total number of pressure injury areas was lower in both the chest and iliac crest area. In the dressing-covered chest areas, 3 stage 1 pressure injuries were noted. In the control areas, 10 sites (20%) had a visible pressure injury. Of those, 5 were stage 1 and 5 were stage 2. The difference in incidence between dressing and control areas was not statistically significant. (χ² = 4.33; P = .071) (Table 4).

Thirty (30) minutes after surgery no pressure injuries were noted on the iliac crest areas that had been covered with a dressing compared to 7 (14%) in the control area (χ² = 7.53; P = .012) (Table 4). Six  (6) were stage 1, and 1 was classified as stage 2. 

Thirteen (13) patients with pressure injuries found on the second examination had both the chest and iliac crest reevaluated 1 week after surgery (Table 5). In the chest area, no pressure injuries remained in the areas that had been covered by the dressing, but 8 (61.5%) of the original 10 areas in the control group were assessed as pressure injuries (χ2 = 11.56; P = .002). Of those, 7 were stage 1, and 1 was a stage 3. In the iliac crest control area, the number of pressure injuries was 4 (30.8%) compared with 7 at 30 minutes after surgery (χ² = 4.73; P = .096). All were classified as stage 1. The difference in the incidence of iliac crest pressure injury areas between dressed and non-dressed areas was not statistically significant.

This experimental study was performed to examine how prophylactic dressings affect pressure injury development in patients undergoing spinal surgery. It was found that the incidence of pressure injuries was significantly lower in the areas covered with a dressing compared with the control areas in the chest and iliac crest area immediately following surgery, in the iliac crest area 30 minutes after surgery, and in the chest area 1 week after surgery. This was consistent with the results of a bench test by Call et al,⁹ who evaluated the shear force and friction force of the preventive dressing, the performance of the dressing, and the physical invasion of ulcers; their results indicated that preventive dressings can distribute the pressure and friction that patients sustain during surgery and reduce the resultant pressure injuries by avoiding direct contact with bone protrusions. In addition, the results of a prospective cohort analysis of the effect of prophylactic dressing in 150 patients in the intensive care unit,¹¹ a study analyzing the effect of prophylactic dressing in 81 patients undergoing vascular surgery,¹² and a computer simulation modeling of preventive dressing revealed low incidences of pressure damage in the area to which the prophylactic dressing was applied, consistent with 1 study that measured the heel pressure and shear force in patients with diabetes.¹³

The number of pressure injuries occurring in the iliac crest area was lower than that in the chest area because, in the prone position, when a surgical frame is used for spinal surgery, the chest area sustains relatively more pressure than the iliac crest. This is consistent with findings of Yoshimura et al,¹⁶ who, in a preliminary investigation, reported that the chest pressure was higher than that of the iliac crest as a result of measuring the interface pressure mapping between the chest and the iliac crest in the prone position using the Relton-Hall frame.

In the present study, pressure injuries were observed not only immediately after surgery, but also 30 minutes and 1 week after surgery. At the second evaluation, 30 minutes after surgery, the incidence of pressure injury in the chest area increased from 2 to 3 cases. However, a study by Fu Shaw et al¹⁵ found that in 297 patients, there was pressure damage not only immediately after surgery but also 30 minutes after surgery. Pressure injury can also be found during recovery after surgery. This suggests that assessments of a patient’s skin condition and nursing interventions should be performed at the appropriate times. Continuous observations can confirm the appearance of pressure injuries and help to determine the risk of occurrence. Furthermore, the current study results observed 1 week after surgery show that most, but not all, IAPIs will resolve. After 1 week, 1 pressure injury had evolved to stage 3. 

In the current study, there were 2 cases (2%) of pressure injuries after surgery in the area where the prophylactic dressing had been applied, and the incidence of pressure injuries was lower than that of 24 cases (24%) in the area where the prophylactic dressing had not been applied. At 30 minutes after surgery, there were 3 pressure injuries (3%) in the area to which the prophylactic dressing had been applied, and the incidence of pressure injuries was lower than that of 17 cases (17%) observed in the area without the prophylactic dressing. Finally, 13 patients with pressure ulcers observed at the second observation underwent a third observation 1 week after surgery. No pressure injuries occurred in the area where the prophylactic dressing was applied. However, 12 pressure injuries (46%) were observed in the area where the prophylactic dressing was not applied. Although not always statistically significant at all measurement intervals, the authors found that prophylactic dressings can reduce the incidence of pressure injury in patients undergoing surgery in a prone postion and reduce the persistence of pressure injuries.

This study had several limitations. This study was conducted at a single university hospital. Further studies should examine the effects of prophylactic dressings on a wider group of patients for an extended period. In addition, this study involved only patients undergoing spinal surgery. Therefore, further studies should investigate the results of prophylactic dressings for other surgeries involving a high risk of pressure injuries and further explore intraoperative risk factors. The authors investigated the occurrence of pressure injuries immediately after surgery, 30 minutes after surgery, and 1 week after surgery; nevertheless, there was a limitation in that the authors could not observe changes in pressure injuries every day over time.

This study is especially significant because of its self-controlled design that minimized exogenous variables. In countries where there are no clear insurance standards for prophylactic dressings, including Korea, additional studies should be conducted to determine whether insurance fees can be established for the use of prophylactic dressings.

The current findings suggest that compared with the use of standard memory foam dressing, the use of soft silicone foam prophylactic dressings for patients undergoing spinal surgery results in a lower incidence of pressure injuries immediately after surgery in both the chest and iliac crest areas. The authors believe that these findings are sufficiently significant to support immediate incorporation of soft silicone foam prophylactic dressings in nursing care plans for these patients. Surgically induced pressure injuries are iatrogenic injuries that can be reduced with preventive measures.

Mr. Yang is a doctoral student, College of Nursing Science, Kyung Hee University, Seoul, Republic of Korea. Dr. Shin is an associate professor, College of Nursing Science, East-West Nursing Research Institute, Kyung Hee University, Seoul, Repulic of Korea. Send all correspondence to: Sung Hee Shin, College of Nursing Science, Kyung Hee University, 02453 24, Kyungheedae-ro, Dongdaemun-gu, Seoul, Republic of Korea; tel: 82-2-961-0917; fax: 82-2-961-9398; email: sunghshin@khu.ac.kr.

None disclosed.