ADVERTISEMENT
Intraoperatively Acquired Pressure Ulcers: Are There Common Risk Factors?
Introduction
Descriptive studies1-4 related to contributory factors in pressure ulcers conducted in long-term care and acute care settings have led to the development of many well-known skin risk assessment tools (ie, Gosnell’s Assessment of Patient Potential for Pressure Ulcer, Braden Scale of Pressure Ulcer Risk Assessment, the Norton Score, Abruzzese's Modified Assessment of Decubitus Ulcer Potential Tool). Several descriptive studies5-10 examining factors associated with pressure ulcer development in the surgical population have demonstrated some consistency among variables associated with pressure ulcer formation and documented that even patients with a low assessment tool-based risk score may develop a pressure ulcer within the operative period.11-13 However, no specific skin risk assessment tool for the intraoperative patient population is available. 
Literature Review
Pressure ulcer prevalence. Pressure ulcers have been reported in most patient care environments; accurately ascertaining the prevalence of pressure ulcers in the operating room has been difficult. One descriptive study involving 1,128 patients reported intraoperatively acquired pressure ulcer prevalence to be 8.5%.12 However, the results may have included existing pressure ulcers (prevalence) as well as newly acquired ulcers (incidence). Documented incidence for intraoperatively acquired pressure ulcers is as low as 12% and as high as 66%.5,14,15 In a descriptive study involving 136 adult patients undergoing elective cardiac surgery, Papantonio6 found that 37 patients (27.2%) developed Stage I and Stage II pressure ulcers. Of the 24 patients who received general anesthesia for spinal disc herniation repair or abdominal surgery in Sanada’s7 3-month descriptive study, nine (36%) developed either a Stage I or Stage II pressure ulcer.
Cost. The cost of managing pressure ulcers in all settings ranges from $1.335 billion to $8.5 billion per year.16-18 Beckrich and Aronovitch18 calculated the cost of treating pressure ulcers using previously published data, including the 1998 Universal Healthcare Almanac19 and 1998 Hospital Statistics20 by the American Hospital Association. Using these data, the overall cost of treating hospital-acquired pressure ulcers in 1998 was determined to be between $2.2 and $3.6 billion, reflecting nearly 30% to 40% of an acute care hospital’s total expenditures. The annual cost to treat surgical patients’ pressure ulcers – nearly 42% of all hospital-acquired pressure ulcers occur in surgical patients – is between $750 million and $1.5 billion.18 The treatment of a single ulcer has been estimated to cost $14,000 to $40,000.20,21
Length of stay. Pressure ulcers also increase length of stay by an (average) additional 3.5 to 5 days.22 One hospital-based descriptive study found that pressure ulcers doubled the length of stay for patients undergoing hip surgery – an average increase of 10 days.23 Schultz et al5 reported that surgical patients with a pressure ulcer had a median hospital length of stay of 16.5 days, compared to 7 days for a surgical patient without a pressure ulcer.
Differential diagnosis. Intraoperatively acquired pressure ulcers are not always recognized in the immediate postoperative period. Failure to make a connection between the surgical procedure or operating room time and pressure ulcer development may be due to the possibility that not all nurses are familiar with the differences between “traditional” and intraoperatively acquired pressure ulcers. A “traditional” pressure ulcer is one that results from the common causes of shear, friction, and pressure. This is the type of pressure ulcer clinicians treat on a daily basis and what many professionals refer to as decubiti. An intraoperatively acquired pressure ulcer is the result of multiple factors that can be identified as causative agents and the appearance can range from mottled epidermis to hard, necrotic tissue.24
Intraoperatively acquired pressure ulcers typically start as burn-like lesions.6,12 Changes in skin integrity may appear within hours – typically, within 72 hours following surgery. The affected area becomes ecchymotic (bruised) and may blister. Necrosis occurs within 2 to 6 days; patients with vascular compromise and subsequent altered skin integrity may present with an area of skin that has a mottled irregular pattern that may resolve or result in a full-thickness wound.24 In many instances, the vascularly compromised patient might have only a diagnosis of diabetes mellitus, coronary artery disease, or peripheral arterial disease. Practitioners should be aware that vascular disease of the pelvic vascular system is not easily diagnosed unless that patient has a recognized abdominal aortic aneurysm or arterial studies for vascular disease in the lower extremities have been conducted.
Determining patient risk. Predicting the occurrence of a pressure ulcer that occurs during a surgical procedure is often difficult because many surgical patients are not generally considered at risk.2,4,11,18 The author has observed that changes in the patient’s skin often are thought to be related to events not associated with surgery, particularly if the patient is acutely ill. As such, nurses treating a patient with an intraoperatively acquired pressure ulcer may fail to consider the intraoperative event the patient has experienced, which may result in inappropriate management of the pressure ulcer.
The author’s personal observation/monitoring of the outcome of patients who developed mottled tissues during a surgical procedure has noted that placing an occlusive dressing (such as petrolatum-based gauze) on the discolored tissue, particularly in the coccyxgeal and upper buttocks, facilitated autolysis in the area. When the same patient population was placed on an appropriate specialty bed surface (eg, air-fluidized therapy) in addition to using an occlusive dressing, either the mottled tissue resolved without tissue loss or less tissue was damaged.
Positioning. Surgical positioning affects the risk and location of skin breakdown – eg, the lithotomy position affects the heels, sacrum, and elbows.22,23 Additional operative risk factors include the type of anesthesia, length of surgery, use of a heating/cooling device, extracorporeal circulation, pressure (ie, retractor internally, operating room staff externally), and negativity.6,26,27 Adding surface layers (eg, cloth, warming blanket) on top of a pressure-reducing surface negates the effect of the pressure-reduction surface and produces a higher pressure reading than would be expected – hence, negativity. Long periods of immobility pre- and postoperatively in elderly patients have been linked to pressure ulcer development in the immediate postoperative period.28 Several descriptive and experimental studies have identified length of surgical time as a significant contributing factor to pressure ulcer development6,9,12,29; however, the reported time frame of intraoperative pressure ulcer development ranges from as little as two to as many as 14 hours.
Many surgical procedures require patient positioning that involves solid objects or devices such as a “bean bag.” After decompression, these devices can increase pressure over a bony prominence, especially if the patient is even minimally repositioned. In the lateral supine position, the circulatory system may be compromised not only by a tight restraint, but also by the overall effect of the horizontal body posture and the changed effects of gravity.29
Anesthetics. Anesthetic agents used in surgery interrupt protective muscular mechanisms by creating alterations in the vascular status that affect blood pressure, tissue perfusion, response to pressure and pain, and the exchange of oxygen and carbon dioxide.26 Scott et al,35 in a prospective, randomized trial of 324 surgical patients, reported that general anesthesia increased the development of pressure ulcers as compared to patients receiving regional anesthetics. A diastolic blood pressure <60 mm Hg has been associated with the development of pressure ulcers in surgical patients.9,11,13 Also, the number of hypotensive events that occur during surgery has been shown to be a factor in the development of a pressure ulcer in the postoperative period.30 Medication given to reverse hypotension causes further injury secondary to increasing oxygenation, resulting in an over-production of toxic free-radicals, particularly in the elderly.31 Hypnotics and sedatives used for their anesthetic effect also can decrease blood pressure, thereby causing peripheral hypoperfusion.31
Body temperature. The body’s heat metabolism increases during surgery secondary to the cooling effect of both anesthesia and the cool operating room environment. The body experiences a 10% increase in tissue metabolism with each 1˚ C rise in skin temperature32; this phenomenon results in an increased need for cellular oxygen and nutrients and an increased byproduct removal rate33 and is magnified by the use of air or water warming systems under the patient. Physiologically, the bodies of older patients have a slower response to blood flow increases to the skin following an increase of temperature to the skin, which may lead to the development of pressure ulcers.34 Experimental23,31 and descriptive25 studies have reported an increase in postoperative pressure ulcers when a warming blanket is placed beneath patients during surgical procedures. This is consistent with the work of Kokate,36 who demonstrated that tissue damage increased significantly as skin temperature increased, even when pressure and time remained constant.
Blood flow. Sanada et al7 conducted a descriptive study of 24 patients to determine the correlation between blood flow and pressure ulcer development during surgery. They found tissue damage severity increased with decreased blood flow – specifically, a 50% decrease in skin blood flow from preoperative levels during the first hour was observed in patients who subsequently developed pressure ulcers.
Tissue damage secondary to unmet cellular demands (eg, need for oxygen and nutrients) has been reported in numerous operating room quality assurance studies.6,8,11,25,33,37 Common variables among patients were vascular compromise; vascular surgery; supine positioning on the operating room table; low pressure ulcer risk using a skin risk assessment tool; >50 years of age; medical diagnosis of hypertension, diabetes, or congestive pulmonary disease; and transfer from another facility.6,27 A secondary analysis of 117 patients from Stotts’s8 original study of pressure ulcer development in surgical patients found the following common denominators or risk factors in patients who developed intraoperative pressure ulcers: cardiovascular surgeries, neurosurgeries, lymphocyte count of 19% (normal range is 19% to 40%), and an estimated mean blood loss of 313 to 892 cc. A descriptive study by Kemp9 demonstrated that low serum albumin levels and a greater number of hypotensive episodes during surgery contributed to pressure ulcer development.
Study Purpose
Facility-based and nationwide pressure ulcer prevalence and incidence data have been collected for all patient types and healthcare facilities10,38-41 but studies do not separate data related to the surgical population and when the pressure ulcer was first noticed. A pressure ulcer on a surgical patient noted within 72 hours of the operative procedure is an indicator that the ulcer most likely occurred during the surgical procedure.6 Given this knowledge, it can be extrapolated that intraoperatively acquired pressure ulcers account for a significant number of nosocomial pressure ulcers within acute care facilities.
The primary purpose of this prospective, descriptive survey was to determine specific risk factors associated with the causation of pressure ulcers that appear immediately following a surgical procedure. The second intent of this study was to determine the current rate of intraoperatively acquired pressure ulcers following impatient surgical procedures.
Methods
Participants. Potential participants were identified using the Wound, Ostomy, and Continence Nurses Society (WOCN) 2002 directory; WOCN members working at acute care facilities throughout the US were sent introductory letters, requesting their assistance with data collection and explaining that participant anonymity would be maintained. Packets containing an appropriate number of data collection sheets and instructions for the 1-day study were sent to the Certified Wound Ostomy and Continence Nurse (CWOCN) of each identified acute care facility. Data were collected between May 2003 and August 2003. Of the 975 packets containing data collection sheets mailed, 288 patient surveys from 37 facilities were returned for a return rate of 3.89%; 281 were usable.
Procedures. Investigational Review Board approval for this study was obtained from Florida State University where the author was employed at the time of this study. Returning a completed packet signified that the WOC nurse and his/her facility agreed to participate in the study. All data sheets were coded to protect the confidentiality of patient participants. Only patients >18 years of age and scheduled for an inpatient surgical procedure of at least 3 hours were eligible to participate. Each WOC nurse and/or facility was asked to collect data on the collection sheets provided for enrolled patients once during a 1-week time period; this included data related to both preoperative and postoperative patient condition (including completion of the Modified Knoll Risk Assessment Tool). The WOC nurse indicated on the patient data sheet the postoperative day of assessment – each patient represented one assessment point.
Instruments. To understand the overall study patient population environment, data collection sheets included information about the hospital – number of active beds, operating room suites, and postoperative recovery units, as well as information regarding support surfaces used post surgery and types of products used routinely in addition to the standard operating room table pad used during surgery.
Patient data sheets included demographic information (age, sex), scheduled length and type of surgery, patient comorbidities, skin assessment, location of any skin changes, and type of support surface used at the time of assessment. The Modified Knoll Skin Risk Assessment Tool42 (see Figure 1) and the Weighted Index Comorbidity Scale44 (see Figure 2) were incorporated into the patient data sheet, which was similar to the instrument used in an earlier study conducted by the author.12 Before the survey, the tool was sent to seven CWOCNs in acute care facilities throughout the US to determine if the original tool asked questions appropriate to the study purposes; their additional questions or data points were added to address the concerns of this study.
The Modified Knoll Risk Assessment Tool is based on Abruzzese’s original tool, Assessment of Decubitus Ulcer Potential Tool, developed in 1974.4.43 This tool was selected because 1) the Modified Assessment of Decubitus Ulcer Potential Tool contains the potential contributing risk factors for alteration in skin integrity, 2) it was based on a hospitalized patient population in an acute-care setting, and 3) inter-rater reliability of the Modified Assessment of Decubitus Ulcer Potential Tool (Modified Knoll Risk Assessment Tool) for use with an acutely ill patient population is high (.8662.)42
The contributing factors included in the Modified Knoll Risk Assessment tool (see Figure 1) are scored on a 0 to 3 scale. Double weight is assigned to the variables of activity, mobility, and incontinence based on Abruzzese’s previous study findings.42 The highest attainable score is 33 – a score of 12 or higher indicates a greater risk for altered skin integrity.
The Weighted Index Comorbitity Scale was developed by Charlson, Pompei, Ales, and MacKenzie44 to ascertain comorbid conditions that might affect the risk of patient mortality. The tool, which has a 95% confidence level, was specifically developed for identifying short-term mortality in longitudinal studies (see Figure 2). Lewicki et al11 used this Scale in their study of risk factors for pressure ulcer development during cardiac surgery. They reported that patients who developed pressure ulcers had higher comorbid condition scores than patients who did not develop pressure ulcers. This tool was utilized for the extensive listing of disease processes that contribute to mortality, many of which the author has found to be related to pressure ulcer development.
Data analysis. Data were analyzed using the SPSS® (Chicago, Ill) version 11.0.1 for Windows® software. Descriptive statistics were obtained for variables and frequencies and calculated for all demographic data. Cross tabulation was used to determine the relationship between comorbidities, pressure ulcer occurrence, and type of surgery.
Results
Participating professionals and facilities. Of the original 975 mailed research packets, 37 participating facilities replied, representing a return rate of 3.79%; 21 of the 50 states were represented (see Table 1), the majority from central and eastern US. The number of patient participants per facility ranged from one to 37 (patient data forms) with 71.4% of facilities having fewer than 10 patients in the study. The median number of participating patients per facility was six (SD 6.93). 
Of the 975 WOCN members who were sent surveys, 887 (91%) never responded. Fifty-one (5.2 %) individuals/facilities replied they would not participate in the study. Reasons for non-participation included 1) no longer employed in acute care, 2) date of data collection conflicted with other work and/or personal activities, and 3) lack of lead time to prepare for data collection.
The majority (15) of the hospitals were urban with an average bed census of 281 and an average of 9,011 surgeries per year. Other facilities included rural hospitals (11), suburban hospitals (eight), and one facility identified as “other.” The number of operating rooms ranged from six in the rural to 14 in the urban hospitals; two hospitals did not provide the number of operating rooms. More than 50% of participating hospitals’ surgical procedures are performed on an outpatient basis (see Table 2).
Patient participants. The mean patient age was 61.4 years (median = 63, SD 14.9),149 (53%) were male (see Table 3), and the majority (214) were Caucasian. Of the 252 patient data sheets with complete information on comorbidities, 31 (12.3%) listed at least one comorbidity identified in the Weighted Index of Comorbidity. Frequently encountered comorbidities for all patients included diabetes mellitus (54 patients), cardiac disease (51), and peripheral vascular disease (41). Of the nine patients who developed a postoperative pressure ulcer, three (33%) had cardiac disease (see Table 4). 
Preoperatively, four (44.4%) of the patients who developed a pressure ulcer were mobile. The total score for the Modified Knoll Skin Risk Assessment Tool ranged from 3 to 16 (representing low to moderate risk for developing a pressure ulcer). Data on nutritional status (serum albumin level) was missing for four patients (see Table 5); however, if the serum albumin level had been noted for these patients it would not have changed their risk scores significantly. Three patients had risk scores >12, placing them in the moderate risk category for developing a pressure ulcer. The remaining patients had risk scores ranging from 3 to 8 and those patients missing data for nutritional status still would have remained in the low risk category even if the serum albumin level were reported to be 2.5 g/dL or less.
Nine patients (eight women and one man) developed a pressure ulcer within 7 days of the surgical procedure; six pressure ulcers (66.7%) occurred by the fourth postoperative day, an incidence of 3.5%. The majority (55.6%) of the patients were in an urban acute care facility. The median surgical duration for all patients was 255 minutes (4.25 hours) with a range from 90 minutes (1.5 hours) to 928 minutes (15.46 hours). Patients who developed a pressure ulcer had a median operating room time of 269 minutes (4.48 hours) with a range from 180 minutes (3 hours) to 387 minutes (6.45 hours) (see Table 6). The one patient on the operating room table for 90 minutes did not impact the study outcome because no pressure ulcer developed.
The majority of the patients received balanced anesthesia, defined as a combination of a short-acting barbiturate followed by an opioid analgesic, and then a skeletal muscle relaxant. At least four different agents (ie, inhalation, intravenous induction, muscle relaxant, hypnotic, opioid) were given to 80.3% of the patient sample. Of the nine patients who developed a pressure ulcer, eight received three or more anesthetic agents in at least two of the four possible categories (see Table 7).
Cardiac, general, orthopedic, and vascular surgeries were most common in this patient sample. Of the patients who developed pressure ulcers, four had orthopedic, three had cardiac, and two had general or neurological surgeries (see Table 8). Supine positioning was used in 75% of all patients and in four of the nine patients who developed pressure ulcers. For 244 patients (84.7%), the primary surface of the operating table was a 2-inch foam pad (standard operating room mattress); 34 patients (14.7%) were placed on a gel pad (see Table 8). Of the patients who developed a pressure ulcer, eight (89%) had been placed on a standard operating room mattress for the surgical procedure. Every patient was provided three or more devices not related to pressure relief (eg, warming blankets and positioning equipment). The devices used most often during a surgical procedure were foam and/or gel pads, warming devices, pillows, and blankets.
Three patients (33%) developed an ulcer in the sacral/coccyx area and two had a heel ulcer. Three of the nine patients had bilateral buttock pressure ulcers, for a total of 12 pressure ulcers. Other pressure ulcers were observed on the chin (one patient) and on the side of the face (one patient). Of the 12 ulcers, two (22.2%) were classified Stage I and six (66.7%) were Stage II; one ulcer was unstageable. Postoperatively, 55.5% of patients who developed pressure ulcers required assistance with mobility and 55.6% were ambulatory. Of the nine persons who developed pressure ulcers, one patient was incontinent, three had poor hydration, and two were comatose. Serum albumin levels were available only for five of the nine patients – one patient had a value <3.5 mg/dL (see Table 5). Of the patients with a postoperative pressure ulcer, more than 50% (five) had intact skin preoperatively.
Discussion
Patients developing a postoperative pressure ulcer had a mean age of 76.88 (30 to 98) years old and at least one comorbidity (most commonly a history of cardiac disease). These findings are similar to the results of Aronovitch’s study.12 Cardiac and orthopedic surgical procedures performed in the supine position on the operating room table were associated with pressure ulcers, confirming that intraoperative positioning is a factor in the development of pressure ulcers.12 In this study, orthopedic surgery resulted in a higher rate of pressure ulcers than previously reported and 63.3% of all study patients who received two or more anesthetic agents (categories) developed a pressure ulcer.
In the current study, the majority of the pressure ulcers were Stage II compared to Stage I in the earlier published study. The pressure ulcer location distribution was similar to previously published studies of intraoperatively acquired ulcers.6,19-21
Research conducted by Grous et al,13 Campbell,27 and Stewart and Magnano,33 as well as the current study results, suggest that the use of warming devices and standard operating room table mattresses increases the risk of pressure ulcer development. Other devices that may be associated with pressure ulcer development include pillows, blankets, gel pads, and foam pads which may have been used for positioning or in an attempt to reduce pressure during the intraoperative period.
Limitations
Limitations of the study are primarily due to the small sample size. The poor response rate to this national survey may have been related to the start date (April 2003) of the most recent changes in the HIPAA guidelines. It is hypothesized that many hospitals and/or WOC nurses were fearful of violating the patients’ privacy by participating in this voluntary survey of intraoperatively acquired pressure ulcers. The return rate was 0.59% greater than the original study reported in 1998, although the number of patient data records was only 24.9% of the original study number (N = 1,128).
In addition, because few studies have examined the effects of anesthetic agents and use of supportive or positioning devices during an operative procedure on pressure ulcer development, no data are available for comparison. Finally, the actual rate of pressure ulcer development may be higher than reported here because patients may have been discharged before the ulcer developed.
Implications for Practice and Research
Perioperative nurses face many challenges in caring for the surgical patient, including preventing pressure ulcers. Pressure ulcer research has shown that immobility, which is further sustained during surgery, increases patient risk.15,26-28 It is not possible for nurses to reposition patients frequently during a surgical procedure; therefore, the equipment used for positioning and maintaining normothermia needs to be effective without increasing the risk of compromising skin integrity. The use of additional padding and forced-air warming devices needs to be re-evaluated. Possibly, the warming device itself, not the warm air, adds additional pressure to the integrity of the skin when it is placed beneath the patient; thus, contributing to the concept of negativity. Only one (11.1 %) of the 34 patients who were placed on a gel operating room table mattress pad developed a pressure ulcer, compared to eight (88.9%) of the patients placed on a standard operating room table mattress pad. The small sample size limits the external validity of these observations but this evidence and the author’s experience suggest that a standard 2-inch operating room table mattress increases the risk of pressure ulcer development.
Demographic data revealed that >50% of hospital surgical procedures are performed on an outpatient basis and information about pressure ulcer development in these patients is not available. Additional studies to determine patient characteristics that contribute to pressure ulcer development during surgery and how these factors could be used as predictors for pressure ulcer development intraoperatively are needed. Patients with tissue oxygenation impairment (ie, cardiovascular and respiratory disease) are known to be at risk for pressure ulcer development but current skin risk assessment tools do not adequately reflect patient intraoperative risk. For example, the results of this study suggest that delivery of more than two types of anesthetic agents may increase pressure ulcer risk. Continuing study of the impact of anesthetic agents, narcotics, and hypnotics used during surgery and their possible relationship to impairment of tissue perfusion is necessary.
Conclusion
A descriptive study of 281 surgical patients showed that nine (3.5%) developed a pressure ulcer within 7 days of their operation. Factors that may increase patient risk for developing intraoperative pressure ulcers include positioning, use of positioning and thermoregulatory devices, length of surgery, type(s) of anesthesia, and comorbidities. Current risk assessment tools to predict (and subsequently prevent) intraoperatively acquired pressure ulcers are not adequate.
This study was sponsored by a research grant from Florida State University, ConvaTec® (a Bristol-Myers Squibb Company, Princeton, NJ), and the Association of PeriOperative Registered Nurses.
1. Gosnell DJ. An assessment tool to identify pressure ulcers. Nurs Res. 1973;22(1):55-59.
2. Bergstrom N, Braden BJ, Laguzza L, Holman V. The Braden scale for predicting pressure sore risk. Nurs Res. 1987;36(4):205-210.
3. Goldstone LA, Goldstone J. The Norton score: an early warning of pressure ulcers? J Adv Nurs. 1982;7(5):419-426.
4. Abruzzese RS. Early assessment and prevention of pressure ulcers. In: Lee BY (ed). Chronic Ulcers of Skin. New York: McGraw-Hill Co; 1985.
5. Schultz A, Bien M, Dumond K, Brown K, Myers A. Etiology and incidence of pressure ulcers in surgical patients. AORN J. 1999;70(3):434-447.
6. Papantonio CJ, Wallop JM, Kolodner KB. Sacral ulcers following cardiac surgery: incidence and risk factors. Adv Wound Care. 1994;7(2):24-36.
7. Sanada H, Nagakawa T, Yamamoto M, Higashidani K, Tsuru H, Sugama J. The role of skin blood flow in pressure ulcer development during surgery. Adv Wound Care. 1997;10(6):29-34.
8. Stotts NA, Paul S. Pressure ulcer development in surgical patients. Decubitus. 1988;1(3):24-30.
9. Kemp MG, Keithley JK, Smith DW, Morreale B. factors that contribute to pressure sores in surgical patients. Res Nurs Health. 1990;13(5):293-301.
10. Garber SL, Rintala DH. Pressure ulcers in veterans with spinal cord injury: a retrospective study. J Rehabil Res Devel. 2003;40(5):433-441.
11. Lewicki L, Mion L, Splane KG, Samstag D, Secic M. Patient risk factors for pressure ulcers during cardiac surgery. AORN J. 1997;65(5):933-942.
12. Aronovitch SA. Intraoperatively acquired pressure ulcer prevalence. J WOCN. 1999;26(3):130-136.
13. Grous CA, Reilly NJ, Gift AG. Skin integrity in patients undergoing prolonged operations. J WOCN. 1997;24(2):86-91.
14. Jesurum J, Joseph K, Davis JM, Suki R. Balloons, beds, and breakdown. Crit Care Nurs Clin N Am. 1996;8(4):423-440.
15. Scott SM, Mayhew PA, Harris EA. Pressure ulcer development in the operating room. AORN J. 1992;56(2):242-250.
16. Kuhn BA, Coulter SJ. Balancing the pressure ulcer cost and quality equation. Nurs Econ. 1992;10(5):353-359.
17. Miller H, Dozier J. Cost implications of pressure ulcer guidelines. Columbia, Md: Center for Health Policy Studies;1994. Contract No. 282-90070. Sponsored by the Agency for Health Care Policy and Reform.
18. Beckrich K, Aronovitch SA. Hospital-acquired pressure ulcers: a comparison of costs in medical versus surgical patients. Nurs Econ. 1999;17(5):263-271.
19. Cherner LL (ed). The Universal Healthcare Almanac. Phoenix, Ariz:Silver & Chernes, Ltd; 1998.
20. The American Hospital Association. Hospital Statistics. Chicago, Ill: Healthcare Infosource, Inc;1998.
21. Barczak C, Barnett RI, Childs EJ, Bosley LM. Fourth pressure ulcer prevalence survey. Adv Wound Care. 1997;10(4):18-26.
22. Oot-Giromini B, Bidwell FC, Heller NB, et al. Pressure ulcer prevention versus treatment, comparative product cost study. Decubitus. 1989;2(3):52-54.
23. Maklebust J, Sieggreen M. Pressure Ulcers: Guidelines for Prevention and Nursing Management. Springhouse, Pa: Springhouse Corp;1996:12-13.
24. Vermillion C. Operating room-acquired pressure ulcers. Decubitus. 1990;3(1):26-30.
25. Marchette L, Arnell I, Redick E. Skin ulcers of elderly surgical patients in critical care units. Appl Res. 1991;10(6):321-329.
26. Walsh J. Postop effects of OR positioning. RN. 1993;56(2):50-75.
27. Campbell K. Pressure points in the operating room. J Enterostomal Ther. 1989;16(3):119-124.
28. Versluysen M. How elderly patients with femoral fracture develop pressure sores in hospital. Br Med J. 1986;292(6531):1311-1313.
29. Hoshowsky VM, Schramm CA. Intraoperative pressure ulcer prevention: an analysis of bedding materials. Res Nurs & Health. 1994;17(5):333-339.
30. Nixon J, Brown J, McElvenny D, Mason S, Bond S. Prognostic factors associated with pressure sore development in the immediate post-operative period. Int J Nurs Studies. 2000;37:279-289.
31. Bliss M, Simini B. When are the seeds of pressure sores sown? BJM. 1999;319(7214):864.
32. Pope R. Pressure sore formation in the operating theater. Br J Nurs. 1999;8(4):211-217.
33. Stewart TP, Magnano SJ. Burns or pressure ulcers in surgical patients. Decubitus. 1988;February:36-40.
34. Ek AC, Lewis DH, Zetterqvist H, Svensson PG. Skin blood flow in an area at risk for pressure sore. Scand J Rehab Med. 1984;16:85-89.
35. Scott EM, Leaper DJ, Clark M, Kelly PJ. Effects of warming therapy on pressure ulcers– a randomized trial. AORN J. 2001;73(5):921-938.
36. Kokate J. Temperature-modulated pressure ulcers: a porcine model. Arch Phys Med Rehab. 1995;76(7):666-673.
37. Hoyman K, Gruber N. A case study of interdepartmental cooperation: operating room-acquired pressure ulcers. J Nurs Care Qual. 1992:Special Report:12-17.
38. Baldwin KM. Incidence and prevalence of pressure ulcers in children. Adv Skin Wound Care. 2002;15(3):121-124.
39. Coleman EA, Martau JM, Lin MK, Kramer AM. Pressure ulcer prevalence in long-term nursing home residents since implementation of the OBRA ‘87. Omnibus Budget Reconciliation Act. J Am Geriatr Soc. 2002;50(4):728-732.
40. Margolis DJ, Knauss J, Baumgarten M, Strom BL. The incidence and prevalence of pressure ulcers among elderly patients in general medical practice. Ann Epidemiol. 2002;12(5):321-325.
41. Amlung SR, Miller WL, Bosley LM. The 1999 National Pressure Ulcer Prevalence Survey: a benchmarking approach. Adv Skin Wound Care. 2001;14(6):297-301.
42. Abruzzese RS. The effectiveness of an assessment tool in specifying nursing care to prevent decubitus ulcers. In: PRN: The Adelphi Report: Project for Research in Nursing 1982, Adelphi University.
43. Aronovitch SA, Millenbach L, Kelman GB, Wing P. Investigation of the Knoll Assessment Scale in a tertiary care facility. Decubitus. 1990;5(3):70-76.
44. Charlson ME, Pompei P, Ales KL, MacKenzie CR. A new method of classifying prognostic comorbidity in longitudinal studies: development and validation. J Chron Dis. 1987;40(5):373-383.
