A pressure ulcer/injury (PU/I) can occur during prolonged surgical procedures in the operating room (OR).1 Such injury commonly occurs in anatomic areas in which soft tissues are subject to sustained mechanical loading (ie, pressure) between the bony anatomy (eg, sacrum, heel, ischium) and an external structure (eg, OR mattress, wheelchair).2 This loading or pressure occurs during prolonged surgical procedures in which the patient is immobilized for longer than 1 to 2 hours and in patients with low perfusion pressure.1 This persistent pressure obstructs capillary blood flow to the area under pressure and may affect the deep or superficial tissues.2 Recent publications suggest that pressure redistribution surfaces applied on top of the OR table mattress may decrease the risk of PU/I.3-5 Few studies have been conducted to determine which surfaces and what patient positioning may achieve sufficient pressure redistribution to decrease intraoperative PU/I.
A 2015 article by some of the authors of this current study focused on pressure mapping OR surfaces using the science of measured peak pressures and surface area to promote the use of an air-filled seat cushion placed under the sacrum during supine procedures.5 Use of static, air-filled seat cushions for supine positioning in the OR resulted in a 65% reduction in sacral PU/Is that originate in the OR over a 5-year period. In that earlier study the static, air-filled seat cushion was not tested for patients in the supine with bent knees position or the supine in lithotomy position, and the use of this cushion in either of those patient positions was not previously promoted.
Statement of purpose
The purpose of this study was to measure the pressure redistribution properties of the standard OR mattress as compared with use of the standard OR mattress with the static, air-filled seat cushion placed on top of it (ie, placed under the buttocks), with patients in the supine with bent knees position or the supine in lithotomy position.
Research question and significance to perioperative nursing
The surgical team, including nursing staff, is responsible for assessing, planning, implementing, communicating, and documenting the collaboration of care in the perioperative area (before, during, and after surgery). Patient positioning is an important part of this team effort and is done under the direction or delegation of the attending surgeon.6,7 The surgical team must have a working knowledge of the “how” and “why” of positioning equipment, the necessary safety measures, and the integration of any equipment with the surgeon’s practice preference. Patient positioning is influenced by the clinical location of the surgical site, optimal site access, surgeon experience, collateral injury, and patient safety.8
Literature review
A literature review for studies focusing on the OR, lithotomy positioning, and pressure mapping found few publications that focus specfically on preventing PU/I. Many studies focus on prevention of other safety factors (eg, preventing nerve damage) or on intraoperative maintenance of skin integrity in general. The authors found few studies on lithotomy positioning and prevention of pressure injuries to the sacral area.
Universal concern exists regarding maintaining skin integrity intraoperatively.9,10 Studies have shown an increased likelihood of preserving skin integrity by reducing interface pressure and using pressure redistribution devices appropriate to the specific positioning of the patient.11 Additionally, the use of silicone dressings has been found to reduce the risk of intraoperatively acquired PU/I by protecting skin from shearing force, friction, and moisture.9,10 It has been noted, however, that although surgical positions are standardized, each patient is unique. That is, each patient has a specific health history and body composition that makes them more or less prone to skin injury; thus, individualized interventions are necessary to address pressure redistribution, avoid shear and friction, and manage moisture.12
In a study published in 2017, Mizuno and Takahashi13 measured pressure to the sacral area in healthy volunteers (N = 21) in the lithotomy position. They investigated the relationship between external pressure (EP) in the sacral region and the physical characteristics of sex, height, weight, and body mass index (BMI). Pressure was measured using a pressure mapping system, a device used to sense EP. Four different pressure measurements were obtained for each subject: box pressure, peak box pressure, contact pressure, and peak contact pressure. The authors did not find a significant correlation between biological sex and BMI in the 4 types of EP measurement over the sacrum with study participants in the lithotomy position.
Kirkland-Walsh et al5 conducted pressure mapping of 50 volunteers on 4 different OR surfaces. Each participant acted as their own control: (1) on the standard foam OR mattress; (2) on the standard OR mattress with the static, air-filled seat cushion; (3) on a self-contouring gel/foam mattress; and (4) on a fluid immersion simulation mattress. Although the average interface pressure was similar for all 4 surfaces, the air-filled seat cushion on top of the standard OR mattress demonstrated the best pressure redistribution properties, with the lowest sacral peak pressure (35.8 mm Hg) and the largest surface area (250.2 in2).
Conceptual framework
Pressure mapping is based on a model derived from a classic study conducted by Kosiak14 and a conceptual model on the etiology of PU/I.2 The 1959 study evaluated the interface pressure on skin over time, and it explained how EP in a specific area could lead to vaso-occlusion, resulting in decreased tissue perfusion and possibly ischemia in deep and superficial tissues in the area under pressure.
Kosiak14 used a cutoff of 32 mm Hg as the upper limit for measuring surface interface pressure. An interface pressure of 32 mm Hg or less is considered to be a useful guideline for determining the efficacy of the redistribution properties of the surface being measured and for reducing the risk of PU/I.15,16