Factors Associated with Pressure Injury Among Critically Ill Patients in a Coronary Care Unit

INTRODUCTION

Pressure injuries (PIs) are defined as “localized injury to the skin and/or underlying tissue, usually over a bony prominence, as a result of pressure or pressure in combination with shear.”1,2 Pressure injuries can occur when there is a high-pressure load for a short period or when there is a low-pressure load for a long period.3 In addition, the definition of PIs has been extended to include medical device-related PIs (MDRPIs).4 In particular, MDRPIs occur at various sites; it can be difficult to detect them and to accurately assess their depth.3 Because PIs are associated with both decreased quality of life for patients and financial burden, prevention and management of these injuries are critical.5–7

To avoid the development of PIs in the ICU, providers must identify patients who are at risk of PIs and initiate prevention interventions as required.8Pressure injury incidence is an important clinical indicator for the quality control of medical centers. Every medical institution has applied its own guidelines for the prevention of PIs.9 However, PI incidence in the ICU ranges from 21% to 35%, whereas incidence is 3% to 14% in general hospital units.9 Critically ill patients admitted to the ICU are often admitted after a stay in other areas such as the ED, a general hospital unit, or the OR.9 Critically ill patients are at high risk of PIs because of their often advanced age, critical condition, state of consciousness, and treatments affecting tissue perfusion, including the extended use of medical devices (eg, ventilator, continuous renal replacement therapy [CRRT]), hypothermia therapy, or inotropes.10

BACKGROUND

Research indicates that the pattern of PIs in the ICU is very diverse. In a study investigating the onset time of PIs in internal medicine and surgical patients, respectively, Park et al11 reported that 42.2% of surgical patients sustained a PI within 0 to 3 days of admission. In contrast, internal medicine patients sustained this injury later: A total of 47.3% of these patients developed a PI between 4 and 15 days after admission. In surgical patients, PI risk increases in the early stages of hospitalization because of general anesthesia, position during surgery, and medical device use.12 However, the risk of PI among medical patients increases over time because of general weakness, poor nutrition, and decreased mobility. These conditions are worsened with prolonged hospitalization.13

Critically ill patients use a variety of medical devices and are exposed to various risk factors and vulnerable positions. Therefore, critically ill patients with cardiovascular disease require careful management to prevent PIs.14 In critically ill patients, it is often impossible to avoid PIs despite preventive nursing care because of exogenous and intrinsic factors that cannot be controlled.15 According to Cox,15 there are approximately 43 risk factors that produce PIs in critically ill patients. These risk factors can be categorized into patient characteristics (eg, comorbidities), length of stay, intrinsic factors, care factors (eg, medical device use, such as prolonged mechanical ventilation), and vasopressor agents.15 Among internal medicine patients, those with cardiovascular disease have an increased risk of PIs because of increased cell damage caused by tissue hypoperfusion, older age, and use of vasopressors.16

The purpose of this study was to determine (1) the incidence and clinical features of PIs among patients in the coronary care unit (CCU) and (2) the influence of risk factors on the stage and onset timing of these injuries.

METHODS

This retrospective study was conducted at a CCU in a tertiary hospital in South Korea; the researchers examined the medical records of patients who developed PIs after admission to the CCU. The researchers screened all patients who were admitted to the CCU between January 2018 and December 2020. The inclusion criteria were as follows: (1) new-onset PI after admission, (2) a stay in the CCU over 3 days, (3) age ≥ 18 years, and (4) cardiovascular disease. Of the 2,203 patients, 1,383 patients were excluded who presented with any of the following: (1) transfer or death within 3 days of admission, (2) aged <18 years, or (3) the presence of a PI at the time of admission. Of the 820 patients, 620 were excluded because they did not develop a PI while in the CCU. Finally, 200 patients with newly developed PIs were included in the analysis.

Using the G*Power program 3.1.9.2 (Heinrich Heine University, Dusseldorf, Germany), the number of participants required with an effect size (F) of 0.25, significance level P of .05, and a statistical power (1-β) of 0.95 was determined to be 176 for a t test, 84 for an analysis of variance, and 53 for a regression analysis.17 Therefore, this study met the minimum number of participants for statistical analysis.

PI Risk Factors

Pressure injury risk factors were categorized according to the previous work by Cox.15

Factor 1: Patient characteristics

Patient characteristics included sex, age, route of admission, diagnosis, and surgical history.

Factor 2: Length of stay

Length of stay included both length of hospital stays prior to CCU admission and length of stay in the CCU.

Factor 3: Intrinsic factors

Intrinsic factors included Glasgow Coma Scale score, duration of sedative use, APACHE II (Acute Physiology and Chronic Health Evaluation II) score, edema, body temperature, and nutrition status (ie, serum albumin, protein, hematocrit, and hemoglobin) at PI onset. Body temperature below 37.8 °C was classified as afebrile and above 37.8 °C as febrile.18 A serum albumin level above 3.5 g/dL, a serum protein level greater than 6.5 g/dL, and serum hemoglobin greater than 12 g/dL were classified as normal levels.19

Factor 4: Care factors, including medical devices

The use of the following medical devices was included in the care factors: endotracheal tube, tracheal tube, arterial catheter, central catheter, Foley catheter, oxygen tube (none; heated, humidified high-flow nasal cannula; nasal prong; simple mask), pulse oximeter, intermittent pneumatic compression (IPC), Levin tube or ventilator, CRRT, extracorporeal membrane oxygenation (ECMO), and restraints.

Factor 5: Vasopressor agents

The use of vasopressor agents and vasopressors including norepinephrine, vasopressin, dobutamine, dopamine, and epinephrine was examined.

Clinical Features of PIs

The researchers examined clinical features of PIs, including the duration between CCU admission and PI development, location of the PI (ie, face, upper extremity, lower extremity, front, back, or lateral), PI size, and PI stage.

PI stage

The researchers reviewed patients’ electronic medical records and classified PIs into stages 1 to 4, a deep tissue injury, or an unstageable injury using the PI assessment tool from the National Pressure Injury Advisory Panel.3 When evaluating the PI stage, if several levels of PI were present within the same injury, then the highest stage was recorded. In addition, the authors created a more general PI classification of either early stage (stage 1) or advanced stage (stage 2 or higher) for the purposes of analysis.

Timing of PI development

According to previous research,15 critically ill patients may be hemodynamically labile and physiologically unstable during the first week of ICU admission. Therefore, care priorities are focused on life preservation rather than PI prevention.15 In addition, Park et al11 reported that 47.3% of patients in internal medicine developed a PI between 4 and 15 days after hospitalization. Based on these results, the researchers classified PIs as either early onset (occurring within 3 days of admission to the CCU) or late onset (occurring after 3 days) for this study.

Braden Scale

The Braden Scale was used to assess PI risk. It measures PI risk with six subscales (sensory perception, activity, mobility, moisture, friction/shear, and nutrition). Lower scores indicate a greater PI risk.15,20

Ethical Considerations

This study was conducted subsequent to the approval of the Gachon University Medical Center Institutional Review Board (IRB no. GAIRB2021-029) and the approval of the nursing department. Identifiable personal information was not collected, and all data were organized by ID numbers.

Data Collection and Analysis

After obtaining IRB approval, the first author reviewed patients’ medical records to determine the timing of the first occurrence of a PI. This information was collected from electronic medical record systems using a structured case report form.

The collected data were analyzed using IBM SPSS (version 23.0; IBM Corp, Armonk, New York). The incidence of PIs in the CCU was calculated as:

The number of newly developedPIsThe number of patients admitted to theCCU*100

Pressure injury risk factors and clinical features were analyzed using frequency, percentage, mean, and SD. Differences in PI risk factors and clinical features according to the PI stage or PI onset time were compared using χ2 test or t test. Logistic regression analysis was used to explore variables that were independently related to the PI stage or onset time.

RESULTS PI Incidence and Risk Factors Among CCU Patients

In the present study, the incidence of PIs was 24.4%. The PI risk factors of the patients included in this study are presented in Table 1. Of the 200 patients, 109 were men, and 136 (68%) were older than 65 years. The most common diagnosis was myocardial infarction (n = 77 [38.5%]). Care factors including the use of various medical devices ranged in usage from 12% (ECMO, n = 24; tracheal tube, n = 24) to 93.5% (Foley catheter, n = 173). Regarding vasopressor agents, 69.0% of the patients (n = 138) were injected with a continuous infusion of vasopressors (Table 1).

Table 1 - PRESSURE INJURY RISK FACTORS AMONG CCU PATIENTS (N = 200) Variable n (%) Mean ± SD Patient characteristics Sex  Male 109 (54.5)  Female 91 (45.5) Age, y  <65 64 (32.0)  ≥65 136 (68.0) Route of admission  ED 53 (26.5)  Unit 78 (39.0)  ICU 69 (34.5) Diagnosis  Myocardial infarction 77 (38.5)  Valve disease 26 (13.0)  Heart failure 64 (32.0)  Arrhythmia 6 (3.0)  Aortic aneurysm 4 (2.0)  Cardiomyopathy 19 (9.5)  Cardiogenic shock 4 (2.0) Surgery  No 117 (58.5)  Yes 83 (41.5) Length of stay  Length of hospital stay before CCU admission, d 9.07 ± 13.06  Length of stay in CCU, d 30.69 ± 46.89 Intrinsic factors  GCS 8.63 ± 4.70  Length of sedation, d 3.44 ± 5.70  APACHE II score 25.21 ± 10.70  Edema 99 (49.5)  Fever 154 (77.0)  Abnormal serum albumin, g/dL 174 (87.0) 2.99 ± 2.07  Abnormal serum protein, g/dL 184 (92.0) 5.19 ± 1.02  Hematocrit, % 29.71 ± 5.08  Abnormal hemoglobin, g/dL 172 (86.0) 10.02 ± 2.59 Care factors, including medical devices  Endotracheal tube 110 (55.0)  Tracheal tube 24 (12.0)  Arterial catheter 156 (79)  Central catheter 173 (86.5)  Foley catheter 187 (93.5)  Oxygen tube   No 129 (64.5)   Heated, humidified high-flow nasal cannula 36 (18.0)   Nasal prong 32 (16.0)   Simple mask 3 (1.5)  Pulse oximeter 200 (100)  IPC 98 (49.0)  Levin tube 132 (66.0)  Ventilator 127 (63.5)  CRRT 49 (24.5)  ECMO 24 (12.0)  Restraints 146 (73.0) Vasopressor agents Inotropic 138 (69.0) Norepinephrine, μg/min 7.43 ± 11.09 Vasopressin, unit/h 0.30 ± 1.06 Dobutamine, μg/kg per minute 1.92 ± 3.96 Dopamine, μg/kg per minute 0.11 ± 0.85 Epinephrine, μg/kg per minute 0.00 ± 0.02

Abbreviations: APACHE, Acute Physiology and Chronic Health Evaluation; CCU, coronary care unit; CRRT, continuous renal replacement therapy; ECMO, extracorporeal membrane oxygenation; GCS, Glasgow Coma Scale; IPC, intermittent pneumatic compression.


Clinical Features of PIs among CCU Patients

Newly developed PIs occurred an average of 7.47 days after CCU admission. The most common PI site was on the back side of the body (n = 142 [72%]). The most common stage at diagnosis was stage 2 (n = 143 [71.5%]; Table 2).

Table 2 - CLINICAL FEATURES OF PI AMONG CCU PATIENTS (N = 200) Variable n (%) or Mean ± SD Duration of PI onset from CCU admission, d 7.47 ± 9.09 PI site of occurrencea  Face 12 (6.0)  Upper extremity 5 (3.5)  Lower extremity 30 (15.0)  Front 4 (2.0)  Back 142 (71.0)  Lateral 7 (3.5) PI size when diagnosed, cm  <1 12 (6)  1 to <5 94 (47)  5 to <10 72 (36)  ≥10 22 (11.0) PI stage when diagnosed  Level 1 41 (20.5)  Level 2 143 (71.5)  Level 3 or aboveb 16 (8.0)

Abbreviations: CCU, coronary care unit; PI, pressure injury.

aPressure injury sites of occurrence: face (ear, n = 7; lip, n = 1; nose, n = 3; tongue, n = 1), upper extremity (radial, n = 2; finger, n = 1; hand, n = 1; elbow, n = 1), lower extremity (foot, n = 2; lower leg, n = 2; heel, n = 16; ankle, n = 5; thigh, n = 1; knee, n = 1; toe, n = 3), front (femoral, n = 4), back (occipital, n = 6; coccyx, n = 94; hip, n = 27; vertebral, n = 4; sacrum, n = 10; scapula, n = 1), lateral (iliac, n = 6; flank, n = 1).

bLevel 3 or above: stage 3, n = 8; unstageable, n = 0; deep tissue injury, n = 8.


Differences in PI Risk Factors and Clinical Features by PI Stage

Patients were divided into two PI categories—early stage (stage 1, n = 41) and advanced stage (stage 2 or higher, n = 159)—to investigate patient characteristics by PI severity (Table 3).

Table 3 - DIFFERENCES IN PI RISK FACTORS AND CLINICAL FEATURES BY PI STAGE (N = 200) Variable Early Stage (n = 41)
n (%) or Mean ± SD Advanced Stage (n = 159)
n (%) or Mean ± SD χ 2 or t P Patient characteristics Sex  Male 21 (51.2) 88 (55.3) 0.224 .726 Age  ≥65 y 28 (68.3) 108 (67.9) 0.002 1.000 Route of admission  ED 10 (24.4) 43 (27.0) 1.209 .546  Unit 19 (46.3) 59 (37.1)  ICU 12 (29.3) 57 (35.8) Had surgery 21 (51.2) 62 (39.0) 2.007 .161 Length of stay Length of hospital stay before CCU admission, d 13.07 ± 16.32 8.04 ± 11.92 1.852 .070 Length of stay in CCU, d 17.90 ± 15.17 33.99 ± 51.55 -1.973 .050 Intrinsic factors GCS 9.66 ± 4.84 8.36 ± 4.64 1.578 .116 Length of sedation, d 2.12 ± 3.50 3.77 ± 6.10 -2.261 .026 APACHE II score 24.54 ± 9.63 25.38 ± 10.99 -0.448 .655 Edema 17 (41.5) 82 (51.6) 1.332 .294 Fever 7 (17.1) 39 (24.5) 1.023 .406 Abnormal serum albumin, g/dL 32 (78.0) 142 (89.3) 3.654 .069 Abnormal serum protein, g/dL 35 (85.4) 149 (93.7) 3.084 .103 Hematocrit, % 31.27 ± 5.53 29.31 ± 4.89 2.224 .027 Abnormal hemoglobin, g/dL 28 (68.3) 144 (90.6) 13.431 .001 Care factors, including medical devices Endotracheal tube 22 (53.7) 88 (55.3) 0.037 .862 Tracheal tube 4 (9.8) 20 (12.6) 0.246 .790 Arterial catheter 34 (82.9) 122 (76.7) 0.730 .526 Central catheter 37 (90.2) 136 (85.5) 0.619 .609 Foley catheter 39 (95.1) 148 (93.1) 0.223 1.000 Oxygen tube 17 (41.5) 54 (34.0) 0.801 .368 IPC 17 (41.5) 81 (50.9) 1.172 .298 Levin tube 22 (53.7) 110 (69.2) 3.500 .067 Ventilator 23 (56.1) 104 (65.4) 1.219 .280 CRRT or ECMO 6 (14.6) 52 (32.7) 5.169 .032 Restraints 29 (70.7) 117 (73.6) 0.135 .698 Vasopressor agents Norepinephrine, μg/min 5.84 ± 9.45 7.84 ± 11.47 -1.027 .306 Vasopressin, unit/h 0.18 ± 0.86 0.33 ± 1.11 -0.787 .432 Dobutaminey, μg/kg per minute 1.20 ± 2.34 2.11 ± 4.26 -1.317 .189 Dopamine, μg/kg per minute 0.10 ± 0.63 0.11 ± 0.90 -0.063 .950 Epinephrine, μg/kg per minute 0.002 ± 0.011 0.004 ± 0.024 -0.368 .713 Duration of CI onset from CCU admission, d 7.02 ± 10.23 7.58 ± 8.80 -0.351 .726 PI site of occurrence  Face 3 (25.0) 9 (75.0) 5.008 .415  Upper extremity 0 (0.0) 5 (100.0)  Lower extremity 9 (30.0) 21 (70.0)  Front 1 (25.0) 3 (75.0)  Back 28 (19.7) 114 (80.3)  Lateral 0 (0.0) 7 (100.0) PI size when diagnosed, cm  <1 1 (2.4) 11 (6.9) 5.171 .160  1 to <5 20 (48.8) 74 (46.5)  5 to <10 12 (29.3) 60 (37.7)  ≥10 8 (19.5) 14 (8.8)

Abbreviations: APACHE, Acute Physiology and Chronic Health Evaluation; CCU, coronary care unit; CRRT, continuous renal replacement therapy; ECMO, extracorporeal membrane oxygenation; GCS, Glasgow Coma Scale; IPC, intermittent pneumatic compression; PI, pressure injury.

The length of stay in the CCU and the length of sedation were both significantly longer for patients in the advanced stage category compared with those in the early stage (P = .050, P = .026, respectively). In addition, hematocrit levels were significantly lower in patients in the advanced stage compared with those in the early stage (P = .027). A significantly greater number of patients in the advanced stage group had abnormal hemoglobin (P = .001) and used CRRT or ECMO (P = .032; Table 3).

In both the early and advanced stages, PIs occurred most often on the back (occipital, coccyx, hip, vertebral, sacrum, and scapula), followed by the lower extremities (foot, lower leg, heel, ankle, thigh, knee, and toe). However, the upper extremity (radial, finger, hand, elbow) and lateral (iliac, flank) PIs that developed were all advanced at the time of first detection (Table 3).

Differences in PI Risk Factors and Clinical Features by PI Onset Time

The researchers divided patients into two PI onset categories—early onset (within 3 days after admission to the CCU) and late onset (more than 4 days after admission to the CCU)—and analyzed patient characteristics accordingly (Table 4). There were 86 patients (43.0%) in the early-onset group and 114 patients (57.0%) in the late-onset group. As a result of these category groupings, length of stay in the CCU and length of sedation were both longer in patients in the late-onset group (P = .017, P ≤ .001). In comparison with the early-onset group, patients in the late-onset group were more likely have edema (P ≤ .001), lower hematocrit levels (P = .003), and abnormal hemoglobin levels (P < .001; Table 4). In addition, more patients in the late-onset group used tracheal tubes, arterial tubes, central catheters, oxygen tubes, IPC, Levin tubes, CRRT or ECMO, and restraints compared with the early-onset group (P = .007, P = .003, P = .001, P = .032, P < .001, P < .001, P = .040, and P = .002, respectively; Table 4). Norepinephrine and vasopressin use was also higher in the late-onset group compared with the early-onset group (P = .001, P = .043, respectively; Table 4).

Table 4 - DIFFERENCES IN PI RISK FACTORS AND CLINICAL FEATURES BY PI ONSET TIME (N = 200) Variable Early Onset (n = 86)
n (%) or Mean ± SD Late Onset (n = 114)
n (%) or Mean ± SD χ 2 or t P Patient characteristics Sex  Male 46 (53.5) 63 (55.3) 0.062 .886 Age  ≥65 y 60 (69.8) 76 (66.7) 0.217 .760 Route of admission  ED 20 (23.3) 33 (28.9) 3.579 .167  Unit 40 (46.5) 38 (33.3)  ICU 26 (30.2) 43 (37.7) Had surgery 37 (43.0) 46 (40.4) 0.144 .772 Length of stay  Length of hospital stay before CCU admission, d 8.21 ± 11.38 9.72 ± 14.21 −0.834 .405  Length of stay in CCU, d 22.00 ± 36.88 37.25 ± 52.42 −2.413 .017 Intrinsic factors GCS 9.22 ± 5.02 8.18 ± 4.41 1.522 .130 Length of sedation, d 1.53 ± 2.76 4.87 ± 6.83 −4.268 <.001 APACHE II score 24.56 ± 9.92 25.69 ± 11.28 −0.741 .459 Edema 27 (31.4) 72 (63.2) 19.784 <.001 Fever 15 (17.4) 31 (27.2) 2.632 .127 Abnormal serum albumin, g/dL 71 (82.6) 103 (90.4) 2.632 .137

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