The Risk Factors of Postoperative Pressure Ulcer After Liver Resection With Long Surgical Duration: A Retrospective Study

Objective. The aim of this study is to investigate the risk factors of postoperative pressure ulcer (PU) development after liver resection with a long surgical duration. Materials and Methods. A retrospective analysis was performed of patients who underwent a liver resection with a surgical duration greater than 2 hours between January 2015 and December 2016 at a tertiary referral hospital in eastern China. Univariate analysis and multivariate logistic regression were used to analyze the independent risk factors for postoperative PUs. Results. Of the 128 patients included in the study, 11 (8.6%; 95% confidence interval [CI], 4.4%–14.9%) developed a stage 1 PU. Univariate analysis showed albumin on admission, diabetes mellitus complication, length of surgery, and intraoperative blood loss were all significantly different between the developed PU group (n = 11) and no PU group (n = 117; P < .05). However, multivariate logistic regression showed length of surgery (odds ratio [OR] = 1.026; 95% CI, 1.008–1.146) and intraoperative blood loss (OR = 1.014; 95% CI, 1.009–1.124) as only the independent risk factors for PU development after liver resection with a long surgical duration. Conclusions. These results showed length of surgery and intraoperative blood loss were independent risk factors for PU after liver resection with a long surgical duration. Use of PU prevention strategies are recommended for patients who undergo liver resection with massive intraoperative blood loss and long surgical duration.

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Surgery-related pressure ulcer (PU) is a common type of PU. A previous systematic review showed the incidence of surgery-related PU was 15%, with a 95% confidence interval (CI) of 14% to 16%.¹ These PUs cause significant pain and additional costs. One study² showed surgical patients who developed a PU had an extended mean length of hospital stay (28.1 days; up from 10.3 days), increased medical expenditure on antibiotics (risk ratio 2.60; 95% CI, 1.88–3.60), and about 1.83-fold risk (95% CI, 1.54–2.18) of 30-day postoperative mortality compared with a control group.Therefore, it is critical to prevent postoperative PU.

The most common types of surgery associated with PU development are cardiac, general/thoracic, orthopedic, and vascular procedures.³ However, in clinical practice, the authors also found PUs could develop in patients receiving liver resection, especially in long and complex surgeries. The authors’ previous study found length of surgery is an important risk factor for PUs in the cardiovascular surgical patient.⁴ Long surgical duration will increase tissue pressure time, allowing a PU to develop. It seems long surgical duration may be a risk factor for PUs in patients who undergo liver resection. However, no study was found assessing this relationship, and other risk factors for PUs in patients with liver resection are unknown.

This study aims to investigate the risk factors of PU following liver resection with long surgical duration.

Patient population
A retrospective analysis was performed by reviewing deidentified medical record data from the Second Affiliated Hospital of Nantong University (Nantong, Jiangsu, China). The study was approved by the medical ethics committee of the Second Affiliated Hospital of Nantong University. Inclusion criteria consisted of patients who underwent a liver resection, with a surgical duration greater than 2 hours, between January 2015 and December 2016 and received a postoperative PU assessment. Patients were excluded if a PU developed before liver resection surgery, patients died during operation or after surgery during hospitalization, or if important data, especially PU information, were missing. 

Data collection
A retrospective review of electronic medical records was used to obtain data based on the Hospital Information System (HIS) of the authors’ hospital, a tertiary referral hospital in eastern China. Predesigned Excel (Microsoft Corporation, Redwood, WA) sheets were used to collect patient information, including demographic characteristics (hospital number, age, and body mass index [BMI]), health status at admission (admission hemoglobin [Hb], admission albumin [Alb], and diabetes mellitus [DM] status [yes or no]), surgery information (length of surgery [minutes] and intraoperative blood loss [mL]), and postoperative PU information (PU occurrence time [days after surgery], location [sacrum and coccyx, heel, or ischial tuberosity], and stage). Pressure ulcers were diagnosed according to the National Pressure Ulcer Advisory Panel.⁵ 

First, the HIS was electronically searched for the aforementioned collected patient information. Then, if the information could not be found by computer search, the authors manually searched the medical records according to hospital number. Once data were collected, all patients were categorized into 2 separate groups: those who developed postsurgical PU and those who did not develop PU. All data were collected by a senior research nurse.

Statistical analysis
Characteristics for patients who developed PU and those without PU were compared by univariate analysis. Continuous variables were tested by t test, and categorical variables were tested by chi-square test or Fischer exact test. These variables were then included in multivariate logistic regression to find out the independent risk factors for postoperative PU of this patient population. Statistical analyses were performed using Stata software (version 11.0; StataCorp LLC, College Station, TX).

Patient characteristics
Between January 2015 and December 2016, 152 patients had a liver resection with a surgical duration greater than 2 hours. Of those, 24 patients were missing PU data and excluded. After exclusion, 128 patients were included in this study. Patient age ranged from 35 to 78 years with a mean age of 61.6 ± 9.5 years. The mean admission Hb was 114.0 ± 14.2 g/L, and the mean admission Alb was 31.0 ± 3.3 g/L. Fifteen patients (11.7%) had DM. The mean surgical duration was 154.2 ± 34.4 minutes, and the mean intraoperative blood loss was 257.3 ± 195.3 mL. The baseline characteristics of the included patients are listed in Table 1.

Postoperative PU
Of the 128 patients, 11 developed a PU. The postoperative PU incidence was 8.6% (95% CI, 4.4%–14.9%). All PUs developed within 3 days after liver resection surgery; 2 PUs developed in the first day after surgery, 6 on the second day, and 3 on the third day. Of the 11 PUs, 7 were on the sacrum and coccyx and 4 were in the ischial tuberosities. All PUs were classified as stage 1. When PUs developed, patients received a pressure-relief mattress, hydrocolloid dressing, and repositioning assistance every 2 hours for treatment. All PUs healed 2 to 5 days after initiation of treatment; healing was determined by visible evidence of the wound covered by skin. 

Risk factors for postoperative PU
Of the 11 patients with a PU and the 117 without, the characteristics of patient age, BMI, and admission Hb were not significantly different between the 2 groups (P > .05). However, admission Alb, DM status, length of surgery, and intraoperative blood loss were significantly different between the 2 groups (P < .05). The baseline characteristics comparison between the 2 groups are shown in Table 1. 

Admission Alb, DM status, intraoperative blood loss, and length of surgery were further analyzed by multivariate logistic regression. After regression analysis, only length of surgery (odds ratio [OR] = 1.008; 95% CI, 1.002–1.146) and intraoperative blood loss (OR = 1.005; 95% CI, 1.001–1.124) were the independent risk factors for postoperative PU of this patient population. The logistic regression analysis is listed in Table 2.

In this study, the postoperative PU incidence in patients who underwent liver resection for longer than 2 hours was 8.6% (95% CI, 4.4%–14.9%). Length of surgery was found to be an independent risk factor for postoperative PU in these patients. The OR value for length of surgery and PU risk was 1.008 (95% CI, 1.002–1.146), which means when length of surgery increased every 1 minute, the PU risk will increase by 1.008 correspondingly. Schoonhoven et al⁶ reported the risk of surgery-related PU increased as the length of surgery in minutes increased (OR = 1.0061; 95% CI, 1.0035–1.0087). Their results⁶ in mixed surgical samples were similar to the present results of patients with a prolonged liver resection. Long surgical duration increases the amount of time a tissue experiences pressure and shear. Some animal model studies explained the correlation between tissue pressure time and the risk for PU development. In a porcine model, Daniel et al⁷ found pressure exceeding 35 mm Hg for 2 hours would cause ischemia, resulting in a PU. In rat models, Linder-Ganz et al⁸ reported the magnitude of cell death causing pressure strongly depends on the time of exposure.

The current study also found intraoperative blood loss was an independent risk factor for postoperative PU in patients with prolonged liver resection surgery. The OR for intraoperative blood loss and PU risk was 1.005 (95% CI, 1.001–1.124), which means when intraoperative blood loss increased every 1 milliliter, the PU risk will increase by 1.005 correspondingly. There may be an explanation for the relationship between intraoperative blood loss and PU risk. As massive intraoperative blood loss occurs, the peripheral blood vessels are vasoconstricted, reducing the supply of blood to the tissue. As Stordeur et al⁹ reported, hypotensive periods were associated with PU incidence in cardiovascular surgical patients.

The Braden Scale is the most widely used tool for predicting PU risk and has been confirmed with good performance in the clinical setting.¹⁰ A low Braden score is an important risk factor for PU; however, the present study did not use the Braden Scale for PU risk assessment in liver resection patients before the initiation of this retrospective study. Therefore, Braden score data cannot be collected. After this study, the authors prospectively began to use the Braden Scale for patients who underwent a liver resection with a surgical duration greater than 2 hours. Further study is needed to assess whether Braden score is a risk factor for the patient population studied herein.

Previous studies also showed serum Alb¹¹ and DM status¹² were related to PU incidence. In the univariate analysis of the present study, the authors still found admission Alb and DM status were significantly different between the 2 groups (P < .05), but Alb and DM were not statistically significant in the multivariate logistic regression. This is possibly due to the low sample size of this study. This study only included 128 patients, and other prospective cohorts with larger sample sizes are needed.

There are some limitations in the present study. First, it was a retrospective study with a small sample size. Based on levels of evidence from the Oxford Center for Evidence-based Medicine,¹³ the levels of evidence herein ranked 3b, indicating a low level of evidence. Second, 4 variables (admission Alb, DM status, intraoperative blood loss, and length of surgery) were included in the logistic regression, but only 11 patients developed a PU. Prospective cohorts with larger sample sizes are needed.

The present results showed length of surgery and intraoperative blood loss were independent risk factors for PU incidence after liver resection with a surgical duration greater than 2 hours. The authors recommend utilizing PU prevention strategies, such as the use of support surfaces, mattress overlays on operating tables, and repositioning every 2 hours, for liver resection patients with massive intraoperative blood loss and long surgical durations.

Contributions: Dr. Chen and Dr. Jiang contributed equally to this work; they are co-first authors.

Authors: Hong-Lin Chen, MD¹; Ai-Gui Jiang, MD²; Bin Zhu, MD³; Ji-Yu Cai, MM⁴; and Yi-Ping Song, MM⁴

Affiliations: ¹Nantong University, School of Public Health, Nantong, Jiangsu, China; ²Department of Respiratory and Critical Care Medicine, Taizhou People’s Hospital, Taizhou, Jiangsu, China; ³Department of Hepatobiliary Surgery, the Second Affiliated Hospital of Nantong University, and First People’s Hospital of Nantong City, Nantong, Jiangsu, China; and ⁴Nantong University, School of Nursing

Correspondence: Bin Zhu, MD, Department of Hepatobiliary Surgery, the Second Affiliated Hospital of Nantong University, and First People’s Hospital of Nantong City, Nantong, Jiangsu, China; pphss@126.com 

Disclosure: This work is supported by Nantong Municipal Science and Technology Bureau (granted number: MS1 2017016-3). The authors disclose no financial or other conflicts of interest.