Factors associated with the healing of complex surgical wounds in the breast and abdomen: retrospective cohort study

ABSTRACT Objective: to estimate the healing rate of complex surgical wounds and its associated factors. Method: retrospective cohort study from 2003 to 2014 with 160 outpatients of a Brazilian university hospital. Data were obtained through consultation of the medical records. Survival function was estimated using the Kaplan-Meier method and Cox regression model to estimate the likelihood of the occurrence of healing. Results: the complex surgical wound healing rate was 67.8% (95% CI: 60.8-74.9). Factors associated with a higher likelihood of wound healing were segmentectomy/quadrantectomy surgery, consumption of more than 20 grams/day of alcohol, wound extent of less that 17.3 cm2 and the length of existence of the wound prior to outpatient treatment of less than 15 days, while the use of hydrocolloid covering and Marlex mesh were associated with a lower likelihood of healing. Conclusion: the wound healing rate was considered high and was associated with the type of surgical intervention, alcohol consumption, type of covering, extent and length of wound existence. Preventive measures can be implemented during the monitoring of the evolution of the complex surgical wound closure, with possibilities of intervention in the modifiable risk factors.


Introduction
Various international guidelines are available for chronic wounds, such as venous, arterial and pressure ulcers and diabetic foot ulcers, with recommendations for the prevention and treatment of these wounds.
For wounds of acute etiology, e.g., surgical wounds, there are few care recommendations, which generates a variety of actions in the practice, without the clarity regarding specific factors that assist or delay the cicatrization process. Associated with this fact, the large number of dressings available, the large number of health professionals involved, and the many opinions regarding effective wound care must be considered (1) .
Surgical wounds (SW) are considered acute, planned and carried out with overlapping edges, which heal by primary intention and have a tendency to regress spontaneously and complete within the expected period.
When there is no edge proximity the healing of surgical wounds is by secondary intention. These wounds require more time to heal due to the space between the edges and need greater granulation tissue formation for completion until contraction and epithelialization occur (2) .
It is estimated that 234 million surgeries are performed worldwide each year, with the majority of the SW resulting in healing by first intention (3) . First intention SW can become complex (CSW) when they present complications, such as infection, hematoma and seroma, that cause dehiscence, requiring healing by secondary intention. The incidence of complex surgical wounds described in the literature ranges from 0.5% to 3.0% for adults and 10.0% for older adults, with mortality ranging from 10.0% to 45.0%. The number of new cases of CSW has remained unchanged since the 1950s, despite the scientific advances of the last century (4)(5)(6) .
In the clinical practice in various Brazilian institutions, doubts still remain about the factors that slow the CSW healing process and which dressings are effective for healing this injury. It is known that the aggravation of the CSW is associated with increased morbidity, mortality and costs to health systems, with hospitalizations and treatments (7)(8)   In this type of analysis, the main characteristic is the presence of censoring, which is the partial observation of the response. That is, for some reason, the monitoring of the patient is interrupted. In this study, censoring occurred due to lack of occurrence of healing by the end of the study, which included death, transfer to another

Results
A total of 160 medical records of patients with complex surgical wounds in the breast or abdomen region were identified and all met the inclusion criteria. No medical records were excluded due to lack of registration of three or more items. Therefore, 160 individuals and 171 wounds (11 patients had two wounds) were included in this study. The CSW healing rate was 67.8% (95% CI: 60.8-74.9). Of the 52 patients that were discharged without being cured but with area and depth of the CSW reduced, 26 (16.3%) were transferred to the Primary Health Unit, 14 (8.8%) were referred for surgery, either due to cancer relapse or for closure of the CSW by third intention, 11 (6.9%) abandoned the treatment and 1 (0.6%) patient died prior to wound closure.  (Table 1). unit and surgery. The survival analysis method makes it possible to incorporate the information contained in the censored data into the statistical analysis (9) .
In the univariate analysis of the data, two survival analysis techniques were used: the first was the Kaplan-Meier method for the construction of survival curves and the second was the Cox proportional hazards model, to estimate the likelihood of healing (hazard ratio), with confidence intervals of 95% (95% CI) (9) . As it was a study of medical records, the researchers signed the Terms of Commitment for use of the data.    In the univariate analysis (Tables 1 and 2

Discussion
The CSW has a great impact on the quality of life of patients due to the pain, unpleasant odor and exudate from the lesions, which can be associated with sleep problems, restriction of activities and leisure, reduced productivity at work and social isolation, in addition to economic burdens due to the treatment of the injury (10) .
This is the first retrospective cohort study published nationally or internationally that estimated the complex wound healing rate and associated factors with outpatients. Due to lack of specific studies on CSW, comparisons of data with other investigations, at times, were extrapolated to chronic wounds.
The healing rate in this study is similar to data from the United States, considering all types of wounds (7) .  (8) .
A phase II intervention study of a protocol to reduce the incidence of complications in SW in obese gynecological oncology patients, conducted in the United States, estimated an increase of at least 3,500 US dollars in the surgical procedures due to the treatment of CSW (11) .
The high cost associated with patients with chronic wounds was also reported in Wales, UK. The total cost was approximately 328.8 million pounds, a mean of 1,727 pounds sterling per patient, accounting for 5.5% of the National Health Service (NHS) spending (12) .
Regarding the predictors associated with healing of the CSW, consumption of more than 20.0 grams of alcohol was a protective factor for wound healing, contradicting previous studies. In a systematic review with metaanalysis, the preoperative consumption of alcohol was associated with an increased risk of postoperative morbidity in general, including wound complications (HR = 1.23; 95% CI = 1.09-1.40). In the same study, low and moderate preoperative alcohol consumption did not seem to be associated with the occurrence of complications in the postoperative period (13) . However, an experimental study with rats showed that acute alcohol intoxication did not alter the healing of colonic anastomosis wounds, although it increased the death rate in the postoperative period (14) .   (15) . Similarly, the smaller extent of the wound has been associated with an increased rate of wound healing, considering that less formation of granulation tissue and reepithelialization are required. The length of existence of the wound prior to outpatient treatment also acted as a protective factor in the wound healing.
One possible explanation is that acute wounds tend to heal faster when compared with chronic wounds (16) .
Another factor that may contribute to the result is the more rapid institution of the therapeutic treatment, with the prognosis for wound closure being better as possible complications can be ameliorated.
Conversely, the Marlex screen delayed wound healing. This occurred due to it being a foreign body, triggering a reaction in the tissues, which could vary from an exudative process, a foreign body granuloma reaction, to a hypersensitivity immune response of the patient and formation of adhesions (17) . Another experimental study with rats showed that the use of polypropylene mesh surrounded by fibrous tissue was more effective in the correction of induced abdominal hernias, with a lower degree of macroscopic adhesions when compared to polypropylene mesh (18) .
Despite the extensive literature (19)(20) demonstrating the use of hydrocolloid as an effective wound closure covering, in this study it was negatively associated with the healing process. This is because patients who used hydrocolloid, also initially made use of charcoal with silver, to reduce the bacterial load of the lesions with critical colonization or infection, indicating that these were patients with greater wound severity (21) that required more time for the healing of the wound.
One limitation of this study refers to the collection of data from secondary sources, not always adequately