Skin Perfusion After Abdominal Surgery

Introduction Wound healing problems after surgery are a stressful experience for patients. Wound dressing changes are often on a daily basis and can cause considerable discomfort to the patient as these are often painful. Wound healing problems can lead to complications like wound infection, hernia formation, wound rupture or even tissue necrosis. These complications are often associated with prolonged hospital stays and reoperations and cause an economic burden to the hospital health budget. It is generally accepted that adequate blood perfusion of the wound edges is required for optimal wound healing. Greater understanding of the impact of a surgical procedure on skin perfusion may help to reduce postoperative wound healing problems. Such will have great clinical relevance.

Aim Can postoperative wound complications involving the abdominal wall be explained by changes in skin blood perfusion?

Main results from the literature study In surgery, knowledge on the vascular anatomy is applied in order to place incisions in such a manner that a good approach is combined with minimal damage to the vascular anatomy. Knowledge on vascular anatomy does not provide exact information on how skin perfusion alters after surgery. The invasive method indocyanine green fluorescence-agiography (ICG-FA) can be used to evaluate intraoperatively the effect of an abdominoplasty on skin perfusion. However, animal studies in flap surgery have clearly shown that tissue perfusion is a dynamic process. Using dynamic infrared thermography (DIRT) in a clinical setting revealed that flap perfusion is a dynamic process that takes place over days during the postoperative phase. DIRT is a non-invasive technique that relies on measuring skin surface temperatures. Studies have shown that there is a close correlation between skin temperature and skin perfusion. DIRT has been shown to be a good alternative to ICF-FA to visualize skin perfusion.

Purpose of the study The purpose of the study is to analyze the impact of a surgical procedure on skin perfusion of the abdominal wall in order to increase our understanding on how postoperative wound healing problems can be avoided.

Study population The study population will include patients that are undergoing one of the following operations; a) abdominoplasty, b) breast reconstruction after breast cancer with a free flap from the lower abdomen and c) endovascular stenting of the abdominal aorta for aneurysm. These surgical procedures are frequently performed procedures at the University Hospital of North Norway (UNN). Based on the vascular anatomy of the abdominal wall, each procedure will have an impact on the skin perfusion of the abdominal wall.

Material and Methods Approval will be obtained from the regional ethical committee and the principles outlined in the Declaration of Helsinki will be followed.

Study I The inclusion criteria are patients scheduled for abdominoplasty who are non-smokers or have stopped smoking at least 3 months prior to surgery and have no supraumbilical abdominal scars from previous surgery Study II The inclusion criteria are patients scheduled for secondary unilateral free abdominal flap breast reconstructions who are non-smokers or have stopped smoking at least 3 months prior to surgery and have no abdominal scar from previous surgery.

Study III Patients who are scheduled for endovascular stenting of the abdominal aorta.

DIRT will be performed on the day before surgery, intraoperatively and on the 1st, 3rd and 6th postoperative day with all DIRT examinations performed in the same supine position for study I and II. For study III, the same protocol will be used, however, no intraoperative DIRT examination will be performed. For study III, thermal images are taken from both lower extremities during the abdominal DIRT examination to see if stenting causes a change in rewarming of the lower extremities following stenting.

An IR camera (FLIR ThermaCAM S65 HS FLIR Systems, FLIR Systems AB, Boston, MA) will be positioned directly above the exposed anterior thorax and abdomen. This camera can produce sequences of high-definition digital IR images with an accuracy of 0.1º C. Thermal emissivity is set to 0.98 and the accuracy of the camera will be regularly checked against a black body with a traceable temperature source (Model IR-2103/301, Infrared Systems Development Corp., Florida, USA). IR images are taken at regular intervals to register the rate and pattern of skin recovery for 3 minutes after a mild cold challenge. Images are electronically stored and afterwards processed using image analysis software ThermaCAM Researcher Pro 2.8 SR-1 (FLIR Systems AB).

The pre- and postoperative images are taken in a dedicated laboratory (room temperature 21-23°C) before and during recovery following a cold challenge after an acclimatization period of 10 minutes with the thoracic and abdominal wall exposed. The thermal challenge is delivered by blowing air at room temperature over the skin surface for 2 minutes with a desktop fan. The intraoperative examination is performed with the patient in general anaesthesia just before and at the end of surgery. The thermal cold challenge is performed by washing the thorax and abdomen evenly for 1 minute with gauze soaked in saline at room temperature (22-23°C).

The abdomen is divided into vascular zones as defined by Huger. The mean skin temperature is calculated for each zone in the postoperative phase before cooling, at end cooling and at 1, 2 and 3 minutes recovery. A qualitative analysis of the changes of pattern and rate of recovery of hot spots within each zone is made and compared with the results from the other zones. A one tailed t test for paired variables is use to see if there is a statistically significant in the mean temperatures between zones at each time point of rewarming. Statistical significance is defined as p<0.05.

Publications The results from each study will be published in an international peer-reviewed journal.