Obesity: A Risk Factor for Infection after Surgery

*José Alonso Suclla-Velásquez and Connie Smedts*

### **Abstract**

Obesity is a prevalent health problem all over the world. It is associated with several diseases including infections. It impairs the immune system function by plenty of mechanisms. For instance, leptin and adiponectin are cytokines produced by the adipose tissue, both participating in immunity, but their effects are impaired in obese patients. Moreover, immune cells also show defects in their functions. They produce a pro-inflammatory state and contribute to obesity-related diseases. Innate immune system and adaptive immunity are both impaired in obese patients which causes a poor response to infections. In addition, in surgical site infections (SSI), there are local factors that must be considered. The large adipose panicle and visceral adipose tissue increase the surgical technique difficulty and extend the operative time. Besides, the adipose tissue has poor oxygenation and reduces operative field. It has been proven that obesity is associated to surgical site infection irrespective of type of surgery. However, minimal invasive surgery has demonstrated that reducing surgical trauma can diminish the risk for surgical site infection.

**Keywords:** obesity, surgery, surgical site infection, immune deficiency, surgical complication

#### **1. Introduction**

Nowadays, obesity is a serious health problem which affects all countries irrespective of economic status. It is produced by an energy imbalance, and then there is an increase in body-fat mass. A body mass index (BMI) more than 30 kg/m2 is defined as obesity [1].

There are plenty of diseases that are linked to obesity; the most common are metabolic syndrome, type 2 diabetes mellitus, coronary disease, and hyperlipidemia. Despite not being as well-known as the previous examples, obesity is strongly associated with infection [2].

Obese patients have a higher risk of nosocomial infections because medical care of these patients requires special procedures, equipment, and staff. Moreover, obese patients are usually immobilized which is a risk factor for decubitus ulcers and contributes to increase length of stay [3].

Although there are some controversial studies, an association between caries rates and elevated BMI has been proven. Dietary habits characterized by high consumption of soft drinks, fast food, and refined sugar contribute to dental caries as well as obesity [4]. In addition, it is well-known that severe infections in the face and neck usually have an odontogenic origin and obesity is a risk factor for the infection progression. Besides, an association has been described between the levels of tumor necrosis factor alpha in gingival crevicular fluid and BMI [5]; therefore, there is a systemic effect of obesity in oral health.

Obesity is related to respiratory diseases including nosocomial pneumonia and community-acquired respiratory tract infections [3]. In these patients, a decreased lung volume and a restrictive ventilatory pattern have been noticed. Excess weight on the anterior chest wall, abdominal obesity, and the presence of the adipose tissue in the intra-abdominal visceral tissue increase muscle work in breathing, diminish lung expansion, and increase airway resistance. These mechanical changes and augmented adipose tissue produce an inflammatory state that contributes to metabolic disease [6]. Other respiratory diseases associated to obesity are obstructive sleep apnea, chronic obstructive pulmonary disease, and asthma [6, 7].

On the other hand, obesity is a risk factor for the development of steatosis in patients with chronic hepatitis C infection and biliary disease with infectious complications [3]. Skin and soft tissue infections are also more prevalent in obese patients [2, 3]. The adipose tissue affects the pharmacokinetics and pharmacodynamics of antibiotics. Therefore, some special considerations must be taken when treating an obese patient [8, 9].

Even though there are some important studies that demonstrate obesity is not a risk factor for surgical complications [10], there are still some evidence that contrast with these researches [11]. On the other side, it is well-known that obese patients have a higher risk for surgical site infections (SSI) particularly when open surgery is performed. This phenomenon has been associated to low oxygen tension in the adipose tissue as well as a poor immune response observed in obese patients [3, 10, 11].

In this chapter we will review the available evidence about obesity as a risk factor for surgical infections in most common surgical procedures, considering pathophysiology as well as relevant clinical information.
