What is Postoperative Ileus (POI)?

Postoperative ileus (POI) is a condition characterized by transient impairment or cessation of normal bowel function following surgery. It commonly occurs after abdominal surgery but can also occur after non-abdominal procedures. POI typically manifests as delayed passage of gas and stool, abdominal distension, bloating, and discomfort.


Several factors contribute to the development of postoperative ileus:


  • Surgical trauma: Manipulation of the intestines during surgery can lead to inflammation, disruption of normal peristalsis (the rhythmic contractions that propel food through the digestive tract), and temporary paralysis of the bowel muscles.


  • Anesthesia: Anesthetic agents and pain medications used during surgery can inhibit bowel motility and contribute to the development of ileus.


  • Inflammatory response: Surgery triggers an inflammatory response in the body, which can further impair bowel function and delay recovery of normal gastrointestinal motility.


  • Electrolyte imbalances: Fluid shifts and electrolyte disturbances during surgery can affect bowel function and contribute to ileus.


  • Opioid medications: Opioid pain medications commonly used after surgery can slow down intestinal motility and exacerbate ileus.


What is the relationship between POI and oxidative stress?

The relationship between postoperative ileus (POI) and oxidative stress is an area of ongoing research. Oxidative stress occurs when there is an imbalance between the production of reactive oxygen species (ROS) and the body’s antioxidant defenses, leading to cellular damage. Several factors related to surgery and inflammation can contribute to oxidative stress, which may in turn play a role in the development of POI.


  • Surgical Trauma: The physical trauma caused by surgery can lead to tissue injury and inflammation, triggering oxidative stress. Injured tissues release pro-inflammatory cytokines and activate immune cells, which produce ROS as part of the inflammatory response.


  • Ischemia-Reperfusion Injury: During surgery, blood flow to the intestines may be temporarily interrupted, leading to ischemia (lack of blood flow) and subsequent reperfusion (restoration of blood flow). This ischemia-reperfusion injury can generate ROS and contribute to oxidative stress.


  • Inflammatory Response: Surgery induces a systemic inflammatory response, characterized by the release of pro-inflammatory cytokines and activation of inflammatory pathways. Chronic inflammation and oxidative stress are closely linked, and excessive ROS production during inflammation can exacerbate tissue damage and impair intestinal function.


  • Gut Microbiota: Disruption of the gut microbiota, which can occur during surgery and in the postoperative period, may contribute to oxidative stress and intestinal dysmotility. Alterations in the gut microbiota composition can affect intestinal barrier function and immune responses, potentially leading to increased ROS production and oxidative damage.


  • Medications: Some medications commonly used during and after surgery, such as opioids and nonsteroidal anti-inflammatory drugs (NSAIDs), have been implicated in the generation of oxidative stress. Opioids, in particular, can slow intestinal transit and exacerbate POI, potentially through mechanisms involving oxidative stress.


While the precise mechanisms linking oxidative stress to POI are not fully understood, oxidative damage to intestinal tissues and disruption of normal cellular signaling pathways may contribute to impaired gastrointestinal motility and delayed recovery of bowel function.