Nutrition in Surgery Part II

Undergoing a surgical procedure causes the nervous system to activate a stress response that sends signals from the surgery site to specific areas of the brain. This leads to the release and enhanced activity of several hormones including the stress hormone, cortisol, as well as proteins that are associated with inflammation at the injury site [1]. As the levels of hormones (e.g., cortisol, growth hormone, glucagon) and inflammatory proteins increases, the body’s stress response to the surgery worsens.

Increased cortisol levels in particular, cause the body to burn large amounts of energy in the form of blood sugar. However, it also promotes the production of sugar in the liver, which raises blood sugar levels. The body mostly uses stored muscle protein and fats to produce sugar that is used as an energy source [2]. High blood sugar levels subsequently disrupt wound healing and increase the risk of surgery-related complications such as inadequate blood flow, infections, sepsis, and death [1].

Nutrition Status on Surgical Outcomes

Nutritional supplementation helps improve the outcomes of surgery by reducing the occurrence of harmful changes in nutrient metabolism [3]. For instance, supplementing the diet with amino acids, glucose (sugar), and additional nutrients reduces the breakdown of stored nutrients (e.g., muscle protein), which in turn prevents dramatic increases in blood sugar and inflammation that can hinder healing and lead to serious complications [4]. Accordingly, individuals whose nutritional status is poor before undergoing surgery tend to have an abnormal stress response [3]. Therefore, supplementation is recommended for such individuals prior to surgery [3, 4].

Pre-operative and post-operative Nutrition Guidelines

Pre-operative screening for malnutrition or obesity is a standard procedure. For individuals who are considered high risk due to nutritional deficiencies, a nutritional and physical exercise (if possible) regimen is recommended as a pre-habilitation approach at least 7-10 days prior to surgery [5, 6]. In particular, oral nutritional supplementation (ONS) along with exercise reduces the risk of post-operative complications and shortens the length of stay for individuals undergoing therapy [5].

Furthermore, fasting is typically required prior to surgery in order to minimize the amount of food in the digestive tract and prevent vomiting that can lead to respiratory problems during the procedure, as different types of food leave the stomach at different rates [7]. In general, fasting involves only consuming clear liquids for up to 2 hours prior to surgery and refraining from eating for at least 8 hours before surgery [7]. Similarly, overnight fasting involves the consumption of only clear liquids 8 hours before the procedure [7-9]. However, preoperative nutritional or carbohydrate loading (e.g., 1 cup of coffee or 1 cup of orange juice) 2 hours before surgery has demonstrated similar stomach content as overnight fasting and it does not pose a serious risk for vomiting-induced breathing problems [8]. The same observation was made for those who ate one slice of buttered toast with either one cup of tea or one cup of coffee with milk [9]. Therefore, the final recommendation for overnight fasting versus preoperative carbohydrate loading is based on the physician’s guidelines [7].

Beginning to eat shortly after the procedure has been shown to resolve post-operative issues earlier, promote wound healing, reduce the length of the hospital stay, and decrease infection rates [6]. One study in particular, compared oral intake at postoperative day 1 to that of day 2 in order to determine the optimal time to resume oral intake following surgery. One group started a liquid diet with ONS on postoperative day 1 and the second group received the same on postoperative day 2. Both groups advanced to a regular diet within 24 hours of starting the liquid diet. The findings from this study demonstrated that resuming oral intake 1 day following surgery promoted more rapid gastrointestinal recovery as the passage of flatus (passing gas) and a bowel movement occurred earlier in this group in comparison to those who resumed oral intake 2 days following surgery [10].

Most patients who undergo surgery also experience periods of undernourishment due to a reduced appetite during the post-operative period. This may lengthen the hospital stay and it increases the risks of post-operative illnesses and even death (3, 4) [11, 12]. Accordingly, ONS with high protein supplementation in particular, has been recommended as a routine post-operative approach for enhancing recovery in surgery patients and this should begin 1 day following the procedure [12]. If food cannot be consumed orally, the intravenous (IV) administration of nutrients should begin within 24 to 48 hours of surgery [6]. Clinical research regarding the benefits of nutrient supplementation through an IV during surgery is ongoing as this may further improve patient outcomes.


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