**3. Nutritional support in AP**

### **3.1 Nutritional requirements**

Energy requirements should be estimated with IC if possible or should be given 25–35 kcal/kg/d as energy goal, the estimated protein requirements range over 1.2–1.5 g/kg/d. This may improve nitrogen balance and is related to a decrease in 28-d mortality in critically ill patients [39]. A mixed source of energy from carbohydrates, fat, and protein should be provided [40, 41]. In severe AP, carbohydrates/day should be 3–6 g/kg and up to 2 g/kg of lipid/day.

## **3.2 Enteral nutrition vs. parenteral nutrition**

Enteral nutrition (EN) is feasible, safe, and beneficial in all types of pancreatitis [42]. It is currently acknowledged that EN properly applied may be essential to enhance AP-associated malnutrition and its general effects; on the other hand, bowel rest has been associated with atrophy of the intestinal mucosa and an increase in infectious complications [43]. About 60% of patients with AP have experienced gut barrier dysfunction [8, 44]. It is important to mention that EN has immunomodulatory effects that preserve the integrity of the intestinal mucosa, in addition to stimulating intestinal motility and reducing the excessive growth of bacteria, [8, 45] and diminishing endotoxin and bacterial translocation [46–49].

The 2016 American Society for Parenteral and Enteral Nutrition/society of critical care medicine guidelines recommend EN over parenteral nutrition (PN) and show a decrease in infectious morbidity (42.6% vs. 16.1%, P < .0001) and mortality (16.4% vs. 6.1%, P = .02); [50] EN also decreases levels of TNF, IL-1, IL-6, and IL-8 [47]. A meta-analysis of eight randomized clinical trials found that EN considerably reduced mortality, organ failure, and surgical intervention compared with PN [51]. EN vs. PN mortality rates showed an increase in survival with EN (4% vs. 15.9%). In patients with SAP, EN is preferred to PN, whether administered orally or by tube, it preserves

### *Advances in Nutritional Therapy of Acute Pancreatitis DOI: http://dx.doi.org/10.5772/intechopen.106765*

the intestinal barrier function to prevent bacterial translocation. The New England Journal of Medicine demonstrated, in a multicenter randomized study, that both early tube feeding and oral diet after 72 hours given to patients with AP at high risk of complications are equivalent in reducing infection rates or death [46]. Multiple metaanalyses have been found that support the use of EN in PN, such as a Cochrane study in which eight randomized controlled studies were carried out in patients with PA comparing EN with PN, it was found that EN reduced mortality, systemic infections, and multi-organ failure [52]. Another study carried out on 381 patients confirmed the benefit of EN over PN in patients with SAP, and the results showed lower mortality, fewer infectious complications, a lower rate of organ failure, and surgical intervention [49]. Several trials have suggested that the optimal EN route is the nasogastric route, putting it as an alternative to the nasoduodenal or nasojejunal routes [53–55]. As demonstrated in multiple trials involving a sample of 157 SAP patients, the results were that nasogastric feeding is safe and well tolerated compared with nasojejunal feeding [41, 56]. Nevertheless, as shown by multiple randomized trials that have associated total PN (TPN) with risks of infection and other complications [57]. PN should still be minimized unless the enteral route is not available, not tolerated, or not meeting caloric requirements [58, 59]. PN causes increased inflammatory cytokines, leading to a proinflammatory state in the gastrointestinal tract [58, 60]. Overall, PN is more expensive than EN or oral nutrition and associated with more complications [61].

### **3.3 Nutrition support in mild and moderate AP**

In the care of patients with mild-to-moderate AP, food can be given orally once nausea, vomiting, and abdominal pain have subsided and appetite has returned [62, 63]. The conventional way of feeding patients with AP is increasing, that is, once the abdominal pain has disappeared and the pancreatic enzymes have decreased, the first 24 hours are given clear liquids to later consume a low-fat soft diet for 24 hours to check tolerance, and then start a solid low-fat diet [57]. However, a randomized study determined that providing a soft diet with clear liquids to patients with mild AP did not show significant differences in the two participating groups. In addition, it was determined that starting treatment with a solid diet is associated with a shorter hospital stay (mean of 5 vs. 8 days of starting with clear liquids, p < 0.001) . On the other hand, a current open-label randomized trial [64] demonstrated no difference in tolerance to refeeding when comparing both the stepped and immediate full-calorie diets. Likewise, it was mentioned that fasting caused by constant abdominal pain in patients with moderate AP should not exceed five days, and if this is the case, a catheter should be placed [62, 63, 65].

Theory mentions that nasojejunal feeding is preferred over nasogastric feeding because it is assumed to be more tolerable for patients [66]. In nasojejunal feeding, placing the tube in the jejunum beyond the duodenum avoids stimulation of the already inflamed pancreas, causing less pain. However, there are studies that compared nasojejunal and nasogastric feeding and did not find significant differences [67, 68]. The current indication is that continuous feeding over bolus feeding is recommended for patients requiring tube feeding [3, 66]. EN demonstrated better feeding tolerance and decreased interruptions due to high residuals and vomiting in the continuous infusion when compared with the bolus group [69, 70].

The method of administration of the nasogastric diet is through interrupted boluses (200–300 mL 5–6 times a day) under control of gastric residual volume (GRV) or continuous infusion (30–50 mL/h), unlike NE via NJT that is administered in continuous infusions. Gradually increasing the flow rate: from 20 to 30 ml/h to 100 to 125 ml/h. To avoid complications (regurgitation, aspiration, or pneumonia), EN *via* the nasogastric route should be interrupted at GRV > 200 mL. The EN must cover a minimum of 60% of the energy requirement. When intolerance to EN occurs, resulting in effects such as diarrhea, the rate of feed delivery should be decreased. When this is not enough, a switch to EN should be considered. The continuous evaluation of the nutritional requirement and the laboratory investigations must be carried out weekly with the objective of optimally carrying out the nutritional support and if required, the modification of the type or formula if indicated. In addition, it is essential to carry out adequate care of the tube (in EN) or catheter (in PN) to avoid infections and other complications related to the catheter and the tube [1, 71]. Due to its nature, parenteral nutrition is reserved only for patients who present intolerance or are unable to receive enteral nutrition [52, 72].

### **3.4 Nutrition support in severe AP**

At the international level [62, 63, 65, 73, 74], it is mentioned that in patients with SAP, nutritional support should be provided through enteral feeding (grade of recommendation: A). Even if complications such as fistulas, ascites, and pseudocysts occur, EN is preferred over PN (grade of recommendation: C) [63, 65]. After surgery for pancreatitis, EN is recommended through intraoperative jejunostomy (grade of recommendation: C) [65]. Since enteral tube feeding can provide safe nutritional support in AP even in cases where gastric outlet is obstructed [75] in this case, the tip of the tube should be placed distal to the obstruction (grade of recommendation: C) [65]. However, early EN (enteral tube feeding within 24 hours of presentation) has not been shown to improve outcomes in SAP patients, compared with oral feeding starting at 72 hours. [76]

The only real contraindication to EN is prolonged paralytic ileus. However, according to the European Society for Parenteral and Enteral Nutrition guidelines, it is advisable to combine PN with a small content of an elemental or immunopotentiating diet (10–30 ml/h) continuously infused into the jejunum. Regarding delivery times, continuous infusion is preferred over bolus administration (grade B recommendation) [65, 66].

### **3.5 Time of enteral support**

EN should be initiated when the patient has an established condition for gut permeability and should start after adequate resuscitation and stable hemodynamic status. Many studies have shown the advantages of early enteral feeding in SAP and how convenient it is for the prognosis [77]. A meta-analysis conducted by Petrov [78] showed that the timely administration of EN during the first 48 hours of admission improved the reduction of multiorgan failure, complications of infectious origin, and mortality rate in comparison with PN. After this period, there were no significant differences observed in comparison with PN. Starting EN before 48 hours provide several advantages in more successive studies and another meta-analysis. Many studies have shown this association, and a more recent meta-analysis, improving the time, demonstrated that starting EN within 24 hours after hospital admission was associated with lower complications for predicted severe or SAP, but not for mild to moderate pancreatitis. [76, 79–82]. A multicenter randomized controlled trial compared early EN within 24 h versus an on-demand oral diet of 72 h, with tube feeding

provided on day 4 if the oral diet was not tolerated. This study showed that patients with moderate pancreatitis, who do not require intensive care, can use an oral diet on demand and only through a tube from day 4 if the oral diet is not successful [76].

### **3.6 Gastric vs. small bowel feeding**

In response to decreased efficiency in pancreatic secretion during PA, nasogastric feeding has been considered to be similar to nasojejunal feeding when the following parameters are assessed: pain, aspiration, compliance with energy balance, and mortality; this even though it was previously believed that feeding through the small intestine could decrease the stimulation of the pancreas and digestion [55].

Feeding in the stomach is the most used because it is easier and cheaper, and it optimizes the time for the patient who requires EN, since through the intestine, not only a special technique is required, but also more time for the correct one tube placement. However, this technique is mainly used for patients who do not tolerate gastric feedings, such as obstructions, edema, severe gastroparesis, or pseudocysts. Likewise, the use of jejunal probes is indicated for post-operative patients in different conditions where it is required [65, 83].
