Acute pancreatitis is a common intra-abdominal inflammatory condition of varied aetiology. The disease is mild in the vast majority of patients and has a favourable outcome. The acute severe form of the disease on the other hand is a lethal form with a high mortality and morbidity. A number of strategies have provided clinical benefit in severe acute pancreatitis (SAP). Of these, nutritional management is by far the most effective. SAP is associated with persistent end-organ failure, commonly respiratory, circulatory and renal. Treatment is targeted to support these organs. As of now there is no definitive therapy for acute pancreatitis. Patients are managed with fluids, analgesics, antibiotics and nutritional supplements besides adequately treating local complications such as pseudocyst and walled-off pancreatic necrosis by suitable interventional methods, be it endoscopic or percutaneous. The focus here is nutritional support in the management of SAP.
Which Form of Nutrition: Parenteral or Enteral?
This depends largely on the functional integrity of the stomach and small intestine. Patients of SAP often have poor gastric emptying and paralytic ileus, which is made worse with the use of narcotics. Moreover, local complications of pancreatitis (peripancreatic fluid collections) can have a pressure effect on the stomach and/or duodenum. As a result oral feeds may not be possible in these patients. Patients on ventilator support also cannot be given oral feeds.
Enteral feeding through the nasogastric or nasojejunal tubes is often not tolerated by patients because of discomfort. In addition, these tubes often get displaced or withdrawn. Reinsertion of the tubes, under endoscopic or radiological guidance, is cumbersome in such patients. All these factors favour parenteral feeding. The distinct advantage of enteral nutrition is that it prevents mucosal atrophy and transmigration of bacteria (an important causeof sepsis in SAP). Also, enteral feeding augments intestinal motility and is cheaper than parenteral preparations. Enteral nutrition improves motility in patients with paralytic ileus. The relative merits of these forms of nutritional therapy have been evaluated in a systematic review. Eight published randomized trials including a total of 348 patients were included. Enteral feeding was given through a nasojejunal tube and parenteral nutrition through a catheter placed in a central vein. Enteral nutrition was shown to reduce mortality, multi-organ failure, systemic infection and surgical intervention in comparison with parenteral nutrition. The length of hospital stay too was shown to be reduced. In view of these, enteral nutrition appears to be a better option while managing patients of SAP and has been recommended by the American College of Gastroenterology, American Gastroenterological Association and International Association of Pancreatology.
When should enteral feeding be started?
Patients with mild acute pancreatitis can usually be started on oral feeds in 2–3 days. Those with moderately severe acute pancreatitis can be started on oral feeding only after a variable period and hence should receive enteral nutritional support. Early enteral feeding has been shown to avoid end-organ failure in a large series of patients (1200).
Enteral feeding started within 48 h of onset of illness was associated with organ failure in 21% of patients as opposed to 81% when enteral feeding was started after 48 h. This benefit of early enteral feeding has also been shown in a recent meta-analysis. However, there was no benefit in mortality with early enteral feeding. In yet another randomized controlled trial, early enteral feeding (within 24 h) was compared with on-demand enteral feeding after 72 h.
The primary endpoint of this study was major infection or death. The study did not detect any significant difference in the primary endpoint in either group (early or on-demand feeding). However, it did show that patients receiving on-demand nutrition tolerated oral feeds without using a tube.
- Nasogastric or Nasojejunal
Should the feed be administered in the stomach through a nasogastric (NG) tube or in the jejunum through a nasojejunal (NJ) tube? Gastric feeding is thought to increase pain and aggravate pancreatitis due to food-induced pancreatic stimulation. In view of this, NJ feeding is practised. However, placement of a NJ tube is cumbersome and needs a skilled endoscopist or radiologist. It causes more inconvenience to patients. A nasogastric (NG) tube is thus an alternative. A number of studies have been published comparing NG and NJ feeding. The results of these studies can be summarized as follows: There was no difference in mortality. Feeds were equally tolerated in the two groups and NG feeding is simple. NG feed was not shown to increase pain and is thus as good as NJ feeding. A meta-analysis subsequently published showed no difference in mortality, hospital stay and infection rate between the two groups. Both forms of feeding were equally well tolerated. NJ feeding thus is not advised in the management of most patients with SAP. However, it still has a place when the patient has a high risk of aspiration. Also, patients on a ventilator and those not tolerating NG feed should be fed through NJ tube. The other issue concerning enteral feeding in SAP is the composition of the feed.
- Type of Formulation
Various commercially available formulations include (1) polymeric formulations comprising complex lipids, carbohydrates and proteins and (2) elemental formulations comprising simple amino acids, carbohydrates and free fatty acids. Other formulations used are glutamine-rich feeds and feeds with probiotics, fibres, etc. Immuno-nutrition using arginine, glutamine and polyunsaturated fatty acids has been evaluated in multiple studies and compared with standard feeding. A metaanalysis showed some benefit in mortality but not for prevention of infection, end-organ failure or inflammatory response. This benefit was not seen with the use of probiotics or fibre-based feeds. A systematic review did not show any benefit of immuno-nutrition or probiotics. It also showed that polymeric formulations are as well tolerated as oligomeric ones (elemental).