Enteral Nutrition

Besides providing systemic nutrition, what are the benefits of enteral nutrition?

Avoids GI mucosal atrophy
Maintains gut-associated lymphoid tissue
Decreases infectious complications from bacterial translocation
Yields better glycemic control than parenteral nutrition
Less risks compared to parenteral nutrition (i.e. central venous catheter-related complications)
Less cost than parenteral nutrition

Do all patients benefit from early enteral nutrition?

No. Prospective randomized controlled trials (RCTs) show that patients with Albumin > 4g/dl undergoing GI surgery have no differences in outcome and complications when receiving enteral nutrition compared to maintenance IV solutions in the initial days following surgery.
However, most prospective RCTs and meta-analyses show that patients with severe abdominal or thoracic trauma have decreased infectious complications with early enteral nutrition compared to unfed or parenteral nutrition. The exception is patients with closed-head injury.

What is special about head trauma patients?

They are at risk for gastroparesis, with a higher risk of aspiration.

What are indicators of gastroparesis?

Gastric residuals >200mL over 4-6hrs
Abdominal distension

Consider NGT decompression and postpyloric feeding.

What about patients with enterocutaneous fistula?

Enteral support is acceptable for low output enterocutaneous fistulas (<500 ml/day)

When is a good time to institute enteral feeds?

Early enteral support should be instituted following resuscitation from major trauma and patients where a prolonged postoperative recovery is anticipated.

Healthy patients with good nutritional status can tolerate 10 days on maintenance fluids before significant protein catabolism occurs.

Among hospitalized patients, how many present with alterations in nutritional parameters?

15-65%, and once hospitalized with an obligated fast, 50-100% become undernourished!

Should I start enteral feeds through a nasogastric tube?

Acceptable for short-term, but has aspiration risks, and often dislodges.

Reserve for intact mental status and protected laryngeal reflexes.

What are problems associated with postpyloric nasojejunal tubes?

They are often difficult to place, and may need assistance with fluoroscopic guidance.

What is a PEG?

Percutaneous endoscopic gastrostomy

What are common indications for PEG placement?

Major facial trauma
Impaired swallowing
Oropharyngeal or esophageal obstruction
Cerebrovascular disease
Chronic neurological disorders

What are contraindications to PEG placement?

Gastric neoplasm
Ascites
Coagulopathy
Varices
Abdominal Wall Defect
Inability to perform endoscopy or transilluminate abdominal wall

What are the two techniques for PEG placement?

1. The Push Technique - uses a Foley catheter pushed through the abdominal wall via Seldinger technique using dilators
2. The Pull Technique - uses a long tapered PEG tube pulled from the mouth through the stomach across the abdominal wall via Seldinger technique

PEG tubes come in sizes ranging from 16-28Fr, but 20Fr is commonly used.

How many surgeons are necessary to perform a PEG?

Two. One to perform endoscopy, and one to place the catheter.

What are the components of the "Pull Technique" for PEG placement?

1. IV sedation for endoscopy, with patient placed supine.
2. Placement of endoscope in stomach with inspection and insufflation.
3. Endoscopic transillumination of upper anterior abdominal wall (usually proximal to incisura)
4. Depress abdominal wall where light is seen... endoscopist should visually confirm indentation.
5. Infiltrate skin at site with local anesthetic.
6. Use a #11 blade to make 5-10mm skin incision.
7. Place 14G needle through incision into insufflated stomach.
8. Allow endoscopist to position snare near the needle.
9. Thread guidewire through needle into the stomach, allowing endoscopist to snare the guidewire. The needle can be removed.
10. Once guidewire is secured, it is pulled out of the mouth along with the scope.
The guidewire now passes through the abdominal wall into the stomach, then proximally out the mouth.
11. The endoscopist will secure the tapered end of the PEG tube to the proximal end of the guidewire.
12. The guidewire should be pulled away from the abdominal wall, which will gradually pull the PEG tube into position in the stomach up against the anterior abdominal wall.
13. A securing external bolster device can be fitted against the skin to keep the tube in position.
14. The endoscopist should visually confirm that the PEG balloon/internal bolster is adequately positioned (snug but not tight).

What are complications of PEG placement?

Wound infection
Bleeding
Peritonitis / Leak
Bowel perforation (Transilluminate!)

What is a PEGJ?

Allows for postpyloric access by passing a 9-12F tube through an existing PEG via endoscopic or fluoroscopic guidance.

Are systemic prophylactic antibiotics recommended for PEG placement?

Yes, there is Level 1 evidence that they decrease peristomal infection rates (Cochrane review)

How long is it recommended that a new PEG remain in situ before it is changed or replaced to a button?

6 weeks

What are surgical options for enteral access?

Gastrostomy
Jejunostomy

Can be performed open or laparoscopic, depending on ability and situation.

What is a Stamm Gastrostomy?

A series of opposing inner and outer purse-string sutures are used to secure a Foley catheter that has been passed through the anterior abdominal wall into the stomach. The sutures are then secured to the anterior abdominal wall, ensuring that the stomach is pexied in place.

What is a Witzel Jejunostomy?

After placement of a purse-string suture around a red rubber catheter that has been introduced into the jejunum, a seromuscular tunnel is sewn around the catheter using interrupted Lembert stitches for about 5cm. The catheter is then fixed to the abdominal wall. This can be performed longitudinally or transversely.

What is a Needle-Catheter Jejunostomy?

Utilizes a 6Fr catheter that is tunneled in the seromuscular space of the intestinal wall before it enters the intestinal lumen.

What are indications for surgical jejunostomy?

Patients undergoing major abdominal surgery where prolonged ileus or recovery is expected, or patients who are malnourished, hypermetabolic, septic, or may be undergoing postoperative chemotherapy or radiotherapy and requiring additional nutritional support.

What is the only absolute contraindication for a jejunostomy or postpyloric feeding?

Distal obstruction

Patients with pancreatitis can receive postpyloric feeds!

What is the caloric density of most isotonic enteral formulas?

1.0 kcal/ml

Why do some formulas contain fiber?

Fiber increases intestinal transit time
Fiber stimulates pancreatic lipase activity
Soluble fiber binds bile acid and cholesterols
Soluble fiber is metabolized by bacteria into short-chain fatty acids

Why should we care about short-chain fatty acids?

It is the primary fuel for the colonocyte!

What do immune-enhancing formulas often contain?

glutamine
arginine
branched-chain amino acids
omega3 fatty acids

They cost more, but have uncertain benefit!

Why do we care about glutamine?

It is the primary fuel for the enterocyte!
Lymphocytes and macrophages also love glutamine...
It is a precursor to glutathione (cellular anti-oxidant)

Why do we care about arginine?

It has a role in up-regulating immune function and promoting wound healing.
It is a substrate for nitric oxide synthase.
It affects anabolic hormone release including growth hormone, glucagon, prolactin, and insulin.

Why do we care about omega-3 fatty acids?

They decrease the inflammatory response (i.e. prostaglandins)

What is the caloric density of fluid-restriction formulas?

1.5-2.0 kcal/ml

What is the content of elemental formulas?

Predigested nutrients

These are higher in osmolality, but considered in situations such as malabsorption, gut impairment, and pancreatitis.

What is bolus feeding?

Delivering 200-500ml of formula over a short amount of time (i.e. 5 minutes).

This is the most physiologic, and typically only into the stomach.

What is intermittent feeding?

Infusing a volume delivered by gravity drip over 20-30 minutes.

What is continuous feeding?

Enteral delivery using an infusion pump, typically over 12-24 hours.
Usually increased by 10-25ml/hr every 4+ hours to a desired goal rate.

Required for postpyloric feeds.

What are potential nasty complications of enteral feeding in the setting of global hypoperfusion?

pneumatosis intestinalis and small bowel necrosis

Delay enteral nutrition until adequate resuscitation has been acheived!

What is "trophic" feeding?

Using enteral nutrition to complement parenteral nutrition, by administering enough as tolerated to stimulate intestinal trophism, while providing primary nutritional support via TPN.
Used in patients who cannot tolerate full enteral nutrition.

Late... SG

Sources:
Schwartz' Principles of Surgery, 8th ed.
O'Leary's Physiologic Basis of Surgery, 3rd ed.
Scott-Connor's The SAGES Manual: Fundamentals of Laparoscopy and GI Endoscopy (1999)
Lipp A, Lusardi G. Systemic antimicrobial prophylaxis for percutaneous endoscopic gastrostomy. Cochrane Database of Systematic Reviews 2006, 4 :CD005571.
Tapia J, Murguia R, Garcia G, de Los Monteros PE, Onate E. Jejunostomy: Techniques, Indications, and Complications. World J Surg 1999; 23: 596-602.