How to Monitor for Enteral Feeding

The quality of patient care advances in parallel with our ability to monitor, recognize, and promptly intervene to reverse system dysfunction. Patients often are unable to receive full nutrition because the gastrointestinal (GI) tract is, or may be, impaired. We present a simple, practical approach to safely extend the benefits of enteral nutrition. This regimen continuously monitors GI function, automatically restricting jejunal inflow to match sluggish peristaltic outflow.

It is common practice to feed patients through a tube inserted directly into the stomach, which increases the danger of regurgitation and aspiration of gastric contents. The current trend is toward a more distal feeding site, the jejunum, to reduce this risk.

Peristalsis distal to the duodenum is resistant to spontaneous reversal. However, this physiologic feature is a "double-edged sword" that all too often jeopardizes rather than protects the patient.

The proximal intestine is unique, able to directly avail itself of intraluminal nutrients. Feedings normally stimulate the responsive jejunum. These factors contribute to its own functional recovery, but only when the feeding rate is tolerated.

Patients with compromised gut function may barely be able to propel and resorb their own copious digestive juices. With feedings and swallowed air superimposed upon secretions, total flow into the jejunum may transiently exceed spontaneous outflow from this feeding catheter site. Disruptive (even lethal) autonomic reflexes can develop in response to this local imbalance before we can recognize and respond to the reversible iatrogenic complication.

Excess feedings accumulate in close proximity to the catheter. The stagnation is sensed, triggering vagal reflexes that further slow already-sluggish intestinal motility. This foodstuff, in a pool of digestive juices, breaks down to osmotically active moieties (e.g. complex carbohydrates Æ glucose). Imbibed fluid further swells the residual volume, initiating a rapidly progressive vicious cycle.

Even slightly excess jejunal feeding may quickly cause severe local effects, cascading to generalized abdominal distention, malaise, immobility, and respiratory embarrassment. Cardiovascular collapse can be the most serious consequence of such acute intestinal distention, probably responsible for the reported 1 in 1,000 incidence of lethal bowel necrosis for jejunally fed patients.1

The minimally increased local volume of early stagnation must be appreciated even before the concomitant pressure rise is detectable. The total jejunal inflow must be continuously monitored and adjusted to match the compromised gut's ability to accommodate the load further downstream. Simultaneous exclusion of swallowed air would further protect fragile motility and absorption.2

Our regimen automatically aspirates the jejunal feeding catheter into a small plastic burette. All air bubbles are vented efficiently, the residual liquid volume is assessed, and the degassed fluid is returned by gravity within each 60-second cycle. No feedings or juices are removed permanently unless they accumulate at the feeding site. Only then are those several milliliters of excess liquid selectively discarded.

Methods

1. Apparatus

The disposable "Enteral Feeding Monitor/Manager" (Moss Medical Products, Inc, White Plains, NY) superficially resembles a gravity feeding set, whose "drip chamber" is a conical plastic burette with a floating ball check valve (Figure 1). This unit has an adjustable overflow level, with the default setting at 20 mL.

Gastrointestinal function Monitor/Manager: off suction.

Figure 1.

Gastrointestinal function Monitor/Manager: off suction.

Figure 1.

Gastrointestinal function Monitor/Manager: off suction.

Close modal

The intermittent suction is applied to the Enteral Feeding Monitor/Manager through a disposable canister (e.g. Bemis Manufacturing Co, Sheboygan Falls, WI), into which is aspirated all air and any excess overflow liquid.

Most hospital sources of intermittent suction cannot be user programmed for the requisite 1-minute cycles of 30 seconds "on" and 30 seconds "off," although some can be so adjusted internally by the hospital's biomedical technician. To utilize standard hospital continuous suction, we found Intermittent Suction Regulator Model 7702L (Boehringer Laboratories, Inc, Norristown, PA) to be a highly stable unit whose factory default cycling is appropriate for this regimen. Portable Suction (Models 306 and 326, Impact Instrumentation, West Caldwell, NJ) are self-contained sources of suitable user-programmable intermittent suction that we have used for our regimen.

2. Procedure

A standard single-lumen jejunal feeding tube (J-tube) is placed via the nasal, transgastric, or direct route. A feeding pump continuously delivers an elemental diet into the J-tube at the full desired rate.

The Enteral Feeding Monitor/Manager is positioned sufficiently above the patient (3 to 4 feet) to empty by gravity flow within 30 seconds into the side arm of the J-tube. The burette's overflow tube is connected to the inflow port of the disposable suction canister.

Intermittent suction (programmed for 30-second cycles each of "on" and "off") is connected to the suction port of the canister. As the elevated Enteral Feeding Monitor/Manager is subjected to intermittent suction, it alternately fills from below with jejunal aspirate, and then returns the degassed liquid by gravity flow.

Gastrointestinal function Monitor/Manager: excess jejunal fluid removed.

Figure 3.

Gastrointestinal function Monitor/Manager: excess jejunal fluid removed.

Figure 3.

Gastrointestinal function Monitor/Manager: excess jejunal fluid removed.

Close modal

The suction intensity is adjusted to lift all jejunal residual liquid and air bubbles into the chamber within the 30 seconds that suction is applied (Figure 2). The chamber's liquid content returns to the jejunum under gravity during the 30-seconds "off" period.

Gastrointestinal function Monitor/Manager: no excess residual, no overflow.

Figure 2.

Gastrointestinal function Monitor/Manager: no excess residual, no overflow.

Figure 2.

Gastrointestinal function Monitor/Manager: no excess residual, no overflow.

Close modal

Simply noting that the fluid column fully fluctuates each minute is adequate confirmation that the system is functioning properly.

Discussion

Utilizing current clinical approaches, physicians have great difficulty titrating jejunal feeding to fully utilize, but not exceed, impaired GI function. We do not recognize intolerance until excess foodstuff leads to signs of physiologic derangement, such as abdominal distention, nausea, or vomiting. By then, the mismatch between feeding rate and inadequate GI function will have wreaked clinically significant havoc. Aspiration may result despite (or because of) jejunal delivery.

Physicians at Memorial-Sloan Kettering Cancer Center conducted a prospective, controlled study of conventional postoperative jejunal feeding for 100 paired cancer patients.3 They concluded that their attempts at feeding impeded, rather than improved, postoperative recovery. A similar study in Ottawa4 reached the same conclusion. This latter group specifically observed that early postoperative feeding further impaired respiratory mechanics and patient mobility, almost certainly because of increased abdominal distention.

Miedema and his coworkers5 at the University of Missouri monitored intraluminal jejunal pressure and reported that feeding intolerance does correlate with increased pressure. However, this approach was not a practical "early-warning system." The compliant jejunum normally is nearly empty. Measurable pressure elevation is a late development in the course of progressive GI dysfunction. They are repeating their clinical study but are employing our regimen to monitor and respond to jejunal volume, rather than pressure.

"Checking for residual" is a time-honored procedure to assess the adequacy of GI function for tube-fed patients, but repeated manual testing is too labor intensive for practical application. The described automated regimen performs this function every 60 seconds, without requiring additional nursing effort. Any standard single-bore jejunal tube can serve dual functions. At 30-second intervals, the full channel is alternately dedicated to either monitoring or feeding.

The procedure is inherently safe, and verification of proper function simply requires a brief glance at the oscillating fluid column. Although J-tube clogging is always a concern, the repeated flushing with self-cleansing digestive juices and the use of elemental diet appear to ensure patency. (The proteins of polymeric diets are avoided while monitoring, as they curdle on contact with digestive juices.)

Suction actually experienced within the intestine is markedly attenuated from that applied. The hydrostatic fluid column between the elevated chamber and the patient effectively reduces the jejunal vacuum by approximately 100 mm Hg.

Nothing is delivered in net fashion to the patient by the Enteral Feeding Monitor/ Manager. Gravity periodically returns several milliliters of degassed enteral fluids that had been aspirated from the same site 30 seconds earlier.

In contrast with gastric aspiration, swallowed air could be removed efficiently within the close confines of the tubular esophagus.6 The esophageal suction orifices were prone to clogging by swallowed phlegm, and they required heroic nursing efforts to maintain patency. This requisite attention was available in our exceptionally well-staffed Clinical Research Center, but the difficulty precluded wider adoption of this earlier regimen.

However, over 40 years ago we reported that just adding efficient exclusion of swallowed air by esophageal aspiration immediately following operation resulted in clinically normal gastric emptying and absorption of elemental diet. Positive nitrogen balances were achieved uniformly within hours of major bowel resection and reanastomosis.2 Postoperative x-ray film motility contrast studies confirmed the preservation and utilization of GI function.7 This earlier protein synthesis was shown to reflect accelerated wound healing and antibody production.8

This current regimen was used in the intensive care units of community hospitals in the Albany, NY, area for three patients following thoraco-abdominal resection for esophageal carcinoma. Their GI continuity was reestablished with intrathoracic positioning of the stomach. A standard jejunostomy feeding tube was inserted for immediate postoperative feeding of approximately 1,000 kcal of elemental diet.

The J-tube aspirate volume most often was less than 10 mL. Whenever it reached the 20-mL overflow level, any excess was removed automatically. The total daily overflow was approximately 100 to 200 mL/d of net fluid removal into the suction canister.

The initial postoperative GI dysfunction appeared to resolve rapidly with this procedure, comparable to that reported with esophageal removal of swallowed air following our earliest regimen. No patient developed distention, sensation of fullness, or nausea. The abdomen appeared devoid of gas by percussion. Feedings were fully absorbed, despite the absence of bowel sounds, indicating motility without liquid-air interaction. This is consistent with virtual "degassing" of the GI tract, as noted decades ago. Normal bowel sounds appeared immediately on continued J-tube feeding after cessation of simultaneous aspiration and monitoring.

No complication was associated with this regimen, and the increased attention was deemed insignificant by the nursing staff. The formal studies under way will quantify the possible clinical benefits.

Summary

A simple and inherently safe Enteral Feeding Monitor/Manager is described for use with standard, single-lumen jejunal tubes. No feedings or GI fluids are removed permanently unless they accumulate adjacent to the catheter. Only such momentary excess is removed promptly, before local distention can develop.

The full bore automatically alternates between 30 seconds on suction and 30 seconds for return of the aspirate. Each minute, the removed air bubbles are vented, the residual jejunal volume is measured, and the degassed fluid is returned by gravity.

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Source: https://meridian.allenpress.com/bit/article/39/2/151/198882/Enteral-Feeding-Monitor-Manager

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