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Blind bedside placement of enteric feeding tubes
Blind Bedside Placement of Enteric Feeding Tubes G a r y P. Z a l o g a , M D
Early enteral nutrition, especially with immune-modulating formulas, has been shown to improve outcomes in critically ill patients. Early nutrient delivery supports organ function and recovery from illness and modulates inflammation and organ injury. Misconceptions regarding gastrointestinal function and alterations in gastrointestinal function during illness impede early enteral feeding. Bowel sounds, elevated gastric residuals, failure to pass flatus, and diarrhea are not contraindications to enteral nutritional support. Most critically ill patients can be fed into the stomach with minimal risk for aspiration. Promotility agents aid in gastric feeding. When gastric feeding is not possible, most patients will tolerate small intestinal feeding. Because spontaneous passage of feeding tubes into the small bowel in critically ill patients is rare, most feeding tubes can be positioned into the small bowel with blind bedside placement by the clinician (ie, physician, nurse, nutritionist). When such procedures are not successful, x-ray guided or endoscopic placement of feeding tubes into the small bowel are recommended. Occasionally, small bowel feeding tubes will need to be placed surgically. Copyright 9 2001 by W.B. Saunders Company
E
nteral nutrition is the preferred route of nutritional support in all groups of patients. Enteral feeding is superior to parenteral feeding. In addition, recent reviews and meta-analyses indicate that early enteral administration of nutrients improves outcome compared with delayed enteral feeding. 1,2 Outcome in these analyses was defined as complications, infections, length of hospitalization, costs, or mortality. Current analyses also indicate that use of nutrients with immune support and inflammatory control are superior to standard enteral diets. 3-5 Thus, early institution of enteral nutrition represents an important therapy for optimizing care and improving outcome. There are a number of barriers that delay enteral nutritional support. 6"s These include lack of appreciation for the benefit of early enteral nutrition, misconceptions regarding gastrointestinal function and evaluation, and the inability to place feeding tubes in an expeditious and inexpensive manner. This article reviews these issues.
Benefits of Early Enteral Nutrition Enteral nutrition supplies a large variety of nutrients that are important for the body's response to illness, healing, prevention of cell injury, and recovery from illness and injury. Although
From the Department of Critical Care Medicine, Suburban Hospital, Bethesda, MD. Address reprint requests to Gary P. Zaloga, MD, Director of Research, Intensimed, 7309 Bannockburn Ridge Ct, Bethesda, MD, 20817. Copyright 9 2001 by W.B. Saunders Company 1096-2863/01/0301-0003535.00/0 doi:10.1053/tgie.2001.19907
the body has evolved complex mechanisms for storing and mobilizing nutrients, these mechanisms are not as effective as exogenous nutrient intake. Exogenous intake provides larger amounts and greater variety of nutrients than does endogenous mobilization (ie, amino acids, lipids, electrolytes, trace elements, vitamins, antioxidants). In addition, many patients are malnourished or have organ dysfunction/failure before hospitalization and cannot mobilize adequate quantities of some nutrients (ie, arginine, zinc, magnesium, glutathione, vitamin E). Early institution of enteral feeding after injury is associated with improved organ function (Table 1). The organs most affected by early enteral feeding are the gastrointestinal tract, liver, kidneys, and immune system. Experimental data indicate that enteral feeding can prevent organ dysfunction in various models of critical illness (ie, shock, burn, hemorrhage, sepsis). Improved organ function (especially immune function) is associated with decreased infections, complications, length of stay, and cost 1,2 in humans with critical illness. Based on the benefits of early enteral feeding, many clinicians begin enteral nutrition (ie, metabolic resuscitation) immediately after cardiopulmonary resuscitation of the patient. This process is termed the ABCD (airway, breathing, circulation, diet) approach to resuscitation.
Nutritional Misconceptions Misconceptions regarding gastrointestinal tract function are major causes of delayed enteral feeding. 6,s The gastrointestinal tract is composed of the upper tract (mouth and esophagus), stomach, small intestine, colon, and rectum. Most patients with severe illness will not be capable of ingesting adequate nutrition safely (ie, oral route). Altered mentation and dysregulated swallowing impair intake and place patients at risk for aspiration. Thus, most critically ill patients will require use of feeding tubes for delivery of enteral nutrients. After critical illness, many investigators report a decrease in gastric emptying and colonic motility. However, most studies indicate that small intestinal motility remains relatively intact and adequate for enteral feeding. Importantly, the effects of illness on gastric emptying appear to be related to timing of feeding after illness and the severity of the underlying disease. Gastric feeding can be accomplished in most patients when feeding is begun within hours of illness or injury. Delaying feeding for many hours to days results in progressive impairment of gastric emptying and may prevent use of the gastric route. These patients frequently require placement of small bowel feeding tubes for nutrient delivery. Colonic motility rarely causes problems with nutritional support. Although bowel movements are uncommon for the first few days (ie, 2 to 4 days) after onset of critical illness, few patients develop clinically significant bowel distention. Feeding fully absorbable enteral formulas (ie, nonfiber formulas) is
Techniques in Gastrointestinal Endoscopy, Vol 3, No 1 (January), 2001: pp 9-15
9
T A B L E 1. Benefits of Enteral Nutrients on Organ Function
Organ
Nutrient Effects
Gastrointestinal tract
Improvedmotility Improved mass Improved absorption Decreased permeability Improved blood flow Improved mucous layer Improved immunity Decreased bacterial adherence Increased IgA secretion Maintenance of lymphoid tissue Decreased bacterial/yeast/toxin translocation Increased mass Improved function Increased blood flow Improved B and T cell function Improved phagocytosis Improved bacterial/fungal killing Improved IgA secretion (gut) Improved lymphoid tissue (gut) Decreased infections Improved healing Improved Improved blood flow Improved recovery from acute renal failure
Liver Immune
Wound Protein synthesis Renal
well tolerated and the formula is usually completely absorbed before it enters the colon. Although most clinicians listen for bowel sounds before they initiate enteral nutrition, few listen properly and even fewer understand the meaning of bowel sounds. Bowel sounds are produced when air is propelled through the intestines (small and large) by peristalsis. There is a large range for bowel sounds in healthy individuals. One may hear anywhere from a few per minute to almost continuous sounds. Proper listening for the absence of bowel sounds requires 3 to 4 minutes in each of the 4 abdominal quadrants. Few clinicians ever listen for 12 to 16 minutes. Bowel sounds should be described as present or absent and not hypo- or hyperactive (because of the wide range of sounds normally). Bowel sounds require the presence of air in the gastrointestinal tract and will be decreased in patients with impaired swallowing and in those who receive nasogastric suctioning. Because bowel sounds are dependent on the quantity of air in the gut and gastric emptying, they are poor indicators of bowel peristalsis and feeding tolerance. Hearing many sounds suggests that gastric emptying is adequate for feeding. However, hearing few sounds has little predictive power for determining tolerance to feeding. Bowel sounds can easily be elicited by injecting air into the stomach via a nasogastric tube. We do not recommend the routine evaluation of bowel sounds. Instead, assessment of the abdomen by clinical examination and evaluation of gastric residual volume are better predictors of enteral feeding tolerance. Diarrhea is not a contraindication for enteral feeding. Most diarrhea which develops in hospitalized patients without short gut syndrome results from prosecretory states and not from the enteral feeding. 9 A healthy gut can tolerate standard nutritional formula feeding rates up to 275 mlJhr. 9 Infection with release of cytokines and toxins stimulates gut secretory activity. The diarrhea usually resolves with control of the underlying disease state and most patients tolerate partial to full enteral feeding. Diarrhea can be minimized by eliminating osmotic agents (ie, magnesium), treating infections, minimizing use of unneeded antibiotics that contribute to bacterial overgrowth or selection, 10
use of fiber formulas, and use of antisecretory and antimotility agents (ie, opiates, bismuth subsalicylate). The incidence of diarrhea reported in intensive care unit (ICU) patients varies greatly. Much of the difference can be explained by differences in the definition used to define diarrhea. ~~ Some consider diarrhea to be present in patients with multiple bowel movements (even if they are formed and of low volume). Others define diarrhea as present in any patient with liquid stool. Many critically ill patients have rectal incontinence and one should not define diarrhea as multiple small volume formed bowel movements per day. Montejo et al 7 defined diarrhea as 5 or more liquid stools in a 24 hour period or an estimated volume of 2,000 mL or greater per day. Fourteen percent of 400 patients had at least 1 episode of diarrhea. However, the diarrhea was short lived in most patients (ie, lasting less than 1 day) and persisted for more than 3 days in only 3% of patients. Diarrhea resulted in withdrawal of enteral feeding in only 3% of patients. We define diarrhea as 3 or more liquid bowel movements per day or 350 mL or more of liquid stool per day. The incidence of diarrhea in our medical ICU patients is approximately 5% and usually subsides within 3 days, despite continuation of enteral feeding. Some clinicians do not feed their patients until the patients admit to or are noted to pass flatus. We do not favor this practice. Flatus is present in most patients even if patients and nursing staff are not aware of it. In addition, fully absorbable formulas do not require colonic function. Our practice is to feed patients with nonfiber formulas until they have a bowel movement. Fiber can be given once bowel movements resume. We also follow clinical examination of the abdomen. Extensive clinical experience indicates that these patients tolerate early enteral feeding.
Gastric Residual Volume Gastric residual volume has been used by clinicians for many years as a parameter for assessing tolerance of gastric feeding and risk for aspiration. However, little data in the literature support the use of gastric residuals for these purposes. Controlled trials have not been performed to establish the validity, range, and limitations of gastric residual monitoring. This is interesting because physicians, nurses, and nutritionists frequently stop enteral feedings based on gastric residual volume, regardless of clinical status. Although aspiration is increased by large gastric residual volumes and incompetent lower esophageal sphincter tone, there is no direct relationship between gastric residuals and aspiration. Few studies have evaluated gastric residuals in healthy, bedridden, and critically ill patients. Gastric residuals also vary with the time after a meal. McClave et al H studied gastric residual volume during 8 hours (at bedrest) of total enteral nutrition (65 to 175 mL/hr) in 20 volunteers, 8 stable patients with gastrostomy tubes, and 10 critically ill patients. None of the subjects was intolerant to the feeds and none of the patients sustained obvious aspiration. Fasting residual volumes in the volunteers and critically ill patients were close to zero. During feeding, 2.4% of gastric residuals in the volunteers were above 150 mL; 13% were above 150 mL in the critically ill patients; none of the residuals were greater than 150 mL in the gastrostomy group. Findings on physical examination failed to predict gastric residual volume. McClave et a111 suggested that gastric residuals of 200 mL obtained from a nasogastric tube should GARY P. ZALOGA
raise concern about intolerance. Adam and Batson 6 evaluated 193 critically ill patients. Average daily gastric aspirates during gastric feeding were 200 to 220 mL during the first few days of feeding and decreased to approximately 100 mL during the remainder of the patients' ICU stay. We evaluated fasting (admission gastric residual volumes) and gastric residual volumes during enteral feeding (every 4 to 6 hours for 72 hours) in 100 medical ICU patients (Table 2). Fasting gastric residuals were obtained with an oral or nasogastric tube as the patient lay in the supine position with the head elevated at 30 ~ on admission to the medical ICU. Thirty percent were greater than 100 mL, 15% were greater than 150 mL, and 6% were greater than 200 mL. Interestingly, gastric residual volumes decreased with gastric feeding (100 mL every 2 hours) and only 8% of fed patients had gastric residual volumes greater than 150 mL. We found no relationship between gastric residual volume and aspiration in these patients. We also compared gastric residual volume and risk for aspiration in 18 critically ill patients randomized to bolus feeding (100 mL every 2 hours) or continuous feeding (50 mL/hr). 12 There was no evidence for aspiration in any of the patients. Both groups received similar quantities of nutrition that met 85% to 90% of their nutritional goals over 72 hours of study. Gastric residual volumes (Table 3) were similar between groups and decreased with duration of gastric feeding. In summary, morning gastric residual volumes in ambulatory healthy individuals who fast after midnight are close to zero. Normal gastric residuals in fasting supine critically ill patients are usually under 150 mL, with an occasional patient having a residual of 150 to 250 m L These patients usually tolerate gastric feeding without problems, and gastric residuals may decrease in patients being enterally fed. During enteral feeding, we use a gastric residual volume of 150 mL as an indicator of possible feeding intolerance.
Gastric Feeding Most critically ill patients require the use of feeding tubes for nutrient delivery. These tubes can be placed into the stomach or small intestine. Although it was once believed that critically ill patients would not tolerate gastric feeding because of gastroparesis and the risk of aspiration, recent experience suggests that gastric feeding is usually well tolerated in most patients. With aggressive resuscitation, limited use of antimotility agents (ie, opiates), use of promotility agents, and institution of very early feeding, most patients will tolerate gastric nutritional support. This does not mean that gastric emptying is normal in all the patients. However, it does indicate that the decrease in gastric emptying experienced by most ICU patients allows for adequate gastric delivery of nutrients. In a review of 300 patients in our medical intensive care unit (Table 4), we found that 95% were fed within 12 to 24 hours of TABLE 2. Gastric Residual Volumes in 100 Medical ICU Patients Gastric Residual
Fasting
During Gastric
Volume (mL)*
(Admission)
Feeding
>200 >150 > 100
6 15 30
2 8 20
TABLE 3. Gastric Residual Volumes (GRV) During Bolus and Continuous Gastric Feeding in 18 Medical ICU Patients
Day
Bolus Maximal GRV (mL)
Bolus Average GRV (mL)
Continuous Maximal GRV (mL)
Continuous Average GRV (mL)
1 2 3
88 + 4 6 52• 45 + 2 4
28_+13 18_+9 18_+11
92_+41 35_+18 12_+4"
28+13 15+-8 7-+2
* P < .05 compared with bolus.
admission and tolerated gastric feeding. Only 5% required placement of small bowel feeding tubes or parenteral nutrition. This evaluation included patients with ARDS (acute respiratory distress syndrome), respiratory failure secondary to chronic obstructive pulmonary disease or asthma, pneumonia, intracranial bleeds and ischemic strokes, renal failure, shock (sepsis, hemorrhagic, cardiogenic), gastrointestinal bleeding, liver failure, status epilepticus, and malignancies. Feeding tubes were placed into the stomach by the bedside nurse. Gastric residuals were monitored every 2 to 4 hours. Most nutrition was delivered by the bolus method. A recent evaluation of 40 patients in our ICU fed within 12 to 24 hours of ICU admission indicated that none of the patients developed clinically significant aspiration pneumonia. Aspiration pneumonia was defined as a new pulmonary infiltrate that occurs in a patient who is receiving gastric nutrition. All patients were fed with the head of the bed elevated approximately 30 ~ None of these patients had deterioration in oxygenation, defined as the ratio of PO 2 to inspired oxygen concentration (ie, PO~/FIO 2 ratio). These data do not exclude aspiration but suggest that the risk is low. Interestingly, evaluation of patients with aspiration pneumonia admitted to the ICU failed to reveal an association between gastric tube feeding and aspiration. An occasional patient was admitted with aspiration pneumonia after dislodgment of the feeding tube during continuous feeding. Montejo et aF evaluated 400 consecutive patients admitted to the ICU and receiving enteral feeding. Ninety-one percent received gastric feeds. The incidence of aspiration pneumonia was reported to be 1.5%.
Gastrointestinal Motility Agents A number of agents administered to critically ill patients can interfere with gastrointestinal motility. Opiates are the most common. However, decreased motility can also be seen with some neuromuscular blocking agents (caused by their anticholinergic effects) and other anticholinergic agents. We minimize the use of opiates for pain control. Our primary agent for sedation/analgesia is propofol. Although touted as a sedative agent,
TABLE 4. Route of Early Nutritional Support in 300 Medical ICU Patients Route*
Number (%)
Gastric
185 (95%) 10 (3%) 5 (2%)
Small bowel Parenteral nutrition
* Excludes patients admitted on parenteral nutrition (ie, short gut * Obtained in the supine position, head of bed elevated to 30 ~ ENTERIC FEEDING TUBES
syndrome). 11
at high doses propofol produces excellent analgesia. This agent does not decrease gastric emptying or gut motility. When gastric residuals volumes are consistently greater than 150 to 200 mL, we administer promotility agents. The 3 agents available on the market are erythrolnycin (100 to 250 mg every 6 hours), metoclopramide (10 mg every 6 hours), and cisapride. Cisapride has numerous toxic effects, especially on the cardiovascular system. It is being withdrawn from the market and should not be used. It is no more effective than the other agents. A number of studies of the promotility effects of the above agents have been conducted in critically ill patients. 13 Three prospective randomized controlled trials evaluated the effects of metoclopramide on gastric emptying in critically ill patients. ~3 Two of the 3 trials (using acetaminophen absorption and feeding tube migration) reported increased emptying. Four studies evaluated the effect of erythromycin on gastric emptying. All reported increased emptying (using acetaminophen absorption, gastric residuals, and feeding tube migration). We favor the use of erythromycin over metoclopramide. Interestingly, we have treated a few patients who continued to have large gastric residuals despite erythromycin who improved when metoclopramide was added to the erythromycin. We discontinue these agents periodically (ie, every 3 to 5 days) as the patient improves to determine if treatment with the agents is still required.
Benefits of Postpyloric Feeding The primary indication for postpyloric feeding is the maintenance of nutritional intake in patients intolerant of gastric feeding. Most patients with high gastric residuals and clinically significant gastroesophageal reflux can be administered adequate nutritional support via the postpyloric route. Many clinicians believe that postpyloric feeding decreases the risk for aspiration. However, a decrease has not been proven in controlled studies. ~4q7 Kearns et al ~4 investigated the incidence of ventilator-associated pneumonia in a small group (n = 44) of patients randomized to gastric versus small intestinal feeding. The small bowel feeding group did not receive gastric decompression or monitoring of gastric residuals. The incidence of ventilator-associated pnemnonia was similar in both groups (4/21 v 3/23). However, nutrient delivery was better in the small intestinal feeding group. Two other randomized trials of gastric versus small bowel feeding failed to document decreased aspiration in the small bowel fed patients. ~5,16 However, nutrient delivery was improved with small bowel feeding. ~5,16 Unfortunately, these studies had small numbers of patients and were underpowered to show clinically significant differences in the incidence of aspiration pneumonia. Although not clearly proven in prospective randomized trials, we and others 18,19 believe that small bowel feeding (especially when combined with gastric decompression) minimizes aspiration in the subset of patients at high risk for aspiration or with significant gastroesophageal reflux. In fact, the American Thoracic Society's consensus statement concludes that distal enteral feeding sites probably decreases the risk of nosocomial pneulnonia. 19
Spontaneous Transpyloric Passage of Feeding Tubes In a previous study of mixed medical-surgical critically ill patients, 2~ we found that only 5% of small bore feeding tubes passed spontaneously into the small bowel over 3 days. This
12
rate was not improved with metoclopramide. Silk et al 2~ reported a spontaneous passage rate over an average of 4 to 5 days for small bore feeding tubes of 0% to 4%. The rate was 0% (0/76) for unweighted feeding tubes and 4% (3/79) for weighted tubes. Rees et a122 evaluated spontaneous small bore feeding tube passage into the small bowel in general ward and intensive care unit patients. A total of 69 patients were studied. Spontaneous transpyloric passage of the tubes occurred in approximately one third of the patients. Importantly, a third of the patients in this study were mobile. Posniak et a123 reported a 13% passage rate and Marian et a124 reported a 15% spontaneous passage rate for feeding tubes. Thus, a small percentage of small bore feeding tubes pass spontaneously into the small bowel in critically ill patients. Early initiation of enteral feeding in patients intolerant of gastric feeding requires active placement of the feeding tubes into the small bowel.
Placement of Small Bowel Feeding Tubes When gastric emptying fails to improve with promotility agents or the patient has documented pulmonary aspiration, we place small bowel feeding robes. Most of the time, these tubes can be placed into the small bowel at the bedside. 25,26 In our initial study in 1991,25 we attempted 231 bedside small bowel feeding tube placements using the "corkscrew technique" and were successful in 213 (92%) of the placements. Seven (3%) of the tubes were in the first part of the duodenum, 57 (25%) in the second portion of the duodenum, 109 (47%) in the third portion of the duodenum, and 40 (17%) were in the proximal jejunum. The average time for placement of the tubes in the 1991 study was 40 minutes. However, with additional experience the time was reduced to 10 to 20 minutes. This technique has been used by other clinicians and found to be successful in 75% to 90% of attempts. 27 In our initial study, we emptied the stomach before placing the feeding tubes. However, because gastric distension is a stimulus for gastric emptying, others report excellent success in placing small bowel feeding tubes with use of air insufflation. 28-3~We incorporated air insufflation along with the "corkscrew technique" and were able to place over 95% of small bowel feeding tubes in approximately 5 to 15 minutes. Our current technique for placement of bedside small bowel feeding tubes involves placing the patient in the supine position and rotated 30 ~ to 40 ~ onto the right side (right side down). The stomach is emptied of its contents using a oral or nasogastric tube. The pH of the contents is checked using pH paper, and the contents are observed for bile. Then the oral or nasogastric tube is removed. A 10F to 12F weighted feeding tube containing a wire stylet is placed into the stomach. The stylet is removed, the tip is bent at a 30 ~ angle approximately 2 cm from the distal end, and it is reinserted into the feeding tube (Fig 1). The bend allows for the tip of the tube to cover a greater surface area during rotation and helps the tip to "hook" the pyloric outlet during tube advancement. A 60 mL syringe is used to pump 10 mL/kg of air into the stomach (in adults). After air insufilation, the feeding tube is slowly rotated and advanced in short 4 to 5 cm bursts until it is inserted the appropriate length compatible with a small bowel location. The tube is allowed to slowly advance and is not forced forward. Advancement can be assisted by repeated injection of small volumes of air. The tube is taped in place and its position checked by aspiration. A change of pH from acidic (stomach) to basic or the appearance of bile (not found in the stomach) suggests small bowel placement. In GARY P. ZALOGA
addition, the inability to aspirate insufflated air suggests small bowel versus gastric placement. There is also a change in location and pitch of bowel sounds when moving from the stomach into the small bowel. Air insufflated into the stomach has a lower pitch, is heard best in the left upper quadrant, and does not radiate well to the right flank. Air insufflated into the small bowel is of higher pitch, best heard in the midline or right upper quadrant, and radiates well to the right flank. One can also check for small bowel position by placing a nasogastric tube and injecting blue dye through the small bowel tube. Failure of the dye to appear from aspiration of the gastric tube indicates small bowel location. If the position is uncertain, a radiograph can be obtained to determine tube position. We instructed a n u m b e r of nurses to perform this procedure at the bedside. In a prospective evaluation of 59 attempted small bowel placements, nurses were successful in placing 7"5%.26 The mean time for placement was 11 minutes. A few patients had minor complications but no patient had major complications. In a n u m b e r of institutions feeding tubes are being placed by nurses and other nutritional support personnel with good success. Welch 31 reported a study in which 79 nurses were certified in feeding tube placement and 90% of attempts successfully intubated the duodenum. Harrison et aP 2 reported a 99% success rate when feeding tubes were directed into the small bowel by bedside nurse practitioners in a pediatric ICU. Blind bedside placement of small bowel feeding tubes has been successful in the hands of m a n y clinicians. However, some have not achieved a high success rate, which may relate to training, experience in the technique, and the severity of underlying illness of patients. Thus, m a n y clinicians have sought bedside methods that can aid in placement of feeding tubes. These have included pH sensor guidance,33, 34 magnetic guidance, 35 sonographic guidance, 36 electromyographic guidance, 3r and fiberoptic scopes 3s through the feeding tubes. Gabriel et a135 used a hand-held magnet to maneuver a nasoenteral feeding tube containing a small magnet at its tip into the small bowel in critically ill patients. Forty-two intubations were performed in 35 patients and the investigators were successful in 88% (mean procedure time 15 minutes). This technique is being evaluated by other investigators. Preliminary reports indicate a lower success rate of about 50%. Grathwohl et aP s evaluated use of a videoscope attached to an angioscope that was placed through a 12F feeding tube. They were able to visualize enteric structures through the scope and were suc-
Fig 1. Bending of wire stylet for "corkscrew" technique.
ENTERICFEEDINGTUBES
I
RESUSCITATIONCOMPLETE I (Airway,Breathing,Circulation) I
I
PLACEOG/NG TUBE INTO STOMACH
I G R > 150ml
G R < 150ml
Empty Stomach Contents
I Begin Enteral Feeding I .., (ie. 100ml bolus Q
2hr)I
Discard
II I
CHECK GR EVERY 2 Hours (before next bolus)
GR~5OmI ~ i Continue Enteral Feeding
I
I
L
GR>150ml
! A0ent Be0'nPr~176l-(ie. erythromycin)
CHECK GR EVERY 2 Hours GR
.....
Increase Volume of Feeds (ie. 1 can every 4hrs); Increase GR Monitoring
Interval to Every 4 hrs.
50ml
"'
PromotilityAgentPlus Trial of ContinuousEnteralFeeds
(ie.50mi/hr)
or PlaceSmallBowelFeedingTube & RestartFeeds
Fig 2. Approach to early enteral feeding. cessful in placing all tubes into the small bowel in a small number of normal individuals and critically ill patients. Hernandez-Socorro et aP 6 used bedside ultrasound to guide feeding tubes into the small bowel in critically ill patients. The technique was successful in 85% (22/26) of patients in whom blind bedside small bowel placement failed. We have not found that pH sensor guided tubes offer much over use of intermittent pH assessment using pH paper. Although they are easier to use for evaluating pH changes, the cost of the tubes is much greater. Levy3r used electromyographic guidance to place postpyloric feeding tubes. This technology measures spontaneous electrical activity of the gut and can distinguish between gastric and small intestinal locations. Overall success rate was 92% with the technique. Further study of these techniques is required. It is important for this studies to consider cost-effectiveness of the techniques. When bedside maneuvers are not successful, small bowel feeding tubes can be placed in most patients using x-ray guidance, 39 endoscopic guidance, 4~ or surgery. These methods are discussed in other articles in this issue.
13
Conclusions We use the ABCD approach to enteral feeding (Fig 2). After control of the airway, assessment and support of breathing, and support of the circulation, we begin diet resuscitation (ie, nutrient delivery). Delivery of nutrients is by feeding protocol (Fig 2). A number of studies indicate that nutrient delivery is improved when administration is directed by a feeding protocol. We minimize the use of antimotility agents such as opiates and neuromuscular blockers. Our primary sedative in intubated patients is propofol because of its minimal effects on gut motility. Whenever possible, patients are maintained with the head of the bed elevated at 20 ~ to 30 ~, to minimize the risk of aspiration. There are no reliable clinical tests for monitoring the patient for aspiration. The exact incidence of aspiration is unclear and has been reported to range from 0% to 50%. In addition, the number of patients with aspiration of formula who go on to develop pneumonia is also unknown. Some clinicians place blue dye in the nutritional formula. Appearance of dye in pulmonary secretions indicates that aspiration has occurred. However, this test lacks sensitivity. Others have used serial monitoring of tracheal glucose levels. The reliability of this test is also questioned. Aspiration does appear to be reduced by elevating the head of the bed.42,43 As discussed previously, there is no clear relationship between gastric residual volume and aspiration; however, most clinicians monitor gastric residuals and hold feeding when the residual is greater than 150 to 200 mL. Recent studies suggest that use of an orogastric or nasogastric tube does not increase the risk of aspiration above that of small bore feeding tubes. 44,45 Some have suggested that competence of the lower esophageal sphincter is actually increased by the presence of a tube across the esophageal junction. 46
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References 1. Zaloga GP: Early enteral nutritional support improves outcome. Hypothesis or fact? Crit Care Med 27:259-261, 1999 2. Kudsk KA, Minard G, Croce MA, et al: A randomized trial of isonitrogenous enteral diets after severe trauma. Ann Surg 224:531-543, 1996 3. Zaloga GP: Immune-enhancing diets. Where's the beef? Crit Care Med 26:1143-1146, 1998 4. Heys SD, Walker LG, Smith I, et al: Enteral nutritional supplementation with key nutrients in patients with critical illness and cancer: A meta-analysis of randomized controlled clinical trials. Ann Surg 229: 467-477, 1999 5. Beale RJ, Bryg DJ, Bihari DJ: Immunonutrition in the critically ill: A systematic review of clinical outcome. Crit Care Med 27:2799-2805, 1999 6. Adam S, Batson S: A study of problems associated with the delivery of enteral feed in critically ill patients in five ICUs in the UK. Intensive Care Medicine 23:261-266, 1997 7. Montejo JC, and the Nutritional and Metabolic Working Group of the Spanish Society of Intensive Care Medicine: Enteral nutrition-related gastrointestinal complications in critically ill patients: A multicenter study. Crit Care Med 27:1447-1453, 1999 8. Heyland D, Cook DJ, Winder B, et al: Enteral nutrition in the critically ill patient: A prospective survey. Crit Care Med 23:1055-1060, 1995 9. Kandil HE, Oper FH, Switzer BR, et al: Marked resistance of normal subjects to tube-feeding-induced diarrhea: The role of magnesium. Am J Clin Nutr 57:73-80, 1993 10. Zimmaro D, Guenter PA, Gregg R: Defining and reporting diarrhea in tube-fed patients: What a mess! Am J Clin Nutr 55:753-759, 1992 11. McClave SA, Snider HL, Lowen CC, et al: Use of residual volume as a marker for enteral feeding intolerance: Prospective blinded com14
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35.
36.
parison with physical examination and radiographic findings. J Parent Ent Nutr 16:99-105, 1992 Todd N, Marik PE, Zaloga GP: Bolus versus continuous gastric nutrient administration: Efficacy and risk for pneumonia in critically ill patients. Crit Care Med 27:A119, 1999 (abstr) Zaloga GP, Marik P: Promotility agents in the ICU. Crit Care Med 28:2657-2659, 2000 Kearns PJ, Chin D, Mueller L, et al: The incidence of ventilatorassociated pneumonia and success in nutrient delivery with gastric versus small intestinal feeding: A randomized clinical trial. Crit Care Med 28:1742-1746, 2000 Strong R, Condon S, Solinger M, et al: Equal aspiration rates from postpylorus and intragastric-placed small-bore nasoenteric feeding tubes: A randomized, prospective study. J Parent Ent Nutr 16:59-63, 1992 Montecalvo M, Steger K, Farber H, et al: Nutritional outcome and pneumonia in critically ill patients randomized to gastric versus jejunal tube feedings. Crit Care Med 20:1377-1387, 1992 Cook D, DeJonghe B, Heyland D: The relation between nutrition and nosocomial pneumonia: Randomized trials in critically ill patients. Crit Care 1:3-9, 1997 Metheny NA, Eisenberg P, Spies M: Aspiration pneumonia in patients fed through nasoenteral tubes. Heart Lung 15:256-262, 1986 American Thoracic Society Ad Hoc Committee of the Scientific Assembly on Microbiology Tuberculosis and Pulmonary Infections: Hospital acquired pneumonia in adults: Diagnosis, assessment of severity, initial antimicrobial therapy and preventive strategies: A consensus statement. Am J Respir Crit Care Med 153:1711-1725, 1995 Zaloga GP: Prevention of infection with endogenous organisms, in Browne D, Weiss JF, MacVittie, et al (eds): Treatment of Radiation Injuries. New York, NY, Plenum Press, 1990, pp 115-126 Silk DBA, Rees RG, Keohane PP, et al: Clinical efficacy and design changes of "fine bore" nasogastric feeding tubes: A seven-year experience involving 809 intubations in 403 patients. J Parent Ent Nutr 11:378-383, 1987 Rees RGP, Payne-James J J, King C, et al: Spontaneous transpyloric passage and performance of 'fine bore' polyurethane feeding tubes: A controlled clinical trial. J Parent Ent Nutr 12:469-472, 1988 Posniak H, Gottlieb K, Mikolaitis S, et al: What happens to blindly placed nasoenteral tubes? J Am Coil Nutr 12:318, 1993 Marian M, Rappaport W, Cunningham D, et al: The failure of conventional methods to promote spontaneous transpyloric feeding tube passage and the safety of intragastric feeding in the critically ill ventilated patient. Surg Gynecol Obstet 176:475-479, 1993 Zaloga GP: Bedside method for placing small bowel feeding tubes in critically ill patients. A prospective study. Chest 100:1643-1646, 1991 Zaloga GP, Roberts PR: Bedside placement of enteral feeding tubes in the intensive care unit. Crit Care Med 26:987-988, 1998 Thurlow PM: Bedside enteral feeding tube placement into duodenum and jejunum. J Parent Ent Nutr 10:104-105, 1986 Ugo PJ, Mohler PA, Wilson GL: Bedside postpyloric placement of weighted feeding tubes. Nutr Clin Pract 7:284-287, 1992 Salasidis R, Fleiszer T, Johnson R: Air insufflation techniques of enteral tube insertion: A randomized controlled trial. Crit Care Med 26:1036-1039, 1998 Spalding HK, Sullivan KJ, Soremi O, et al: Bedside placement of transpyloric feeding tubes in the pediatric intensive care unit using gastric insufflation. Crit Care Med 28:2041-2044, 2000 Welch SK: Certification of staff nurses to insert enteral feeding tubes using a research-based procedure. Nutr Clin Pract 11:21-27, 1996 Harrison AM, Clay B, Grant MJC, et al: Nonradiographic assessment of enteral feeding tube position. Crit Care Med 25:2055-2059, 1997 Botoman VA, Kirtland SH, Moss RL: A randomized study of a pH sensor feeding tube vs a standard feeding tube in patients requiring enteral nutrition. J Parent Ent Nutr 18:154-158, 1994 Dimand RJ, Veereman-Wauters G, Braner DAV: Bedside placement of pH-guided transpyloric small bowel feeding tubes in critically ill infants and small children. J Parent Ent Nutr 21:112-114, 1997 Gabriel SA, Ackermann RJ, Castresana MR: A new technique for placement of nasoenteral feeding tubes using external magnetic guidance. Crit Care Med 25:641-645, 1997 Hernandez-Socorro CR, Marin J, Ruiz-Santana S, et al: Bedside sonographic-guided versus blind nasoenteric feeding tube GARY P. ZALOGA
37. 38.
39. 40.
41.
placement in critically ill patients. Crit Care Med 24:1690-1694, 1996 Levy H: Postpyloric feeding tube placement and the use of electromyographic technology. Nutr Clin Pract 12:$28-30, 1997 Grathwohl KW, Gibbons RV, Dillard TA, et al: Bedside videoscopic placement of feeding tubes: Development of fiberoptics through the tube. Crit Care Med 25:629-634, 1997 Prager R, Laboy V, Venus B, et al: Value of fluoroscopic assistance during transpyloric intubation. Crit Care Med 14:151-152, 1986 Kirby DF, Clifton GL, Turner H, et al: Early enteral nutrition after brain injury by percutaneous endoscopic gastrojejunostomy. J Parent Ent Nutr 15:298-302, 1991 DeLegge MH, Duckworth F, McHenry L, et al: Percutaneous endoscopic gastrojejunostomy: A dual center safety and efficacy trial. J Parent Ent Nutr 19:239-243, 1995
ENTERIC FEEDING TUBES
42. Torres A, Serra-Batles J, Ros E, et al: Pulmonary aspiration of gastric contents in patients receiving mechanical ventilation: The effect of body position. Ann Intern Med 116:540-543, 1992 43. Orozco-levi M, Torres A, Ferrer M, et al: Semirecumbent position protects from pulmonary aspiration but not completely from gastroesophageal reflux in mechanically ventilated patients. Am J Respir Crit Care Med 152:1387-1390, 1995 44. Ferrer M, Bauer -I-r, Torres A, et al: Effect of nasogastric tube size on gastroesophageal reflux and microaspiration in intubated patients. Ann Intern Med 130:991-994, 1999 45. Kuo B, Castell DO: The effect of nasogastric intubation on gastroesophageal reflux: A comparison of different tube sizes. Am J Gastroenterol 90:1804-1807, 1995 45. Fisher RS, Malmud LS, Roberts GS, et al: Gastroesophageal (GE) scintiscanning to detect and quantitate GE reflux. Gastroenterology 70:301-308, 1976
"15
Early enteral nutrition, especially with immune-modulating formulas, has been shown to improve outcomes in critically ill patients. Early nutrient delivery supports organ function and recovery from illness and modulates inflammation and organ injury. Misconceptions regarding gastrointestinal function and alterations in gastrointestinal function during illness impede early enteral feeding. Bowel sounds, elevated gastric residuals, failure to pass flatus, and diarrhea are not contraindications to enteral nutritional support. Most critically ill patients can be fed into the stomach with minimal risk for aspiration. Promotility agents aid in gastric feeding. When gastric feeding is not possible, most patients will tolerate small intestinal feeding. Because spontaneous passage of feeding tubes into the small bowel in critically ill patients is rare, most feeding tubes can be positioned into the small bowel with blind bedside placement by the clinician (ie, physician, nurse, nutritionist). When such procedures are not successful, x-ray guided or endoscopic placement of feeding tubes into the small bowel are recommended. Occasionally, small bowel feeding tubes will need to be placed surgically. Copyright 9 2001 by W.B. Saunders Company
E
nteral nutrition is the preferred route of nutritional support in all groups of patients. Enteral feeding is superior to parenteral feeding. In addition, recent reviews and meta-analyses indicate that early enteral administration of nutrients improves outcome compared with delayed enteral feeding. 1,2 Outcome in these analyses was defined as complications, infections, length of hospitalization, costs, or mortality. Current analyses also indicate that use of nutrients with immune support and inflammatory control are superior to standard enteral diets. 3-5 Thus, early institution of enteral nutrition represents an important therapy for optimizing care and improving outcome. There are a number of barriers that delay enteral nutritional support. 6"s These include lack of appreciation for the benefit of early enteral nutrition, misconceptions regarding gastrointestinal function and evaluation, and the inability to place feeding tubes in an expeditious and inexpensive manner. This article reviews these issues.
Benefits of Early Enteral Nutrition Enteral nutrition supplies a large variety of nutrients that are important for the body's response to illness, healing, prevention of cell injury, and recovery from illness and injury. Although
From the Department of Critical Care Medicine, Suburban Hospital, Bethesda, MD. Address reprint requests to Gary P. Zaloga, MD, Director of Research, Intensimed, 7309 Bannockburn Ridge Ct, Bethesda, MD, 20817. Copyright 9 2001 by W.B. Saunders Company 1096-2863/01/0301-0003535.00/0 doi:10.1053/tgie.2001.19907
the body has evolved complex mechanisms for storing and mobilizing nutrients, these mechanisms are not as effective as exogenous nutrient intake. Exogenous intake provides larger amounts and greater variety of nutrients than does endogenous mobilization (ie, amino acids, lipids, electrolytes, trace elements, vitamins, antioxidants). In addition, many patients are malnourished or have organ dysfunction/failure before hospitalization and cannot mobilize adequate quantities of some nutrients (ie, arginine, zinc, magnesium, glutathione, vitamin E). Early institution of enteral feeding after injury is associated with improved organ function (Table 1). The organs most affected by early enteral feeding are the gastrointestinal tract, liver, kidneys, and immune system. Experimental data indicate that enteral feeding can prevent organ dysfunction in various models of critical illness (ie, shock, burn, hemorrhage, sepsis). Improved organ function (especially immune function) is associated with decreased infections, complications, length of stay, and cost 1,2 in humans with critical illness. Based on the benefits of early enteral feeding, many clinicians begin enteral nutrition (ie, metabolic resuscitation) immediately after cardiopulmonary resuscitation of the patient. This process is termed the ABCD (airway, breathing, circulation, diet) approach to resuscitation.
Nutritional Misconceptions Misconceptions regarding gastrointestinal tract function are major causes of delayed enteral feeding. 6,s The gastrointestinal tract is composed of the upper tract (mouth and esophagus), stomach, small intestine, colon, and rectum. Most patients with severe illness will not be capable of ingesting adequate nutrition safely (ie, oral route). Altered mentation and dysregulated swallowing impair intake and place patients at risk for aspiration. Thus, most critically ill patients will require use of feeding tubes for delivery of enteral nutrients. After critical illness, many investigators report a decrease in gastric emptying and colonic motility. However, most studies indicate that small intestinal motility remains relatively intact and adequate for enteral feeding. Importantly, the effects of illness on gastric emptying appear to be related to timing of feeding after illness and the severity of the underlying disease. Gastric feeding can be accomplished in most patients when feeding is begun within hours of illness or injury. Delaying feeding for many hours to days results in progressive impairment of gastric emptying and may prevent use of the gastric route. These patients frequently require placement of small bowel feeding tubes for nutrient delivery. Colonic motility rarely causes problems with nutritional support. Although bowel movements are uncommon for the first few days (ie, 2 to 4 days) after onset of critical illness, few patients develop clinically significant bowel distention. Feeding fully absorbable enteral formulas (ie, nonfiber formulas) is
Techniques in Gastrointestinal Endoscopy, Vol 3, No 1 (January), 2001: pp 9-15
9
T A B L E 1. Benefits of Enteral Nutrients on Organ Function
Organ
Nutrient Effects
Gastrointestinal tract
Improvedmotility Improved mass Improved absorption Decreased permeability Improved blood flow Improved mucous layer Improved immunity Decreased bacterial adherence Increased IgA secretion Maintenance of lymphoid tissue Decreased bacterial/yeast/toxin translocation Increased mass Improved function Increased blood flow Improved B and T cell function Improved phagocytosis Improved bacterial/fungal killing Improved IgA secretion (gut) Improved lymphoid tissue (gut) Decreased infections Improved healing Improved Improved blood flow Improved recovery from acute renal failure
Liver Immune
Wound Protein synthesis Renal
well tolerated and the formula is usually completely absorbed before it enters the colon. Although most clinicians listen for bowel sounds before they initiate enteral nutrition, few listen properly and even fewer understand the meaning of bowel sounds. Bowel sounds are produced when air is propelled through the intestines (small and large) by peristalsis. There is a large range for bowel sounds in healthy individuals. One may hear anywhere from a few per minute to almost continuous sounds. Proper listening for the absence of bowel sounds requires 3 to 4 minutes in each of the 4 abdominal quadrants. Few clinicians ever listen for 12 to 16 minutes. Bowel sounds should be described as present or absent and not hypo- or hyperactive (because of the wide range of sounds normally). Bowel sounds require the presence of air in the gastrointestinal tract and will be decreased in patients with impaired swallowing and in those who receive nasogastric suctioning. Because bowel sounds are dependent on the quantity of air in the gut and gastric emptying, they are poor indicators of bowel peristalsis and feeding tolerance. Hearing many sounds suggests that gastric emptying is adequate for feeding. However, hearing few sounds has little predictive power for determining tolerance to feeding. Bowel sounds can easily be elicited by injecting air into the stomach via a nasogastric tube. We do not recommend the routine evaluation of bowel sounds. Instead, assessment of the abdomen by clinical examination and evaluation of gastric residual volume are better predictors of enteral feeding tolerance. Diarrhea is not a contraindication for enteral feeding. Most diarrhea which develops in hospitalized patients without short gut syndrome results from prosecretory states and not from the enteral feeding. 9 A healthy gut can tolerate standard nutritional formula feeding rates up to 275 mlJhr. 9 Infection with release of cytokines and toxins stimulates gut secretory activity. The diarrhea usually resolves with control of the underlying disease state and most patients tolerate partial to full enteral feeding. Diarrhea can be minimized by eliminating osmotic agents (ie, magnesium), treating infections, minimizing use of unneeded antibiotics that contribute to bacterial overgrowth or selection, 10
use of fiber formulas, and use of antisecretory and antimotility agents (ie, opiates, bismuth subsalicylate). The incidence of diarrhea reported in intensive care unit (ICU) patients varies greatly. Much of the difference can be explained by differences in the definition used to define diarrhea. ~~ Some consider diarrhea to be present in patients with multiple bowel movements (even if they are formed and of low volume). Others define diarrhea as present in any patient with liquid stool. Many critically ill patients have rectal incontinence and one should not define diarrhea as multiple small volume formed bowel movements per day. Montejo et al 7 defined diarrhea as 5 or more liquid stools in a 24 hour period or an estimated volume of 2,000 mL or greater per day. Fourteen percent of 400 patients had at least 1 episode of diarrhea. However, the diarrhea was short lived in most patients (ie, lasting less than 1 day) and persisted for more than 3 days in only 3% of patients. Diarrhea resulted in withdrawal of enteral feeding in only 3% of patients. We define diarrhea as 3 or more liquid bowel movements per day or 350 mL or more of liquid stool per day. The incidence of diarrhea in our medical ICU patients is approximately 5% and usually subsides within 3 days, despite continuation of enteral feeding. Some clinicians do not feed their patients until the patients admit to or are noted to pass flatus. We do not favor this practice. Flatus is present in most patients even if patients and nursing staff are not aware of it. In addition, fully absorbable formulas do not require colonic function. Our practice is to feed patients with nonfiber formulas until they have a bowel movement. Fiber can be given once bowel movements resume. We also follow clinical examination of the abdomen. Extensive clinical experience indicates that these patients tolerate early enteral feeding.
Gastric Residual Volume Gastric residual volume has been used by clinicians for many years as a parameter for assessing tolerance of gastric feeding and risk for aspiration. However, little data in the literature support the use of gastric residuals for these purposes. Controlled trials have not been performed to establish the validity, range, and limitations of gastric residual monitoring. This is interesting because physicians, nurses, and nutritionists frequently stop enteral feedings based on gastric residual volume, regardless of clinical status. Although aspiration is increased by large gastric residual volumes and incompetent lower esophageal sphincter tone, there is no direct relationship between gastric residuals and aspiration. Few studies have evaluated gastric residuals in healthy, bedridden, and critically ill patients. Gastric residuals also vary with the time after a meal. McClave et al H studied gastric residual volume during 8 hours (at bedrest) of total enteral nutrition (65 to 175 mL/hr) in 20 volunteers, 8 stable patients with gastrostomy tubes, and 10 critically ill patients. None of the subjects was intolerant to the feeds and none of the patients sustained obvious aspiration. Fasting residual volumes in the volunteers and critically ill patients were close to zero. During feeding, 2.4% of gastric residuals in the volunteers were above 150 mL; 13% were above 150 mL in the critically ill patients; none of the residuals were greater than 150 mL in the gastrostomy group. Findings on physical examination failed to predict gastric residual volume. McClave et a111 suggested that gastric residuals of 200 mL obtained from a nasogastric tube should GARY P. ZALOGA
raise concern about intolerance. Adam and Batson 6 evaluated 193 critically ill patients. Average daily gastric aspirates during gastric feeding were 200 to 220 mL during the first few days of feeding and decreased to approximately 100 mL during the remainder of the patients' ICU stay. We evaluated fasting (admission gastric residual volumes) and gastric residual volumes during enteral feeding (every 4 to 6 hours for 72 hours) in 100 medical ICU patients (Table 2). Fasting gastric residuals were obtained with an oral or nasogastric tube as the patient lay in the supine position with the head elevated at 30 ~ on admission to the medical ICU. Thirty percent were greater than 100 mL, 15% were greater than 150 mL, and 6% were greater than 200 mL. Interestingly, gastric residual volumes decreased with gastric feeding (100 mL every 2 hours) and only 8% of fed patients had gastric residual volumes greater than 150 mL. We found no relationship between gastric residual volume and aspiration in these patients. We also compared gastric residual volume and risk for aspiration in 18 critically ill patients randomized to bolus feeding (100 mL every 2 hours) or continuous feeding (50 mL/hr). 12 There was no evidence for aspiration in any of the patients. Both groups received similar quantities of nutrition that met 85% to 90% of their nutritional goals over 72 hours of study. Gastric residual volumes (Table 3) were similar between groups and decreased with duration of gastric feeding. In summary, morning gastric residual volumes in ambulatory healthy individuals who fast after midnight are close to zero. Normal gastric residuals in fasting supine critically ill patients are usually under 150 mL, with an occasional patient having a residual of 150 to 250 m L These patients usually tolerate gastric feeding without problems, and gastric residuals may decrease in patients being enterally fed. During enteral feeding, we use a gastric residual volume of 150 mL as an indicator of possible feeding intolerance.
Gastric Feeding Most critically ill patients require the use of feeding tubes for nutrient delivery. These tubes can be placed into the stomach or small intestine. Although it was once believed that critically ill patients would not tolerate gastric feeding because of gastroparesis and the risk of aspiration, recent experience suggests that gastric feeding is usually well tolerated in most patients. With aggressive resuscitation, limited use of antimotility agents (ie, opiates), use of promotility agents, and institution of very early feeding, most patients will tolerate gastric nutritional support. This does not mean that gastric emptying is normal in all the patients. However, it does indicate that the decrease in gastric emptying experienced by most ICU patients allows for adequate gastric delivery of nutrients. In a review of 300 patients in our medical intensive care unit (Table 4), we found that 95% were fed within 12 to 24 hours of TABLE 2. Gastric Residual Volumes in 100 Medical ICU Patients Gastric Residual
Fasting
During Gastric
Volume (mL)*
(Admission)
Feeding
>200 >150 > 100
6 15 30
2 8 20
TABLE 3. Gastric Residual Volumes (GRV) During Bolus and Continuous Gastric Feeding in 18 Medical ICU Patients
Day
Bolus Maximal GRV (mL)
Bolus Average GRV (mL)
Continuous Maximal GRV (mL)
Continuous Average GRV (mL)
1 2 3
88 + 4 6 52• 45 + 2 4
28_+13 18_+9 18_+11
92_+41 35_+18 12_+4"
28+13 15+-8 7-+2
* P < .05 compared with bolus.
admission and tolerated gastric feeding. Only 5% required placement of small bowel feeding tubes or parenteral nutrition. This evaluation included patients with ARDS (acute respiratory distress syndrome), respiratory failure secondary to chronic obstructive pulmonary disease or asthma, pneumonia, intracranial bleeds and ischemic strokes, renal failure, shock (sepsis, hemorrhagic, cardiogenic), gastrointestinal bleeding, liver failure, status epilepticus, and malignancies. Feeding tubes were placed into the stomach by the bedside nurse. Gastric residuals were monitored every 2 to 4 hours. Most nutrition was delivered by the bolus method. A recent evaluation of 40 patients in our ICU fed within 12 to 24 hours of ICU admission indicated that none of the patients developed clinically significant aspiration pneumonia. Aspiration pneumonia was defined as a new pulmonary infiltrate that occurs in a patient who is receiving gastric nutrition. All patients were fed with the head of the bed elevated approximately 30 ~ None of these patients had deterioration in oxygenation, defined as the ratio of PO 2 to inspired oxygen concentration (ie, PO~/FIO 2 ratio). These data do not exclude aspiration but suggest that the risk is low. Interestingly, evaluation of patients with aspiration pneumonia admitted to the ICU failed to reveal an association between gastric tube feeding and aspiration. An occasional patient was admitted with aspiration pneumonia after dislodgment of the feeding tube during continuous feeding. Montejo et aF evaluated 400 consecutive patients admitted to the ICU and receiving enteral feeding. Ninety-one percent received gastric feeds. The incidence of aspiration pneumonia was reported to be 1.5%.
Gastrointestinal Motility Agents A number of agents administered to critically ill patients can interfere with gastrointestinal motility. Opiates are the most common. However, decreased motility can also be seen with some neuromuscular blocking agents (caused by their anticholinergic effects) and other anticholinergic agents. We minimize the use of opiates for pain control. Our primary agent for sedation/analgesia is propofol. Although touted as a sedative agent,
TABLE 4. Route of Early Nutritional Support in 300 Medical ICU Patients Route*
Number (%)
Gastric
185 (95%) 10 (3%) 5 (2%)
Small bowel Parenteral nutrition
* Excludes patients admitted on parenteral nutrition (ie, short gut * Obtained in the supine position, head of bed elevated to 30 ~ ENTERIC FEEDING TUBES
syndrome). 11
at high doses propofol produces excellent analgesia. This agent does not decrease gastric emptying or gut motility. When gastric residuals volumes are consistently greater than 150 to 200 mL, we administer promotility agents. The 3 agents available on the market are erythrolnycin (100 to 250 mg every 6 hours), metoclopramide (10 mg every 6 hours), and cisapride. Cisapride has numerous toxic effects, especially on the cardiovascular system. It is being withdrawn from the market and should not be used. It is no more effective than the other agents. A number of studies of the promotility effects of the above agents have been conducted in critically ill patients. 13 Three prospective randomized controlled trials evaluated the effects of metoclopramide on gastric emptying in critically ill patients. ~3 Two of the 3 trials (using acetaminophen absorption and feeding tube migration) reported increased emptying. Four studies evaluated the effect of erythromycin on gastric emptying. All reported increased emptying (using acetaminophen absorption, gastric residuals, and feeding tube migration). We favor the use of erythromycin over metoclopramide. Interestingly, we have treated a few patients who continued to have large gastric residuals despite erythromycin who improved when metoclopramide was added to the erythromycin. We discontinue these agents periodically (ie, every 3 to 5 days) as the patient improves to determine if treatment with the agents is still required.
Benefits of Postpyloric Feeding The primary indication for postpyloric feeding is the maintenance of nutritional intake in patients intolerant of gastric feeding. Most patients with high gastric residuals and clinically significant gastroesophageal reflux can be administered adequate nutritional support via the postpyloric route. Many clinicians believe that postpyloric feeding decreases the risk for aspiration. However, a decrease has not been proven in controlled studies. ~4q7 Kearns et al ~4 investigated the incidence of ventilator-associated pneumonia in a small group (n = 44) of patients randomized to gastric versus small intestinal feeding. The small bowel feeding group did not receive gastric decompression or monitoring of gastric residuals. The incidence of ventilator-associated pnemnonia was similar in both groups (4/21 v 3/23). However, nutrient delivery was better in the small intestinal feeding group. Two other randomized trials of gastric versus small bowel feeding failed to document decreased aspiration in the small bowel fed patients. ~5,16 However, nutrient delivery was improved with small bowel feeding. ~5,16 Unfortunately, these studies had small numbers of patients and were underpowered to show clinically significant differences in the incidence of aspiration pneumonia. Although not clearly proven in prospective randomized trials, we and others 18,19 believe that small bowel feeding (especially when combined with gastric decompression) minimizes aspiration in the subset of patients at high risk for aspiration or with significant gastroesophageal reflux. In fact, the American Thoracic Society's consensus statement concludes that distal enteral feeding sites probably decreases the risk of nosocomial pneulnonia. 19
Spontaneous Transpyloric Passage of Feeding Tubes In a previous study of mixed medical-surgical critically ill patients, 2~ we found that only 5% of small bore feeding tubes passed spontaneously into the small bowel over 3 days. This
12
rate was not improved with metoclopramide. Silk et al 2~ reported a spontaneous passage rate over an average of 4 to 5 days for small bore feeding tubes of 0% to 4%. The rate was 0% (0/76) for unweighted feeding tubes and 4% (3/79) for weighted tubes. Rees et a122 evaluated spontaneous small bore feeding tube passage into the small bowel in general ward and intensive care unit patients. A total of 69 patients were studied. Spontaneous transpyloric passage of the tubes occurred in approximately one third of the patients. Importantly, a third of the patients in this study were mobile. Posniak et a123 reported a 13% passage rate and Marian et a124 reported a 15% spontaneous passage rate for feeding tubes. Thus, a small percentage of small bore feeding tubes pass spontaneously into the small bowel in critically ill patients. Early initiation of enteral feeding in patients intolerant of gastric feeding requires active placement of the feeding tubes into the small bowel.
Placement of Small Bowel Feeding Tubes When gastric emptying fails to improve with promotility agents or the patient has documented pulmonary aspiration, we place small bowel feeding robes. Most of the time, these tubes can be placed into the small bowel at the bedside. 25,26 In our initial study in 1991,25 we attempted 231 bedside small bowel feeding tube placements using the "corkscrew technique" and were successful in 213 (92%) of the placements. Seven (3%) of the tubes were in the first part of the duodenum, 57 (25%) in the second portion of the duodenum, 109 (47%) in the third portion of the duodenum, and 40 (17%) were in the proximal jejunum. The average time for placement of the tubes in the 1991 study was 40 minutes. However, with additional experience the time was reduced to 10 to 20 minutes. This technique has been used by other clinicians and found to be successful in 75% to 90% of attempts. 27 In our initial study, we emptied the stomach before placing the feeding tubes. However, because gastric distension is a stimulus for gastric emptying, others report excellent success in placing small bowel feeding tubes with use of air insufflation. 28-3~We incorporated air insufflation along with the "corkscrew technique" and were able to place over 95% of small bowel feeding tubes in approximately 5 to 15 minutes. Our current technique for placement of bedside small bowel feeding tubes involves placing the patient in the supine position and rotated 30 ~ to 40 ~ onto the right side (right side down). The stomach is emptied of its contents using a oral or nasogastric tube. The pH of the contents is checked using pH paper, and the contents are observed for bile. Then the oral or nasogastric tube is removed. A 10F to 12F weighted feeding tube containing a wire stylet is placed into the stomach. The stylet is removed, the tip is bent at a 30 ~ angle approximately 2 cm from the distal end, and it is reinserted into the feeding tube (Fig 1). The bend allows for the tip of the tube to cover a greater surface area during rotation and helps the tip to "hook" the pyloric outlet during tube advancement. A 60 mL syringe is used to pump 10 mL/kg of air into the stomach (in adults). After air insufilation, the feeding tube is slowly rotated and advanced in short 4 to 5 cm bursts until it is inserted the appropriate length compatible with a small bowel location. The tube is allowed to slowly advance and is not forced forward. Advancement can be assisted by repeated injection of small volumes of air. The tube is taped in place and its position checked by aspiration. A change of pH from acidic (stomach) to basic or the appearance of bile (not found in the stomach) suggests small bowel placement. In GARY P. ZALOGA
addition, the inability to aspirate insufflated air suggests small bowel versus gastric placement. There is also a change in location and pitch of bowel sounds when moving from the stomach into the small bowel. Air insufflated into the stomach has a lower pitch, is heard best in the left upper quadrant, and does not radiate well to the right flank. Air insufflated into the small bowel is of higher pitch, best heard in the midline or right upper quadrant, and radiates well to the right flank. One can also check for small bowel position by placing a nasogastric tube and injecting blue dye through the small bowel tube. Failure of the dye to appear from aspiration of the gastric tube indicates small bowel location. If the position is uncertain, a radiograph can be obtained to determine tube position. We instructed a n u m b e r of nurses to perform this procedure at the bedside. In a prospective evaluation of 59 attempted small bowel placements, nurses were successful in placing 7"5%.26 The mean time for placement was 11 minutes. A few patients had minor complications but no patient had major complications. In a n u m b e r of institutions feeding tubes are being placed by nurses and other nutritional support personnel with good success. Welch 31 reported a study in which 79 nurses were certified in feeding tube placement and 90% of attempts successfully intubated the duodenum. Harrison et aP 2 reported a 99% success rate when feeding tubes were directed into the small bowel by bedside nurse practitioners in a pediatric ICU. Blind bedside placement of small bowel feeding tubes has been successful in the hands of m a n y clinicians. However, some have not achieved a high success rate, which may relate to training, experience in the technique, and the severity of underlying illness of patients. Thus, m a n y clinicians have sought bedside methods that can aid in placement of feeding tubes. These have included pH sensor guidance,33, 34 magnetic guidance, 35 sonographic guidance, 36 electromyographic guidance, 3r and fiberoptic scopes 3s through the feeding tubes. Gabriel et a135 used a hand-held magnet to maneuver a nasoenteral feeding tube containing a small magnet at its tip into the small bowel in critically ill patients. Forty-two intubations were performed in 35 patients and the investigators were successful in 88% (mean procedure time 15 minutes). This technique is being evaluated by other investigators. Preliminary reports indicate a lower success rate of about 50%. Grathwohl et aP s evaluated use of a videoscope attached to an angioscope that was placed through a 12F feeding tube. They were able to visualize enteric structures through the scope and were suc-
Fig 1. Bending of wire stylet for "corkscrew" technique.
ENTERICFEEDINGTUBES
I
RESUSCITATIONCOMPLETE I (Airway,Breathing,Circulation) I
I
PLACEOG/NG TUBE INTO STOMACH
I G R > 150ml
G R < 150ml
Empty Stomach Contents
I Begin Enteral Feeding I .., (ie. 100ml bolus Q
2hr)I
Discard
II I
CHECK GR EVERY 2 Hours (before next bolus)
GR~5OmI ~ i Continue Enteral Feeding
I
I
L
GR>150ml
! A0ent Be0'nPr~176l-(ie. erythromycin)
CHECK GR EVERY 2 Hours GR
.....
Increase Volume of Feeds (ie. 1 can every 4hrs); Increase GR Monitoring
Interval to Every 4 hrs.
50ml
"'
PromotilityAgentPlus Trial of ContinuousEnteralFeeds
(ie.50mi/hr)
or PlaceSmallBowelFeedingTube & RestartFeeds
Fig 2. Approach to early enteral feeding. cessful in placing all tubes into the small bowel in a small number of normal individuals and critically ill patients. Hernandez-Socorro et aP 6 used bedside ultrasound to guide feeding tubes into the small bowel in critically ill patients. The technique was successful in 85% (22/26) of patients in whom blind bedside small bowel placement failed. We have not found that pH sensor guided tubes offer much over use of intermittent pH assessment using pH paper. Although they are easier to use for evaluating pH changes, the cost of the tubes is much greater. Levy3r used electromyographic guidance to place postpyloric feeding tubes. This technology measures spontaneous electrical activity of the gut and can distinguish between gastric and small intestinal locations. Overall success rate was 92% with the technique. Further study of these techniques is required. It is important for this studies to consider cost-effectiveness of the techniques. When bedside maneuvers are not successful, small bowel feeding tubes can be placed in most patients using x-ray guidance, 39 endoscopic guidance, 4~ or surgery. These methods are discussed in other articles in this issue.
13
Conclusions We use the ABCD approach to enteral feeding (Fig 2). After control of the airway, assessment and support of breathing, and support of the circulation, we begin diet resuscitation (ie, nutrient delivery). Delivery of nutrients is by feeding protocol (Fig 2). A number of studies indicate that nutrient delivery is improved when administration is directed by a feeding protocol. We minimize the use of antimotility agents such as opiates and neuromuscular blockers. Our primary sedative in intubated patients is propofol because of its minimal effects on gut motility. Whenever possible, patients are maintained with the head of the bed elevated at 20 ~ to 30 ~, to minimize the risk of aspiration. There are no reliable clinical tests for monitoring the patient for aspiration. The exact incidence of aspiration is unclear and has been reported to range from 0% to 50%. In addition, the number of patients with aspiration of formula who go on to develop pneumonia is also unknown. Some clinicians place blue dye in the nutritional formula. Appearance of dye in pulmonary secretions indicates that aspiration has occurred. However, this test lacks sensitivity. Others have used serial monitoring of tracheal glucose levels. The reliability of this test is also questioned. Aspiration does appear to be reduced by elevating the head of the bed.42,43 As discussed previously, there is no clear relationship between gastric residual volume and aspiration; however, most clinicians monitor gastric residuals and hold feeding when the residual is greater than 150 to 200 mL. Recent studies suggest that use of an orogastric or nasogastric tube does not increase the risk of aspiration above that of small bore feeding tubes. 44,45 Some have suggested that competence of the lower esophageal sphincter is actually increased by the presence of a tube across the esophageal junction. 46
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42. Torres A, Serra-Batles J, Ros E, et al: Pulmonary aspiration of gastric contents in patients receiving mechanical ventilation: The effect of body position. Ann Intern Med 116:540-543, 1992 43. Orozco-levi M, Torres A, Ferrer M, et al: Semirecumbent position protects from pulmonary aspiration but not completely from gastroesophageal reflux in mechanically ventilated patients. Am J Respir Crit Care Med 152:1387-1390, 1995 44. Ferrer M, Bauer -I-r, Torres A, et al: Effect of nasogastric tube size on gastroesophageal reflux and microaspiration in intubated patients. Ann Intern Med 130:991-994, 1999 45. Kuo B, Castell DO: The effect of nasogastric intubation on gastroesophageal reflux: A comparison of different tube sizes. Am J Gastroenterol 90:1804-1807, 1995 45. Fisher RS, Malmud LS, Roberts GS, et al: Gastroesophageal (GE) scintiscanning to detect and quantitate GE reflux. Gastroenterology 70:301-308, 1976
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