Assessing the Metabolic and Clinical Consequences of Early Enteral Feeding in the Malnourished PatientFrom the Richmond Hospital, Richmond, British Columbia, Canada Correspondence: Mrs. Mary E. Flesher, RD, 5171 Bunting Avenue, Richmond, British Columbia V7E 5X3, Canada. Electronic mail may be sent to mflesher{at}shaw.ca. Background: It is often thought that enteral feeding should be initiated slowly in those who are severely malnourished. This descriptive study examined the effect of an enteral feeding protocol on the typical metabolic consequences seen in refeeding syndrome. Methods: A retrospective chart review was conducted on 51 patients who had been placed on hospital-wide enteral feeding and electrolyte replacement protocols over a 9-month period to determine whether there were any negative clinical consequences to early feeding. Results: Goal feeding rate was achieved within 17.6 ± 8.7 hours. Forty patients (80%) developed depletions in phosphate, magnesium, or potassium after initiation of enteral feeding, including 93% of those deemed "at risk" and 74% of those "not at risk." All patients received electrolyte replacement according to protocols, and no patients showed any negative clinical effect. Conclusions: This study showed that malnourished patients at risk for refeeding syndrome can be fed early without observed negative clinical consequences. An electrolyte replacement protocol may be an effective means of minimizing the electrolyte imbalances associated with early feeding. It also demonstrated the significance of applying such protocols to all patients requiring enteral support, as current methods of assessing "risk" for refeeding syndrome may be inadequate. Refeeding syndrome is a set of metabolic abnormalities that can occur when a severely malnourished patient begins feeding. In a starved state, fat and muscle catabolism leads to losses of phosphate, magnesium, and potassium. These depletions are not reflected in serum levels because of adjustments in renal excretion rates.1 With refeeding, carbohydrate intake triggers insulin release, causing an intracellular shift of phosphate, magnesium, and potassium and a decrease in serum levels.2 Refeeding of carbohydrate also contributes to sodium retention and expansion of extracellular fluid, leading to cardiac overload and weight gain, particularly in the presence of excessive sodium intake.2,3 Eventually, this glucose load can suppress gluconeogenesis, resulting in hyperglycemia.1 Refeeding syndrome is thus the consequence of compartmental shifts, depletions and repletions of phosphate, magnesium, potassium, glucose and fluid.1 Severe hypophosphatemia (<0.4 mmol/L) can cause symptoms like congestive heart failure, arrhythmias, ataxia, confusion, seizures, and paresthesias.1,2,4,5 Some symptoms of severe hypomagnesemia (<0.4 mmol/L) are arrhythmias, tachycardia, diarrhea, seizures, hypocalcemia, and irritability.1,2,4,5 Severe hypokalemia (<2.5 mmol/L) can cause ileus, cardiac arrest, arrhythmias, paresthesias, paralysis, and respiratory depression.1,2,4,5 Evidence of fluid excess associated with refeeding syndrome may be seen with changes in weight, serum sodium, blood pressure, pulse, respiratory pattern, and with the presence of edema.6 Thiamine deficiency can be associated with refeeding syndrome because it is an essential coenzyme in carbohydrate metabolism.1,2 Severe thiamine deficiency (Wernicke encephalopathy) can also occur with carbohydrate loading in the presence of reduced thiamine body stores.1 Symptoms of thiamine deficiency include confusion, ataxia, coma, memory loss, impaired vision, congestive heart failure, metabolic acidosis, and reduced intestinal motility.2,6 The management of complications associated with refeeding have been previously reviewed.1–3 The first step is to recognize those at risk: patients with protein-energy malnutrition, alcohol abuse, anorexia nervosa, prolonged fasting, no nutritional intake for 7 days or more, or significant rapid weight loss.2,7 Secondly, laboratory data are monitored and abnormal values corrected accordingly.2,7,8 Finally, a slow increase in caloric delivery is recommended.1–3,7–9 The benefits of early feeding have been well documented.10–16 Early or aggressive enteral feeding, defined as reaching goal rate or calories within 48 hours, 17 is often avoided in patients identified as "at risk" for refeeding syndrome. An enteral feeding protocol would help to ensure standardized monitoring, prevention, and treatment of refeeding syndrome. The objective of this study was to assess the metabolic consequences of an aggressive enteral protocol that included monitoring and replacement of electrolytes. Additionally, we hypothesized that even patients identified by validated instruments as "well nourished" may develop the metabolic abnormalities. Therefore, an enteral protocol that monitored all patients for metabolic changes was used.
This retrospective descriptive study reviewed the medical records of surgical, medical, palliative, and intensive care patients at the Richmond Hospital. During this 9-month period, 51 patients were placed on the hospital-wide enteral feeding protocol. Fifty met the inclusion criteria (>18 years of age and on the enteral feeding protocol) and were included in the analysis (Table I); one patient, aged 13, was excluded because of age. Each patient had a nutrition care plan and subjective global assessment (SGA) completed by the dietitian (Fig. 1).18 The nutrition care plan included assessment of actual body weight, usual weight, body mass index (BMI), ideal weight, and height. Diagnosis, history, pertinent laboratory data, and pertinent medications were also noted. In order to assess a patient's nutritional status and risk of refeeding syndrome, SGA was done on each patient. The SGA provided a validated, qualitative assessment of the severity of patients' malnutrition according to their food intake, weight-loss pattern, gastrointestinal symptoms, and physical examination of fat loss, muscle wasting, and edema. Patients were then categorized as well nourished, moderately malnourished, or severely malnourished according to the SGA rating. Patients categorized as severely malnourished were designated "at risk" for refeeding syndrome. Some patients in the moderately malnourished category were also suspected as being "at risk" by the dietitian, especially in situations where patients were unable to give a reliable diet history.
The enteral feeding protocol (Fig.
2) included the planned formula choice, goal rate, rate of
progression, flushing volume, choice of feeding tube, laboratory tests, and
relevant medications. It also provided optional orders for daily thiamine and
multivitamins. Prechecked boxes were used to ensure all necessary laboratory
data, and monitoring for weight and gastric residuals was completed.
Tube-feeding goal rates were determined using 25–30 kcal/kg/d for normal
or underweight
patients.19
Patients with a BMI of
Baseline serum levels of phosphate, magnesium, and potassium were compared with subsequent daily, biweekly, and weekly values. An evidence-based electrolyte replacement protocol was used to replete phosphate according to measured serum phosphate and serum creatinine (Fig. 2).5 Magnesium and potassium were replaced by physician's orders on the surgical, medical, and palliative wards or by a preprinted protocol in the intensive care unit (Figs. 3 and 4).5 Because of the effect of feeding on fluid balance, evidence of weight gain was monitored using baseline and daily weights (for 3 or more days) and then subsequently weekly weights. Charting by physicians and nurses was screened to determine changes in respiratory and cardiac status, with emphasis on blood pressure, respiratory pattern, serum sodium, edema, and weight gains. Urinary electrolytes were not measured. Albumin level was measured (Fig. 2) because it has been correlated with SGA.18
Frequency and amount of bowel movements (BMs) were recorded because of the influence of diarrhea on electrolyte and fluid balance. Diarrhea was classified as 3 or more loose BMs, >500 mL via rectal tube or more than 1 L ostomy output per day.20,21 The reason for initiating enteral feeding and the time required to reach goal rates were examined. The number of patients designated as "at risk" for refeeding syndrome and those experiencing drops in serum phosphate, magnesium, and potassium after refeeding despite not being categorized as "at risk" were also evaluated. Although all patients were screened for medications that could also contribute to these electrolyte imbalances (Table II), 22,23 no patients were excluded according to their medications. However, refeeding syndrome was not considered the cause of hypophosphatemia, hypomagnesemia, or hypokalemia in patients with preexisting electrolyte imbalances associated with contributory medications (Table II).
Patients were also not excluded according to their acute or chronic diagnoses (ie, congestive heart failure, alcoholism). Instead, these preexisting medical conditions were noted, and trends in weight, blood pressure, serum sodium, respiratory pattern, and edema were monitored. For the purpose of this study, weight gains that exceeded 3 kg with corresponding hyponatremia (<125 mmol/L)22,24 within the first week8 were considered a significant indicator of fluid volume excess. Fluid volume excess or deficits were treated by the health care team through adjustments in IV fluids, medications, enteral formulae, and enteral water flushes. Refeeding syndrome was not considered the cause of abnormal phosphate, magnesium, or potassium in patients experiencing clinical states like alkalosis or alcoholism.
Twenty-seven men and 23 women, aged 24 to 93 years, were included in this study (Tables I, III). Fifty-six percent of patients were treated in the intensive care unit at some point in their hospitalization.
Patients achieved their feeding goal rate within 17.6 ± 8.7 hours. The median number of days on a tube feeding was 6 days, with a range of 2–135 days. The average length of stay for patients was 24.9 days. Although some patients had preexisting cardiac and neurologic deficits, no complications associated with early enteral feeding were noted. No patients developed ventilator-associated pneumonia (VAP) while receiving enteral feeding, and 8 patients were admitted with preexisting aspiration pneumonia. Twenty-eight patients had been in the intensive care unit at some point in their stay, with 21 of 28 experiencing electrolyte imbalances. Eight patients died during their hospital stay because of their underlying disease process, although none were receiving a tube feeding at the time of death. Seven of 50 patients experienced diarrhea, with the average length of duration being 2.9 days. All these patients had below-normal electrolyte levels while experiencing diarrhea. However, only 1 of these patients had diarrhea within the first week of initiating enteral feeding, and therefore his changes in electrolyte levels were not attributed to refeeding.8 No patients with hyponatremia experienced weight changes above 3 kg within the first week of initiating feeding, and only 1 patient had a serum sodium of 125 mmol/L related to syndrome of inappropriate secretion of antidiuretic hormone. The mean albumin was 25.5 g/L, although some of the severely malnourished patients had normal or mild depletions in albumin.7 As expected in some patients who are chronically malnourished, albumin levels may be maintained because of shifts from extravascular to the intravascular compartments.7 the The patient with the BMI of 14.0 kg/m2 (Table I) had an albumin of 29 and experienced only mild depletions in phosphate and magnesium (Figs. 2, 3) with the initiation of enteral feeding. She reached her goal tube-feeding rate in 42 hours. Twenty-nine patients (58%) received thiamine supplementation per physician discretion, most being either patients in the intensive care unit or those having a history of alcohol abuse. The presence of hypophosphatemia, hypomagnesemia, or hypokalemia was similar in the thiamine-supplemented and the non-supplemented patients. Patients receiving and not receiving thiamine supplementation were given similar amounts of carbohydrate (100–160 g per 1000 kilocalories), and no symptoms of postrefeeding thiamine deficiency were observed. Forty patients (80%) developed hypophosphatemia, hypomagnesemia, or hypokalemia after initiation of enteral feeding (Table IV). All patients received electrolyte replacement according to protocols, and no patients showed any negative clinical effect. Fifteen patients (30%) were identified as "at risk" for refeeding syndrome according to the SGA rating or by dietitian assessment. Fourteen (93%) of the 15 patients categorized as "at risk" experienced a depletion of 1 or more of the measured electrolytes after initiation of enteral feeding compared with 26 (74%) of the 35 patients categorized as "not at risk" showing electrolyte abnormalities. Five patients developed severe hypophosphatemia (<0.4 mmol/L; Fig. 2) and 1 patient developed severe hypokalemia (<2.5 mmol/L; Fig. 4), but only 3 of these patients had been deemed "at risk" of refeeding syndrome. Of the remaining 3 deemed "not at risk," 2 of them were noted to have above normal BMIs (26.7 and 34.3 kg/m2).
Refeeding syndrome is a complication of nutrition support that can result in significant morbidity and mortality.1 Cardiac and neurologic events related to refeeding are most often seen in the first week of initiating nutrition support, justifying close monitoring and replenishment of electrolytes.8 Hernandez-Aranda et al25 found a 48% incidence of refeeding syndrome in patients assessed as having mild to severe malnutrition using an unspecified screening method. Marik and Bedigian26 found 34% of intensive care patients experienced refeeding hypophosphatemia after a starvation period as short as 48 hours. Although there is no known method of avoiding refeeding syndrome in all patients, most studies have recommended a slow, gradual feeding reaching goal rate in 4–7 days, providing a maximum 20 kcal/kg/d.1–3,9,27 In addition, many studies recommend electrolyte replacement with laboratory monitoring to help prevent complications this disorder.1–4,8,27–30 Kohn et al8 of suggested an initial goal rate of 130% of resting energy expenditure using Harris-Benedict Equation (HBE) to treat anorexia nervosa, followed by additional caloric increases to final goal rate. The final goal rates that are recommended in our hospital-wide enteral protocol are approximately 130% of HBE (or 25–30 kcal/kg/d) in attempts to avoid overfeeding in all patients.19 Fluid retention can be a serious complication of refeeding syndrome, although not all studies have proven this.9 It has been postulated that this fluid volume excess may be correlated with hypoalbuminemia because of depressed colloid osmotic pressure9 or because refeeding excessive carbohydrate causes sodium and water retention.1,2 This fluid overload may result in renal failure, cardiac failure, or death.2 Refeeding with only protein and fat often results in losses in weight and urinary sodium.2 All patients at risk of refeeding syndrome should be monitored for excessive weight gain, hyponatremia, blood pressure changes, and edema when initiating feeding. There are advantages and disadvantages of early feeding. Early provision of enteral nutrients can reduce septic complications, 10–13 improve wound healing, 14 reduce the hypermetabolic response to injury, 15,16 and maintain intestinal immunologic defenses.14,15 However, early enteral feeding should be used cautiously in patients who are hemodynamically unstable, are requiring substantial amounts of inotropic agents, or are receiving norepinephrine because this shunts blood away from the gastrointestinal tract.31,33 et al32 Ibrahim found a significantly greater incidence of VAP with early enteral feeding, but our study had no incidence of VAP related to tube feeding. It is often thought that early enteral feeding is contraindicated in patients at risk for refeeding syndrome. This study showed that the majority of patients had electrolytic changes, without observed metabolic complications, that could be corrected using electrolyte replacement protocols. Most patients reached their goal rates for enteral feeding within 24 hours of initiation, although 5 patients took between 27 and 42 hours. Forty of the 50 study patients showed a reduction in phosphate, magnesium, or potassium levels after initiation of enteral feeding. Fifty-two percent (26/50) of the study patients were not identified "at risk" using the SGA rating scale but showed electrolyte abnormalities. The implication of this result is that this screening method may be ineffective in identifying all patients "at risk" for refeeding syndrome and that a protocol that monitors and replaces electrolytes for all patients may be more effective. The cause of these patients' hypophosphatemia, hypomagnesiumemia, and hypokalemia was likely multifactorial but in part was associated with refeeding. Patients "not at risk" of refeeding syndrome may also have experienced these abnormalities because of their medication use or clinical state, but all of these patients had normal electrolyte levels before initiating their enteral feeding. When assessing overweight or underweight individuals using SGA or BMI, history of their weight pattern and current functional status are also important. Malnourished patients often had vitamin deficiencies, especially thiamine.1 Thiamine may have a contributory role in refeeding syndrome. Wernicke encephalopathy, seen in chronic alcohol abuse, can also develop in patients with poor nutritional status, especially with carbohydrate loading.1 Carbohydrate refeeding results in increased cellular thiamine use, requiring additional thiamine during this time.2 Fifty-eight percent of patients in this study received 100 mg of thiamine daily for up to 7 days. The patients receiving thiamine were no less likely to develop depletions of phosphate, magnesium, and potassium than those not receiving thiamine. Larger-scale studies would need to be done to determine whether routine thiamine supplementation is warranted in this population. This study demonstrated that early enteral feeding, using a standardized enteral feeding protocol, including electrolyte replacement protocols, showed no observed negative clinical consequence, even in patients deemed as "at risk" for refeeding syndrome. Patients who are not hemodynamically stable, volume resuscitated, or receiving norepinephrine should be fed cautiously. Further research on electrolyte monitoring and replacement protocols in orally fed patients with moderate to severe malnutrition would be useful. Additionally, specific screening tools for refeeding syndrome would be beneficial, especially for oral refeeding. Received for publication April 2, 2004. Accepted for publication December 2, 2004.
Journal of Parenteral and Enteral Nutrition, Vol. 29, No. 2,
108-117 (2005)
|
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 |
|
|
 |
|
Top
MATERIALS AND METHODS
RESULTS
35 kg/m2 received 21 kcal/kg of actual
body weight.
