Early enteral nutrition is recommended in critically ill adult patients. The optimal method of administering enteral nutrition remains unknown. Continuous enteral nutrition administration in critically ill patients remains the most common practice worldwide; however, its practice has recently been called into question in favour of intermittent enteral nutrition administration, where volume is infused multiple times per day. This presentation will outline the key differences between continuous and intermittent enteral nutrition, describe the metabolic responses to continuous and intermittent enteral nutrition administration and outline recent studies comparing continuous with intermittent enteral nutrition administration on outcomes in critically ill adults.

1. MD, IDCCM, FNB (Critical Care),
EDIC, ADHCA, DOA
Editor 'Critical Care WAarticles'
Senior Consultant Critical Care
Medanta The Medicity|
Global Health Private Ltd| Sector - 38|
Gurgaon - 122001|Haryana|India|
Mobile: +919899302959
Email- homeprashant@yahoo.com
Intermittent bolus feeding versus
Continuous enteral feeding

2. Introduction
Comparative Studies
What do guidelines
say?
Conclusion

3. Enteral tube feeding in adults
• The default mode of administration of nutrition when oral
intake is compromised and there is no contraindications.
• Generally safe, the most common serious complication of
tube feeding is misplaced tube into the lungs leading to
aspiration.
• Apparently looking simple and everyday happening in the
ICUs tube feedings are often heralded by innumerable
controversies.

4. Enteral
tube
feeding in
adults
Short Term
(less than 6
weeks)
Nasogastric
/ Orogastric
Tube
Long Term
(More than
6 weeks)
Gastrostomy/
Jejunostomy

5. Some other controversies on enteral nutrition
• Early versus late
• Gastric versus post pyloric
• Low fibre versus high fibre
• Polymeric versus predigested feeds
• Disease specific feeds such as renal, hepatic feeds etc.
• Gastric residual volume to stop feeds

6. Classification based on rate and frequency
EN via feeding
pump for 24
h/day
Cyclic
EN via feeding
pump for <24
h/day
Intermittent
EN over 20-60
min every 4-6 h
with/without
feeding pump
Bolus
EN over short
time period at
specified
interval via
gravity drip or
syringe
DiscontinuousContinuous

7. Continuous feeding
• Administered by feeding
pumps at the rate of 20- 50 ml
per hour and then enhanced
gradually as tolerated.
• Such method is generally
preferred for the bed ridden
patients who generally are on
ventilator and intolerant to the
bolus Enteral Nutrition.

8. Possible advantages of continuous methods over
discontinuous methods
• Better tolerance of EN in critical patients; lesser gastric
residual volume (GRV); lesser small intestinal transit time;
lower incidence of diarrhea
• Better glycemic control
• Only method possible in post pyloric feeds due to lack of
reservoir capacity of small intestine
• Lesser incidence of regurgitation & aspiration episodes
• Nutritional target achieved faster
• Lesser weight loss over ICU stay

11. RCTs comparing
cyclic and
continuous feeding

12. Comparison of the metabolic effects of
continuous enteral feeding versus cyclic
• Patients after major head and neck surgery.
• One group was fed continuously for 24 h, the other was fed
only at night, ie, from 1700 to 0900 the next morning.
Campbell IT, Morton RP, Cole JA, Raine CH, Shapiro LM, Stell PM. A comparison of
the effects of intermittent and continuous nasogastric feeding on the oxygen
consumption and nitrogen balance of patients after major head and neck surgery. Am
J Clin Nutr. 1983;38:870–8.

13. Oxygen consumptionmeasured preopretatively
and upto 5 days postoperatively

14. Serum glucose and insulin concentration

15. 24 hour catecholamine excretion
This study favors cyclic EN due to its better
energy efficiency and better nitrogen balance

16. Influence on respiratory and digestive tract
colonization
• Continuous enteral feeding (CEF) has been associated
with decreased gastric acidity presumably stimulating
gastric colonization and ventilator-associated pneumonia
(VAP).
• Almost all patients receiving enteral feeding are colonized
in the stomach with gram-negative bacteria.
• IEF resulted in a slight decrease in intragastric pH without
influencing rates of colonization and infection of the
respiratory tract.
Bonten MJ, Gaillard CA, van der Hulst R, et al. Intermittent enteral feeding: the
influence on respiratory and digestive tract colonization in mechanically ventilated
intensive-care-unit patients. Am J Respir Crit Care Med. 1996;154:394–9.

17. Effect on postoperative gastric function
• Fifty-seven patients who underwent pylorus preserving
pancreatoduodenectomy (PPPD) were studied
van Berge Henegouwen MI, Akkermans LM, et al. Prospective, randomized trial on
the effect of cyclic versus continuous enteral nutrition on postoperative gastric function
after pylorus preserving pancreatoduodenectomy. Ann Surg. 1997;226:677–85.
Cholecystokinin
(CCK) response to
continuous (circles)
and cyclic (triangles)
enteral nutrition,
assessed on the
10th postoperative
day.

18. • Cholecystokinin (CCK) normally inhibits the gastric
emptying.
• Cyclic enteral nutrition reduces the number of days until
patients tolerate a normal diet, thereby reducing hospital
stay.
• Cyclic enteral nutrition is therefore the feeding regimen of
choice in these patients.

19. Influence of the feeding therapy model on
pulmonary complications
Tamowicz B, Mikstacki A, Grzymislawski M. The influence of the feeding therapy
model on pulmonary complications in patients treated under conditions of intensive
therapy. Adv Clin Exp. 2007;16:365–73.
• The prospective randomized study included 40 patients
(13 women and 27 men, aged18–75 years), divided into
two groups: I (n = 20) undergoing intermittent enteral
feeding (IEF) and II (n = 20) with continuous enteral
feeding (CEF).
• Evaluation included daily changes in the pH value of the
gastric contents analyzed

20. • Evaluation of Time Changes in pH of Gastric Contents

21. Intermittent enteral feeding leads
to a statistically insignificant
reduction of the risk of Ventilator
Associated Pneumonia.

22. Intermittent Enteral Feeding: The Influence on
Respiratory and Digestive Tract Colonization
• All mechanically ventilated patients admitted to one of
these wards were eligible for this clinical trial.
• Enteral feeding was administered intragastrically.
• CEF was administered at a continuous rate over a 24-h
period, whereas IEF was administered at a continuous
rate over an 18-h period.
• The amounts of enteral feeding administered and the
residual volumes were monitored daily. In case of gastric
retention of > 400 ml per day, enteral feeding was
diminished or discontinued in both groups.
Bonten MJ, Gaillard CA et al. Intermittent Enteral Feeding: The Influence on
Respiratory and Digestive Trad Colonization in Mechanically Ventilated Intensive-
Care-Unit Patients. Am J Resplr Crit Care Med Vol 154. pp 394-399, 199

23. Median intragastric pH values (with interquartile ranges) in patients with CEF(a) and
IEF(b) in the periods before enteral feeding, during enteral feeding, and between 2:00
and 8:00 A.M. (enteral feeding was discontinued in patients receiving IEF).

24. Percentages of patients colonized with enteric gram-negative bacteria in the
stomach in both study groups according to the numbers of days in the study.

25. Mean volumes of enteral feeding administered in both study groups according to the
numbers of days in the study.

26. • Results of the study indicate that IEF induces only a slight
decrease in intragastric acidity, without influencing
digestive and respiratory tract colonization.
• Almost all patients receiving enteral feeding acquired
gastric colonization with gram-negative bacteria.
Therefore, IEF is
not an effective
measure for
reducing the
incidence of VAP.

27. RCTs comparing continuous and cyclic methods
Cyclic (Advantages)
• Lower pH and reduced bacterial colonization of stomach
• Favorable nitrogen balance
• Less oxygen consumption
• Better glucose control
• Less ICU Mortality
• Less hospital stay
• Less VAP
Continuous (Advantages)
• Less Gastric Residual Volume

28. RCTs comparing
intermittent and
continuous feeding

29. Continuous compared with intermittent tube
feeding in the elderly.
Ciocon JO, Galindo-Ciocon DJ, Tiessen C, Galindo D. Continuous compared with
intermittent tube feeding in the elderly. JPEN J Parenter Enter Nutr. 1992;16:525–8.
Intermittent Continuous
Diarrhea 96.7 % 66.7 % (P = 0.008)
Aspiration 33.3 % 16.7 % (NS)
Clogged tube 16.7 % 50.0 % (P . 0.01)
Agitation, self extubation No significant difference between the
groups
Discrepancy between recommended
and actually provided calories in the 7-
day period
795 ± 25 kcal/day 783 ± 29 kcal day (P
0.1)
Time to administer and Intermittent:
monitor feeding process
48.45 + 11.54 min 46.46 + 11.19 min (P
= 0.25)
Continuous method has
1. Less diarrhea
2. Less aspiration
3. More clogged tube
Time to administer and
calories delivered are similar.

30. Continuous vs discontinuous enteral nutrition:
compared effects on serum lipids andlipoproteins
• Serum lipids, apoproteins, and 24 hour urinary C peptide concentrations
were determined on days 0 and 7.
• The fall during continuous nutrition was significantly greater than that
during discontinuous nutrition for serum cholesterol (14% vs 2.4%; p <.05),
low density lipoprotein cholesterol (17.4% vs 3.9%; p =0.02), and
apoprotein B (19% vs 0.2%; p <.05) concentrations.
• Mean 24‐hour urinary C‐peptide excretion increase was significantly
greater (p <.05) during discontinuous (78%) than during continuous enteral
nutrition (15.6%).
• These results suggest that the cholesterol‐lowering effect of enteral
nutrition was induced mainly by the continuous delivery of the
nutrients and was related to changes in insulin secretion.
Beau P, Labat J. Continuous vs discontinuous enteral nutrition: compared effects on
serum lipids and lipoproteins in humans. JPEN J Parenter Enter Nutr. 1994;18:331–4

31. Prospective randomizedcontrol trial of intermittent
versus continuous gastric feeds
• A prospective randomized trial was conducted in the trauma
intensive care unit in a university Level I trauma center.
• The patients intermittently fed reached the goal faster
and by day 7 had a higher probability of being at goal than
did the patients fed continuously (chi = 6.01, p = 0.01).
• Intermittent patients maintained 100% of goal for 4 of 10
days per patient (95% CI = 3.5-4.4) as compared with the
drip arm goal for only 3 of 10 days per patient (95% CI =
2.7-3.6).
MacLeod JB, Lefton J, Houghton D, et al. Prospective randomized control trial of
intermittent versus continuous gastric feeds for critically ill trauma patients. J Trauma.
2007;63:57–61
Patients from both the intermittent and
continuous feeding regimens reached the goal
during the study period of 7 days but the
intermittent regimen patients reached goal
enteral calories earlier.

32. RCTs comparing intermittent and continuous
Advantages of Intermittent
• Less chance of constipation
• Less chance of clogged tube
• Nutritional target is achieved early
Advantages of continuous
• Less chances of aspiration
• Less chance of weight loss during hospital stay
• Less chance of diarrhea

33. Comparison of continuous vs intermittent nasogastric
enteral feeding in trauma patients
• Eighteen trauma patients [Injury Severity Score (ISS) > or
= 20] were enrolled in the study; 9 received continuous
ENS (CENS) and 9 received intermittent bolus ENS
(IENS).
•
Steevens EC, Lipscomb AF, Poole GV, Sacks GS. Comparison of continuous vs
intermittent nasogastric enteral feeding in trauma patients: perceptions and practice.
Nutr Clin Pract. 2002;17:118–22.
Bolus Continuous P- value
Interruption in EN delivery due
to elevated GRV
55% 33% No P-
value
given% of target delivered cumulatively for 7 days 86.8% 87%
Diarrhea 55% 22%
Aspiration 11.1% 0%
CENS through a nasoenteric
feeding tube may facilitate nutrient
intake with less gastrointestinal
complications

34. RCTs comparing
bolus feeding and
continuous feeding

35. Effects of continuous versus bolus infusion of
enteral nutritionin critical patients
• 28 EN candidates divided into Group I (as a 1-hour bolus
every 3 hours), or Group II (Continuously for 24 hours)
• Nearly half of the total population (46.4%) exhibited high
gastric residues on at least 1 occasion, but only 1
confirmed episode of pulmonary aspiration occurred
(3.6%). Both groups displayed a moderate number of
complications, without differences.
• The two groups were similar in this regard, without
statistical differences
Serpa LF, Kimura M, Faintuch J, Ceconello I. Effects of continuous versus bolus
infusion of enteral nutrition in critical patients. Rev Hosp Clin Fac Med Sao Paulo.
2003;58:9–14.

36. Constant rate enteralnutrition in buccopharyngeal
cancer care. A highly efficient nutritional support
system
• Patients with operable buccopharyngeal cancer and for
whom at least 10 days of NG tube feeding had been
planned
• Based on anthropometrical, biological and immunological
criteria, patients on Constant Rate Enteral Nutrition
(CREN) showed a significant improvement of their post-
operative protein state in comparison with patients on
Fractioned Enteral Nutrition (FEN).
Pichard C, Roulet M. Constant rate enteral nutrition in bucco-pharyngeal cancer care.
A highly efficient nutritional support system. Clin Otolaryngol Allied Sci. 1984;9:209–
14.

37. RCTs comparing bolus and continuous
Bolus (Advantage)
• Improved nitrogen balance
• Less oxygen consumption more energy efficient (Campbell et
al, 1983)
Continuous (Advantages)
• Less chance of weight loss in postoperative period (Pichard
1984)
• Less chance of fall in Serum Albumin
• Less chances of aspiration & diarrhea
• Less chance of feed intolerance

38. Clinical guidelines for methods of delivering enteral
feeding
Canadian Critical Care Nutrition Guidelines
(2013)
“There are insufficient data to make a recommendation on
enteral feeds given continuously vs. other methods of
administration in critically ill patients”

39. National Institute for Health and Care Excellence
(NICE) clinical guidelines (2006)
“For people being fed into the stomach, bolus or
continuous methods should be considered, taking into
account patient preference, convenience and drug
administration. For people in intensive care, nasogastric
tube feeding should usually be delivered continuously
over 16–24 h daily. If insulin administration is needed it is
safe and more practical to administer feeding
continuously over 24 h”

40. • Continuous pump feeding can reduce gastrointestinal
discomfort and may maximise levels of nutrition support
when absorptive capacity is diminished. However,
intermittent infusion should be initiated as soon as possible
(grade A)
• To minimize aspiration, patients should be fed propped up
by 30˚ or more and should be kept propped up for
30 minutes after feeding. Continuous feed should not be
given overnight in patients who are at risk (grade C).

41. Conclusion
• Evidence does not suggest one method to be superior to
others.
• Post-pyloric tube feeding necessitates continuous or
cyclic EN administration due to loss of stomach reservoir
capability.
• In gastric feeding impaired tolerance may require
continuous methods.
• For medically stable patients, intermittent and bolus
feeding methods are preferred due to practical issues,
such as patient mobility, convenience, and cost.