Nutrition in critical care

Last Updated: 20 Mar 2023
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Nutrition in Critically Ill Patients, Early Introduction and Maintainance - Nurses Role

Nutrition is very vital in critically ill patients, often the neglected area of critical care where researchers and analysts had been concentrating on for a long time. Guidelines and protocols have been formulated by institutions and organisation, but compliance had been identified as the reason to experience abasement in proper nutrition. Stroud (2007) mentioned that the acute illness aggravates the metabolic rate and abbreviates the pursuance of nutritional elements. I will be reviewing the literatures about the nutrition of critically ill patients, and the role of nurses in intensive care unit (ICU). I have focussed on nutrition of patients in intensive care as it is part of my competency No.5, Hydration and Nutrition. My aim was to find articles regarding adult Intensive care units and adult patients because the knowledge found in this study and the search results can be utilised in my working environment.

Cinahl Database

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My search started with the Boolean search using ‘Ebscohost’ in the Cinahl database, and I used nutrition and critically ill as my search word. My search brought up 1089 articles, which I narrowed down to 507, as I limited my research in between years 2006 - 2013. To be more specific, I applied limitations to the search by limiting the results to be peer reviewed academic journals with full text which included abstracts, and in doing so, brought up 39 articles. Finally, I came up with 22 articles after adding another limitation which was that only articles on adults were used. I was keen to see if it is fruitful to search other databases as well, and so used Ovid as my next database. I narrowed down the search results using the same limitations, leading to the number of results decreasing from ninety-nine to three. The databases Pubmed and Medline brought up similar articles but I found it is easy to access full texts from Cinahl so it did not interest me particularly as my enthusiasm was the involvement of nurses which help in the improvement of evidence based patient care.

Optimising Nutrition

Ovid was a useful resource to get my supporting literatures and was utilised effectively. I found a few articles which helped my process and I will try to point out my findings from those articles. The articles which I would like to discuss are mainly; “Early enteral nutrition and the outcomes of critically ill patients treated with vasopressors and mechanical ventilation” by Khalid et al (2010), “Evaluation of enteral nutrition in critically ill patients receiving mechanical ventilation” by O’Meara et al (2008), and “Optimising nutrition in intensive care units: Empowering critical care nurses to be effective agents of change” by Marshall et al (2012). These articles were published in the American journal of critical care an academic journal.

I chose these articles as each one is discussing different aspects of nutrition and the nurses’ involvement in implementing the use of early enteral nutrition in improving the care of critically ill patients. Critically ill patients have elevated metabolic demand and depend on the provision of nutritional feeding to meet this demand and they are at high risk of insufficient nutritional support. Malnutrition is often a complication in this susceptible group of patients. According to Barr et al (2004), 40% of patients admitted to hospitals become malnourished during the course of stay, 66% of all patients struggle with declination of their nutritional status in the interim and critical illness, further elaborates this occurrence. Malnutrition has been noticed as a reason for the poor outcome of critically ill patients as established by studies and researches.

Wandrag et al(2011), in the study done on 56 patients with enteral feed more than 3 days over two years at a large university hospital established that the patients who had feeding initiated within 24 hours and minimal interruptions had less energy deficit and related complications. Critically ill patients who need Intensive care more than few days develop extensive decrease in lean body mass subsequently resulting in increased mortality, morbidity and length of stay in hospital. Early introduction of sufficient nutrition may not prevent the complication of critical illness but contributes in improving the outcome (Debaveye, Van den Berghe, 2006).

Enteral tube feeding is recommended as early as within 24 hours by the European Society for Clinical Nutrition and Metabolism for all patients in ICUs unless they are expected to be on full oral diet within 3 days (Kreymann et al, 2006). Evidences suggest that enteral feed should be administered in critically ill patients with functional guts after starting mechanical ventilation. (Khalid et al,2006).The authors cited Zalga et al(2003) giving 2 reasons for not starting enteral feed in unstable critically ill patients, gut ischemia and increase in splanchnic blood flow with reduced cardiac output. Atrinian et al (2006) in a study on effects of early enteral feeding suggests that it promotes better enzyme utilisation, avoidance of mucosal atrophy, conservation of gut flora integrity and immune competency. The nutritional support is an indispensable element in critical care and there are different routes to provide nutrition to these patients.

Effect of Early Enteral Feeding on Haemodynamically

Khalid et al (2006) aimed to find the effect of early enteral feeding on haemodynamically unsettled patients who required mechanical ventilation and support with vasopressors . In the study they considered age, sex, race, admitting diagnosis, medications received and the severity of illness on admission to ICU as variables for analysis. Any new changes in respiratory status, new pathogens isolated in blood or sputum culture, any histopathological findings and the mortality rate were included in the data collected for evaluation. Outcome was evaluated using variables like, ICU and hospital mortality, incidence of ventilator associated pneumonia, length of stay in ICU, ventilator free days, and vasopressor free days within first 28 days after first intubation .Patients who had enteral feed commenced within 48 hours of the start of the mechanical ventilation and who had enteral feed started late were the two control group for the particular trial. The patients who had contra indications or gastro intestinal complications were not included in the study.

The analysis of the data comparing different subgroups against the two trial group revealed that hospital mortality of the mechanically ventilated patients were less in the early fed group than the late fed. The effect was apparent in each subgroup. The earlier studies by Marik and Zaloga (2001) and Heyland et al (2003) were cited by the authors mentioning that there was improvement in the outcome and significance of mortality rate .IT needs to be mentioned that all the patients in this study were medical patients with unstable heamodynamic conditions. In the study by Purcell, Davis, Branson (1993) explains that although enteral feeding increases oxygen consumption in the guts, the postprandial hyperaemic response in heamo-dynamically unstable patient’s acts as the complimentary effect and increases oxygen delivery. The metabolic response to critical illness is different to starvation. The need to mobilise tissues for defence and repair to restore homeostasis, wound healing and to combat pathogens is very important.

Hypo Metabolic Phase

There are two stages in this metabolic phase in which hypo metabolic phase where poor tissue perfusion due to low cardiac output and low temperature lasts only 24 hours which is followed by hyper metabolic phase when the metabolic rate increases(Hammarqvist et al, 2009).This theory explains the use of early enteral feed initiated early within24 to 48 hours. The limitations of the study by Khalid et al (2010) were that the caloric intake of the cohort was not considered and the reason for not being fed was not discussed. The early enteral feeding is suggested to improve mortality of critically ill patients treated with mechanical ventilation and vasopressors considering that they have unstable conditions. The evidence based theory that establishment of nutrition as early as within 24 to 48 hours of starting mechanical ventilation have to be further ascertained by delivery of prescribed enteral nutrition without disruption.

The unit where I am working, a trauma specialist centre, the protocol and guidelines of the unit encourage to insert a small bore feeding tube (SBFT) and start enteral feeding as early as possible after confirmation of post pyloric position beginning with small amount and increased each time if the residual volume after 4 hours is less than 250 ml. O’Meara et al (2008) did an observational prospective study in an 18 bedded medical intensive care unit. The subject was to analyse the reasons for under feeding and reduced calorie intake of mechanically ventilated patients. The research was done by collecting data of the patients who were mechanically ventilated with no contraindication for enteral feeding or insertion of small bore feeding tube.

The decisions about insertion of SBFT and initiation of feeding were guided by the multi disciplinary team caring for the patient consisting of critical care physicians, internal medicine residents, registered nurse, pharmacist, and a registered dietician. The time of insertion of SBFT and confirmation of post pyloric position on radiograph, measurement of residual volume, preparation for surgery, procedures, heamodynamic instability, bath or skin care, emesis and others were recorded as the reasons for interruption of enteral feeding. The nursing staff had recorded all these interruptions, duration and reasons.

Nutritional Requirement Estimated

The group concluded that the patients in the study received only 50% of prescribed nutritional requirement estimated for each day. 25.5% of interruptions were related to insertion and confirmation of SBFT where as the high residual volume accounted for only 13.3%,Weaning 11.7% and all other interruptions accounted for 21% which were more frequent but shorter. This study was done in a single institution and they had account for interruptions but did not measure the rate of feeding at any time. The researchers cited Barr et al(2004)and Ferrie, McWilliam (2006) saying that even with advanced techniques and evidence based guidelines critically ill patients only receive 50% of their targeted nutritional requirements. Insertion of feeding tube and its confirmation accounted for the longest time of reduction in feeding time and thereby causing hindrance in providing prescribed nutrition in critically ill. National patient safety agency (NPSA) (2011) suggests to measure pH of the aspirate and if it is 5.5 the tube is considered to be in the right position. When this is not applicable, radiological confirmation is advised causing delays in most occasions due to various reasons. The promptness of radiography and exposure to x ray are questionable.

The magnetic guided nasogastric placement, cortrak can be used to facilitate insertion of SBFT. This method provides correct confirmation and reduced lapse of time in interruption of feed and also cost effective .(Lei et al, 2007).The other reason for reduced nutritional provision was increased residual volume .McLane et al (2005) suggest that residual volumes should not be used to validate the tolerance of enteral feed as it has minimum clinical value. Delayed gastric emptying is a characteristic dysfunction of critically ill due to the effect of the sedation, inotropes and opioid analgesic.

Nguyen et al (2007) suggested use of a combination of prokinetic agents, metachlorpromide and erythromycin single or combined use to overcome the gastric stasis. Reid (2006) exhibited displacement of feeding tube, long periods of fasting for bronchoscopy, tracheostomy, endoscopy, surgical procedures and regular nursing interventions as the other causes of inadequate nutritional support. Reid (2006) suggested gastro intestinal complications like vomiting, abdominal distension; sedation related ileus, sepsis and delayed gastric emptying post head injury as hindrances in the delivery of adequate nutrition resulting in malnutrition. Alberda et al (2009) stays that malnutrition in ICU patient’s results in increased ventilator need, increased infection rates, and impaired wound healing which eventually relates to increased morbidity and mortality and length of ICU stay. The inadequacy of nutritional supplement and related malnutrition are related to delay in commencing feed or interruptions to feeding due to variable reasons described in different studies.


The majority of feed interruptions on ICU were avoidable (Wandrag et al, 2011). Marshall et al(2012)conducted a study to establish the potential role of nurses to raise the levels of nutritional provision by reducing the interruption of feeding and early commencing of enteral feed. The observational study done by the authors specify factors that impact nurses’ nutritional practice and analyse how these factors affect the variables causing an impact in fulfilling the nutritional requirement of ICU patients comparing six published practise guidelines. An important element in nutritional support is knowledge, attitudes and behaviour of the physicians and dieticians. Critical care nurses can influence and utilise the evidence based nutritional practice to bring improvement as nurses are primary point of care in assessment of patients. Nurses have the duty to assess the patient, discuss the treatment plan, monitor and evaluate the response, and to mould the treatment as per the clinical indication. When considering nutritional therapy nurses have an important role in identifying the risk, assessing the suitability, commencing and maintaining the nutritional support and monitoring for potential complications (shneider, 2006).

Evidence based guidelines in provision of enteral nutrition in critical care are available. There is a gap between the recommendations of the guidelines and the actual practice. Heyland et al (2010) suggests that utilising guidelines and recommendations to formulate nurse initiated protocols for starting and increasing the enteral feed to accommodate required calorie intake will improve the nutritional support which help prevention of malnutrition in critically ill patients. McClave et al (2009) points out that nurses are expected to choose the best guideline that is suitable to the value and culture of the particular unit in which they are working. The issue discussed in the study by Marshall et al (2012) is about the controversies of the guidelines available and its usefulness for nurses in achieving the target of 100% nutritional support. The authors lists out the issues where inadequate information provided by the available guidelines regarding nutritional support as tube insertion techniques, placement confirmation, maintaining tube patency, monitoring feed tolerance, and method of administration of feedings, monitoring for complications, minimising risk of aspiration, diarrhoea and withholding feeds for diagnostic tests and procedures.

The study cited Thompson et al (2001) stating that the nurses and other professionals apply the knowledge to solve the issues in a rapidly changing environment. The utilisation of knowledge of clinically accountable professionals must be utilised to facilitate guidelines and protocols in nutritional therapy. The nursing resource person with nutritional expertise can be a key strategy to provide information to form guidelines to improve nutritional therapy. Nutritional support is vital part of critical care leading to prevention of malnutrition in patients in ICU. Malnutrition in critically ill patients increase hospital mortality, morbidity and increase in length of stay in hospital (Khalid et al, 2010).The initiation of enteral feed within 48 hours of critical illness and admission to ICU after establishing mechanical ventilation and vasopressors showed improvement in hospital mortality and length of stay in ICU.

Earlier Theory

The earlier theory that inhibited introduction of enteral tube feeding was that the critical illness cause gut ischaemia and poor absorption is contradicted by Revelly et al (2001)saying that the oxygen delivery improved as enteral nutrients improve blood flow to the gastro intestinal tract ,by the phenomenon known as postprandial hyperaemia. This physiological process helps by improving absorption, decreasing bacterial displacement and inhibits sepsis in heamodynamically unstable patients. The early introduction of enteral feed has been encouraged by different researchers and protocols guidelines are formulated to help the process. In spite of following guidelines (NPSA, 2011) the researches show that only 59% 0f energy requirement of critically ill patients were only supported over first 28 days of ICU stay as per O’Meara et al (2008) . One of the reasons for not initiating or initialising enteral feed within the first 24 to 48 hours have been discussed by authors as difficulty in insertion and confirmation of SBFT. Different protocols suggest different ways of confirmation but there is no clear guidance on how to insert SBFT or how to confirm the post pyloric positioning of the tube. In most cases experience of the nurses play a role .The radiological confirmation by X ray is the advised as the safest medium of confirmation.

The displacement of the tube after initiation of feed is further complicated by aspiration and underfeeding as waiting for X ray each time creates long intervals of absence of feed. Since the introduction of magnetic guided device to insert and confirm the position of SBFT have resolved these issues .National patient safety agency (2007) have confirmed this as a safer method and promotes provision of early enteral nutrition. Another issue was the interruptions of feeding due to causes like problems due to SBFT, increased gastric residual volume and interventions such as weaning, surgical procedures, and nursing procedures and gastro intestinal disturbances like vomiting and abdominal distension. High residual volume had been the reason for the longest interruption. The use of metachlorpamide and erythromycin each individually or together has been supported (Nguven et al, 2011). The researches by Davies et al (2002), Montejo (2002) have used residual volume as the sign of feed tolerance but the study by O’Meara et al(2008) mentioned that gastric residual volume had no significance in the absorption supporting the conclusion of Reid et al (2006).The authors even feel that measuring residual volumes consumes nurse’s time and interrupts feeding.

Evaluation and Updating of Current Protocols

The suggestion is to use better markers like bowel sounds or abdominal distensions should as indicator of feed tolerance. This critical evaluation increases the need in evaluation and updating of current protocols and guidelines to improve nutritional support and reducing the rate of malnutrition and improving patient outcome. The study by Marshall et al (2012) explores the nurses ‘role as agents of change in optimising nutrition in ICU. Critical care nurses have a definite role in ensuring that prominent initiation and maintenance of nutritional support. Nurses can play an important role in formulating guidelines based on new evidences to make sure that the quality care is provided at all instances (NMC, 2008). The nurses have a responsibility to recognise the gap in research in relation to nutritional support, actively participate in the development of integrated nutrition resources in co-operation with the multidisciplinary team and valuate the obstacles to evidence based nutritional approach specific to the particular area. Nurses can use social interaction to circulate the up-to-date guidelines in the clinical area.

Participation in multidisciplinary team to formulate clinical practice and to disseminate the knowledge by education and research to improve the nutritional support of the patients in ICU which will help reduce mortality, morbidity and length of stay in ICU. The unit where I practice critical care nursing promote use of an algorithm to calculate calorie requirement to ensure the feeding is initiated and maintained at all possible occasions .The audit done in the critical care unit which I participated showed that in 30% of patients, nurses calculated the target rate and 30% of patients achieved the calculated target rate within 8 hours. The important thing which we noticed was that 66% of the target volume was delivered. The main problems we still face are interruptions due to preparation for surgery. The change in the practice was not to starve the patient unless the patients were going to have procedure involving gastro intestinal system like abdominal surgery or airway to avoid aspiration.


Using catch up rate to achieve target volume will replace volume for the period missed. Using nasogastric bridles (Webb et al, 2012) ensures the stability of the nasogastric tube avoiding interruptions due to repeated replacement of SBFT and related radiation for confirmation. The validity of using gastric residual volume in reduction of feed volume is still an area needs further research. The nutritional support is very vital in critically ill and supplementing in appropriate time and required volume and accurate calorie will make a difference in the outcome of the critical illness and the nurses have an important role to promote this outcome.

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Nutrition in critical care. (2018, Jul 06). Retrieved from

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