Marie E. Riley, RN, Dip Adult Critical Care.
Staff Nurse, Cardiothoracic Intensive Care Unit, The General Infirmary at Leeds, LeedsHaving decided that nutritional intervention is necessary, perhaps because a patient has swallowing difficulties after a stroke or radical surgery, the nurse must establish access using the most appropriate tube type.
Having decided that nutritional intervention is necessary, perhaps because a patient has swallowing difficulties after a stroke or radical surgery, the nurse must establish access using the most appropriate tube type.
Briggs (1996) states that a nasogastric tube should be suitable for long-term use. It should be possible to check its position and it should preferably be inserted without a guide wire. In essence, there is a simple choice between a wide- or fine-bore tube.
Wide-bore tubes (12Fr or wider, made from PVC) are inserted without a guide wire, are easy to aspirate and are generally visible on X-ray. However, they are associated with a number of problems including reflux rhinitis, oesophageal erosion, upper gastrointestinal bleeds, sphincter incompetence and stricture formation (Briggs, 1996; Kennedy, 1997). The risk of complications will increase if the tubes are left in position for prolonged periods. They should therefore be changed to a fine-bore tube after seven days (Briggs, 1996).
Fine-bore tubes (8Fr, made from polyurethane), are suitable for long-term use (Richardson, 1996) but block more easily than wide-bore tubes. Many require insertion with a guide wire, may be difficult to aspirate and, once the guide wire is removed, they cannot easily be seen on X-ray (Briggs, 1996).
Guide wires should never be inserted into a tube in situ to enable a position check, as this may pierce the tube, causing internal organ damage or leakage of feed into the respiratory pathway. Most authors agree that a fine-bore tube is more comfortable for the patient and has a longer lifespan (ASPEN, 1993; Raper and Maynard, 1992; Richardson, 1996). However, some also advocate use of a wide-bore tube at least in the first instance (Raper and Maynard, 1992; Richardson, 1996).
Positioning and maintaining safety
This paper discusses the accurate placement and maintenance of nasogastric tube position within the context of Guidelines 4, 5 and 6 (Box 1, Part 1). A literature search dating back to the 1980s identified several instances of untoward complication (Aronchick et al, 1984; Duthorn et al, 1998; Hendry et al, 1986; Thomas et al, 1996). The potential for misplacement was quoted at 0.3 to 15% (Thomas et al, 1996), with Methany et al (1998) suggesting that 5% of new tubes were placed in the respiratory tract. Kennedy (1997) also suggests that 60% are dislodged by the patient during the feeding period. While all tubes can be passed incorrectly, the guide wire used to introduce fine-bore tubes may damage internal organs in the process (Murphy, 2001).
ASPEN (1993) proposes that frequent monitoring should include the status and position of the feeding tube. Four-hourly aspiration was already commonplace in the author's unit. In addition, position checks should be undertaken if the patient vomits or retches severely, after suctioning and before drug delivery (Colagiovanni, 1999; Loan et al, 1998; Leeds Teaching Hospitals Trust, 2001).
So far, no 100% accurate test for ascertaining nasogastric tube position has been found (Methany and Clouse, 1997; Methany et al, 1997; Methany et al, 1998). The most common approaches are set out in Box 3. The uncertainty of these methods suggests the need for more than one confirmatory test (Colagiovanni, 1999; D'Souza et al, 1994; Sizer, 1996). Hendry et al (1986) similarly state that there is no ideal method but that the acknowledgement of potential problems will lead to heightened awareness by the health professional.
Each stage of the nutritional intervention process is littered with choices, none more so than in deciding an appropriate treatment regimen (Box 1, Part 1, Guidelines 7 and 8). Verity (1996) identified three main methods of delivering enteral feed, which are listed in Box 4.
Adam (2000) states that no particular delivery method or regimen has, as yet, proved to be best at improving outcomes. He goes on to suggest that protocols have the advantage of selecting patients for whom timely support, matched to an evidenced need, would be beneficial. The algorithm illustrated in Part 1 of this article (Figure 1) uses a flow chart to guide the nurse through this decision-making process.
Amount of nutrition
Tube feeds have been developed with the aim of meeting daily requirements for vitamins and minerals with a balance of carbohydrates, fats and fibre (Abbott Nutrition, 2001). Where deficiencies arise, the type of feed can be changed to optimise serum levels. Calorific requirements have been quoted within a range of 2500 to 4000 calories a day (Young, 1988). However, later work suggests that over-feeding is more dangerous than underfeeding (ASPEN, 1993; Trujillo et al, 1999), causing an increase in CO2 production and making weaning from respiratory support difficult.
Common guidelines emerging from the literature suggest a calorific requirement of 25-35Kcal/Kg/day with 1.5-2g of protein/Kg/day for the critically ill (ASPEN, 1993; Chan et al, 1999; Trujillo et al, 1999; Verity, 1996). These requirements will vary according to the patient and the area of practice, making individual patient assessment vital.
Common problems and their solutions
Several studies identify a failure to give all of a prescribed regimen (Adam, 2000; McClave et al, 1999). There are many reasons for this, some of which are considered below.
Raper and Maynard (1992) state that bowel sounds have no role in assessing suitability for enteral nutrition. It is suggested that they indicate motility not absorption (Loan et al, 1998) and occur mainly because of the passage of food through the gastrointestinal tract. Heyland et al (1995) state that 90% of patients tolerate feeding whether or not bowel sounds are present. Chan et al (1999), however, suggest that feeding is possible in these cases only if the tube is placed beyond the pylorus
It is commonly agreed that there is no scientific evidence to prove residual volumes accurately reflect gastric emptying (Chapman et al, 2000; Loan et al, 1998; Zainal, 1994). Romand and Suter (2000) state that, where high gastric aspirates arise, 'different alternatives exist. The least appropriate is to stop enteral nutrition'. The amount of acceptable aspirate varies according to the institution, report or guidelines.
In our trust, Richardson (1996) advocates the return of only 100ml, while Bratt (1995) suggests an amount double that. Lin and VanCitters (1997) found that with true failure of gastric emptying residual volumes exceeded 1000ml by hour 10. In all other cases such volumes, although large, would plateau (no more than 50ml difference in volumes aspirated five hours apart) within three to 13 hours of starting feeding. It would seem reasonable, in view of this information, to return amounts up to 200ml. Loan et al (1998) sensibly suggest that we look at the ongoing upward or downward trend in such volumes to determine the need for a further review of nutritional intervention.
There are several options to correct the high residual volumes and vomiting associated with enteral feeding. The simple remedies are often the best, and ASPEN (1993) advocates nursing enterally fed patients at a 30° head-up angle. There is strong evidence to show that catecholamines, commonly used in the critically ill, will interfere with gastric emptying, depending on the drug and its dosage (Fruhwald et al, 2000). The study identified dopexamine as 500 times less likely to do this than dopamine. While it may not be possible to withdraw catecholamine use completely, the aim should be to wean patients off them as quickly as their condition allows.
Romand and Suter (2000), among others, advocate the use of prokinetic agents in all enterally fed patients, at least in start-up regimens, to enhance contractility and accelerate intraluminal transit (Schapira et al, 1990). Several potential drugs are identified in the literature, including metoclopramide, erythromycin, domperidone and neostigmine (Bradley, 2001; Chapman et al, 2000; Hinder and San-Garde, 1983).
Most authors agree that diarrhoea is rarely caused by the enteral feed (Loan et al, 1998; Verity, 1996). They suggest discounting other causes, such as antibiotic therapy, infection and predisposing illnesses such as diabetes, first. If in any doubt, stool specimens should be sent for infection screening. Loan et al (1998), along with Raper and Maynard (1992), emphasise that diarrhoea alone should not lead to rate alterations or cessation of feed. Remedies include altering the feed to increase fibre content or reduce osmolarity and symptomatic treatment with drugs such as loperamide (Loan et al, 1998; Raper and Maynard, 1992).
The problems identified above need not stop enteral feeding but should lead the nurse to discuss other options with the multidisciplinary team. Placement of the enteral tube beyond the pylorus is one such option (Romand and Suter, 2000; Trujillo et al, 1999; Zaloga and Marik, 2000). Where it becomes necessary to institute total parenteral nutrition, enteral feeding should be continued at a rate protective to the gut, that is 10-20ml (Bratt, 1995; Raper and Maynard, 1992; Tomkins et al, 2000). Total parenteral nutrition should not be withdrawn suddenly but decreased gradually and stopped when absorption of enteral feed is fully evidenced by low residual volumes and normal bowel action (Griffiths, 2000).
Contamination of feed
Contamination by bacteria such as enterobacter, klebsiella and enterococci may occur even in ready-to-hang feeds (Mathus-Vliegan et al, 2000). So it is vital that nurses take all the precautions possible to reduce the risks. The steps taken will depend on the environment but might reasonably include the following (Leeds Teaching Hospitals Trust, 2000a; 2000b):
- All feeds must be prepared for hanging using an aseptic technique and dressing trolley. Ready-to-hang feeds should be used preferentially and care taken not to touch the silver foil top - the giving set will pierce this as it is attached. Can tops must be cleaned with an alcohol wipe
- Pre-filled containers can be hung for 24 hours and decanted feeds for eight hours
- It is important to limit disconnection of the giving set from the tube. Aspiration, drug delivery and flushes should all be done from its port (Loan et al, 1998), which should be swabbed, allowed to dry and given a clean cap each time
- Water used for flushes must be sterile. If accessed from a bottle, a non-touch technique should be used and the bottle must be clearly marked 'for nasogastric use only'. Syringes and jugs used for flushing and aspiration are single-use items.
In the patient's home, the nurse must ensure that the patient maintains good hygiene techniques, including washing hands before preparing the feed and designating a specific area of the kitchen as the point of preparation.
Monitoring blood glucose - Orr (1992) suggests that enteral feeding causes a rise and fall in gastric emptying rates as glucose levels alter. If this is so, it may be significant in all clinical environments. Schrezenmeir et al (1998) define control as a blood glucose level between 5.5 and 11mmol and simple measures to achieve this are vital. Within the guidelines, therefore, the author has suggested that glucose levels should be monitored closely throughout and insulin given as prescribed.
The process of enteral nutrition is continuous and requires thorough, ongoing assessment and adaptation, which will vary according to the setting. The processes that are considered vital in intensive care are outlined in Guidelines 17, 18 and 19 (Box 1, Part 1). All planned care must be documented in the nursing records and a schedule for monitoring care developed. Table 2 identifies the components considered necessary in ICU. A food chart is maintained for all potentially compromised patients, whether or not enteral feeding is in progress.
Richardson (1996) identifies the need to gradually reduce nutritional support, giving lower daily volumes or overnight feeding before complete cessation. Recovery from critical illness is rarely straightforward and appetite in these patients is, in practice, variable, making daily review necessary to ensure optimum nutritional status.
Monitoring of such support is not limited to the benefits for the individual, and an examination of costs, benefits and complications on a regular basis is essential (Sizer, 1996). Audits on the effectiveness of nutritional intervention are vital irrespective of the care environment.
The provision of adequate nutrition is a complex issue within any environment. Getting it right will promote recovery, while deficits will increase morbidity and mortality, prolong recovery and delay convalescence.
By outlining current thinking it is hoped that this paper goes some way towards guiding the nurse in his or her care provision. The guidelines are the basis for intervention and, for the most part, not cast in stone. Within the author's own environment the safety issues are, however, non-negotiable.
It is vital that all attempts to minimise future risk are taken and this should apply to every practising professional. It is hoped that the guidelines will allow us to provide evidence-based nutritional interventions on a universal basis thereby reducing the problems associated with deficits. While it is not suggested that they fulfil every possible nuance of nutrition provision their establishment will provide the means for future audits of care.
As with much of nursing today, interventions form only part of a cyclical process, which never stops, but continually strives to improve upon what is already in place. There are many aspects of feeding that are not examined here and which deserve future consideration. Many achieve higher calorific intake than is currently shown in the author's clinical area and Griffiths (2000) proposes that requirements effectively double between weeks one and two of intensive care, necessitating input of 35-40Kcal/Kg/day. Could future regimens then use higher rates of delivery, immunomodulated diets or calorie-rich formulae?
There has also been no attempt to look at the oral diet available for patients in ICU although, in practice, it is evident this can be improved, and perhaps this is where our attention should now turn.
Much government time has been spent on examining the NHS and discovering ways of moving forward. In the document Making a Difference (DoH, 1999) the Government identified the value placed upon nurses and nursing in achieving this. The emphasis is on promoting good lines of communication to highlight and share best practice in all areas. It surely starts with nurses examining current care policies to ascertain how they can be improved, sharing their own guidelines and being prepared to examine their implications on a wider basis. As Grimshaw et al (1999) state, even the best guidance will be worthless unless it is read and acted upon.
- Part 1 of this paper appeared in the June 2002 issue of Professional Nurse.
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