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Perioperative nutritional support
BASIC SCIENCE
Perioperative nutritional support
Nutritional assessment This can be difficult in practice as there is no ‘gold standard’ which can be applied across all patient groups. A nutritional assessment should include the criteria listed in Table 2. Anthropometric measurements such as mid arm circumference (MAC), triceps skinfold thickness (TSF) and mid arm muscle circumference (MAMC) are used to measure lean body mass and body fat stores. It is generally used in long-term nutritional support as a method of monitoring changes in nutritional status.
Marion J O’Connor Julie I Dehavillande
Abstract Preoperative nutrition support
Malnutrition is a common and often unrecognized problem which increases the risk of postoperative morbidity and mortality. To identify those at risk, all patients should be screened on admission to hospital using a validated reliable tool (e.g. the malnutrition universal screening tool, MUST). Minimal perioperative fasting, carbohydrate loading and early enteral feeding all reduce postoperative complications and enhance recovery. Refeeding syndrome needs to be diagnosed and treated prior to initiating feeding. Enteral is the preferred route of feeding as it provides nourishment directly to the gut. If parenteral nutrition (PN) is indicated then close monitoring and strict guidelines need to be followed to reduce the risk of metabolic complications and line sepsis. PN is an integral part of the management of high output enterocutaneous fistulae (ECF). A high output ileostomy causes malnutrition and electrolyte abnormalities. Alterations to diet and fluids alongside medical management are necessary to reduce the high output stoma.
Surgical patients in particular are an at-risk group as surgery like any injury imposes a stress on the body. The metabolic response to this stress is characterized by a hyper-metabolism and catabolism mediated by hormones and cytokines. This is designed to mobilize tissues for defence and repair mechanisms. The magnitude and duration of this response are related to the severity of the stress. Obese surgical patients are at greater risk as the mortality from surgery is higher in obese compared to non-obese individuals. Contributory factors are hyperglycemia, hypertension, and precipitation of cardiovascular events. The perioperative complications of obesity result from respiratory failure, impairment in fibrinolysis, a hypercoagulable state, and decreased resistance to infection. With catabolic illness, lean body mass may waste rapidly despite the presence of excess adipose tissue. The benefit of early detection of malnutrition and subsequent provision of nutrition support is to reduce the risk of postoperative complications. This will be achieved by minimizing negative protein balance so as to maintain muscle mass, immune and cognitive function and enhance postoperative recovery. To ensure the patient is in an optimal nutritional state, all elective surgery patients should have a nutritional assessment performed at the pre-assessment clinic. This could be as simple as a weight, height, body mass index (BMI), % weight loss and identification of any factors which may affect nutritional intake prior to surgery. For high-risk patients, a referral should then be made to a dietitian who will carry out a more in-depth assessment and arrange the provision of nutrition support as indicated. If possible, especially in high-risk patients, surgery should be postponed until there is an improvement in the nutritional status.
Keywords Carbohydrate loading; enhanced recovery after surgery (ERAS); fistulae; high output stoma; ileus; insulin resistance; malnutrition
The adverse effects of malnutrition in surgical patients have been documented from as early as 1936.1 Despite this, it remains a common problem with an incidence of w50%, exacerbated by hospital stay.2 A suboptimal dietary intake for >14 days is associated with a high morbidity and mortality. To prevent complications (see Table 1) associated with malnutrition, nutrition screening, assessment and support must become an integral part of the multidisciplinary care of the surgical patient. Early detection is vital, therefore, all patients should be screened on admission using a validated reliable tool, for example the Malnutrition Universal Screening Tool (MUST). This should be repeated at least once a week during their hospital stay. The tool should contain locally agreed care plans that can then be instigated to prevent and/or treat malnutrition.
Perioperative nutrition support Once the nutritional status is optimized preoperatively, measures to reduce the stress induced by surgery and facilitate the return of
Consequences of malnutrition Impaired immune function / infections Delayed wound healing Increased risk of postoperative complications Muscle wasting and weakness which affects: C respiratory function / chest infections C cardiac function / heart failure C mobility / [deep vein thrombosis/pulmonary embolism and pressure sores Apathy, depression and neglect
Marion J O’Connor MSc BSc(Hons) RD is a Specialist Dietitian in Intestinal Failure and Total Parenteral Nutrition at the Oxford Radcliffe Hospitals NHS Trust, Oxford, UK. Conflicts of interest: none declared. Julie I Dehavillande BSc(Hons) RD is a Dietetic Team Leader for Critical Care/Neurosciences at the John Radcliffe Hospital, Oxford, UK. Conflicts of interest: none declared.
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Table 1
413
Ó 2010 Elsevier Ltd. All rights reserved.
BASIC SCIENCE
Criteria for nutritional assessment History
Disease status
Functional assessment Laboratory tests
Fluid balance
Identify any pre-admission factors which have led to malnutrition Clinical condition Weight (only useful in the absence of oedema or dehydration) Height Body mass index (BMI) ¼ weight/height (kg/m2) BMI < 18 ¼ underweight BMI 20e25 ¼ normal weight BMI > 30 obese Weight loss history %weight loss ¼ usual weight current weight/usual weight 100 a weight loss of >10% in the preceding 6 months is significant Appetite Food intake history Gastrointestinal symptoms Fever Medical and drug history Temperature Inflammatory markers e.g. C-reactive protein (CRP) Nutrient losses e.g. wounds, fistulae, ileostomy etc Muscle strength using hand dynamometry which correlates well with outcome in surgical patients Inflammatory markers Albumin e as this is an acute phase protein, it must be interpreted in conjunction with CRP Prealbumin Transthyretin Transferrin Nitrogen balance Vitamins, minerals and trace elements especially where deficiencies are suspected Examine for dehydration or oedema Monitor daily weights to record changes in fluid balance Measure urea, creatinine, and electrolyte levels as clinically indicated
Table 2
function should be instigated. The enhanced recovery after surgery program (ERAS) provides guidance on how to achieve this (Table 3). The aspects of this program that are relevant from a nutritional perspective are reduced pre- and postoperative fasting, carbohydrate loading, early mobilization and early feeding postoperatively.
One of the main observations during the catabolic response to injury is the development of insulin resistance. It can result in dehydration, weight loss, fatigue, poor wound healing, increased risk of infectious complication and a reduction in lean body mass as a result of increased nitrogen losses. The magnitude, type and duration of surgery as well as perioperative blood loss are all factors which contribute to its development. It can be present for up to 10 days postoperatively.3 The recommendations for minimizing postoperative insulin resistance are listed in Box 1.
The multimodal approach to enhance recovery after surgery (ERAS) Pre-admission counselling
Avoidance of fluid and sodium overload No bowel prep Warm environment Reduced fasting times No drains Carbohydrate loading Early mobilization Mid-thoracic epidural anaesthesia Early removal of catheters Short-acting anaesthetic agent Non-opiate analgesia Short incisions Stimulate gut motility No nasogastric tubes for Perioperative nutrition gastric drainage
Factors to reduce postoperative insulin resistance C C C C
Table 3
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Reduce fasting preoperatively Carbohydrate loading preoperatively Consider operative procedure i.e. minimally invasive Early postoperative nutrition
Box 1
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BASIC SCIENCE
nervosa, those with minimal intake for >7 days, should have their electrolytes (i.e. sodium, potassium, calcium, magnesium and phosphate) checked and repleted prior to feeding. Thiamine which is an essential coenzyme in carbohydrate metabolism should be given 30 minutes before commencing the feed. The feed should provide 5e20 kcal/kg per day until stable. Once stable, the feed can be increased to meet full nutritional requirements.
In recent years, traditional guidelines to fast patients preoperatively have been abandoned as there is lack of evidence that it reduces the risk of aspiration. There is now a much stronger evidence base showing the benefit of allowing free fluid intake up to 2 hours before surgery. Consequently many anaesthesiology societies have changed their guidelines regarding fasting. Food is now allowed up to 6 hours before surgery and clear oral fluids or carbohydrate loading drinks up to 2 hours before surgery.
Route of nutritional support Preoperative carbohydrate loading
As a general rule of thumb ‘if the gut works use it’. Enteral feeding where possible is superior to parenteral feeding as it delivers nutrients to the gut and maintains gut integrity by preventing gut atrophy and subsequent bacterial translocation. In comparison to PN, it is cheaper, safer and easier to administer as it does not require specially trained staff. It can be administered via a nasogastric, nasojejunal, jejunostomy or gastrostomy feeding tube. If gastric stasis is an issue, then nasojejunal feeding should be commenced. In comparison with enteral nutrition (EN), parenteral nutrition (PN) is expensive, unphysiological and there is a risk of metabolic disturbances and sepsis, it requires close monitoring of electrolytes and it requires trained staff to administer. Despite this, PN is vital in the management of certain clinical conditions, for example short bowel syndrome, fistulae, intestinal failure, postoperative ileus, mucositis, dysmotility. There is little benefit to providing PN for shorter than 7 days and this must be a consideration when the referral is made. PN contains glucose often present in high concentrations, making it an ideal medium for the growth of bacteria, making it vital that it is administered aseptically via a dedicated lumen identified at the time of insertion of the central line and clearly marked as such. If all lumens have been used then a new line should be inserted. Manipulation of the line can increase the risk of infection, so only trained staff should make connections or disconnections. In extenuating circumstances, if the line has to be used for fluids or drugs other than PN, this should be done aseptically and the nutrition team and surgical teams informed. Electrolyte disturbances are common in patients receiving PN, but can be corrected by appropriate adjustment of TPN electrolyte content or by separate intravenous supplementation. If the liver function tests (LFTs) become acutely abnormal, the PN should not be discontinued, but the source of the problem identified, for example sepsis, hepatotoxic drugs etc. However, PN prescriptions should be reviewed in patients receiving longterm PN whose LFTs become abnormal as this may be a sign of overfeeding. Wherever possible, a small amount of enteral feeding at 30 ml/hour (trophic feeding) should be given alongside the PN. This will prevent gut atrophy and promote stimulation of the entero-hepatic circulation.
Carbohydrate loading ensures that the liver and muscle glycogen stores in the body are replete thus optimizing the metabolic response to surgery. It improves the postoperative recovery period by its effects on reducing insulin resistance, improving protein balance, preservation of lean body mass and muscle strength and reducing length of hospital stay. It involves the use of specially formulated carbohydrate drinks which leave the stomach rapidly as they have a low osmolality. They achieve an insulin response similar to that which is seen occurring after a normal meal. This ensures that the patient is in the ‘fed’ or anabolic state rather than the ‘fasted’ state prior to surgery. Insulin sensitivity is increased when they are given before the onset of the stress. These drinks can be taken up to 2 hours before surgery, assuming gastric emptying is not impaired.
Early enteral feeding Historically, postoperative feeding was often delayed until the passage of flatus and the presence of bowel sounds. There was also a fear that early feeding would cause a breakdown of the bowel anastomosis. The ERAS program has challenged this and several researchers have illustrated that both flatus and bowel sounds return sooner in those who are fed in comparison to those starved postoperatively. The incidence of anastomotic breakdown in the fed group was not significantly greater than the fasted group. Patients should be offered nutritional supplements or diet as tolerated from day 1 to 2 post surgery. If a postoperative ileus occurs, then a nasogastric tube should be inserted for drainage and intravenous feeding by day 7e10. Patients failing to meet their nutritional requirements postoperatively should be referred to a dietitian who can advise on nutrition support. If artificial nutrition support is indicated, this can be administered via a nasogastric or nasojejunal feeding tube. Before feeding commences, the patient’s risk of refeeding syndrome should be determined.
Refeeding syndrome Refeeding syndrome is common, but often goes unrecognized. It is defined as the potentially fatal shifts in fluids and electrolytes that may occur in malnourished patients receiving artificial feeding. It is caused by the metabolic and hormonal changes which occur after rapid feeding following a prolonged period of minimal intake or starvation.4 The metabolic effects of refeeding syndrome are hypokalemia, hypophosphatemia, hypomagnesemia, hypocalcemia and vitamin deficiencies. Those identified at high risk, for example alcoholics, anorexia
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Postoperative nutrition support on the intensive therapy unit Patients admitted to the intensive therapy unit (ITU) postoperatively generally require support of one or more organs, particularly the respiratory system, necessitating ventilatory support or intensive and invasive monitoring. Initially postoperatively the priority is resuscitation and stabilization of the patient. Following this, there is evidence to
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BASIC SCIENCE
available all with their own limitations.6 See Table 4 for examples of types of equations.
support that commencing early enteral nutrition (EN) within 24 hours is associated with a significant reduction in mortality and pneumonia.5 The hypothesis for this is that early EN preserves the gut associated lymphoid tissue and barrier function, thereby reducing the risk of translocation of gut organisms.
ITU feeding protocols Feeding protocols are widely used on ITU to promote the early and safe provision of enteral nutrition. Studies show that protocols are associated with improved enteral feed delivery.7 Protocols recommend incremental feed delivery rates based on Gastric Residual Volume (GRV) threshold levels (aspiration of gastric contents with a syringe), which may vary between 120 and 500 ml on different units. GRVs are used as a marker of gastric emptying. Rationale for withholding feed if levels are high is based on the assumption that aspiration of gastric contents is associated with pneumonia. Limitations to this rationale include: GRV thresholds do not consider gastric and salivary secretions which may equate to 188 ml/hour. Reliable measurements can be difficult to obtain. Poor correlation between GRVs and other measures of gastric emptying, for example paracetamol absorption test. Poor association between higher GRV measurements and pneumonia. GRVs should thus be interpreted with caution especially as patients often do not receive their full feed prescription for periods of starvation for theatre, investigations, planned tracheal extubation etc. Hypocaloric feeding can be associated with negative outcomes particularly infection.8 Where GRVs are persistently high, protocols advocate the prescription of prokinetic drugs such as metoclopramide and/or low doses of the antibiotic erythromycin. If this is unsuccessful then the placement of a single or double lumen nasojejunal tube should be considered. The latter allows feeding into the jejunum with concurrent drainage of gastric contents.
Goals of nutrition support on ITU Attenuate loss of lean body mass in order to support recovery and weaning from the ventilator. Weight loss and muscle wasting are unpreventable during the acute phase of illness even with adequate nutrition (Frankenfield 1997). Avoid risks of under feeding which include impaired immune function, infection risk, poor wound healing, muscle wasting and prolonged ventilatory wean. Avoid risks of overfeeding which include azotaemia, hyperglycaemia, hepatic dysfunction and hypercapnia, which may hinder weaning. Avoid metabolic complications such as refeeding syndrome (see section above).
Nutritional assessment of ITU patients This can be extremely difficult in an ITU setting, unless the patient has been assessed prior to an elective procedure. Anthropometric measurements are often not possible to undertake in an unstable, sedated patient and if obtainable would be inaccurate as fluid retention can cause significant weight increases over short periods of time. Biochemical markers, for example albumin, are also inaccurate due to reduced synthesis, increased degradation, transcapillary escape and dilution effects.
Nutritional requirements of the ITU patient There is much debate regarding determining appropriate energy provision for ITU patients. They are an extremely heterogeneous population of patients from a range of specialities. In addition to this, the presence of large wounds, infection, sepsis, differing levels of sedation, paralysis and mode of respiratory support can affect energy requirements. The gold standard for establishing energy requirements is by measuring oxygen consumption and carbon dioxide output using an indirect calorimeter. Unfortunately due to lack of availability of equipment and cost this is often only used in research settings. In practice prediction equations are used. There are more than 200 different equations
Feeding regimens on ITU Once requirements have been determined, a feed prescription is devised to best meet these, detailing the volume to be given and rate of delivery over a 24-hour period. Often polymeric standard fibre or non-fibre feeds are used which contain varying levels of kilocalories (kcal) and protein. Non-feed sources of energy also need to be considered (e.g. the sedative propofol is based in a lipid emulsion and provides 1.1 kcal/ml).
Equations used for calculating feeding regimes Type of equation Regression equations derived from healthy populations to which stress factors and activity factors for patients conditions are added Regression equations derived from specific intensive therapy unit patient populations Equations based on physiological variables e.g. respiratory rate, tidal volume, body temperature
Examples Schofield, Harris-Benedict
Limitations Use of stress factors is open to error
Ireton-Jones Penn State
May not apply to all patients, check reference population used Very complex Variables change throughout the day
Swinamer
Table 4
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Specialist feeds on ITU Immune modulating feeds Immune modulating enteral feeds contain different combinations and doses of omega-3 fatty acids, arginine, glutamine and nucleotides. These formulations may benefit specific surgical patients but some reports that arginine may worsen mortality in sepsis have limited their use.9 Renal feeds Low-electrolyte/low-volume feeds are available for patients with renal failure who are fluid restricted or whose electrolyte levels are deranged. If a patient is receiving continuous renal replacement therapy then a standard feed is preferential particularly because renal feeds tend to be lower in protein and haemofiltration can result in significant nitrogen losses.
Figure 2 Large open abdominal wound after intensive nutrition and stoma therapy support.
Nutritional management of postoperative complications Postoperative ileus From as early as 1906, postoperative ileus was recognized as a frequent complication after abdominal surgery. Despite this, an understanding of the cause of ileus and the means to prevent it are still incomplete. Ileus invariably leads to malnutrition, prolonged hospital stay, and is associated with an increase in morbidity. The patient with a postoperative ileus for >7 days should be treated with PN until the ileus has resolved.
and protein requirements cannot be met via diet and sip feeds, a high-protein feed should be administered via a nasogastric feeding tube.
Enterocutaneous fistulae Gastrointestinal fistulae can form due to surgery, disease or trauma. Enterocutaneous fistulae (ECF), defined as abnormal communications between bowel and skin, are among the most challenging conditions managed by the general surgeon. The mortality from an enterocutaneous fistula remains 10e30% due to the often present complications of sepsis, malnutrition and deranged electrolytes. Overall management consists of controlling sepsis, optimization of nutritional state, wound care, assessment of fistula anatomy, appropriate timing of surgery and surgical strategy (the SOWATS guideline).10 Application of the SOWATS guidelines allows a favourable outcome after a short convalescence period. Abdominal wall defects and preoperative hypoalbuminemia are important prognostic variables. Nutrition support is integral in the management of fistulae in preventing malnutrition and in the provision of nutrients to promote healing. In conservative management, the bowel is rested by putting the patient nil by mouth (NBM) and PN is commenced. This will also allow the basal fistula output to be measured. Fistula output should be monitored daily. Once fistula output is <200 ml, a low-residue diet is introduced and the effect of this on fistula output is monitored. If no increase in output occurs then diet is increased further to meet full nutritional requirement and TPN is weaned off accordingly. On the other hand, after 30e40 days if the output remains high >500 ml, PN is continued until an optimal time is reached when surgery can be performed. With a high output fistula, additional fluid and electrolytes will need to be added to PN or given intravenously in addition to PN. If optimal timing for surgery (3e6 months from previous surgery) has not been reached consideration should be given to discharging the patient to their own home on PN.
Surgical wounds For optimal wound healing to occur, the body needs to be well nourished. This will enable synthesis of acute phase proteins, white cells, fibroblasts collagen and other tissue components which can be delivered to the wound to promote healing. If these are not present, wound healing will be delayed and dehiscence or anastomotic breakdowns may occur. Large open abdominal wounds (Figures 1 and 2) will require intensive nutrition support. Protein intake should be optimized as losses from larger open abdominal wounds are often underestimated. There are also electrolyte, vitamin and mineral losses. Vitamin and mineral levels should be checked especially zinc and vitamin C. If calorie
High output stomas High output stomas lead to dehydration and metabolic disturbance (most commonly hyponatraemia, hypokalaemia
Figure 1 Large open abdominal wound.
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Steps involved in managing fluid loss from stomas STEP 4
STEP 1 • Review history (number of bags emptying/day, associated pain, etc) • Ask dietitian to review oral intake • Check drug chart (prokinetics, proton pump inhibitor dose, anti-diarrhoeal dose, lactose-containing medication) • Consider cause: – inappropriate diet – gastric hypersecretion – bacterial overgrowth – partial obstruction (parastomal hernia, adhesions, stomal stricture) – prestomal ileitis – recurrent Crohn’s – peristomal sepsis – short bowel – coincidental/undiagnosed disease (villous atrophy, hyperthyroidism, h ypolactasia, pancreatic insufficiency, dysmotility) • Arrange appropriate investigations: • Trial of empirical therapy: – dietary adjustment to a low-fibre, low-sugar diet and isotonic fluids – omeprazole 40–80 mg once daily – metronidazole 400 mg three times daily for 1 week – loperamide 4 mg four times daily – codeine 60 mg four times daily
Calculate stoma output while on isotonic fluids
<1200 ml/day
Go to Step 5
Measure impact, in succession, of i. omeprazole 80 mg once daily ii. add loperamide 8 mg four times daily iii. add codeine 60 mg four times daily iv. add octreotide 100 µg twice daily
Output <1500 ml/day
STEP 2 • • • • •
>1200 ml/day
Establish basal output by approach below 48–72 hours on intravenous fluids AND nil by mouth Monitor electrolytes (Na, K, Mg) daily Review by dietitian If basal output >1200 ml/day, then it is very unlikely that the patient will manage without intravenous fluids at home. Get advice from parenteral nutrition team.
Go to Step 5
Output >1500 ml/day
Anticipate and plan for long-term intravenous fluids or parenteral nutrition
STEP 3
STEP 5
• For 24–48 hours, establish the effect of isotonic fluids, which contain [Na + ] >90 mmol as net water absorption by the jejunum only occurs when luminal [Na + ] >90 mmol. The dietitian should explain to the patient and nursing staff the role of isotonic fluids and how they are constituted • Document fluid intake and ileostomy output.
• Establish effect of solid food, supervised by dietitian.
Figure 3 REFERENCES 1 Studley H. Percentage of weight loss. A basic indicator of surgical risk in patients with chronic peptic ulcer. JAMA 1936; 106: 458e60. 2 McWhirter JP, Pennington CR. Incidence and recognition of malnutrition in hospital. BMJ 1994 Apr 9; 308: 945e8. 3 Thorell A, Nygren J, Ljungqvist O. Insulin resistance: a marker of surgical stress. Curr Opin Clin Nutr Metab Care 1999 Jan; 2: 69e78. 4 Mehanna HM, Moledina J, Travis J. Refeeding syndrome: what it is, and how to prevent and treat it. BMJ 2008 Jun 28; 336: 1495e8.
hypomagnesaemia and uraemia). Advice to drink extra fluids can make the situation worse, especially if these are hypo- or hypertonic fluids. Fluids flush the small intestinal contents through and exacerbates dehydration and electrolyte losses. As food and fluids can promote secretion and increase volume, it is important to assess daily food and fluid intake. The steps defined in Figure 3 are necessary to establish and correct the cause, with the aim of achieving a stoma effluent volume of <1200 ml/day. A
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5 Doig GS, Heighes PT, Simpson F, Sweetman EA, Davies AR. Early enteral nutrition, provided within 24 h of injury or intensive care unit admission, significantly reduces mortality in critically ill patients: a meta-analysis of randomised controlled trials. Intensive Care Med 2009 Dec; 35: 2018e27. 6 Walker RN, Heuberger RA. Predictive equations for energy needs for the critically ill. Respir Care 2009 Apr; 54: 509e21. 7 McClave SA, Martindale RG, Vanek VW, et al. Guidelines for the provision and assessment of nutrition support therapy in the adult critically ill patient: Society of Critical Care Medicine (SCCM) and American Society for Parenteral and Enteral
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Nutrition (A.S.P.E.N.). JPEN J Parenter Enteral Nutr 2009 MayeJun; 33: 277e316. 8 Villet S, Chiolero RL, Bollmann MD, et al. Negative impact of hypocaloric feeding and energy balance on clinical outcome in ICU patients. Clin Nutr 2005 Aug; 24: 502e9. 9 Heyland DK, Novak F. Immunonutrition in the critically ill patient: more harm than good? JPEN J Parenter Enteral Nutr 2001 MareApr; 25(2 suppl): S51e5 [discussion S5e6]. 10 Visschers RG, Olde Damink SW, Winkens B, Soeters PB, van Gemert WG. Treatment strategies in 135 consecutive patients with enterocutaneous fistulas. World J Surg 2008 Mar; 32: 445e53.
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Perioperative nutritional support
Nutritional assessment This can be difficult in practice as there is no ‘gold standard’ which can be applied across all patient groups. A nutritional assessment should include the criteria listed in Table 2. Anthropometric measurements such as mid arm circumference (MAC), triceps skinfold thickness (TSF) and mid arm muscle circumference (MAMC) are used to measure lean body mass and body fat stores. It is generally used in long-term nutritional support as a method of monitoring changes in nutritional status.
Marion J O’Connor Julie I Dehavillande
Abstract Preoperative nutrition support
Malnutrition is a common and often unrecognized problem which increases the risk of postoperative morbidity and mortality. To identify those at risk, all patients should be screened on admission to hospital using a validated reliable tool (e.g. the malnutrition universal screening tool, MUST). Minimal perioperative fasting, carbohydrate loading and early enteral feeding all reduce postoperative complications and enhance recovery. Refeeding syndrome needs to be diagnosed and treated prior to initiating feeding. Enteral is the preferred route of feeding as it provides nourishment directly to the gut. If parenteral nutrition (PN) is indicated then close monitoring and strict guidelines need to be followed to reduce the risk of metabolic complications and line sepsis. PN is an integral part of the management of high output enterocutaneous fistulae (ECF). A high output ileostomy causes malnutrition and electrolyte abnormalities. Alterations to diet and fluids alongside medical management are necessary to reduce the high output stoma.
Surgical patients in particular are an at-risk group as surgery like any injury imposes a stress on the body. The metabolic response to this stress is characterized by a hyper-metabolism and catabolism mediated by hormones and cytokines. This is designed to mobilize tissues for defence and repair mechanisms. The magnitude and duration of this response are related to the severity of the stress. Obese surgical patients are at greater risk as the mortality from surgery is higher in obese compared to non-obese individuals. Contributory factors are hyperglycemia, hypertension, and precipitation of cardiovascular events. The perioperative complications of obesity result from respiratory failure, impairment in fibrinolysis, a hypercoagulable state, and decreased resistance to infection. With catabolic illness, lean body mass may waste rapidly despite the presence of excess adipose tissue. The benefit of early detection of malnutrition and subsequent provision of nutrition support is to reduce the risk of postoperative complications. This will be achieved by minimizing negative protein balance so as to maintain muscle mass, immune and cognitive function and enhance postoperative recovery. To ensure the patient is in an optimal nutritional state, all elective surgery patients should have a nutritional assessment performed at the pre-assessment clinic. This could be as simple as a weight, height, body mass index (BMI), % weight loss and identification of any factors which may affect nutritional intake prior to surgery. For high-risk patients, a referral should then be made to a dietitian who will carry out a more in-depth assessment and arrange the provision of nutrition support as indicated. If possible, especially in high-risk patients, surgery should be postponed until there is an improvement in the nutritional status.
Keywords Carbohydrate loading; enhanced recovery after surgery (ERAS); fistulae; high output stoma; ileus; insulin resistance; malnutrition
The adverse effects of malnutrition in surgical patients have been documented from as early as 1936.1 Despite this, it remains a common problem with an incidence of w50%, exacerbated by hospital stay.2 A suboptimal dietary intake for >14 days is associated with a high morbidity and mortality. To prevent complications (see Table 1) associated with malnutrition, nutrition screening, assessment and support must become an integral part of the multidisciplinary care of the surgical patient. Early detection is vital, therefore, all patients should be screened on admission using a validated reliable tool, for example the Malnutrition Universal Screening Tool (MUST). This should be repeated at least once a week during their hospital stay. The tool should contain locally agreed care plans that can then be instigated to prevent and/or treat malnutrition.
Perioperative nutrition support Once the nutritional status is optimized preoperatively, measures to reduce the stress induced by surgery and facilitate the return of
Consequences of malnutrition Impaired immune function / infections Delayed wound healing Increased risk of postoperative complications Muscle wasting and weakness which affects: C respiratory function / chest infections C cardiac function / heart failure C mobility / [deep vein thrombosis/pulmonary embolism and pressure sores Apathy, depression and neglect
Marion J O’Connor MSc BSc(Hons) RD is a Specialist Dietitian in Intestinal Failure and Total Parenteral Nutrition at the Oxford Radcliffe Hospitals NHS Trust, Oxford, UK. Conflicts of interest: none declared. Julie I Dehavillande BSc(Hons) RD is a Dietetic Team Leader for Critical Care/Neurosciences at the John Radcliffe Hospital, Oxford, UK. Conflicts of interest: none declared.
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Table 1
413
Ó 2010 Elsevier Ltd. All rights reserved.
BASIC SCIENCE
Criteria for nutritional assessment History
Disease status
Functional assessment Laboratory tests
Fluid balance
Identify any pre-admission factors which have led to malnutrition Clinical condition Weight (only useful in the absence of oedema or dehydration) Height Body mass index (BMI) ¼ weight/height (kg/m2) BMI < 18 ¼ underweight BMI 20e25 ¼ normal weight BMI > 30 obese Weight loss history %weight loss ¼ usual weight current weight/usual weight 100 a weight loss of >10% in the preceding 6 months is significant Appetite Food intake history Gastrointestinal symptoms Fever Medical and drug history Temperature Inflammatory markers e.g. C-reactive protein (CRP) Nutrient losses e.g. wounds, fistulae, ileostomy etc Muscle strength using hand dynamometry which correlates well with outcome in surgical patients Inflammatory markers Albumin e as this is an acute phase protein, it must be interpreted in conjunction with CRP Prealbumin Transthyretin Transferrin Nitrogen balance Vitamins, minerals and trace elements especially where deficiencies are suspected Examine for dehydration or oedema Monitor daily weights to record changes in fluid balance Measure urea, creatinine, and electrolyte levels as clinically indicated
Table 2
function should be instigated. The enhanced recovery after surgery program (ERAS) provides guidance on how to achieve this (Table 3). The aspects of this program that are relevant from a nutritional perspective are reduced pre- and postoperative fasting, carbohydrate loading, early mobilization and early feeding postoperatively.
One of the main observations during the catabolic response to injury is the development of insulin resistance. It can result in dehydration, weight loss, fatigue, poor wound healing, increased risk of infectious complication and a reduction in lean body mass as a result of increased nitrogen losses. The magnitude, type and duration of surgery as well as perioperative blood loss are all factors which contribute to its development. It can be present for up to 10 days postoperatively.3 The recommendations for minimizing postoperative insulin resistance are listed in Box 1.
The multimodal approach to enhance recovery after surgery (ERAS) Pre-admission counselling
Avoidance of fluid and sodium overload No bowel prep Warm environment Reduced fasting times No drains Carbohydrate loading Early mobilization Mid-thoracic epidural anaesthesia Early removal of catheters Short-acting anaesthetic agent Non-opiate analgesia Short incisions Stimulate gut motility No nasogastric tubes for Perioperative nutrition gastric drainage
Factors to reduce postoperative insulin resistance C C C C
Table 3
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Reduce fasting preoperatively Carbohydrate loading preoperatively Consider operative procedure i.e. minimally invasive Early postoperative nutrition
Box 1
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BASIC SCIENCE
nervosa, those with minimal intake for >7 days, should have their electrolytes (i.e. sodium, potassium, calcium, magnesium and phosphate) checked and repleted prior to feeding. Thiamine which is an essential coenzyme in carbohydrate metabolism should be given 30 minutes before commencing the feed. The feed should provide 5e20 kcal/kg per day until stable. Once stable, the feed can be increased to meet full nutritional requirements.
In recent years, traditional guidelines to fast patients preoperatively have been abandoned as there is lack of evidence that it reduces the risk of aspiration. There is now a much stronger evidence base showing the benefit of allowing free fluid intake up to 2 hours before surgery. Consequently many anaesthesiology societies have changed their guidelines regarding fasting. Food is now allowed up to 6 hours before surgery and clear oral fluids or carbohydrate loading drinks up to 2 hours before surgery.
Route of nutritional support Preoperative carbohydrate loading
As a general rule of thumb ‘if the gut works use it’. Enteral feeding where possible is superior to parenteral feeding as it delivers nutrients to the gut and maintains gut integrity by preventing gut atrophy and subsequent bacterial translocation. In comparison to PN, it is cheaper, safer and easier to administer as it does not require specially trained staff. It can be administered via a nasogastric, nasojejunal, jejunostomy or gastrostomy feeding tube. If gastric stasis is an issue, then nasojejunal feeding should be commenced. In comparison with enteral nutrition (EN), parenteral nutrition (PN) is expensive, unphysiological and there is a risk of metabolic disturbances and sepsis, it requires close monitoring of electrolytes and it requires trained staff to administer. Despite this, PN is vital in the management of certain clinical conditions, for example short bowel syndrome, fistulae, intestinal failure, postoperative ileus, mucositis, dysmotility. There is little benefit to providing PN for shorter than 7 days and this must be a consideration when the referral is made. PN contains glucose often present in high concentrations, making it an ideal medium for the growth of bacteria, making it vital that it is administered aseptically via a dedicated lumen identified at the time of insertion of the central line and clearly marked as such. If all lumens have been used then a new line should be inserted. Manipulation of the line can increase the risk of infection, so only trained staff should make connections or disconnections. In extenuating circumstances, if the line has to be used for fluids or drugs other than PN, this should be done aseptically and the nutrition team and surgical teams informed. Electrolyte disturbances are common in patients receiving PN, but can be corrected by appropriate adjustment of TPN electrolyte content or by separate intravenous supplementation. If the liver function tests (LFTs) become acutely abnormal, the PN should not be discontinued, but the source of the problem identified, for example sepsis, hepatotoxic drugs etc. However, PN prescriptions should be reviewed in patients receiving longterm PN whose LFTs become abnormal as this may be a sign of overfeeding. Wherever possible, a small amount of enteral feeding at 30 ml/hour (trophic feeding) should be given alongside the PN. This will prevent gut atrophy and promote stimulation of the entero-hepatic circulation.
Carbohydrate loading ensures that the liver and muscle glycogen stores in the body are replete thus optimizing the metabolic response to surgery. It improves the postoperative recovery period by its effects on reducing insulin resistance, improving protein balance, preservation of lean body mass and muscle strength and reducing length of hospital stay. It involves the use of specially formulated carbohydrate drinks which leave the stomach rapidly as they have a low osmolality. They achieve an insulin response similar to that which is seen occurring after a normal meal. This ensures that the patient is in the ‘fed’ or anabolic state rather than the ‘fasted’ state prior to surgery. Insulin sensitivity is increased when they are given before the onset of the stress. These drinks can be taken up to 2 hours before surgery, assuming gastric emptying is not impaired.
Early enteral feeding Historically, postoperative feeding was often delayed until the passage of flatus and the presence of bowel sounds. There was also a fear that early feeding would cause a breakdown of the bowel anastomosis. The ERAS program has challenged this and several researchers have illustrated that both flatus and bowel sounds return sooner in those who are fed in comparison to those starved postoperatively. The incidence of anastomotic breakdown in the fed group was not significantly greater than the fasted group. Patients should be offered nutritional supplements or diet as tolerated from day 1 to 2 post surgery. If a postoperative ileus occurs, then a nasogastric tube should be inserted for drainage and intravenous feeding by day 7e10. Patients failing to meet their nutritional requirements postoperatively should be referred to a dietitian who can advise on nutrition support. If artificial nutrition support is indicated, this can be administered via a nasogastric or nasojejunal feeding tube. Before feeding commences, the patient’s risk of refeeding syndrome should be determined.
Refeeding syndrome Refeeding syndrome is common, but often goes unrecognized. It is defined as the potentially fatal shifts in fluids and electrolytes that may occur in malnourished patients receiving artificial feeding. It is caused by the metabolic and hormonal changes which occur after rapid feeding following a prolonged period of minimal intake or starvation.4 The metabolic effects of refeeding syndrome are hypokalemia, hypophosphatemia, hypomagnesemia, hypocalcemia and vitamin deficiencies. Those identified at high risk, for example alcoholics, anorexia
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Postoperative nutrition support on the intensive therapy unit Patients admitted to the intensive therapy unit (ITU) postoperatively generally require support of one or more organs, particularly the respiratory system, necessitating ventilatory support or intensive and invasive monitoring. Initially postoperatively the priority is resuscitation and stabilization of the patient. Following this, there is evidence to
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available all with their own limitations.6 See Table 4 for examples of types of equations.
support that commencing early enteral nutrition (EN) within 24 hours is associated with a significant reduction in mortality and pneumonia.5 The hypothesis for this is that early EN preserves the gut associated lymphoid tissue and barrier function, thereby reducing the risk of translocation of gut organisms.
ITU feeding protocols Feeding protocols are widely used on ITU to promote the early and safe provision of enteral nutrition. Studies show that protocols are associated with improved enteral feed delivery.7 Protocols recommend incremental feed delivery rates based on Gastric Residual Volume (GRV) threshold levels (aspiration of gastric contents with a syringe), which may vary between 120 and 500 ml on different units. GRVs are used as a marker of gastric emptying. Rationale for withholding feed if levels are high is based on the assumption that aspiration of gastric contents is associated with pneumonia. Limitations to this rationale include: GRV thresholds do not consider gastric and salivary secretions which may equate to 188 ml/hour. Reliable measurements can be difficult to obtain. Poor correlation between GRVs and other measures of gastric emptying, for example paracetamol absorption test. Poor association between higher GRV measurements and pneumonia. GRVs should thus be interpreted with caution especially as patients often do not receive their full feed prescription for periods of starvation for theatre, investigations, planned tracheal extubation etc. Hypocaloric feeding can be associated with negative outcomes particularly infection.8 Where GRVs are persistently high, protocols advocate the prescription of prokinetic drugs such as metoclopramide and/or low doses of the antibiotic erythromycin. If this is unsuccessful then the placement of a single or double lumen nasojejunal tube should be considered. The latter allows feeding into the jejunum with concurrent drainage of gastric contents.
Goals of nutrition support on ITU Attenuate loss of lean body mass in order to support recovery and weaning from the ventilator. Weight loss and muscle wasting are unpreventable during the acute phase of illness even with adequate nutrition (Frankenfield 1997). Avoid risks of under feeding which include impaired immune function, infection risk, poor wound healing, muscle wasting and prolonged ventilatory wean. Avoid risks of overfeeding which include azotaemia, hyperglycaemia, hepatic dysfunction and hypercapnia, which may hinder weaning. Avoid metabolic complications such as refeeding syndrome (see section above).
Nutritional assessment of ITU patients This can be extremely difficult in an ITU setting, unless the patient has been assessed prior to an elective procedure. Anthropometric measurements are often not possible to undertake in an unstable, sedated patient and if obtainable would be inaccurate as fluid retention can cause significant weight increases over short periods of time. Biochemical markers, for example albumin, are also inaccurate due to reduced synthesis, increased degradation, transcapillary escape and dilution effects.
Nutritional requirements of the ITU patient There is much debate regarding determining appropriate energy provision for ITU patients. They are an extremely heterogeneous population of patients from a range of specialities. In addition to this, the presence of large wounds, infection, sepsis, differing levels of sedation, paralysis and mode of respiratory support can affect energy requirements. The gold standard for establishing energy requirements is by measuring oxygen consumption and carbon dioxide output using an indirect calorimeter. Unfortunately due to lack of availability of equipment and cost this is often only used in research settings. In practice prediction equations are used. There are more than 200 different equations
Feeding regimens on ITU Once requirements have been determined, a feed prescription is devised to best meet these, detailing the volume to be given and rate of delivery over a 24-hour period. Often polymeric standard fibre or non-fibre feeds are used which contain varying levels of kilocalories (kcal) and protein. Non-feed sources of energy also need to be considered (e.g. the sedative propofol is based in a lipid emulsion and provides 1.1 kcal/ml).
Equations used for calculating feeding regimes Type of equation Regression equations derived from healthy populations to which stress factors and activity factors for patients conditions are added Regression equations derived from specific intensive therapy unit patient populations Equations based on physiological variables e.g. respiratory rate, tidal volume, body temperature
Examples Schofield, Harris-Benedict
Limitations Use of stress factors is open to error
Ireton-Jones Penn State
May not apply to all patients, check reference population used Very complex Variables change throughout the day
Swinamer
Table 4
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Specialist feeds on ITU Immune modulating feeds Immune modulating enteral feeds contain different combinations and doses of omega-3 fatty acids, arginine, glutamine and nucleotides. These formulations may benefit specific surgical patients but some reports that arginine may worsen mortality in sepsis have limited their use.9 Renal feeds Low-electrolyte/low-volume feeds are available for patients with renal failure who are fluid restricted or whose electrolyte levels are deranged. If a patient is receiving continuous renal replacement therapy then a standard feed is preferential particularly because renal feeds tend to be lower in protein and haemofiltration can result in significant nitrogen losses.
Figure 2 Large open abdominal wound after intensive nutrition and stoma therapy support.
Nutritional management of postoperative complications Postoperative ileus From as early as 1906, postoperative ileus was recognized as a frequent complication after abdominal surgery. Despite this, an understanding of the cause of ileus and the means to prevent it are still incomplete. Ileus invariably leads to malnutrition, prolonged hospital stay, and is associated with an increase in morbidity. The patient with a postoperative ileus for >7 days should be treated with PN until the ileus has resolved.
and protein requirements cannot be met via diet and sip feeds, a high-protein feed should be administered via a nasogastric feeding tube.
Enterocutaneous fistulae Gastrointestinal fistulae can form due to surgery, disease or trauma. Enterocutaneous fistulae (ECF), defined as abnormal communications between bowel and skin, are among the most challenging conditions managed by the general surgeon. The mortality from an enterocutaneous fistula remains 10e30% due to the often present complications of sepsis, malnutrition and deranged electrolytes. Overall management consists of controlling sepsis, optimization of nutritional state, wound care, assessment of fistula anatomy, appropriate timing of surgery and surgical strategy (the SOWATS guideline).10 Application of the SOWATS guidelines allows a favourable outcome after a short convalescence period. Abdominal wall defects and preoperative hypoalbuminemia are important prognostic variables. Nutrition support is integral in the management of fistulae in preventing malnutrition and in the provision of nutrients to promote healing. In conservative management, the bowel is rested by putting the patient nil by mouth (NBM) and PN is commenced. This will also allow the basal fistula output to be measured. Fistula output should be monitored daily. Once fistula output is <200 ml, a low-residue diet is introduced and the effect of this on fistula output is monitored. If no increase in output occurs then diet is increased further to meet full nutritional requirement and TPN is weaned off accordingly. On the other hand, after 30e40 days if the output remains high >500 ml, PN is continued until an optimal time is reached when surgery can be performed. With a high output fistula, additional fluid and electrolytes will need to be added to PN or given intravenously in addition to PN. If optimal timing for surgery (3e6 months from previous surgery) has not been reached consideration should be given to discharging the patient to their own home on PN.
Surgical wounds For optimal wound healing to occur, the body needs to be well nourished. This will enable synthesis of acute phase proteins, white cells, fibroblasts collagen and other tissue components which can be delivered to the wound to promote healing. If these are not present, wound healing will be delayed and dehiscence or anastomotic breakdowns may occur. Large open abdominal wounds (Figures 1 and 2) will require intensive nutrition support. Protein intake should be optimized as losses from larger open abdominal wounds are often underestimated. There are also electrolyte, vitamin and mineral losses. Vitamin and mineral levels should be checked especially zinc and vitamin C. If calorie
High output stomas High output stomas lead to dehydration and metabolic disturbance (most commonly hyponatraemia, hypokalaemia
Figure 1 Large open abdominal wound.
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Steps involved in managing fluid loss from stomas STEP 4
STEP 1 • Review history (number of bags emptying/day, associated pain, etc) • Ask dietitian to review oral intake • Check drug chart (prokinetics, proton pump inhibitor dose, anti-diarrhoeal dose, lactose-containing medication) • Consider cause: – inappropriate diet – gastric hypersecretion – bacterial overgrowth – partial obstruction (parastomal hernia, adhesions, stomal stricture) – prestomal ileitis – recurrent Crohn’s – peristomal sepsis – short bowel – coincidental/undiagnosed disease (villous atrophy, hyperthyroidism, h ypolactasia, pancreatic insufficiency, dysmotility) • Arrange appropriate investigations: • Trial of empirical therapy: – dietary adjustment to a low-fibre, low-sugar diet and isotonic fluids – omeprazole 40–80 mg once daily – metronidazole 400 mg three times daily for 1 week – loperamide 4 mg four times daily – codeine 60 mg four times daily
Calculate stoma output while on isotonic fluids
<1200 ml/day
Go to Step 5
Measure impact, in succession, of i. omeprazole 80 mg once daily ii. add loperamide 8 mg four times daily iii. add codeine 60 mg four times daily iv. add octreotide 100 µg twice daily
Output <1500 ml/day
STEP 2 • • • • •
>1200 ml/day
Establish basal output by approach below 48–72 hours on intravenous fluids AND nil by mouth Monitor electrolytes (Na, K, Mg) daily Review by dietitian If basal output >1200 ml/day, then it is very unlikely that the patient will manage without intravenous fluids at home. Get advice from parenteral nutrition team.
Go to Step 5
Output >1500 ml/day
Anticipate and plan for long-term intravenous fluids or parenteral nutrition
STEP 3
STEP 5
• For 24–48 hours, establish the effect of isotonic fluids, which contain [Na + ] >90 mmol as net water absorption by the jejunum only occurs when luminal [Na + ] >90 mmol. The dietitian should explain to the patient and nursing staff the role of isotonic fluids and how they are constituted • Document fluid intake and ileostomy output.
• Establish effect of solid food, supervised by dietitian.
Figure 3 REFERENCES 1 Studley H. Percentage of weight loss. A basic indicator of surgical risk in patients with chronic peptic ulcer. JAMA 1936; 106: 458e60. 2 McWhirter JP, Pennington CR. Incidence and recognition of malnutrition in hospital. BMJ 1994 Apr 9; 308: 945e8. 3 Thorell A, Nygren J, Ljungqvist O. Insulin resistance: a marker of surgical stress. Curr Opin Clin Nutr Metab Care 1999 Jan; 2: 69e78. 4 Mehanna HM, Moledina J, Travis J. Refeeding syndrome: what it is, and how to prevent and treat it. BMJ 2008 Jun 28; 336: 1495e8.
hypomagnesaemia and uraemia). Advice to drink extra fluids can make the situation worse, especially if these are hypo- or hypertonic fluids. Fluids flush the small intestinal contents through and exacerbates dehydration and electrolyte losses. As food and fluids can promote secretion and increase volume, it is important to assess daily food and fluid intake. The steps defined in Figure 3 are necessary to establish and correct the cause, with the aim of achieving a stoma effluent volume of <1200 ml/day. A
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5 Doig GS, Heighes PT, Simpson F, Sweetman EA, Davies AR. Early enteral nutrition, provided within 24 h of injury or intensive care unit admission, significantly reduces mortality in critically ill patients: a meta-analysis of randomised controlled trials. Intensive Care Med 2009 Dec; 35: 2018e27. 6 Walker RN, Heuberger RA. Predictive equations for energy needs for the critically ill. Respir Care 2009 Apr; 54: 509e21. 7 McClave SA, Martindale RG, Vanek VW, et al. Guidelines for the provision and assessment of nutrition support therapy in the adult critically ill patient: Society of Critical Care Medicine (SCCM) and American Society for Parenteral and Enteral
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Nutrition (A.S.P.E.N.). JPEN J Parenter Enteral Nutr 2009 MayeJun; 33: 277e316. 8 Villet S, Chiolero RL, Bollmann MD, et al. Negative impact of hypocaloric feeding and energy balance on clinical outcome in ICU patients. Clin Nutr 2005 Aug; 24: 502e9. 9 Heyland DK, Novak F. Immunonutrition in the critically ill patient: more harm than good? JPEN J Parenter Enteral Nutr 2001 MareApr; 25(2 suppl): S51e5 [discussion S5e6]. 10 Visschers RG, Olde Damink SW, Winkens B, Soeters PB, van Gemert WG. Treatment strategies in 135 consecutive patients with enterocutaneous fistulas. World J Surg 2008 Mar; 32: 445e53.
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