|Year : 2016 | Volume
| Issue : 4 | Page : 469-477
Perioperative nutrition to enhance recovery after surgery
Department of Anesthesia, Intensive Care, and Pain Management, Ain Shams University, Cairo, Egypt
|Date of Submission||02-Oct-2016|
|Date of Acceptance||05-Oct-2016|
|Date of Web Publication||12-Jan-2017|
8595, El Reda and Nour Street, Mokattam, Cairo, 11571
Source of Support: None, Conflict of Interest: None
Preoperative malnutrition is a major risk factor for increased postoperative morbidity and mortality. Patients at risk for malnutrition should be identified early. The Nutritional Risk Score is a validated tool to identify patients who should benefit from nutritional support. The adoption of total parenteral nutrition followed by the extraordinary progress in parenteral and enteral feedings, in addition to the increased knowledge of cellular biology and biochemistry, has allowed clinicians to treat malnutrition and improve surgical patient’s outcomes. Periods of prolonged fasting should be minimized and nutrition should be commenced as early as possible after surgery, preferably through the enteral route. The surgical patient with established malnutrition should begin aggressive nutrition at least 7–10 days before surgery. Those patients in whom eating is not anticipated beyond the first 5 days following surgery should receive the benefits of early enteral or parenteral feeding depending on whether the gut can be used. Many patients may benefit from newer enteral formulations, such as those designed to enhance immune function (immunonutrition).
Keywords: enteral nutrition, immunonutrition, total parenteral nutrition
|How to cite this article:|
Salah D. Perioperative nutrition to enhance recovery after surgery. Ain-Shams J Anaesthesiol 2016;9:469-77
| Introduction|| |
Ever since 1936 when Studley  demonstrated a direct relationship between preoperative weight loss and operative mortality, nutritional support of surgical and critically ill patients has undergone significant advances. The WHO cites malnutrition as the greatest single threat to the world’s public health as the reported in-hospital prevalence of malnourished patients on admission ranges up to 50% ,. Malnutrition is considered a risk factor for impaired systemic and intestinal immune function, as well as decreased digestive and absorptive capacity due to the altered architecture of the gut barrier . Perioperative nutrition has been convincingly shown to improve clinical outcome in patients undergoing major gastrointestinal surgery, to reduce costs, and to decrease length of hospital stay . The mechanism of action seems to be not only an improved nutritional status by providing a higher caloric intake, but primarily a re-enforced immune response; nutritional formulas containing immunomodulating agents (glutamine, arginine, n-3 fatty acids, and RNAs) are particularly beneficial modulators of the acute stress response ,.
Major stress, such as surgery, can subject a patient to a whole host of metabolic and physiologic changes. The body responds to such stress by increasing its basal metabolic rate, using up its nitrogen stores, and creating a negative nitrogen balance . An increase in gluconeogenesis as well as the synthesis of acute phase proteins is also observed . The body scavenges for the required nutrients during times of stress, which if continues undetected for prolonged periods of time could lead to adverse consequences. Perioperative nutritional supplementation, therefore, should blunt the catabolic effects of such a high-energy state . Interestingly, there is an increase in intestinal permeability during periods of surgical stress, which can be as greater as four-fold in some patients, usually normalizing around fifth postoperative day ,,. Associated with this increase in permeability is a decrease in villous height, leading to malabsorption and an impaired ability of the gut to act as a barrier against endogenous bacteria and toxins ,.
Malnutrition and surgery can also both present a stress on the heart. Patients undergoing cardiac surgery are frequently found to be malnourished, resulting in alteration in the structure of myocytes and depleting the substrates utilized by the heart for mechanical work. It is therefore hypothesized that, by addressing the undernourished state of the patient before surgical intervention, we can improve cardiovascular performance and decrease the incidence of cardiac complications after surgery as well as lower perioperative mortality .
The aim of this review was to focus on the advantages, limitations, and comparisons of both parenteral and enteral nutrition (EN) in the malnourished perioperative patient.
| Preoperative|| |
Nutritional assessment and population at risk for perioperative malnutrition
Nutritional status is difficult to quantify accurately. A history of chronic disease, cancer, infection, surgery, recent reduced dietary intake, and weight loss help identify patients at risk for malnutrition. Assessment may include a calculation of BMI, an estimate of recent loss of subcutaneous fat and muscle mass, and signs of specific nutritional deficiencies . Interestingly, malnutrition can occur in obese patients who have low muscle mass. This form of obesity, termed sarcopenic obesity, may be less recognizable in many cases . In many patients, fat-free mass index may be a better predictor for mortality compared with BMI. Van Venrooij et al.  found that low fat-free mass index was associated with an increased occurrence of adverse outcomes after cardiac surgery. They advocate fat-free mass index as the leading parameter in classifying and treating malnourished cardiac surgical patients .
Numerous laboratory indices have been proposed as markers of nutritional status. For example, low preoperative serum albumin concentrations are associated with delayed wound healing  and can be used to predict morbidity in patients undergoing elective operations ,,. However, as albumin concentration is suppressed by surgery and illness, its postoperative measurement is of limited value . The perioperative measurements of serum transferrin and prealbumin have more potential, along with serum cholesterol and lymphocyte count, as their half-lives are shorter than that of albumin . However, the clinical value of these markers is indicative rather than diagnostic, as they are not specific for malnutrition.
The European Society of Parenteral and Enteral Nutrition guidelines recommend the use of the Nutrition Risk Screening 2002 tool, along with subjective global assessment, and serum albumin less than 30 g/l in their evaluation of undernutrition ,. [Table 1] illustrates the components of the tool. In one study by Jie et al. , those patients scoring 5 or higher on the Nutrition Risk Screening 2002 malnutrition scale received the most benefit from perioperative nutritional support.
The most common surgical practice of making patients nil per os after midnight of the day of any planned surgical procedure has been recently questioned. Brady et al.  reviewed 38 randomized controlled trials on perioperative fasting and concluded that there was no evidence to suggest that overnight fasting for fluids results in a decrease in perioperative aspiration risk or related morbidities . Evidence is emerging that overnight fasting is not only unnecessary but may also be harmful.
Gastric emptying is controlled by neural and hormonal pathways and is determined by a number of intraluminal and extraluminal factors. Intraluminal factors include meal composition (caloric load, volume, temperature, and nutrient type), the osmolality of small intestinal contents, and the length and the region of small intestine exposed to nutrient . Extraluminal factors include glycemia, posture, pain, sex, and age ,. The optimal duration of fasting for a particular patient depends on numerous factors. The rate of emptying of nutrient from the stomach is linear, with emptying occurring more rapidly for liquids than for solids. In contrast, water is emptied from the stomach exponentially, with an approximate half-life of 10 min ,,.
Gastroesophageal regurgitation and pulmonary aspiration is thought to be more likely in critically ill patients, due to disturbed gastric and esophageal motility . Preoperative fasting, particularly when 6 or more hours in duration, will starve critically ill patients who require frequent operations ,.
Factors associated with slower gastric emptying are as follows.
- Diseases affecting autonomic dysfunction, such as diabetes mellitus, amyloidosis, Parkinson’s disease, multiple sclerosis, HIV, and spinal injury.
- Other diseases such as hyperglycemia, alcoholism, hypothyroidism, malignancy, and critical illness.
- Gastrointestinal diseases such as gastric dysmotility, gastric outlet, or bowel obstruction.
- Surgical causes such as vagotomy, fundoplication, and Roux-en-Y anastomosis.
- Drugs such as opiates, tricyclic antidepressants, calcium channel blockers, dopamine agonists, α-2-adrenergic agonists, glucagon-like peptide-1 receptor agonists, muscarinic cholinergic receptor antagonists, catecholamines, cyclosporine, and somatostatin analogs (e.g. octreotide).
- In addition, composition of meal ingested, high caloric load, large lipid component, pregnancy or postpartum state, and advanced age .
Surgical stress causes postoperative insulin resistance, immunosuppression, and increased patient discomfort ,. Patient outcomes may be improved by a shorter fasting period preceded by prescribed carbohydrate intake . Studies have reported that postoperative insulin sensitivity is preserved by carbohydrate drinks (100 g the night before surgery and 50 g 2 h before surgery)  or intravenous glucose (5 mg/kg/min) , possibly through suppression of fat and glucose oxidation and attenuation of pyruvate dehydrogenase kinase .
Preoperative nutritional support and immunonutrition
International guidelines recommend nutritional support for severely malnourished patients 7–14 days before elective major surgery. Severely malnourished patients have at least one of the following: weight loss more than 10–15% within 6 months; BMI less than 18.5 kg/m2; or serum albumin below 30 g/l without hepatic or renal dysfunction .
The optimal timing of nutritional intervention remains a controversial topic. Preoperative preparation of the patient gained support following several landmark studies by Gianotti et al.  and Braga et al.  demonstrating that major morbidity could be reduced by ∼50% in patients undergoing resection for malignancy of the esophagus, stomach, or pancreas. This benefit was noted in both the well-nourished and malnourished patient populations. They provided an immunomodulating formula given 5 days preoperatively, which included arginine, omega-3 (ω) fatty acids, and nucleic acids, and resulted in significant decreases in infectious morbidity, length of hospital stay, and hospital-related expenses.
In terms of nutritional support, it is generally accepted that earlier is better than later, that enteral is superior to parenteral, that the quality of nutrient appears more important than the quantity, and that select populations will show additional benefit from specific nutrient supplementation. Goals of nutritional support have changed in the past few years from attempts to preserve lean body mass following a surgical or traumatic stress to efforts to attenuate the hypermetabolic response, reverse loss of lean body mass, prevent oxidant stress, favorably modulate the immune response with early enteral feeding, attain meticulous glycemic control, and administer appropriate macronutrients and micronutrients .
| Intraoperative|| |
There are few randomized controlled trials assessing intraoperative enteral feeding. Studies are limited to surgery following burn injury and nongastrointestinal trauma . Following burn injury, the small intestine can be fed during surgery, which reduces cumulative calorie deficits and does not appear to increase the risk for aspiration of gastric contents . Intraoperative EN, except during surgery on the airway or gastrointestinal tract, can shorten the duration of fasting in mechanically ventilated critically ill patients.
| Postoperative|| |
Optimal time to start nutrition
The optimal time to start postoperative nutritional intervention is significantly influenced by a host of factors such as age, premorbid conditions, route of delivery, metabolic state, organ involvement, etc. The reported benefits of early enteral feeding are prevention of adverse structural and functional alterations in the mucosal barrier, augmentation of visceral blood flow, and enhancement of local and systemic immune response .
Postoperatively, normal oral food intake or nutrition through feeding tube should start within the first 24 h. A meta-analysis evaluated early commencement of postoperative EN (within 24 h) versus traditional management in patients undergoing gastrointestinal surgery. It was in favor of early enteral feeding following gastrointestinal surgery to reduce morbidity and mortality rates . The beneficial effect of early oral feeding was also shown by El Nakeeb et al. . There is strong evidence that oral nutritional supplements (200 ml twice daily) given from the day of surgery until normal food intake is achieved are beneficial.
The optimal duration of nutritional support in the postoperative period remains unclear. Although using postoperative oral nutritional supplements for 8 weeks in malnourished patients enhances recovery of nutritional status and quality of life , benefits for well-nourished patients are less evident . Concerning postoperative immunonutrition, duration of therapy varied from 3  to more than 10 days ,,, with the most common duration being 7 days ,,.
| Route of administration|| |
Specific benefits to perioperative EN include a reduction in the incidence of postoperative infections and complications, and improved wound healing ,. This would also include fewer life-threatening surgical complications, such as anastomotic stenosis or leak, delayed gastric emptying, recurrent nerve palsy, and superficial or deep fascial surgical site infections ,. EN has been shown to be cost-effective by reducing the length of hospital stay . These effects are thought to be due to EN capacity to maintain gastrointestinal integrity, thus preventing villous atrophy, to attenuate the body’s response to stress and maintain immunocompetency through IgA secretion ,,. EN contraindications include the presence of intestinal obstruction, malabsorption, multiple fistulas with high output, intestinal ischemia, severe shock with impaired splanchnic perfusion, and fulminant sepsis ,.
Strategies used to reduce postoperative gastrointestinal dysmotility and increase success of postoperative enteral feeding include the following :
- Correction of pH imbalance.
- Correction of electrolyte abnormalities (especially potassium and magnesium).
- Limiting excessive fluid administration.
- Minimization of exogenous opiates.
- Optimization of glycemic control to avoid hyperglycemia-induced slowing of gastric emptying.
- Early institution of enteral feeding.
- Use of prokinetic medications to treat established feed intolerance ([Table 2]).
Total parenteral nutrition (TPN) has been shown to significantly affect postoperative outcomes in the severely malnourished patient group ,. Because of its direct central venous administration, parenteral nutrition can rapidly improve nitrogen balance, which allows for quicker lymphocyte recovery and improved wound healing ,. Although TPN has many benefits, there are considerable risks to its use. Volume overload can cause respiratory compromise, particularly in individuals with marginal cardiopulmonary reserve . Hyperglycemia, along with its metabolic consequences, can result in adverse outcomes if allowed to remain uncorrected.
Hyperglycemia is also associated with the dysfunction of the immune response. Abnormalities include affecting the granulocyte adhesion, chemotaxis, phagocytosis, complement function, and intracellular killing ,. Compher et al.  were able to demonstrate that tight glycemic control in ICU patients receiving TPN resulted in fewer infectious complications and a decrease in mortality. Overfeeding is another concern with TPN, especially in patients at extreme ages. Overfeeding can lead to azotemia, hypertonic dehydration, and metabolic acidosis. Excessive carbohydrate infusion results in hyperglycemia, hypertriglyceridemia, and hepatic steatosis. High lipid infusions can cause hypertriglyceridemia and fat-overload. Hypercapnia and refeeding syndrome may also result from aggressive feeding  ([Table 3]).
| Optimum nutrition|| |
As regards specific macronutrients, the requirement for carbohydrates is estimated at 3–6 mg/kg/min (roughly 200–300 g/day), for protein it is 1.25–2.0 g/kg/day, and for lipids it is 10–25% of total calories, depending on the route and lipid composition . These figures vary depending on the specific patient condition. Ideally, one would like to provide sufficient nutrients to minimize the catabolic loss associated with stress, injury, and surgery while avoiding the problems associated with overfeeding, such as hyperglycemia, azotemia, excess CO2 production, etc.
Several trials suggest additional benefits with immunomodulation compared with the standard formulas when the appropriate population is chosen. More than 27 prospective randomized trials using immunomodulation formulas have resulted in very similar conclusions, demonstrating a decrease in infectious complications and shortened hospital stays with no change in overall mortality ,. Some editorials continue to support the use of immune formulas , whereas others report them as poison .
The greatest debate revolves around the pros and cons of additional arginine in the ICU setting. One school considers that arginine is potentially toxic , whereas another argument is that arginine is deficient in critical illness and should be supplemented. No prospective clinical data are currently available proving that arginine is harmful, whereas numerous prospective articles have demonstrated arginine to be beneficial, especially in the surgical and trauma population.
Glutamine is the other conditionally essential amino acid that has recently gained even greater support in the critical care setting. Glutamine has been reported to offer a myriad of benefits, including maintenance of acid/base balance, provision of primary fuel for rapidly proliferating cells (i.e. enterocytes and lymphocytes), synthesis of glutathione and arginine, and lowering of insulin resistance, and functions as a key substrate for gluconeogeneis . Evidence that glutamine can induce heat-shock protein is yet another beneficial molecular effect of this amino acid . The heat-shock proteins are a class of cellular chaperone proteins that support appropriate protein folding . With glutamine enhancing heat-shock protein, the cell protects itself from subsequent stress.
The ω-3 fats in fish oil have multiple beneficial effects in the perioperative period, including modulation of leukcocyte function and regulation of cytokine release through nuclear signaling and gene expression . The ω-3 lipids have recently been reported to enhance the production of a new group of prostaglandin derivatives called resolvins and neuroprotectins, which play a role in accelerating their solution of the proinflammatory state  ([Table 4]).
|Table 4: The daily vitamins and trace element requirements for an adult receiving artificial nutrition |
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| How much to feed?|| |
The caloric requirement for the perioperative and ICU patient is evolving as the concept of hypocaloric feeding, or so-called permissive underfeeding, in the early ICU and postoperative period. There is a relative anorexia that occurs from significant illness and the supply of nutrients during this period induces a proinflammatory state, which then exacerbates the condition. This concept has led several investigators to encourage hypocaloric feeding in the early phases of critical illness. Krishnan et al.  reported that underfeeding the septic medical ICU patient resulted in a small improvement in survival. In a study evaluating TPN and caloric delivery, McCowan et al.  demonstrated an interesting but not statistically significant trend in decreasing infectious complications. Several studies in critically ill obese patients use a hypocaloric high-protein regimen with excellent metabolic results ,. Although the optimal caloric load for the hypermetabolic (nonobese) patient remains in transition, the caloric delivery currently considered safe for the perioperative period is in the range of 20–30 kcal/kg/day (excluding the morbidly obese).
| Special patient groups|| |
Despite a considerable fat store, obese patients are at risk of loss of lean body mass through gluconeogenesis and micronutrient deficiency during times of acute stress. Fasting insulin concentrations are increased, which suppress lipid mobilization from stores and result in accelerated protein breakdown to fuel gluconeogenesis . These risks may be increased because of an incorrect assumption that obese patients have a greater ‘nutritional reserve’ compared with nonobese patients .
Screening and supplementation for micronutrient deficiency may be of benefit. For example, patients undergoing laparoscopic sleeve gastrectomy can be deficient in vitamin D, iron, thiamine, and vitamin B12 . Postoperative nutrition should contain enough protein to minimize muscle loss and aid wound healing and should contain enough calories to prevent severe ketoacidosis . High-protein hypocaloric feeding of critically ill obese patients has been evaluated with the aim of allowing fat stores to be utilized for energy and sparing muscle protein from excessive catabolism ,,. Suggested caloric requirements for this group of patients are 22–25 kcal/kg ideal body weight/day (or 11–14 kcal/kg actual body weight/day) with 2 g/kg/day of protein, but the evidence upon which the recommendation is based is weak .
Aging is associated with a reduction in lean body mass, increase in body fat, decrease in total body water, and a reduction in bone density . Advanced age is independently associated with poor nutritional status in hospitalized patients . Deficiencies of vitamins B6, B12, C, D, folate, and calcium are prevalent in this group ,. Elderly patients who have experienced 10% or more weight loss in the previous 6 months, or who are hypoalbuminemic, experience more adverse postoperative outcomes . Perioperative nutritional support is indicated in malnourished elderly patients, who are not in a terminal phase of illness, and the enteral route is preferred . Although the evidence is limited, nutritional supplementation may reduce morbidity in elderly patients who suffer a hip fracture  or who undergo total hip or total knee arthroplasty .
The critically ill
Critically ill surgical patients often do not receive adequate nutrition , although only two specific situations arise where concerns about the safety of EN may be valid − namely, for patients receiving vasopressor drugs and those with laparostomies. The rationale for avoiding EN is that it might exacerbate subclinical gut ischemia in patients receiving vasoconstrictor agents. However, in health, mesenteric artery blood flow increases with nutrient load . Retrospective observational data have suggested that enteral feeding during shock is safe and may be associated with reduced mortality . A recent large multicenter cohort study conducted in France reported that nutrition within 48 h of intubation in shocked patients was associated with reduced mortality, irrespective of the route of feeding . Similarly, EN does not appear to delay closure of laparostomies and has been associated with a reduction in the frequency of both fistulae formation and pneumonia .
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]