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Ann Clin Nutr Metab 2023;15(2):40-45
Published online August 1, 2023
Perioperative nutrition support: a narrative review
Rajeev Joshi, Asma Khalife

Department of General Surgery, Topiwala National Medical College & B.Y.L. Nair Charitable Hospital, Mumbai, India
Correspondence to: Asma Khalife, email: asma.khalife@gmail.com
Received June 21, 2023; Revised July 25, 2023; Accepted July 27, 2023.
© 2023 The Korean Society of Surgical Metabolism and Nutrition and The Korean Society for Parenteral and Enteral Nutrition.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Purpose: Proper nutrition and supplementation are paramount in surgical patients. Suboptimal nutrition status is increasingly recognized as an independent predictor of poor surgical outcomes. The purpose of this review is to highlight the need for nutritional protocols, with an emphasis on perioperative nutrition.
Current concept: Perioperative nutrition support is considered an adjunctive strategy in most centers, although it is proven to be the key in improving surgical outcomes. There is a need to increase the standards and formulate policies and protocols to optimize perioperative nutrition support. Components of perioperative nutrition include nutritional screening and assessment, prehabilitation, preoperative metabolic optimization and carbohydrate loading, postoperative early enteral feeding and perioperative parenteral nutrition, immunonutrition and micronutrients, and oral nutritional supplementation vs. hospital-based kitchen feeds. Supplemental parenteral nutrition becomes valuable when enteral nutrition alone cannot fulfil energy needs. In patients in the surgical intensive care unit who are dealing with hemodynamic instability, high levels of serum lactate unrelated to thiamine deficiency, acidosis, significant liver dysfunction, high blood sugar, and high blood lipid levels, parenteral nutrition must be started with caution. In the post-surgery care ward, it is advisable to administer up to 30 kcal/kg/day and 1.2–2 g/kg/day of protein.
Conclusion: The positive impact of comprehensive nutritional support and the importance of setting and executing standards must be highlighted. Emphasis should be placed on overcoming existing challenges in implementing nutrition therapy in current surgical practice, as better perioperative nutrition supports better surgical outcomes.
Keywords : Dietary supplements; Enteral nutrition; Immunonutrition diet; Micronutrients; Nutrition assessment
Introduction

Nutritional support has been considered adjunctive care, not an active therapeutic strategy. It is essential instead to stress the importance of comprehensive perioperative nutrition support to improve surgical outcomes. Suboptimal nutrition status is increasingly considered an independent predictor of poor surgical outcomes [1]. The emphasis is now on the positive impact of nutrition therapy on surgical outcomes and the understanding that it remains a key aspect of enhanced recovery. There is a need to strengthen the standards and formulate new policies and protocols to optimize perioperative nutrition support.

Nutrition practices in surgical patients need to be addressed in elective, emergent, and emergency situations as well as preoperative, postoperative, and postdischarge settings. Implementing such practices involves an interplay between recommendations, nutrition practices, lacunae, and the challenges in improving practices and the subsequent solutions. Recommendations are generally based on the standard European Society of Parenteral and Enteral Nutrition (ESPEN) [2] or Asian Surgical Consensus on Nutrition Therapy (ASCENT) guidelines. Still, there are country or between-hospital differences in implementation, and these discrepancies need to be bridged to optimize therapy. The challenges can be overcome by creating awareness of how to overcome the consequences of metabolic derangement following surgery by integrating nutritional care into overall patient management. Optimal perioperative nutrition support is necessary, and a proper understanding is essential to improve surgical outcomes.

Components of perioperative nutrition

The concept of perioperative nutrition includes understanding the main components of nutrition, nutritional management in the postoperative surgical intensive care unit (SICU) and wards, and post discharge recommendations. The components of perioperative nutrition can be enumerated as follows: nutritional screening and assessment; prehabilitation; preoperative metabolic optimization and carbohydrate loading; postoperative early enteral feeding and perioperative parenteral nutrition (PN); immunonutrition and micronutrients; and oral nutritional supplementation (ONS) vs. hospital-based kitchen feeds. If surgeons would recognize the importance of proper perioperative surgical nutritional support and proper implementation of evidence-based nutrition practices, a significant improvement in outcomes could be expected.

Nutritional screening and assessment

Hospital malnutrition is a highly prevalent and frequently under recognized condition in Asia, and emphasis should be placed on its avoidance. Hospital malnutrition is associated with an estimated annual economic burden of more than USD 30 billion annually in additional healthcare costs [3]. Also, poor nutritional status is associated with increased morbidity and mortality rates. This underscores the need for rigorous screening and assessment as well as continuous monitoring of nutrition status in hospitalized patients to facilitate early identification and proactive management of hospital malnutrition. Various aspects of perioperative care are important in surgical practice to ensure optimal outcomes. Whereas comorbidities and risk factors like cardiopulmonary or hepatorenal conditions are routinely addressed, malnutrition is often left unrecognized and unaddressed. These patients consequently have diminished physiological reserves to overcome the surgical stress response due to a suboptimal nutrition state, adding to the morbidity and mortality rates [4].

Anticipating that all patients undergoing major surgery are at risk for nutritional deficits, assessing their nutritional status must be considered an integral part of the clinical evaluation. The Subjective Global Assessment (SGA), Nutrition Risk Score (NRS 2022), and Nutrition Risk in Critically Ill (NUTRIC) score are considered the best tools for assessing malnutrition in the preoperative period [5-8]. These tools assist in planning preoperative interventions, identifying nutritional deficiencies and other risk factors, and integrating nutritional care into overall management [9]. Patients with NRS 2002 >3, NUTRIC score ≥5, or SGA grade C are at high risk for malnutrition, and nutritional support should be considered in the preoperative period. The aim should be to start nutritional therapy as soon as nutritional risk becomes apparent. Preoperative intervention can be supplemental oral nutrition, enteral nutrition (EN), PN, or combined EN and PN. Preoperative PN can be considered in severely undernourished patients with recent weight loss >10%–15% of their body weight and who cannot be fed adequately through oral or enteral routes [2]. Other recommendations include the integration of nutritional care into overall management, assuming that all patients undergoing major surgery are at risk of deficits, anticipating the risk of deficits to prevent complications, and starting therapy as soon as the nutritional risk becomes apparent. Patients at high risk include chronically malnourished patients and those with little or no energy intake for >10 days. Malnourished surgical patients benefit from ONS before surgery as part of metabolic preparation, which continues in the postoperative period [10].

Prehabilitation

Prehabilitation is preparing the patient for upcoming surgery and improving their functional capability to withstand postoperative inactivity. Preoperative optimization of nutrition, limb exercises, chest physiotherapy, avoidance of long preoperative fasting periods, and smoking and alcohol cessation are important [10]. Prehabilitation optimally should be started from 4–8 weeks before surgery if the underlying condition permits [11]. While optimization is possible in the elective setting, partial or suboptimal optimization in the emergent setting and no optimization in the emergency surgery setting may occur.

Preoperative metabolic optimization and carbohydrate loading

Preoperative metabolic optimization starts by correcting any fluid and electrolyte imbalances and attaining adequate resuscitation. Metabolic optimization is essential and can be achieved by preoperative carbohydrate loading and postoperative glycemic control [12]. Before surgery, carbohydrate loading through isotonic carbohydrate solutions the previous night and 2 hours before surgery enhances glycogen stores in the liver, muscles, and myocardium and improves the postoperative glycemic response by reducing insulin resistance.

Insulin resistance and hyperglycemia are of major concern postoperatively in all major surgical patients and are closely associated with complications, especially infections [13]. However, both can be significantly minimized by following the Enhanced Recovery After Surgery (ERAS) protocol, which includes avoiding prolonged preoperative fasting, early postoperative feeding, epidural analgesia, and early mobilization. Glucose-insulin infusion is a safe way to reduce the risk of postoperative hyperglycemia. Overfeeding and hyperglycemia should be avoided; close monitoring is required to avoid them (>110 mg/dL). Studies have shown that irrespective of the route of nutritional support, glycemic control reduces mortality [14]. However, excess carbohydrate loading increases carbon dioxide production and difficulty in weaning and can cause hepatic steatosis and liver dysfunction.

Postoperative early enteral feeding and perioperative PN

Malnutrition and energy and protein deficits are independently associated with poorer clinical outcomes in surgical patients. Infectious complications, along with catabolism and loss of lean body mass leading to surgery-acquired sarcopenia are common. Hence, early initiation of nutritional support following surgery is important. Whether given in cyclical, continuous, or bolus form, early postoperative enteral feeds are important to ensure adequate caloric demand, except in patients with intestinal obstruction, shock, or ischemia [15]. Conventional treatment after bowel resection entails starvation with the administration of intravenous fluids until the passage of flatus, principally due to concerns over postoperative ileus. However, initiating feeding at a lower rate and advancing as tolerated is the new norm. Initiating early oral or enteral feeds is one of the main tenets of ERAS protocols. The basis for this is that small intestinal motility recovers 6–8 hours after surgical trauma and a moderate absorptive capacity exists even in the absence of normal peristalsis. Appropriate steps to prevent postoperative ileus include minimizing the use of opioids for pain relief, avoiding overhydration fluid strategies, and maintaining the electrolyte balance. Early initiation (<24 hours) of enteral feeding is recommended after gastrointestinal surgery (grade A) [16].

When EN is not feasible, PN ensures the provision of required nutrients to meet the patient’s needs and becomes necessary when the gastrointestinal tract cannot absorb sufficient nutrients via the enteral route because of a non-functional, inaccessible, or perforated gut. Early parental nutrition should be considered, especially in patients with severe malnutrition and NUTRIC score >5 or those with postoperative complications. The expected caloric goal is approximately 25–30 kcal/kg/day. With surgical insult, this requirement may increase by up to two-fold. In a patient not tolerating oral or enteral feeds, PN compensates for the required caloric demand. As per the 2017 ESPEN guidelines, when the caloric requirements are not met by oral or enteral intake alone (<50% of caloric requirements for >7 days), a combination of EN and PN is recommended within a single three-chamber bag. PN is recommended in all patients who cannot tolerate enteral feeds. The key parameter prior to starting PN is the cumulative caloric deficit; a prolonged calorie deficit >400 kcal/day leads to complications. The American Society of Parenteral and Enteral Nutrition and ESPEN guidelines jointly recommend starting PN within 24–48 hours if EN is not appropriate and the patient is at high nutritional risk. PN should be increased progressively, starting with a low dose and gradually increasing it, ultimately reaching the nutritional target 2–5 days after initiation. Close monitoring to prevent hyperglycemia and metabolic derangements is important [2].

Supplemental parenteral nutrition (SPN) is PN used in a step-up approach when full enteral support is not possible or fails to reach caloric targets. As much nutrition as possible is administered by the enteral route, and the deficit is addressed with PN. Providing EN and SPN without delay can prevent a calorie–protein gap. Currently, the trend is to move away from total PN toward hypocaloric nutrition (partial parenteral nutrition, PPN). Hypercaloric total PN requires central venous cannulation, causes hyperglycemia, and increases the risk of infection. However, PPN entails a peripheral infusion of amino acids and glucose at doses below a patient’s energy expenditure and represents a safer approach [17].

Energy targets for PN should be slightly lower than EN targets. Studies suggest that EN aiming for a 100% nutritional target usually results in the absorption of approximately 70% of nutrients. In contrast, PN generally achieves 100% of nutrient targets because enteral tolerance does not limit uptake. Therefore, it is suggested to aim for reduced caloric targets (70% of resting energy expenditure) in the acute phase of critical illness. Weaning off PN should be initiated once the patient demonstrates the ability to tolerate and utilize enterally administered nutrients or to ingest and utilize adequate oral nutrients. If daytime oral nutrient intake is suboptimal, it may be supplemented by nocturnal administration of specialized nutrition support. In a stable patient, if approximately 60%–70% of the caloric requirements are met by EN, PN may be withdrawn.

Immunonutrition and micronutrients

The potential to modulate the activity of the immune system through the intake of specific nutrients is termed immunonutrition. Perioperative immunonutrition has been found to have a crucial role in reducing infections, hospital length of stay, and mortality and in improving wound healing. Many trials and meta-analyses have shown benefits of immunonutrients (e.g., glutamine, arginine, omega-3 fatty acids) in reducing infections, hospital length of stay, and hospital costs and improving wound healing. Glutamine appears to effectively reduce the inflammatory response and intestinal mucosal permeability in patients with major abdominal surgery. Parenteral glutamine supplementation and omega-3 fatty acids may be considered in patients who cannot be fed adequately enterally. Immunonutrition should be started 5–7 days prior to surgery and continued in the postoperative period [18-21].

Micronutrients, which are trace elements and vitamins, are crucial for survival and should be administered to strengthen endogenous antioxidant defenses. Critically ill, hyper-metabolic patients have increased requirements for most micronutrients—in particular, vitamins C and E as well as zinc, copper, and selenium. Micronutrients should be supplemented parenterally until full enteral uptake is guaranteed. Emphasis on immunonutrients and micronutrients ensures comprehensive support through nutrition therapy [22].

ONS and hospital-based kitchen feeds

ONS offers a comprehensive package, unlike hospital-based kitchen feeds, which have an inadequate composition of macro- and micronutrients and carry the risk of contamination. Also, the quality of ingredients is suboptimal in kitchen feeds, and there is a problem with their consistency and tube blockage as well as osmolality. The key to preventing malabsorption and maldigestion is the use of appropriate formula feeds [23]. Salient features include the use of elemental (monomeric) and semi-elemental (oligomeric) formulas for tube feeding and specialized (polymeric) formula feeds for enteral feeding. Early postoperative feeding can reduce translocation and infections.

Nutritional management in the SICU patient

In critically ill surgical patients, achieving target goals with EN alone can be difficult. An inability to match energy–protein deficits, accrued early in illness, increases morbidity and mortality rates. Obligatory catabolism associated with prolonged mechanical ventilation, persistent shock, a non-functional gut, and peritonitis contributes further. The value of supplemental PN when energy requirements cannot be met by EN alone has been shown in numerous studies. There is often a delay in enteral feeding until patients are off vasopressor support and fully resuscitated. There is also fear of inducing intestinal complications, like anastomotic leaks, perforation, paralytic ileus, diarrhea, and high gastric residual volume (GRV). However, GRV does not correlate with incidence rates of pneumonia, regurgitation, and aspiration and should not be used as part of routine care to monitor intensive care unit patients on EN. Steps should be taken to reduce the risk of aspiration or improve tolerance to gastric feeding by administering prokinetic agents or continuous infusions, elevating the head end of the bed, and diverting feeding into the lower gastrointestinal tract using nasojejunal tubes [24]. Nasogastric feeding is simpler, cheaper, and easier to enact and is as effective as nasojejunal feeding. Early initiation of postpyloric feeding instead of gastric feeding does not appear to confer any clinically significant advantage. Routine use of postpyloric feeding is not recommended but should be promptly considered if gastroparesis is not resolved with prokinetics [25].

During the acute phase, trophic or hypocaloric feeding (≤70% of standard caloric targets) should be adopted. After beginning with 10–20 kcal/h and increasing to 500 kcal/day during the initial period, feeding should be increased as tolerated to >80% of the target energy after 24–48 hours. High protein intake (1.5 g/kg/day) is recommended during the early phase of SICU stay, regardless of the calorie intake goal in the first week. In the post-acute phase, 25–30 kcal/kg/day should be administered to prevent lean body mass reduction and maintain or improve muscle strength, which helps with early mobilization and improves functional recovery. Fluids containing dextrose and lipid-based medications like propofol are additional energy sources that need to be considered to avoid caloric overfeeding. Cautious initiation of PN is mandated in SICU patients with hemodynamic instability, high serum lactate levels not related to thiamine deficiency, acidosis, severe hepatic impairment, hyperglycemia, and hyperlipidemia. Increases in the blood urea nitrogen concentration may signify protein overload [22-26].

Postoperative care in ward

It is recommended to provide up to 30 kcal/kg/day and 1.2–2 g/kg/day of protein. Higher energy and proteins are required for a long period to regain lost muscle mass fully. Additionally, micronutrients and anabolic hormones help to restore lean mass. There is a need to commence rehabilitation exercises to improve quality of life.

Recommendations on discharge

The rehabilitation period can last for much longer than healthcare providers expect. Home artificial nutrition (EN or PN) for patients not able to fulfill nutritional requirements by themselves, along with a regular follow-up by a nutritional support team, is suggested. The late phase of recovery (from discharge to return to normal function) has received little attention in research and publications. Continuity of care remains an essential aspect of perioperative nutrition support.

Conclusion

Obstacles to nutrition practices in some countries include the poor realization of malnutrition as a significant problem. Regional differences in socioeconomic conditions, healthcare delivery systems, funding sources, and differing practices in various hospital settings are challenging environments for standardization. There is a definite division between public and private and between urban and rural institutions, and a standardized protocol is often lacking. Despite recognizing proper perioperative nutritional support and its potential value to patient outcomes, poor implementation of evidence-based nutrition practices remains. Most postoperative patients are not fed within the time frames outlined by evidence-based guidelines. Insufficient liquid and solid feeding practices and untimely upgrades of patients to nutritionally adequate diets are problems, particularly in a public hospital setting.

One can overcome existing challenges by emphasizing the fight against hospital malnutrition and highlighting malnutrition as a problem. Understanding and addressing nutrition practices early in the curriculum, offering periodic continuing medical education, encouraging interactions with key opinion leaders, and holding regular webinars will help. Initiatives like Nutrition Insights Day [27] and United for Clinical Nutrition will help to bridge the gap. ASCENT and regional societies like the Parenteral and Enteral Nutrition Society of India and the Indian Society of Parenteral and Enteral Nutrition could help in addressing this mission problem [28].

Currently, the emphasis is on newer and integrated multidisciplinary medical strategies, including ERAS and perioperative nutrition support, to promote optimal patient recovery following major surgery. However, more recent strides do not necessarily translate into safer and economically viable alternatives, and the basic tenets of safe nutrition practices must be followed.

The positive impact of comprehensive nutritional support and the importance of following set standards need to be highlighted. Emphasis should be placed on overcoming existing challenges in implementing nutrition therapy in current surgical practice, as better perioperative nutrition will lead to better surgical outcomes.

Authors’ contribution

Conceptualization: RJ, AK. Formal analysis: AK. Methodology: AK. Project administration: AK. Supervision: AK. Validation: AK. Writing – original draft: AK. Writing – review & editing: all authors.

Conflict of interest

The authors of this manuscript have no conflicts of interest to disclose.

Funding

None.

Data availability

None.

Acknowledgments

None.

Supplementary materials

None.

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