Nutritional assessment in the critically ill

Metabolic and the Surgical Stress Response Considerations to Improve Postoperative Recovery

PURPOSE OF REVIEW

Enhanced recovery pathways are a multimodal, multidisciplinary approach to patient care that aims to reduce the surgical stress response and maintain organ function resulting in faster recovery and improved outcomes.

RECENT FINDINGS

A PubMed literature search was performed for articles that included the terms of metabolic surgical stress response considerations to improve postoperative recovery. The surgical stress response occurs due to direct and indirect injuries during surgery. Direct surgical injury can result from the dissection, retraction, resection, and/or manipulation of tissues, while indirect injury is secondary to events including hypotension, blood loss, and microvascular changes. Greater degrees of tissue injury will lead to higher levels of inflammatory mediator and cytokine release, which ultimately drives immunologic, metabolic, and hormonal processes in the body resulting in the stress response. These processes lead to altered glucose metabolism, protein catabolism, and hormonal dysregulation among other things, all which can impede recovery and increase morbidity. Fluid therapy has a direct effect on intravascular volume and cardiac output with a resultant effect on oxygen and nutrient delivery, so a balance must be maintained without excessively loading the patient with water and salt. All in all, attenuation of the surgical stress response and maintaining organ and thus whole-body homeostasis through enhanced recovery protocols can speed recovery and reduce complications. The present investigation summarizes the clinical application of enhanced recovery pathways, and we will highlight the key elements that characterize the metabolic surgical stress response and improved postoperative recovery.

Perioperative catabolism

PURPOSE

This article reviews the pathophysiology, clinical relevance, and therapy of the catabolic response to surgical stress.

PRINCIPLE FINDINGS

The key clinical features of perioperative catabolism are hyperglycemia and loss of body protein, both metabolic consequences of impaired insulin function. Muscle weakness and (even moderate) increases in perioperative blood glucose are associated with morbidity after major surgery. Although the optimal glucose concentration for improving clinical outcomes is unknown, most medical associations recommend treatment of random blood glucose > 10 mmol·L(-1). Neuraxial anesthesia blunts the neuroendocrine stress response and enhances the anabolic effects of nutrition. There is evidence to suggest that the avoidance of preoperative fasting prevents insulin resistance and accelerates recovery after major abdominal surgery.

CONCLUSIONS

Current anticatabolic therapeutic strategies include glycemic control and perioperative nutrition in combination with optimal pain control and the avoidance of preoperative starvation. All these elements are part of Enhanced Recovery After Surgery (ERAS) programs.

The anabolic effect of perioperative nutrition depends on the patient's catabolic state before surgery

OBJECTIVE

We tested the hypothesis that the anabolic effect of hypocaloric, isonitrogenous nutrition in patients undergoing colorectal surgery depends on the patient's preoperative catabolic state.

BACKGROUND

Although there is evidence to suggest that total parenteral nutrition more effectively spares protein in depleted than in nondepleted cancer patients, the influence of preoperative catabolism on the anabolic effects of hypocaloric nutrition in patients undergoing elective surgery is unknown.

METHODS

Seventeen patients undergoing colorectal surgery received intravenous infusion of glucose with amino acids. Feeding was administered over 72 hours, from 24 hours before until 48 hours after surgery. Glucose provided 50% of the patient's measured resting energy expenditure. Amino acids provided 20% of the resting energy expenditure. Whole-body leucine balance (difference between the incorporation of leucine into protein = protein synthesis and endogenous leucine release = proteolysis) was determined using L-[1-(13)C]leucine kinetics before and 2 days after surgery. We analyzed the association between the postoperative increase in leucine balance and the following factors: preoperative leucine balance, protein breakdown, weight loss, oxygen consumption, circulating concentrations of glucose, free fatty acids, insulin, glucagon, cortisol, albumin, age, duration of surgery, and blood loss.

RESULTS

Of 6 potentially relevant variables, 4 (weight loss, protein breakdown, albumin, and cortisol) were removed because they were not significant during the stepwise linear regression procedure. Leucine balance and age were the remaining 2 factors that remained with the final regression model: Δleucine balance = 19.1 - (0.20 × age [years]) - (0.58) × leucine balance(preOP)).

CONCLUSIONS

We demonstrate a significant association between the degree of preoperative catabolism, the patient's age, and the anabolic effect of hypocaloric nutrition (ClinicalTrials.gov registration ID: NCT01414946).

Human serum albumin: from bench to bedside

Human serum albumin (HSA), the most abundant protein in plasma, is a monomeric multi-domain macromolecule, representing the main determinant of plasma oncotic pressure and the main modulator of fluid distribution between body compartments. HSA displays an extraordinary ligand binding capacity, providing a depot and carrier for many endogenous and exogenous compounds. Indeed, HSA represents the main carrier for fatty acids, affects pharmacokinetics of many drugs, provides the metabolic modification of some ligands, renders potential toxins harmless, accounts for most of the anti-oxidant capacity of human plasma, and displays (pseudo-)enzymatic properties. HSA is a valuable biomarker of many diseases, including cancer, rheumatoid arthritis, ischemia, post-menopausal obesity, severe acute graft-versus-host disease, and diseases that need monitoring of the glycemic control. Moreover, HSA is widely used clinically to treat several diseases, including hypovolemia, shock, burns, surgical blood loss, trauma, hemorrhage, cardiopulmonary bypass, acute respiratory distress syndrome, hemodialysis, acute liver failure, chronic liver disease, nutrition support, resuscitation, and hypoalbuminemia. Recently, biotechnological applications of HSA, including implantable biomaterials, surgical adhesives and sealants, biochromatography, ligand trapping, and fusion proteins, have been reported. Here, genetic, biochemical, biomedical, and biotechnological aspects of HSA are reviewed.

Enhanced albumin synthesis in severely burned adults

Albumin plays an important role in maintaining physiological homeostasis. Although decreased albumin concentration has been well described as an acute-phase response following injury, it is unclear whether the decrease is due to compromised synthesis of albumin, dilution, or imbalance between synthesis and breakdown rates, particularly after injury. We investigated changes in albumin synthesis in severely burned patients using stable isotope infusion techniques. Five patients (29 ± 3 years; 80 ± 7 kg) with burn of 48% ± 4% total body surface area (TBSA) were enrolled and studied in the ICU at the Burn Unit of the US Army Institute of Surgical Research. Five age- and sex-matched healthy volunteers (33 ± 5 years; 81 ± 6 kg) were included as controls. On the study day (13 ± 3 days after burn), a primed constant infusion (4 h) of stable isotope d5-phenlylalanine and d3-ketoisocaproic acid was given. Hourly arterial blood samples were drawn during the infusion to determine albumin synthesis rates, using gas chromatography-mass spectrometry analysis. Burned patients had higher heart and respiration rates. Plasma total protein in burn patients (4.5 ± 0.3 g · dL-1) was lower compared with controls (6.8 ± 0.2 g · dL-1). Plasma albumin concentration in burn patients (1.1 ± 0.1 g · dL-1) was also lower compared with controls (3.8 ± 0.1 g · dL-1; both P < 0.05). Albumin synthesis rate in burn patients (4.6 ± 0.2 mg · kg-1 · h-1) was enhanced compared with controls (2.2 ± 0.2 mg · kg-1 · h-1; P < 0.05). Despite the decrease in albumin concentration, albumin synthesis was enhanced in severely burned patients during the flow phase.

Albumin therapy in clinical practice

Albumin is the predominant product of hepatic protein synthesis and one of the more abundant plasma proteins. Among its multiple physiologic roles, it plays an essential part in the generation of colloid-oncotic pressure. In the United States, the indications for which albumin therapy are considered include hypovolemia or shock, burns, hypoalbuminemia, surgery or trauma, cardiopulmonary bypass, acute respiratory distress syndrome, hemodialysis, and sequestration of protein-rich fluids. The use of this relatively expensive therapy accounts for up to 30% of the total pharmacy budget in certain hospitals. The use of albumin therapy in different clinical situations and its influence in morbidity and mortality have been reviewed in multiple randomized controlled trials and meta-analyses. Despite frequent reviews, the use of albumin remains controversial in several clinical situations. At the same time, these valuable reviews seem to have documented the advantages of albumin therapy in the management of ascites and clarified the use of albumin in volume resuscitation. More studies have been recommended to investigate the use of albumin in different doses and its role in hypoalbuminemia. This article will provide an overview of albumin metabolism, use of albumin for volume expansion, the potential therapeutic role of albumin in liver disease, and the role of albumin therapy in nutrition.

Surgical management of high output enterocutaneous fistulae: a 24-year experience

PURPOSE OF REVIEW

Enterocutaneous fistulae are abnormal communications between the small or large bowel and the skin, which may be lined with epithelium or associated with intra-abdominal sepsis. Patients with high fluid and electrolyte losses are best managed in a nutrition unit by a dedicated team of physicians and other healthcare workers. Despite recent advances in the management of these patients, the mortality rate ranges between 10 and 20%. It is therefore imperative that attention must be paid to well-designed management protocols.

RECENT FINDINGS

A total of 494 patients with high-output enterocutaneous fistulae were reviewed over a 24-year period. The overall mortality rate of the patients was 13%. A pilot study evaluating somatostatin in combination with total parenteral nutrition showed promise in the conservative management of high-output enterocutanous fistulae, but the use of somatostatin is controversial, and it should not be used routinely. Although H2 receptor antagonists and proton pump inhibitors decrease gastric secretions, they do not help in closing enterocutaneous fistulae.

SUMMARY

Sepsis, in all its forms, is an important cause of morbidity and mortality and requires aggressive treatment. Definitive surgical closure of the fistula should only be performed when the patient is apyrexial and in good nutritional status, and if the fistula effluent shows no signs of decreasing in volume after 4-6 weeks of nutritional support. All reviews of patients with enterocutaneous fistulae reveal that the best results with the least morbidity are obtained by definitive resection and end-to-end anastomoses.

Usefulness of short-lived proteins as nutritional indicators surgical patients

BACKGROUND AND AIMS

Biochemical indicators are used to assess the adequacy of nutritional support given to postoperative patients. However, the metabolic alterations present in these patients diminish the efficiency of these indicators. The objective of this work is to determine the usefulness of short-lived proteins as indicators to assess the nutritional support administered to patients during the metabolic stress phase produced by surgery.

METHODS

The nitrogen balance and plasma concentrations of transthyretin, retinol binding protein, and insulin-like growth factor-1 were determined in 24 patients who received 4 different nutritional regimens during 7 days after surgery.

RESULTS

Transthyretin and retinol binding protein, although sensitive to nutritional intake (P<0.0005 and P<0.04 respectively), were strongly affected by the stress response (P<0.008 and P<0.0003 respectively), thus limiting their usefulness for nutrition assessment. Insulin-like growth factor-1 was not influenced by the stress response and was sensitive to the nutritional supply (P<0.0001). Insulin-like growth factor-1 was the only component that showed similar efficiency than nitrogen balance as nutritional indicator.

CONCLUSIONS

Transthyretin and retinol binding protein are not adequate to assess the nutritional supply during the stress phase after surgery, while insulin-like growth factor-1 is a suitable indicator of the adequacy of recent intake in this situation, similar in performance to nitrogen balance.