Impact of the nutritional regimen on protein catabolism and nitrogen balance in patients with acute renal failure

Clearance and nutrition in neonatal continuous kidney replacement therapy using the Carpediem™ system

BACKGROUND

Infants with kidney failure (KF) demonstrate poor growth partly due to obligate fluid and protein restrictions. Delivery of liberalized nutrition on continuous kidney replacement therapy (CKRT) is impacted by clinical instability, technical dialysis challenges, solute clearance, and nitrogen balance. We analyzed delivered nutrition and growth in infants receiving CKRT with the Cardio-Renal, Pediatric Dialysis Emergency Machine (Carpediem™).

METHODS

Single-center observational study of infants receiving CKRT with the Carpediem™ between June 1 and December 31, 2021. We collected prospective circuit characteristics, delivered nutrition, anthropometric measurements, and illness severity Score for Neonatal Acute Physiology-II. As a surrogate to normalized protein catabolic rate in maintenance hemodialysis, we calculated normalized protein nitrogen appearance (nPNA) using the Randerson II continuous dialysis model. Descriptive statistics, Spearman correlation coefficient, Mann Whitney, Wilcoxon signed rank, receiver operating characteristic curves, and Kruskal-Wallis analysis were performed using SAS version 9.4.

RESULTS

Eight infants received 31.9 (22.0, 49.7) days of CKRT using mostly (90%) regional citrate anticoagulation. Delivered nutritional volume, protein, total calories, enteral calories, nPNA, and nitrogen balance increased on CKRT. Using parenteral nutrition, 90 ml/kg/day should meet caloric and protein needs. Following initial weight loss of likely fluid overload, exploratory sensitivity analysis suggests weight gain occurred after 14 days of CKRT. Despite adequate nutritional delivery, goal weight (z-score = 0) and growth velocity were not achieved until 6 months after CKRT start. Most (5 infants, 62.5%) survived and transitioned to peritoneal dialysis (PD).

CONCLUSIONS

Carpediem™ is a safe and efficacious bridge to PD in neonatal KF. Growth velocity of infants on CKRT appears delayed despite delivery of adequate calories and protein.

A Proposed Predictive Equation for Energy Expenditure Estimation Among Noncritically Ill Patients With Acute Kidney Injury

OBJECTIVE

The incidence of acute kidney injury (AKI) is identified more frequently in noncritical compared with intensive care settings. The prognosis of malnourished AKI patients is far worse than those with normal nutritional status. However, a method for estimating the optimal amount of energy required to guide nutritional support among noncritically ill AKI patients is yet to be determined.

METHODS

We evaluated the performance of weight-based formulas (20-30 kcal/kg/day) with the reference values of energy expenditure (EE) measured by indirect calorimetry (IC) among noncritically ill AKI patients during hospitalization. The statistics for assessing agreement, including total deviation index and accuracy within 10% represent the percentage of estimations falling within the IC value range of ±10%, were tested. Parameters for predicting the EE equation were also developed using a regression analysis model.

RESULTS

A total of 40 noncritically ill AKI patients were recruited. The mean age of participants was 62.5 ± 16.5 years with 50% being male. The average IC-derived EE was 1,124.6 ± 278.9 kcal/day with respiratory quotients 0.8-1.3, indicating good validity of the IC test. Receiving dialysis, protein catabolic rate, and age was not significantly associated with measured EE. Nearly all weight-based formulas overestimated measured EE. The magnitude of total deviation index values was broad with the proportion of patients achieving an accuracy of 10% being as low as 20%. The proposed equation to predict EE derived from this study was EE (kcal/day) = 618.27 + (8.98 x weight in kg) + 137.0 if diabetes - 199.7 if female (r2 = 0.68, P < .001). In the validation study with an independent group of noncritically ill AKI patients, predicted EE using the newly derived equation was also significantly correlated with measured EE by IC (r = 0.69, P = .004).

CONCLUSION

Estimation of EE by weight-based formulas usually overestimated measured EE among noncritically ill AKI patients. In the absence of IC, the proposed predictive equation, specifically for noncritically ill AKI patients might be useful, in addition to weight-based formulas, for guiding caloric dosing in clinical practice.

The effect of continuous venovenous hemodiafiltration on amino acid delivery, clearance, and removal in children

BACKGROUND

In critically ill children with acute kidney injury (AKI), continuous kidney replacement therapy (CKRT) enables nutrition provision. The magnitude of amino acid loss during continuous venovenous hemodiafiltration (CVVHDF) is unknown and needs accurate quantification. We investigated the mass removal and clearance of amino acids in pediatric CVVHDF.

METHODS

This is a prospective observational cohort study of patients receiving CVVHDF from August 2014 to January 2016 in the pediatric intensive care unit (PICU) of a tertiary children's hospital.

RESULTS

Fifteen patients (40% male, median age 2.0 (IQR 0.7, 8.0) years) were enrolled. Median PICU and hospital lengths of stay were 20 (9, 59) and 36 (22, 132) days, respectively. Overall survival to discharge was 66.7%. Median daily protein prescription was 2.00 (1.25, 2.80) g/kg/day. Median daily amino acid mass removal was 299.0 (174.9, 452.0) mg/kg body weight, and median daily amino acid mass clearance was 18.2 (13.5, 27.9) ml/min/m², resulting in a median 14.6 (8.3, 26.7) % protein loss. The rate of amino acid loss increased with increasing dialysis dose and blood flow rate.

CONCLUSION

CVVHDF prescription and related amino acid loss impact nutrition provision, with 14.6% of the prescribed protein removed. Current recommendations for protein provision for children requiring CVVHDF should be adjusted to compensate for circuit-related loss. A higher resolution version of the Graphical abstract is available as Supplementary information.

Nutritional assessment and support during continuous renal replacement therapy

Malnutrition is highly prevalent in patients with acute kidney injury, especially in those receiving renal replacement therapy (RRT). For the assessment of nutritional status, a combination of screening tools, anthropometry, and laboratory parameters is recommended rather than a single test. To avoid underfeeding and overfeeding during RRT, energy expenditure should be measured by indirect calorimetry or calculated using predictive equations. Nitrogen balance should be periodically measured to assess the degree of catabolism and to evaluate protein intake. However, there is limited data for nutritional targets specifically for patients on RRT, such as protein intake. The composition of commercial solutions for continuous renal replacement therapy (CRRT) varies. CRRT itself can be associated with both, nutrient losses into the effluent fluid and caloric gain from dextrose, lactate, and citrate. The role of micronutrient supplementation, and potential use of micronutrient enriched CRRT solutions in this setting is unknown, too. This review provides an overview of existing knowledge and uncertainties related to nutritional aspects in patients on CRRT and emphasizes the need for more research in this area.

ESPEN guideline on clinical nutrition in hospitalized patients with acute or chronic kidney disease

Acute kidney disease (AKD) - which includes acute kidney injury (AKI) - and chronic kidney disease (CKD) are highly prevalent among hospitalized patients, including those in nephrology and medicine wards, surgical wards, and intensive care units (ICU), and they have important metabolic and nutritional consequences. Moreover, in case kidney replacement therapy (KRT) is started, whatever is the modality used, the possible impact on nutritional profiles, substrate balance, and nutritional treatment processes cannot be neglected. The present guideline is aimed at providing evidence-based recommendations for clinical nutrition in hospitalized patients with AKD and CKD. Due to the significant heterogeneity of this patient population as well as the paucity of high-quality evidence data, the present guideline is to be intended as a basic framework of both evidence and - in most cases - expert opinions, aggregated in a structured consensus process, in order to update the two previous ESPEN Guidelines on Enteral (2006) and Parenteral (2009) Nutrition in Adult Renal Failure. Nutritional care for patients with stable CKD (i.e., controlled protein content diets/low protein diets with or without amino acid/ketoanalogue integration in outpatients up to CKD stages four and five), nutrition in kidney transplantation, and pediatric kidney disease will not be addressed in the present guideline.

Enteral Nutrition in the Mechanically Ventilated Patient

Mechanically ventilated patients are unable to take food orally and therefore are dependent on enteral nutrition for provision of both energy and protein requirements. Enteral nutrition is supportive therapy and may impact patient outcomes in the intensive care unit. Early enteral nutrition has been shown to decrease complications and hospital length of stay and improve the prognosis at discharge. Nutrition support is unique for patients on mechanical ventilation and, as recently published literature shows, should be tailored to the individuals' underlying pathology. This review will discuss the most current literature and recommendations for enteral nutrition in patients receiving mechanical ventilation.

Continuous Renal Replacement Therapy: Who, When, Why, and How

Continuous renal replacement therapy (CRRT) is commonly used to provide renal support for critically ill patients with acute kidney injury, particularly patients who are hemodynamically unstable. A variety of techniques that differ in their mode of solute clearance may be used, including continuous venovenous hemofiltration with predominantly convective solute clearance, continuous venovenous hemodialysis with predominantly diffusive solute clearance, and continuous venovenous hemodiafiltration, which combines both dialysis and hemofiltration. The present article compares CRRT with other modalities of renal support and reviews indications for initiation of renal replacement therapy, as well as dosing and technical aspects in the management of CRRT.

Low caloric and protein intake is associated with mortality in patients with acute kidney injury

BACKGROUND

Acute renal injury (AKI) interferes greatly with nutritional status, affecting the metabolism of all macronutrients and increased mortality rates in hospitalized patients. Our objective was to evaluate the association of nutritional parameters (albumin, cholesterol, caloric and protein intake and nitrogen balance (NB)) with mortality in patients with AKI.

METHODS

This is a prospective observational study that evaluated 595 consecutive patients over the age of 18 years with AKI, requiring enteral or parenteral feeding. At the time of the patient's enrollment, demographic and laboratorial data, caloric and protein supply and NB were recorded on the first day of referral to the nephrologist. All patients were followed throughout the hospital stay and mortality rate was also recorded.

RESULTS

The medium age of patients with AKI was 64 (54-75) years, 64.5% male, 62% admitted to intensive care unit (ICU), 52% on dialysis and the majority (48%) were at stage 3 by AKIN. Length of stay and hospital mortality were 18 (10-31) days and 46%, respectively. Superior age, AKI severity, lower body weight and body mass index (BMI), higher need for dialysis, ICU admission and shorter hospital stay were associated with higher mortality. At logistic regression, caloric (OR: 0.946; CI:95%: 0.901-0.994; p:0.029) and protein intake (OR: 0.947; CI:95%: 0.988-0.992; p = 0.028) and serum albumin (OR: 0.545; CI:95%: 0.401-0741; p < 0.001) were associated with hospital mortality. Cholesterol (OR: 0.995; CI:95%: 0.991-1.000; p = 0.052) was not associated with increased mortality in the adjusted analysis. Analysis of the receiver operating characteristic (ROC) curve showed that calorie intake < 12 kcal/kg (AUC: 0.745; CI:95%: 0.684-0.765; p < 0.001) and protein intake < 0.5 g/kg (AUC: 0.726; CI:95%: 0.686-0.767; p < 0.001) were predictors of hospital mortality, as well as a negative NB < -6.47 g N/day (AUC: 0.745; CI:95%: 0.704-0.786; p < 0.001).

CONCLUSIONS

In conclusion, low caloric and protein intake, negative NB and low albumin value are conditions associated with higher hospital mortality in patients with AKI.

Energy and Protein in Critically Ill Patients with AKI: A Prospective, Multicenter Observational Study Using Indirect Calorimetry and Protein Catabolic Rate

The optimal nutritional support in Acute Kidney Injury (AKI) still remains an open issue. The present study was aimed at evaluating the validity of conventional predictive formulas for the calculation of both energy expenditure and protein needs in critically ill patients with AKI. A prospective, multicenter, observational study was conducted on adult patients hospitalized with AKI in three different intensive care units (ICU). Nutrient needs were estimated by different methods: the Guidelines of the European Society of Parenteral and Enteral Nutrition (ESPEN) for both calories and proteins, the Harris-Benedict equation, the Penn-State and Faisy-Fagon equations for energy. Actual energy and protein needs were repeatedly measured by indirect calorimetry (IC) and protein catabolic rate (PCR) until oral nutrition start, hospital discharge or renal function recovery. Forty-two patients with AKI were enrolled, with 130 IC and 123 PCR measurements obtained over 654 days of artificial nutrition. No predictive formula was precise enough, and Bland-Altman plots wide limits of agreement for all equations highlight the potential to under- or overfeed individual patients. Conventional predictive formulas may frequently lead to incorrect energy and protein need estimation. In critically ill patients with AKI an increased risk for under- or overfeeding is likely when nutrient needs are estimated instead of measured.

Prevention and Therapy of Acute Kidney Injury in the Developing World

Timely recognition of patients at risk or with possible acute kidney injury (AKI) is essential for early intervention to minimize further damage and improve outcome. Initial management of patients with suspected and persistent AKI should include thorough clinical assessment of all patients with AKI to identify reversible factors, including fluid volume status, potential nephrotoxins, and an assessment of the underlying health of the kidney. Based on these assessments, early interventions to provide appropriate and adequate fluid resuscitation while avoiding fluid overload, removal of nephrotoxins, and adjustment of drug doses according to the level of kidney function derangement are important. The judicious use of diuretics for fluid overload and/or in cardiac decompensated patients and introduction of early enteral nutritional support need to be considered to improve outcomes in AKI. Although these basic principles are well recognized, their application in clinical practice in low resource settings is often limited due to lack of education, availability of resources, and lack of trained personnel, which limits access to care. We report the consensus recommendations of the 18th Acute Dialysis Quality Initiative meeting in Hyderabad, India, on strategies to evaluate patients with suspected AKI and initiate measures for prevention and management to improve outcomes, particularly in low resource settings. These recomendations provide a framework for caregivers, who are often primary care physicians, nurses, and other allied healthcare personnel, to manage patients with AKI in resource poor countries.

Issues of Acute Kidney Injury Staging and Management in Sepsis and Critical Illness: A Narrative Review

Acute kidney injury (AKI) has a high incidence on intensive care units around the world and is a major complication in critically ill patients suffering from sepsis or septic shock. The short- and long-term complications are thereby devastating and impair the quality of life. Especially in terms of AKI staging, the determination of kidney function and the timing of dialytic AKI management outside of life-threatening indications are ongoing matters of debate. Despite several studies, a major problem remains in distinguishing between beneficial and unnecessary "early" or even harmful renal replacement therapy (RRT). The latter might prolong disease course and renal recovery. AKI scores, however, provide an insufficient outcome-predicting ability and the related estimation of kidney function via serum creatinine or blood urea nitrogen (BUN)/urea is not reliable in AKI and critical illness. Kidney independent alterations of creatinine- and BUN/urea-levels further complicate the situation. This review critically assesses the current AKI staging, issues and pitfalls of the determination of kidney function and RRT timing, as well as the potential harm reflected by unnecessary RRT. A better understanding is mandatory to improve future study designs and avoid unnecessary RRT for higher patient safety and lower health care costs.

Estimating Catabolism: A Possible Tool for Nutritional Monitoring of Patients With Acute Kidney Injury

Hypercatabolism has been described as the main nutritional change in acute kidney injury. Catabolism may be defined as the excessive release of amino acids from skeletal muscle. Conditions such as fasting, inadequate nutritional support, renal replacement therapy, metabolic acidosis, and secretion of catabolic hormones are the main factors that affect protein catabolism. Given the imprecision of the methods conventionally used to assess and monitor the nutritional status of hospitalized patients, the parameters of protein catabolism, such as nitrogen balance, urea nitrogen appearance, and protein catabolic rate appear to be the main measures in this population. Considering the high prevalence of malnutrition in this population and important limitations in this clinical condition, such as the inflammatory state and altered fluid, catabolism parameters are accurate and reliable methods that could contribute to minimize adverse prognosis in this population.

The Impact of Macro-and Micronutrients on Predicting Outcomes of Critically Ill Patients Requiring Continuous Renal Replacement Therapy

Critically ill patients with acute kidney injury (AKI) who receive renal replacement therapy (RRT) have very high mortality rate. During RRT, there are markedly loss of macro- and micronutrients which may cause malnutrition and result in impaired renal recovery and patient survival. We aimed to examine the predictive role of macro- and micronutrients on survival and renal outcomes in critically ill patients undergoing continuous RRT (CRRT). This prospective observational study enrolled critically ill patients requiring CRRT at Intensive Care Unit of King Chulalongkorn Memorial Hospital from November 2012 until November 2013. The serum, urine, and effluent fluid were serially collected on the first three days to calculate protein metabolism including dietary protein intake (DPI), nitrogen balance, and normalized protein catabolic rate (nPCR). Serum zinc, selenium, and copper were measured for micronutrients analysis on the first three days of CRRT. Survivor was defined as being alive on day 28 after initiation of CRRT.Dialysis status on day 28 was also determined. Of the 70 critically ill patients requiring CRRT, 27 patients (37.5%) survived on day 28. The DPI and serum albumin of survivors were significantly higher than non-survivors (0.8± 0.2 vs 0.5 ±0.3g/kg/day, p = 0.001, and 3.2±0.5 vs 2.9±0.5 g/dL, p = 0.03, respectively) while other markers were comparable. The DPI alone predicted patient survival with area under the curve (AUC) of 0.69. A combined clinical model predicted survival with AUC of 0.78. When adjusted for differences in albumin level, clinical severity score (APACHEII and SOFA score), and serum creatinine at initiation of CRRT, DPI still independently predicted survival (odds ratio 4.62, p = 0.009). The serum levels of micronutrients in both groups were comparable and unaltered following CRRT. Regarding renal outcome, patients in the dialysis independent group had higher serum albumin levels than the dialysis dependent group, p = 0.01. In conclusion, in critically ill patients requiring CRRT, DPI is a good predictor of patient survival while serum albumin is a good prognosticator of renal outcome.

The Use of Transpyloric Enteral Nutrition in the Critically Ill Child

To assess the use and complications of transpyloric enteral nutrition (TEN) in the critically ill child we evaluated prospectively all children who received TEN in a pediatric intensive care unit (PICU) of a tertiary university hospital. The type of nutrition used, its duration, medication administered, tolerance, gastrointestinal complications (vomiting, abdominal distension or excessive gastric residue, diarrhea, and pulmonary aspiration), nongastrointestinal complications, and mortality were assessed. A comparative analysis was made between the first 2 years of the study and the remaining period. Over a period of 4.5 years, 152 patients between the ages of 3 days and 17 years received TEN for a duration of 19 ± 32.3 days (range 1–240 days). Forty-one patients received TEN during the first 2 years; 100 patients received TEN in the postoperative period after cardiac surgery (66%). One hundred seventeen patients (77%) received sedation and 65 (43%) received muscle relaxants, presenting no extra complications. Twenty-four patients (15.8%) presented with gastrointestinal complications: abdominal distension and/or excessive gastric residue in 17 and diarrhea in 11. Gastrointestinal intolerance was associated with pulmonary infection ( p < 0.05), altered hepatic function ( p < 0.001), and hypokalemia or hypocalcemia ( p < 0.05). Diarrhea was more frequent in patients with shock ( p < 0.05), altered hepatic function ( p < 0.05), excessive gastric residue ( p < 0.001), and hypokalemia or hypocalcemia ( p < 0.05). In the second study period, the number of patients on TEN and the doses of sedatives, muscle relaxants, and vasoactives were higher ( p < 0.05), with no increase in the incidence of complications. TEN is a useful method of nutrition with few complications in the critically ill child.

Critical care: Meeting protein requirements without overfeeding energy

BACKGROUND AND AIMS

Relatively high protein input has been associated with improved clinical outcome in critical illness. However, until recently differences in clinical outcome have been examined in terms of the energy goal-versus under-feeding. Most studies failed to set the energy goal by an accurate measure or estimate of expenditure or independently set protein prescription. This leads to under-prescription of protein, possibly adversely affecting outcome. We determined whether an enteral nutrition prescription could meet local and international protein guidelines.

METHODS

Protein prescriptions of consecutive patients admitted to Southmead Hospital ICU and requiring full enteral nutrition were audited against local and international guidelines. Prescriptions were designed to not exceed energy expenditure based on a validated estimation equation, minus non-nutritional energy, and protein requirements were based on local or international guidelines of between 1.2 and 2.5 g protein/kg/d or 2-2.5/kg ideal body weight (Hamwi ideal body weight)/d.

RESULTS

From 15/1/15 to 12/4/15 139 ICU patients were prescribed full enteral nutrition. Protein prescriptions failed to meet local guidelines in 75% (p < 0.001) and international guidelines in 45-100%. Prescriptions meeting at least 90% of protein guidelines and 130 g of carbohydrate could be increased from between 0 and 55%, depending on the guideline, to between 53 and 94% using a protein supplement and 82 and 100% using a protein plus glucose supplement. Non-nutritional energy (NNE) proportionately reduces feed protein prescription and contributed 19% of energy expenditure in 10% of patients.

CONCLUSIONS

We need feeds with a lower non-protein energy: nitrogen (NPE:gN) ratio and/or protein supplementation if prescriptions are to meet protein guidelines for critical illness. NNE must be adjusted for in prescriptions to ensure protein needs are met.

Specialized nutritional support interventions in critically ill patients on renal replacement therapy

PURPOSE OF REVIEW

Optimal nutritional requirements and nutrient intake composition for patients with acute kidney injury remain a partially unresolved issue. Targeting nutritional support to the actual protein and energy needs improves the clinical outcome of critically ill patients, yet very few data are currently available on this topic in acute kidney injury. In this specific clinical condition the risk for underfeeding and overfeeding may be increased by factors interfering on nutrient need estimation, such as rapidly changing body weight due to fluid balance variations, nutrient losses and hidden calorie sources from renal replacement therapy. Moreover, as acute kidney injury is now considered a kidney-centered inflammatory syndrome, the renoprotective role of specific pharmaconutrients with anti-inflammatory properties remains to be fully defined. This review is aimed at discussing recently published results concerning quantitative and qualitative aspects of the nutritional approach to acute kidney injury in critically ill patients.

RECENT FINDINGS

Nutrient needs in patients with acute kidney injury can be difficult to estimate, and should be directly measured, especially in the ICU setting. In fact, recent findings suggest that hidden calorie sources not routinely taken into account - for example, calories from anticoagulants and replacement solutions for renal replacement therapy - could be quantitatively relevant in these patients. Moreover, recent experimental data indicate a possible role for some pharmaconutrients with anti-inflammatory effects (glutamine, and omega-3 fatty acids), in both the prevention of renal function worsening, and in the fostering of renal function recovery after an episode of acute kidney injury.

SUMMARY

Acute kidney injury includes a highly heterogeneous group of patients with widely varying nutrient needs and intakes. Nutritional requirements, in their quantitative and qualitative aspects, should be frequently assessed, individualized, and carefully integrated with renal replacement therapy, in order to avoid both underfeeding and overfeeding, as well as to exploit possible positive pharmacologic effects of specific nutrients.

Adequacy of early enteral nutrition in adult patients in the intensive care unit

AIMS AND OBJECTIVES

To evaluate the adequacy of energy and protein intake of patients in a Korean intensive care unit in the first four days after initiation of enteral feeding and to investigate the factors that had impact on adequate intake.

BACKGROUND

Underfeeding is a common problem for patients hospitalised in the intensive care unit and is associated with severe negative consequences, including increased morbidity and mortality.

DESIGN

A prospective, cohort study was conducted in a medical intensive care unit of a university hospital in Korea.

METHODS

A total of 34 adult patients who had a primary medical diagnosis and who had received bolus enteral nutrition for the first four days after initiation of enteral nutrition were enrolled in this study. The data on prescription and intake of energy and protein, feeding method and feeding interruption were recorded during the first four days after enteral feeding initiation. Underfeeding was defined as the intake <90% of required energy and protein.

RESULTS

Most patients (62%) received insufficient energy, although some (29%) received adequate energy. More than half of patients (56%) had insufficient protein intake during the first four days after enteral feeding was initiated. Logistic regression analysis showed that the factors associated with underfeeding of energy were early initiation of enteral nutrition, under-prescription of energy and prolonged interruption of prescribed enteral nutrition.

CONCLUSION

Underfeeding is frequent in Korean critically ill patients owing to early initiation, under-prescription and prolonged interruption of enteral feeding.

RELEVANCE TO CLINICAL PRACTICE

  Interventions need to be developed and tested that address early initiation, under-prescription and prolonged interruption of enteral nutrition. Findings from this study are important as they form the foundation for the development of evidence-based care that is badly needed to eliminate underfeeding in this large vulnerable Korean intensive care unit population.

[Guidelines for specialized nutritional and metabolic support in the critically-ill patient. Update. Consensus of the Spanish Society of Intensive Care Medicine and Coronary Units-Spanish Society of Parenteral and Enteral Nutrition (SEMICYUC-SENPE): acute renal failure]

Nutritional support in acute renal failure must take into account the patient's catabolism and the treatment of the renal failure. Hypermetabolic failure is common in these patients, requiring continuous renal replacement therapy or daily hemodialysis. In patients with normal catabolism (urea nitrogen below 10 g/day) and preserved diuresis, conservative treatment can be attempted. In these patients, relatively hypoproteic nutritional support is essential, using proteins with high biological value and limiting fluid and electrolyte intake according to the patient's individual requirements. Micronutrient intake should be adjusted, the only buffering agent used being bicarbonate. Limitations on fluid, electrolyte and nitrogen intake no longer apply when extrarenal clearance techniques are used but intake of these substances should be modified according to the type of clearance. Depending on their hemofiltration flow, continuous renal replacement systems require high daily nitrogen intake, which can sometimes reach 2.5 g protein/kg. The amount of volume replacement can induce energy overload and therefore the use of glucose-free replacement fluids and glucose-free dialysis or a glucose concentration of 1 g/L, with bicarbonate as a buffer, is recommended. Monitoring of electrolyte levels (especially those of phosphorus, potassium and magnesium) and of micronutrients is essential and administration of these substances should be individually-tailored.

Relationship of Acute Phase Reactants and Fat Accumulation during Treatment for Tuberculosis

Background. Tuberculosis causes inflammation and muscle wasting. We investigated how attenuation of inflammation relates to repletion of body composition during treatment in an underserved population. Design. Twenty-four patients (23 to 79 years old) with pulmonary tuberculosis and inflammation (pretreatment albumin = 2.96 ± 0.13 g/dL, C-reactive protein [CRP] = 6.71 ± 1.34 μg/dL, and beta-2-microglobulin = 1.68 ± 0.10 μg/L) were evaluated and had BIA over 24 weeks. Results. Weight increased by 3.02 ± 0.81 kg (5.5%; P = 0.007) at week 4 and by 8.59 ± 0.97 kg (15.6%; P < 0.0001) at week 24. Repletion of body mass was primarily fat, which increased by 2.09 ± 0.52 kg at week 4 and 5.05 ± 0.56 kg at week 24 (P = 0.004 and P < 0.0001 versus baseline). Fat-free mass (FFM), body cell mass (BCM), and phase angle did not increase until study week 8. Albumin rose to 3.65 ± 0.14 g/dL by week 4 (P < 0.001) and slowly increased thereafter. CRP levels declined by ∼50% at each interval visit. Conclusions. During the initial treatment, acute phase reactants returned towards normal. The predominant accrual of fat mass probably reflects ongoing, low levels of inflammation.

Longitudinal hemodiafilter performance in modeled continuous renal replacement therapy

BACKGROUND/AIMS

With advanced anticoagulation, many institutions operate continuous renal replacement therapy (CRRT) circuits longer than manufacturers' recommendations. This extended use may change hemodiafilter performance and clearance properties. However, hemodiafilter performance over time has not been assessed. We investigated solute clearance over time in modeled CRRT.

METHODS

In vitro continuous hemofiltration (CH) and continuous hemodialysis (CD) were operated for 48 h using AN69 polyacrylonitrile, cellulose triacetate, F70 polysulfone, and Optiflux F160NR polysulfone hemodiafilters with citrated bovine blood. Urea, creatinine, gentamicin, vancomycin, and albumin clearances were assessed in CH (ultrafiltration rates = 1 and 3 l/h). Clearances of urea, creatinine, gentamicin, and albumin, were assessed in CD with dialysate flow rate of 2 l/h.

RESULTS

Solute CH clearances were significantly higher at 3 l/h. Only creatinine and gentamicin clearances were affected by time. Creatinine CD clearance significantly declined at 48 h for all hemodiafilters, especially polysulfone hemodiafilters.

CONCLUSIONS

CRRT duration affects solute transmembrane clearance. Clinicians should consider hemodiafilter age when assessing hemodialysis dose or drug clearance.

Specific nutritional problems in acute kidney injury, treated with non-dialysis and dialytic modalities

Patients who develop AKI, especially in the intensive care unit (ICU), are at risk of protein-energy malnutrition, which is a major negative prognostic factor in this clinical condition. Despite the lack of evidence from controlled trials of its effect on outcome, nutritional support by the enteral (preferentially) and/or parenteral route appears clinically indicated in most cases of ICU-acquired AKI, independently of the actual nutritional status of the patient, in order to prevent deterioration in the nutritional state with all its known complications. Extrapolating from data in other conditions, it seems intrinsically unlikely that starvation of a catabolic patient is more beneficial than appropriate nutritional support by an expert team with the skills to avoid the potential complications of the enteral and parenteral nutrition methodologies. By the same token, it is ethically impossible to conduct a trial in which the control group undergoes prolonged starvation. The primary goals of nutritional support in AKI, which represents a well-known inflammatory and pro-oxidative condition, are the same as those for other critically ill patients with normal renal function, i.e. to ensure the delivery of adequate nutrition, to prevent protein-energy wasting with its attendant metabolic complications, to promote wound healing and tissue repair, to support immune system function, to accelerate recovery and to reduce mortality. Patients with AKI on RRT should receive a basic intake of at least 1.5 g/kg/day of protein with an additional 0.2 g/kg/day to compensate for amino acid/protein loss during RRT, especially when daily treatments and/or high efficiecy modalities are used. Energy intake should consist of no more than 30 kcal non-protein calories or 1.3 × BEE (Basal Energy Expenditure) calculated by the Harris-Benedict equation, with ∼30-35% from lipid, as lipid emulsions. For nutritional support, the enteral route is preferred, although it often needs to be supplemented through the parenteral route in order to meet nutritional requirements.

Nutritional assessment and support in acute kidney injury

PURPOSE OF REVIEW

Acute kidney injury (AKI) in the ICU is associated with an increased risk of protein-energy wasting (PEW), a major negative prognostic factor. This review illustrates recently published data and guidelines concerning nutritional problems in AKI, pointing out complexities and peculiarities of the syndrome.

RECENT FINDINGS

The main goals of nutritional support in AKI on renal replacement therapy (RRT) are to ensure the provision of adequate amounts of nutrients, to prevent PEW, to promote tissue reparation, to support the immune system, and possibly to reduce mortality. The enteral route should be preferred, even though parenteral nutrition is often required to target nutritional needs. Special attention should be paid both to the impact of RRT on macronutrient and micronutrient losses, and to the risk of complications. In fact, due to both the acute loss of the kidneys' homeostatic function, and the frequent need of RRT, patients with AKI are especially prone to hypoglycemia and hyperglycemia, hypertriglyceridemia, fluid balance alterations, electrolyte and acid-base derangements.

SUMMARY

This review highlights the most recent concepts and recommendations for nutritional support in AKI, stressing the need for a close integration between adequate nutrition and RRT in this clinical condition, with the aim of carefully tailoring both therapies on patients' changing needs. Recent findings about the renoprotective role of some nutrients (glutamine, omega-3 fatty acids) are also discussed.

Parenteral nutrition in patients with renal failure - Guidelines on Parenteral Nutrition, Chapter 17

Partial EN (enteral nutrition) should always be aimed for in patients with renal failure that require nutritional support. Nevertheless PN (parenteral nutrition) may be necessary in renal failure in patient groups with acute or chronic renal failure (ARF or CRF) and additional acute diseases but without extracorporeal renal replacement therapy, or in patients with ARF or CRF with additional acute diseases on extracorporeal renal replacement therapy, haemodialysis therapy (HD), peritoneal dialysis (PD) or continuous renal replacement therapy (CRRT), or in patients on HD therapy with intradialytic PN. Patients with renal failure who show marked metabolic derangements and changes in nutritional requirements require the use of specifically adapted nutrient solutions. The substrate requirements of acutely ill, non-hypercatabolic patients with CRF correspond to those of patients with ARF who are not receiving any renal replacement patients therapy (utilisation of the administered nutrients has to be monitored carefully). In ARF patients and acutely ill CRF patients on renal replacement therapy, substrate requirements depend on disease severity, type and extent/frequency of extracorporeal renal replacement therapy, nutritional status, underlying disease and complications occurring during the course of the disease. Patients under HD have a higher risk of developing malnutrition. Intradialytic PN (IDPN) should be used if causes of malnutrition cannot be eliminated and other interventions fail. IDPN should only be carried out when modifiable causes of malnutrition are excluded and enhanced oral (like i.e. additional energy drinks) or enteral supply is unsuccessful or cannot be carried out.

Nutrition support therapy in acute kidney injury: distinguishing dogma from good practice

Acute kidney injury (AKI) is a frequently observed complication in critically ill patients. Its presentation may range from the early risk of renal dysfunction to complete renal failure. Morbidity and mortality in the AKI patient increase with the decline of renal function. Appropriate nutrition therapy is essential in the medical management of the AKI patient. Assessment of nutritional requirements should take into account the patient's underlying complication, comorbid medical conditions, and severity of the renal dysfunction. Various stages of AKI determine the direction of nutrition therapy. Additionally, understanding the macro- and micronutrient modifications and electrolyte and vitamin alterations that should be implemented are vital for better patient outcomes.

The protein equivalent of nitrogen appearance in critically ill acute renal failure patients undergoing continuous renal replacement therapy

OBJECTIVE

To assess the nutritional status of critically ill patients with acute renal failure on continuous renal replacement therapy (CRRT) and their protein needs by estimating the protein equivalent of nitrogen appearance (PNA).

DESIGN

Prospective, observational study.

SETTING

A 74-bed intensive care unit in a single tertiary care hospital.

PATIENTS

Twenty-five consecutive critically ill patients with acute renal failure on CRRT.

METHODS

The patients were studied over a period of 24 hours, at initiation on CRRT. The nutritional status was assessed by anthropometry and bioimpedance analysis. The PNA was estimated using the Bergstrom equation and PNA was normalized to body weight.

RESULTS

The mean age was 58.2 +/- 17 years and 20 (80%) were male. The mean weight was 67 +/- 12 kg, body mass index was 25 +/- 3.5 kg/m(2), and triceps and subscapular skin fold thickness were 13 +/- 4.6 mm and 15 +/- 2.5 mm, respectively. Bioimpedance studies showed that the total body water was increased at 61.7 +/- 5.5% and body fat was 31.8 +/- 5.4%. The PNA was 103 +/- 35 g/day and normalized PNA was 1.57 +/- 0.4 g/kg/day. The mean protein intake was 0.56 +/- 0.38 g/kg/day, resulting in mean net negative protein balance of 1.0 +/- 0.6 g/kg/day.

CONCLUSIONS

Malnutrition was uncommon in patients with acute renal failure at the time of initiation on CRRT, but their total body water was increased. They exhibited hypercatabolism and the mean normalized PNA was 1.57 g/kg/day. A large negative nitrogen balance was observed in them, since their protein intake was suboptimal.

Evaluation of high-protein supplementation in weight-stable HIV-positive subjects with a history of weight loss: a randomized, double-blind, multicenter trial

BACKGROUND

HIV patients with wasting are at increased risk of opportunistic complications and fatality.

OBJECTIVE

We hypothesized that augmenting dietary intake with high-biologic-value protein would enhance weight and lean tissue in weight-stable subjects with a prior unintentional weight loss of >3%.

DESIGN

Fifty-nine subjects with HIV RNA concentrations <5000 copies/mL were randomly assigned to receive a 280-kcal supplement containing 40 g whey protein or a matched isocaloric control supplement without added protein twice daily for 12 wk.

RESULTS

Before the study, intake of total energy and protein exceeded estimated requirements (44.3 +/- 12.6 kcal x kg(-1) x d(-1) and 1.69 +/- 0.55 g x kg(-1) x d(-1), respectively). Both supplements failed to increase total energy intake because of decreases in self-selected food intake. Changes in weight (0.8 +/- 2.4 and 0.7 +/- 2.4 kg) and lean body mass (0.3 +/- 1.4 and 0.3 +/- 1.5 kg) did not differ significantly between the whey protein and control groups, respectively. Waist-to-hip ratio improved more with whey protein (-0.02 +/- 0.05) than with the control (0.01 +/- 0.03; P = 0.025) at week 6 but not at week 12. Fasting triacylglycerol increased by 39 +/- 98 mg/dL with the control supplement and decreased by 16 +/- 62 mg/dL with whey protein at week 12 (P = 0.03). CD4 lymphocytes increased by 31 +/- 84 cells/mm(3) with whey protein and decreased by 5 +/- 124 cells/mm(3) with the control supplement at 12 wk (P = 0.03). Gastrointestinal symptoms occurred more often with whey protein.

CONCLUSIONS

A whey protein supplement did not increase weight or lean body mass in HIV-positive subjects who were eating adequately, but it did increase CD4 cell counts. The control supplement with rapidly assimilable carbohydrate substituted for protein increased cardiovascular disease risk factors. Careful dietary and weight history should be obtained before starting nutritional supplements in subjects with stable weight loss and good viral control.

Bench-to-bedside review: metabolism and nutrition

Acute kidney injury (AKI) develops mostly in the context of critical illness and multiple organ failure, characterized by alterations in substrate use, insulin resistance, and hypercatabolism. Optimal nutritional support of intensive care unit patients remains a matter of debate, mainly because of a lack of adequately designed clinical trials. Most guidelines are based on expert opinion rather than on solid evidence and are not fundamentally different for critically ill patients with or without AKI. In patients with a functional gastrointestinal tract, enteral nutrition is preferred over parenteral nutrition. The optimal timing of parenteral nutrition in those patients who cannot be fed enterally remains controversial. All nutritional regimens should include tight glycemic control. The recommended energy intake is 20 to 30 kcal/kg per day with a protein intake of 1.2 to 1.5 g/kg per day. Higher protein intakes have been suggested in patients with AKI on continuous renal replacement therapy (CRRT). However, the inadequate design of the trials does not allow firm conclusions. Nutritional support during CRRT should take into account the extracorporeal losses of glucose, amino acids, and micronutrients. Immunonutrients are the subject of intensive investigation but have not been evaluated specifically in patients with AKI. We suggest a protocolized nutritional strategy delivering enteral nutrition whenever possible and providing at least the daily requirements of trace elements and vitamins.

Intradialytic nutritional support

PURPOSE OF REVIEW

Intradialytic nutritional support has been used for more than 30 years both in critically ill patients with acute renal failure and during maintenance hemodialysis. Present knowledge allows better estimation of its metabolic and nutritional efficacy, as well its effect on patient outcome.

RECENT FINDINGS

Recent data showed that intradialytic nutritional support is able to counteract these effects of dialysis on protein metabolism and to improve both nitrogen and energy balance. In maintenance hemodialysis patients, the improvement of nutritional status during nutritional support was shown to improve long-term survival. In critically ill patients with acute renal failure, protein sparing is one of the main therapeutic goals. The effect of nutritional support on patient outcome is not demonstrated. Recent data, however, showed that the improvement of nitrogen balance may be associated with a better outcome.

SUMMARY

Current information helps to better assess the effects of intradialytic nutritional support, to clarify the nutritional management of renal failure patients and to provide recommendations. Future research should focus on the possible means to improve the efficacy of nutritional support, either by modifying its components of by associating anabolic or anticatabolic agents.

Continuous arteriovenous hemodialysis and continuous venovenous hemofiltration in burn patients with acute renal failure

Acute renal failure (ARF) is a very common condition that may occur in patients with major burn injuries. The majority of burn patients with ARF have a high mortality rate, ranging from 73% to 100%. There are several ways to treat ARF in burn patients, including peritoneal dialysis (PD), intermittent hemodialysis, and continuous renal replacement therapy (CRRT). CRRT is generally used in patients in whom intermittent hemodialysis has failed to control hypovolemia, as well as in patients who cannot tolerate intermittent hemodialysis. Additionally, PD is not suitable for patients with burns within the abdominal area. For these reasons, most patients with unstable hemodynamic conditions receive CRRT. In this study (conducted in our burn unit between 1997 and 2004), six burn patients received CRRT: three received continuous arteriovenous hemodialysis (CAVHD) and the other three received continuous venovenous hemofiltration (CVVH). The patients were all males, with a mean age of 49.8 years (range, 27-80 years), and a mean burnt surface area of 65.1% (range, 30-95%). Four patients died due to multiple organ failure, and two patients recovered from severe ARF. CRRT has been proven safe and useful for burn patients with ARF. According to this study, we conclude that CVVH is an appropriate tool for treating ARF, with a lower incidence of vascular complications than CAVHD.