Eight guidelines were included. Results are shown in Table 2. The Appraisal of Guidelines for Research and Evaluation II (AGREE II) instrument was used, which comprises six domains with 23 items. Each item is scored from 1 to 7, where 1 indicates “strongly disagree” (completely noncompliant) and 7 indicates “strongly agree” (completely compliant). Domain scores were standardized using the formula: (actual score – minimum possible score)/(maximum possible score – minimum possible score) × 100%. Recommendation levels were defined as follows: if all six domains score ≥60%, the recommendation is grade A; if more than three domains score ≥30% and at least one domain scores < 60%, the recommendation is grade B; if more than three domains score < 30%, the recommendation is grade C.

Two expert consensus documents met the quality standards and were included. The results are presented in Table 3.

One clinical decision aid was included (26), defaulting to high-level evidence.

In addition, we included one evidence summary (18), the evaluation results were as follows: item 3, “Transparency of reviewers or editors,” and item 5, “Transparency and translatability of the evidence grading system,” were rated “No”; item 7, “Appropriate citation of recommendations,” was rated “Not entirely”; all other items were rated “Yes.” This summary was therefore included.

After systematically extracting and integrating the relevant evidence, 16 evidence points were summarized across three domains: nutritional assessment and selection of nutritional pathways, energy and protein provision, and monitoring and supplementation of electrolytes and micronutrients (see Table 4).

Since CRRT does not alter the energy requirements of patients with AKI, current guidelines recommend an energy intake of 20–30 kcal/kg/day across all stages of AKI (27–29, 38). Indirect calorimetry is considered the gold standard for measuring resting energy expenditure (REE) in critically ill patients (39) and may be used to assess actual energy consumption when conditions permit. Multiple studies (40, 41) indicate that non-nutritive calories (NNCs) from propofol, glucose, and citrate in the CRRT circuit can contribute meaningfully to total energy intake. However, a retrospective study of 33 patients undergoing CVVHD (42) found that, in non-hyperglycemic patients, the metabolic contributions of lactate, glucose, and citrate were negligible, whereas in hyperglycemic patients these substrates were associated with substantial caloric loss (up to approximately 600 kcal/day). This finding may relate to the CRRT modality and patients' baseline hyperglycemia, which can increase glucose losses during therapy. Patients receiving CRRT are typically critically ill with multi-organ injury, and their energy requirements are closely linked to the underlying disease. Therefore, in clinical practice, energy provision should be individualized based on disease status, exogenous caloric intake and losses, and the CRRT modality.

Protein-energy wasting (PEW) is highly prevalent in patients with acute kidney injury (AKI) and is associated with prolonged hospitalization, increased complications, and higher mortality. Non-selective solute removal during CRRT may exacerbate PEW. During CRRT, various amino acids are removed (43); the degree of loss correlates with the patient's clinical condition and treatment modality, with CVVH demonstrating the greatest amino acid clearance (9, 10). Tatsumi's study (44) shows that in AKI patients without nutritional supplementation, blood amino acid concentrations remained stable during CVVH, yet substantial amounts of amino acids were detected in the effluent, potentially reflecting endogenous protein catabolism. Different studies (44, 45) estimate amino acid losses ranging from 5.7 to 13.4 g, which may relate to differences in membrane type, exogenous amino acid supplementation, and baseline serum amino acid concentrations. The ESPEN guidelines (27) recommend a protein intake of 1.5–1.7 g/kg/day for patients undergoing CRRT, whereas Hung et al. (34) recommend 1.5–2.5 g/kg/day. Research by van Ruijven et al. (46) found that early high-protein intake (≥1.2 g/kg/day) in patients receiving CRRT was significantly associated with lower hospital and ICU mortality. However, evidence linking higher protein intake to improved clinical outcomes remains limited.

Hypomagnesemia is quite common in AKI patients undergoing CRRT, with its incidence varying depending on the CRRT modality, treatment dosage, anticoagulation strategy, and composition of the replacement fluid/dialysate (47–49). The specific mechanisms of magnesium loss remain incompletely understood, potentially involving direct loss through filters and chelation with citrate in the extracorporeal circulation (50). However, this mechanism has not been confirmed in subsequent studies. Current guidelines recommend supplementing magnesium in the dialysate, but the optimal magnesium concentration for different CRRT protocols has yet to be established. Hypophosphatemia occurs in 54%−85% of critically ill patients undergoing CRRT (11); this may result in ventilator failure, difficulty weaning off the ventilator, and arrhythmias (11, 51). The occurrence of hypophosphatemia in CRRT patients may be associated with nonspecific clearance during the CRRT process. The use of phosphate-containing CRRT solutions is a safe and effective core strategy for preventing CRRT-induced hypophosphatemia. Combined with daily serum phosphorus monitoring, individualized phosphorus supplementation (oral or intravenous), and avoidance of electrolyte disturbances, this approach can significantly improve patient outcomes (52).

Regional citrate anticoagulation has become the preferred anticoagulation method for CRRT treatment in patients without contraindications due to its low bleeding risk (36, 53, 54). Because it relies on citrate to chelate calcium ions in the blood to inhibit activation of the coagulation system, it may cause disturbances in the patient's acid-base balance and fluctuations in blood calcium levels during treatment. Multiple studies (55, 56) have confirmed that ionized calcium levels in CRRT patients are closely associated with prognosis, with hypocalcemia increasing the risk of adverse outcomes. Current guidelines recommend monitoring electrolytes and acid-base status every 6–12 h initially for CRRT patients receiving citrate anticoagulation. If the patient remains stable within 24–48 h, electrolyte testing frequency may be reduced to every 12–24 h. Maintaining extracorporeal calcium ion concentration at 0.25–0.40 mmol/L achieves effective local anticoagulation, while maintaining intravascular calcium ion concentration within the normal physiological range of 1.1–1.3 mmol/L (36).

Micronutrients play a central role in numerous metabolic processes and cellular functions (38, 57). However, due to diffusion or adsorption, vitamins and trace elements may experience additional losses during CRRT treatment. The extent of these losses varies depending on the CRRT method, dosage, duration, and the specific type of micronutrient involved (38). Vitamin C, folic acid, selenium, copper, zinc, and carnitine can be detected in the effluent, with vitamin C and carnitine exhibiting the most significant losses (12, 58, 59). Liposoluble vitamins (A, D, E, K) and certain water-soluble vitamins (B1, B6, B12, potentially due to dilution, metabolic conversion, or adsorption) were not detected in the filtrate, yet their plasma concentrations showed a significant decrease, possibly related to adsorption by the membrane (9). The concentrations of trace elements such as selenium, zinc, and copper in the filtrate vary, potentially influenced by the patient's clinical condition, CRRT mode, and duration. A study involving 50 adult patients (60) demonstrated that vitamin B6, vitamin C, and folate levels significantly decreased 72 h after initiating CRRT, consistent with findings reported by Fah et al. (59). It is important to emphasize the monitoring and supplementation of micronutrients. Unfortunately, due to variations in nutritional delivery methods across studies, the relatively short duration of CRRT, and small sample sizes, it is not possible to provide dosage and regimen recommendations for nutritional supplementation in clinical practice (38, 61).

Summary: this study synthesizes the best available evidence on nutritional management during continuous renal replacement therapy (CRRT) in adults, providing an evidence-based foundation for clinical practice. Healthcare providers should develop personalized nutritional treatment plans tailored to each patient's disease status, CRRT modality, and treatment duration. As most included literature is in English, applying evidence should be contextualized to clinical settings. Future research should explore the effects of different CRRT modes, materials, and durations on caloric and nutrient requirements in AKI patients, thereby providing more reliable guidance for nutritional management in this population.