Evaluation of an Integrated Nutrition, Volume, and Electrolyte Nursing Protocol in Elderly Diabetic Nephropathy: A Retrospective Cohort Study

Summary

This retrospective historical-control study evaluated an integrated nutrition, volume, and electrolyte nursing protocol in 66 elderly patients with diabetic nephropathy. Compared with routine nursing, the protocol was associated with more favorable nutritional, volume, electrolyte, renal-function, adverse-event, quality-of-life, and economic indicators during hospitalization and three-month follow-up.

Abstract

To develop a “nutrition-volume-electrolyte” Trinity nursing protocol for elderly patients with diabetic nephropathy (DN), centered on precise nutritional protein regulation, and to evaluate its clinical and economic value. This single-center retrospective cohort study included 66 elderly patients with DN admitted between January 2022 and November 2025. Based on the implementation of the updated nursing protocol in January 2024, 31 patients who received routine nursing care were assigned to the historical control group, and 35 patients who received Trinity integrated nursing based on stratified nutritional protein management combined with volume and electrolyte regulation were assigned to the observation group. Interventions were delivered during hospitalization and continued for three months after discharge. Outcomes included nutritional indicators, volume load, electrolyte target attainment, renal function, adverse events, quality of life, and health economic measures. After three months, albumin, prealbumin, hemoglobin, and transferrin were significantly higher in the observation group than in the control group (all P < 0.01). At all assessed time points, the 24-h intake-output difference, B-type natriuretic peptide (BNP) level, and edema severity score were lower in the observation group (all P < 0.001). Target attainment rates for serum potassium, sodium, calcium, and phosphorus were higher (all P < 0.05), and changes in eGFR, serum creatinine, and 24-h urinary total protein were more favorable (all P < 0.05). Adverse events were less frequent in the observation group than in the control group (25.71% vs. 51.61%, P = 0.030). 36-Item Short Form Health Survey (SF-36) scores were higher, whereas hospital stay, total medical cost per capita, and cost per unit effect were lower (all P. < 0.001). In conclusion, the Trinity integrated nursing protocol improved nutritional status, volume, and electrolyte balance, renal outcomes, quality of life, and economic performance in elderly patients with DN, supporting its value in clinical nursing management.

Introduction

With the ongoing aging of the global population, diabetic nephropathy (DN) in older adults has become an increasingly important issue in the prevention and management of chronic disease in the elderly¹. Epidemiologic studies indicate that type 2 diabetes and chronic kidney disease frequently coexist in older adults, and diabetes remains a major contributor to kidney failure requiring dialysis or transplantation². In elderly patients, damage to the glomerular filtration barrier and persistent proteinuria lead to continuous loss of key nutritional proteins such as albumin. At the same time, age-related decline in organ function, multiple comorbidities, and polypharmacy further weaken the ability to maintain protein synthesis³. Once nutritional protein levels become abnormal, the consequences are not limited to malnutrition alone. Protein deficiency not only reflects poor nutritional status but also promotes hypoproteinemic edema and fluid retention⁴. It may also impair renal tubular ion transport and aggravate disturbances in potassium, calcium-phosphorus, and other electrolyte metabolism⁵. These abnormalities often interact with one another and may accelerate renal deterioration while increasing the risk of severe events such as acute heart failure and malignant arrhythmia⁶.

At present, nursing care for elderly patients with DN still focuses mainly on glycemic control and renal function monitoring^7,8. Alternative nursing approaches, including nutrition-focused care, rehabilitation nursing, home nursing, and structured follow-up, have been reported in patients with DN, but these strategies usually emphasize one dominant care domain⁹. For elderly non-dialysis DN patients with concurrent nutritional decline, edema, fluctuating fluid balance, or electrolyte abnormalities, an integrated pathway may be more practical because dietary guidance, volume monitoring, electrolyte review, and follow-up adjustment can be performed within the same nursing workflow¹⁰. By contrast, nutritional management, volume control, and electrolyte regulation are often handled separately, and nutritional protein management in particular is frequently inadequate¹¹. In some patients, protein intake is restricted too aggressively in an attempt to delay renal progression. In others, protein regulation lacks individualization altogether. Under these circumstances, the long-standing imbalance between protein loss and protein supplementation is difficult to correct. Previous studies have suggested that nutritional risk, fluid-related complications, and electrolyte disturbances are clinically relevant management concerns in patients with DN and chronic kidney disease (CKD); however, evidence regarding coordinated nursing pathways that address these problems together remains limited¹². Nevertheless, coordinated nursing strategies that address nutrition, volume status, and electrolyte balance as interrelated management targets remain insufficiently evaluated. Existing reports have mostly focused on single-domain nursing interventions, and the short-term clinical and economic associations of an integrated nursing-management pathway in elderly patients with diabetic nephropathy remain unclear. Reports on integrated nursing protocols centered on precise protein management remain limited, and their economic value has rarely been examined, which makes it difficult to provide solid support for nursing resource allocation in clinical practice.

Therefore, the present study evaluated whether a standardized integrated nutrition, volume, and electrolyte nursing protocol was associated with more favorable short-term clinical and economic indicators than routine nursing care in elderly patients with diabetic nephropathy. The study did not aim to prove a mechanistic pathway in which protein regulation directly drives volume or electrolyte improvement. Rather, it assessed whether a coordinated nursing-management strategy was associated with more favorable short-term clinical and economic indicators than routine nursing care. The study hypothesis was that, compared with historical routine nursing care, the integrated protocol would be associated with better nutritional status, more stable volume and electrolyte indicators, more favorable renal-function changes, fewer adverse events, improved quality of life, and lower medical costs during the three-month follow-up.

Protocol

This study was approved by the Ethics Committee of Zhejiang University School of Medicine. Because the study involved only anonymized retrospective data and no direct patient contact, informed consent was waived. The reagents and the equipment used are listed in the Table of Materials.

Study design and patient screening
This study used a single-center retrospective cohort design; elderly patients with DN who were treated in Zhejiang University School of Medicine between January 2022 and November 2025 were included. Candidate records were first identified through the hospital information system according to age, admission date, and discharge diagnosis. Eligibility was then checked against the predefined inclusion and exclusion criteria by two investigators, and records with incomplete hospitalization information, missing core laboratory indicators, or unavailable three-month follow-up data were excluded.

Inclusion and exclusion criteria
Inclusion criteria: age ≥60 years; either sex; diagnosis of type 2 diabetes and diabetic nephropathy based on standard clinical, laboratory, and kidney-disease management criteria¹³; complete hospitalization, treatment, and nursing records; complete follow-up data at three months after discharge; and traceable core laboratory results.

Exclusion criteria: end-stage renal disease, defined as chronic kidney disease (CKD) stage 5; regular hemodialysis or peritoneal dialysis; previous kidney transplantation; severe hepatic insufficiency (Child-Pugh grade B or above); malignant tumor; active autoimmune disease; severe hematologic disease; major cardio-cerebrovascular events within three months before enrollment, including acute myocardial infarction, cerebral infarction, and cerebral hemorrhage; severe systemic infection, septic shock, major trauma, or major surgery-related stress at admission; severe cognitive impairment or psychiatric disease affecting standardized nursing and follow-up; or a missing rate of core clinical data greater than 10%.

Group allocation
A total of 66 eligible patients were included. Because of the retrospective cohort design, no a priori sample-size calculation was performed. The final sample size represented all consecutive eligible patients treated during the predefined study period after application of the inclusion and exclusion criteria and confirmation of complete hospitalization records and three-month follow-up data. Our hospital formally implemented the integrated nursing protocol investigated in this study in January 2024, and this time point was used for grouping. The 31 patients admitted from January 2022 to December 2023 received routine nursing during hospitalization and were assigned to the control group. The 35 patients admitted from January 2024 to November 2025 received the integrated nursing intervention and were assigned to the observation group. Because the two groups were admitted during different periods, crossover of nursing interventions was unlikely. However, this before-and-after grouping strategy introduced potential temporal bias, as changes in hospital practice, medication availability, diabetes management, discharge planning, staffing, follow-up procedures, and cost structures between 2022 and 2025 may have influenced the observed outcomes.

Conventional nursing protocol
Routine nursing was based mainly on standard disease management. It included daily monitoring of fasting and 2-h postprandial blood glucose, blood pressure, heart rate, oxygen saturation, and other vital signs; medication-related nursing according to medical orders for hypoglycemic drugs, renin-angiotensin-aldosterone system (RAAS) inhibitors, lipid-lowering agents, and renoprotective treatment, together with monitoring for adverse drug reactions; unified dietary education on a low-protein diet, with protein intake set at 0.8 g/kg ideal body weight per day and high-quality animal protein accounting for at least 50%, along with salt and fluid restriction; daily recording of 24-h intake and output; weekly assessment of renal function and serum electrolytes; observation of edema and urine output; and reporting of abnormalities in a timely manner. After discharge, patients received verbal health education and one telephone follow-up per month to assess home medication use, dietary control, and compliance with scheduled follow-up. Each telephone follow-up was recorded in the nursing follow-up log and included medication adherence, diet implementation, edema symptoms, urine-output changes, hypoglycemic symptoms, and outpatient review status.

Trinity integrated nursing protocol
The integrated nursing protocol used in the observation group was designed to replace the fragmented approach of routine care. The workflow included five sequential steps: baseline assessment within 24 h after admission, individualized nutrition-volume-electrolyte planning, daily inpatient monitoring and adjustment, discharge education, and three-month post-discharge follow-up. At baseline, nurses recorded body mass index, CKD stage, appetite, dietary intake, edema grade, 24-h intake-output balance, urine output, medication use, and core laboratory indicators. During hospitalization, diet records, fluid intake, output, edema, blood pressure, urine output, and electrolyte results were reviewed according to the nursing checklist. Abnormal findings, including persistent positive fluid balance, worsening edema, reduced urine output, poor dietary intake, hypoalbuminemia, or electrolyte abnormality, were reported to the treating physician or clinical nutrition service for adjustment. Before discharge, patients and caregivers received written instructions on protein intake, low-phosphorus food choices, salt and fluid restriction, body-weight monitoring, warning symptoms, medication adherence, and follow-up appointments, and follow-up records were maintained for three months after discharge. It was a multicomponent nursing package that combined individualized nutritional guidance, volume management, electrolyte monitoring, follow-up education, and home-care support. The nutritional component was carried out by ward nurses under nephrologist-approved dietary prescriptions, with consultation from the clinical nutrition service when patients had poor intake, evident malnutrition risk, marked hypoalbuminemia, uncontrolled edema, or recurrent electrolyte disturbance. At admission, nurses assessed body mass index, chronic kidney disease stage, appetite, usual diet, serum albumin, prealbumin, hemoglobin, transferrin, urinary protein, edema grade, 24-h intake-output balance, and serum electrolyte levels. Daily nursing tasks included diet-record review, reinforcement of protein-energy targets, education on high-quality low-phosphorus protein choices, fluid and sodium guidance, monitoring of edema and urine output, and timely reporting of abnormal nutritional or electrolyte results for medical or nutritional adjustment. A schematic overview of the protocol is shown in Figure 1. The intervention was initiated within 24 h after admission, continued throughout hospitalization, and was maintained for three months after discharge. Protocol adherence was checked using admission assessment forms, daily nursing checklists, discharge education forms, and follow-up logs. The three-month endpoint was selected because nutritional correction, volume stabilization, electrolyte adjustment, renal-function monitoring, adverse events, quality of life, and medical costs require repeated assessment after discharge. This timeframe is also consistent with recent nutritional and chronic kidney disease management literature, in which approximately twelve weeks or three months is commonly used to evaluate short-term clinical and nutritional responses.

Outcome assessment
Assessments were performed before intervention (at admission) and again three months after intervention. The primary outcomes were nutritional protein-related indicators at three months, including serum albumin, prealbumin, hemoglobin, and transferrin. Secondary outcomes included volume load-related indicators, electrolyte target attainment, renal function-related indicators, adverse events, all-cause readmission, quality-of-life scores, and health economic indicators. Three milliliters of fasting venous blood were collected from the cubital vein in the morning, and serum was separated by centrifugation at 1505 × g. for 10 min at room temperature before analysis. Measured indicators included serum albumin (ALB), prealbumin (PA), hemoglobin (HGB), and transferrin (TRF). Volume load-related indicators included 24-h fluid intake-output difference, BNP level, and edema severity score. The 24-h intake-output difference was calculated as total recorded fluid intake minus total recorded output within the same 24-h period. Edema severity was scored as 0 for no edema, 1 for mild ankle or pedal edema, 2 for edema extending to the lower leg, and 3 for generalized edema or obvious sacral edema. Electrolyte-related indicators were defined as the rates of achieving target values for serum potassium, sodium, calcium, phosphorus, and bicarbonate during the three-month intervention period, according to the reference ranges used by the hospital laboratory. Renal function-related indicators, estimated glomerular filtration rate (eGFR), serum creatinine (Scr), and 24-h urinary total protein (24-h UTP), were measured before intervention and at the follow-up endpoint.

Safety assessment
Clinical adverse events occurring within three months after intervention were recorded when documented in the medical record by the treating physician, including acute left heart failure, hyperkalemia, acute kidney injury, pulmonary infection, and severe hypoglycemia. The all-cause readmission rate was also documented¹⁴.

Quality-of-life assessment
Quality of life was assessed before intervention and again at the follow-up endpoint using the 36-Item Short Form Health Survey (SF-36)¹⁵. The scale includes eight dimensions: physical functioning, role physical, bodily pain, general health, vitality, social functioning, role emotional, and mental health. Each dimension is scored on a 0–100 scale, with higher scores indicating better quality of life.

Health economic evaluation
Relevant data were obtained from the hospital information system (HIS) and follow-up records, including hospital stay during the index admission, total hospitalization cost, and outpatient cost during the three-month follow-up period. Based on these data, the per-capita total medical cost was calculated for each group (per capita total medical cost was calculated as the sum of hospitalization cost and outpatient cost during the three-month follow-up period for each patient). The cost-effectiveness ratio (CER) was then calculated using the change in ALB before and after intervention as the effect indicator.

Statistical analysis
All data were analyzed using SPSS 26.0. Quantitative data with a normal distribution are expressed as mean ± standard deviation (χ ± s); between-group comparisons were performed using the independent-samples t-test, and within-group comparisons before and after intervention were performed using the paired t-test. Quantitative data without a normal distribution are expressed as median (interquartile range) [M (P25, P75)] and were compared using the Mann-Whitney U test. Categorical data are expressed as the number of cases (percentage) [n (%)] and were compared using the χ² test or Fisher’s exact test where appropriate. All tests were two-sided, with α = 0.05 regarded as statistically significant.

Results

Comparison of baseline characteristics
Baseline demographic characteristics, disease status, complications, and laboratory indicators at admission were compared between the two groups. No statistically significant differences were found in baseline variables (P. > 0.05, Table 1).

Changes in nutritional protein-related indicators before and after intervention
After three months, ALB, PA, HGB, and TRF were all higher in the o...

Discussion

In routine nursing practice, nutrition, volume status, and electrolyte balance in elderly patients with DN are often managed as separate issues rather than as closely related components of the same clinical problem. In the present study, the Trinity nursing protocol was associated with more favorable outcomes than routine care across several dimensions. Patients in the observation group showed better nutritional indices, more stable volume and electrolyte status, slower deterioration in renal function, fewer adverse even...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Centrifuge	Hunan Xiangyi Laboratory Instrument Development Co., Ltd.	TGL-16G	Routine high-speed centrifuge for laboratory use, used for centrifuging collected venous blood at 3000 r/min for 10 minutes to separate serum from blood components, providing serum samples for subsequent blood index testing.
24-hour Urinary Total Protein (24-h UTP) Detection Reagent	Shanghai Kehua Bio-Engineering Co., Ltd.	KHB Series Matching Biochemical Reagent	Used for detecting total protein content in 24-hour urine, directly reflecting the degree of proteinuria in patients, and serving as an important indicator for evaluating renal injury and renal function changes in patients with diabetic nephropathy.
Bicarbonate Detection Reagent	Mindray Biomedical Electronics Co., Ltd.	BS-800 Series Matching Biochemical Reagent	Used for detecting bicarbonate content in serum, serving as an auxiliary indicator for acid-base balance and electrolytes, and participating in the evaluation of patients' electrolyte and internal environment balance.
B-type Natriuretic Peptide (BNP) Detection Reagent	Abbott Diagnostics Products (Shanghai) Co., Ltd.	i2000 Series Matching Chemiluminescence Reagent	Used for detecting BNP concentration in serum, serving as a key indicator for evaluating the volume load of research subjects and assisting in judging volume abnormalities related to edema and cardiac function.
Disposable Blood Collection Needle	Becton, Dickinson and Company (BD) Medical Devices (Shanghai) Co., Ltd.	21G	Used in conjunction with vacuum blood collection tubes for venipuncture of the cubital vein to collect venous blood. The needle size is suitable for venous blood collection operations, and single-use ensures sterility.
Hemoglobin (HGB) Detection Reagent	Sysmex Medical Electronics (Shanghai) Co., Ltd.	XN Series Matching Hematology Reagent	Used for detecting hemoglobin content in blood, comprehensively evaluating the nutritional status of research subjects in combination with indicators such as albumin and prealbumin, and serving as an important reagent for anemia and nutritional assessment.
Prealbumin (PA) Detection Reagent	Roche Diagnostics Products (Shanghai) Co., Ltd.	cobas c Series Matching Biochemical Reagent	Used in conjunction with albumin detection reagents to detect prealbumin levels in serum, assisting in evaluating the short-term nutritional status of patients and providing monitoring indicators for the effectiveness of nutritional interventions.
Serum Albumin (ALB) Detection Reagent	Roche Diagnostics Products (Shanghai) Co., Ltd.	cobas c Series Matching Biochemical Reagent	Used for detecting albumin content in serum, serving as a core reagent for evaluating the nutritional protein status of research subjects. Suitable for fully automatic biochemical analyzers, the test results provide data for evaluating the nutritional status of elderly patients with diabetic nephropathy.
Serum Creatinine (Scr) Detection Reagent	Roche Diagnostics Products (Shanghai) Co., Ltd.	cobas c Series Matching Biochemical Reagent	Detects creatinine concentration in serum, serving as one of the core indicators for evaluating renal function. Combined with eGFR and 24h urinary total protein, it judges the degree of renal injury and intervention effect in patients.
Serum Electrolyte Detection Reagent (Potassium, Sodium, Calcium, Phosphorus)	Mindray Biomedical Electronics Co., Ltd.	BS-800 Series Matching Biochemical Reagent	Contains dedicated reagents for detecting potassium, sodium, calcium, and phosphorus ions, used for detecting the concentration of corresponding electrolytes in serum, calculating the electrolyte target compliance rate, and evaluating electrolyte balance status.
SPSS Statistical Software	IBM Corporation	SPSS 26.0	Used for statistical analysis of all clinical and experimental data in this study, capable of completing various statistical methods such as independent sample t-test, paired t-test, chi-square test, and Mann-Whitney U test, with α=0.05 set as the statistical significance criterion.
Transferrin (TRF) Detection Reagent	Roche Diagnostics Products (Shanghai) Co., Ltd.	cobas c Series Matching Biochemical Reagent	Detects transferrin levels in serum, serving as one of the nutritional protein-related indicators to participate in the comprehensive evaluation of patients' nutritional status, reflecting the body's iron metabolism and nutritional reserves.
Vacuum Coagulation-promoting Blood Collection Tube	Becton, Dickinson and Company (BD) Medical Devices (Shanghai) Co., Ltd.	3ml Routine Coagulation-promoting Type	Used for collecting fasting venous blood from the cubital vein of research subjects, with a single tube blood collection volume of 3ml. Coagulants accelerate blood coagulation to facilitate subsequent serum separation, serving as a dedicated device for blood sample collection.