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 observation group than in the control group (P < 0.01). Within-group analysis showed significant increases in all four indicators in the observation group after intervention (P < 0.01). In the control group, PA and TRF increased slightly compared with baseline (P < 0.01), whereas ALB and HGB did not show significant change (P. > 0.01, Figure 2).

Changes in volume load-related indicators
At admission, there were no significant differences between the two groups in the 24-h intake-output difference, BNP level, or edema severity score (P > 0.05). During follow-up, all three indicators declined in both groups, and values at each assessment point were lower in the observation group than in the control group (P. < 0.01, Figure 3).

Electrolyte target attainment
During the three-month intervention period, bicarbonate target attainment did not differ significantly between the two groups (P = 0.053). However, the observation group had higher attainment rates for serum potassium, sodium, calcium, and phosphorus than the control group (P. < 0.05). In the observation group, the attainment rate for each of these indicators exceeded 80%, whereas the highest rate in the control group was 74.19% (Table 2).

Changes in renal function-related indicators
At admission, eGFR, Scr, and 24-h UTP were comparable between the two groups (P > 0.05). After three months, all three renal function-related indicators showed more favorable changes in the observation group (P < 0.01). In the control group, Scr and 24-h UTP decreased compared with baseline (P < 0.01), but eGFR did not change significantly (P > 0.05). After intervention, eGFR was higher, and Scr and 24-h UTP were lower in the observation group than in the control group (P. < 0.01, Figure 4).

Clinical adverse events and readmission
During the three-month follow-up period, the total incidence of clinical adverse events was 25.71% in the observation group and 51.61% in the control group (P. = 0.030). The all-cause readmission rate was 8.57% in the observation group and 16.13% in the control group (Table 3).

Changes in quality-of-life scores
After three months of intervention, scores in all eight dimensions of the SF-36 were higher in the observation group than in the control group (P < 0.01). Within-group comparisons showed significant improvement in all eight dimensions in both groups after intervention (P. < 0.01, Figure 5).

Analysis of health economic benefits
Mean hospital stay in the observation group was (10.37 ± 3.10) d, shorter than (14.06 ± 2.86) d in the control group (P < 0.01). Total hospitalization cost, outpatient cost during the three-month follow-up, and per-capita total medical cost were all lower in the observation group (P < 0.01). Using the increase in ALB at three months as the effect indicator, the CER was calculated as 5839.09 RMB per 1 g/L increase in ALB in the observation group, compared with 7088.29 RMB in the control group (P. < 0.01), suggesting more favorable short-term economic indicators in the observation group (Table 4).

DATA AVAILABILITY:
Data supporting the findings of this study are provided in Supplementary File 1.

Figure 1: Trinity integrated nursing protocol for elderly patients with DN. Please click here to view a larger version of this figure.

Figure 2: Changes in nutritional protein-related indicators before and after follow-up. (A) Serum albumin (ALB). (B) Prealbumin (PA). (C) Hemoglobin (HGB). (D) Transferrin (TRF). Compared with that at admission, ^**P < 0.01, and compared with the observation group ^##P. < 0.01. Please click here to view a larger version of this figure.

Figure 3: Changes in volume load-related indicators during follow-up. (A) 24-h intake-output difference. (B) B-type natriuretic peptide (BNP). (C) Edema severity score. Compared with that at admission, ^**P < 0.01, and compared with the observation group ^##P. < 0.01. Please click here to view a larger version of this figure.

Figure 4: Changes in renal function-related indicators before and after follow-up. (A) Estimated glomerular filtration rate (eGFR). (B) Serum creatinine (Scr). (C) 24-h urinary total protein (24-h UTP). Compared with that at admission, ^**P < 0.01, and compared with the observation group ^##P. < 0.01. Please click here to view a larger version of this figure.

Figure 5: Changes in SF-36 quality-of-life scores after follow-up. (A) Physical functioning. (B) Role physical. (C) Bodily pain. (D) General health. (E) Vitality. (F) Social functioning. (G) Role emotional. (H) Mental health. Compared with that at admission, ^**P < 0.01, and compared with the observation group ^##P. < 0.01. Please click here to view a larger version of this figure.

Indicator	Observation group (n=35)	Control group (n=31)	t or c2	P
Age (years)	73.71±6.18	72.45±7.19	0.767	0.446
Sex (male/female)	19/16	16/15	0.047	0.828
Body mass index (kg/m²)	23.04±3.53	22.27±2.67	0.98	0.331
Duration of type 2 diabetes (years)	10.74±4.43	11.16±4.15	0.394	0.695
Duration of DN (years)	4.54±1.67	4.06±1.61	1.181	0.242
Mogensen stage (III/IV)	20/15	#######	0.374	0.541
CKD stage (2/3/4)	9/18/8	7/15/9	0.34	0.844
Complications
Hypertension	27 (77.14)	22 (70.97)	0.328	0.567
Coronary heart disease	10 (28.57)	13 (41.97)	1.293	0.256
Hyperlipidemia	20 (57.14)	20 (64.52)	0.374	0.541

Table 1: Baseline demographic and clinical characteristics of the two groups.

Indicator	Observation group (n=35)	Control group (n=31)	c2	P
Serum potassium	30 (85.71)	20 (64.52)	4.022	0.045
Serum sodium	33 (94.29)	23 (74.19)	Fisher's exact	0.037
Serum calcium	31 (88.57)	20 (64.52)	Fisher's exact	0.037
Serum phosphorus	28 (80.00)	17 (54.84)	4.797	0.029
Bicarbonate	32 (91.43)	22 (70.97)	Fisher's exact	0.053

Table 2: Comparison of electrolyte target attainment rates between the two groups during the three-month intervention period.

Adverse event type	Observation group (n=35)	Control group (n=31)	c2	P
Acute left heart failure	1 (2.86)	2 (6.45)
Hyperkalemia	2 (5.71)	3 (9.68)
Acute kidney injury	1 (2.86)	2 (6.45)
Pulmonary infection	2 (5.71)	3 (9.68)
Severe hypoglycemia	0 (0.0)	1 (3.23)
All-cause readmission	3 (8.57)	5 (16.13)
Total	9 (25.71)	16 (51.61)	4.686	0.03

Table 3: Comparison of clinical adverse events and all-cause readmission between the two groups.

Indicator	Observation group (n=35)	Control group (n=31)	t	95%CI	P
Length of hospital stay (days)	10.37±3.10	14.06±2.86	5.009	2.220 to 5.166	<0.001
Total cost per hospitalization (RMB)	16054.54±2467.01	22523.71±3763.58	8.348	4921 to 8017	<0.001
Total outpatient cost during three months follow-up (RMB)	2229.03±527.33	3408.16±813.17	7.067	845.8 to 1512	<0.001
Per-capita total medical cost (RMB)	18283.57±2557.41	25931.87±3841.05	9.62	6060 to 9237	<0.001
CER (RMB / per 1 g/L increase in ALB)	5839.09±235.22	7088.29±278.90	19.742	1123 to 1376	<0.001

Table 4: Comparison of health economic indicators between the two groups.

Supplementary File 1: Data supporting the findings of this study.Please click here to download this file.

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 events, and better quality-of-life scores. Economic indicators also favored the integrated protocol, with shorter hospital stays and lower overall medical expenditure. These findings suggest that a coordinated nursing approach may be more suitable for elderly patients with DN than conventional fragmented management¹⁶. Because the intervention was delivered as a multicomponent nursing package, these findings should be interpreted as associations with the overall integrated pathway rather than causal effects of any single component.

One important feature of the present protocol was the use of a stratified protein intake plan based on renal function stage and the severity of urinary protein loss. This may partly explain, together with structured follow-up and coordinated volume and electrolyte management, the more favorable nutritional markers observed in the observation group. In routine nursing, a single protein standard is often applied to most patients, regardless of differences in CKD stage or protein loss burden. In practice, this may result either in excessive restriction and worsening malnutrition or in protein supplementation that does not match the patient’s renal condition^9,17. By contrast, the present protocol adjusted total protein intake more carefully, maintained an appropriate proportion of high-quality low-phosphorus protein, and emphasized adequate energy intake to reduce the likelihood of endogenous protein breakdown due to insufficient calories. In other words, the intervention did not focus only on how much protein patients ate, but also on whether intake matched protein loss and metabolic demand. Similar observations have been reported in previous studies of nutritional nursing in elderly patients with DN^12,18, which also showed that individualized nutritional intervention was more effective than uniform dietary advice in improving nutritional status and reducing the risk of malnutrition.

A similar advantage was seen in the management of volume status and electrolyte balance. This may be related to the fact that the present protocol did not treat these domains independently. In elderly patients with DN, volume overload commonly coexists with hypoproteinemia. Under routine care, edema is often addressed mainly with diuretics¹⁹. Although this approach may relieve symptoms for a time, it can also aggravate urinary protein loss, further lower plasma colloid osmotic pressure, and make recurrent fluid retention more likely. At the same time, potassium, sodium, and other electrolyte disturbances may become harder to control²⁰. In the observation group, nutritional correction was placed before more detailed volume regulation. Improved ALB may have supported plasma colloid osmotic pressure and contributed to more stable volume control, but this remains an interpretation because colloid osmotic pressure was not directly measured. The more favorable volume-related indicators may reflect the combined effects of dietary guidance, fluid and sodium education, intake-output monitoring, edema assessment, medication-related nursing, and follow-up adjustment, rather than nutritional correction alone. Electrolyte monitoring was also linked to ongoing changes in diet and medication, and the testing schedule was adjusted according to actual intake and treatment. Such management was more anticipatory than reactive, which may partly account for the higher electrolyte target attainment rates seen in the observation group. This finding is generally consistent with previous reports suggesting that integrated volume management is more effective in maintaining homeostasis in patients with DN²¹.

The observation group also showed better post-intervention renal function, fewer clinical adverse events, and higher quality-of-life scores. These improvements were probably not due to any single measure, but to the combined effect of coordinated intervention. In elderly patients with DN, hyperglycemia and hypertension remain important risk factors, but malnutrition, recurrent volume overload, and electrolyte disturbance also play an important role in rapid renal deterioration and acute clinical exacerbation²². Routine nursing often places greater emphasis on blood glucose and blood pressure control, whereas these additional factors may not be managed systematically enough. By addressing nutrition, volume status, and electrolyte balance together, the present protocol may have reduced several modifiable contributors to acute deterioration while also helping to slow ongoing renal decline. This pattern was reflected not only in laboratory findings but also in the lower incidence of adverse events and the more favorable quality-of-life profile after intervention. In addition, shorter hospital stay and lower readmission in the observation group reduced total medical expenditure. The cost-effectiveness analysis led to the same general conclusion, namely that the integrated nursing protocol improved outcomes while lowering the medical burden on patients, which is consistent with domestic health economic studies of integrated chronic disease nursing²³.

These findings have practical implications for healthcare delivery in elderly patients with diabetic nephropathy. A structured nutrition-volume-electrolyte pathway may help reduce fragmented instructions, improve continuity from hospitalization to home care, and enable nurses to identify nutritional decline, fluid overload, and electrolyte disturbance earlier. Because the protocol mainly depends on routine laboratory tests, intake-output records, dietary review, structured education, and scheduled follow-up, it may be incorporated into existing chronic disease nursing workflows without major additional equipment. The observed reductions in hospital stay, adverse events, readmission, and per-capita medical cost also suggest potential value for resource allocation in geriatric kidney care, although this should be confirmed in prospective multicenter studies. However, several limitations should be noted. First, this was a single-center retrospective cohort study with a relatively small sample size of 66 cases, and the use of a historical control design means that selection bias and temporal bias cannot be fully ruled out. Because the historical control and observation groups were treated during different calendar periods, changes in hospital practice, medication availability, diabetes management, discharge planning, staffing, follow-up procedures, and cost structures between 2022 and 2025 may have contributed to between-group differences. Second, because the study was retrospective, the completeness of nursing records and the consistency of follow-up data may not have been entirely uniform, and residual confounding is still possible. Third, the intervention and follow-up period lasted only three months, so the present findings mainly reflect short-term effects. Whether this protocol can influence long-term renal progression and survival remains unclear. In addition, subgroup analyses based on CKD stage or baseline nutritional status were not performed, so the applicability of the protocol in specific patient subsets remains to be clarified. Although nursing checklists and follow-up logs were used during implementation, detailed process indicators such as checklist completion rate, dietary-record completeness, and follow-up contact completion were not analyzed as independent outcomes. Moreover, the intervention was delivered as a multicomponent package, and the independent contribution of each component could not be isolated. Therefore, the observed associations should not be attributed solely to nutritional protein regulation. Further multicenter prospective randomized studies with larger sample sizes and longer follow-up will be needed.

Conclusion
The “nutrition-volume-electrolyte” Trinity integrated nursing protocol was associated with more favorable nutritional status, volume, and electrolyte indicators, renal-function changes, adverse-event profile, quality of life, and short-term economic indicators in elderly patients with DN. These findings suggest that the protocol may have practical value as a structured nursing-management pathway for clinically stable elderly patients with non-dialysis DN.

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.