The study is a multi-center, interventional, prospective, pragmatic, unblinded, and parallel controlled trial This protocol is designed in accordance with Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) guidelines(19). All the data will be collected at each time spot as shown in the Standard Protocol Items [Fig.1]. The study flow is described in Figure 2.
Study sites and period
The study is planned to be conducted from March 1st 2019 to February 28th 2022 in 2 centers including the ICU of Zhongnan Hospital of Wuhan University and the ICU of Wuhan Central Hospital of Tongji Medical College, Huazhong University of Science and Technology. The above 2 hospitals are both tertiary hospitals integrating clinical, scientific research and teaching. Participating ICUs began enrolment sequentially over the first year of the study. Each ICU will enroll participants for an equal number of acetate Ringer’s solution and saline months for at least 12 months.
Registration, ethical considerations, and monitoring
The study was registered on ClinicalTrials.gov before the participants' enrolment started (identifiers: NCT03685214) (Table 1). This study follows the principles of the Helsinki Declaration 2013. The whole protocol has been reviewed and approved by the Ethics Committee of Zhongnan Hospital of Wuhan University (Clinical Ethical Approval No. 2018010) and the Ethics Committee of Wuhan Central Hospital of Tongji Medical College, Huazhong University of Science and Technology (Hospital Ethical Approval No. 201904). An independent data and safety monitoring board (DSMB) is monitoring the progress and safety of the trial. The DSMB is independent of the trial and is comprised of two academic intensivists, professor Jianguo Li and professor Bo Hu, outside the study who are experienced in the conduct of clinical trials in critical illness, being able to pause the trial to investigate or give suggestions on potential safety issues to improve our design and implement. The DSMB follows the charter of the Ethics Committee of Zhongnan Hospital of Wuhan University.
Participants' inclusion criteria are as follows:
- At the age of 18 to 80;
- Diagnosed as sepsis (a possible or specific proof for infection plus Sequential Organs Failure Assessment (SOFA) scores≥2)(22).
Participants' exclusion criteria are as follows:
- Patients once having received RRT;
- Patients requiring RRT prior to enrolment;
- Patients possessed with only one kidney;
- Patients with a medical history of renal transplant；
- AKI caused by permanent kidney artery embolism or surgery injury to kidney artery;
- AKI caused by glomerulonephritis, interstitial nephritis or vasculitis;
- AKI caused by postrenal obstruction;
- Hemolytic uremic syndrome (HUS) or thrombotic thrombocytopenic purpura;
- Patients having received fluid resuscitation over 1000ml within 6 hours prior to ICU;
- Patients with serum chloride more than 120mmol/L;
- Pregnant women;
- Patients enrolled into another clinical trial at the same
The intervention of treatment lies in fluid management. To exclude the possible difference caused by different balanced crystalloid solution, acetate Ringer’s solution is chosen for balanced crystalloids infusion. After patient screening and grouping, participants will be assigned with acetate Ringer’s solution or saline for intravenous infusion accordingly. The volume, infusion rate and additive content (e.g., potassium chloride) of the fluid will be determined by responsible clinicians. The intervention will last for 5 days after patients’ enrolment. Other solutions are permitted to be used as carrier fluids for the infusion of any drug on the occasion when neither acetate Ringer’s solution nor saline is considered compatible. Medication use except fluids will not be restricted in the study.
Parallel control and allocation
Patients will be divided into 2 parallel groups: acetate Ringer’s solution versus saline. Crystalloids for enrolled patients is assigned according to the number of the month. Once assigned, the solution will be applied for the first 5 days during the patients’ stay in ICU. The assignment remains during change of month. The solution applied in the beginning month in each ICU is determined randomly by Excel2016 of Microsoft Office to make sure that stratified patient groups will be randomized to receive either acetate ringers or saline solution, followed by a monthly rotation of fluids, so that any potentially observed difference in renal function is not due to other confounding factors such as use of nephrotoxic medication or contrast media. According to the Excel2016-generated random numbers, Acetate Ringer’s solution will be applied in the odd month and saline will be applied in the even month both in the 2 centers. The random number table is operated by the primary investigator alone and clinicians are not involved in the process.
Study fluid distribution and logistics
The acetate Ringer’s solution is manufactured by Heng Rui Pharmaceutical Company Limited of Jiangsu Province with trade name of Le Jia, which has volume sizes of 250ml and 500ml, while the saline is produced by Baxter Healthcare with different volume sizes of 250ml, and 500ml. Components of these two crystalloids are presented below [Fig.3]. The study is an open-label study, thus the exact solution used is known to investigators, clinicians and patients. Since the study is non-blind and two fluids used in this study have already been widely applied in the daily care of patients in the above ICUs, there are not problems of logistics.
The primary outcome is MAKE28 (major adverse kidney events)(23)-a composite of in-hospital death, new renal-replacement therapy or persistent renal dysfunction (defined by an estimate glomerular filtration rate (eGFR) lower than 60 ml/min/1.73 m2 for at least 3 months(24, 25)) within 28 observational days.
Secondary outcomes will include:
- 28 days-mortality;
- Electrolytes disturbance, including hypernatremia, hyperchloremia and hyperkalemia as well as hyponatremia, hypochloremia and hypokalemia;
- Changes of renal functions based on the biomarkers measured from the participants' plasma and urine samples collected in the first three days after
- Other clinical outcomes: ICU-stay days, ventilator days, vasopressor days, and RRT
Pre-specified subgroups for primary and secondary outcome analyses will include:
- With or without kidney injury (defined as baseline creatinine concentration at least 1.5 times above the upper limit of normal for the local laboratory);
- With or without septic shock;
- Low versus high severity of sepsis: mild, moderate and severe (defined by SOFA scores and Acute Physiology and Chronic Health Evaluation II (APACHE II) scores)
- Intravenous infused volumes of the assigned
Sample size and statistical power
The sample size was calculated based on the occurrence of MAKE30 on septic patients, which was around 35%(17). With a noninferiority limit of 1.5%, a total of 312 study participants (156 in each group) would result in a power of at least 80% with a one-sided type-1 error rate (α) of 2.5%, allowing a 20% withdrawal rate in each group.
Measurement data that conform to normal distribution will be described as mean ± SD, while ones that do not will be reported as the median and inter quartile range (IQR). Count data will be notified as frequencies and proportions. As for single factor analysis, the difference of measurement data will be compared with T-test between two groups or with one-way analysis of variance among three groups. Chi-square test and Fisher's exact test will be used for rate comparison. As for multi-factor analysis, variables which showed a significant difference in the univariate analysis will be processed by logistic multivariate regression analysis. Multiple linear regression analysis will be used to demonstrate the linear relationship between variables. P value <0.05 will be considered statistically significant. SPSS 22.0 will be used to complete data processing and statistical analysis.
This study will recruit a meaningful sample sized participants with a wide range of baseline risk factors of the primary outcome who are exposed to the study intervention and can be divided into subgroups of distinct renal function. The baseline and secondary analysis will figure out whether the intervention makes a difference to patients' prognosis.
The primary analysis will be an intention-to-treat comparison of the primary outcome of MAKE28 between the saline and acetate Ringer's solution. A generalized linear mixed-effects model will be used including fixed effects (sex, age, race, group assignment, principal diagnosis, mechanical ventilation days, vasopressor days, ICU stay days) and random effects. It is aimed to describe patients’ baseline characteristics and eliminate confounding factors.
Main secondary analysis
We presume that participants will receive a wide range of total crystalloid volumes and that the more fluid patients receive, the more significant difference will be performed between the two groups. Also, we presume that the outcome may be related with participants’ initial renal function. Based on these anticipations, in the main secondary analysis, patients will be divided into several groups according to different crystalloid infusion volumes and distinct initial renal function respectively. The proportion of patients experiencing the primary outcome will be compared between the same volume groups of saline and acetate Ring's solution respectively and between the same initial renal function groups, namely no AKI, AKI stage 1, AKI stage 2 and AKI stage 3, respectively. In this section, a logistic regression model with the primary outcome will be conducted to detect whether it differs significantly between saline and acetate Ringer's solution infusion on renal outcome in the same volume group or the same initial renal function group, and then figure out whether the infused volume or initial renal function makes a difference.
Additional secondary analysis
Statistical methods mentioned in the statistical analysis will be applied according to the characteristics and distribution of the data.
- Compare the secondary outcome between two groups;
- Subgroup analysis will include:
- Septic shock (yes/no)
- The APACHE II scores and SOFA scores at the day of enrolment
- Receipt of mechanical ventilation (yes/no) and ventilation days
- Receipt of vasopressor (yes/no), vasopressor category and max dose
- Receipt of RRT (yes/no) and RRT days
- Stage of AKI on the enrolment day (no AKI, AKI, chronic kidney disease without receiving RRT regularly)
- Main diagnosis at the time of admission to hospital (nervous system disease, respiratory system disease, cardiovascular system disease, digestive system disease, urinary system disease, hematologic system disease, endocrine system disease)
- Complications (Hypertension, diabetes, coronary heart disease, etc.)
Handing of missing data
Of the primary outcome, data of the rate of AKI and the percentage of new receipt of RRT are not supposed to be missing for any patients. Nevertheless, some data of renal function may be missing due to protocol executive errors or record-keeping errors. Mean completer, hot deck imputation and filling manually will be taken to minimize the effects of these missing data as much as possible. For example, if the renal function values near the missing value are in the normal range or have the same trend, the missing data will be averaged or filled with proximity. Patients without a serum creatinine measurement between enrolment and hospital discharge who survive and do not receive new RRT will be considered as not having experienced MAKE. If the patients or authorized agents give up treatment due to little chance to survive predicted by clinicians, their outcome is considered to be death.
Besides, in-hospital mortality may be missing due to patients or authorized agents giving up treatment or other unpredictable accidents when the illness is not that severe. Data may also be missing due to severe adverse events (SAEs) or patients quitting the trial. Under these circumstances, an intention-to-treat analysis will be conducted to deal with the missing data. Of other outcomes, deletion will be considered if the missing data is too large to fill. Indices with complete data after conservative imputation will be included in the statistical analysis.
Data collection and management
Patients’ demographic data, main diagnosis, comorbidities, assigned crystalloids, general vital signs, SOFA scores, APACHE II, infection indices and indices of multi-organ function including renal function, respiratory function, cardiac function, etc. at the time of enrolment will be collected as baseline data. Clinical information including infection indices (white blood cells count, procalcitonin, etc.), organ function indices (renal function (creatinine, urea nitrogen, cystatin C, urine volumes, etc.), respiratory function (PO2/FiO2, ventilation situation, etc.), hepatic function (total bilirubin), etc.) and indices of internal environment (blood gas analysis) will be detected during the first 5 days in ICU, and treatments such as vasopressors, mechanical ventilation, RRT and electrolytes supplement will be recorded. These data and infused volumes of the assigned fluids will be collected for at least 5 days or until ICU discharge. ICU stay days, vasopressor days, RRT days and ventilation days will be counted during 28 days after enrolment. These data will be collected to assess and analyze primary and secondary outcomes. Besides, patients’ blood and urine samples within the first 3 days after enrolment will be collected and stored for testing possible biomarkers for identifying AKI at an early stage.
Patients' information and clinical data will be collected from the Hospital Information System (HIS) of the hospitals involved in this study, and recorded in the Case Report Format (CRF) by the trial manager or trained personnel. An electronic password-protected excel, which will be applied for statistical analysis, will be created to summarize the data of all participants. All the data will be accessed by only investigators and authorized personnel to monitor the completeness and authenticity of the table. The confidentiality is secured and all the data will be preserved for the purpose of a secondary analysis or investigations by the investigators. To protect patients' privacy, their names will not appear on the CRF table. Every participant will only be recognized by their study ID.
Risk evaluation and adverse events
The trial is considered to pose a low risk. Firstly, saline and acetate Ringer's solution have already been widely used in the clinical practice of ICUs of the above hospitals. Secondly, it still remains controversial which fluid (saline or balanced crystalloid solution) is better for septic patients. Thirdly, clinicians are allowed to make clinical judgments and choose the other crystalloid for a specific patient if they think the assigned one may increase the risk of poor prognosis. For instance, clinicians are authorized to give acetate Ringer's solution to patients with severe hyperchloremia for resuscitation in the month when saline is supposed to be used for the safety of participants. Therefore, the adverse events (AEs) of this trial may be minimal.
Still, during the entire observational 28 days from the beginning of the trial, possible AEs will be assessed and recorded in the CRF table. Investigators will evaluate the relationship between the events and our intervention by clinical judgment, and the events will be graded as mild, moderate and severe. SAEs should be considered if unexpected clinically significant critically ill diseases which may be resulted from fluid intervention happen. AEs, especially SAEs, must be reported to DSMB and followed until they are solved. At the end of the trial, AEs and their relationship to the study will be documented in a table and submitted.