The Effects of Administration of Exogenous Albumin Early after Non-cardiac Surgery on Postoperative AKI in Patients with Preoperative Hypoalbuminemia: A Prospective Propensity-score Matching Analysis

doi:10.21203/rs.3.rs-1131516/v2

Background: Evidence has shown that preoperative hypoalbuminemia is independently associated with acute kidney injury (AKI) after non-cardiac surgery. However, little study has investigated the effects of administration of exogenous albumin early after non-cardiac surgery on postoperative AKI in patients with preoperative hypoalbuminemia.

Methods: This study was a secondary analysis of the database of a previously conducted prospective cohort study. Data of 661 adult patients who underwent non-cardiac surgery and were admitted to Surgical Intensive Care Unit (SICU) after surgery from May 1, 2019, to November 30, 2020, were collected. 267 patients with preoperative hypoalbuminemia were screened, and divided into two groups according to whether they were administrated with exogenous albumin on the day of SICU admission. The demographic and perioperative data of the two groups were propensity-matched.

Results：After propensity score matching, 64 pairs of patients were included in the final analysis. The patients of the albumin group showed a higher serum albumin level on postoperative day 1 than that in patients of the control group [31.3±3.4 vs. 29.7±3.8, P=0.008], however, no difference was observed in postoperative AKI incidence between the two groups (59.4% vs. 62.5%, P=0.717). Furthermore, there was no difference in other prognostic factors, such as the use and duration of mechanical ventilation, number of other postoperative complications, in-hospital mortality, length of SICU stay and postoperative hospital stay.

Conclusions: The current study did not exhibit benefit of exogenous albumin administration early after non-cardiac surgery on the occurrence of postoperative AKI in patients with preoperative hypoalbuminemia, which needs to be confirmed by further large randomized controlled researches in the future.

Hypoalbuminemia

Acute kidney injury

Exogenous albumin infusion

Acute kidney injury (AKI) is a common complication after surgery among different patient populations, and postoperative AKI is associated with poor outcomes[1]. In the absence of proven effective treatments for AKI, early recognition of modifiable risk factors and the development of renal protective strategies would be beneficial.

Perioperative hypoalbuminemia has proved to be a risk factor for increased incidence of postoperative AKI[2-7]. Renal protective properties of albumin have been shown in amount of clinical and basic studies[8-11]. Serum albumin may play a protective role in the maintenance of effective circulating volume and renal perfusion, preservation of proximal tubular integrity and function, binding of endogenous toxins and nephrotoxic drugs, scavenging and limiting the production of reactive oxygen species, and delivery of protective lysophosphatidic acid. In addition, albumin can improve microcirculatory blood flow and reduce the inflammatory response.

In our previous study, a preoperative serum albumin level of less than 37.5g/L was found to be independently associated with postoperative AKI in patients undergoing non-cardiac surgery[2]. We suppose that correction of hypoalbuminemia may be a reasonable preventive strategy for postoperative AKI. Although administration of exogenous albumin for correcting hypoalbuminemia has been widely used in various clinical settings, there are limited data on whether perioperative albumin intravenous infusion affects the occurrence of postoperative AKI, and its usefulness for organ protection is still a matter of debate[12]. This study was conducted to prospectively evaluate the effect of administration of exogenous albumin early after surgery on postoperative AKI occurrence in patients with preoperative hypoalbuminemia following non-cardiac surgery.

Ethics and consent

This study was a secondary analysis of the database of a previously conducted prospective cohort study investigating the perioperative predictors of AKI following non-cardiac surgery. Ethical approval (2019-075) was provided by the Clinical Research Ethics Committee of Peking University First Hospital. The privacy rights of participants were observed. The original study was conducted in the Surgical Intensive Care Units (SICU) of Peking University First Hospital from May 1, 2019, to November 30, 2020. Written informed consents were obtained from patients, their next of kin or their legal representatives.

Patients

The inclusion criteria included (1) adult patients (age≥18 years), (2) undergoing non-cardiac surgery, and (3) being admitted to SICU immediately after surgery. Patients with any of the following criteria were excluded: (1) preoperative chronic kidney disease stage 5 or requiring long-term dialysis; (2) surgery involving kidney, such as nephrectomy, partial nephrectomy, nephroureterectomy, or kidney transplantation; (3) AKI events before admission to SICU; (4) without Foley catheter placement; and (5) written informed consent not obtained. Our medical center is a teaching hospital affiliated with a university, which provides tertiary care and has about 1600 beds.

Data collection

Specially trained researchers were responsible for patient recruitment and data collection. The data of patients were collected from the electronic medical records system of our hospital. Preoperative information included demographic characteristics (age, gender), body mass index (BMI), medical history, nephrotoxin exposure, American Society of Anesthesiology (ASA) Classification of Physical Status, as well as preoperative clinical laboratory data. Intraoperative data included type and duration of surgery, surgical approach, anesthesia method, duration of anesthesia, fluid input and output, estimated blood loss, occurrence of hypotension and duration, and use of vasoactive drugs. Postoperative data included non-renal Sequential Organ Function Assessment (SOFA) score within 24h of SICU admission and sepsis on SICU admission.

Definition and outcomes

The cutoff value of preoperative hypoalbuminemia was 37.5g/L, which referred to our previous research reporting that preoperative serum albumin level less than 37.5g/L was an independent risk factor for AKI after non-cardiac surgery[2].

The timing of early administration of exogenous albumin was defined as being less than 12 hours after surgery. In our department, 20% albumin is generally administrated either in patients who require persist fluid resuscitation, or in patients who need to maintain a high colloidal osmotic pressure, such as patients with intracranial hypertension or a very low albumin level[13].

Postoperative follow-up was performed. The primary end point was postoperative AKI development. Postoperative AKI were defined according to Kidney Disease Improving Global Outcomes (KDIGO) criteria using the maximal change in serum creatinine compared with the preoperative baseline values and urine output during the first 7 postoperative days[14].

The secondary end points were the amount of early albumin infusion, the level of serum albumin on postoperative day 1, positive fluid balance on the day of SICU admission, postoperative use and duration of mechanical ventilation (MV), length of stay in SICU and hospital after surgery, occurrence of postoperative complications other than AKI, and in-hospital mortality. Other main postoperative complications were pulmonary infection, pleural effusion, pulmonary atelectasis, respiratory failure, surgical bleeding, new-onset arrhythmia, acute myocardial infarction, hemodynamic insufficiency, stroke, ileus, anastomotic leakage, intra-abdominal abscess, acute liver injury, wound infection, wound dehiscence, urinary tract infection, sepsis, disseminated intravascular coagulation, digestive tract bleeding, and venous thromboembolism (Table S1).

Statistical analysis

The Kolmogorov-Smirnov method was used to test the normality of continuous variables. Normally distributed data were presented as mean ± standard deviation (SD), and non-normally distributed data were presented as median (minimum-maximum). Categorical variables were presented as number (percentage). Analyses of the frequencies of categorical variables were performed using chi-squared test or Fisher’s exact test. Differences in quantitative variables between two independent groups were tested with t-test or Mann–Whitney U test.

Several underlying susceptibilities, procedures, or exposures have been identified as risk factors of postoperative AKI occurrence[3, 15].Variables being considered clinically relevant were used for propensity score matching and selected a priori. These variables included age, gender, BMI, preoperative comorbidities, preoperative and postoperative albumin, ASA classification, type and duration of surgery, type and duration of anesthesia, intraoperative hemodynamic instability and postoperative non-renal SOFA. The propensity score matching was conducted using multivariate logistic regression. Patients were matched in a 1:1 ratio based on their scores using the nearest-neighbor matching with the tolerance being 0.1. Between-group differences of baseline and perioperative variables for propensity score matching were compared using the absolute standardized differences (ASDs)[16], which were calculated as (mean1-mean2)/SD1. An ASD ≥0.250

was considered imbalanced between the two groups.

Data analyses were performed with SPSS 26.0. Two-tailed P values lower than 0.05 were considered statistically significant.

Participants

During the enrollment period, a total of 661 patients who underwent non-cardiac surgery and were admitted to SICU met the inclusion/exclusion criteria. Of the 247 patients with preoperative hypoalbuminemia, 130 received administration of 20% albumin early after surgery (albumin group), with 25 (19.2%) receiving albumin for hemodynamic stabilization and improving organ perfusion, 70 (53.8%) receiving albumin to maintain high colloid osmolarity, and 35 (26.9%) receiving albumin for the both aims. The amounts of the received albumin were 20 (10-100) gram, 20 (10-150) gram and 30 (10-50) gram, respectively. The remaining 117 did not receive postoperative early albumin infusion (control group). Propensity score matching was performed to match the baseline and perioperative variables. Ultimately, 64 pairs of patients were included in the final statistical analysis. Figure 1 showed the flow diagram of the study.

Baseline and perioperative data

In this study, the baseline and perioperative data of the 247 patients with preoperative hypoalbuminemia were analyzed. Compared with patients of the control group, those of the albumin group had more history of coronary heart disease, more ACEI/ARB medication history, lower preoperative and postoperative albumin; they underwent more abdominopelvic surgery and general anesthesia; they had longer duration of surgery and anesthesia; they received more fluids during surgery; they showed more intraoperative hypotension and received more vasoactive drugs; they had higher non-renal SOFA within 24h of SICU admission and more sepsis on SICU admission. After propensity score matching, the above variables of the two groups were well balanced (Tables 1-3).

Primary and secondary endpoints

The patients of the albumin group were administrated with 20 (10-150) gram albumin early after surgery, and serum albumin on postoperative day 1 in patients of the albumin group was higher than that in patients of the control group [31.3±3.4 vs. 29.7±3.8, P=0.008], which indicated that administration of albumin early after surgery did improve the albumin level on postoperative day 1. However, there was no difference in postoperative AKI incidence between the two groups (59.4% vs. 62.5%, P=0.717). Furthermore, higher positive fluid balance on the day of SICU admission was observed in the albumin group, but not statistically significant [36.5 (4.0-337.0) vs. 32.0 (4.0-128.0), P=0.064] (Table 4).

Regarding other secondary end points, no difference was found in the use and duration of MV, number of other postoperative complications, in-hospital mortality and postoperative hospital stay between the two groups (Table 4). Particularly, the tendency of longer duration of SICU stay in the albumin group was noticed, although no statistical difference was observed [2.0 (1.0-23.0) vs. 1.0 (1.0-66.0), P=0.090]. As for postoperative complications, the rate of sepsis seemed to be higher in patients of the albumin group (18.8% vs. 6.3%, P=0.059] (Table S1). One of the most common organs affected by sepsis is the kidney, resulting in sepsis associated AKI that contributes to the morbidity and mortality of sepsis[17]. Sepsis associated AKI was diagnosed in 6 (9.4%) patients of the albumin group, and 2 (3.1%) patients of the control group (P=0.273). Besides, the rate of acute myocardial infarction was found to be higher in patients of the albumin group (9.4% vs. 0.0%, P=0.028) (Table S1).

In this study, we prospectively analyzed the association between administration of exogenous albumin early after non-cardiac surgery and postoperative AKI in patients with preoperative hypoalbuminemia. Although the patients of the albumin group exhibited a higher serum albumin level on postoperative day 1, no differences were observed in postoperative AKI occurrence and other prognostic factors between the two groups.

Cumulative evidence has shown that a perioperatively reduced serum albumin level may contribute to an increased risk of postoperative AKI in various clinical settings[1-4, 6, 7]. There are several factors responsible for the changes in albumin concentration after surgery: (1) Large amounts of fluid infusion during the operation leads to the dilution of plasma albumin; (2) The ability of liver to synthesize albumin decreases under stress; (3) Decomposition of albumin is increased to compensate for energy expenditure under stress; (4) The permeability of capillaries increases in the systemic inflammatory responses, and plasma albumin molecules leak out from the blood vessels; (5) Albumin is lost with blood loss during surgery. Among the above factors, the blood dilution and the exudation of albumin molecules out of the capillaries were considered to be the main causes of postoperative hypoalbuminemia[18, 19].

Currently, the conclusions of limited studies investigating the effect of perioperative exogenous albumin infusion on occurrence of postoperative AKI are not consistent. Eun-Ho Lee et al. prospectively reported that administration of exogenous albumin immediately before surgery reduced the risk of AKI after off-pump coronary artery bypass surgery in patients with a preoperative serum albumin level of less than 4.0 g/dl, although the observed difference in that study was only marginally significant (P=0.048)[12]. On the contrary, in the retrospective cohort study of Anne Julie Frenette et al, a dose-dependent AKI risk associated with the administration of albumin until 36 hours after surgery was observed in patients undergoing on-pump cardiac surgery[20].

To the best of our knowledge, this is the first prospective cohort study investigating the association of albumin infusion early after non-cardiac surgery and incidence of postoperative AKI. In our study, there was no difference in occurrence of postoperative AKI in patients of the two groups, which did not show improvement of administration of exogenous albumin early after non-cardiac surgery on renal outcome. Several reasons were supposed to be responsible for the result. As mentioned above, surgery and the systemic inflammatory responses increase capillary permeability significantly, and massive albumin molecules leak out of the capillaries into the interstitial space, so the effect of correcting the hypoalbuminemia and the renal protective properties of serum albumin would not sustained. From this perspective, administration of exogenous albumin early after surgery, especially for major abdominopelvic surgery, is cost and unhelpful. On the contrary, with the subsidence of systemic inflammatory responses and the optimization of nutritional status, the level of serum albumin tends to recover spontaneously[21]. Additionally, in our study, although exogenous albumin was administrated early after surgery, the level of serum albumin in more than 89% of the patients was still lower than the threshold value, and the possibility that the dosage of exogenous albumin might not be sufficient could not be excluded completely. Furthermore, the causes of postoperative AKI are complicated and multifactorial. The isolated procedure of postoperative administration of exogenous albumin may not be enough to inhibit the pathological process leading to AKI in these high-risk patients.

As for the secondary outcomes, the rate of sepsis seemed to be higher in patients of the albumin group (Table S1). This difference was supposed to be relevant to the higher rate of abdominopelvic surgery (67.2% vs. 57.8%) and open surgery (54.7% vs. 39.1%) in patients of the albumin group (Table 2-3), which predisposed patients to a high risk of infection. Meanwhile, despite propensity score was matched between the two groups, there might be some confounding factors that have not been well balanced and a selective bias might exist. For sepsis associated AKI, there was no statistical difference between the two groups. The incidence rate of acute myocardial infarction was found to be higher in the albumin group (Table S1), which might be explained by the higher rate of preoperative T2DM (28.1% vs. 23.4%) (Table 1) and postoperative sepsis (18.8% vs. 6.3%) in this group of patients. Specially, the higher incidence rates of postoperative complications mentioned above were also the main factors that were responsible for the longer SICU stay in these patients (Table 4).

There are several other shortcomings in this study. Firstly, the standard of timing and dosage of albumin administration was absent. A definite treatment regime of albumin administration should be established. Secondly, a specific control fluid was not administrated in patients of control group, although the difference in the positive fluid balance between the two groups was not significant. Finally, the sample size after propensity score matching was relatively small, and an expanded population would guarantee an increased statistical power. Therefore, a large randomized controlled study is needed to evaluate the above issues.

As the first prospective cohort study investigating the association between albumin infusion and incidence of AKI after non-cardiac surgery, the current study did not exhibit benefit of exogenous albumin administration early after non-cardiac surgery on the occurrence of postoperative AKI in patients with a preoperative serum albumin level of less than 37.5g/L. We believe this study will form the basis for further researches in the future.

Ethics approval and consent to participate

Ethical approval (2019-075) was provided by the Clinical Research Ethics Committee of Peking University First Hospital. We confirmed that all methods were performed in accordance with relevant guidelines and regulations. Written informed consents were obtained from patients, their next of kin or their legal representatives.

Consent for publication

Not applicable.

Availability of data and materials

The datasets are not publicly available, but available from the corresponding author on reasonable request.

Competing interests

The authors declare that they have no competing interests.

Funding

The study was funded by the Clinical Research Program of Peking University First Hospital (2019CR09).

Authors’ Contributions

MY helped design the study, analyze the data, and draft the manuscript. WJZ helped design the study and perform data collection. MX helped design the study and perform data collection. SNZ helped analyze and interpret data. NL helped design the study, perform data collection, analyze data, draft and revise the manuscript. SLL helped design the study and interpret data. All authors have read and approved the manuscript.

Acknowledgements

The authors gratefully acknowledge Professor Dong-Xin Wang for his suggestions on study design and data analysis.

AKI: acute kidney injury; SICU: Surgical Intensive Care Unit; CKD: chronic kidney disease; BMI: body mass index; ASA: American Society of Anesthesiology; SOFA: Sequential Organ Function Assessment; KDIGO: Kidney Disease Improving Global Outcomes; MV: mechanical ventilation; SD: standard deviation; ASD: absolute standard difference; NA, not applicable.

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Table 1. Baseline and Preoperative Variables Used for Propensity Score Matching

		Full cohort (n=247)			Matching cohort (n=128)
	All (n=247)	Albumin group (n=130)	Control group (n=117)	ASD	Albumin group (n=64)	Control group (n=64)	ASD
Age (y)	77 (23-99)	74 (27-99)	78 (23-95)	0.106	74 (29-97)	78 (23-95)	0.004
Male sex	144 (58.3%)	73 (56.2%)	71 (60.7%)	0.100	41 (64.1%)	38 (59.4%)	0.103
BMI (kg/m²)	23.0 (14.3-38.5)	22.9 (14.3-37.0)	23.3 (16.6-38.5)	0.183	22.7 (15.2-31.8）	23.1 (17.0-36.2)	0.171
Hypertension	141 (57.1%)	70 (53.8%)	71 (60.7%)	0.140	33 (51.6%)	36 (56.3%)	0.079
T2DM	65 (26.3%)	35 (26.9%)	30 (25.6%)	0.022	18 (28.1%)	15 (23.4%)	0.110
CKD	34 (13.8%)	17 (13.1%)	17 (14.5%)	0.059	9 (14.1%)	11 (17.2%)	0.086
Preoperative albumin (g/L)	33.9 (20.7-37.4)	33.3 (20.7-37.4)	34.6 (21.0-37.4)	0.367	33.8 (25.1-37.4)	33.6 (21.0-37.4)	0.071
ASA classification				0.029			0.000
I-II	35 (14.2%)	18 (13.8%)	17 (14.5%)		10 (15.6%)	10 (15.6%)
III-IV	212 (85.8%)	112 (86.2%)	100 (85.5%)		54 (84.4%)	54 (84.4%)

Data are presented as mean±SD, median (minimum-maximum) or number (percent).

Abbreviations: ASD, absolute standardized difference; BMI, body mass index; T2DM, Type 2 diabetes; CKD, chronic kidney disease; ASA, American Society of Anesthesiologists.

Table 2. Intraoperative and Postoperative Variables Used for Propensity Score Matching

		Full cohort (n=247)			Matching cohort (n=128)
	All (n=247)	Albumin group (n=130)	Control group (n=117)	ASD	Albumin group (n=64)	Control group (n=64)	ASD
Site of surgery				0.546			0.157
Abdominopelvic	157 (63.6%)	96 (73.9%)	61 (52.1%)		43 (67.2%)	37 (57.8%)
Thoracic	26 (10.5%)	12 (9.2%)	14 (12.0%)		7 (10.9%)	9 (14.1%)
Neural	7 (2.8%)	2 (1.5%)	5 (4.3%)		1 (1.6%)	3 (4.7%)
Orthopedic	54 (21.9%)	20 (15.4%)	34 (29.0%)		13 (20.3%)	15 (23.4%)
other	3 (1.2%)	0 (0.0%)	3 (2.6%)		0 (0.0%)	0 (0.0%)
Type of surgery				0.158			0.137
Open	113 (45.7%)	75 (57.7%)	38 (32.5%)		35 (54.7%)	25 (39.1%)
Laparoscopic	81 (32.8%)	38 (29.2%)	43 (36.7%)		20 (31.3%)	22 (34.4%)
Non-relevant	53 (21.5%)	17 (13.1%)	36 (30.8%)		9 (14.1%)	17 (26.6%)
Duration of surgery (min）	195 (29-925)	210 (29-925)	183 (33-783)	0.292	186 (29-715)	183 (33-783)	0.056
Type of anesthesia				0.530			0.141
General	234 (94.7%)	127 (97.7%)	107 (91.5%)		61 (95.3%)	60 (93.8%)
Epidural	11 (4.5%)	3 (2.3%)	8 (6.8%)		3 (4.7%)	3 (4.7%)
Reginal block	2 (0.8%)	0 (0.0%)	2 (1.7%)		0 (0.0%)	1 (1.6%)
Duration of anesthesia (min)	279 (70-1012)	289 (84-1012)	273 (70-859)	0.273	255 (84-802)	275 (70-859)	0.065
Intraoperative hypotension ^a	138 (55.9%)	87 (66.9%)	51 (43.6%)	0.487	35 (54.7%)	38 (59.4%)	0.080
Intraoperative vasoactive drugs ^b	151 (61.1%)	88 (67.7%)	63 (53.8%)	0.299	41 (64.1%)	39 (60.9%)	0.062
Intraoperative hypotension (min)	15 (5-345)	20 (5-345)	10 (5-240)	0.177	15 (5-120)	10 (5-240)	0.024
Postoperative albumin (g/L)	29.2 (10.5-41.9)	27.2 (10.5-37.6)	31.4 (18.0-41.9)	0.847	29.3 (19.8-37.6)	30.2 (18.0-38.9)	0.028
Non-renal SOFA	3.0 (0.0-11.0)	3.5 (0.0-11.0)	3.0 (0.0-10.0)	0.523	3.0 (0.0-10.0)	3.0 (0.0-10.0)	0.177

Data are presented as mean±SD, median (minimum-maximum) or number (percent).

Abbreviations: ASD, absolute standardized difference; SOFA, sequential organ function assessment.

^aIndicates intraoperative systolic blood pressure lower than 90mmHg, or lower than the baseline value by more than 30%.

^bIncluding dopamine, dobutamine, norepinephrine, ephedrine, phenylephrine, epinephrine and meta-hydroxylamine.

Table 3. Perioperative Variables Not Used for Propensity Score Matching

		Full cohort (n=247)			Matching cohort (n=128)
	All (n=247)	Albumin group (n=130)	Control group (n=117)	P value	Albumin group (n=64)	Control group (n=64)	P value
Preoperative comorbidities
Coronary heart disease	79 (32.0%)	33 (25.4%)	46 (39.3%)	0.019	20 (31.3%)	19 (29.7%)	0.848
Cerebrovascular disease	44 (17.8%)	26 (20.0%)	18 (15.4%)	0.344	10 (15.6%)	12 (18.8%)	0.639
Preoperative Hb (g/L)	108.5±18.5	108.1±17.8	109.0±19.2	0.723	108.4±16.3	105.0±19.0	0.834
Baseline serum creatinine (μmol/L)	72.6 (18.1-286.8)	71.1 (27.9-286.8)	74.6 (18.1-238.31)	0.151	75.6 (44.7-242.0)	68.11 (18.1-238.3)	0.464
Baseline eGFR [ml/(min·1.73m²)]	82.2 (18.8-156.1)	81.5 (22.4-156.1)	82.9 (18.8-134.5)	0.198	81.4 (22.6-132.4)	83.5 (25.0-156.1)	0.637
Preoperative BNP (pg/ml)	92.0 (2.8-1622.0)	86.5 (2.8-1197.0)	99.0 (9.0-1622.0)	0.623	80.0 (9.0-1197.0)	81.0 (9.0-791.0)	0.792
Radiocontrast exposure	25 (10.1%)	15 (11.5%)	10 (8.5%)	0.436	7 (10.9%)	6 (9.4%)	0.770
On ACEI/ARB	41 (16.6%)	14 (10.8%)	27 (23.1%)	0.009	6 (9.4%)	10 (15.6%)	0.285
Intraoperative fluid input (ml)	2350 (500-21800)	2825 (550-21800)	1850 (500-8500)	0.000	2350 (550-8293)	1975 (900-8500)	0.116
Intraoperative artificial colloid (ml)	500 (100-3500)	500 (100-3500)	500 (500-1700)	0.174	500 (100-1500)	500 (500-1700)	0.298
Intraoperative fluid output (ml)	600 (10-8650)	625 (50-8650)	520 (10-2800)	0.096	500 (50-2700)	600 (50-2800)	0.351
Intraoperative estimated blood loss (ml)	100 (5-6000)	100 (5-6000)	100 (5-2000)	0.089	100 (10-1700)	100 (5-2000)	0.669
Sepsis on SICU admission	9 (3.6%)	9 (6.9%)	0 (0.0%)	0.004	0 (0.0%)	0 (0.0%)	NA

Data are presented as mean±SD, median (minimum-maximum) or number (percent).

Abbreviations: Hb, hemoglobin; eGFR, estimated glomerular filtration rate; BNP, type B natriuretic peptide; ACEI/ARB, angiotensin-converting enzyme inhibitor/angiotensin receptor blocker; SICU, Surgical Intensive Care Unit; NA, not applicable.

Table 4. Primary and Secondary Outcomes of the Study in Matched Patients

	Total (n=128)	Albumin group (n=64)	Control group (n=64)	P value
Postoperative AKI	78 (60.9%)	38 (59.4%)	40 (62.5%)	0.717
Albumin on postoperative day 1 (g/L)	30.6±3.6	31.3±3.4	29.7±3.8	0.008
Positive fluid balance on the day of SICU admission (ml/kg)	34.0 (4.0-337.0)	36.5 (4.0-337.0)	32.0 (4.0-128.0)	0.064
On MV in SICU	62 (48.4%)	30 (46.9%)	32 (50.0%)	0.724
Duration of MV (h)	6 (1-1128)	6 (2-392)	6.5 (1-1128)	0.745
Number of postoperative complications except AKI	0 (0-12)	0 (0-11)	0 (0-12)	0.116
In-hospital mortality	6 (4.7%)	2 (3.1%)	4 (6.3%)	0.676
Length of SICU stay (d)	1.5 (1.0-66.0)	2.0 (1.0-23.0)	1.0 (1.0-66.0)	0.090
Postoperative hospital stay (d)	11 (2-72)	11 (2-72)	11.5 (2-71)	0.778

Data were presented as mean±SD, median (minimum-maximum) or number (percentage).

Abbreviations: AKI, acute kidney injury; SICU, Surgical Intensive Care Unit; MV, mechanical ventilation.

No competing interests reported.

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The Effects of Administration of Exogenous Albumin Early after Non-cardiac Surgery on Postoperative AKI in Patients with Preoperative Hypoalbuminemia: A Prospective Propensity-score Matching Analysis

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