The aim of the study was to investigate the clinical features and risk factors on outcomes of patients with cardiorenal syndrome (CRS) in the surgical intensive care unit (SICU).

The clinical data of the patients admitted to SICU of Peking University People's Hospital from January 1st, 2017 to December 31st, 2017 were analyzed retrospectively, including gender, age, severity of the disease, underlying diseases, type of CRS, precipitating factors of CRS, cardiac and renal function [cardiac troponin I (cTnI), B-type natriuretic peptide (BNP).

Serum creatinine (SCr), glomerular filtration rate (eGFR)], outcomes [secondary outcomes, duration of mechanical ventilation, the length of ICU stay, the length of hospital stay, 28-day mortality and hospital mortality] were also analyzed.

Patients were grouped according to CRS classification or hospitalization prognosis, the clinical features within different CRS types were analyzed, and risk factors on outcomes of the CRS patients were analyzed by Logistic regression.

A total of 86 (7.3%) of the 1 172 patients during the study period had CRS. CRS clinical features: CRS 1-5 type patients accounted for 24.4% (21 cases), 1.2% (1 case), 20.9% (18 cases), 1.2% (1 case) and 52.3% (45 cases) respectively, CRS type 1, 3 and 5 were the main types (i.e. acute cardiac and renal dysfunction), while type 5 CRS was the highest (i.e. organ dysfunction caused by simultaneous involvement of cardiac and renal functions secondary to systemic diseases was the most common).

Baseline BNP (Z = 11.365, P = 0.023), SCr peak (Z = 13.405, P = 0.009) and baseline eGFR (F = 2.648, P = 0.037) were significantly different within the CRS 5 types. The basic cardiac function of type 1 CRS patients was significantly worse than that of type 3 and type 5 CRS patients [baseline BNP (μg/L): 434.2 (187.0, 1 252.0) vs. 154.9 (66.4, 272.5), 268.5 (124.1, 486.6), both P < 0.05].

Type 3 CRS patients

The basic renal function of type 3 CRS patients was significantly worse than that of type 5 CRS patients [baseline eGFR (mL/min): 71.0±30.3 vs. 88.3±29.0, P < 0.05]. The severity of acute kidney injury (AKI) in type 3 CRS patients was significantly higher than that in type 1 and type 5 CRS patients [SCr peak (μmol/L): 285.0 (171.5, 420.6) vs. 143.0 (99.5, 213.5), 189.0 (105.5, 280.5), both P < 0.01].

There were no significant differences in gender, age, department, acute physiology and chronic health evaluation II (APACHE II), intraoperative blood loss, basic cTnI, and SCr levels, BNP peak, AKI staging and prognostic indicators among patients with various types of CRS.

Death risk analysis: 43 (50%) of the 86 CRS patients died during the hospital stay. Compared with the survival patients, CRS death patients were older [years old: 72 (57, 80) vs. 62 (50, 73)] and had higher APACHE II score [22 (17, 29) vs. 18 (15, 21)], with higher proportion of cerebrovascular disease (9.3% vs. 0).

Regarding precipitating factors of CRS, sepsis/septic shock (41.9% vs. 18.6%) and surgery stress (9.3% vs. 0) were remarkably increased in dying patients. Death patients had higher cTnI and SCr peak [cTnI peak (μg/L): 1.155 (0.192, 5.125) vs. 0.122 (0.045, 0.610), SCr peak (μmol/L): 208 (143, 295) vs. 146 (101, 289)].

And also high proportion of AKI stage 3 (41.9% vs. 20.9%), higher rate of secondary infection (67.4% vs. 30.2%), prolonged duration of mechanical ventilation and the length of ICU stay [hours: 179 (61, 470) vs. 37 (7, 134); days: 10 (4, 24) vs. 5 (2, 11)], with statistically significant differences (all P < 0.05).

Logistic regression analysis showed that the elderly [odds ratio (OR) = 1.053, 95% confidence interval (95%CI) = 1.003-1.094, P = 0.010], high APACHE II score (OR = 1.165, 95%CI = 1.057-1.285, P = 0.002), sepsis/septic shock (OR = 4.561, 95%CI = 1.351-15.391, P = 0.014) and AKI stage 3 (OR = 5.468, 95%CI = 1.457-20.530, P = 0.012) were independent risk factors for hospital death in CRS patients.

Surgical ICU patients with CRS are characterized by acute cardiac and renal dysfunction. CRS type 5 is the most common and has a high fatality rate. Age, the severity of illness, sepsis/septic shock and AKI stage 3 are independent risk factors of death.