Cardiac surgery-associated acute kidney injury and perioperative plasma viscosity: is there a relationship?

Plasma viscosity (PV) is a key factor in microcirculatory flow resistance and capillary perfusion during hemodilution, we hypothesized a possible relationship between cardiac surgery-associated acute kidney injury (CSA-AKI) and PV. We conducted a prospective, observational, single-center study on 50 adult cardiac surgery patients with cardiopulmonary bypass (age 64 years, male sex 80%, baseline serum creatinine 1.04 mg/dL). We assessed perioperative characteristics, management, short-term outcomes, blood analysis, PV, serum creatinine, and diuresis. CSA-AKI was identified using KDIGO criteria. Data were collected at 10 time points during the first perioperative week. CSA-AKI occurred in 17 patients (34%): 12 (24%) stage 1, 1 (2%) stage 2, and 4 (8%) stage 3. Most patients (88%) developed CSA-AKI within 48 h post-surgery. Patients with CSA-AKI had higher body mass index (BMI), more frequent chronic kidney disease (CKD), and lower hemoglobin and hematocrit levels. The median baseline PV for the entire cohort was 1.50 cP on EDTA and 1.37 cP on citrate. No significant differences in PV levels were found between patients with CSA-AKI and normal kidney function, both at baseline and at the 48-h. Logistic and Cox regression analyses showed no significant relationship between PV and CSA-AKI. However, CSA-AKI was related to increased BMI, lower hemoglobin and hematocrit levels, and pre-existing CKD. The present study found no significant association between PV and CSA-AKI. Nevertheless, more research is needed to validate this finding and to investigate the role of PV in other clinical settings.

Perioperative Trajectory of Haemoglobin, Predictors of Blood Transfusion and Tailoring Targets for Patient Blood Management Interventions: A Single-centre, Retrospective Study of Non-emergent Cardiac Surgery Patients.

Background: Anaemia and blood transfusion are two independent contributing factors to perioperative morbidity in cardiac surgery. While preoperative treatment of anaemia has been shown to improve outcomes, in real life, logistical difficulties remain substantial, even in high-income countries. The adequate trigger for transfusion in this population remains controversial, and there is a wide variability in transfusion rates among centres. Objectives: To assess the impact of preoperative anaemia on perioperative transfusion in elective cardiac surgery,todescribe the perioperative trajectory of haemoglobin (Hb), to stratify outcomes based on preoperative presence of anaemia and to identify predictors of perioperative blood transfusion. Materials: and Methods: We included a retrospective cohort of consecutive patients who underwent cardiac surgery with cardiopulmonary bypass in a tertiary centre of cardiovascular surgery. Recorded outcomes included hospital and intensive care unit (ICU) length of stay (LOS), surgical re-exploration due to bleeding, packed red blood cell (PRBC) transfusion pre-, intra- and postoperatively. Other record perioperative variables were preoperative chronic kidney disease, duration of surgery, use of rotation thromboelastometry (ROTEM) and cell saver, and fresh frozen plasma (FFP) and platelet (PLT) transfusion. Hb values were recorded at four distinct time points: Hb1 - at hospital admission, Hb2 - last Hb recorded preoperatively, Hb3 - first Hb recorded postoperatively and Hb4 - at hospital discharge. We compared the outcomes between anaemic and non-anaemic patients. Transfusion was decided by the attending physician on a case-by-case basis. Results: Of the 856 patients operated during the selected period, 716 underwent non-emergent surgery and 710 were included in the analysis. Also, 40.5% (n = 288) of patients were anaemic preoperatively (Hb <13 g/dl); 369 patients (52%) were transfused PRBCs, with differences found between anaemic and non-anaemic patients regarding the percentage of transfused patients perioperatively (71.5% vs 38.6%, p < 0.001) and in the total median number of units transfused (2 [IQR 0-2] vs 0 [IQR 0-1], p <0.001). We built a multivariate model, and logistic regression analysis showed that preoperative Hb <13 g/dl (odds ratio [OR] 3.462 [95% CI 1.766-6.787]), female sex (OR 3.224 [95% CI 1.648-6.306]), age (1.024 per year [95% CI 1.0008-1.049]), hospital LOS (OR 1.093 per day of hospitalisation [95% CI 1.037-1.151]) and FFP transfusion (OR 5.110 [95% CI 1.997-13.071]) are associated with PRBC transfusion. Conclusions: Untreated preoperative anaemia leads to more transfusion in elective cardiac surgery patients, both as a ratio of transfused patients and as the number of units of PRBCs per patient, and this is associated with an increased use in FFP.