Red Cell Transfusion–Associated Hemolysis in Cardiac Surgery

Carboxyhemoglobin in Cardiac Surgery Patients and Its Association with Risk Factors and Biomarkers of Hemolysis

BACKGROUND

Cardiac surgery with cardiopulmonary bypass (CPB) is associated with hemolysis. Yet, there is no easily available and frequently measured marker to monitor this hemolysis. However, carboxyhemoglobin (CO-Hb), formed by the binding of carbon monoxide (a product of heme breakdown) to hemoglobin, may reflect such hemolysis. We hypothesized that CO-Hb might increase after cardiac surgery and show associations with operative risk factors and indirect markers for hemolysis.

METHODS

We conducted a retrospective descriptive cohort study of data from on-pump cardiac surgery patients. We analyzed temporal changes in CO-Hb levels and applied a generalized linear model to assess patient characteristics associated with peak CO-Hb levels. Additionally, we examined their relationship with red blood cell (RBC) transfusion and bilirubin levels.

RESULTS

We studied 38,487 CO-Hb measurements in 1735 patients. CO-Hb levels increased significantly after cardiac surgery, reaching a peak CO-Hb level 2.1 times higher than baseline (P < .001) at a median of 17 hours after the initiation of surgery. Several factors were independently associated with higher peak CO-Hb, including age (P < .001), preoperative respiratory disease (P = .001), New York Heart Association Class IV (P = .019), the number of packed RBC transfused (P < .001), and the duration of CPB (P = .002). Peak CO-Hb levels also significantly correlated with postoperative total bilirubin levels (Rho = 0.27, P < .001).

CONCLUSIONS

CO-Hb may represent a readily obtainable and frequently measured biomarker that has a moderate association with known biomarkers of and risk factors for hemolysis in on-pump cardiac surgery patients. These findings have potential clinical implications and warrant further investigation.

Risk factors analysis and nomogram construction for blood transfusion in elderly patients with femoral neck fractures undergoing hemiarthroplasty

INTRODUCTION

Elderly patients with femoral neck fractures (FNFs) undergoing hemiarthroplasty usually have poor physical condition. The main aim of this study was to identify risk factors for blood transfusion in these patients and construct a nomogram to intuitively predict the requirement of transfusion. The secondary purpose was to examine the relationship between blood transfusion and complications within 30 days post-operatively. Our hypothesis was that chronic kidney disease (CKD) and hypoalbuminemia may increase the requirement of transfusion.

METHODS

Data of 414 elderly patients undergoing hemiarthroplasty for FNFs were retrospectively collected. Univariate and multiple regression analysis were performed to identify independent risk factors for blood transfusion, which were used to construct a nomogram subsequently. The discrimination and calibration of the nomogram model were assessed with concordance index (C-index), the area under receiver operating characteristic curve (AUC), and calibration curve. Furthermore, the complications of blood transfusion within 30 days post-operatively were also analyzed.

RESULTS

Out of 414 patients, 127 (30.7%) received a blood transfusion. Independent risk factors for blood transfusion included CKD, hypoalbuminemia, pre-operative anaemia, general anaesthesia, higher American Society of Anesthesiologists score, more intraoperative blood loss, and longer surgical time. Increased hidden blood loss, deep vein thrombosis, superficial wound infection, and prolonged hospital stays were more common in transfused patients. The C-index of the nomogram model was 0.848 (95% CI = 0.811-0.885), and the AUC value was 0.859. The calibration curve showed a good consistency between the actual transfusion and the predicted probability.

DISCUSSION

We observed a transfusion rate of 30.7% in elderly FNF patients undergoing hemiarthroplasty. CKD and hypoalbuminemia were firstly identified as independent risk for blood transfusion. In addition, blood transfusion can increase the occurrence of early post-operative complications.

CONCLUSION

Targeted pre-operative intervention, such as optimizing CKD and correcting hypoalbuminemia is essential and highly regarded.

Potential Consequences of the Red Blood Cell Storage Lesion on Cardiac Electrophysiology

Background The red blood cell (RBC) storage lesion is a series of morphological, functional, and metabolic changes that RBCs undergo following collection, processing, and refrigerated storage for clinical use. Since the biochemical attributes of the RBC unit shifts with time, transfusion of older blood products may contribute to cardiac complications, including hyperkalemia and cardiac arrest. We measured the direct effect of storage age on cardiac electrophysiology and compared it with hyperkalemia, a prominent biomarker of storage lesion severity. Methods and Results Donor RBCs were processed using standard blood-banking techniques. The supernatant was collected from RBC units, 7 to 50 days after donor collection, for evaluation using Langendorff-heart preparations (rat) or human induced pluripotent stem cell-derived cardiomyocytes. Cardiac parameters remained stable following exposure to "fresh" supernatant from red blood cell units (day 7: 5.8±0.2 mM K+), but older blood products (day 40: 9.3±0.3 mM K+) caused bradycardia (baseline: 279±5 versus day 40: 216±18 beats per minute), delayed sinus node recovery (baseline: 243±8 versus day 40: 354±23 ms), and increased the effective refractory period of the atrioventricular node (baseline: 77±2 versus day 40: 93±7 ms) and ventricle (baseline: 50±3 versus day 40: 98±10 ms) in perfused hearts. Beating rate was also slowed in human induced pluripotent stem cell-derived cardiomyocytes after exposure to older supernatant from red blood cell units (-75±9%, day 40 versus control). Similar effects on automaticity and electrical conduction were observed with hyperkalemia (10-12 mM K+). Conclusions This is the first study to demonstrate that "older" blood products directly impact cardiac electrophysiology, using experimental models. These effects are likely caused by biochemical alterations in the supernatant from red blood cell units that occur over time, including, but not limited to hyperkalemia. Patients receiving large volume and/or rapid transfusions may be sensitive to these effects.

Relationship between free hemoglobin (hemolysis), potassium and ionized calcium in lithium heparin blood gas samples collected intraoperatively

OBJECTIVE

Develop sample acceptability rules by determining the relationship between free hemoglobin level (hemolysis) and potassium or ionized calcium in blood gas samples collected intraoperatively.

DESIGN AND METHODS

Hemolysis was assessed visually or by H index for lithium heparin blood gas samples collected intraoperatively. During periods one and three this was done using two different rules for visual assessment of centrifuged lithium heparin plasma. During period two H index was measured for all visually hemolyzed samples on a Roche Cobas c501 analyzer to determine acceptability. Potassium and ionized calcium were measured in 75 lithium heparin whole blood samples on a Radiometer ABL90 to correlate H index and potassium or ionized calcium.

RESULTS

During period one 35 of 5808 (0.6%) blood gas samples had visual hemolysis levels exceeding tolerance for reporting of potassium. By switching to measured H index using a laboratory-established threshold, during period 2 we estimate that 171 of 5396 (3.2%) blood gas samples exceeded the H index threshold for reporting of potassium. In 75 intraoperative blood gas samples with H index and whole blood potassium and ionized calcium measured; we observed no relationship between H index and potassium or ionized calcium. During period 3 we switched to visual assessment of hemolysis with a greater tolerance for hemolysis; with only 3 of 5345 (0.06%) samples exceeding the new visual hemolysis threshold.

CONCLUSION

For blood gas samples collected intraoperatively, there is no relationship between hemolysis and measured potassium or ionized calcium. The results suggest that only grossly hemolyzed intraoperative blood gas samples should be rejected for measurement of whole blood potassium and ionized calcium.

Hidden blood loss and its risk factors after hip hemiarthroplasty for displaced femoral neck fractures: a cross-sectional study

Purpose

Several authors have reported the degree of total blood loss (TBL) following hemiarthroplasty for displaced femoral neck fracture; however, the research specifically investigating on hidden blood loss (HBL) after hip hemiarthroplasty is still lacking. The purpose of this study is to evaluate the HBL in patients who underwent hip hemiarthroplasty for displaced femoral neck fractures and to analyze its risk factors.

Patients and methods

From January 2015 to December 2016, 212 patients (57 males and 155 females) with displaced femoral neck fracture undergoing hip hemiarthroplasty were included in this study. The demographic and relevant clinical information of the patients were collected. According to the Gross’s formula, each patient’s height, weight, and preoperative and postoperative hematocrit were recorded and used for calculating the total perioperative blood loss and HBL. Risk factors were further analyzed by multivariate linear regression.

Results

The HBL was 525±217 mL, with 61.0%±13.6% in the total perioperative blood loss (859±289 mL), and the perioperative hemoglobin (Hb) loss was 23.8±7.4 g/L. Multivariate linear regression analysis revealed that HBL was positively associated with higher American Society of Anesthesiologists (ASA) classification (regression coefficient=62.169, 95% CI=15.616–108.722; P=0.009), perioperative gastrointestinal bleeding/ulcer (regression coefficient=155.589, 95% CI=38.095–273.083; P=0.010), and transfusion (regression coefficient=192.118, 95% CI=135.578–248.659; P<0.001). Compared with females, males had a risk of increased HBL (regression coefficient=87.414, 95% CI=28.547–146.280; P=0.004), and general anesthesia had an increased HBL compared with spinal anesthesia (regression coefficient=68.920, 95% CI=11.707–126.134; P=0.018).

Conclusion

HBL should not be ignored in patients who underwent hip hemiarthroplasty for displaced femoral neck fractures in the perioperative period, because it is a significant portion of TBL. Female patients, patients with higher ASA classification and perioperative gastrointestinal bleeding/ulcer, patients who were administered general anesthesia, or patients who underwent transfusion had a greater amount of HBL after hip hemiarthroplasty was performed. Having a correct understanding of HBL may help surgeons improve clinical assessment capabilities and ensure patients’ safety.

Elevated free hemoglobin and decreased haptoglobin levels are associated with adverse clinical outcomes, unfavorable physiologic measures, and altered inflammatory markers in pediatric cardiac surgery patients

BACKGROUND

There are data suggesting that free hemoglobin (Hb), heme, and iron contribute to infection, thrombosis, multiorgan failure, and death in critically ill patients. These outcomes may be mitigated by haptoglobin.

STUDY DESIGN AND METHODS

164 consecutively treated children undergoing surgery for congenital heart disease were evaluated for associations between free Hb and haptoglobin and clinical outcomes, physiologic metrics, and biomarkers of inflammation RESULTS: Higher perioperative free Hb levels (and lower haptoglobin levels) were associated with mortality, nosocomial infection, thrombosis, hours of intubation and inotropes, increased interleukin-6, peak serum lactate levels, and lower nadir mean arterial pressures. The median free Hb in patients without infection (30 mg/dL; 29 interquartile range [IQR], 24-52 mg/dL) was lower than in those who became infected (39 mg/dL; IQR, 33-88 mg/ 31 dL; p = 0.0046). The median mechanical ventilation requirements were 19 (IQR, 7-72) hours in patients with higher levels of haptoglobin versus 48 (IQR, 18-144) hours in patients with lower levels (p = 0.0047). Transfusion dose, bypass duration, and complexity of surgery were all significantly correlated with Hb levels and haptoglobin levels. Multivariate analyses demonstrated that these variables were independently and significantly associated with outcomes.

CONCLUSIONS

Elevated pre- and postoperative levels of free Hb and decreased levels of haptoglobin were associated with adverse clinical outcomes, inflammation, and unfavorable physiologic metrics. Transfusion, RACHS score, and duration of bypass were associated with increased free Hb and decreased haptoglobin. Further investigation of the role of hemolysis and haptoglobin as potential mediators or markers of outcomes is warranted.

Pre-operative anaemia, intra-operative hepcidin concentration and acute kidney injury after cardiac surgery: a retrospective observational study

Acute kidney after cardiac surgery is more common in anaemic patients, whereas haemolysis during cardiopulmonary bypass may lead to iron-induced renal injury. Hepcidin promotes iron sequestration by macrophages: hepcidin concentration is reduced by anaemia and increased by inflammation. We analysed the associations in 525 patients between pre-operative anaemia (haemoglobin < 130 g.l^-1 in men and < 120 g.l^-1 in women), intra-operative hepcidin concentration and acute kidney injury (dialysis or > 26.4 μmol.l^-1 or > 50% creatinine increase during the first two days after cardiac surgery. Rates of pre-operative anaemia and postoperative kidney injury were 109/525 (21%) and 36/525 (7%), respectively. The median (IQR [range]) intra-operative hepcidin concentration was 20 (10-33 [0-125]) μg.l^-1 and was lower in anaemic patients than those who were not: 15 (4-28 [0-125]) μg.l^-1 vs. 21 (12-33 [0-125]) μg.l^-1 , respectively, p = 0.002. Four variables were independently associated with postoperative kidney injury, for which the beta-coefficients (SE) were: minutes on cardiopulmonary bypass, 0.016 (0.004), p < 0.001; intra-operative hepcidin concentration, 0.032 (0.008), p < 0.001; pre-operative anaemia, 1.97 (0.56), p < 0.001; and Cleveland clinic risk score, 0.88 (0.35), p = 0.005. Contrary to generally increased rates of kidney injury in patients with higher hepcidin concentrations, rates of kidney injury in anaemic patients were lower in patients with higher hepcidin concentrations, beta-coefficient (SE) -0.037 (0.01), p = 0.007. In cardiac surgical patients the rate of postoperative acute kidney injury predicted by the Cleveland risk score might be adjusted for pre-operative anaemia and intra-operative cardiopulmonary bypass time and hepcidin concentration. Pre-operative correction of anaemia, reduction in intra-operative bypass time and modification of iron homeostasis and hepcidin concentration might reduce acute kidney injury.