Retransfusion of cardiotomy suction blood impairs haemostasis: Ex vivo and in vivo studies

Cell salvage for minimising perioperative allogeneic blood transfusion in adults undergoing elective surgery

BACKGROUND

Concerns regarding the safety and availability of transfused donor blood have prompted research into a range of techniques to minimise allogeneic transfusion requirements. Cell salvage (CS) describes the recovery of blood from the surgical field, either during or after surgery, for reinfusion back to the patient.

OBJECTIVES

To examine the effectiveness of CS in minimising perioperative allogeneic red blood cell transfusion and on other clinical outcomes in adults undergoing elective or non-urgent surgery.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, three other databases and two clinical trials registers for randomised controlled trials (RCTs) and systematic reviews from 2009 (date of previous search) to 19 January 2023, without restrictions on language or publication status.

SELECTION CRITERIA

We included RCTs assessing the use of CS compared to no CS in adults (participants aged 18 or over, or using the study's definition of adult) undergoing elective (non-urgent) surgery only.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included 106 RCTs, incorporating data from 14,528 participants, reported in studies conducted in 24 countries. Results were published between 1978 and 2021. We analysed all data according to a single comparison: CS versus no CS. We separated analyses by type of surgery. The certainty of the evidence varied from very low certainty to high certainty. Reasons for downgrading the certainty included imprecision (small sample sizes below the optimal information size required to detect a difference, and wide confidence intervals), inconsistency (high statistical heterogeneity), and risk of bias (high risk from domains including sequence generation, blinding, and baseline imbalances). Aggregate analysis (all surgeries combined: primary outcome only) Very low-certainty evidence means we are uncertain if there is a reduction in the risk of allogeneic transfusion with CS (risk ratio (RR) 0.65, 95% confidence interval (CI) 0.59 to 0.72; 82 RCTs, 12,520 participants). Cancer: 2 RCTs (79 participants) Very low-certainty evidence means we are uncertain whether there is a difference for mortality, blood loss, infection, or deep vein thrombosis (DVT). There were no analysable data reported for the remaining outcomes. Cardiovascular (vascular): 6 RCTs (384 participants) Very low- to low-certainty evidence means we are uncertain whether there is a difference for most outcomes. No data were reported for major adverse cardiovascular events (MACE). Cardiovascular (no bypass): 6 RCTs (372 participants) Moderate-certainty evidence suggests there is probably a reduction in risk of allogeneic transfusion with CS (RR 0.82, 95% CI 0.69 to 0.97; 3 RCTs, 169 participants). Very low- to low-certainty evidence means we are uncertain whether there is a difference for volume transfused, blood loss, mortality, re-operation for bleeding, infection, wound complication, myocardial infarction (MI), stroke, and hospital length of stay (LOS). There were no analysable data reported for thrombosis, DVT, pulmonary embolism (PE), and MACE. Cardiovascular (with bypass): 29 RCTs (2936 participants) Low-certainty evidence suggests there may be a reduction in the risk of allogeneic transfusion with CS, and suggests there may be no difference in risk of infection and hospital LOS. Very low- to moderate-certainty evidence means we are uncertain whether there is a reduction in volume transfused because of CS, or if there is any difference for mortality, blood loss, re-operation for bleeding, wound complication, thrombosis, DVT, PE, MACE, and MI, and probably no difference in risk of stroke. Obstetrics: 1 RCT (1356 participants) High-certainty evidence shows there is no difference between groups for mean volume of allogeneic blood transfused (mean difference (MD) -0.02 units, 95% CI -0.08 to 0.04; 1 RCT, 1349 participants). Low-certainty evidence suggests there may be no difference for risk of allogeneic transfusion. There were no analysable data reported for the remaining outcomes. Orthopaedic (hip only): 17 RCTs (2055 participants) Very low-certainty evidence means we are uncertain if CS reduces the risk of allogeneic transfusion, and the volume transfused, or if there is any difference between groups for mortality, blood loss, re-operation for bleeding, infection, wound complication, prosthetic joint infection (PJI), thrombosis, DVT, PE, stroke, and hospital LOS. There were no analysable data reported for MACE and MI. Orthopaedic (knee only): 26 RCTs (2568 participants) Very low- to low-certainty evidence means we are uncertain if CS reduces the risk of allogeneic transfusion, and the volume transfused, and whether there is a difference for blood loss, re-operation for bleeding, infection, wound complication, PJI, DVT, PE, MI, MACE, stroke, and hospital LOS. There were no analysable data reported for mortality and thrombosis. Orthopaedic (spine only): 6 RCTs (404 participants) Moderate-certainty evidence suggests there is probably a reduction in the need for allogeneic transfusion with CS (RR 0.44, 95% CI 0.31 to 0.63; 3 RCTs, 194 participants). Very low- to moderate-certainty evidence suggests there may be no difference for volume transfused, blood loss, infection, wound complication, and PE. There were no analysable data reported for mortality, re-operation for bleeding, PJI, thrombosis, DVT, MACE, MI, stroke, and hospital LOS. Orthopaedic (mixed): 14 RCTs (4374 participants) Very low- to low-certainty evidence means we are uncertain if there is a reduction in the need for allogeneic transfusion with CS, or if there is any difference between groups for volume transfused, mortality, blood loss, infection, wound complication, PJI, thrombosis, DVT, MI, and hospital LOS. There were no analysable data reported for re-operation for bleeding, MACE, and stroke.

AUTHORS' CONCLUSIONS

In some types of elective surgery, cell salvage may reduce the need for and volume of allogeneic transfusion, alongside evidence of no difference in adverse events, when compared to no cell salvage. Further research is required to establish why other surgeries show no benefit from CS, through further analysis of the current evidence. More large RCTs in under-reported specialities are needed to expand the evidence base for exploring the impact of CS.

High summation of preoperative and postoperative Interleukin-6 levels predicts prolonged mechanical ventilation in patients with acute DeBakey type I aortic dissection: A single center retrospective study

Objective

This study aimed to investigate the predictive effect of preoperative and postoperative interleukin-6 (IL-6) levels on the duration of mechanical ventilation in patients with acute DeBakey Type I aortic dissection (I-AAD) after emergency surgery.

Methods

We retrospectively enrolled 381 patients with I-AAD who underwent surgery in our hospital, between June 2018 and June 2022. Patients were divided into two groups according to whether prolonged mechanical ventilation (PMV) occurred after surgery. The baseline data, biochemical indicators at admission, surgical data, biochemical indicators at postoperative 6 h, and the postoperative data of the two groups were recorded and analyzed.

Results

The PMV group comprised 199 patients, and the non-PMV group 182. The postoperative in-hospital mortality was different between the two groups (11.1% vs. 3.3%, p = 0.004). The length of intensive care unit and hospitalization time in the PMV group were significantly longer than those in the non-PMV group. Multiple regression analysis showed postoperative IL-6 (post-IL-6) ≥67.1 pg/mL and summation of preoperative and postoperative IL-6 (total IL-6) ≥83.4 pg/mL were associated risk factors for PMV [odds ratio (OR) 3.259, 95% confidence interval (CI) 1.922-5.524, p < 0.001], [(OR) 4.515, 95% CI 2.241-9.098, p < 0.001]. Furthermore, determined by the receiver operating characteristics(ROC) curve, the cut-off point was total IL-6 ≥83.4 pg/mL (area under curve(AUC) = 0.825). The sensitivity and specificity of predicting postoperative PMV of patients with I-AAD were 91.5% and 78.2%, respectively (95% CI 0.782-0.868, p < 0.001).

Conclusion

For predicting postoperative PMV in patients with I-AAD, post IL-6 ≥67.1 pg/mL is potentially valuable and summation of preoperative and postoperative IL-6 (total IL-6) ≥83.4 pg/mL has a more pronounced predictive value.

Fibrinogen and Bleeding in Adult Cardiac Surgery: A Review of the Literature

Background: Fibrinogen is a substrate for blood clots formation. In cardiac surgery, a number of different mechanisms lead to a decrease in fibrinogen levels and consequent impaired haemostasis. Patients undergoing cardiac surgery are therefore frequently exposed to blood loss and allogeneic blood transfusion, which are risk factors associated with morbidity and mortality. Thus, particular efforts in fibrinogen management should be made to decrease bleeding and the need for blood transfusion. Therefore, fibrinogen remains an active focus of investigations from basic science to clinical practice. This review aims to summarise the latest evidence regarding the role of fibrinogen and current practices in fibrinogen management in adult cardiac surgery. Methods: The PubMed database was systematically searched for literature investigating the role and disorders of fibrinogen in cardiac surgery and diagnostic and therapeutic procedures related to fibrinogen deficiency aimed at reducing blood loss and transfusion requirements. Clinical trials and reviews from the last 10 years were included. Results: In total, 146 articles were analysed. Conclusion: The early diagnosis and treatment of fibrinogen deficiency is crucial in maintaining haemostasis in bleeding patients. Further studies are needed to better understand the association between fibrinogen levels, bleeding, and fibrinogen supplementation and their impacts on patient outcomes in different clinical settings.

Adult cardiopulmonary bypass in Australian and New Zealand public hospitals: A survey of practice

A telephone survey of cardiac anaesthetists and perfusionists at the 29 public hospitals providing adult cardiac surgical services in Australia and New Zealand was carried out between December 2019 and January 2020. The aim was to investigate current practice with regard to selected contentious elements of anaesthetic and perfusion management during cardiopulmonary bypass; primarily relating to bypass circuit priming, blood conservation methods and point-of-care coagulation testing. There was a 100% response rate. The average number of adult public cardiopulmonary bypass cases per hospital was 508 (160-1400). For cardiopulmonary bypass cases, ten hospitals (34%) routinely used a cell saver and the remainder used a cell saver selectively. Residual blood remaining in the cardiopulmonary bypass circuit was processed using a cell saver routinely in four hospitals (14%) and selectively in 23 (79%). Acute normovolaemic haemodilution was rarely used. Retrograde autologous priming was used routinely in seven hospitals (24%) and selectively in 16 (55%). All hospitals had access to point-of-care coagulation testing. The majority of hospitals targeted an activated clotting time of 480 s (range 400-500 s) prior to commencing cardiopulmonary bypass. There was marked geographic variation in access to fibrinogen concentrate. The cardiopulmonary bypass circuit prime solution was primarily a balanced crystalloid in most hospitals; however, there was significant variation regarding the addition of human albumin, mannitol, sodium bicarbonate and other medications. Many of the interventions examined were used on a case-by-case basis. These findings support the need for further research to define more evidence-based practice of these interventions.

The effect of a novel turbulence-controlled suction system in the prevention of hemolysis and platelet dysfunction in autologous surgery blood

Background:

Re-transfusion of autologous blood is an important aspect of intraoperative blood management. Hemolysis and platelet dysfunction due to turbulence in the blood suction system strongly impede later usage of suction blood for re-transfusion. The aim of this study was to analyze the effects of a novel surgical-blood suction system with an automatic control setup for minimization of turbulence in the blood flow.

Methods:

We compared the turbulence-controlled suction system (TCSS) with a conventional suction system and untreated control blood in vitro. Blood cell counts, hemolysis levels according to free hemoglobin (fHb) and platelet function were analyzed to determine the integrity of the suction blood.

Results:

In the conventional suction system, we found a strong increase of the fHb levels. In contrast, erythrocyte integrity was almost completely preserved when using the TCSS. We obtained similar results regarding platelet function. The expression of platelet glycoproteins, such as GP IIb/IIIa and P-selectin, native or after stimulation with ADP, were markedly impaired by the conventional system, but not by the TCSS. In addition, platelet aggregometry revealed significant platelet dysfunction in conventional suction blood, but less aggregation impairments were present in blood samples from the TCSS.

Conclusion:

Our findings on an in vitro assessment show major improvements in red blood cell integrity and platelet function of suction blood when using the TCSS compared to a conventional suction system. These results reflect a significant benefit for autologous re-transfusion. We suggest testing the TCSS in surgery for clinical evaluation.

Improving hemolysis levels associated with cardiotomy suction

BACKGROUND

The major source of hemolysis during cardiopulmonary bypass (CPB) remains the cardiotomy suction.¹ Previous research has shown that the combination of negative pressures and the massive air-blood interface exponentially increases hemolysis in suctioned blood.

OBJECTIVE

This research aims to decrease hemolysis by eliminating the air-to-blood interface by implementing the Venturi effect to create powerful suction. This research effort hypothesizes that the Venturi suction will result in less hemolysis, indicated by lower plasma free hemoglobin levels (PFH) compared to current vacuum suction.

METHOD

The research hypothesizes that a paradigm approach to cardiotomy suction that utilizes the Venturi effect with shorter tubing lengths and weighted sucker tips will further reduce hemolysis.

RESULTS

The vacuum-suctioned blood showed PFH levels significantly increased from baseline levels (p=0.0039). Neither the Venturi nor paradigm groups showed PFH levels significantly increased from baseline levels (p=0.0625 and p=0.125, respectively). There was a significant difference in PFH levels among the three conditions (p<0.0001). The vacuum condition showed significantly higher levels of PFH compared to both the Venturi and the paradigm conditions (p<0.001 for both). There was no significant difference in the PFH levels between the Venturi and the paradigm groups (p=1.00).

CONCLUSION

This study concludes that vacuum suction causes excessive hemolysis. A Venturi-powered suction system does not cause hemolysis and can be employed to reduce the damaging effects of vacuum suction on blood.

Cell saver processing mitigates the negative effects of wound blood on platelet function

BACKGROUND

Wound blood is highly activated and has poor haemostatic properties. Recent data suggest that retransfusion of unwashed wound blood may impair haemostasis. We hypothesized that cell saver processing of wound blood before retransfusion reduces the negative effects.

METHODS

Wound blood was collected from 16 cardiac surgery patients during cardiopulmonary bypass. One portion of the wound blood was processed in a cell saver and one portion left unprocessed. Increasing amounts of unprocessed blood (10% and 20% of the systemic blood volume) or corresponding volumes of processed blood were added ex vivo to whole blood samples from the same patient. Clot formation was assessed by modified thromboelastometry (ROTEM(®) ) and platelet function with impedance aggregometry (Multiplate(®) ).

RESULTS

Addition of unprocessed wound blood significantly impaired clot formation and platelet aggregability. Cell saver processing before addition did not influence clot formation but abolished completely the negative effects of wound blood on platelet aggregability tested with all agonists. Median adenosine diphosphate-induced platelet aggregation was 51 (25th and 75th percentiles 42-69) when 20% processed cardiotomy suction blood was added vs. 34 (24-52) U when 20% unprocessed blood was added, P < 0.001. The corresponding figures for arachidonic acid-, thrombin receptor activating peptide- and collagen-induced aggregation was 21 (17-51) vs. 13 (10-25) U, 112 (87-128) vs. 78 (65-103) U and 58 (50-73) vs. 33 (28-44) U, respectively, all P < 0.001).

CONCLUSION

The results suggest that cell saver processing before retransfusion mitigates the negative effects of wound blood on platelet function despite that cell saver processing reduces platelet count.