Safety and effectiveness of intracesarean blood salvage

A randomised controlled trial and economic evaluation of intraoperative cell salvage during caesarean section in women at risk of haemorrhage: the SALVO (cell SALVage in Obstetrics) trial

BACKGROUND

Caesarean section is associated with blood loss and maternal morbidity. Excessive blood loss requires transfusion of donor (allogeneic) blood, which is a finite resource. Cell salvage returns blood lost during surgery to the mother. It may avoid the need for donor blood transfusion, but reliable evidence of its effects is lacking.

OBJECTIVES

To determine if routine use of cell salvage during caesarean section in mothers at risk of haemorrhage reduces the rates of blood transfusion and postpartum maternal morbidity, and is cost-effective, in comparison with standard practice without routine salvage use.

DESIGN

Individually randomised controlled, multicentre trial with cost-effectiveness analysis. Treatment was not blinded.

SETTING

A total of 26 UK obstetric units.

PARTICIPANTS

Out of 3054 women recruited between June 2013 and April 2016, we randomly assigned 3028 women at risk of haemorrhage to cell salvage or routine care. Randomisation was stratified using random permuted blocks of variable sizes. Of these, 1672 had emergency and 1356 had elective caesareans. We excluded women for whom cell salvage or donor blood transfusion was contraindicated.

INTERVENTIONS

Cell salvage (intervention) versus routine care without salvage (control). In the intervention group, salvage was set up in 95.6% of the women and, of these, 50.8% had salvaged blood returned. In the control group, 3.9% had salvage deployed.

MAIN OUTCOME MEASURES

Primary - donor blood transfusion. Secondary - units of donor blood transfused, time to mobilisation, length of hospitalisation, mean fall in haemoglobin, fetomaternal haemorrhage (FMH) measured by Kleihauer-Betke test, and maternal fatigue. Analyses were adjusted for stratification factors and other factors that were believed to be prognostic a priori. Cost-effectiveness outcomes - costs of resources and service provision taking the UK NHS perspective.

RESULTS

We analysed 1498 and 1492 participants in the intervention and control groups, respectively. Overall, the transfusion rate was 2.5% in the intervention group and 3.5% in the control group [adjusted odds ratio (OR) 0.65, 95% confidence interval (CI) 0.42 to 1.01; p = 0.056]. In a planned subgroup analysis, the transfusion rate was 3.0% in the intervention group and 4.6% in the control group among emergency caesareans (adjusted OR 0.58, 95% CI 0.34 to 0.99), whereas it was 1.8% in the intervention group and 2.2% in the control group among elective caesareans (adjusted OR 0.83, 95% CI 0.38 to 1.83) (interaction p = 0.46, suggesting that the difference in effect between subgroups was not statistically significant). Secondary outcomes did not differ between groups, except for FMH, which was higher under salvage in rhesus D (RhD)-negative women with RhD-positive babies (25.6% vs. 10.5%, adjusted OR 5.63, 95% CI 1.43 to 22.14; p = 0.013). No case of amniotic fluid embolism was observed. The additional cost of routine cell salvage during caesarean was estimated, on average, at £8110 per donor blood transfusion avoided.

CONCLUSIONS

The modest evidence for an effect of routine use of cell salvage during caesarean section on rates of donor blood transfusion was associated with increased FMH, which emphasises the need for adherence to guidance on anti-D prophylaxis. We are unable to comment on long-term antibody sensitisation effects. Based on the findings of this trial, cell salvage is unlikely to be considered cost-effective.

FUTURE WORK

Research into risk of alloimmunisation among women exposed to cell salvage is needed.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN66118656.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 22, No. 2. See the NIHR Journals Library website for further project information.

Does current evidence support the use of intraoperative cell salvage in reducing the need for blood transfusion in caesarean section?

PURPOSE OF REVIEW

An important cause of maternal morbidity and direct maternal death is obstetric haemorrhage at caesarean section. Concerns regarding allogeneic blood safety, limited blood supplies and rising health costs have collectively generated enthusiasm for the utility of methods intended to reduce the use of allogeneic blood transfusion in cases of haemorrhage at caesarean section. This can be achieved by intraoperative cell salvage (IOCS). The aim of this review is to summarize and examine the evidence for the efficacy of IOCS during caesarean section, in women at risk of haemorrhage, in reducing the need for allogeneic blood transfusion.

RECENT FINDINGS

The majority of the evidence currently available is from case reports and case series. Although this evidence appears to support the use of IOCS in obstetrics, strong clinical evidence or economic effectiveness from clinical trials are essential to support the routine practice of IOCS in obstetrics.

SUMMARY

Current evidence is limited to reported case series and two small controlled studies. Overall, IOCS may reduce the need for allogeneic blood transfusions during caesarean section. Future large randomized trials are required to assess effectiveness, cost effectiveness and safety. The results of the current ongoing SALVO (A randomised controlled trial of intra-operative cell salvage during caesarean section in women at risk of haemorrhage) trial will shed light on these aspects.

Cost savings of red cell salvage during cesarean delivery

OBJECTIVE

To use decision analysis to evaluate whether and under what conditions routine setup of intraoperative cell salvage during cesarean delivery is cost-saving.

METHODS

We developed a decision model to compare costs associated with two strategies for cesarean delivery: 1) routine setup of intraoperative cell salvage; or 2) standard care without intraoperative cell salvage. One-, two-, and three-way sensitivity analyses as well as Monte Carlo simulation were used to assess the robustness of our findings.

RESULTS

Among nonselected women undergoing cesarean delivery, our base case estimate was that 3.2% would require red blood cell transfusion. Under this assumption, cell salvage is cost-saving only if each woman requires at least 60 units. Conversely, if only two units on average are required, the probability of transfusion needs to be at least 58% for cell salvage to be cost-saving. In our base case analysis, setup of intraoperative cell salvage during routine cesarean deliveries is not cost-saving, increasing the cost per cesarean delivery by $223.80. We found that cell salvage would be cost-saving only in very high-risk scenarios. For example, severe maternal anemia or abnormal placentation, in which 54% and 75% of women are transfused three and two units per case, respectively, would make cell salvage cost-saving.

CONCLUSION

Setup of intraoperative cell salvage during cesarean delivery is cost-saving and should be considered only when there is a predictably high probability of transfusion or when a massive transfusion is reasonably likely.

Intraoperative cell salvage in obstetrics

The use of Intraoperative Cell Salvage (ICS) in obstetrics has been slow to develop as a result of theoretical concerns relating to amniotic fluid embolism and fetal red cell contamination. In this article we examine the current UK position on the use of ICS in this clinical speciality and the recommendations for its safe and appropriate use.

The introduction of intra-operative cell salvage in obstetric clinical practice: a review of the available evidence

Intra-operative blood salvage is common practice in many surgical specialties but its safety is questioned with concerns about the risks of contamination of recovered blood with amniotic fluid and of maternal-foetal alloimmunization. However, the role of cell salvage as a blood-saving measure in this clinical setting is progressively acquiring relevance thanks to the growing body of evidence regarding its quality and safety. Modern cell savers remove most particulate contaminants and leukodepletion filtering of salvaged blood prior to transfusion adds further safety to this technique. Amniotic fluid embolism is no longer regarded as an embolic disease and the contamination of the salvaged blood by foetal Rh-mismatched red blood cells can be dealt with using anti-D immunoglobulin; ABO incompatibility tends to be a minor problem since ABO antigens are not fully developed at birth. Maternal alloimmunization can be caused also by other foetal red cell antigens, but it should also be noted that the risk of alloimmunization of the mother from allogeneic transfusion may be even greater. Therefore the use of cell savers in obstetric clinical practice should be considered in patients at high risk for haemorrhage or in cases where allogeneic blood transfusion is difficult or impossible.

Maternal morbidity, mortality, and risk assessment

Maternal deaths in developed countries continue to decline and are rare. Maternal mortality statistics are essentially similar in the United States and United Kingdom. However, the situation is completely different in developing countries, where maternal mortality exceeds 0.5 million every year. This article not only assesses morbidity risks in some of the leading causes of maternal death but also highlights strategies to minimize the risks and to prevent maternal morbidity and mortality.

Cell salvage in obstetrics

The safety of cell salvage in obstetrics has been questioned because of the presumed risk of precipitating amniotic fluid embolism and, to a lesser extent, maternal alloimmunisation. For these reasons, experience in this field is limited and has lagged far behind that in other surgical specialties. There has, however, been renewed interest in its use over recent years, mainly as a result of problems associated with allogeneic blood transfusion. Our aim was to review the medical literature to ascertain the principles of cell salvage, the ability of the process to remove contaminants, and its safety profile in the obstetric setting. The search engines PubMed and Google Scholar were used and relevant articles and websites hand searched for further references. Existing cell salvage systems differ in their ability to clear contaminants and all require the addition of a leucocyte depletion filter. Although large prospective trials of cell salvage with autotransfusion in obstetrics are lacking, to date, no single serious complication leading to poor maternal outcome has been directly attributed to its use. Cell salvage in obstetrics has been endorsed by several bodies based on current evidence. Current evidence supports the use of cell salvage in obstetrics, which is likely to become increasingly commonplace, but more data are required concerning its clinical use.

Intraoperative cell salvage in obstetrics

Cell salvage is widely used in many surgical specialties to reduce the use of allogeneic blood, which is associated with well-recognized significant complications such as incorrect transfusion, acute and delayed immunological transfusion reactions and transfusion-transmitted infection. Theoretical concerns over the use of cell salvage in obstetrics have focused on the risk of Rhesus immunization and the risk of contamination of the cell-saved blood with traces of amniotic fluid. This article examines the in vitro and in vivo evidence for the safety of the technique, presents current usage figures from Wales and the entire UK, and discusses the current perception of amniotic fluid embolus as an anaphylactoid reaction. It suggests that patients will have to choose between the risks of allogeneic or cell-saved blood, and concludes that the balance of evidence is now in favour of cell salvage in obstetrics.

Blood conservation techniques in obstetrics: a UK perspective

In the UK, maternal mortality due to haemorrhage appears to be rising, with obstetric haemorrhage accounting for 3-4% of the red cells transfused. Allogeneic blood transfusion carries risks such as administration errors, transmitted infections and immunological reactions. The supply of blood is decreasing, partly due to the exclusion of donors who have themselves received a blood transfusion since 1980, in order to stop transmission of variant-Creutzfeldt-Jakob disease. The cost of blood is significantly increasing, partly because it is now leucocyte-depleted to minimize viral transmission. Various blood conservation techniques can reduce exposure to allogeneic blood thereby reducing risk and conserving the blood supply. These include preoperative autologous donation, acute normovolaemic haemodilution and intra-operative cell salvage. Preoperative autologous donation may produce anaemia, does not eliminate transfusion risk, cannot be used in an emergency and is not acceptable to Jehovah's Witnesses. It should be reserved for exceptional circumstances (rare blood type or unusual antibodies). Acute normovolaemic haemodilution may induce anaemia and cardiac failure and cannot be used in an emergency. It may have a limited role in combination with other techniques. Intra-operative cell salvage is more effective and useful in obstetrics than the other techniques, overcomes their shortcomings and is endorsed by CEMACH, OAA/AAGBI Guidelines, the National Blood Service and NICE.

An Analysis of Transfusion Practice and the Role of Intraoperative Red Blood Cell Salvage During Cesarean Delivery

BACKGROUND

We sought to determine to what extent intraoperative salvaged red blood cells (RBC) might theoretically reduce exposure to appropriately transfused allogenic erythrocytes in Cesarean delivery patients.

METHODS

Medical records of Cesarean delivery patients requiring blood transfusions from January 1, 1992 to June 30, 1996 and June 1, 1998 to June 30, 2003 were reviewed. For each patient, we calculated the number of allogenic RBC units that could have theoretically been avoided had intraoperative autotransfusion been performed, based upon estimated blood loss, preoperative hematocrit, and the amount of retrieved blood needed to yield a single RBC unit. RBC transfusion appropriateness was determined using the recommended guideline of transfusing RBCs if the hemoglobin is <7 gm/dL in a patient with continuing bleeding.

RESULTS

A small percentage of Cesarean delivery patients (1.8%) received blood product transfusions. Of 207 patients receiving blood transfusions, salvaged erythrocytes could have theoretically decreased exposure to allogenic RBCs in 115 (55.6%) patients. Only 75.7% of these 115 patients were appropriately transfused with erythrocytes.

CONCLUSION

Theoretically, based on best, average, and worst RBC salvage recovery calculations, 25.1%, 21.2%, or 14.5% of the appropriately transfused patients, respectively, could have completely avoided allogenic RBC transfusion.

Planning for hemorrhage. Steps an anesthesiologist can take to limit and treat hemorrhage in the obstetric patient

Obstetric hemorrhage continues to be a significant cause of maternal mortality and morbidity. Blood transfusion in such circumstances may be life saving but involves exposing the patient to additional risks. Limiting blood transfusion and using autologous blood when possible may reduce some of these risks. This article outlines the techniques that may be used to limit and more effectively treat hemorrhage in the obstetric patient, with particular attention paid to reducing the use of allogeneic blood transfusion.

Clinical experience with cell salvage in obstetrics: 4 cases from one UK centre

We present 4 cases in which cell salvaged blood was used in maternity patients, including three caesarean sections and one post-partum haemorrhage. All patients were monitored for a minimum of 24 h on either a general Intensive Care Unit (ICU) or specialised obstetric High Dependency Unit (HDU). Postoperative complications are discussed, with particular emphasis on whether the transfusion of cell salvaged blood was a contributory factor. Cell salvage in obstetrics is being used in a haphazard and individual manner and our only present outcome indicators are case reports. We consider the argument for and against cell salvage in obstetrics, and suggest guidelines to reflect current best practice in the use of the machine and filters.

Cell salvage in obstetrics: an evaluation of the ability of cell salvage combined with leucocyte depletion filtration to remove amniotic fluid from operative blood loss at caesarean section

During 27 elective caesarean sections, operative blood loss was collected and processed using the Haemonetics Cell Saver 5 and filtered by Pall RC 100 leucocyte depletion filtration. The efficiency of removal of amniotic fluid, and the degree. of contamination with fetal red cells were assessed in the resulting 'cleaned' blood. Cell saver processing effectively removed alpha-fetoprotein from the red cells of 14 patients whose amniotic fluid was removed by separate suction and from nine of the 13 patients whose amniotic fluid was aspirated into the cell saver along with operative blood loss. Cell saver processing and leucocyte depletion filtration completely removed trophoblastic tissue and white cells, but fetal squames were still clearly present in 10, and possibly in 14 samples after processing and fully removed in only two specimens. Amorphous debris was present in all samples after processing. The maximum mass of fetal red cells contaminating any patient's total salvaged blood was 19 ml (range 2-19 ml). Had this been re-transfused into a rhesus-incompatible mother it would have required 2500 i.u. (500 microg) anti-D immunoglobulin to prevent rhesus-immunization of the mother. Contamination of processed caesarean section blood with fetal red cells and fetal squames is defined and its clinical implications discussed, with an overview of the development and current status of cell salvage. Autotransfusion by cell salvage with leucocyte depletion filtration should be considered in life-threatening obstetric haemorrhage and offered to Jehovah's Witnesses.

The safety of intraoperative autologous blood collection and autotransfusion during cesarean section

OBJECTIVE

We evaluated the safety of intraoperative autologous blood collection and autotransfusion during cesarean section.

STUDY DESIGN

A multicenter historical cohort study identified 139 patients in whom autologous blood collection autotransfusion during cesarean section was performed. We also identified 87 control patients who underwent similar surgical procedures at the same centers without autotransfusion. The outcome variables we compared were acute respiratory distress syndrome, amniotic fluid embolism, disseminated intravascular coagulation, need for ventilatory support, infectious morbidity, and the length of postpartum hospitalization.

RESULTS

Demographic and obstetric characteristics were similar in both groups. The ranges of autotransfused volumes were 200 to 11,250 mL at Yale, 225 to 1160 mL at Good Samaritan, and 125 to 4750 mL at Hinsdale. No statistically significant differences existed between the two groups in any of the outcome variables analyzed. No case of acute respiratory distress syndrome or amniotic fluid embolism was identified in either group.

CONCLUSIONS

Our multicenter experience reveals no demonstrably increased risk of complications in patients receiving autologous blood collection autotransfusion during cesarean section.

[Evaluation of the blood quality collected by cell-saver during cesarean section]

OBJECTIVE

To determine the quality of blood salvaged and processed during Caesarean section with a cell-saver.

STUDY DESIGN

Laboratory study.

PATIENTS

The study included 20 patients of ASA physical class 1 or 2 undergoing a scheduled Caesarean section.

METHODS

A separate suction device was used from the beginning surgery until the delivery of the fetus, to remove most of the amniotic fluid coming from the surgical field. Thereafter using an Haemolite 2Plus (Haemonetics), the blood was separated and washed with 2 L of normal saline solution. Blood quality was assessed through detection of fetal cells and measuring out of alpha-fetal-protein, tissue factor. A Kleihauer test was also performed.

RESULTS

Cell-saver processing removed most of alpha-fetal-protein and tissue factor while fetal cells were rarely seen. The Kleihauer test could not be performed because of haemolized blood samples. However, the results were very heterogeneous and after washing some salvaged units contained very high concentrations of alpha-fetal-protein or tissue factor.

CONCLUSIONS

These preliminary results show that intra-operative autologous transfusion is not fully safe during Caesarean sections. In addition, there is an immunological risk if a significant part of fetal red blood cells are reinfused into maternal circulation. Therefore, additional studies are needed to better assess this risk.

The use of acute hemodilution in parturients undergoing cesarean section

OBJECTIVE

Concern over transmissible disease has increased interest in methods of minimizing homologous blood transfusion during elective surgery. One method is acute hemodilution, a technique previously unreported in parturients. This study was designed to determine its feasibility and safety in women at risk of hemorrhage during cesarean section.

STUDY DESIGN

This technique was performed on 38 parturients. Collected blood was retransfused at the end of surgery or earlier, if required. Hemoglobin was measured before hemodilution, after hemodilution, before transfusion, after transfusion, and 24 hours postoperatively. Neonatal assessment included umbilical blood gases and Apgar scores.

RESULTS

All patients were hemodynamically stable and no fetal heart rate abnormalities were observed during the procedure. One patient received homologous blood and 14 received previously donated autologous blood. Umbilical blood gases were normal and 5-minute Apgar scores were > or = 7.

CONCLUSION

This study suggests that acute hemodilution is well tolerated in parturients undergoing cesarean section. This may limit exposure to homologous blood transfusion.

Perioperative interventions to decrease transfusion of allogeneic blood products

OBJECTIVE

To discuss some of the many options available for decreasing perioperative transfusion of allogeneic blood products.

DESIGN

We review the issues that focus on the goal of developing an appropriate transfusion strategy in consideration of the individual patient's preexisting conditions, physiologic requirements, perioperative stress, and coagulation status.

RESULTS

Increased awareness of transfusion-related morbidity from allogeneic blood products has resulted in increased development and application of alternatives to allogeneic transfusion. Preoperative donation and perioperative collection of autologous blood and blood products decrease exposure to allogeneic blood. Pharmacologic agents, such as antifibrinolytics, may also decrease the need for allogeneic transfusion. Perioperative use of laboratory tests of coagulation function facilitates the rapid and specific diagnosis of coagulation disorders.

CONCLUSION

Physicians now have considerable appreciation of the risks and benefits of blood product transfusion. This knowledge has resulted in conservative and scientific approaches to therapy for perioperative bleeding and coagulopathy.

Transfusion and surgery

In this survey of transfusion in surgery, we have attempted to provide the surgeon with an understanding of the problems associated with homologous transfusion and a practical knowledge of treatment strategies and alternatives designed to reduce homologous blood exposure. Such a review cannot be encyclopedic. Our hope is that it will serve the reader as a stimulus to examine his or her transfusion practices and as a guide for future self-learning.