Modification of Suction-Induced Hemolysis During Cell Salvage

Application of an autotransfusion pressure control system in blood salvage

OBJECTIVE

This study was performed to evaluate the effect of a homemade autotransfusion pressure-control system on the regulation of negative pressure and to clarify the influence of different negative pressures on the recovered erythrocytes.

METHODS

Fifty patients were randomly divided into five groups, and five different suction-generated negative pressures were applied. Before suction, 6 mL of blood was collected from the surgical field; after suction, 6 mL of blood was collected from the blood storage tank. The hemoglobin, hematocrit, mean corpuscular volume, newly generated standardized plasma free hemoglobin, and change in the hemolysis rate of erythrocytes before and after suction were compared. Additionally, the erythrocyte morphology was observed.

RESULTS

The hemoglobin and hematocrit were significantly different before and after suction in all five groups. As the suction pressure increased, gradual increases were noted in the number of abnormal erythrocytes in the field of view, the newly generated standardized plasma free hemoglobin, and the change in the hemolysis rate.

CONCLUSIONS

The destruction rate of erythrocytes increased as the suction-generated negative pressure increased. When using a pressure-control system, a negative pressure of <200 mmHg should be applied to reduce the damage to the autotransfused blood.

Self-anticoagulant sponge for whole blood auto-transfusion and its mechanism of coagulation factor inactivation

Clinical use of intraoperative auto-transfusion requires the removal of platelets and plasma proteins due to pump-based suction and water-soluble anticoagulant administration, which causes dilutional coagulopathy. Herein, we develop a carboxylated and sulfonated heparin-mimetic polymer-modified sponge with spontaneous blood adsorption and instantaneous anticoagulation. We find that intrinsic coagulation factors, especially XI, are inactivated by adsorption to the sponge surface, while inactivation of thrombin in the sponge-treated plasma effectively inhibits the common coagulation pathway. We show whole blood auto-transfusion in trauma-induced hemorrhage, benefiting from the multiple inhibitory effects of the sponge on coagulation enzymes and calcium depletion. We demonstrate that the transfusion of collected blood favors faster recovery of hemostasis compared to traditional heparinized blood in a rabbit model. Our work not only develops a safe and convenient approach for whole blood auto-transfusion, but also provides the mechanism of action of self-anticoagulant heparin-mimetic polymer-modified surfaces.

Turbulence in surgical suction heads as detected by MRI

BACKGROUND

Blood loss is common during surgical procedures, especially in open cardiac surgery. Allogenic blood transfusion is associated with increased morbidity and mortality. Blood conservation programs in cardiac surgery recommend re-transfusion of shed blood directly or after processing, as this decreases transfusion rates of allogenic blood. But aspiration of blood from the wound area is often associated with increased hemolysis, due to flow induced forces, mainly through development of turbulence.

METHODS

We evaluated magnetic resonance imaging (MRI) as a qualitative tool for detection of turbulence. MRI is sensitive to flow; this study uses velocity-compensated T1-weighted 3D MRI for turbulence detection in four geometrically different cardiotomy suction heads under comparable flow conditions (0-1250 mL/min).

RESULTS

Our standard control suction head Model A showed pronounced signs of turbulence at all flow rates measured, while turbulence was only detectable in our modified Models 1-3 at higher flow rates (Models 1 and 3) or not at all (Model 2).

CONCLUSIONS

The comparison of flow performance of surgical suction heads with different geometries via acceleration-sensitized 3D MRI revealed significant differences in turbulence development between our standard control Model A and the modified alternatives (Models 1-3). As flow conditions during measurement have been comparable, the specific geometry of the respective suction heads must have been the main factor responsible. The underlying mechanisms and causative factors can only be speculated about, but as other investigations have shown, hemolytic activity is positively associated with degree of turbulence. The turbulence data measured in this study correlate with data from other investigations about hemolysis induced by surgical suction heads. The experimental MRI technique used showed added value for further elucidating the underlying physical phenomena causing blood damage due to non-physiological flow.

Cell Salvage in Oncological Surgery, Peripartum Haemorrhage and Trauma

Oncological surgery, obstetric haemorrhage and severe trauma are the most challenging conditions for establishing clinical recommendations for the use of cell salvage. When the likelihood of allogeneic transfusion is high, the intraoperative use of this blood-saving technique would be justified, but specific patient selection criteria are needed. The main concerns in the case of oncological surgery are the reinfusion of tumour cells, thereby increasing the risk of metastasis. This threat could be minimized, which may help to rationalize its indication. In severe peripartum haemorrhage, cell salvage has not proven cost-effective, damage control techniques have been developed, and, given the risk of fetomaternal alloimmunization and amniotic fluid embolism, it is increasingly out of use. In trauma, bleeding may originate from multiple sites, coagulopathy may develop, and it should be evaluated whether re-transfusion of autologous blood collected from uncontaminated organ cavities would be feasible. General safety measures include washing recovered blood and its passage through leukocyte depletion filters. To date, no well-defined indications for cell salvage have been established for these pathologies, but with accurate case selection and selective implementation, it could become safe and effective. Randomized clinical trials are urgently needed.

Efficacy of Intraoperative Blood Salvage in Cerebral Aneurysm Surgery

BACKGROUND

The use and effectiveness of intraoperative cell salvage has been analyzed in many surgical specialties. Until now, no data exist evaluating the efficacy of intraoperative cell salvage in cerebral aneurysm surgery.

AIM

To evaluate the efficacy and cost effectiveness of intraoperative cell salvage in cerebral aneurysm surgery.

METHODS

Data were collected retrospectively for all the patients who underwent cerebral aneurysm surgery at our institution between 2013 and 2019. Routinely, we apply blood salvage through autotransfusion. The cases were divided into a ruptured cerebral aneurysm group and a unruptured cerebral aneurysm group.

RESULTS

A total of 241 patients underwent cerebral aneurysm clipping. Of all the cerebral aneurysms, 116 were ruptured and 125 were unruptured and clipped electively. Age, location of the aneurysm, postoperative red blood cell count, intraoperative blood loss, and number of allogenic blood cell transfusions were statistically significantly different between the groups. The autotransfusion of salvaged blood could only be facilitated in eight cases with ruptured cerebral aneurysms and in none with unruptured cerebral aneurysms clipped electively (p < 0.01). Additionally, 35 patients with ruptured cerebral aneurysms and one patient with unruptured cerebral aneurysm required allogenic red blood cell transfusion after surgery, and 71 vs. 2 units of blood were transfused (p < 0.0001). In terms of cost effectiveness, a total of EUR 45,189 in 241 patients was spent to run the autotransfusion system, while EUR 13,797 was spent for allogenic blood transfusion.

CONCLUSIONS

The use of cell salvage in patients with unruptured cerebral aneurysm, undergoing elective surgery, is not effective.

Effects of transfusion load and suction pressure on renal function in intraoperative salvage autotransfusion

Although some investigations have been performed to determine the effects of transfusion load and suction pressure on renal function during intraoperative salvage autotransfusion, the precise threshold is still undetermined. A total of 625 patients undergoing surgery with the Continuous AutoTransfusion System (CATS^plus) were enrolled and divided into groups according to the utilized suction pressure and transfusion volume. Plasma free hemoglobin (FHB) and creatinine clearance (CCr) were assayed to indicate the renal function. Both 0.03 MPa suction (≥4-unit load) and >5 units transfusion changed the levels of FHB and CCr significantly when measured 24 h post-operation compared to pre-operation. Under 0.02 MPa suction (≥4-unit load), the alteration of FHB and CCr returned to normal after 24 h. Under 3 units transfusion, the levels of FHB and CCr at 6 and 12 h post-operation changed significantly compared to pre-operation (P<0.05 or P<0.01, respectively), and this alteration could be restored to normal at 72 h post-operation. After an exhaustive investigation, less than 4 units transfusion and less than 0.03 MPa suction pressure are recommended for intraoperative salvage autotransfusion.

Cell saver physics – a review

Cell salvage, cell saver, cell processor or autologous blood transfusion is the process of collecting a patient’s blood from the surgical field, washing, filtering and transfusing it back to the same patient. There are six basic steps involved in cell salvage. Step one involves the collection of shed blood into a reservoir with an anticoagulant-saline mixture. Step two is the filtration of debris and clots. In step three, the red blood cells (RBCs) are separated from the nonerythrocyte components. This process may be likened to clothes in the washing machine. Washing with saline removes contaminants in step four and the RBCs are resuspended in saline and transferred to the reinfusion bag. Waste products are transferred into the waste bag in step five. In step six, the resuspended, washed RBCs are collected in a bag at room temperature which can be reinfused. The functioning of the cell saver is based on Newton’s First and Second Laws of Motion, where centripetal forces are generated to separate the blood components depending on their density. The denser RBCs are driven to the outer wall of the centrifuge bowl with the plasma collecting on the inside. A typical yield will retrieve 50–95.8% RBCs with a final haematocrit of 50–70%. Cell savers are used in procedures with a large volume of anticipated blood loss, high risk of bleeding, low preoperative haemoglobin, in patients with rare blood groups or multiple antibodies and in some Jehovah’s Witness patients.

Cell salvage in burn excisional surgery

BACKGROUND

Hemostasis during burn surgery is difficult to achieve, and high blood loss commonly occurs. Bleeding control measures are limited, and many patients require allogeneic blood transfusions. Cell salvage is a well-known method used to reduce transfusions. However, its evidence in burns is limited. Therefore, this study aimed to examine the feasibility of cell salvage during burn surgery.

STUDY DESIGN AND METHODS

A prospective, observational study was conducted with 16 patients (20 measurements) scheduled for major burn surgery. Blood was recovered by washing saturated gauze pads with heparinized saline, which was then processed using the Cell Saver. Erythrocyte concentrate quality was analyzed by measuring hemoglobin, hematocrit, potassium, and free hemoglobin concentration. Microbial contamination was assessed based on cultures at every step of the process. Differences in blood samples were tested using the Student's t-test.

RESULTS

The red blood cell mass recovered was 29 ± 11% of the mass lost. Patients' preoperative hemoglobin and hematocrit levels were 10.5 ± 1.8 g/dL and 0.33 ± 0.05 L/L, respectively. The erythrocyte concentrate showed hemoglobin and hematocrit levels of 13.2 ± 3.9 g/dL and 0.40 ± 0.11 L/L thus showing a concentration effect. The potassium level was lower in the erythrocyte concentrate (2.5 ± 1.5 vs. 4.1 ± 0.4 mmol/L, p < 0.05). The free hemoglobin level was low (0.16 ± 0.21 μmol/L). All cultures of the erythrocyte concentrate showed bacterial growth compared to 21% of wound cultures.

CONCLUSION

Recovering erythrocytes during burn excisional surgery using cell salvage is possible. Despite strict sterile handling, erythrocyte concentrates of all patients showed bacterial contamination. The consequence of this contamination remains unclear and should be investigated in future studies.

Clinical Utility of Autologous Salvaged Blood: a Review

INTRODUCTION

Autologous salvaged blood, commonly referred to as "cell saver" or "cell salvage" blood, is an important method of blood conservation. Understanding the mechanism of action and summarizing the existing evidence regarding the safety, efficiency, and the relative costs of cell salvage may help educate clinicians on how and when to best utilize autotransfusion.

METHODS

This review focuses on issues concerning the quality of red blood cells (RBC), efficiency, and the cost effectiveness relative to autotransfusion. The key considerations of safe use and clinical applicability are described along with the challenges for wider dissemination.

RESULTS

Cell salvage can reduce requirements for allogeneic transfusions, along with the associated risks and costs. Autologous salvaged RBCs provide high-quality transfusion, since the cells have not been subjected to the adverse effects of storage as occurs with banked blood. The risks for RBC alloimmunization and transfusion-related infectious diseases are also avoided. With a careful selection of cases, salvaged blood can be more cost effective than donor blood. Cell salvage may have a role in cardiac, major vascular, orthopedic, transplant, and trauma surgeries. However, there remain theoretical safety concerns in cases with bacterial contamination or in cancer surgery.

CONCLUSION

In addition to other methods of blood conservation used in patient blood management programs, autologous salvaged blood adds value and is cost effective for appropriate surgical cases. Evidence suggests that autologous salvaged blood may be of higher quality and confer a cost reduction compared with the allogeneic banked blood, when used appropriately.

Intraoperative cell salvage use reduces the rate of perioperative allogenic blood transfusion in patients undergoing periacetabular osteotomy

Blood loss during periacetabular osteotomy (PAO) is variable, with losses ranging from 100 to 3900 ml in published series. Perioperative allogenic blood transfusion is frequently utilized although is associated with significant risk of morbidity. Cell salvage (CS) is a common blood conservation tool; however, evidence supporting its use with PAO is lacking. Our aim was to assess whether CS affects perioperative allogenic blood transfusion rate in patients undergoing PAO. The clinical records of 58 consecutive PAOs in 54 patients (median age 24.7 years, interquartile range 17.8-29.4 years) performed by a single surgeon between 1 January 2016 and 30 April 2018 were reviewed. Autologous blood pre-donation and surgical drains were not used. Due to variable technician availability, CS was intermittently used during the study period. PAOs were allocated into a CS group or no cell salvage group (NCS group), according to whether an intraoperative CS system was used. There was no significant difference in patient age, gender, body mass index, dysplasia severity, regional anesthetic technique, tranexamic acid administration, surgical duration or estimated blood loss (all P > 0.05) between the two groups. The CS group had a lower preoperative hemoglobin compared to the NCS group (median, 13.4 g/dl versus 14.4 g/dl, P = 0.006). The incidence of allogenic blood transfusion was significantly lower in the CS group compared to the NCS group (2.5% versus 33.3% patients transfused, P = 0.003). Multivariate modeling showed CS use to be protective against allogenic blood transfusion (P = 0.003), with an associated 80-fold reduction in the odds of transfusion (odds ratio, 0.01; 95th% CI, 0-0.57). To our knowledge, this is the first study to assess the effect of CS use on allogenic transfusion rate in patients undergoing PAO. Our results demonstrate CS to be a mandatory component of blood conservation for all patients undergoing PAO.

How do I perform cell salvage in obstetrics?

Maternal mortality in the United States is increasing. The leading cause of death is hemorrhage. Maternal hemorrhage can be profound, with entire blood volumes being lost. In most major blood loss surgery, autotranfusion (also known as cell salvage, cell saving, and intraoperative blood collection and readministration) is a technique that has been used to minimize allogeneic transfusion. Historically, autotransfusion has been considered contraindicated in the face of maternal hemorrhage because of a fear of incorporating amniotic fluid in the salvaged blood. Recent data suggests that this fear is unfounded, with several medical societies now recommending that autotransfusion be used during maternal hemorrhage. In this review, autotransfusion during maternal hemorrhage is discussed, and suggestions are made for how to make it most successful.

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.

Influence of autologous blood transfusion in liver transplantation in patients with hepatitis B on the function and hemorheology of red blood cells

The present study aimed to characterize the function and hemorheology of red blood cells (RBCs) recovered during liver transplantation surgery in patients with hepatitis B and decompensation. A total of 15 hepatitis B patients with decompensation who underwent liver transplantation surgery were included in the present study. Blood samples were recovered during the liver transplantation surgery using an Autologous Blood Recovery System. The morphology and structure of RBCs were characterized and compared between pre-operative and recovered blood samples. In addition, the physiological functions of RBCs were measured and compared between pre-operative and recovered blood samples. No significant differences in the morphological score, 2,3-diphosphoglycerate, Na+K+-ATPase, Ca2+-ATPase, Mg2+-ATPase, malondialdehyde and osmotic fragility were identified between RBCs in the pre-operative and recovered blood samples. The level of free hemoglobin in RBCs of the recovered blood samples was significantly higher than in the pre-operative blood samples (P<0.05). Medium- and high-shear blood viscosities in the recovered blood samples were significantly lower than those observed in the pre-operative blood samples (P<0.05). Casson viscosity in the recovered blood samples was significantly higher compared with the pre-operative blood samples. However, no significant differences (P>0.05) in the low-shear blood viscosity, plasma viscosity, relative blood viscosity, erythrocyte aggregation index or Casson yield stress were identified between recovered and pre-operative blood samples. These findings suggested that autologous blood transfusion in liver transplantation surgery in patients with hepatitis B and decompensation had no significant influence on the morphology, structure, function and hemorheology of RBCs.

Blood loss, predictors of bleeding, transfusion practice and strategies of blood cell salvaging during liver transplantation

Blood loss during liver transplantation (OLTx) is a common consequence of pre-existing abnormalities of the hemostatic system, portal hypertension with multiple collateral vessels, portal vein thrombosis, previous abdominal surgery, splenomegaly, and poor “functional” recovery of the new liver. The intrinsic coagulopathic features of end stage cirrhosis along with surgical technical difficulties make transfusion-free liver transplantation a major challenge, and, despite the improvements in understanding of intraoperative coagulation profiles and strategies to control blood loss, the requirements for blood or blood products remains high. The impact of blood transfusion has been shown to be significant and independent of other well-known predictors of posttransplant-outcome. Negative effects on immunomodulation and an increased risk of postoperative complications and mortality have been repeatedly demonstrated. Isovolemic hemodilution, the extensive utilization of thromboelastogram and the use of autotransfusion devices are among the commonly adopted procedures to limit the amount of blood transfusion. The use of intraoperative blood salvage and autologous blood transfusion should still be considered an important method to reduce the need for allogenic blood and the associated complications. In this article we report on the common preoperative and intraoperative factors contributing to blood loss, intraoperative transfusion practices, anesthesiologic and surgical strategies to prevent blood loss, and on intraoperative blood salvaging techniques and autologous blood transfusion. Even though the advances in surgical technique and anesthetic management, as well as a better understanding of the risk factors, have resulted in a steady decrease in intraoperative bleeding, most patients still bleed extensively. Blood transfusion therapy is still a critical feature during OLTx and various studies have shown a large variability in the use of blood products among different centers and even among individual anesthesiologists within the same center. Unfortunately, despite the large number of OLTx performed each year, there is still paucity of large randomized, multicentre, and controlled studies which indicate how to prevent bleeding, the transfusion needs and thresholds, and the “evidence based” perioperative strategies to reduce the amount of transfusion.

In vitro analysis of cell salvage blood collection with a laparoscopic suction device

STUDY OBJECTIVE

To determine whether cell salvage blood collection with a laparoscopic suction device is inferior to use of a traditional Yankauer suction device.

DESIGN

Prospective, in vitro study.

SETTING

Academic teaching hospital.

INTERVENTIONS

Individual units of donated packed red blood cells were diluted with normal saline solution to a hematocrit level of 21%. The blood was divided into 2 equal parts and then suctioned with either a laparoscopic suction device or a Yankauer plastic suction catheter tip connected to double-lumen cell salvage tubing with a diluted heparin drip and a vacuum pressure of 100 mm Hg. Collected blood was processed with a cell salvage device. Red blood cell volume was calculated by multiplying the hematocrit level by the total volume of blood product at the time of testing. Mean hemolysis indexes were compared between the laparoscopic and Yankauer method of blood collection by use of a 2-sample t test. Assuming a clinically acceptable limit of loss to be 7%, percent loss in red blood cell volume was tested with a 95% one-sided confidence limit to assess noninferiority.

MEASUREMENTS AND RESULTS

The mean hemolysis index was 43.33 with laparoscopic suction method and 34.67 with the Yankauer suction method. The mean difference was 8.67 and was not considered significant (p = .074). The percent loss in red blood cell volume after collection and cell salvage processing was 33.2% with the laparoscopic suction method and 29.57% with the Yankauer method. The mean difference was 3.63% and was within the acceptable 7% loss limit for noninferiority (p = .0278).

CONCLUSIONS

Laparoscopic blood collection is not inferior to the standard Yankauer method for cell salvage collection.

Washing and filtering of cell-salvaged blood - does it make autotransfusion safer?

Autologous transfusion was first performed in the late 1800s, but it was not until the 1970s that devices were developed that enabled widespread adoption of the practice. Unwashed salvaged blood contains thrombogenic products, cell breakdown products and plasma proteins, and gross chemical, cellular and physical contaminants. Washing and filtering of salvaged blood is routinely performed to remove or reduce these elements. In this paper we review the clinical data supporting the need for washing and filtering of salvaged blood.

A hemolysis study of an intravascular blood cooling system for localized organ tissue cooling

Therapeutic hypothermia can reduce both ischemic and reperfusion injury arising after strokes and heart attacks. New localized organ cooling systems offer a way to reduce tissue damage more effectively with fewer side effects. To assess initial blood safety of our new organ cooling system, the CoolGuide Cooling System (CCS), we investigated safe operating conditions and configurations from a hemolysis perspective. The CCS consists of a peristaltic pump, a custom-built external heat exchanger, a chiller, biocompatible polyvinyl cellulose (PVC) tubing, and a control console. The CCS cools and circulates autologous blood externally and re-delivers cooled blood to the patient through a conventional catheter inserted directly into the organ at risk. Catheter configurations used included: a 7F guide catheter only, a 7F guide with a 0.038” wire inserted through the center and advanced 2 cm distal to the catheter distal tip, a 6F guide catheter only and a 6F guide with a 0.014” guidewire similarly inserted through the center. Using porcine blood, an in vitro test rig was used to measure the degree of hemolysis generation, defined as the percentage change in free hemoglobin, adjusted for total hemoglobin and hematocrit, between exiting and entering blood. The highest degree of hemolysis generation was 0.11±0.04%, based on the average behavior with a 6F catheter and a 0.014” guidewire configuration at a blood flow rate of approximately 130 mL/min. In terms of average percentage free hemoglobin exiting the system, based on total hemoglobin, the highest value measured was 0.17%±0.03%, using this 6F and 0.014” guidewire configuration. This result is significantly below the most stringent European guideline of 0.8% used for blood storage and transfusion. This study provides initial evidence showing hemolysis generation arising from the CoolGuide Cooling System is likely to be clinically insignificant.

Hemolysis and red blood cell mechanical fragility in shed blood after total knee arthroplasty

BACKGROUND

There are several options for the salvage of postoperative shed red blood cells (RBCs). This study compared the characteristics of the returned RBCs collected using two different devices: one that washes and one that does not wash the collected RBCs.

STUDY DESIGN AND METHODS

Forty patients undergoing first-time total knee arthroplasty consented to participate. Twenty patients were operated on by a surgeon who routinely uses a device that does not wash the shed RBCs (unwashed group), the other 20 patients were operated on by surgeons who routinely use a device that washes and concentrates the collected RBCs (washed group). A small quantity of postprocessing RBCs were collected immediately before reinfusion and the amount of plasma-free hemoglobin (PFHb), and the mechanical fragility index (MFI) of the returned RBCs were determined.

RESULTS

The patients in both groups were well matched for age, sex, and length of stay. The mean percent hemolysis of the returned RBCs was not different between the unwashed and washed groups (1.22±0.30 vs. 1.24±0.42, p=0.895), while the mean total amount of returned PFHb was not different (0.51±0.12 g vs. 0.55±0.35 g, p<0.615). The ratio of total PFHb:total returned Hb was significantly lower for the washed group (0.0087±0.0023 vs. 0.0035±0.0011, p<0.0001). The MFI was higher in the washed group (1.71±0.55 vs. 0.53±0.42, p<0.001).

CONCLUSIONS

The washing device returned more Hb to the patients relative to the amount of free Hb.

The impact of suctioning RBCs from a simulated operative site on mechanical fragility and hemolysis

Background

Intraoperative cell salvage exerts shear stress upon RBCs, particularly as they are suctioned from the surgical field. Shear stress can result in overt hemolysis or it can cause sublethal injury to the suctioned RBCs. The mechanical fragility (MF) test uses shear stress to measure the extent of RBC sublethal injury. RBCs that have sustained sublethal injury are more susceptible to shear stress induced hemolysis. In this study we suctioned whole blood samples from an artificial surgical field to determine if pre-menopausal female RBCs would demonstrate greater resistance to hemolysis and less sublethal injury compared to that of males and post-menopausal females.

Methods

Ten CPD-preserved whole blood units from these 3 donor groups were obtained and samples suctioned at -150 mmHg from a simulated surgical field. The MF test was then performed and the % hemolysis calculated. In addition the MF test was serially performed on these whole blood units during the 21 days of storage.

Results

There were no differences in the extent of hemolysis or RBC shear stress resistance after suctioning between the 3 donor groups. During storage the pre-menopausal female RBCs demonstrated higher shear stress tolerance compared to the males or post-menopausal females at all of the time points.

Conclusion

Although during static storage pre-menopausal female RBCs in CPD-preserved whole blood demonstrated higher shear stress tolerance, this enhanced resistance was not observed after suctioning from a simulated surgical field.

Cell salvage as part of a blood conservation strategy in anaesthesia

The use of intraoperative cell salvage and autologous blood transfusion has become an important method of blood conservation. The main aim of autologous transfusion is to reduce the need for allogeneic blood transfusion and its associated complications. Allogeneic blood transfusion has been associated with increased risk of tumour recurrence, postoperative infection, acute lung injury, perioperative myocardial infarction, postoperative low-output cardiac failure, and increased mortality. We have reviewed the current evidence for cell salvage in modern surgical practice and examined the controversial issues, such as the use of cell salvage in obstetrics, and in patients with malignancy, or intra-abdominal or systemic sepsis. Cell salvage has been demonstrated to be safe and effective at reducing allogeneic blood transfusion requirements in adult elective surgery, with stronger evidence in cardiac and orthopaedic surgery. Prolonged use of cell salvage with large-volume autotransfusion may be associated with dilution of clotting factors and thrombocytopenia, and regular laboratory or near-patient monitoring is required, along with appropriate blood product use. Cell salvage should be considered in all cases where significant blood loss (>1000 ml) is expected or possible, where patients refuse allogeneic blood products or they are anaemic. The use of cell salvage in combination with a leucocyte depletion filter appears to be safe in obstetrics and cases of malignancy; however, further trials are required before definitive guidance may be provided. The only absolute contraindication to the use of cell salvage and autologous blood transfusion is patient refusal.