Obstetric intra-operative cell salvage: a review of an established cell salvage service with 1170 re-infused cases.

The use of cell salvage during caesarean section has been increasing steadily, although there are concerns relating to cost, a perceived risk of amniotic fluid embolism, and fetal red cell sensitisation. We present observational data from almost a decade of use of intra-operative cell salvage in obstetrics. By the end of this period, we set up cell salvage collection for > 98% of all caesarean sections. From 2008 to 2017, 1170 women have had a re-infusion of cell salvaged blood with no clinical safety concerns; the median (IQR [range]) volume was 231 (154-306 [80-1690]) ml. During this time there has been a marked reduction in the number of women who were transfused allogeneic blood, as well as the amount of blood transfused. In total, 647 (55%) women have had alloimmunisation testing, with two positive cases. Quality control data indicate that the quality of blood processed from partial first bowls is no worse than that from full bowls. We discuss the costs of providing this service with regard to: staffing costs; single suction; leucodepletion filters; selectivity in the processing of collected blood; and the use of partial first bowls.

Obstetric intra-operative cell salvage and maternal fetal red cell contamination.

BACKGROUND: The significance of fetal red blood cell (RBC) contamination in obstetric intra-operative cell salvage is not fully known. It is unclear if we re-infuse a larger volume of fetal RBCs into the maternal circulation than the amount that occurs secondary to transplacental haemorrhages is unclear. We also do not know if there is a critical volume required to cause alloimmunisation or if larger volumes increase the risk. OBJECTIVES: The aim of this study is to provide data on the level of fetal RBC contamination in the maternal circulation prior to delivery and immediately post-partum and to compare these levels to those found in processed cell-salvaged blood. METHODS: In the first part of this study, we quantified the levels of fetal RBCs circulating in women immediately prior to delivery. This was then repeated with a separate group measuring the levels of fetal RBCs pre- and post-delivery. RESULTS: We found that 37% of women had fetal cells detected in their circulation, median 0·00 mL (IQR 0-0·24; average 0·3 mL, maximum 4·56 mL). Fetal RBCs were present pre-delivery (maximum 0·66 mL) in 16% of women, increasing to 53% post-delivery (median 0·66 mL; IQR 0·22-2·20, maximum 21·20 mL). CONCLUSIONS: We have shown that fetal RBCs are present in the maternal circulation throughout pregnancy and that the volumes are comparable to that obtained from intra-operative salvage, with contamination amounts of up to 19 mL. At the Royal Cornwall Hospital, our experience and evidence supports offering intra-operative salvage to all women, and we have not noted an increase in antibody formation, compared to allogeneic transfusion.

Is cell salvaged vaginal blood loss suitable for re-infusion?

BACKGROUND: Haemorrhage is one of the commonest causes of maternal critical care admission. Cell salvage used during caesarean section can contribute to a reduction in allogeneic blood consumption. This study sought to provide a practical method to salvage blood lost after vaginal delivery and a description of the constituents before and after washing. METHODS: Blood lost after vaginal delivery was collected from 50 women and washed in a cell salvage machine. No blood was re-infused to any patient in this study. The following measurements were made pre- and post-wash: haemoglobin (haematocrit), alpha-fetoprotein, albumin, lactate dehydrogenase, plasma free haemoglobin, heparin concentration, fetal red cells and identification of bacterial species and colony-forming units (cfu). RESULTS: Median haemoglobin concentration post-wash was 15.4 g/dL. Alpha-fetoprotein, lactate dehydrogenase and albumin concentrations were significantly reduced post-wash (<1 KU/L, 183 IU/L, 0.011 g/L, respectively; P <0.001). Median fetal red cell level post-wash was 0.15 mL [range 0-19 mL]. Median bacterial contamination concentration post-wash was 2 cfu/mL, with a median total count of 303 cfu. CONCLUSIONS: Vaginal blood can be collected efficiently with little disruption to patient management. The amounts of haemolysis and washout of non-red cell blood components are consistent with results in our cell salvage quality assurance programme for caesarean section and non-obstetric surgery. Although bacteria are detectable in all the post-wash and post-filter samples, the median residual contamination is similar to that found with cell salvage in caesarean section, and if re-infused would result in a circulating bacteraemia of <1 cfu/mL; this is similar to that seen with dental procedures (0.3-4.0 cfu/mL) and is thought to be clinically insignificant.

Assessment of intra-operative cell salvage haemolysis in the obstetric and orthopaedic clinical setting, in comparison with allogeneic blood.

OBJECTIVES/BACKGROUND: Haemolysis is still a re-occurring theme in intra-operative cell salvage (ICS) with further haemolysis possibly caused by suction pressure, washing/centrifuging process and aspiration method. Previous investigations, along with manufacturer's reports, state that between 75 and 95% of free haemoglobin (Hb) is removed by the washing and centrifugation process; however, if these results are above the expected levels, excess free Hb may remain after washing. The aim of this article was to quantify haemolysis levels whilst employing different aspiration methods from skimmed (orthopaedics) and pooled (obstetrics) surgery types and comparing this to allogeneic blood. METHODS/MATERIALS: Samples obtained from 50 allogeneic units and 50 ICS cases (25 obstetric and 25 orthopaedic) were tested for plasma free Hb levels. RESULTS: Free Hb testing as a marker of haemolysis was greatest in orthopaedic 17·2 g L(-1) (range: 1·7-57·0 g L(-1) ), obstetric 2·8 g L(-1) (range: 1·0-13·5 g L(-1) ) and allogeneic 0·95 g L(-1) (range: 0·2-4·8 g L(-1) ) cases. CONCLUSION: ICS involving skimming collection techniques (orthopaedics) had significantly more haemolysis than pooled collections (obstetrics) (P < 0·001). Further analysis of orthopaedic data highlighted a difference between the three machines used with the Haemonetics OrthoPat (Haemonetics Ltd., Watford, UK) significantly higher with a free Hb of 29·8 g L(-1) compared with the other two machines 6·7 g L(-1) (P < 0·001). On comparison of ICS blood to allogeneic blood, free Hb levels obtained from ICS were significantly higher (P < 0·001).

Lactate dehydrogenase and Haemolysis Index as quality control markers of haemolysis in intra-operative cell salvage.

OBJECTIVES: The aim of this investigation was to explore the potential use of the tests lactate dehydrogenase (LDH) and Haemolysis Index as haemolysis markers in intra-operative cell salvage (ICS) blood in comparison to plasma free haemoglobin levels. BACKGROUND: Quality control (QC) should be seen as a fundamental part of any ICS blood conservation programme, however, due to lack of available knowledge, familiarity and experience, QC is still a comparatively new subject. A QC pilot scheme is currently being undertaken by the Royal Cornwall Hospital in association with the UK Cell Salvage Action Group to explore potential markers that can be used to assess the quality of blood obtained from ICS. This test list should be available to all ICS users and achievable within financial budgets. Currently this proposed test list includes a full blood count, a protein marker such as urine albumin/microalbumin and heparin monitoring. Haemolysis testing is another key marker. METHODS/MATERIALS: Samples were collected from ICS processed blood and allogeneic SAGM leucodepleted red cell units and processed for plasma free haemoglobin, LDH and Haemolysis Index. RESULTS: There was a very strong correlation between plasma free haemoglobin and LDH (0.960), and plasma free haemoglobin and the Haemolysis Index (0.944). CONCLUSION: We have shown that the LDH and Haemolysis Index tests are suitable and reliable alternatives for measuring haemolysis from samples obtained from ICS or allogeneic blood. We have incorporated the LDH test into our Hospital's ICS QC package and recommend that this test is considered for all ICS QC samples.

A modified thrombin clotting time test as a quality control marker for heparin contamination in obstetric intraoperative cell salvage.

OBJECTIVE: To assess if a modified thrombin clotting time test could be used as a simple quality control (QC) method to screen for unfractionated heparin in the product obtained from obstetric intraoperative cell salvage cases before re-infusion. BACKGROUND: A national QC scheme has recently been piloted to monitor the quality of autologous blood being returned to the patient. Laboratory tests include full blood count and microalbumin. Unfractionated heparin testing should be performed to ensure that there is no gross contamination of heparin in the final product; however, presently, there is no quick cheap test available suitable for heparin detection. MATERIALS AND METHODS: Samples were collected into plain non-anticoagulated tubes and centrifuged at 2500 × g for 5 min. Supernatant was mixed with commercially available coagulated normal plasma and a thrombin clotting time test performed. RESULTS: Calibration runs demonstrated that our system was sensitive up to 0 · 14 IU mL(-1) heparin, linear between 0 · 08 and 0 · 14 IU mL(-1). CONCLUSION: We have shown that the thrombin clotting time test can be modified and used as a cheap and reliable marker for heparin contamination. We have successfully incorporated this modified test into our hospital's obstetric QC scheme.

Ultrasonic measurement of gas flow using electrostatic transducers.

Ultrasonic gas flowmeters typically use narrowband piezoelectric transducer arrangements for interrogating the flow of gas in a pipe. In this work, the suitability of broadband electrostatic transducers operating at frequencies of up to 1 MHz for ultrasonic measurement of gas flow has been investigated. The transit time method of ultrasonic gas flow measurement was adopted and experiments were carried out using a laboratory test rig capable of producing a range of gas flowrates up to 17.5 m/s. The test rig also allowed easy interchange of different prototype flowmetering sections. Times of flight of ultrasonic waves interrogating the gas flow were measured using separate send/receive electrostatic transducer arrangements. Two flowmeter configurations were considered. The first interrogated the flow at 45 degrees in contra-propagating upstream and downstream directions. The second consisted of an up-stream interrogation at 45 degrees to the gas flow and an interrogation made normal to the flow direction. k factors correlating the fluid velocity along the ultrasonic path with the mean fluid velocity in the pipe were calculated using experimental ultrasonic data and anemometer measurements. All transducer configurations were numerically modelled using the computational fluid dynamics software package FLOTRAN (ANSYS Inc.). Theoretical gas flow velocities for both transducer arrangements were subsequently compared with experimental values and found to be in excellent agreement. A flow-dependent frequency shift of the received ultrasonic signals was also observed simultaneously with the transit time measurement.