Case Study
A woman in her second pregnancy was booked for an elective cesarean delivery at 37 weeks’ gestation. Her first pregnancy required a classical cesarean delivery due to a 10-cm lower uterine segment fibroid, and the patient had since undergone a myomectomy. Ultrasound examination showed a possible placenta accreta overlying the scar. Because her family was complete, she was consented for a potential cesarean hysterectomy in case an adherent placenta was found at delivery, which could lead to massive hemorrhage with persisting efforts to remove it. Her preoperative hemoglobin was 118 g/liter.
A combined spinal-epidural anesthetic technique (spinal dose 12.5 mg hyperbaric bupivacaine with 300 µg diamorphine) was used, with a crystalloid coload and a phenylephrine infusion to maintain blood pressure. Cell salvage was used from the start of surgery, with a separate suction catheter to remove amniotic fluid. After a healthy baby girl was delivered, 5 units of oxytocin was given slowly, followed by a 10 unit/h oxytocin infusion. At this point, the lower part of the placenta separated, and umbilical cord traction, in an attempt to detach the rest of it, produced dimpling of the uterus where the placenta remained adherent despite additional doses of uterotonics. A hysterectomy was subsequently performed as planned, with assistance from the attending gynecologist. Anesthesia was maintained with 5- to 10-ml boluses of epidural 0.5% levobupivacaine and 100 µg fentanyl. The patient remained hemodynamically stable throughout the procedure. The estimated blood loss was 1,500 ml, and most of this was collected both directly and by rinsing blood-soaked swabs. This was processed by the Cell Saver, and 477 ml of autologous blood was returned using a leukocyte depletion filter (LDF). The patient had a brief episode of symptomatic hypotension (BP 67/31 mmHg) on transfer to the high-dependency unit, but she recovered spontaneously and did not require further fluid boluses or vasopressor treatment. The patient received overnight high-dependency care. The postoperative hemoglobin concentration was 119 g/liter. The patient made an uneventful recovery and was discharged home on the third postoperative day.
Key Points
Anticipation of problems during cesarean delivery in this patient due to her placenta accreta, fibroids, and previous uterine scarring resulted in a planned cesarean hysterectomy that avoided massive hemorrhage.
Intraoperative cell salvage was used from the beginning of the procedure to collect most of the blood lost during surgery.
The transfusion of autologous blood prevented postoperative anemia while avoiding the risks of allogeneic blood transfusion.
Discussion
It is routine practice to ensure that cross-matched blood is available for elective cesarean delivery patients at high risk of major obstetric hemorrhage. However, transfusion of allogeneic red cells is associated with many potential hazards for the parturient, with a 1 in 7,000 risk of acute transfusion reaction.1
In 2014, 3,017 adverse events were reported to the Serious Hazards of Transfusion (SHOT) group,2 the majority of which were near misses due to error:
10 patients were given ABO-incompatible red cell transfusions due to clinical errors in either collection or administration, with one patient developing renal failure.
169 cases of major morbidity occurred, the majority due to acute allergic or febrile transfusion reactions and pulmonary complications.
Transfusion-associated circulatory overload (TACO) accounted for 36 cases of major morbidity (two of which were obstetric) and six deaths (none were obstetric). This is a particular hazard when several units of allogeneic blood are given to treat obstetric hemorrhage. Allogeneic blood from blood donors is also increasingly facing supply problems due to rising demand in the face of reducing number of donors.
Intraoperative cell salvage (IOCS) offers an effective alternative, providing a suitable supply of autologous blood from the patient in direct proportion to the magnitude of intraoperative hemorrhage, provided that no contraindications exist.
Autologous blood is fresh and warm, with red cells that maintain normal shape and deformability, resulting in an increased mean viability (88 percent compared with 70 percent for allogeneic blood).3, 4 Transfusion of autologous blood does not affect 2,3-diphosphoglycerate (DPG) levels in circulating blood, preserving oxygen transport capacity, unlike allogeneic blood, which reduced 2,3-DPG levels from 4.3 to 3.9 µmol/liter.5 This has potential benefits in improving recovery and reducing postoperative complications with little danger of immunomodulation, transmission of infections, hyperkalemia, or acidemia. It is also free from the dangers of incorrect blood transfusion because it is always started in a single-patient environment.
Mechanism of Cell Salvage
A dual-lumen anticoagulated suction tube is used to aspirate blood directly from the operative site or from blood-soaked swabs rinsed in saline (Figure 34.1). The collected blood is passed through a filter and collected in a reservoir. Once sufficient blood has been collected, the cell salvage machine can be set to manual or automatic to process the blood using a differential centrifugation bowl. This washes the cells and removes less dense elements, including platelets, activated clotting factors, and complement. The output contains red cells suspended in saline with a hematocrit of 0.5–0.8, which can be returned to the patient as an autologous transfusion within the next 6 hours.
Figure 34.1 Cell salvage circuit
IOCS Benefits in Nonobstetric Surgery
IOCS has become well established in nonobstetric surgery since the 1970s. A Cochrane review of 75 randomized, controlled trials in orthopedic and cardiac surgery found that IOCS reduced the requirement for allogeneic blood by 38 percent without adversely affecting mortality or morbidity.6 Cell salvage is considered to be very safe and an essential standard of routine care in many specialties, such as vascular, orthopedic, and cardiac surgery.2 Current guidelines from the Association of Anaesthetists of Great Britain and Ireland (AAGBI) for the use of blood components recommend that cell salvage be considered for high- or medium-risk surgery in nonobstetric adult patients when blood loss is likely to exceed 500 ml.7
Controversies Regarding IOCS in Obstetrics
For many years, IOCS was considered to be inappropriate for use in obstetrics for the following reasons.
1. Amniotic Fluid Contamination with IOCS
IOCS was thought to be contraindicated in cesarean delivery due to concerns about contamination of salvaged blood with amniotic fluid, potentially causing an amniotic fluid embolism (AFE). This syndrome was previously thought to be an embolic disease occurring when components of amniotic fluid entered the maternal circulation, causing hypoxia, collapse, coagulopathy, and a high mortality rate, with evidence of fetal squamous cells in postmortem maternal lung tissue. This may have been an erroneous explanation because there is evidence that amniotic fluid routinely enters the maternal circulation at the time of delivery.8, 9 The pathophysiology is now better understood, and it is thought that endothelin-1 plays a part in the early transient pulmonary hypertension, while amniotic fluid–derived tissue factor may be responsible for disseminated intravascular coagulopathy (DIC) as part of an anaphylactoid syndrome.10
Using a separate suction catheter for the amniotic fluid reduces the amount of contamination, and the wash process of cell salvage has been shown to completely remove active tissue factor from postwash samples.11 However, some particulate components remain. The use of leukocyte depletion filters (LDFs) in obstetric patients significantly reduces the level of particulate contaminants to a concentration similar to that seen in maternal venous blood at delivery.12, 13
Leukocyte depletion of blood was described by Alexander Fleming in 1926 when he was investigating the effects of leukocytes on bacterial growth using cotton wool. Modern filters use a synthetic mesh made from a nonwoven web of microfibers. There is a coarsely woven prefilter, which screens out microaggregate debris. As the blood passes deeper through the filter layers, the effective pore size of the filter decreases. This physical barrier is supplemented by adhesion of leukocytes to the filter fibers.14 LDFs are used to remove white cells from allogeneic blood transfusions to reduce the risk of adverse reactions and also have been shown to remove tumor cells when cell salvage is used for patients with malignancy.
There has only been one published case where AFE was claimed to have occurred following IOCS, in a Jehovah’s Witness with HELLP syndrome who refused allogeneic blood products and received salvaged blood without an LDF. However, this diagnosis has been called into question in subsequent correspondence.15
2. Alloimmunization with IOCS
Alloimmunization is an additional consideration for Rhesus-negative mothers whose fetus may be Rhesus positive. This occurs when the mother’s immune system is sensitized to foreign erythrocyte surface antigens by the transplacental passage of fetal red cells during delivery, trauma, or invasive obstetric procedures, stimulating the production of IgG antibodies. In subsequent pregnancies, these antibodies cross the placenta with potentially fatal consequences for the fetus, including hydrops fetalis. This can be prevented by antenatal Rhesus D immunoglobin prophylaxis
It has been shown that small amounts of transplacental hemorrhage (TPH) occur throughout pregnancy, peaking at delivery, with 1 percent of women having a TPH greater than 2.5 ml and 0.3 percent greater than 15 ml.16 The quantity of fetal red cells that have entered the maternal circulation can be estimated by the Kleihauer test to determine the correct dose of anti-D. A dose of 500 IU within 72 hours of delivery is sufficient to neutralize up to 4 ml of fetal red cells.17
During cesarean delivery, fetal red cells may contaminate maternal blood aspirated during IOCS that are not removed by washing or using a LDF. The volume of fetal cells in reinfused blood may vary from 1 to 20 ml.12, 18 Current guidance from the British Committee for Standards in Haematology states that where the cord blood group is confirmed to be RhD positive (or unknown), a minimum of 1,500 IU of anti-D should be given after the reinfusion of salvaged red cells, and a maternal sample should be taken 30–45 minutes afterwards in case further anti-D is required. The transfusion laboratory must be informed so that the correct dose of anti-D is issued.17
Problems with LDF in Clinical Practice
The main problem with using a LDF in clinical practice is that it considerably slows the rate of reinfusion of salvaged blood, which is undesirable when treating hypovolemia associated with massive obstetric hemorrhage. The manufacturers advise that pressurized infusion bags must not be used to increase the rate of flow because the IOCS bags are weaker than standard blood bags and may rupture, which would defeat the purpose. There is also about 50–70 ml of air in the tubing that is pushed into the bag when it fills with processed blood, and pressurizing can result in air embolism. However, most reinfusion bags have two exit ports, and the speed of infusion can be doubled by spiking both ports.
There have also been several case reports of transient hypotension attributed to use of an LDF for the transfusion of salvaged blood in massive obstetric hemorrhage, which reversed when the transfusion was stopped.19 In each case, pressure bags or syringes had been used to expedite the flow rate. This may have triggered a bradykinin burst within the negatively charged filter. Bradykinins are generated when plasma comes into contact with a negatively charged surface. This activates factor XII, which, in turn, activates the kinin-kallikrein system, resulting in the generation of bradykinin, a nonapeptide that causes vasodilation until it is rapidly broken down by kininases, including an angiotensin-converting enzyme inhibitor.20
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