Acute Normovolemic Hemodilution
The easiest method for decreasing red cell loss during surgery in relatively normovolemic adults is to use acute normovolemic hemodilution (ANH), also known as acute isovolemic hemodilution. This is when the patient's blood is removed (to keep for later transfusion) and replaced with 500 mL to 1 L crystalloid (or occasionally colloid) immediately before surgery. This dilutes the blood volume and results in a smaller decrease in hematocrit for the same volume of blood loss.1 Since this process reduces the loss of RBC mass during surgery, it can be used for urgent or elective procedures to decrease the requirement for preoperative blood donation and the use of banked blood.15
This technique provides fresh whole blood for use in the operating room (OR) and is safe (uses the patient's own blood), convenient for the patient, simple to perform, and inexpensive. Use ANH if the surgical blood loss is anticipated to be >15 mL/kg and the patient has an Hgb ≥10 g/dL before surgery. For nonemergent surgery, give iron to patients with a lower Hgb to raise their Hgb level before the operation. Patients excluded from this procedure are those with sickle cell disease, severe cardiac disease, bacteremia, liver disease, or bleeding disorders.16 At the conclusion of surgery or if there is an indication that a transfusion is necessary during the procedure, collected blood may be returned to the patient.3 It is especially useful for hospitals with limited or no blood bank facilities.17-19
At the onset of surgery in a stable patient who is not hemorrhaging, use a 14-gauge IV catheter in an antecubital vein to remove either 2 L of blood or enough so the hematocrit is 28%, whichever comes first. Drain the blood into a sterile container with anticoagulant (generally 64 mL CPD [citrate-phosphate-dextrose] or the equivalent/500 mL blood).
The volume to be removed (V) is determined using the formula17:
where: EBV (patient's estimated blood volume) = body weight (kg) × 70 mL/kg
- H1 = patient's initial Hct
- H2 = patient's target Hct after hemodilution
- Havg = the average Hct (average of H1 and H2)
As the first liter of blood is removed, it is simultaneously replaced with an equal volume of colloid solution, if available, and then with crystalloid in a 2:1 ratio. (Up to a 3:1 ratio can be used if only 1 unit is removed.)19 If colloid is not available, use crystalloid for all replacements. If there is only one IV line, the blood collection and the infusion of replacement fluids are alternated. If there are two IV lines, they occur simultaneously.16 Immediately label all blood units with the patient's identifying information.
Obtain Hct levels and vital signs immediately before hemodilution, after the removal of each 500 mL of blood, and at the end of the hemodilution procedure. Patients should receive hemodiluted blood intraoperatively to maintain their Hct >25%. Transfuse all hemodiluted blood before discharging the patient from the recovery area.17
Unlike preoperative autologous blood donations (described subsequently), ANH requires minimal preoperative preparation and produces negligible patient inconvenience. The procedure can be used for some patients requiring unplanned operations—including Cesarean sections. Probably most important in austere situations is that the blood does not require a blood bank: it is stored at room temperature at the patient's bedside and administered only to that patient. This also reduces the human errors inherent in the process of giving the correct blood to the patient.16,17
Blood or cell salvage is when shed blood is collected from a wound or body cavity and then reinfused into the same patient. The general rule is to use this technique if the patient seems likely to lose <20% blood volume,1 although this technique works well to supplement allogenic (another patient's) or presurgically donated blood.
This technique is often used for patients presenting with ruptured ectopic pregnancies, which are a common cause of massive intraperitoneal hemorrhage. Many of these women present in hypovolemic shock, because considerable time often elapses between the ectopic rupture and the patient's arrival at the hospital. Part of the high mortality associated with ectopic pregnancies in both developed and least-developed countries is due to the scarcity of blood available for transfusion. Using blood salvage and autotransfusion often leads to a normal recovery.20 The techniques are also used for hemothoraces from penetrating chest injuries and for blunt abdominal injuries with hepatic or splenic bleeding.21
Use autologous transfusion only if blood can be removed from a cavity (usually the chest or abdomen) where it has been for less than 24 hours, although some clinicians try to limit it to 12 hours or less.
Blood from sterile cavities, such as the chest or abdomen, without visceral injuries or evidence of overt hemolysis is preferred.1 Contraindications to salvage include blood contaminated with bowel contents, bacteria, fat, amniotic fluid, urine, malignant cells, and irrigation fluids.4,16 Blood from contaminated abdominal wounds can be used, but with an increased risk of systemic infection.22 The patient's condition determines when the blood is reinfused, although the units should be used within a few hours to limit the chance of bacterial growth. If possible, it is best to wait to transfuse until bleeding has been surgically controlled.
Draining the blood from abdominal bleeding (usually due to a ruptured ectopic pregnancy or blunt abdominal trauma) is often called pre-incision needle drainage, but it can also be performed through a tiny opening in the peritoneum once it is exposed. To do this, make a small peritoneal incision while "tenting" the peritoneum to avoid spillage. If the intraperitoneal blood appears fresh and is the normal color, collect it in small containers. If the hospital has a blood bank, the first aliquot of blood should be sent for type and cross-match, in case additional blood is needed.
Multiple variations of the following two methods have been described. The first method is to collect the blood by scooping it (or letting it drain) into a sterile bowl and then pouring it through gauze into another sterile container. A person wearing sterile gloves then uses 50-mL syringes to infuse the blood into a transfusion bag. The syringe may need to be rinsed with normal (0.9%) saline (NS) occasionally to prevent the plunger from sticking.23
The second method, faster and more elegant, to use for ruptured ectopic pregnancies (but that could also be used for hemothoraces) is to position the patient so that the fluid is dependent. With a hemoperitoneum, that will usually be in a feet-down (i.e., reverse Trendelenburg) position with the patient turned slightly to the right side. After prepping the area, introduce a 15-gauge needle into the right iliac fossa. Connect it to a standard blood set and blood collection bag with anticoagulant. Gently manipulate the needle, allowing the blood to flow freely into the bag. Another method to increase flow is to lavage the abdomen with NS, although this results in lowering the Hgb of the collected blood. The blood is transfused using a filter to avoid clots.24,25 The bowel is rarely injured when using the percutaneous needle since, like draining ascites, the bowel normally floats away from the needle. Of course, the process can be done under ultrasound guidance, which may be even safer.20
After removing most of the fresh blood, enlarge the peritoneal incision and clamp the bleeding site. At that point, some clinicians scoop (not suck) blood from the abdomen into sterile containers1; others use gentle suction (<40 mm Hg).20
When there is bleeding into the chest cavity, blood is commonly drained out through a chest tube using gravity. Blood drains through a funnel lined with several layers of gauze and into a sterile glass bottle containing anticoagulant such as CPDA-1 (citrate-phosphate-dextrose-adenine) (Fig. 17-1). The bottle can then be inverted and directly infused through an IV with a 200-micrometer filter.21
Improvised cell salvage from a chest tube.
Gauze is frequently used to filter the blood. No less than three, and preferably eight, layers of sterile gauze should be used to screen out small clots and tissue fragments that could cause pulmonary emboli or disseminated intravascular coagulation, before putting the blood into sterile bags or bottles with anticoagulant (if available).1,4,20
For each 500 mL of blood, add 60 mL of 3.8% sodium citrate (3.8 g/L) or 12 mL of citric acid monohydrate-trisodium citrate dihydrate-glucose solution. If clots appear, re-filter the blood. Reinfuse this blood immediately; do not store for later use.25 If anticoagulant is not available, prepare acid-citrate/dextrose (ACD) by mixing 2 g sodium citrate and 3 g dextrose in enough sterile water to make a total volume of 120 mL, which is sufficient for 1 unit of blood.20
An alternate formula for preparing ACD is to combine 8 g citric acid monohydrate, 22 g tri-sodium citrate dihydrate, and 24.5 g dextrose monohydrate, mix, and add it to 1000 mL distilled water to make the ACD solution. Then place 75 mL of the ACD solution in a 500-mL blood bottle and autoclave it. Alternatively, the dry ACD mixture can be separated into 4-g portions and wrapped in waxed paper. A 4-g packet is the amount necessary for one 500-mL blood bottle. Each time blood bottles are made up, empty the contents of one packet into the bottle, add 75 mL of distilled water, and autoclave the bottle.26
In some cases, especially in dire emergencies, cell salvage may be used either without anticoagulants or with alternative anticoagulants (such as heparin).21,27 Blood that flows freely and has been in contact with serosal surfaces (e.g., peritoneum, pericardium, and pleura) usually lacks fibrinogen and may not need an extra anticoagulant. Either using heparin anticoagulation or not using anticoagulants has been used without any complications. If CPDA-1 is in short supply, a half-dose (30 mL/500 mL blood) can also be used.21
Cell salvage has been shown to be safe, simple to use, and culturally acceptable. The method poses no risk of either transfusion reactions from mismatches or the transmission of blood-borne diseases. The blood is immediately available, since there is no need to do a type and cross-match. The method is so simple that it can be done in resource-poor settings without elaborate equipment or the electricity needed for blood refrigeration. In cultures that fear or ban blood donation or receiving blood from others, this method may overcome some of their concerns.
The potential harmful complications of infection, embolism, or coagulopathies are far outweighed by the lifesaving potential of the procedure. The chance of infection from the transfusion is markedly lessened by using sterile equipment and by discarding blood from a contaminated source, such as an abdomen with ruptured bowel or tubo-ovarian abscess. Transfuse blood as soon as possible to avoid the proliferation of any bacteria that are present. Coagulopathy is more common when this technique is used with ruptured ectopic pregnancies (due to trophoblastic products) than with other abdominal or chest injuries. Yet, few complications have been reported. Some of these complications, including renal failure from transfusing hemolyzed blood, have led some clinicians to limit its use to bleeding sites that are no more than 3 hours old.21
Preoperative Autologous Blood Donation
Preoperative autologous blood donation (PABD) is one of the safest methods of obtaining blood for anticipated surgical blood loss. The method can be used anywhere a blood bank exists. Ideally, 4 to 5 weeks before an elective operation, the patient donates blood for use during surgery.
However, PABD is expensive, since it requires that there be a functioning blood bank in which to store the blood. The procedure is also prone to some human error, since the correct patient's blood must be identified and administered. Moreover, since patients can donate only a limited amount of blood, that amount may be insufficient to replace the blood lost at surgery.1