In austere situations, there may be no blood available for transfusion. If blood is available, there is a greater risk that it could be contaminated and infect the patient than under optimal circumstances. In addition, the methods to rapidly rewarm blood to avoid the complications of hypothermic transfusion may not be available.

Blood can easily transmit human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), Chagas disease, malaria, and other diseases. Only about 66% of developed countries and 46% of least-developed countries screen blood for HIV, although there is about a 90% seroconversion rate following the transfusion of blood infected with HIV. Even where (often, for-profit private) blood banks purport to screen for HIV, many either don’t screen or use insensitive tests. Government oversight is sparse.^1,2

Use non-blood substitutes, if possible. They are much safer, easier to use, and can be less costly than using blood. Substitutes include crystalloids, synthetic colloids (e.g., Dextran), and noninfectious plasma derivatives. For all but crystalloids, however, both cost and availability may be a problem.

To avoid a transfusion, especially in the operative patient: (a) restrict preoperative diagnostic phlebotomy, (b) use meticulous intraoperative surgical hemostasis, (c) use blood/cell salvage, (d) employ hemodilution, (e) use pharmaceutical hemostasis agents, (f) maintain normothermia, and (g) position patients to minimize blood loss and hypertension. Postoperatively, (a) use blood/cell salvage, (b) tolerate anemia (as described later in this chapter), (c) optimize fluid and volume management, and (d) restrict diagnostic phlebotomy. The units of blood potentially saved by not doing a transfusion with each strategy are shown in Table 18-1.³

The decision to transfuse blood depends on the patient’s clinical condition and their ability to compensate for reduced tissue oxygenation. Patients with evidence of severe cardiac or respiratory disease or with preexisting anemia have a limited ability to compensate.⁴ In critically ill, non-bleeding adult patients <55 years old and without evidence of an acute myocardial infarction or unstable angina, keeping the hemoglobin (Hgb) >7.0 g/dL, rather than >10 g/dL, does not change mortality rates.⁵ The mortality increases dramatically, however, when the Hgb drops lower than 5 to 6 g/dL, especially in postoperative patients.⁶

Severe Anemia

When the blood supply is scarce or dangerous, clinicians must tolerate levels of anemia in their patients that would be unacceptable under optimal conditions. The World Health Organization (WHO) defines very severe anemia in a child as Hgb <4 g/dL (40 g/L) or a hematocrit (Hct; packed-cell volume) <12%. If the blood supply is routinely tested for HIV and HBV, transfuse these children with 10 mL/kg packed red blood cells (PRBCs). If the blood supply may be tainted, wait to transfuse until the Hgb is <3 g/dL (30 g/L) or the Hct is <10%.⁷ Also limit the amount transfused. Critically ill children in modern intensive care units do as well when transfusions keep their Hgb >7 g/dL as they do when kept at the more common Hgb level of 9.5 g/dL.⁸

In adults, clinicians generally use an arbitrary Hgb level of 10.0 g/dL to indicate that a transfusion is necessary. But patients can tolerate lower Hgb levels than previously believed.⁶ Except for patients with ischemic cardiovascular disease, keeping critically ill patients’ Hgb levels between 7.0 and 9.0 g/dL is as safe as keeping them between 10.0 and 12.0 g/dL.^3,9

Acute Bleeding: Is a Massive Transfusion Required?

The primary method to avoid the need for transfusing patients with acute hemorrhage is to stop the bleeding as soon as possible. Frequently, this is not possible and transfusion will be required. The question in these settings is: Does the patient require a “massive transfusion” (MT)? An MT means transfusing three units of packed red blood cells (PRBCs) per hour or five units PRBCs per 3 hours, and signifies uncontrolled hemorrhage, which requires a special transfusion protocol.¹⁰ (Note that the old, retrospective definition of MT, ≥10 PRBCs per 24 hours, is only useful for research.)

In most settings, two simple methods can determine whether a patient will require an MT: the Shock Index (SI) and the Assessment of Blood Consumption (ABC) Score, both of which are described below. In early hemorrhage, both the SI and the ABC Score are more helpful than inferior vena cava (IVC) measurements using ultrasound. The sensitivity of the dynamic IVC measures (collapsibility index and IVC end expiratory diameter) for detecting early blood loss is only around 80%.¹¹

Shock Index

Particularly useful in prehospital and other resource-poor settings, the SI (heart rate [HR]/systolic blood pressure [SBP]) helps indicate a need for MT in “relatively normotensive” blunt trauma patients with SBP ≥90 mm Hg.¹² As the SI increases >0.9, the probability of needing an MT increases incrementally; with an SI >1.4, 57% of patients need an MT. The SI’s sensitivity is equivalent to measuring the base deficit or lactate.¹³ Be careful with elderly patients: The need for MT may occur at much lower SIs. Their vital signs may not demonstrate the seriousness of their injury, as in the following examples.¹⁴

• 
  

  <70 years old: HR ≥130/min and SBP <90 mm Hg (SI = 1.4)

  
  
• 
  

  ≥70 years old may need a MT if: HR >90/min and SBP <110 mm Hg (SI = 0.8)

Assessment of Blood Consumption Score

ABC score is another method to determine need for MT. However, it requires using ultrasound for a FAST Exam. The four components of the ABC each receive 1 point if they are positive. The components are as follows:

1. 
   

   Penetrating mechanism of injury

   
   
2. 
   

   SBP ≤90 mm Hg

   
   
3. 
   

   HR ≥120/min

   
   
4. 
   

   Positive FAST examination

The ABC Score correctly classified patients as to whether they would need an MT if their score was 2 (82%), 3 (91%), or 4 (89%).¹⁵

Carrying O-Negative Blood in the Field

While relatively costly, both civilian and military medical units have shown that it can be safe and effective to carry and administer O-negative blood in the prehospital setting. The civilian units carry blood in special cold boxes (LifeBox50 Transport Containers; FareTec Inc, Painesville, Ohio, US), and the PRBCs are returned to the blood bank three times a week. In one large metropolitan civilian area, the EMS carried two units of “O-negative” PRBCs, of which they administered 26% to patients. Of the non-transfused units, they returned 98% to the blood bank in useable condition. The cost of providing PRBCs for civilian prehospital use was $500 to $700 for each unit transfused.¹⁶ In the laboratory, studies have showed that PRBCs can survive parachute jumps and mechanical agitation over 12 hours at 48°C (118°F) without significant changes in chemistry or morphology.¹⁷

“Damage Control” Transfusion

When an MT is indicated due to major trauma with continuing blood loss (or a severe head injury), use a transfusion protocol that not only promptly replaces erythrocytes, but also promptly treats coagulopathy. Use PRBCs, fresh-frozen plasma (FFP) and platelets immediately, in a 1:1:1 ratio. If platelets are unavailable, use PRBCs and FFP in a 1:1 ratio. Do not wait for abnormal laboratory test results. To be able to quickly implement this protocol, discuss it with the blood bank in advance, so that they are responsive to your needs.

Using this protocol increases 6-hour, 24-hour, and 30-day survival. The mortality at 24 hours and at 30 days was no different than with using a ratio of 1:1:2 (platelets, FFP, PRBCs).^18,19 That is unsurprising, because both higher FFP:PRBC ratios and higher platelet:PRBC ratios improve survival at 24 hours and at 30 days.²⁰

Whole Blood in Trauma Resuscitations

Most blood banks no longer have whole blood available for immediate transfusion, because this practice reduces the availability of blood components, while the unused whole blood units become outdated. The use of a “walking blood bank,” that is, donors available when called, provides this resource (see the “Walking Blood Bank” section in this chapter). The benefits of using fresh whole blood include increased volume, plasma’s coagulation factors, platelets, and the presence of circulating antibacterial substances.²¹

How to Determine Adequate Blood Replacement

If a patient has been adequately transfused after acute blood loss (assuming that the bleeding has ceased), the skin will become warm, dry, and, if the patient is Caucasian, pink. The nose will again be warm, and the capillary refill will be brisk (immediate). This is in contrast to the skin being cold, damp, and white, and having a delayed (not “brisk”) capillary refill when acutely anemic. These clinical results of transfusion may be delayed, especially if the blood loss was severe or prolonged. A urine output of ≥1 mL/kg/hour is also an excellent sign of adequate blood replacement.²²

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 Hct for the same volume of blood loss.¹ Because 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.²³

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 a 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.²⁴ At the conclusion of surgery or if there is an indication that a transfusion is necessary during the procedure, transfuse the collected blood into the patient.³ It is especially useful for hospitals with limited or no blood bank facilities.^25,26,27

Acute Normovolemic Hemodilution Procedure

At the onset of surgery in a stable patient who is not hemorrhaging, use a 14-gauge intravenous (IV) catheter in an antecubital vein to remove either 2 L of blood or enough blood so the Hct 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 formula²⁵:

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

  
  
• 
  

  H^avg = the average Hct = (H¹ + H²) ÷ 2

  
  
• 
  

  Example: 70 kg patient; Initial Hct = 35%; Target Hct = 28%

  
  
• 
  

  Volume to remove = (70 kg × 70 mL/kg) × [(.35 – .28) ÷ {(.35 + .28)/2}] = 1,089 mL

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 one unit is removed.)²⁷ If colloid is not available, use crystalloid for all replacements. If there is only one IV line, alternate the blood collection and the infusion of replacement fluids. If there are two IV lines, they occur simultaneously.²⁴ 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.²⁵

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.^24,25

Blood/Cell Salvage—Autotransfusion

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 a ruptured ectopic pregnancy, which is 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.²⁸ The techniques are also used for hemothoraces from penetrating chest injuries and for blunt abdominal injuries with hepatic or splenic bleeding.²⁹

What Blood to Use?

Use autologous transfusion only if blood can be removed from a cavity (usually the chest or abdomen) where it has been for <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.^4,24 Blood from contaminated abdominal wounds can be used, but with an increased risk of systemic infection.³⁰ 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, wait to transfuse until bleeding has been surgically controlled.

Technique: Abdomen