Chapter 11

### Key Points

1. Typical transfusion thresholds include a hematocrit of 21% in asymptomatic patients, and 30% in critically ill premature neonates or patients undergoing major surgery.

2. Patients with sickle cell disease (SCD) require strict physiologic optimization preoperatively, and close monitoring after surgery, to prevent complications.

3. A platelet count of 50,000/mm3 is adequate for procedures such as central line placement.

4. For massive transfusion, a blood component ratio of 1:1:1 for red blood cells (RBCs): fresh frozen plasma (FFP): platelets is recommended.

5. Most transfusion reactions typically fall into one of 3 categories: hemolytic, febrile, and urticarial.

Hematologic abnormalities are frequently encountered in the ill pediatric patient. Many excellent reviews of the physiology and pathophysiology of blood disorders and coagulation are currently available. This chapter is designed to complement rather than replace them. The goal is to provide a practical guide for the practicing surgeon and to aid in the formulation of diagnostic and treatment algorithms for the care of actual patients.

### Anemia

In the strictest sense, anemia is defined as a hemoglobin value or hematocrit level that is below 2 standard deviations from the mean for a given patient's age and sex. This definition, however, does not serve to identify those patients with clinically significant reductions in RBC mass, which is usually defined as the level at which tissue oxygenation is compromised. In fact, most decisions to transfuse RBCs are based on clinical judgment, currently available clinical and experimental data, accepted clinical guidelines, and personal experience.

The range of “normal” hematocrit levels for a particular age group can be rather broad. Likewise, the acceptable minimum hematocrit for any given patient is variable. In general, red cell transfusion is not considered in an otherwise healthy asymptomatic child until the hematocrit is less than approximately 21% (hemoglobin <7.0 g/dL). Even this is not an absolute indication for transfusion, as we have seen healthy children tolerate levels less than this with minimal physiologic embarrassment. Furthermore, in stable critically ill children, a recent randomized controlled trial demonstrated that a hemoglobin level of 7 g/dL is feasible as a transfusion threshold without affecting outcome. Some children with chronic anemia (eg, chronic renal insufficiency) have established compensatory mechanisms to such a degree that they can tolerate hematocrit levels much lower than those stated above. On the other hand, children with a hematocrit value higher than a minimally acceptable standard but who are clinically compromised may require transfusion regardless of the absolute hematocrit.

Newborns have a hematocrit value that normally varies between 47% and 60% but gradually decreases to a “physiological nadir” at approximately 2 to 3 months of age. This value can be as low as 28% in healthy infants. This nadir also coincides with the normal replacement of fetal hemoglobin (HbF), the predominant form in neonates, with the adult type. HbF has a higher affinity for oxygen and demonstrates a relative left shift of the oxygen–hemoglobin dissociation curve. Congenital hemoglobinopathies affecting the adult form of hemoglobin (eg, sickle cell anemia, thalassemia, etc) typically become clinically apparent after 2 to 3 months, when most of the unaffected HbF has been replaced with the defective adult form. Healthy newborns are not transfused unless they are clinically compromised by a low hematocrit. Critically ill neonates, especially premature infants, are often empirically transfused to hematocrit levels of 30% or higher depending on the clinical scenario.

There are accepted indications for empiric blood transfusion in the setting of acute blood loss typically encountered in the trauma bay or operating room. Most protocols suggest transfusion for acute losses ...

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