To obtain capillary blood samples that provide accurate laboratory results with minimal discomfort and potential for injury/infection.

Capillary blood sampling is the most frequently performed skin-breaking procedure in neonatal intensive care units (1). It is an easily mastered, minimally invasive procedure that, when performed with proper technique and equipment, provides laboratory results that are comparable to arterial samples (2, 3). The only exception to this is a complete blood count (CBC), where capillary samples have a higher hemoglobin (Hgb), hematocrit (Hct), red blood cell (RBC) count, and white blood cell (WBC) count when compared to venous samples (4). The advantage of capillary sampling is that repeated testing may be carried out, and peripheral veins may be saved for IV access.

1. Venous or arterial blood rather than capillary samples should be used for

a. Blood cultures, which require sterile technique

b. Tests in which even a minimal amount of hemolysis will compromise results

c. Special tests such as coagulation studies (newer coagulation tests that require only a few drops of blood are still not widely available)

d. Laboratory tests that require more than 1.5 mL of blood

1. Automated heel-lancing device: Encased, springloaded, retractable blade that provides a controlled and consistent width and depth of incision for blood testing.

a. Incision depths range from 0.65 to 2 mm for micropreemies through toddlers (Tenderfoot, International Technidyne Corporation, Edison, New Jersey) and from 0.85 to 1 mm for preemies and newborns (BD Quikheel Lancet, BD Vacutainer Systems, Franklin Lakes, New Jersey) (see Table 18.1).

b. The controlled depths avoid damage to the calcaneus (6, 7, 8) while providing greater yield with less pain, hemolysis, and laboratory-value error (6, 9). The shallower devices can be used to obtain small samples from larger infants who require frequent point-of-care glucose testing (10).