How to draw blood from the baby's foot

We all know that although blood drawing is simple, it is not an easy task to draw blood successfully from newborns, produce qualified blood smears, and ensure the quality of blood smears. Therefore, strict requirements must be set and blood collection must be standardized. In the five years of blood collection for neonatal disease screening in our hospital, we have continuously selected effective blood collection points on the inner and outer edges of the neonatal heels, summarized the lessons learned in the blood collection process, improved the success rate of one-time blood collection, and achieved certain results. The blood collection method and operation are reported as follows.

1 Clinical Data

Data from blood sampling for neonatal disease screening in our hospital since 2008 were collected. From January 2010 to January 2012, blood was collected from 1,856 newborns aged more than 72 hours without other complications, with an average weight of 3,186 g and who had been fully breastfed for more than 8 times. 1,793 cases were successful, with a success rate of 96.6%, and 63 cases failed, accounting for 3.4%. Failure was caused by improper position selection in 14 cases, accounting for 22.2%. Insufficient preparation before blood collection resulted in 49 failures, accounting for 77.8%.

2 Methods

2.1 Blood collection method

2.1.1 Blood sampling time: After the newborn has been fully breastfed for 8 times, bathe with warm water at 38℃-39℃ in winter and 37℃-38℃ in summer, gently touch the newborn's heel, and draw blood when the heel is engorged and rosy.

2.1.2 Preparation of the environment before blood collection: Indoor air is disinfected with an ozone disinfector for 30-60 minutes, the indoor neutral temperature is 24℃-25℃, and the relative humidity is 55%-60%［2］. Items: blood collection card, sterile blood collection needle, 75% alcohol cotton ball or cotton swab, sterile talc-free gloves. The operator washes his hands and wears a mask, hat and gloves.

2.1.3 Note: The following areas cannot be used for newborn screening blood collection: first, the bend of the heel; second, the arch of the foot; third, the center of the heel; fourth, the edema area; and finally, the fingers (the distance from the skin at the end of a newborn's finger to the finger bone is 1.2-2.2mm. Blood collection at this site can easily damage the bones. Local infection and necrosis are complications of finger blood collection). Blood sampling from the first three parts can easily cause damage to the newborn's nerves, tendons, ligaments and cartilage, resulting in certain sequelae.

2.2 Blood sampling site Based on the experience of blood sampling for neonatal disease screening at home and abroad, the medial and lateral edges of the heel are ideal sites for blood sampling［3］. However, the range is too large to accurately locate the point. In our clinical work, we draw a vertical line from the posterior side of the lateral malleolus to the sole of the foot. The intersection of the vertical line and the lateral edge of the sole is the ideal puncture point.

3 Operation

3.1 Operation method

3.1.1 Locate the site and perform puncture for blood collection. First, place the newborn on the operating table in a supine position, raise the newborn's head, and make the soles of the feet lower than the level of the heart to increase the venous pressure and increase the amount of blood reaching the puncture site. The second is to disinfect the inner and outer edges of the heel with 75% alcohol. The diameter should be more than 3cm. Use a dry cotton swab to wipe off the residual alcohol before starting the operation. Then the nurse gently holds the newborn's foot with her left hand, tightens the skin at the blood collection site, and holds the blood collection needle in her right hand to puncture the blood collection site on the heel with a depth of less than 3 cm. (Based on clinical work experience, the most ideal puncture point for heel blood sampling is the intersection of a vertical line drawn from the lateral side of the ankle to the lateral edge of the heel and the lateral edge of the sole of the foot).

3.1.2 Preparation of blood collection card After puncture, let the blood flow out naturally, then gently wipe off the first drop of blood with a sterile cotton swab to avoid mixing of blood and tissue fluid and causing unqualified blood samples. Then gently squeeze and relax around the puncture site, and when the blood drop is large enough, lightly touch the blood drop with the front of the blood collection card to allow the blood to be naturally absorbed and penetrate into the back of the filter paper, ensuring that the front and back sides of the filter paper are evenly penetrated. Three blood spots were collected consecutively, each of which was larger than 8 mm.

3.1.3 Local treatment after blood collection: Lift the newborn's feet and lay them flat on the operating table. Use a non-fine cotton swab to gently press the needle hole until the bleeding stops. Do not use adhesive tape.

3.1.4 Blood sampling is qualified by collecting three blood spots at a time. The diameter of the blood spots should be greater than 8mm and the front and back sides of the filter paper should be evenly penetrated.

In fact, the success rate of neonatal blood collection is high, which reduces the pain caused to newborns by repeated punctures. Parents' satisfaction with this puncture technology has been greatly improved, so that congenital and hereditary diseases of newborns can be treated in time, and the children's intelligence and quality of life can be improved. Second, the blood collection site: In clinical work, we found that directly inserting the needle vertically from the inner and outer edges of the heel is prone to penetrate too deep, and the needle can easily reach the subcutaneous fat layer where there are relatively few capillaries.