Does red blood cell transfusion change the near infra red photoplethysmography signal in infants?

Abstract

Objective: Transfusion practices for neonates are controversial and based on limited scientific information. We examined the use of the plethysmographic volume pulse to assess anemia.

Design: We used near-infrared photoplethysmography (NIRP) to investigate signal strength parameters as area under the curve (AUC) and the first derivate of the amplitude (flux) in anemic infants before and after elective transfusion.

Setting: Tertiary intensive care unit.

Patients: Thirty-four neonates on day 25+/-15 of life with a pretransfusion hemoglobin level of 8+/-0.9 g/dl. Four infants were excluded for incomplete data.

Interventions: Transfusion of 10 ml packed red cells per kilogram body weight

Measurements and results: The volume pulse signal was obtained with a sensor attached to the sole of the foot. After transfusion we found a significant decrease in number of bradycardia episodes per hour (0.35 vs. 0.16) and episodes of pulse oximeter desaturation less than 85% per hour (1.8 vs. 1.3) and a significant increase in daily weight gain (12+/-7 vs. 20+/-18 g), but neither of the microcirculatory parameters changed significantly (AUC 102+/-38 vs. 101+/-44; flux 435+/-160 vs. 405+/-120).

Conclusions: Even though infants were transfused at very low levels of hemoglobin with significant clinical effects, microcirculation assessed by NIRP seemed not be affected. Infrared photoplethysmographs present flow not only in the nutritive capillaries but mainly in the subpapillary plexus at a greater depth. This thermoregulatory flow seems not be affected by blood transfusions of anemic infants.