Monitoring critically ill newborn infants with digital capillary blood samples: an alternative.

Capillary blood samples obtained from a warmed distal phalanx of the right hand were compared with either temporal or right radial arterial blood samples for PO2, PCO2, and pH in 33 critically ill newborn infants. The blood pressure and skin temperatures of each infant and the ambient oxygen concentration were recorded at the time the blood was sampled. Sixty-eight paired PO2 analyses yielded a regression line close to the line of identity. The mean difference between digital capillary and arterial PO2 was 11.3 +/- 1.4 mm Hg (r = 0.92). The results were similar for the paired PCO2 analyses (r = 0.84) and for the paired pH analyses (r = 0.94). The correlation between arterial PO2 and digital capillary PO2 deteriorated when the systolic blood pressure of the patient was below 35 mm Hg. There was no correlation between skin temperature and capillary-arterial PO2 differences. The frequency of retrolental fibroplasia leading to blindness was not different from that in nurseries that sample umbilical arterial blood routinely.