Comparison of simultaneously obtained arterial and capillary blood gases in pediatric intensive care unit patients.

Objective: To determine whether capillary blood gas measurements provide a clinically acceptable estimate of arterial pH, Pco 2 , and Po 2 . Design: Prospective convenience sample. Setting: Pediatric intensive care unit at a referral children's hospital. Patients: Fifty children >1 month of age with indwelling arterial catheters. Interventions: A local anesthetic was applied to the third finger of the hand contralateral to a radial artery catheter. After 90 mins, simultaneous arterial and capillary blood gases were drawn. Measurements and Main Results: Arterial and capillary pH, Pco 2 , and Po 2 were measured. Heart rate and Wong/Baker faces score were noted before and during capillary blood gas collection to assess discomfort associated with blood collection. There was a strong correlation between capillary and arterial pH (r 2 =.903, p 6.5 torr (>0.87 kPa). Despite a statistically significant correlation between capillary and arterial Po 2 (r 2 =.358, p 6.5 torr (>0.87 kPa) in 42 of 50 patients. Pain, endotracheal intubation, vasoactive drips, or pharmacologic paralysis did not affect accuracy of the capillary pH or Pco 2 . Concluslons: Capillary blood gases accurately reflect arterial pH and Pco 2 in most pediatric intensive care unit patients. Capillary samples did not significantly underestimate arterial hypercarbia or acidosis. This conservative reflection of metabolic status may be particularly useful in hemodynamically stable patients with mild-to-moderate lung disease.