COMPARISON OF SIMULTANEOUSLY OBTAINED ARTERIAL AND CAPILLARY BLOOD-GASES IN PEDIATRIC INTENSIVE-CARE UNIT PATIENTS

Objective: To determine whether capillary blood gas measurements provi de a clinically acceptable estimate of arterial pH, Pco(2), and Po-2. Design: Prospective convenience sample. Setting:Pediatric intensive ca re unit at a referral children's hospital. Patients: Fifty children >1 month of age with indwelling arterial catheters. Interventions: A loc al anesthetic was applied to the third finger of the hand contralatera l to a radial artery catheter. After 90 mins, simultaneous arterial an d capillary blood gases were drawn. Measurements and Main Results: Art erial and capillary pH, Pco(2), and Po-2 were measured. Heart rate and Wong/Baker faces score were noted before and during capillary blood g as collection to assess discomfort associated with blood collection. T here was a strong correlation between capillary and arterial pH (r(2) =.903, p<.0001). The relative average bias of the capillary pH was 0.0 09, with capillary lower than arterial and 95% limits of agreement of +/-0.032. In all patients, the absolute value of the difference betwee n arterial and capillary pH was less than or equal to 0.05. There was a strong correlation between arterial and capillary Pco(2) (r(2) =.955 , p< .0001). The relative average bias of the capillary Pco(2) was 1.6 torr (0.21 kPa), with capillary higher than arterial and 95% limits o f agreement of +/-4.5 torr (+/-0.6 kPa). In two of 50 patients, the ab solute value of the difference between arterial and capillary Pco(2) w as >6.5 torr (>0.87 kPa). Despite a statistically significant correlat ion between capillary and arterial Po-2 (r(2) =.358, P <.0001), the ab solute value of the difference between arterial and capillary Po-2 was >6.5 torr (>0.87 kPa) in 42 of 50 patients. Pain, endotracheal intuba tion, vasoactive drips, or pharmaco logic paralysis did not affect acc uracy of the capillary pH or Pco,. Conclusions: Capillary blood gases accurately reflect arterial pH and Pco(2) in most pediatric intensive care unit patients. Capillary samples did not significantly underestim ate arterial hypercarbia or acidosis. This conservative reflection of metabolic status may be particularly useful in hemodynamically stable patients with mild to moderate lung disease.