Schwartz J B, Cheng M H, Ramos A D, Merritt R J, Platzker A C
Division of Neonatology and Pediatric Pulmonary, University of Southern California School of Medicine, Childrens Hospital of Los Angeles.
J Perinatol. 1990 Dec;10(4):376-9.
Plasma ammonia concentration in neonates has routinely been determined using arterial or venous blood. Expected plasma ammonia values in capillary blood obtained by heelstick have not been determined. We compared ammonia levels in 20 sets of plasma from simultaneously drawn arterial, venous, and capillary blood in a group of neonates receiving total parenteral nutrition. Mean ammonia concentrations in venous (107 +/- 44) and capillary blood (112 +/- 33) were 45% and 51% higher, respectively, than corresponding arterial (74 +/- 22) values (P less than .001). Ammonia levels in blood obtained by venipuncture (Ven), however, did not correlate consistently with arterial (Art) values (r = .43; Art = 51 + 0.21 Ven; P greater than .05). In contrast, ammonia levels in capillary blood (Cap) correlated well with arterial values (r = .86; Art = 10.3 + 0.6Cap; P less than .001). Ammonia levels in neonates may be reliably interpreted using the latter regression equation when blood for analysis is obtained by a properly performed heelstick, allowing the preservation of arteries and veins, and sparing the infant from repetitive needle punctures. Ammonia levels in blood obtained by venipuncture do not adequately correlate with arterial values and therefore may be therapeutically misleading.
新生儿血浆氨浓度通常采用动脉血或静脉血进行测定。足跟采血获取的毛细血管血中血浆氨的预期值尚未确定。我们比较了一组接受全胃肠外营养的新生儿同时采集的动脉血、静脉血和毛细血管血中20组血浆的氨水平。静脉血（107±44）和毛细血管血（112±33）中的平均氨浓度分别比相应的动脉血（74±22）值高45%和51%（P＜0.001）。然而，静脉穿刺获取的血液中的氨水平与动脉血值并不始终相关（r = 0.43；动脉血值=51 + 0.21×静脉血值；P＞0.05）。相比之下，毛细血管血中的氨水平与动脉血值相关性良好（r = 0.86；动脉血值=10.3 + 0.6×毛细血管血值；P＜0.001）。当通过正确操作的足跟采血获取用于分析的血液时，使用后一个回归方程可以可靠地解读新生儿的氨水平，这样可以保留动脉和静脉，避免婴儿反复接受针刺。静脉穿刺获取的血液中的氨水平与动脉血值相关性不足，因此可能在治疗上产生误导。
