Continuous monitoring of fetal pH, pO(2) and pCO(2) using a fiberoptic multiparameter sensor in animal models reproducing in utero conditions

Objectives: To evaluate the feasibility and accuracy of continuous fetal mo nitoring with a multiparameter intravascular sensor (MPIS) in animal models mimicking the fetal metabolic status. Methods: First, the accuracy of the MPIS in hypoxic conditions was tested in adult rabbits (n = 6). The carotid artery(n = 4) or vein (n = 2) was catheterized with a 20-gauge cannula, ho using a 500-mu m Neotrend(R) fiberoptic sensor for pCO(2), pO(2), pH and te mperature. Fiberoptic readings were compared with arterial blood-gas (ABG) analyses. Secondly, the feasibility of continuous fetal fiberoptic sensing was tested during experimental fetoscopic surgery in lambs (n = 4). An iden tical sensor was introduced in a chorionic artery and readings were compare d to ABG analyses of fetal blood samples. Results: The overall bias and pre cision in the first experiment (147 measurement pairs) were -4.2 and 10.9 m m Hg for pO(2), +1.6 and 8.2 mm Hg for pCO(2) and -0.015 and 0.031 for pH, respectively. In the sheep experiments, continuous readings for all paramet ers were only available during 50% of the operation time, mainly due to dis turbances induced by movement, contact with vessel wall and interference by endoscopic light. 20 sample pairs were obtained resulting in an overall bi as and precision of -3.9 and 4.3 mm Hg for pO(2), -0.74 and 3.68 mm Hg for pCO(2) and -0.0032 and 0.02 for pH. Conclusions: fiberoptic microsensors ar e potentially useful for monitoring acid-base status in the low pO(2) range present in fetal life. Copyright (C) 2000 S. Karger AG, Basel.