Objectives: To evaluate the feasibility and accuracy of continuous fetal monitoring 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, housing a 500-microm Neotrend((R)) fiberoptic sensor for pCO(2), pO(2), pH and temperature. 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 identical sensor was introduced in a chorionic artery and readings were compared to ABG analyses of fetal blood samples.
Results: The overall bias and precision in the first experiment (147 measurement pairs) were -4.2 and 10.9 mm 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 parameters were only available during 50% of the operation time, mainly due to disturbances induced by movement, contact with vessel wall and interference by endoscopic light. 20 sample pairs were obtained resulting in an overall bias 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 are potentially useful for monitoring acid-base status in the low pO(2) range present in fetal life.
Copyright 2000 S. Karger AG, Basel