A new device for the aspiration of follicular fluid for acid-base balance analysis in cattle

The aim of this study was to evaluate a new device for the ultrasound-guided transvaginal aspiration of follicular fluid for acid-base balance analysis (ABB set) in comparison with the original modified commercial OPU set. In the ABB set, an aspiration syringe was placed in the front part of the new tool's handle, next to the transducer, so as to enable direct collection of the sample into the syringe. To obtain a sufficient amount of testable fluid, reservoirs of urine (rubber balloons) were used for later aspiration under laboratory conditions in Experiment 1. Fifteen triads of samples (each triad with two punctures) were collected. While the first sample of each triad was taken using the ABB set (ABB sample), two samples were taken by one puncture using the original modified commercial OPU set: aerobic phase of sampling (AE sample) with air present in the tubing at the start of sampling and the subsequent anaerobic phase of sampling (AN sample). Values determined in the second sample from the triad (AE) varied from the values in both ABB and AN samples (pH 7.685 vs. 7.704 vs. 7.692, pCO2 11.13 vs. 10.3 vs. 10.85, pO2 6.87 vs. 8.67 vs. 7.02). In Experiment 2, ultrasound-guided transvaginal aspirations were carried out in 13 cows bearing ovarian cysts with diameters of at least 3 cm, using plastic aspiration syringes (Experiment 2P) and in 12 cows using glass aspiration syringes (Experiment 2G). The sequence of samples was the same as in Experiment 1. We found a significantly higher pH in AE in comparison to AN (7.357 vs. 7.348), lower pCO2 (6.85) and higher O2 (14.12) in samples of AE in comparison to samples of ABB and AN (pCO2 7.36, 7.30; O2 9.95, 10.63 respectively) in cystic fluid in Experiment 2P. We found a significantly higher pH (7.4), lower pCO2 (5.98) and a higher pO2 (12.35) in AE samples in comparison to ABB and AN samples of cystic fluid (pH 7.386, 7.385; pCO2 6.39, 6.35 and O2 10.56, 10.65, respectively) from Experiment 2G. We conclude that the acid-base balance assay was affected by air, present in the tubing during aerobic sampling in comparison to anaerobic and ABB set sampling. These pre-analytical changes can be prevented by the use of the ABB set because the results obtained with the ABB set were not different from that of the AN samples. We also confirmed pre-analytical changes in acid-base balance parameters in the cystic fluid after it had been stored in plastic aspiration syringes. Our new ABB set equipped with a glass aspiration syringe is suitable for sampling follicular fluid for both acid-base balance and gas analysis.