Telemetric monitoring of fetal blood pressure and heart rate in the freely moving pregnant sheep: a feasibility study

Abstract

Remote telemetric monitoring of fetal haemodynamics in pregnant sheep would allow unrestricted animal movement, minimize suffering and distress, and improve animal welfare, while enhancing the quality of data collected. This may also be useful in clinical practice following fetal surgery. Using an open fetal surgical technique at approximately two-thirds of gestation, we implanted the catheter of a D70-PCTP haemodynamic telemetric device (Data Sciences International, Tilburg, The Netherlands) into the carotid artery of the fetal sheep (n = 4). The attached transmitter was secured to the posterior aspect of the maternal anterior abdominal wall. Two receivers, with a range of 1 m each, were sited in an 11 m² sheep enclosure to maximize animal freedom while allowing continuous monitoring of the ewe. The receivers were connected by cable to a nearby computer. In the first two procedures, both fetuses died eight and 12 days after surgery, and the catheter tip was observed to be lying in the bicarotid trunk. In the next two procedures the catheter tip was threaded further upstream from the insertion point, in an attempt to reach the fetal aorta, and both fetuses survived until the scheduled postmortem examination at the end of pregnancy. After catheter implantation, fetal blood pressure (BP) and heart rate (HR) were successfully recorded continuously for seven days and then hourly per day for a further three weeks. The fetal BP and HR values were in the normal range for healthy sheep fetuses.

Long-term increase in uterine blood flow is achieved by local overexpression of VEGF-A165 in the uterine arteries of pregnant sheep

“…Fetal catheter implantation was accomplished using an open fetal surgical technique at 101.25±0.25 days of gestation, where we implanted the catheter of a D70-PCTP hemodynamic telemetric device (Data Sciences International) into the carotid artery of the fetal sheep (n ¼ 4). 54 Vector injection was performed as described above 6 --8 days later.…”

Doppler sonography for evaluation of hemodynamic characteristics of fetal umbilicus in Beetal goats

“…With this non-invasive technique (Doppler ultrasonography) umbilical artery and venous blood flow pattern were investigated. Only recently, a trans-abdominal approach for Doppler evaluations in anesthetized animals fixed in recumbency has been reported [ 11 ]. Experiments were done twice during gestation, after midline laparotomy, surgical mobilization of the uterine arteries and placing a transit-time ultrasonic flow probe around the uterine artery supplying the pregnant horn [ 11 , 12 ].…”

“…Only recently, a trans-abdominal approach for Doppler evaluations in anesthetized animals fixed in recumbency has been reported [ 11 ]. Experiments were done twice during gestation, after midline laparotomy, surgical mobilization of the uterine arteries and placing a transit-time ultrasonic flow probe around the uterine artery supplying the pregnant horn [ 11 , 12 ]. Color Doppler ultrasonography had been done to characterize blood flow pattern during entire pregnancy in Boer × German improved fawn goat [ 13 ]; however, no information is available on blood flow to uterus and developing fetus in tropical breeds.…”

Evaluation of fetal exposure to external loud noise using a sheep model: quantification of in utero acoustic transmission across the human audio range

“…In an area of myometrium away from placentomes, a 5 cm uterine incision was performed over the fetal head which was then exteriorized through the uterine incision. 19 Babcock clamps were used to compress the amniotic membrane against the uterine wall in order to minimize bleeding and reduce amniotic fluid loss. A calibrated hydrophone was sutured to the occiput of the fetal head and cabling was secured to the posterior aspect of the fetal neck using 2.0 Prolene (Ethicon, Ohio, USA).…”

“…The uterine incision was closed in two layers as described. 19 The cabling from the hydrophone was then exteriorized onto the ewe's right flank and secured to the skin. Antibiotics for infection prophylaxis and analgesia were given to the ewe at the end of the procedure as described 19 .…”