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The umbilical cord (UC) is a vital connection between fetus and placenta. It constitutes a stable connection to the fetomaternal interface, while allowing the fetal mobility that is of great importance for fetal development in general and fetal neuromotor development in particular. This combination of mechanical stability and flexibility is due to the architecture of the UC. There is however a range of umbilical cord complications that may be life threatening to the fetus and these too can be explained to a large extent by the cord's structural characteristics. This review article discusses clinically relevant aspects of UC ultrasound.

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Chorioamniotic membrane separation (CMS) comprises cases of spontaneous and iatrogenic detachment between the amniotic and chorionic membranes, with various fetal outcomes due to possible complications, particularly the formation of constrictive amniotic bands and preterm rupture of membranes. In the absence of mandatory management standards conservative monitoring is the most reported approach. In the case we present here, close sonographic surveillance afforded us the opportunity to observe the process from CMS to amnion rupture with the formation of constrictive amniotic bands and threatened cord impairment via constrictive margins of the amniotic sac. Despite the complicated background of reduced membranous layers in ruptured CMS, we performed a successful fetoscopic intervention with band release at 24 weeks' gestation and the pregnancy was prolonged to 34 weeks under close monitoring.

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Fetal malformations are detected early in pregnancy by means of ultrasound challenging fetal therapy. While open fetal surgery has been preformed during preliminary clinical trials we evaluated fetoscopic therapy avoiding laparotomy and uterotomy. We used a laser fibre (900 mu) which was introduced into the uterus by an endoscope. During animal experiments in five fetal lambs with a gestational age of 120-122 days we used an excimer laser (Technolas, x) with a wave-length of 308 nm. Laser incisions were compared with the conventional cutting technique using a scapel. During histological evaluation the tissue effect was morphometricly analysed. The zone of devitalisation was characterized by pycnosis of the nuclei and in a change of cytoplasma volume. The excimer laser incisions using a frequency of 40 HZ had a mean zone of devitalisation of 50.3 +/- 4.5 mu. Using the excimer laser with a frequency of 10 HZ we found a tissue alteration of only 11.2 +/- 3.4 mu. The incisions by scapel showed a extended traumatisation with a mean tissue effect of 153.2 +/- 16.3 mu. From these results we conclude, that endoscopic surgery may be come a usefull additional tool for fetal therapy.

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The noninvasive determination of biochemical parameters has become an important aspect of intensive care medicine. The newly developed monitors for laser reflectometry provide the possibility of spectroscopic monitoring. The equipment consists of a near-infrared data collection unit and a personal computer. The four laser diodes emit light at wavelengths of 775, 805, 845 and 904 nm. By analyzing the changes in optical density during laser irradiation of biological tissue, information is obtained about the relative changes in the concentration of hemoglobin and the blood volume. In animal experiments with ten fetal lambs we evaluated the reliability of near infrared laser spectroscopy. Fetal hyperoxia was achieved by means of an extracorporeal circuit with interposition of a membrane oxygenator (0.8 m2, Scimed). During the induced hyperoxia the laser spectroscopic tracings showed a rise in the HbO2 signal with a synchronous decrease in the HbR signal. Additionally, the spectroscopic pattern showed a characteristic initial rise in the intracerebral blood volume, which stabilized after 4 minutes. We found a significant correlation between the intermittently measured PO2 values of the arterial blood samples and the laser spectroscopic HbO2 and HbR signals (r = 0.87, and r = -0.82, respectively; p less than 0.001). Furthermore, hyperoxia was indicated by the laser system with a short lag time. We conclude that laser spectroscopy is a reliable method with a high potential for clinical routine use in intensive care, as it provides noninvasive continuous information at comparatively low costs using portable monitors.

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In order to evaluate the influence on the fetal brain due to compression of the umbilical cord biochemical and biophysical changes were traced during defined occlusions of 60 sec by means of NIR laser spectroscopy. Synchronously blood samples were drawn intermittently from a catheter positioned in the A. carotis and analysed for blood gases. The saturation values measured in the fetal blood correlated significantly with the dates of the HbO2 tracing of the NIR-system (r = 0.81, p less than 0.001). After induced occlusion of the umbilical cord a reproducible pattern of the NIR tracing occurred. While an immediate fall in HbO2 occurred, a synchronous rise in desaturated Hb was observed. For the changes of the cytochrome aa3 we detected a minor decrease that occurred with a lag time. Additionally there was an indication of a major change of blood volume as the total Hb content augmented during each compression. We concluded: Changes of Hb-saturation in the fetal blood are immediately indicated by NIR-laser spectroscopy. During cord occlusion of 60 sec. the intracellular oxygenation decrease only after a significant lag time and are reversible and furthermore it leads to a reproducible change of intracerebral blood volume.

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During an animal study using five bastard dogs the hemodynamic relations during extracorporeal perfusion with an arteriovenous circuit and extracorporeal CO2 removal (ECCO2-R) were analyzed. We utilised a prototype circuit (Promed, West-Germany) which is by diminution and using silicon rubber adapted to the application in newborn. A silicon lung (Scimed, 0.8 m2, ECCO2-R) was used in the circuit. During the six hours perfusion period a main arterial blood pressure of 83 +/- 17 mmHg and an extracorporeal blood flow of 412 +/- 56 ml/min was found using arteriovenous perfusion via the femoral artery and vein. We found a statistical significant correlation (r = 0.66) between the main arterial blood pressure and the extracorporeal blood flow. Further more there was a significant correlation between the arterial PCO2 and the blood flow through membrane lung (r = 0.81). In conclusion our animal experiments approved the possibility of hemodynamic adaptation to an arteriovenous circuit as well as effectiveness of CO2 removal via such circuit.

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During twenty animal experiments the effectiveness of the gas exchange during extracorporeal membrane oxygenation (ECMO) was evaluated. Arteriovenous, venovenous and venoarterial perfusion systems were compared. While PO2 saturation values were sufficient in all three groups the PO2 values were significant higher during arteriovenous perfusion (84.22 +/- 3.5 mmHg) compared to venovenous 71.99 +/- 7.3 mmHg) and venoarterial (65.11 +/- 4.5 mmHg) perfusion (p less than 0.001). PCO2 values correlated with the flow in the extracorporeal circuit in all three groups. The absolute values of PCO2 were significantly lowest during venoarterial perfusion (39.68 +/- 3.1 mmHg) compared to the venovenous (42.69 +/- 3.3 mmHg) and the arteriovenous mode (49.96 +/- 4.1 mmHg). These results indicate that perfusion circuits other than the original venoarterial ECMO could provide sufficient gas transfer for respiratory insufficient neonates while avoiding points of criticism of such systems.

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