Pulse oximetry: an improved in vitro model that reduces blood flow-related artifacts.

Artifacts may occur in many in vitro models of pulse oximetry due to the optical effects of synchronously oriented and/or deformed erythrocytes. Although these artifacts are most likely negligible in living superficial tissues, they are demonstrated to have considerable influence on the calibration curve obtainable from the in vitro simulation of pulse oximetry in such models, especially at low oxygen saturations. Therefore, we have developed a modified in vitro model which reduces the effect of these artifacts. This is achieved by excluding data obtained during pressure transients and by raising the blood flow velocity. As a result, the model more closely approximates in vivo pulse oximetry, particularly under clinically important conditions of low blood oxygen saturation levels.

[Possibilities and applications of pulse oximetry during labor]. / Mozliwosci i zastosowanie pulsoksymetrii podczas porodu.

Fetal pulsoxymetry gives the opportunity of constant registration of oxygen saturation in the fetus during delivery. Important changes of the utilized equipments are crucial for proper assessment of this parameter. Construction of the sensors is of special importance. A good fixation of the sensors is prerequisite for the avoidance of artefacts. So far this procedure has not been used for diagnosing threatened fetal hypoxemia. Recent clinical research shows that the above method reflects a good state of the fetus if only good quality of signal and constant high saturation is maintained. That is why the method helps in the case of suspicious cardiotocographic records. Besides the application in fetal arrhythmias, the method can be used to decrease the number of blood gas analyses. The quality of pulsoxymetry should be confirmed by prospective studies in the nearest future.

Telemedicine: application of telepathology-remote microscopy for intraoperative diagnoses on frozen sections.

Due to the time delay, intraoperative consultations result in an extension of operation times, leading to prolonged anesthesia and idle time during surgery. Using a remote controlled microscope for telepathology, transfer times between hospital and pathologist can be eliminated and pathological expertise obtained independently of the geographic location of the hospital. In cooperation with a community hospital located 100 km apart from the Institute of Pathology of the Justus Liebig University Giessen, telepathological intraoperative consultations have been performed since 1999. After preparation and staining of the cryosection in the hospital, the slide was examined in our institute using a remote-controlled microscope (Leica DMRXA) and a special telepathological software (Leica TPS1). Data were transferred via two ISDN connections in parallel. The telepathology system contains an additional macroscopic examination equipment. Up to now more than 40 telepathological consultations have been done. Time required for the microscopic diagnosis ranged between 4 and 25 minutes. The amount of time saved, compared to the transfer to the next available pathologist, was approximately 45 minutes. In our experience, telepathological diagnoses were fully in accordance with conventional diagnoses routinely performed afterwards. The application of telepathology can lead to a significant shortening of surgery time if a pathologist is locally not available. In the study presented, no diagnostic errors occurred. The additional application of a macroscopic equipment allows inspection and interactive guidance for sampling, thus preventing sampling errors.

[Conservative treatment of ectopic pregnancies and presentation of a complicated case of peritonitis due to methotrexate]. / Konservative Behandlungsmöglichkeiten ektoper Schwangerschaften und Präsentation eines komplizierten Verlaufes mit einer Peritonitis unter Methotrexat.

Due to the improvement of diagnostic procedures and the refinement of endoscopic methods, the treatment of ectopic pregnancy has more and more turned against salpingectomy and towards organ-preserving actions. Moreover, for some years a range of medical therapies has been offering an alternative to surgical intervention. In addition to presenting a review of conservative methods of treatment, we report on a patient with an angular pregnancy who was treated with methotrexate and developed a pronounced peritonitis.

[Prevalence and follow-up of hepatitis C virus infection in pregnancy]. / Prävalenz und Verlauf der Hepatitis-C-Virusinfektion in der Schwangerschaft.

Hepatitis C shows an increasing distribution in countries of western Europe. The aim of our study was to assess the prevalence of antibodies to hepatitis C (anti-HCV) in pregnancy, to evaluate the risk factors for anti-HCV positive women and the course of hepatitis C during pregnancy. 3712 pregnant patients of the university hospital Grosshadern, Munich, were analyzed for anti-HCV, anti-HIV and hepatitis B surface antigen. Anti-HCV seropositive women were further tested with western blot and polymerase chain reaction for HCV-RNA. Thirty-five (0.94%) of the 3712 pregnant women were found anti-HCV positive. 20% of them had present or previous injection drug abuse, hereof one patient had an associated seropositivity for HIV. Parenteral transmission through blood transfusion was likely in 11%. However, no parenteral exposure was recognized in 57% of the anti-HCV positive patients. The presence of serum HCV-RNA was detected in 16 (57%) of the 28 patients tested. In 17% (6/35) of the anti-HCV positive pregnancies elevated liver enzymes were noted, which did not show any significant change during the course of pregnancy. In conclusion, the prevalence of hepatitis C in pregnancy is relatively high with nearly 1%-comparable to chronic hepatitis B infection. Selected pregnancy screening based on perceived high-risk groups alone fail to detect about 60% of HCV antibody-positive women. Pregnancy did not influence the course of hepatitis C.

Pulmonary embolism during labor and the effect on the fetus monitored with oxycardiotocography.

We report on a rare case of pulmonary embolism which we observed in the second stage of labor. For fetal surveillance we used oxycardiotocography (OCTG), an experimental system which combines internal CTG and pulse oximetry which enabled us to observe hemodynamic reactions of the unborn child and the effect on maternal-fetal gas exchange. It was possible to record marked fetal bradycardia simultaneously with decrease in oxygen saturation in the fetal arterial system during the acute event.

Fetal pulse oximetry: influence of tissue blood content and hemoglobin concentration in a new in-vitro model.

OBJECTIVE: To assess the influence of the blood content of the tissue and the hemoglobin content of the blood upon pulse oximetry at oxygen saturation ranges that commonly occur in the fetus during birth. METHOD: A new in-vitro model, which differs conceptually from models used by other authors, was developed to simulate the tissue. Our sensor measured absorption changes in red (640 nm) and infrared (880 nm) light as the blood concentration in the optical chamber changed in analogy to arterial pulsations. RESULTS: Blood content of the tissue and hemoglobin content of the blood both affect the pulse oximetric measurement adversely, especially at low oxygen saturations. Our simulations indicate, for example, that at a true oxygen saturation (SaO2) of 30%, a blood content change from 10 to 6 vol% would cause an underestimation of SaO2 by more than 16% points. CONCLUSION: Pulse oximetry at low saturations should take the blood content of the tissue and hemoglobin content of the blood into account in order to provide more accurate results.

[Emergency cesarean section--organization and decision-delivery time]. / Notsectio--Organisation und E-E-Zeit.

The German Society of Gynaecology and Obstetrics has published standards for obstetrical services concerning equipment, personnel and organisation. All obstetrical services must be able to perform an emergency Caesarean section with a 20 minutes interval from decision to delivery (D-D time). This study represents an analysis of the 75 emergency Caesarean sections performed at the University hospital Grosshadern of Munich during the interval from 1987 to 1994. This being a level III hospital, there is a 24 hour obstetrical, anaesthesia and neonatal service, and personnel is readily available. The operation can and has been done in each delivery room. 1. The incidence of emergency Caesarean sections was 0.6% compared to a total Caesarean rate of 21.5% in a high risk population having a preterm rate of 19% during the period of the study. 55% of the patients who had emergency Caesarean sections presented with a gestational age of less than 37 weeks and 35% of less than 32 weeks. 2. The mean time elapsed between decision and delivery (D-D time) was 12.8 minutes; however, the 90 percentile was 22 minutes and exceeded the recommended D-D time of 20 minutes. The mean decision to incision interval represented 9.1 minutes, and 3.6 minutes were needed between incision and delivery. 3. There was a significantly higher frequency of emergency Caesarean sections, performed during daytime and evening hours compared to early morning (0-8 a.m.). However, the D-D time intervals examined for these three time periods showed only minor, non-significant differences. In conclusion, an efficient emergency Caesarean delivery requires a coordinated team effort with excellent cooperation between obstetrics, anaesthesia and neonatology. Our study demonstrates that even in this optimal setting a decision to delivery time within the 20-minute interval can not always be achieved. Based upon our results and other studies, we recommend a D-D time of 30 minutes.

[Mortality, mode of delivery, pneumothorax and intracranial hemorrhage in 859 extremely premature newborn infants between 1984-1992]. / Mortalität, Geburtsmodus, Pneumothorax und intrakranielle Blutungen bei 859 extrem Frühgeborenen zwischen 1984-1992.

In a retrospective study we investigated the mortality and the most important complications of all very low birth-weight infants (VLBW; < or = 1500 g and/or < or = 32 weeks) born with vital signs between 1984 and 1992 at the Klinikum Grosshadern, Munich University Hospital. During this period 859 premature infants fulfilled the entrance criteria. The perinatal mortality rate was 174/859 infants (20%). During the study period the mortality rate dropped significantly from 25% (1984-1986) to 15% (1990-1992). Premature infants born after 26 gestational weeks showed the most significant decrease in mortality. Excluding non viable infants with extreme immaturity ( < 24 weeks of gestation) or lethal malformations; the mean corrected mortality rate was 11%, decreasing over the years from 16% (1984-1986) to 5% (1990-1992). Caesarean section was performed in 70% of all children (602/859), vaginal delivery in 28% (239/859), delivery by forceps in 1% (7/859), and the mode of delivery was not clearly registrated in 1% (11/859). The incidence of Caesarean section increased significantly from 55% (1984-86) to 79% (1990-92). Evaluating the mode of delivery in relation to mortality, a significant difference was found between the infants delivered vaginally (40%, 95/239) and those delivered by Caesarean section (11%, 67/602). This improved survival after Caesarean section was statistically significant for the group with a birth weight of less than 1500 g. The rate of pneumothorax also declined significantly from 19% to 9%. The rate of intracranial haemorrhage (ICH) remained almost constant during these years, but the incidence of ICH grade 3 and 4 decreased from 15% (1984-1986) to 6% (1990-1992). Probably because of improved antenatal care and the progress in neonatal intensive care, the chance of survival for VLBW infants has substantially improved over the last decade. Estimations of the prognosis of VLBW infants based on data from the 1980s are out of date.

Rupture of splenic artery aneurysm in a pregnant patient with portal hypertension.

The rupture of a splenic artery aneurysm in pregnancy is a rare emergency. As our case illustrates, immediate laparotomy often cannot prevent the fatal outcome. Pregnancies with portal hypertension are at increased risk, and therefore screening for splenic artery aneurysm is recommended, if possible, before conception.

Continuous fetal monitoring of HbO2 with pulse oximetry.

Pulse oximetry is well established in anesthesia and intensive care medicine. Application for fetal monitoring would be desirable, but significant modifications are necessary. We report our first promising clinical experience with a self-developed probe, hard- and software system. We hope by the positive results which we have observed that this new technology--oxicardiotocography (OCTG) will improve the safety of fetal monitoring.

[Monitoring fetal delivery by oxycardiotocography]. / Fetale Geburtsüberwachung durch Oxykardiotokographie (OCTG).

Oxycardiotocography is a combination of cardiotocography and continuous registration of the foetal arterial oxygen saturation (SaO2). In a few cases, the value of this additional information of foetal SaO2 is demonstrated. During uncomplicated deliveries with normal foetal heart rate patterns, the foetal SaO2 usually ranges between 50% and 70%. Uterine hyperactivity with impaired perfusion of the placenta shows besides a changed heart rate patterns, a significant decrease of the foetal oxygen saturation. Conversely, by supplying oxygen to the mother with a mask, the foetal oxygen saturation can be increased by approx. 10%. In case of a breech presentation and application of the sensor to the buttocks, the measured O2-saturation is approx. 10% to 15% below the values usually obtained from the scalp because the tissue there is supplied with mixed blood after the ductus.

Increasing DNase I activity after exposure of isolated DNA to halothane.

DNA was exposed to halothane (CAS 151-67-7) in a cell-free system. After exposure the DNA was used as substrate for DNase I from bovine pancreas. The DNase I activity increased after halothane exposure of the substrate depending on time and doses. Drugs are able to influence the DNA conformation. Conformational changes in the DNA can enhance the DNase I cleavage rate. Therefore, it is possible that halothane exposure induces changes in DNA conformation demonstrable by an increased DNase I activity. The results suggest a mechanism by which halothane may contribute to chromosomal defects and disturbances of DNA metabolism in cells.

Duration of the multifetal gestation, birth weight and infant prognosis.

For the higher numbered multifetal gestation, duration of gestational age decreases in spite of different medical activities. On the other hand increasing gestational age often strongly suggests the need for delivery by caesarean section for maternal indications. After the 32nd week of gestation in general no serious respiratory problems should be expected, and there may be no essential increase in fetal weight, but the risk of intrauterine death increases due to placental insufficiency. Therefore, for logistic reasons we propose liberal indications for caesarean section after the 32nd week of the multifetal gestation.

[A new procedure for continuous measurement of fetal oxygen saturation sub partu]. / Ein neues Verfahren zur kontinuierlichen Messung der fetalen Sauerstoffsättigung sub partu.

The principal aim of foetal monitoring during labor is early detection of hypoxia. Current methods are unable to accomplish this task. Pulse oximetry permits continuous measurement of oxygen saturation and is the best method to detect early hypoxia. In this report, an optical scalp electrode is presented, which permits continuous monitoring of foetal oxygen saturation during labor.