Volker König

LONG-TERM FOLLOW-UP OF HEPATITIS B VIRUS-INFECTED RECIPIENTS AFTER ORTHOTOPIC LIVER TRANSPLANTATION

The outcome after OLT was studied in 53 patients with chronic hepatitis B virus (HBV)* infection, 15 of whom had, in addition, evidence of hepatitis delta virus (HDV) superinfection. Nine of 53 patients received short-term immunoprophylaxis with anti-hepatitis B surface (HBs) hyperimmunoglobulin up to 1 week after OLT and 44 of 53 patients received long-term unlimited immunoprophylaxis. Eight of 9 (89%) patients with short-term immunoprophylaxis showed reactivation of replication with HBV DNA in serum > 10 pg/ml independently of the preoperative HBV DNA level and HBsAg reappeared in all cases. Four (44%) patients in this group lost their graft because of fulminant hepatitis or cirrhosis and required retransplantation, and 2 patients (22%) died after reinfection in the second graft. Nineteen of 44 (43%) patients with long-term immunoprophylaxis developed HBV values > 10 pg/ml after transplant and 12 of 44 (27%) became HBsAg+ again. Most of them had quantifiable HBV DNA levels before OLT. Retransplantation was required in 5 of 44 (11%) patients and 4 of them died after HBV recurrence. The frequency of HBV reactivation and the development of viral hepatitis after OLT were associated with the preoperative presence of HBV, as determined by the molecular hybridization assay. With nested polymerase chain reaction, all 53 patients were HBV-DNA+ in the serum before and after OLT. with just one exception, none of the patients with HDV superinfection died, in spite of increased HDV replication after OLT. The data indicate that long-term immunoprophylaxis with anti-HBs hyperimmunoglobulin after OLT improves the prognosis in HBV-infected patients. The preoperative detection of HBV DNA in serum by molecular hybridization assay is correlated with graft infection and represents a prognostic parameter. The presence of HDV may have a protective effect after OLT.

Pulse oximetry used for documenting oxygen saturation and right-to-left shunting immediately after birth

The objective of this study was to investigate the clinical applicability of pulse oximetry to measure haemoglobin oxygen saturation and heart rate in the first 20 min of life and to analyse the effect of pre- or postductal (hand, respectively, foot) fixation of sensors on oxygen saturation. Measurements were carried out on 53 newborn infants selected at random after delivery by caesarean section. Signal detection occurred significantly faster from the hand (50% after 1.3 min, 90% after 4 min) than from the foot (50% after 3.1 min, 90% after 9 min). Both fixation sites showed equally great sensitivity to motion. The heart rates from pulse oximetry recordings were up to 30% lower than those from ECG recordings. Saturation values from the hand were nearly always higher than those from the foot (median difference in the 5th min was 10%; between the 5th and 10th min it was 7%; no significant difference occurred after the 17th min). We conclude that pulse oximetry can be used for documenting oxygenation and right-to-left shunting in newborn infants during the first minutes of life in spite of limitations due to incomplete pulse wave detection and artifacts.

Intrapartum reflectance pulse oximetry: effects of sensor location and fixation duration on oxygen saturation readings

Objective. To determine the effects of sensor location and suction fixation duration on measurements of intrapartum fetal oxygen saturation (SpO2) with a new reflectance pulse oximetry system. Design. Fetal SpO2 values (n = 18) were determined in the first stage of labor before and after moving the sensor to another part of the fetal head. Results. Mean fetal SpO2 values did not differ with sensor location (95% CI: −3.59 to 1.48). The duration of measurement period 1, before moving the sensor, was 104 ± 44 (range 30–240) min. No time-dependent changes in SpO2 values were seen (r = 0.17). Conclusion. Suction is an effective and noninvasive method of securing the reflectance pulse oximetry sensor to the fetal head in the first stage of labor and does not interfere with reproducible SpO2 values over several hours.

Reflectance pulse oximetry--principles and obstetric application in the Zurich system.

Transmission and reflectance are the two main modes of pulse oximetry. In obstetrics, due to the absence of a transilluminable fetal part for transmission oximetry, the only feasible option is the reflectance mode, in which sensor and detector are located on the same surface of the body part. However, none of the reflectance pulse oximeters developed for intrapartum use are fully satisfactory, as indicated by the fact that none have entered routine use. We have designed, developed, constructed and tested a reflectance pulse oximeter with the possibility to adjust the electronic circuits and signal processing in order to determine the effects of various parameters on signal amplitude and wave-form and to optimize the sensitivity and spatial arrangement of the optical elements.Following an explanation of the principles of reflectance pulse oximetry, we report our experience with the design, development, construction and field-testing of an in-house reflectance pulse oximetry system for obstetric application.

Changes in bone density and metabolism in pregnancy

Objective.  The impact of pregnancy on maternal bone density remains unclear. As a prerequisite to investigate the pathophysiology of gestational bone metabolism, we sought to document the changes in bone metabolism biochemistry in conjunction with those in selective trabecular/cortical osteodensitometry between early and late pregnancy.

Limitations of forehead pulse oximetry

During initial clinical tests to calibrate our reflectance pulse oximetry system, we observed serious physiologic limitations to the use of pulse oximetry in the forehead region. We present a case of simultaneous reflectance and transmission mode pulse oximetry monitoring in a child undergoing cardiac surgery for congenital cyanotic heart disease with a large intracardiac shunt. During general anesthesia, when the patient was endotracheally intubated and mechanically ventilated, the transmission mode saturation agreed well with arterial oxygen saturation measurements; but, our reflectance pulse oximeter, with the sensor applied to the forehead, displayed spuriously lower (−18%) oxygen saturations. Before and after anesthesia and surgery, there was fine agreement between reflectance and transmission mode saturation values. We suggest that the difference was caused by vasodilatation and pooling of venous blood due to compromised venous return to the heart, and a combination of arterial and venous pulsations in the forehead region. This means that the reflectance pulse oximeter measured a mixed arterial-venous oxygen saturation.

Reflectance pulse oximetry in neonates

OBJECTIVE To test the feasibility and reliability in neonates of an in-house reflectance pulse oximetry (RPOX) system as an alternative method of non-invasive oxygen saturation monitoring when transmission pulse oximetry (TPOX) cannot be used, as in fetal scalp oxygen saturation monitoring during delivery. STUDY DESIGN The study population consisted of 31 intensive care neonates. The RPOX sensor was attached by suction to the forehead, cheek, occiput and back; recordings were under simultaneous TPOX control. RESULTS There was close agreement between RPOX and TPOX oxygen saturation and heart rate values, even in periodic breathing. RPOX signals from the back were unreliable because of breathing artifacts. Differences in mean absolute RPOX and TPOX oxygen saturation values were due to different calibrations. Both systems were equally sensitive to motion artifacts. CONCLUSION As a feasible and reliable method of non-invasive oxygen saturation monitoring in neonates, RPOX has potential applications in fetal scalp monitoring.

Pre‐core mutants of hepatitis B virus in patients receiving immunosuppressive treatment after orthotopic liver transplantation

Orthotopic liver transplantation (OLT) is a possible treatment for acute or chronic liver failure due to hepatitis B virus (HBV) infection, but reinfection of the graft can be a serious complication. The aim of this study was to monitor HBV markers, to analyse pre‐core‐/core‐mutations as well as to identify the viral population causing reinfection after OLT, and to investigate the emergence or disappearance of these mutants in patients receiving immunosuppressive treatment.

Calibration of a reflectance pulse oximeter in fetal lambs for arterial oxygen saturations below 70

Objective: To calibrate a reflectance pulse oximeter developed at the Division of Perinatal Physiology, University Hospital of Zurich, for monitoring of oxygen saturations below 70%. Methods: Oxygen saturation measured monivasively with the reflectance pulse oximeter in fetal sheep was compared with oxygen saturation of arterial blood samples measured by a conventional two-wavelength oximeter. Oxygen saturation was varied by stepwise reduction of the inspired oxygen concentration of the ewe. Results: A total of 58 data pairs was obtained from five fetuses, with a range of 10.9-73.5% for the reference method and 6.8-69.2% for the pulse oximetry oxygen saturation values. There was good correlation between the results obtained by the two methods (r2 = .89, P < .0001), with a 95% confidence interval of ± 12.5%. The pulse oximeter showed a precision of 6.2% oxygen saturation. Conclusion: The Zurich reflectance pulse oximeter offers valid measurements of oxygen saturation levels down to 10% oxygen saturation, and is therefore suitable for monitoring the fetus during delivery.

Erfahrungen bei der Messung der Sauerstoffsättigung mittels eines eigenen Reflexions-Pulsoximetrie-Systems bei Erwachsenen und Neugeborenen sowie bei ersten Messungen während der Geburt

Die Transmissions-Pulsoximetrie (TOPX) hat sich in der klinischen Routine zur Uberwachung der arteriellen Sauerstoffsattigung (SO2) durchgesetzt, da es sich um ein einfach anzuwendendes, nichtinvasives Verfahren handelt. Um fetale Risikozustande sub partu fruhzeitig zu erkennen, hegt daher der Wunsch nahe, die Pulsoximetrie auch als intrapartale Uberwachungsmethode einsetzen zu konnen. Die klinische Anwendbarkeit der Reflexions-Pulsoximetrie (RPOX), die diese Moglichkeit in Aussicht stellt, wird derzeit in Studien evaluiert.