An evaluation of the Hellige Transoxode (Servomed Oxymonitor SM 361 System): response to halothane and enflurane in vitro.

The effects of halothane (0.5-2%) and enflurane (1-4%) on two Transoxode transcutaneous oxygen (TcPO2) electrodes (Hellige Servomed Oxymonitor SM.361 system) were serially tested in atmospheres of nitrogen, air and 50% nitrous oxide in oxygen. Both TcPO2 electrodes reduced and "read" halothane but no enflurane. Calibration drift was significantly greater (p less than 0.05) after electrode exposure to halothane; 5.40 s.e.m. 1.37 kPa vs enflurane; -0.60 s.e.m. 0.93 kPa. Halothane has a direct effect in rendering the Transoxode inaccurate, which is probably clinically less important than the indirect cardiovascularly medicated influence of both halothane and enflurane on TcPO2 levels. A reduction in the electrode polarisation voltage is recommended to obviate the direct effect of halothane on Transoxode performance.

Aspects of intra-uterine fetal resuscitation.

An analogy may be drawn between the lungs and placenta regarding distribution and matching of their exchanging flows. Furthermore, prostaglandins probably play a role in restoring the normal pulmonary ventilation-to-perfusion ratio (V/Q) and the uterine (maternal)-to-umbilical (fetal) placental perfusion ratio (Q-q). Availability of oxygen to the fetal brain is probably independent of PaO2, provided cerebral tissue PO2 is above a certain critical level. Oxygen content rather than PO2 of the blood perfusing the fetal brain is the prime factor in maintaining adequate cerebral oxygenation. With the above physiological consideration in mind, the concept of intra-uterine fetal resuscitation is presented. The hypothesis that low concentrations of aneasthetic vapours and 60% oxygen inhaled by the mother in the presence of fetal distress improve placental blood flow matching, and hence fetal cerebral oxygenation, is discussed.