Association of uterine activity and maternal volatile anesthetic exposure during open fetal surgery for spina bifida: a retrospective analysis.

BACKGROUND: Recent warnings postulate a possible damaging effect of volatile anesthetics on the fetus. In our archive of fetal surgeries, we found wide variation in dosing of volatile anesthetics during spina bifida surgeries. We hypothesized that there was an association between volatile anesthetic exposure and uterine activity. METHODS: Sixty anesthesia records from spina bifida operations were assessed. We analyzed the course of the administered volatile anesthetic during surgery and calculated from each patient's anesthesia record the volatile anesthetic exposure expressed in vol%h. We divided the records into two post hoc groups of the 20 lowest exposure (Group L) versus the 20 highest exposure (Group H), and compared them for uterine activity and fetal heart rate. RESULTS: The number of contractions per hour was significantly greater in Group H (mean 1.3, SD ±â€¯1.2) compared with Group L (mean 0.5, SD ±â€¯0.6, P=0.049). There was no difference between the groups for the administration of the tocolytic drug atosiban (P=0.29). The course of the mean arterial pressure did not significantly differ but group H needed significantly more vasoactive medication (P <0.05). CONCLUSIONS: We found that a lower intra-operative volatile anesthetic exposure than recommended in the MOMS-trial (i.e. <2.0 minimum alveolar concentration [MAC]) was not associated with an increase in intra-operative uterine activity. This is an indication that during spina bifida surgery, 2.0 MAC may not be necessary to avoid potentially harmful uterine activity.

Area-pressure relationship of lower limb main veins in man.

BACKGROUND: The mechanical properties of human veins remain incompletely known. However they play an important part in number of physiological and pathological situations, as hemodynamic adjustment to orthostasis, deep venous thrombosis (DVP) and chronic venous insufficiency (CVI). The aim of the study was to describe the pressure/volume (area) relationship of some important conduit veins of the human's lower limb. PROBANDS AND METHODS: We investigated the area/pressure relationship of thefemoral vein (FV) at mid thigh, the great saphenous vein (GSV) at lower third of the leg, and a deep leg vein (DLV), either the peroneal or posterior tibial vein, in fifteen healthy young men. The cross section areas were measured with B-mode ultrasound while various positive and negative venous pressures were generated by body's tilting. RESULTS: Over the range of pressures investigated, the area/pressure relationship was roughly linear, the classical sigmoid relation did not emerge from our data. The relative compliance of FV, GSV and DLV was 0.0312, 0.0118, and 0.0147 mmHg(-1), respectively. CONCLUSIONS: The relative compliance of FV is more than two times higher than the relative compliance of both the DLV and the GSV.

Human muscle fatigue and elastic compressive stockings.

The present study was performed to test if elastic compressive stockings (ECSs) increase muscle fatigability during sustained muscle contraction or if it improves the recovery after fatigue. Surface electromyograms (EMGs) were recorded on 4 leg and thigh muscles, and static ankle dorsal flexion force levels were measured in the right limb of 15 healthy subjects. The subjects maintained a 50% maximum ankle dorsal flexion force (MVF) for as long as possible without and, after a 30 min rest, with a European class I ECS. Finally, after another 30 mn rest, the pressure exerted by the ECS on the skin was measured at standard points on the limb, using a Salzmann apparatus. During the first 10 min of both rest periods, the subjects performed brief static maximum ankle dorsal flexions every 30 s. ECS exerted a 14.3 mm Hg mean pressure at tibial level C. Linear relationships, whose slopes were not influenced by ECS, existed between the maintenance time and both the mean power frequency and the logarithm of the total power of the tibialis anterior and gastrocnemius lateralis EMGs. The endurance times, the force recovery times after fatigue and the linear relationships between the logarithm of the time elapsing after exhaustion and the MVF reached during the recovery period were also independent of ECS. The results show that class I ECSs are not responsible for greater muscle fatigability; but they do not improve force recovery during rest following static fatiguing voluntary contractions.