Cahiers d'anesthésiologie
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Lumbar plexus block is indicated in anesthesia and analgesia of the proximal part of the lower limb. Several techniques, two via the anterior approach and at least three via a posterior paravertebral approach have been described. All these techniques are not equivalent in terms of technical facilities or difficulties, efficacy, success or failure rates and postoperative analgesia. The best choice must be done keeping in mind all advantages or disadvantages of each technic.
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The placental transfer of local anaesthetics (LA) depends on maternal factors (LA dosage, degree of protein binding, blood pH), placental factors (surface of placental exchange, placenta thickness) and fetal factors (maternal-fetal gradient of pH, fetal hepatic metabolism of the LA, redistribution of the cardiac output in case of fetal hypoxia). The assessment of effects of LA and epidural anaesthesia (EA) on the fetus is based on the monitoring of the fetal heart rate and the measurement of the fetal pH allowing to rapidly detect an acute fetal distress. Apgar score, analysis of blood gases in the umbilical artery and neurobehavioral tests (such as Brazelton test (NBAS). ⋯ Direct effects of LA: although a diminution of variability of the fetal heart rate has been reported little after the beginning of an EA using lidocaine, no significant modification of the fetal heart rate after EA using bupivacaine or lidocaine with epinephrine has been shown. Fetal neurological toxicity is rare and there are very little alterations of neurobehavioral scores after EA. Indirects effects on the uteroplacental blood flow (UBF): in high concentration, LA entail a vasoconstriction of uterine arteries but the main feared effect is maternal arterial hypotension that impedes directly the uteroplacental blood flow: fetal consequences depend on the importance and duration of the UBF decrease, the preliminary state of the utero-placental circulation and haemodynamic adaptative capacities of the fetus: when the former are exceeded, fetal hypoxia occurs and myocardial and brain oxygenation can be rapidly impaired if the haemodynamic state is not corrected.(ABSTRACT TRUNCATED AT 250 WORDS)
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Despite of a chronic volume overload the left ventricle function of pregnant women is preserved by both afterload reduction (arterial vasodilatation) and a facilitation of heart filling through an increase in peripheral venous tone. Fetal oxygenation results from an equilibrium between placental and umbilical blood flows. During regional anaesthesia the sympathetic blockade leads to a peripheral vasodilatation (mainly in the capacitive territories) which is the cause of arterial hypotension through a decrease in cardiac output. ⋯ Finally regional anaesthesia is beneficial for the mother and the fetus through a reduction in plasma catecholamines, provided that arterial pressure remains unchanged. Thus during pregnancy-induced hypertension (PIH) epidural analgesia leads to an improvement of the reduced placental blood flow. However PIH renders the women susceptible to sympathetic blockade and the fetus easily vulnerable to an additional stress factor like acute decrease in placental flow due to hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)
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Unlike epidural anaesthesia for general surgery or caesarean section, épidural analgesia for labour leads to maternal hyperthermia. Its recent demonstration is probably related to the multiple influencing factors: site of measurement, ambient temperature, previous labour duration and dilatation at the time of epidural puncture, and occurrence of shivering. During the first 2 to 5 hours of epidural analgesia, there is a weak--if any--thermic increase. ⋯ This hyperthermia has been correlated with foetal tachycardia but never with any infectious process. A potential deleterious effect is still debated and may lead to propose an active cooling for the mother. This hyperthermia must also be recognized to avoid an inadequate obstetrical attitude (antibiotics, extractions).
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Pain is a major factor of respiratory decompensation after chest trauma. General and/or regional analgesia improve alveolar ventilation, make physiotherapy easier and often avoid mechanical ventilation. Concerning regional techniques, epidural, intercostal and interpleural routes have their respective indications and contraindications, benefits and risks. When suitable, epidural analgesia appears to be the preferable technique.