International journal of obstetric anesthesia
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Int J Obstet Anesth · Jan 1999
The occupational exposure of midwives to nitrous oxide - a comparison between two labour suites.
The study of midwives' occupational exposure to nitrous oxide in a poorly ventilated maternity unit in 1992 was instrumental in ensuring that the replacement building had Department of Health approved ventilation. We have repeated the study in the new unit. ⋯ This difference was significant amongst those midwives who spent a greater time looking after women using Entonox and thus were more at risk from its detrimental effects. We discuss these findings and the ramifications for other maternity units under the new COSHH regulations.
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Int J Obstet Anesth · Jan 1999
Transfer of lidocaine across the dual perfused human placental cotyledon.
Factors affecting lidocaine transfer across the normal term human placenta were studied using the dual perfused isolated single cotyledon. Experiments were performed using perfusates which provided equal protein binding in both the maternal and fetal circuits as well as perfusates that approached the actual in vivo maternal/fetal protein binding gradient. Additional experiments were performed to investigate the effects of increasing maternal lidocaine concentration (5, 10, 40, 80 microg/mL) on maternal to fetal (M-->F) lidocaine transfer across the human placenta. ⋯ When protein binding was similar in the two circuits, M-->F transfer ratios (lidocaine transfer/antipyrine transfer) were significantly lower than the transfer ratios seen in the F-->M direction (0.59+/-0.04 versus 0.84+/-0.06, P<0.05). Transfer ratios (M-->F: 0.83+/-0.06, F-->M: 0.96+/-0.06) were not reduced when the physiological maternal/fetal protein binding gradient was present. Lidocaine transfer was not diminished by increasing maternal concentrations and, in contrast to bupivacaine, was not significantly affected by its binding.
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Int J Obstet Anesth · Jan 1999
An audit of single dose epidural diamorphine during elective caesarean section at a district general hospital.
Mothers receiving combined spinal-epidural (CSE) anaesthesia for elective caesarean section (n = 188) were audited. A single dose of epidural diamorphine (2-3 mg) was given during surgery. Unless contraindicated, diclofenac 100 mg was given per rectum at the end of surgery. ⋯ Nausea was uncommon: mild (19%), moderate (10%), severe (2%); 16% of mothers received anti-emetics. Itching was less than previous reports with subarachnoid diamorphine. Single dose epidural diamorphine can be used during elective caesarean section rendering systemic opiates unnecessary.
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Int J Obstet Anesth · Jan 1999
A proposed mechanism of bupivacaine-induced contraction of human umbilical artery smooth muscle cells.
This in vitro study using ring preparations of human umbilical vessels and cultured human umbilical artery smooth muscle cells was designed to determine: (a) the mechanism of bupivacaine-induced contraction of ring preparations, and (b) whether similar concentrations of bupivacaine release Cal(2+) in cultured smooth muscle cells. Isometric tension was recorded from ring preparations of human umbilical veins and arteries in an isolated tissue chamber. Separate fluorescence and electrophysiology studies were done with cultured human umbilical artery smooth muscle cells. ⋯ Bupivacaine also increased intracellular Cal(2+) in patterns consistent with tonic or phasic tension responses seen in isometric recordings. In addition, the membrane-resting potential was depolarized by bupivacaine. Since similar concentrations of bupivacaine caused both contraction and a rise in intracellular Ca(2+), the bupivacaine-evoked contraction was the result of increased cell Cal(2+) and the source of this Ca(2+) was the extracellular space.