Lidocaine hydrocarbonate and lidocaine hydrochloride for cesarean section: transplacental passage and neonatal effects

Treatment of cluster headache in pregnancy and lactation

Cluster headache is a rare disorder in women, but has a serious impact on the affected woman's life, especially on family planning. Women with cluster headache who are pregnant need special support, including the expertise of an experienced headache centre, an experienced gynaecologist and possibly a teratology information centre. The patient should be seen through all stages of the pregnancy. A detailed briefing about the risks and safety of various treatment options is mandatory. In general, both the number of medications and the dosage should be kept as low as possible. Preferred treatments include oxygen, subcutaneous or intranasal sumatriptan for acute pain and verapamil and prednisone/prednisolone as preventatives. If there is a compelling reason to treat the patient with another preventative, gabapentin is the drug of choice. While breastfeeding, oxygen, sumatriptan and lidocaine for acute pain and prednisone/prednisolone, verapamil, and lithium as preventatives are the drugs of choice. As the individual pharmacokinetics differ substantially, adverse drug effects should be considered if unexplained symptoms occur in the newborn.

Maternal and fetal effects of propofol anaesthesia in the pregnant ewe

The objective of this study was to determine the effects of propofol (PRF) on maternal and fetal cardiopulmonary function during the last trimester of pregnancy. Six pregnant 2-3 year-old Ripollesa sheep, each weighing 78+/-8 kg were used in the study and prepared by placing catheters in the maternal jugular vein and carotid artery. A catheter was also placed in the fetal femoral artery. Twenty-four hours later the sheep were anaesthetized with PRF (6 mg/kg intravenous (IV) followed by a continuous infusion at a rate of 0.4 mg/kg/min for 60 min) and cardiopulmonary data collected. Further data were collected for 105 min following termination of the infusion. The maternal mean arterial pressure (MAP) and diastolic arterial pressure (DAP) were significantly decreased (P<0.05) during the first 15 min of the infusion period, while the maternal pH was also significantly decreased. Maternal PaCO(2) and PaO(2) were significantly increased throughout the total infusion period. It was further observed that the fetal pH decreased significantly, throughout the infusion period, whereas the fetal MAP, DAP and PaCO(2) were significantly increased during the first 15 min of the infusion, after which time all parameters returned to control values. No differences in either maternal or fetal parameters were observed between control and recovery times.

Pharmacological considerations during pregnancy

We present a brief overview of recent literature concerning some of the drugs used in pregnancy, labour and delivery. Obstetric anaesthesia continues to evolve through the reuse of old drugs such as magnesium sulphate or the manipulation of current drugs (e.g. propofol for emesis) in order to improve patient outcome. Pregnant women have traditionally been therapeutic orphans. The use of new agents such as levobupivacaine and ropivacaine in obstetric patients lags behind that of their non-pregnant counterparts. However, this gap is decreasing and these new drugs offer benefits to the parturient woman.

Techniques to study human placental transport

Pregnancy in the 20th century involves women of many age groups from early teens to the fourth or fifth decade. Modern medicine and in vitro fertilization techniques have increased options for pregnancy and childbirth. Pregnancy is a dynamic state, and medical concerns may involve disorders of the fetus and mother requiring medications and special nutrients. Therefore, different techniques have been developed to evaluate the placental transfer of drugs and nutrients using tissues and cells derived from human placenta. These include (a) isolated tissues and cells to study placental transport, (b) primary and malignant trophoblast cell cultures and (c) biophysical methods for studying placental transport. Also, convenient study models have been developed to evaluate placental transfer of safe drugs in pregnant women. Some of the drugs studied by these techniques and models include (a) anesthetics and pain medications used during delivery, (b) antibiotics and anti-bacterials used to cure infections, (c) drugs abused by pregnant women and (d) nutrients required for proper fetal growth. Placental transfer and exchange mechanisms are complicated processes, and in vitro models reflect only partially the equilibria that exist among mother, placenta and fetus. The perfused cotyledon model is elegant and simple but gives only restricted information. Isolated placental tissues give useful information about the pharmacological effects of drugs. Metabolic studies using human placental models provide information on the metabolism of a drug during placental transfer and accumulation of the drug or its metabolite in the placenta or fetal circulation. Several studies on the transplacental passage of drugs exist but many questions regarding the transfer of drugs between the maternal and fetal circulations and clearance of drugs from fetal circulation have yet to be answered. This article reviews in vitro and in vivo methods for evaluation of transplacental transport of drugs and their current effectiveness to obtain clinically useful data.

Clinical pharmacokinetics of neuromuscular relaxants in pregnancy

Despite an increased in bodyweight, plasma volume by 45% and blood volume by 35% that might influence the volume of distribution of polar drugs, the apparent volume of distribution at steady state (Vss), volume of distribution (Vd) and the apparent volume of the central compartment (Vc) of atracurium, vecuronium and pancuronium are unchanged during pregnancy. With an elimination that is independent of renal, hepatic and enzymatic functions, the clearance of atracurium is also unchanged. This is corroborated by an unchanged clinical duration of atracurium during pregnancy. The clearance of pancuronium is increased by 27% during caesarean section. This may be explained by the increased glomerular filtration rate reported in pregnant women. The clinical duration of vecuronium in term and postpartum women is twice that reported in nonpregnant women. On the other hand, an increase in the clearance clearance of vecuronium during cesarean sections has been reported. The umbilical/maternal vein concentration ratio (UV/MV) of nondepolarising neuromuscular relaxants varies from 7 to 26% and clinical doses of these drugs may induce partial residual curarisation in neonates. Fetal concentrations of non-depolarising neuromuscular relaxants are proportional to the maternal dose injected as demonstrated for pancuronium and vecuronium. Increasing UV/MV with longer drug injection to delivery intervals have been demonstrated for drugs with a high molecular weight, such as atracurium, but not for those with a low molecular weight, such as vecuronium, while conflicting results have been reported for pancuronium. Despite decreased plasma pseudocholinesterases, the clinical duration of succinylcholine 1 mg/kg is unchanged in pregnant women, and only is slightly increased in postpartum women. On the other hand, larger doses of succinylcholine have induced prolonged apnoea and phase II block. The use of a pretreatment dose of a nondepolarising neuromuscular relaxant to decrease fasciculations and subsequent postoperative muscle pain is not only unnecessary in pregnant women but may be hazardous, since it may produce unexpected significant curarisation with respiratory distress. At clinical doses, transplacental passage of succinylcholine is insufficient to produce curarisation of neonates except in those born to mothers with abnormal plasma pseudocholinesterases. Magnesium sulfate, used in the treatment of pre-eclampsia, will enhance the blocking effects of nondepolarising neuromuscular relaxants but will have no effects on the characteristics of paralysis of succinylcholine. Histamine type 2 antagonists used to decrease the risk of aspiration during induction of anaesthesia do not influence the blocking properties of neuromuscular relaxants, while metoclopramide prolongs the block of succinylcholine.

Placental transfer of lidocaine hydrochloride after prolonged continuous maternal intravenous administration

We treated a patient with arrhythmia during pregnancy with prolonged intravenous administration of lidocaine hydrochloride. This was a case of twin-to-twin transfusion syndrome and the arrhythmia was caused by ritodrine therapy. In total, 14.1 g lidocaine (50 mg.hr-1 for 282 hr) were used. Since there are no descriptions of human placental transfer of lidocaine after such a prolonged continuous intravenous administration, we measured lidocaine concentrations in maternal and fetal serum, and in the amniotic fluid (AF) at delivery. Fetal serum lidocaine concentrations (donor: 0.83 microgram.ml-1; recipient: 0.82 microgram.ml-1) were lower than in the maternal serum (1.6 micrograms.ml-1), while the AF lidocaine concentrations (donor: 1.05 micrograms.ml-1; recipient: 1.04 micrograms.ml-1) were higher than those of the fetal sera. The fetal/maternal concentration ratios of lidocaine were 0.52 for the donor and 0.51 for the recipient, which were similar to those described previously after administration of lidocaine in labour.