Assessment of Paracervical Nerve Block Anaesthesia during Labour

Murphy, Peter; Wright, J. D.; Fitzgerald, Tom

doi:10.1136/bmj.1.5695.526

Cited by 18 publications

(1 citation statement)

References 10 publications

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“…As with lidocaine and mepivacaine, paracervical nerve block anaesthe sia during labour resulted in significant rates of fetal bradycardia [Murphy et al, 1970] as well as increased maternal and fetal blood levels in some cases [Hollmén et al, 1969]. It has been concluded that, because of such adverse effects, the amide-type local anaesthetic drugs should not be used for single paracervical block (see Lidocaine and Mepivacaine).…”

Section: Transfer To the Fetus At Termmentioning

confidence: 99%

Clinical Pharmacokinetics in Pregnancy and Perinatology

Nau¹

1985

Dev Pharmacol Ther

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Local anaesthetic agents, both of the amide type (e.g., lidocaine, bupivacaine, etidocaine) and of the ester type (e.g., 2-chloroprocaine) are widely used to relieve pain in obstetric and gynaecological practice. The pharmacokinetics of these compounds are discussed in this review, with particular emphasis on the fetal exposure and its relationship to adverse effects on the fetus. 2-Chloroprocaine is rapidly hydrolyzed by esterases, and only traces of this compound reach the fetus, even following multiple injections, suggesting safety for the fetus. The main disadvantage of this compound is the short duration of action (0.5-1 h). The amide-type agents are active for longer time periods (up to several hours). The fetal/matemal total concentration ratios were approximately 0.3 for bupivacaine and etidocaine, 0.5 for lidocaine, 0.7 for mepivacaine, and 1 for prilocaine. The low ratios of bupivacaine and etidocaine result from extensive binding (90%) of these drugs to maternal a(1)-acid glycoprotein which exceeds corresponding fetal protein binding (50%). These low fetal/matemal total concentration ratios cannot be equated with fetal safety, because fetal side effects are better related to the free drug levels. Since the amide- type anaesthetics are weak bases, fetal acidosis will increase the matemal/fetal pH gradient and will result in accumulation of free drug in the fetus and possible fetal side effects. Addition of epinephrine to the injection solution reduces the maternal blood levels of the amide-type compounds, but apparently not the fetal levels to the same extent. Because of possible unwanted effects of epinephrine (decreased uterine blood flow), the addition of this compound is not generally accepted to be of advantage. Paracervical blockade may result in elevated fetal blood levels (possibly by transarterial diffusion into uterine arteries) and possibly fetal bradycardia.

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Section: Transfer To the Fetus At Termmentioning

confidence: 99%