ACE Sample Question
Which of the following is the MOST common complication of paracervical block when performed for labor analgesia? Read the discussion.
(A) Fetal scalp injury
(B) Fetal bradycardia
(C) Postpartum neuropathy
(D) Local anesthetic systemic toxicity
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Paracervical block is a relatively simple procedure for labor analgesia that is performed by obstetricians, albeit rarely. The technique blocks neurotransmission via the paracervical ganglion, which contains the visceral sensory fibers from the cervix, uterus, and upper vagina. Local anesthetic solutions are injected into the submucosa of the cervicovaginal junction (fornix of the vagina) to achieve analgesia during the first stage of labor (Figure 1).
Figure 1. Representation of the segments affected by regional blocks used for obstetric analgesia and anesthesia. © 2020 American Society of Anesthesiologists.
Fetal bradycardia is the most common complication of paracervical block, with an occurrence of about 10% to 20%, but occurrence has been reported to be as high as 70%. Fetal bradycardia typically occurs within 10 minutes after injection of local anesthetic and may persist for as long as 30 minutes. In most cases, it is a transient phenomenon, resolving within 5 to 10 minutes. Fetal acidosis may develop if bradycardia persists for a prolonged period. The exact mechanism for bradycardia is not known, but several possibilities have been reported:
- Deposition of local anesthetic near the uterine arteries, which may induce vasoconstriction and decrease uterine blood flow
- Increased uterine contractions by deposition of local anesthetic, which may cause reduction of uteroplacental perfusion
- Reflex bradycardia from manipulation of the uterus and fetal head
- Passage of local anesthetic via the placenta and depression of the fetal central nervous system and myocardium, producing fetal bradycardia
- Direct depressant effect of local anesthetic on the fetal heart
Current evidence suggests that the most likely reason for bradycardia is reduction of uteroplacental perfusion due to uterine artery vasoconstriction or increased uterine contraction.
Other less common complications of paracervical block include fetal scalp injury and intrafetal injection of local anesthetic. Less common maternal complications include laceration of the vaginal mucosa, local anesthetic systemic toxicity, parametrial hematoma, postpartum neuropathy, vasovagal syncope, and paracervical or subgluteal abscess.
- Chestnut DH, Wong CA, Tsen LC, Ngan Kee WD, Beilin Y, Mhyre JM, eds. Chestnut’s Obstetric Anesthesia: Principles and Practice. 5th ed. Philadelphia, PA: Elsevier Saunders; 2014:518-529.
- Suresh MS, Segal BS, Preston R, Fernando R, Mason CL, eds. Shnider and Levinson’s Anesthesia for Obstetrics. 5th ed. Baltimore, MD: Wolters Kluwer/Lippincott Williams & Wilkins; 2013:131-132.