Paracervical Block Anesthesia

Jay M. Berman, MD, FACOG and Samantha E. Montgomery, MD
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Subject: Paracervical Block Anesthesia

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Introduction

Paracervical block anesthesia has been used since 1925 and was originally refined for pain management during cervical dilation for voluntary termination of pregnancy. It was a popular method of analgesia for the first stage of labor, but has since fallen out of favor in North America due to the risk of fetal bradycardia and rare reports of fetal or neonatal death related to its use. Although paracervical blocks for labor remain popular throughout the rest of the world and the incidence of fetal bradycardia has greatly declined due to the standardization of injection methods, use in North America is now repopularized for ambulatory gynecologic procedures including office hysteroscopy, manual vacuum aspiration, treatment for incomplete abortion, and loop electrosurgical excision procedure (LEEP) and laser ablation procedures. 
Because of the relative ease of administration, lack of special equipment and independence from the anesthesiologist, the paracervical block lends itself well to outpatient gynecologic surgery. 
Innervation of the uterine cervix arises from the Lee-Frankenhäuser plexus, which is located lateral to the junction of the cervix and uterus at the base of the broad ligament. The Frankenhäuser ganglion houses the visceral afferent nerve fibers from the upper vagina, cervix and uterus. Sensory information is then carried to the spinal cord in T10–T12 and the L1 segmental nerves. Pain signals from cervical dilatation are transmitted primarily via this plexus and may be targeted for anesthesia by paracervical block. 
Local anesthetics used for paracervical block are derived from the amide class of anesthetics. These agents are metabolized by N-dealkylation and hydroxylation by microsomal P-450 enzymes in the liver and are metabolized much more slowly than agents from the ester class. Possible anesthetic choices, their strength, onset of action, duration of action and maximal dosages are outlined in Table 82-1. Ten milliliters of 1% lidocaine or 2% chloroprocaine without epinephrine may be used for paracervical block. Bupivacaine should be used in a 0.125% dilution by mixing 50/50 with normal saline. 
 
TABLE 82-1.
Anesthetic Choices for Cervical Blocks
The toxic effects of local anesthetics are generally manifested in the central nervous system (CNS) and the cardiovascular system. Early symptoms of CNS toxicity include circumoral numbness, tongue paresthesia, and dizziness at a plasma concentration of 4 mg/mL. Blurry vision results at a plasma concentration of 6 mg/mL. With exposure to increasingly toxic doses, excitatory symptoms develop, including restlessness, agitation, nervousness, and paranoia at 8 mg/mL. This period of excitation precedes CNS depression characterized by slurred speech, drowsiness, and unconsciousness. Muscle twitching precedes the onset of tonic–clonic seizures at 10 mg/mL, and finally, respiratory arrest occurs at 20 mg/mL. Cardiovascular toxicity develops at blood levels of local anesthetic that are almost three times that required to produce seizures—approximately 26 mg/mL. For this reason, cardiovascular toxicity is generally seen only in the setting of local blocks administered to patients under general anesthesia. Intravascular administration may produce hypotension, atrioventricular heart block, idioventricular rhythms, and life-threatening arrhythmias such as ventricular tachycardia and fibrillation. In general, amide anesthetics are used for paracervical blocks. Because these agents are metabolized in the liver, any condition which decreases hepatic blood flow (congestive heart failure, vasopressors) or function (cirrhosis) increases the risk of anesthetic toxicity. Many providers use lidocaine as 1% or 2% with 1:200,000 epinephrine, which prolongs the duration of action from ≤1 hour to 2 to 6 hours. This compares to the duration of action of bupivacaine 0.25% without epinephrine and maintains lidocaine’s rapid onset of action. 

Equipment

  • Gynecologic speculum of appropriate size

  • Single tooth tenaculum

  • Povidine-iodine solution

  • Sterile cotton balls or gauze

  • 10-cc syringe, control top preferred but not necessary

  • 22-gauge spinal needle or needle and needle extender

  • Local anesthetic of choice (see Table).

  • Crash cart with appropriate medications.

  • Intravenous supplies

  • Automatic external defibrillator

  • Pulse oximeter

  • Portable or wall oxygen with mask and nasal prongs

Indications

  • Diagnostic hysteroscopy

  • Endometrial ablation

  • Hysteroscopic female sterilization

  • Cervical biopsy

  • LEEP. This procedure is most commonly done with intracervical block.

Contraindications

  • Known hypersensitivity to any of the components of the anesthetic

  • Hypersensitivity to the antiseptic agent

  • Cardiac disease and hypertension are relative contraindications to anesthetic agents containing epinephrine.

The Procedure

Step 1

Prepare the tray of instruments including speculums, tenaculum, antiseptic, gauze. 

Step 2

Fill the syringe with 10 mL of the appropriate local anesthetic (see Table 1). 

Step 3

Attach the 22-gauge spinal needle or the 22-gauge needle with needle extender to the syringe. 

Step 4

With the patient in the lithotomy position, the vagina and cervix are cleansed with Betadine. Exposure of the uterine cervix may then be achieved with a sterile speculum or with a weighted speculum and vaginal retractor. The sites for local anesthetic infiltration are selected. The aim is to avoid the uterine vessels and ureters that are located bilaterally at the 3- and 9-o’clock positions. Generally, injections of anesthetic at the 4- or 5- and 7- or 8-o’clock positions are sufficient. 
  • PEARL: Multiple injections at 4, 5, 7, and 8 o’clock have been shown to be no more efficacious than two injections in a randomized-controlled trial involving 82 women.

Step 5

A 22-gauge spinal needle or 23-gauge needle with a needle extender is applied to the lateral edge of the cervix, taking care not to apply traction to the vaginal fornix as this may result in the uterine vessels being brought to a more superficial position. The needle is then advanced up to a depth of 0.5 cm, which allows infiltration of the uterosacral ligaments that carry the nerve bundles from the uterine corpus. One study found that less pain was experienced when local anesthetic was injected to a depth of 1.5 inches (3.81 cm); however, deeper injections carry the risk of intravascular injection. Most practitioners use a depth of 2 to 4 mm. This allows for palpable or visible mucosal swelling and slow intravascular absorption maximizing exposure of Frankenhäuser’s plexus to the anesthetic agent. 
 

Step 6

Aspirate prior to injection so as to avoid intravascular injection. Inject 3 to 5 mL of local anesthetic bilaterally. No more than 12 to 20 mL total should be used. Some authors support the theory that analgesia comes not from the anesthetic per se but from the volume-mediated distention of the tissues, which may exert enough pressure of the autonomic nerves to attenuate the conduction of pain fibers. 
  • PITFALL: Many failed anesthetics are due to impatience on the part of the provider. Think of your dentist giving local and then walking out of the room for 5 to 10 minutes. It is convenient to assemble all of the other procedural instruments (i.e., LEEP or Essure) only after the block is in place. This avoids provider impatience and starting too soon. Wait for the anesthetic to take effect before beginning the procedure.

  • PITFALL: Inadvertent intravascular injection is the leading cause of adverse events. In paracervical block, the location of the needle is close to the uterine arteries. Inadvertent vascular injections can cause CNS stimulation with seizures followed by CNS depression and possible respiratory arrest.

Complications

  • Hypersensitivity: esters more likely than amides to elicit an allergic reaction as they are metabolized to p-aminobenzoic acid, which is a known allergen.

  • If used in labor:

    • Bleeding from the vaginal fornices

    • Fetal scalp injection

    • Parametrial hematoma

    • Fetal bradycardia

    • Sacral plexus trauma

    • Fetal death

    • Infection and deep abscess formation

  • CNS toxicity

  • Respiratory arrest at doses of 20 mg/mL

  • Cardiovascular toxicity

  • Intravascular administration may produce hypotension, atrioventricular heart block, idioventricular rhythms, and life-threatening arrhythmias such as ventricular tachycardia and fibrillation

Pediatric Considerations

Paracervical block is not a useful technique in the pediatric population. Any extensive vaginal or cervical procedure in this population would require a general anesthetic. 

Postprocedure Instructions

Postprocedure counseling is generally not required except to state that the anesthetic effect may last for several hours after the procedure. Patients should be encouraged to start oral pain medication before the anesthetic wears off. 

Coding Information and Supply Sources

The higher fee for in office procedures reflects the cost of the anesthetic agent and other disposables items including syringes, needles, gauze, instruments, sterilization and drapes 
All of the items for this procedure are purchased from our office general medical supply such as Moore Medical or Henry Schein. 

Bibliography

Aimakhu VE, Ogunbode O. Paracervical block anesthesia for minor gynecologic surgery. Int J Gynaecol Obstet. 1972;10:66–71.
Glanta JC, Shomento S. Comparison of paracervical block techniques during first trimester pregnancy termination. Int J Gynaecol Obstet. 2001; 72:171–178.
Gomez PI, Gaitan H, Nova C, et al. Paracervical block in incomplete abortion using manual vacuum aspiration: randomized clinical trial. Obstet Gynecol. 2004;5:943–951.
Wiebe ER, Rawling M. Pain control in abortion. Int J Gynaecol Obstet. 1995;50:41–46. [View Abstract]
Macarthur A. Other techniques for obstetric pain management. Caudal, paracervical, and pudendal blocks. Tech Regional Anesth Pain Managt. 2001;5:18–23.
Wiebe ER. Comparison of the efficacy of different local anesthetics and techniques of local anesthesia in therapeutic abortions. Am J Obstet Gynecol.  1992;167:131–140. [View Abstract]
2008 MAG Mutual Healthcare Solutions, Inc.’sPhysicians’ Fee and Coding Guide. Duluth, Georgia. MAG Mutual Healthcare Solutions, Inc.2007.
 
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