DUKE UNIVERSITYAPRIL SCHMIDT, RN, BSN

Mechanisms and Management of an Incomplete Epidural Block

for C-Section

What have I been up to?

St. John

Baseball and Swimming

Objectives

1) Describe the physiologic changes in the epidural space in the parturient.

2) Be able to list and discuss four major categories of potential causes for inadequate lumbar epidural anesthesia during C-Section.

3) Describe the steps to manage the anesthetic for a parturient with failed or inadequate epidural block during C-Section.

Epidural Anatomy Review

Potential space, surrounds the dura mater posteriorly, laterally, and anteriorly.

Spinal Cord ends at L1 in adultsNerve roots travel as they exit laterally

through the foramen and course outward to become peripheral nerves.

Contents: nerves, fatty connective tissue, lymphatics, venous plexus

Epidural Anatomy

Factors Affecting Epidural Block

Volume: 1-2 ml of LA for each segment to be blocked

Lidocaine: amide LA with rapid onset (5-15 min) DOA (1-3 hrs) Max dose: 5mg/kg (plain) or 7mg/kg (w/ epi)

Epinephrine added to Lidocaine: vasoconstricts slowing absorption and extends length of block

Na+ Bicarb increases speed of onset (more nonionized portion to get into cell quicker)

Parturient: Changes in the Epidural Space

Venous engorgement -more likely to puncture a vesselCompression of the epidural space by

increased intra-abdominal pressure -higher block with less volumeIncreased sensitivity to anesthetics -increased progesterone and endorphinsIncreased curvature of the spine

Case Presentation

28 yo, G1P0, 39+3 gest., 74 kg, Ht 5’0” Hx: Mixed Connective Tissue DisorderLabor Epidural placed 11 hrs prior-pt

comfortable with high dose Pitocin goingC/S indicated for “Failure to Progress” (72

hrs)Epidural loaded incrementally with a total of

25 ml of Lido 2% with 1:200,000 EpiT4 level achieved, (-) Alyce test

Case Presentation

Tolerated abdominal and uterine incision without any pain.

Post-delivery pt began to C/O severe painTx: Ketamine 15 mg, Versed 2 mg,

Duramorph 5 mg per epidural, N20 50%, Propofol boluses (200 mg total)

Maintained respirationsRecall of pain

Questions

Could I have predicted that the epidural was going to fail?

What could I have done differently?Should I have converted to GETA to avoid pain

recall?Theories: 1. Change in pressure in the epidural space redistributing the Lidocaine? 2. Related to Mixed Connective Tissue Disorder?

Efficacy of Extending Labor Epidural for C-Section

Tortosa et al, 2003Retrospective study n=194 pts whose labor

epidurals used for C/S5/194 (2.6%) required GETA27/194 (13.9%) required supplemental

analgesia/sedationConfirms efficacy in using epidural vs GETA

which has a higher mortality rate

Efficacy of Extending Labor Epidural for C-Section

Halpern et al, 2008Prospective study n=501 pts whose labor

epidural used for C/S30/501 (5.9%) had an inadequate block21/501 (4%) required GETA15/21 requiring GETA occurred

intraopertivelyLinked factors: Maternal ht and number of

unscheduled clinician top-ups.

Incidence of Failed or Inadequate Extension of Labor Epidural

Epidurals are used for 29-44% of abdominal deliveries in the U.S.

Incidence of failed/inadequate block is quite variable amongst studies d/t variability of definition of “failed” and “inadequate”.

Up to 20% require supplementation or GETAClosed claims data shows intraop pain during

C/S results in more litigation than non-OB sx

4 Major Categories of Potential Factors for Failed Block

1) Anatomic: septum, large spinal nerve roots2) Technique/Equipment: catheter misplacement

or migration, defects, air used for LOR, inadequate vol., uniport catheter

3) Pt/Sx related: BMI>30, extremes of ht, labor >6hr, hx of spinal sx, exteriorizing uterus, over stretching of round ligaments, sub-diaphragmatic blood

4) Skill level: experience, psychomotor aptitude(Portnoy et al, 2003)

Predicting Block Failure

Important to predict block failure because little can be done when becomes apparent intraop

1) Slow surgeon2) High parity3) Advanced gestation4) Several top-ups required during labor5) High pain scores in last 1-2 hrs

Preventing Epidural Block Failure

Saline for LOR (less unblocked segments)Multi-holed catheterCatheter 2-4 cm in epidural space (prevents

unilateral spread)Using epidural adjuncts has not been proven

to decrease block failure but opioids decrease the amount of LA needed allowing reserve if repeat dose is needed.

Management of Inadequate Block Apparent “Preop”

T4 level needed for adequate analgesia for C/S

Be patientAdditional LA or opioid (Fentanyl)Position changes Pull catheter until 2 cm left in epidural space

(prior to administering LA-helps 46% of the time)

Valsalva or cough may help spread cephalad“EVE”-Epidural Vol. Ext. with NS and dilute

LA

Management of Inadequate Block Apparent “Preop”

1) SAB: wait at least 30 min post epidural bolus AND decrease dose by 30-40% to prevent high/total spinal

2) CSA: small incremental doses, PDPH risk 3) CSE: decrease dosing, epidural for

supplement4) Replace Epidural: risk of local toxicity5) GETA: emergency or regional failure6) Caudal injection for unblocked sacral

segments

Mechanisms of Inadequate Block Presenting “Intraop”

Exteriorization of the uterusOverstretching round ligamentsRough handling of visceraSubdiaphragmatic irritation by blood or

amniotic fluid (innervated by C3-C5)Tachyphylaxis to LidocaineVenous air embolism

Management of Inadequate Block Presenting “Intraop”

Emotional supportLocal infiltration by surgeonSwabbing peritoneal cavity 0.5% Lido (Know

MAX doses)MAC: Versed/Valium, Opioids, Ketamine,

Propofol, N20 50% *Must maintain airway*

GETA with RSI: AFOI if problematic airway

Questions??? Comments?

Has anyone else experienced an inadequate extension of a labor epidural for C/S?

When did it present? Preop? Intraop?

How did you manage it?

References

Halpern, S.H., Soliman, A., Yee, J., Angle, P., & Isocovich, A. (2008). Conversion of epidural labour analgesia to anaesthesia for Cesarean section: a prospective study of the incidence and determinants of failure. British Journal of Anaesthesia, 102 (2), 240-243.

Morgan, G.E., Mikhail, M.S., & Murray M.J. (2006). Clinical Anesthesiology, 4th ed. New York: NY; McGraw-Hill.

References

Portnoy, D. &Vadhera, R.B. (2003). Mechanisms and management of an incomplete epidural block for cesarean section. Anesthesiology Clinics of North America, 21, 39-57.

Tortosa, J.C., Parry, N.S., Mercier, F.J., Mazoit, J.X., & Benhamou, D. (2003). Efficacy of augmentation of epidural analgesia for Caesarean section. British Journal of Anaesthesia, 91 (4), 532-535.

Vercauteren, M. (2006). Failed epidural and spinal: Why do they and what to do? Timisoara, 86-90.