Mechanisms and Management of an Incomplete Epidural Block for ...

Mechanisms and Management of an Incomplete Epidural Block for ...

Mechanisms and Management of an Incomplete Epidural Block for C-Section DUKE UNIVERSITY A P R I L S C H M I D T, R N, B S N 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 adults Nerve 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 vessel

Compression of the epidural space by increased intra-abdominal pressure -higher block with less volume Increased sensitivity to anesthetics -increased progesterone and endorphins Increased curvature of the spine Case Presentation 28 yo, G1P0, 39+3 gest., 74 kg, Ht 50 Hx: Mixed Connective Tissue Disorder Labor Epidural placed 11 hrs prior-pt

comfortable with high dose Pitocin going C/S indicated for Failure to Progress (72 hrs) Epidural loaded incrementally with a total of 25 ml of Lido 2% with 1:200,000 Epi T4 level achieved, (-) Alyce test Case Presentation Tolerated abdominal and uterine incision

without any pain. Post-delivery pt began to C/O severe pain Tx: Ketamine 15 mg, Versed 2 mg, Duramorph 5 mg per epidural, N20 50%, Propofol boluses (200 mg total) Maintained respirations Recall 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, 2003

Retrospective study n=194 pts whose labor epidurals used for C/S 5/194 (2.6%) required GETA 27/194 (13.9%) required supplemental analgesia/sedation Confirms efficacy in using epidural vs GETA which has a higher mortality rate Efficacy of Extending Labor Epidural for C-Section Halpern et al, 2008

Prospective study n=501 pts whose labor epidural used for C/S 30/501 (5.9%) had an inadequate block 21/501 (4%) required GETA 15/21 requiring GETA occurred intraopertively Linked 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 GETA Closed 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 roots 2) 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, subdiaphragmatic 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 surgeon 2) High parity 3) Advanced gestation 4) Several top-ups required during labor

5) High pain scores in last 1-2 hrs Preventing Epidural Block Failure Saline for LOR (less unblocked segments) Multi-holed catheter Catheter 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 patient Additional 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 2) 3) 4)

5) 6) bolus AND decrease dose by 30-40% to prevent high/total spinal CSA: small incremental doses, PDPH risk CSE: decrease dosing, epidural for supplement Replace Epidural: risk of local toxicity GETA: emergency or regional failure Caudal injection for unblocked sacral

segments Mechanisms of Inadequate Block Presenting Intraop Exteriorization of the uterus Overstretching round ligaments Rough handling of viscera Subdiaphragmatic irritation by blood or amniotic fluid (innervated by C3-C5) Tachyphylaxis to Lidocaine Venous air embolism

Management of Inadequate Block Presenting Intraop Emotional support Local infiltration by surgeon Swabbing 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.

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