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  • Nathan Riley, MD

Obgyno Wino Podcast Episode 11 - Obstetric Analgesia and Anesthesia

“The most beautiful thing we can experience is the mysterious. It is the source of all true art and science.” - Albert Einstein

2016 Seven Oaks Cabernet Sauvignon from J. Lohr Vineyards and Wines

PB#209 - Published March 2019

Qualifying labor pain

- 1st stage: visceral (poorly localized)

- 2nd stage: somatic (better localized)

- pudendal nerves and anterior divisions of S2-S4

- visual scales and pain scores are often recommended; I prefer mild/mod/severe; look for brow furrowing and grimacing

***Before getting into pharmacologic pain management, recall that relaxation and breathing techniques, ambulation, swaying, or other movement, hot showers and baths, or partner massage can be extremely effective in managing pain without any associated harm

Opioids

- work a little bit, but overall not great; also significant side effects: drowsiness, nausea, itching, hypotension

- metabolized by liver, eliminated by kidneys

- clearance is slower in newborns, so effects may be prolonged if administered closer to delivery (respiratory depression, neurobehavioral changes, decreased APGARs)

- may cause decreased variability or baseline on FHR tracing


- nalbuphine and butorphanol are mixed agonist-antagonists of opioids receptor, therefore associated with less respiratory depression

- these and the partial agonists like buprenorphine should not be administered with other full opioid receptor agonists as, when combined, you might see (1) decreased analgesia and (2) withdrawal symptoms

- Remifentanil is ultra-short-acting without active metabolites, easily titrated in labor, though a small RCT found increased apneic episodes among women with PCA-controlled remifentanil administration

- NSAIDs, antihistamines, acetaminophen - not as good as opioids


Regional (aka neuraxial) analgesia overview

- >60% of women elect epidural or spinal (subarachnoid space)

- available evidence doesn't suggest that epidurals increases risk of CD nor risk of OVD

- intrathecal opioids compared to IV opioids associated with 90 minutes shorter labor

- epidural compared to no epidural prolongs 2nd stage of labor by 7 minutes on average

- what's in it? local anesthetic + opioid

- bupivacaine or ropivacaine + fentanyl or sufentanil

- local causes the motor blockade

- decreasing the opioid leads to less systemic effect for mom or fetus

- combining the two drugs enables anesthesia to use lower dose of both

- sometimes very dilute epinephrine is added to prolong duration

- sometimes sodium bicarbonate is added to speed up onset of block and/or intensify block

- less need for additional pain relief when compared with opioids


Combined spinal-epidural analgesia

- when CSE is placed, opioid infusion to subarachnoid space then catheter left in place in epidural space

- logic: in early labor, subarachnoid opioid alone is usually sufficient; as labor progresses, pain becomes more somatic, and local anesthesia is generally required

- Cochrane Review comparing CSE with epidural:

  • advantages of CSE: more rapid onset, less need for additional anesthetic, less need for instrumental delivery, lower likelihood of urinary retention

  • no difference in patient mobility, need for labor augmentation, or CD rate

  • when CSE was compared to low-dose epidural, CSE was found to be associated with higher rates of pruritis but no other differences

- Other studies have found higher incidence of fetal bradycardia w/ CSE but no increased CD rate for these FHR abnormalities (fetal brady thought to be direct effect of intrathecal opioids independent of maternal hypotension)

Pudendal nerve block

- useful in facilitating 2nd stage of labor or perineal laceration repair

- compared to spinal, spinal provides better pain relief during labor and delivery but no difference for repairs

- how does it work? blocks sodium channels in nerve cells

- epinephrine can added to potentiate effect; added advantage that it can help you detect intravascular injection (increase HR or BP); thus, better to avoid if underlying maternal cardiac disorder

Inject local anesthetic 2-3 cm medial to the ischial tuberosities bilaterally

Local anesthetic toxicity

- signs and symptoms: neurologic (seizures, coma), cardiac (arrhythmias, myocardial depression)

- notify anesthesia; hypoxemia and acidosis should be corrected immediately by infusing IV lipid emulsion


Nitrous oxide

- inhaled mixture of 50% NO, 50% O2

- compared with epidurals, less effective based on pain scores

- benefits to NO: patient can remain mobile, no additional monitoring, quick onset, quick clearance (also in neonate!)

- can be used in conjunction with other methods of pain management


General anesthesia

- last case resort because it carries risk of aspiration and depression of newborn

- here's how it usually goes:

1) induce with propofol or ketamine

2) muscle relaxant

3) intubation

4) inhaled volatile agents (sevoflurane or isoflurane) - low dose to not adversely affect uterine tone

- higher risk of failed intubation in pregnant patients (1 in 224 failures versus 1 in 390 among non-pregnant females); so LMA can often be helpful


Risks of regional analgesia to mom

- in a review of >300,000 deliveries 30 deaths, 2 cardiac arrests (of 42 total), and 2 myocardial infarctions were related to anesthesia

- 1:60,000 chance of epidural abscess or meningitis

- 1:250,000 chance of epidural hematoma

- 1:4,000 chance of high neuraxial block (equal risk b/w spinal and epidural)

- 1:36,000 chance of serious neurological injury

- 1:10,000 chance of respiratory arrest

- no cases of aspiration, anaphylaxis

- 0.7% chance of spinal headache among all neuraxial procedures involving dural puncture (treat this with epidural blood patch)


Minor adverse effects of neuraxial analgesia

- pruritis (opioid receptor binding), hypotension (sympathetic blockade), nausea and vomiting, fever, shivering, urinary retention, and reactivation of oral herpes

- pruritis is more severe and more common in women who receive intrathecal opioids compared to IV or epidural

- antihistamines are generally ineffective in treating central pruritis; naloxone or nalbuphine are effective but may also lead to decreased analgesic effect

- hypotension seen in 10% of women with low dose neuraxial analgesia: best to pre-load with crystalloids and/or small doses of vasopressors

- lower risk with epidural compared to intrathecal anesthesia due to slower infusion of medication

- fever more common with epidural versus intrathecal


Contraindications to neuraxial anesthesia

- coagulopathy carries increased risk of spinal or epidural hematoma, though still exceedingly rare (1:150,000), slightly higher risk with epidural technique

- thrombocytopenia: regional anesthesia generally contraindicated when platelets <70x10^9/L - space-occupying lesion in the brain carries increased risk of hindbrain herniation with dural puncture (may be OK, however, if no mass effect on imaging)

- Box 1 in PB has a list of indications for anesthesia consult on L&D


Does preeclampsia affect the choice of analgesia or anesthesia?

- decrease in circulating catecholamines associated with better pain control may make it easier to control BPs

- severe preeclampsia also has a protective effect against developing hypotension after spinal anesthesia

- associated thrombocytopenia may preclude neuraxial anesthesia

- avoiding general anesthesia even more important, as intubation techniques can stimulate hypertension (increased risk for stroke and heart failure); laryngeal edema may also make intubation more challenging


Anesthesia and breastfeeding

- opioids can cross placenta or into breast milk and interfere with suckling as the newborn takes much longer to metabolize and clear these drugs

- general anesthesia agents won't affect newborn; OK to start breastfeeding as soon as patient is awake


Anesthesia and analgesia in an emergency

- couple options...bolus a functioning epidural, general anesthesia, or local anesthetic (refer to lidocaine toxicity table)


Managing post-cesarean delivery pain

- preservative-free Morphine (e.g. Duramorph) can be added to intrathecal infusion to achieve ~12-24 hrs of pain-relief (often accompanied by pruritis and nausea, less commonly by respiratory depression)

- consider TAP block, intraperitoneal infusion (20 mL of 2% lidocaine, or 0.25% bupivacaine w/ or w/out epi), or wound infiltration w/ local anesthetic or NSAID

- My practice: scheduled hydrocodone-acetaminophen 5-325 mg PO q4 hrs + Ketorolac 30 mg IV q6 hrs for first 12 hrs, then ibuprofen around the clock w/ hydrocodone-acetaminophen PRN; start Senna 1-2 tablets twice daily; ERAS protocol (early ambulation, early feeding)

- ACOG recommends against daily doses of oxycodone >30 mg (morphine sulfate 45 mg)

- Note: Here is my interview on another podcast called Creogs Over Coffee where I go more in-depth into my post-op pain regimen


Can patients on anti-coagulation receive regional anesthesia?

- aspirin OK

- unfractionated heparin:

  • 10,000 units daily (low-dose, prophylactic): wait 6 hrs after last dose before placing epidural

  • 10,001 - 20,000 (intermediate-dose): wait 12 hrs

  • >20,000 units daily (high-dose): wait 24 hours; also ensure normal PTT and anti-factor Xa level

  • Note: also check platelets to assess for heparin-induced thrombocytopenia

  • Also note: OK to resume 1 hr post epidural catheter removal

- LMW heparin:

  • thromboprophylaxis: wait 12 hrs after last dose to place epidural catheter

  • therapeutic dosing (1mg/kg BID): wait 24 hrs

  • OK to resume 4 hrs post catheter removal

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