T4: nipple (C-sxn) T6: Xiphoid T10: umbilicus

(20% Intralipid) 1. 1.5 mL/kg bolus → 0.25 mL/kg infusion 1. Incremental epi doses 1 mcg/kg rather than large (10 mcg/kg) 1. additional 10 mL/kg bolus if still HD unstable Cardiopulmonary bypass if all else fails!

OB Flashcards by Veronica Robinson

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How do MAC and epidural/spinal requirements change?

MAC dec. 40%

NA dec. 25%

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Epidural space is bound by….

Anteriorly: posterior longitudinal ligament
Posteriorly: ligamentum flavum and the periosteum of the lamina
Laterally: pedicles of the vertebrae, and the intervertebral foramina with their contents
closed at the foramen magnum

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T/F:
The interspinous approach will penetrate the paraspinous muscles.

False
paraspinous approach

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Test Dose

False positives & false negatives

False positives: contractions

false negatives: bradycardia and exaggerated hypertension in response to epinephrine in patients taking β-blockers

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T/F:
Aspirating prior to injecting an epidural dose is sufficient to avoid accidental IV injection.

False
false-negative injection is possible

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Fibers for Vasomotor tone & cardiac accelerator fibers

cardiac accelerators: T1-T4

Vasomotor tone: T5-L1

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Signs of a Subdural injection

A less rapidly appearing high spinal (~15-30 mins)
“Patchy” block
brady, hypotensive, and SOB

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T/F:
Medications injected subdurally will travel higher than injecting epidurally.

True

The spinal subdural space is a potential space that extends intracranially, injections here will travel higher than epidural injections

This is why a subdural injection will result in a high spinal

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Hallmark of PDPH and its S/S

association with body position (relieved by lying flat)

bilateral, frontal, retroorbital, or occipital and extends into the neck
throbbing or constant
photophobia and nausea
diplopia (usually CN VI)
tinnitus

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T/F:
Any epidural catheter might puncture the dura at any time and result in PDPH.

True

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Backache after an epidural may be a sign of…

epidural hematoma and abscess

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Contraindications for Epidurals/neuraxial

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Urinary retention can result from neuraxial. This is caused by blocking which nerves?

S2-S4

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complications of neuraxial

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when does a high spinal become a total spinal?

if the block extends to the cranial nerves

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dermatomes

T4: nipple (C-sxn)
T6: Xiphoid
T10: umbilicus

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Phrenic nerve levels

C 3,4,5

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Why does apnea occur with high spinal?

usually d/t severe sustained hypoTN and medullary hypoperfusion

(rather than phrenic nerve paralysis from blocking C3 to C5).

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Differential blockade

SNS block (temp) 2+ levels higher than sensory block (pain, light touch), which is usually several segments higher than the motor blockade

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What causes the sudden bradycardia, complete heart block, or cardiac arrest
occasionally seen with spinals?

unopposed vagal tone

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Factors for spinal spread

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Lipids for LAST

(20% Intralipid)

1.5 mL/kg bolus → 0.25 mL/kg infusion
Incremental epi doses 1 mcg/kg rather than large (10 mcg/kg)
additional 10 mL/kg bolus if still HD unstable

Cardiopulmonary bypass if all else fails!

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T/F:
LAST can occur with any type of neuraxial anesthesia, including epidurals, spinals and peripheral nerve blocks.

FALSE
not in spinals (dose is too low)

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an LA's potency correlates to its ability to cause...

seizures and cardiac toxicity!

most to least potent/toxic LAs

* most: levobupi, ropivacaine, bupivacaine, tetracaine * intermed: lidocaine & mepivacaine * low: Chloroprocaine

CSF SG

1.003-1.008 at 37°C

What agents can be mixed with CSF in a 1:1 ratio to make them isobaric?

only those that do not have glucose

Hyperbaric solutions travel to the most dependent area. When supine, this would be...

T4-T8

LA toxicity will affect (CNS/cardiac) first

CNS ## Footnote "you'll seize before you asystole"

Max doses for LAs

Which class of LA are longer acting? Why?

amides 1. more lipophilic and protein bound 1. must go to liver for metab

Preggos will these conditions have atypical response to NMBs

polymyositis/dermatomyositis use Roc for RSI (prolonged suxx)

T/F: The placenta is limited in its ability to autoregulate.

True

The uteroplacental circulation is a (low/high)-resistance vascular bed

low

Uterine flow may be reduced by:

1. decrease in uterine arterial pressure 1. increase in uterine venous pressure 1. increase in uterine vascular resistance

Decreased Perfusion Pressure & Increased Uterine Vascular Resistance both decrease uterine flow. What are causes of each?

baseline uterine blood flow & how much does it increase?

50 ml/min to 700-900 ml/min

uterine blood flow is ___% of the CO at term

12%

Equation for uterine blood flow

Describe the respiratory alkalosis that happens in pregnancy

* increased tidal volume (RR unchanged) * Decreased bicarb partially compensates * pH slightly above normal (~ 7.44)

Increased MV in pregnancy due to:

hormonal changes and increase in CO2 production at rest (progesterone is a respiratory stimulant) ## Footnote Vt increases RR does NOT

How does maternal alkalosis affect the curve & fetal O2 delivery?

left shift this increases maternal hgb O2 affinity = less O2 to fetus

Why should mom NOT hyperventilate?

hyperventilation may reduce uterine blood flow and cause fetal acidosis

T/F: Maternal alkalosis and acidosis can both cause fetal acidosis.

True hyperventilation may reduce uterine blood flow and cause fetal acidosis & Maternal hypercapnia can cause fetal acidosis bc fetal PaCO2 correlates directly with maternal PaCO2

Fetal (acidosis/alkalosis) facilitates ion trapping in the fetus.

acidosis ## Footnote fetal acidosis can significantly increase the fetal concentration of drugs such as local anesthetic

How does O2 cross the placenta?

passive diffusion

Pre-eclampsia: the new onset of hypertension and proteinuria after ___ weeks’ gestation

Pre-E diffuse endothelial dysfunction with maternal complications, including:

* placental abruption * pulmonary edema * acute renal & liver failure * Stroke * neonatal complications (preterm, FGR, hypoxic neuro injury, perinatal death)

T/F: Pre-E can occur in the absence of a fetus.

True molar pregnancy

Pre-E Risk Factors

T/F: Smoking cigarettes decreases your risk for Pre-E.

True

Pre-E without severe vs Pre-E with severe

BP in Pre-E without vs with severe features

140/90 160/110

Vessel remodeling in Pre-E

no vessel remodeling!

Pre-E prevention

* low-dose aspirin 12 - 24 W for high risk * mag sulfate for seizure prophylaxis

How does CO change in pregnancy?

+35-40% by the end of the first trimester. 50% by second trimester No changes in third

Why does CO increase in pregnancy?

The initial increase in CO d/t increased HR. CO continues to increase through the second trimester d/t increased stroke volume.

What shows on a pregnant TEG?

hypercoagulability * decreased R & K * increased α angle & max amplitude [MA] * decreased lysis ## Footnote The coagulation profile returns to the nonpregnant state by 2 weeks postpartum

Which coag factors increase/decrease/do not change?

Antiphospholipid Syndrome is at risk for...

* venous & arterial thrombosis * PE * MI * stroke * fetal loss ## Footnote fetal and neonatal thrombosis

Antiphospholipid Syndrome is a/w these conditions

* TIA, stroke * peripheral thrombosis * amaurosis fugax * autoimmune thrombocytopenia * SLE

Antiphospholipid Syndrome Treatment

Heparin (**unfractionated**) prophylaxis & low-dose aspirin throughout pregnancy and up to 6-8 weeks postpartum ## Footnote *history of APS + thrombosis* may require *full* anticoagulation during pregnancy and postpartum

Arachnoiditis

delayed onset of permanent quadriplegia spinal injection of CHG, antioxidant, paraben, or preservative

How to prevent arachnoiditis

wipe away **dried** prep solutions w/ **sterile gauze** to help prevent

prevent unintentional dural puncture

* ID ligamentum flavum * know the likely depth of the epidural space * advance the needle **between** contractions * adequate control of the needle-syringe during advancement * clear the needle of clotted blood or bone plugs

T/F: A successful attempt after a wet tap can cause high levels.

True LA can travel from the epidural space to the subarachnoid space

what causes cranial nerve palsies from a wet tap/dural puncture?

major CSF loss

Wet Tap CN palsies most vulnerable CNs

abducens nerve (VI) is the most vulnerable CNVI, VII, and VIII are the most frequent

Wet Tap CN palsies treatment

prompt PDPH treatment (e.g., epidural blood patch) but even after the blood patch, recovery may be delayed

You accidentally wet tapped, CSF is flowing into the syringe. Why should you **NOT reinject that CSF**?

air will likely also be injected into the subarachnoid space = **pneumocephalus**