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N934 Advanced Principles of Anesthesia II > Tocolytics & Uterotonics > Flashcards

Tocolytics & Uterotonics Flashcards

1
Q

purpose of tocolytics

A
  • delay delivery
  • can be administered concomitantly with corticosteroids –> prior to 33 weeks gestation to reduce neonatal risk
  • onset approximately 18 hours, max benefit at 48 hours
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2
Q

corticosteroids prevent what risks to the neonate?

A
  • RDS
  • IVH
  • NEC
  • perinatal death
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3
Q

what are the tocolytic drugs?

A
  • magnesium sulfate
  • calcium channel blockers
  • beta adrenergic agonists
  • nitric oxide donors
  • cox inhibitors
  • oxytocin antagonists
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4
Q

how do tocolytics inhibit labor?

A
  • generation or alteration of intracellular messengers

- inhibiting synthesis of block action of a myometrial stimulant

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5
Q

MOA of magnesium sulfate

A
  • alters calcium transport and availability of Ca2+ for muscle contraction
  • competes with intracellular calcium to reduce myometrial contractility
  • hyperpolarization of plasma membrane leads to inhibition of myosin light chain kinase activity as magnesium
  • RELAXATION of vascular, bronchial and uterine smooth muscles
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6
Q

mag for treatment of preeclampsia

A
  • relaxes vascular smooth muscle to decrease SVR and BP
  • anticonvulsant
  • decreases fibrin deposition, improving circulation to visceral organs
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7
Q

neonatal side effects of mag

A
  • hypotonia

- respiratory depression

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8
Q

mag dose/admin directions

A
  • loading dose 4-6 g IV over 20-30 min
  • followed by infusion of 1-2 g/hr
  • continue through delivery and up to 24 hours post delivery
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9
Q

normal serum mag level

A

1.8-3 mg/dL

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10
Q

tocolytic range for magnesium

A

4-8 mg/dL

-can have EKG changes here like P-Q elongation and widened QRS

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11
Q

anticonvulsant range for mag

A

7-9 mg/dL

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12
Q

at what level does magnesium cause cardiac arrest?

A

25 mg/dL

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13
Q

side effects mag sulfate

A
  • decreased BP (transient)
  • antagonism of alpha agonist
  • potentiation of NDMRs/skeletal muscle weakness
  • flushing
  • palpitations
  • chest pain
  • nausea
  • blurred vision
  • sedation
  • CNS depression
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14
Q

mag sulfate OD treatment priorities

A
  • d/c mag infusion
  • secure airway
  • IV admin of calcium chloride or gluconate
  • diuresis
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15
Q

mag sulfate anesthetic implications

A
  • exaggerated HoTN after epidural or admin of GA
  • succ does not reduced and defasciculating doses not required
  • reduce maintenance dose of NDMR
  • symptomatic hypocalcemia and respiratory compromise have occurred in cases of myotonic dystrophy
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16
Q

common calcium channel blocker for tocolytic use

A

nifedipine because can be given PO or sublingual

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17
Q

Ca2+ channel blockers MOA

A
  • block influx of calcium ions through cell membrane
  • block release of calcium from the SR
  • inhibit calcium dependent MLCK-mediated phosphorlyation which leads to myometrial relaxation
  • also act on potassium channels
  • when used as tocolytic, birth delayed between 2-7 days
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18
Q

side effects of calcium channel blockers

A
  • hypotension
  • dyspnea
  • pulmonary edema
  • tachycardia
  • HA
  • avoid concomitant use with mag sulfate (bc will enhance NMB effects and affect cardiac and resp function)
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19
Q

calcium channel blocker anesthetic implications

A
  • expect HoTN with admin of neuraxial or GA
  • potential uterine atony that may be refractory to oxytocin and prostaglandins
  • methergine if atony occurs
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20
Q

Beta 2 agonist MOA

A
  • stimulation of beta 2 receptors results in smooth muscle relaxation
  • inhibition of myometrial contractility
  • increase progesterone production which causes changes in myometrial cells to limit contractile impulses
21
Q

common B2 agonists used as tocolytics

A

terbutaline

22
Q

main hazards of B2 agonist as tocolytic

A
  • increased blood sugar and insulin levels in mom (increases w/in few hours and returns to normal at 72 hours)
  • potassium redistributed to intracellular compartment; low level can reach 3 mEq/L
  • neonatal hypoglycemia due to increased insulin secretion in response to hyperglycemia
  • fetal tachycardia also common
23
Q

beta 2 agonists side effects

A
  • maternal/fetal tachycardia
  • dysrhythmias
  • ischemia
  • hypotension
  • pulmonary edema
  • HA
  • hyperglycemia
  • hypokalemia
  • increased plasma renin and vasopressin
24
Q

anesthetic implications of beta2 agonist as tocolytic

A
  • delay anesthesia for 60 min to allow HR to decrease
  • avoid drugs that increase HR - ketamine, atropine, glyco, thiopental, pancuronium, etomidate
  • monitor IV admin due to risk of fluid overload and pulmonary edema
  • treat hypotension with phenylephrine and/or ephedrine
25
Q

nitric oxide donor tocolytic MOA

A
  • endogenous substance necessary for smooth muscle tone
  • acts by increased cyclic guanosine monophosphate (cGMP)
  • cGMP inactivates MLCK causing smooth muscle relaxation
26
Q

nitric oxide donor side effects

A
  • maternal HoTN common

- HA

27
Q

COX inhibitors as tocolytic MOA

A
  • COX converts arachidonic acid to prostaglandin H2 (which is a substrate for tissue specific enzymes critical to giving birth)
  • prostaglandins enhance formation of myometrial gap junctions and increase avail intracellular calcium
  • so COX inhibitors reduce prostaglandin levels which inhibit COX enzymes and result is decreased uterine contraction
28
Q

COX-inhibitors used for tocolytics

A
  • indomethacin (non-selective)

- celebrex (COX-2 selective), tocolytic efficacy equal to Mg in preventing preterm birth within 48 hours

29
Q

COX inhibitors anesthetic implications

A
  • plt inhibition associated with non-selective COX (transient and reversible; neuraxial NOT contraindicated)
  • other maternal side effects are MINIMAL
30
Q

oxytocin receptor antagonist

A

atosiban

31
Q

atosiban MOA

A
  • blocks normal effects of oxytocin in uterus
  • stimulates contractions by converting phosphatidylinositol triphosphate to inositol triphosphate
  • IP3 binds to protein in SR causing calcium release in cytoplasm
32
Q

atosiban facts

A
  • not approved for use in US
  • reports of fetal death associated with use of drug before 28 weeks gestation
  • myometrium DOES remain sensitive to oxytocin
33
Q

uterotonics

A

-stimulate uterine contraction

34
Q

PPH leading cause

A
  • uterine atony

- admin of oxytocin

35
Q

oxytocin

A
  • endogenous hormone produced by post pit gland
  • lowers threshold of depolarization of uterine smooth muscle
  • synthetic oxytocin = octapeptide; fewer S/E than endogenous oxytocin
  • routinely administered after delivery
36
Q

dose post-delivery of oxytocin

A

20-40 units/L if isontonic solution IV over 15-20 min

37
Q

oxytocin uses in obstetrics

A
  • used prophylactically to reduce blood loss after delivery

- infusions at low controlled rate are used to induce labor

38
Q

oxytocin anesthetic implications

A
  • causes a degree of vasodilation or decreased SVR which can result in significant hypotension and tachycardia
  • associated with IV bolus of oxytocin normally so AVOID bolus
39
Q

Ergot Alkaloids as uterotonic

A
  • second line treatment for uterine atony
  • effective for decreasing postpartum blood loss and PPH
  • produce tetanic uterine contractions restricting their use during postdelivery period
40
Q

examples of ergot alkaloids

A
  • methergine = synthetic

- ergotrate = semisynthetic

41
Q

Ergot alkaloids MOA

A

-not clear but thought to be an alpha adrenergic agonist effect

42
Q

methergine dose

A
  • 0.2 mg IM
  • contractions occur within minutes of admin
  • dose may be repeated in 15-20 min
  • total max dose 0.8 mg
43
Q

IV admin of methergine causes what?

A
  • profound hypertension
  • severe N/V
  • cerebral hemorrhage
44
Q

ergot alkaloids anesthetic implications

A
  • do not use in women with HTN; pregnancy induced or chronic; do not use in those with PVD or ischemic heart disease
  • monitor BP carefully and have vasodilating drugs available
  • N/V occurs in 10-20% of women
45
Q

prostaglandins

A
  • 80-90% effective in PPH refractory to oxytocin and ergot alkaloids
  • drug = hemabate, carboprost
46
Q

prostaglandins MOA

A

-increases myometrial calcium levels and subsequently increases MLCK activity and uterine contraction

47
Q

hemabate dose

A
  • 0.25 mg IM or directly into myometrium

- repeat Q15-30 min to a total dose of 2 mg

48
Q

misoprostol

A
  • prostaglandin E1 analog
  • reduced blood loss at C-section and is as effective as oxytocin
  • dose = 0.8-1 mg (administered sublingual or buccal)
49
Q

prostaglandins anesthetic implications

A
  • all of these drugs have detrimental side effects
  • use of carboprost in women with RAD can result in bronchospasm, V/Q mismatch and hypoxemia
  • monitor O2 sats and lung sounds
  • misoprostol can be used in patients with RAD or pulm HTN

N934 Advanced Principles of Anesthesia II (17 decks)

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