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N926 Pharmacology > Tocolytics & Uterotonics > Flashcards

Tocolytics & Uterotonics Flashcards

1
Q

Tocolytics

A

Relax uterus to delay delivery
Inhibit labor via generation or alteration intracellular messengers and/or inhibit synthesis or block action of myometrial stimulant
Administer concomitantly w/ corticosteroids
Onset ≈ 18hrs
Maximum effect at 48hrs

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2
Q

Magnesium Sulfate

A

Vascular, bronchial, & uterine smooth muscle relaxation
Preeclampsia treatment - relaxes VSMC, ↓SVR/BP, anticonvulsant, ↓fibrin deposition improving circulation to visceral organs
Neonatal SE - hypotonia & respiratory depression

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3
Q

Magnesium Sulfate MOA

A

Alter Ca2+ transport & availability for muscle contraction
Complete w/ intracellular Ca2+ → reducing myometrial contractility
Hyperpolarization plasma membrane leads to inhibition myosin light-chain kinase activity
Depress motor endplate sensitivity
Muscle membrane excitability

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4
Q

Magnesium Sulfate Dose

A

Loading dose 4-6g IV over 20-30min
Infusion 1-2g/hr
Therapeutic level 4-9mEq/L
Continue through delivery & 24hrs post-delivery

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5
Q

Serum Magnesium

A 
1.8-3 mg/dL
Tocolytic range 4-8mg/dL
Anticonvulsant 7-9mg/dL
Tendon reflexes abolished 10-12mg/dL
Respiratory depression >12mg/dL
SA/AV blocks (respiratory arrest) 15-20mg/dL
Apnea 18mg/dL
Cardiac arrest 25mg/dL
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6
Q

Magnesium Sulfate SE

A 
Hypotension 
Sedation
Skeletal muscle weakness
CNS depression
Flushing 
Palpitations
Chest pain
Nausea
Blurred vision
Pulmonary edema
Vascular dilatation
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7
Q

Magnesium Sulfate Overdose

A

Discontinue infusion
Secure airway
IV calcium chloride admin
Diuresis

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8
Q

Magnesium Sulfate Anesthetic Implications

A

Hypotension after epidural or general anesthesia administration
Succinylcholine dose not reduced for intubation
Symptomatic hypocalcemia and respiratory compromise have occurred in myotonic dystrophy cases

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9
Q

Calcium Channel Blockers

A

Nifedipine commonly used PO or sublingually

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10
Q

Ca2+ Channel Blockers MOA

A

Block calcium ions influx through cell membrane
Block calcium release from SR
Inhibit calcium-dependent myosin light chain kinase mediated phosphorylation
Acts on potassium channels

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11
Q

Ca2+ Channel Blockers SE

A 
Hypotension exaggerated w/ neuraxial or general anesthesia
Dyspnea
Pulmonary edema
Tachycardia
Headache
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12
Q

Ca2+ Channel Blockers Anesthetic Implications

A

Expect hypotension w neuraxial or general anesthesia
Potential uterine atony refractory to oxytocin and prostaglandins
- Both act through Ca2+ channels
- Adequate IV access and Methergine to treat uterine atony

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13
Q

β2 Agonists

A

β2 receptors result in smooth muscle relaxation
Myometrial contractility inhibition
Increase progesterone production - progesterone causes histologic changes in myometrial cells that limit contractile impulse spread
Ex: Terbutaline

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14
Q

β2 Stimulation

A

↑ blood sugar & insulin levels
K+ redistributed to intracellular compartment lowering levels (as low as 3mEq/L)
Returns to baseline w/in 72hrs
Neonatal hypoglycemia
↑ insulin secretion in response to hyperglycemia
Following delivery glucose load from the mother ceases leading to rebound hypoglycemia
Fetal tachycardia common

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15
Q

β2 Agonists SE

A 
Maternal & fetal tachycardia
Dysrhythmias
Ischemia
Hypotension
Pulmonary edema
Headache
Hyperglycemia
Hypokalemia
↑ plasma renin & vasopressin
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16
Q

β2 Agonists Anesthetic Implications

A

Delay anesthesia for 60min to allow heart rate to decrease
Avoid drugs that increase heart rate - Ketamine, Atropine, Glycopyrrolate, Thiopental, Pancuronium, Etomidate
Monitor IV administration d/t fluid overload & pulmonary edema risk
Treat hypotension w/ Phenylephrine or Ephedrine

17
Q

Nitric Oxide Donors Inhibitors

A

Nitroglycerine
↑ cyclic guanosine monophosphate (cGMP)
Inactivates myosin light-chain kinase causing smooth muscle relaxation

18
Q

Cyclooxygenase Inhibitors

A

NSAIDs
Converts arachidonic acid to prostaglandin H2
Non-selective: Indomethacin
COX-2 selective: Celecoxib

19
Q

COX Inhibitors Anesthetic Implications

A

Platelet inhibition associated w/ non-selective COX inhibitors
Transient & reversible
Neuroaxial anesthesia not contraindicated
Other maternal side effects minimal and have little concern for anesthesia

20
Q

Tocolytics Anesthetic Implications

A

Neuraxial preferred over general anesthesia
Know baseline BP
Maternal hemorrhage poorly tolerated d/t Magnesium vasodilation
Succinylcholine muscle relaxant choice for rapid sequence induction

21
Q

Utertonics

A

Uterine atony leading postpartum hemorrhage cause

  1. Fundal massage
  2. Administer oxytocin
22
Q

Oxytocin

A

Endogenous hormone produced by posterior pituitary gland - lowers threshold for uterine smooth muscle depolarization
Synthetic oxytocin (Pitocin, Syntocinon) are octapeptides
- Fewer side effects than endogenous
- r/t antidiuretic hormone
Routinely administered after delivery
20-40u/L isotonic IV solution over 15-20min
Used prophylactically to reduce blood loss after delivery
Infusions at low controlled rate are used to induce labor

23
Q

Oxytocin Anesthetic Implications

A

Vasodilation or ↓SVR
Significant hypotension & tachycardia
Avoid IV boluses

24
Q

Ergot Alkaloids

A

2nd line uterine atony treatment
Effective to decrease postpartum blood loss & PPH
Produce tetanic uterine contractions restricting their use during post-delivery period
MOA not clear
α adrenergic agonist effect?
Methergine - synthetic
Ergotrate - semisynthetic

25
Q

Methergine

A 
0.2mg IM
Contractions occur w/in minutes
Repeat dose in 15-20min
Total 0.8mg
Ø IV bolus administration
→ Profound hypertension
→ Severe N/V
→ Cerebral hemorrhage
26
Q

Methergine Anesthetic Implications

A

Do NOT use:
- Pregnancy-induced or chronic hypertension
- Peripheral vascular disease or ischemic heart disease (MI risk)
Monitor BP carefully and have vasodilating drugs available
N/V occurs in 10-20% women
Effect on vomiting center - cerebral vasodilation admin phenylephrine

27
Q

Prostaglandins

A

80-90% effective in post-partum hemorrhage refractory to oxytocin and ergot alkaloids
Second option when Methergine contraindicated

28
Q

Prostaglandins MOA

A

↑ myometrial Ca2+ levels subsequently ↑ myosin light-chain kinase activity & uterine contraction
Reduced need for post-op hysterectomy r/t uterine atony

29
Q

Hemabate

A

15-Methylprostaglandin F2a (Hemabate)
250mcg IM
Repeat 15-30min
Total dose 2mg

30
Q

Misoprostol

A 
Prostaglandin E1 Analog
Reduced blood loss
800-1000mcg
Sublingual or buccal
Not preferable to other uterotonics for active 3rd stage labor management
31
Q

Prostaglandins Anesthetic Implications

A

Carboprost (Hemabate) in women w/ reactive airway disease → bronchospasm & ventilation-perfusion mismatch & hypoxemia (asthma patients at risk)
Misoprostol used in patients w/ reactive airway disease or pulmonary hypertension

N926 Pharmacology (17 decks)

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