Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

AS - 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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Magnesium Sulfate

A

1st choice tocolytic
Vascular, bronchial, & uterine smooth muscle relaxation ↓BP
Depresses motor endplate sensitivity; potentiates NMBDs
Antagonizes α agonists

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Magnesium Sulfate

Preeclampsia Treatment

A

Relaxes VSMC, ↓SVR/BP, anticonvulsant, ↓fibrin deposition improving circulation to visceral organs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Magnesium Sulfate

Neonatal SE

A

Hypotonia & respiratory depression

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Normal 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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

MAGNESIUM

Tocolytic Range

A

Serum Mg2+ 4-8mg/dL

EKG changes: ↑PQ & QRS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

MAGNESIUM

Anticonvulsant

A

7-9mg-dL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

MAGNESIUM

Tendon Reflexes Abolished

A

10-12mg/dL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

MAGNESIUM

Respiratory Depression

A

> 12mg/dL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

MAGNESIUM
SA & AV Block
Respiratory Arrest

A

15-20mg/dL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

MAGNESIUM

Apnea

A

18mg/dL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

MAGNESIUM

Cardiac Arrest

A

25mg/dL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Magnesium Sulfate SE

A 
Transient HoTN*
Sedation*
Skeletal muscle weakness*
CNS depression*
Flushing 
Palpitations
Chest pain
Nausea
Blurred vision
Pulmonary edema
Vascular dilatation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Magnesium Sulfate Overdose

TREATMENT

A
  1. Discontinue infusion
  2. Secure airway
  3. IV calcium chloride admin
  4. Diuresis (Mg2+ excretion)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Magnesium Sulfate Anesthetic Implications

A

HoTN after epidural or general anesthesia administration
Succinylcholine dose NOT reduced for intubation; de-fasciculating doses not required
Reduce non-depolarizing muscle relaxant maintenance doses d/t upregulation
Symptomatic hypocalcemia and respiratory compromise have occurred in myotonic dystrophy cases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Calcium Channel Blockers

A

2nd choice tocolytic
Nifedipine commonly used PO or sublingually
Delays birth b/w 2-7 days when used as tocolytic

19
Q

Ca2+ Channel Blockers MOA

A

Block calcium ions influx through cell membrane
Block calcium release from SR (impairs Ca2+ ability to work on the vascular smooth muscle cells)
Inhibit calcium-dependent myosin light chain kinase mediated phosphorylation → myometrial relaxation
Acts on potassium channels

20
Q

Ca2+ Channel Blockers SE

A 
Hypotension exaggerated w/ neuraxial or general anesthesia
Dyspnea
Pulmonary edema
Tachycardia
Headache
21
Q

Ca2+ Channel Blockers Anesthetic Implications

A

Expect hypotension w/ neuraxial or general anesthesia
Avoid concomitant use w/ Mg2+ sulfate
Potential uterine atony refractory to oxytocin and prostaglandins
- Both act through Ca2+ channels
- Adequate IV access and Methergine to treat uterine atony

22
Q

β2 Agonists

A

3rd choice tocolytic
β2 receptors result in smooth muscle relaxation
Myometrial contractility inhibition
↑progesterone production - progesterone causes histologic changes in myometrial cells that limit contractile impulse spread
Ex: Terbutaline

23
Q

β2 Stimulation Causes

A

↑maternal 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

24
Q

β2 Agonists SE

A 
Maternal & fetal tachycardia
Dysrhythmias
Ischemia
Hypotension d/t vasodilation
Pulmonary edema
Headache
Hyperglycemia
Hypokalemia
↑ plasma renin & vasopressin
25
β2 Agonists Anesthetic Implications
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
26
Nitric Oxide Donors MOA
Nitric oxide - endogenous substance necessary for smooth muscle tone ↑cyclic guanosine monophosphate (cGMP) Inactivates MLCK causing smooth muscle relaxation Example: Nitroglycerin
27
Nitric Oxide Donors SE
Maternal HoTN | Headache
28
Cyclooxygenase Inhibitors
NSAIDs COX inhibitors prevent arachidonic acid conversion to prostaglandin H2 ↓prostaglandin levels ↓uterine contraction Non-selective: Indomethacin COX-2 selective: Celecoxib
29
Cyclooxygenase MOA
COX converts arachidonic acid → prostaglandin H2 Prostaglandins enhance myometrial gap junction formation ↑available intracellular Ca2+
30
COX Inhibitors Anesthetic Implications
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
31
Tocolytics Anesthetic Implications
Neuraxial preferred over general anesthesia Know baseline BP & fluid-volume status Magnesium causes vasodilation; maternal hemorrhage poorly tolerated Succinylcholine muscle relaxant choice for rapid sequence induction Magnesium sulfate potentiates muscle relaxants; no de-fasciculating dose
32
Uterotonics
Uterine atony leading postpartum hemorrhage cause 1. Fundal massage 2. Administer oxytocin
33
Oxytocin
Endogenous hormone produced by posterior pituitary gland - lowers threshold for uterine smooth muscle depolarization (depolarization enhanced by Ca2+ channel activation & ↑prostaglandin production) Synthetic oxytocin (Pitocin, Syntocinon) are octapeptides - Fewer side effects than endogenous oxytocin r/t antidiuretic hormone (water intoxication) 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
34
Oxytocin Anesthetic Implications
Vasodilation and/or ↓SVR Significant hypotension & tachycardia Avoid IV boluses → HoTN
35
Ergot Alkaloids
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? Examples: Methergine (synthetic) & Ergotrate (semi-synthetic)
36
Methergine (Synthetic)
``` 0.2mg IM (deltoid) Contractions occur w/in minutes Repeat dose in 15-20min Total 0.8mg Ø IV bolus administration → Profound hypertension → Severe N/V → Cerebral hemorrhage ```
37
Methergine Anesthetic Implications
Do NOT use: - Pre-existing HTN pregnancy-induced or chronic - 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
38
Prostaglandins
80-90% effective in post-partum hemorrhage refractory to oxytocin and ergot alkaloids Second option when Methergine contraindicated 15-Methylprostaglandin F2a (Hemabate/Carboprost)
39
Prostaglandins MOA
↑myometrial Ca2+ levels subsequently ↑myosin light-chain kinase activity & uterine contraction Reduced need for post-op hysterectomy r/t uterine atony
40
Hemabate
15-Methylprostaglandin F2a (Carboprost) 250mcg IM or directly into the myometrium Repeat 15-30min Max dose 2mg
41
Misoprostol
Prostaglandin E1 Analog Reduced blood loss (as effective as oxytocin) 800-1000mcg sublingual or buccal Not preferable to other uterotonics for active 3rd stage labor management
42
Misoprostol Contraindications
HTN | Active cardiac, pulmonary, renal, or hepatic diseases
43
Prostaglandins Anesthetic Implications
Hemabate (Carboprost) in women w/ reactive airway disease → bronchospasm & ventilation-perfusion mismatch & hypoxemia (asthma patients at risk) - Monitor SpO2 & lung sounds Misoprostol used in patients w/ reactive airway disease or pulmonary hypertension Ø 1st line DOC

AS - N926 Pharmacology (18 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions