Flashcards in Tocolytics Deck (107)
Define Tocolytic Drug :
Any drug use to suppress premature labor
Most Common tocolytics
1)Beta agonist (Ritrodrine or Terbutaline ) but use has declined due to maternal side effects
Maternal (6)side effects of tocolytics: ( TRHAMM)
2.Rarely Pulmonary edema
3.Hyperglycemia + Hypokalemia
Why use caution when using ephedrine and /or Ketamine ?
Premature labor is inhibited until ___________and ___________. What medication is given , and a minimum of _________hours is required.
Until lung mature
Sufficient surfactant is produced .
Give steroids to induce production of surfactant
A minimum of 24- 48 hrs is required
When Tocolytic therapy fails , what becomes necessary
Anesthesia ( for delivery )
Terbutaline : routes, rapid route, duration of effects and MOA of that duration .
Routes: PO, SQ, Inhalation
Rapidly effective by SQ and Inhalation.
Effects persists 3-6 hrs partly bc its structure w/ a RESORCINOL ring preventing COMT action.
Bc of this ring , terbutaline cannot be methylated by COMT
When are the tocolytics Terbutaline and Ritodrine used and how is Ritodrine administered ?
used to manage premature labor contractions through relaxation of myometrium via their B2 effect .
Ritodrine started IV and continued PO if tocolysis is achieved
How is ritodrone metabolized
To inactive conjugated
1/2 is excreted unchanged on the urine
Continuous use of beta agonist prayer has been associated with:
hypokalemia and tachyphylaxis
What is the mechanism of hypokalemia in beta 2 agonists ?
Insulin mediated increase in uptake of extra cellular K+
Increased Na+/K+/ATPase activity .
Pulmonary edema with normal PCWP have been attributed to what medications?
Terbutaline and Ritodrine
All beta adrenergic Tocolytic drugs only have B2 receptor effects . True or False ?
Both B1 and B2 receptor effects
Where are B2 receptors found ? ( PALSSS)
Smooth muscle : Uterus, blood vessels , bronchi , intestine , detrusor , spleen
B2 Smooth muscles : name organs/locations
Ritrodrine and Terbutaline are relatively selective B2 and stimulation of B2 in the myometrium =
Relaxation of the uterine smooth muscle
Other B2 effects such as vasodilation occur as well ( can be undesired ) + some B1 effects
Where are Beta 1 receptors located ?
Predominantly: Heart and adipose tissue .
This results in increased maternal HR and CO ( can be undesired )
MOA Beta Adrenergic Tocolytic Drugs
Agonist>> Beta 2 site on outer membrane of uterine myometrail cells >>activate the enzyme adenyl Cyclase >> adenyl cyclase catalyzes conversion of ATP to cAMP>> rise in intracellular concentration of cAMP = high cAMP concentration >>decrease in available intracellular concentration of calcium + inhibits myosin light chain kinase (MLCK) >> inhibition of MLCK= decrease interaction between actin and myosin = myometrial relaxation
A delay of ____minutes often results in slowing of maternal HR after administration of Tocolytic drug . However ,______, ______and ________ often require anesthesia
15 minutes ;
Advanced labor , non reassuring FH status, and abnormal presentation often require anesthesia
Theoretically, what are the effects of epidural analgesia/anesthesia after beta adrenergic agonist when compared to spinal anesthesia ? And why ?
May cause less hemodynamic compromise than spinal anesthesia
Because of slowe onset of sympathetic blockade .
However this theory remains UNPROVEN
Aggressive hydration in patients on Tocolytic therapy . Any thought ?
Avoid aggressive hydration before and during induction of anesthesia in these patients
Due to :
Risk of pulmonary edema
GA is required in a patient who has recently received beta-adrenergic tocolysis , what agents will you avoid in order to prevent exacerbation of maternal tachycardia
* Maternal tachycardia may make it difficult to asses volume status and depth of anesthesia
Why is it a bad idea to use Halothane on patients on tocolysis ?
Because halothane sensitizes the myocardium to catecholamine-induced-arrhythmias
It should not be used
Why should hyperventilation avoided ?
It will exacerbate the hypokalemia = hyperpolarization of the cell membrane will be potentiated
A study found what effects of terbutaline pretreatment in non-pregnant patients on Succs neuromuscular blockage ?
The terbutaline pretreatment shortened BOTH onset time and recovery time of succs- induced-NMB. Therefore :
May be pro dent to use a nerve stimulator during GA
What are the MOA of Magnesium :
1. Extra cellular Mag = competitive antagonist of calcium either at the motor end plate or cell membrane>> reducing calcium influx into the myocyte .
2. Competes with Ca++ for low affinity calcium-binding sites on outside of the sarcoplasmic reticulum and prevents the rise in free intracellular calcium concentration.
To sum it up :
1. Reduce calcium influx into the myocyte
2.Prevent rise in free intracellular calcium concentration
Hypermagnesemia result in
1) Abnormal neuromuscular function
2) Decrease the release of acetylcholine at the NMJ + decrease the sensitivity of the end plate to acetylcholine
True or False . Per studies , Mag Sulfate results more frequent and more severe CV side effects than beta adrenergic tocolytic agents
Mag Sulfate = less severe and less frequent CV side effects than Tocolytic
Magnesium can have similar effects of beta adrenergic tocolytic agents .what side effects have been reported ?
1.Chest Pain And Tightness
8. May lessen normal compensatory responses to hemorrhage in the mother AND fetus