Induction And Analgesia Druing Labor Flashcards
Tocolytics vs oxytocics
Tocolytics = delay and prevent labor by reducing smooth muscle contractions
Oxytocics (uterotonics) = induce labor by promoting smooth muscle contractions
both pathways converge on myosin light-chain kinase (MLCK)
Myosin light chain kinase (MLCK)
Is essential in smooth muscle contraction
- *myometrial cell relaxation is promoted by phosphorylation/inactivation of MLCK**
- agonism of CRH, PGE2 and B2 receptors on the uterus all induce cAMP dependent phosphorylation
- *MLCK is activated by Ca/calmodulin complex**
- this induces contraction due to increased calcium levels
- agonism of thrombin, oxytocin and PGF receptors promotes contraction
General principles of tocolytic agents
Used to arrest preterm deliveries
- are 80% effective
- usually only used between 24-34 weeks of labor
- preterm deliveries are associated with neonatal respiratory distress syndrome, pulmonary HTN and intracranial hemorrhages
- indicated when delaying delivery up to 48hrs is beneficial to the fetus and vertical dilation is not advanced**
- generally are NOT indicated past 34 weeks gestation
are not agents used to decrease overall occurrence of preterm labor or alleviate complications
Contraindications of tocolytic agent use
note that tocolytic agents can only be used for 48hrs- 1week
Contraindications
- previability
- intrauterine fetal demise
- lethal fetal anomaly
- intrauterine infections
- fetal distress
- severe preeclampsia
- vagina bleeding
- maternal hemodynamically unstable
Two mechanisms of tocolytic agents
Decrease calcium/calmodulin complex availability
Increase phosphorylation of MLCK
COX inhibitors (indomethacin)
MOA: non-specific COX inhibitor/ antagonist tocolytic agent (used to block COX-2 in the uterus though but is not selective since selective agents have serious cardiac issues) which works to decrease available intracellular calcium
- 1st line treatment usually
ADRs:
- inhibited platelet functions
- nausea
- GERD
- emesis
- fetal premature closure of the ductus arteriosus
- fetal oligohydramnios
CONTRAINDICATED AFTER 32 WEEKS
Nifedipine
MOA: CBB blocker that is used for tocolytic between 32-34 weeks and also to treat maternal preeclampsia/eclampsia for its HTN properties
- 1st line if indomethacin is contraindicated or 32-34 weeks
safer than BB agonists which can cause cardiac damage (since Nifedapine doesnt affect nodal tissues)
ADRs:
- peripheral vasodilator (headaches, flushing, dizziness, palpitations)
- hypotension
- NO fetal effects
Terbutaline and ritodrine
MOA: selective B2 agonists on the uterus to up-regulate cAMP phosphorylation of MLCK
- terbutaline is also used for asthma treatments
- both can be used as a 2nd-line agent for tocolytic use in 32-34 weeks gestation
ADRs:
- tachycardia
- hypotension
- pulmonary edema
- hypokalemia and hyperglycemia
- CNS issues (tremor, headache, anxiety, sleep disturbances)
- black box for maternal cardiotoxicity and death (due to also mild b1 agonism effects)
- fetal tachycardia and hypotension
Atosiban
MOA: oxytocin receptor antagonists which work as tocolytic agent to decreased intracellular calcium and calcium/calmodulin complexes
Given IV only
Mimics the effectiveness of terbutaline but has fewer ADRs
- hypersensitivity is possible though!
Magnesium sulfate and nitric oxide
MOA: (magnesium) used as tocolytic agent to block calcium voltage-gated channels (similar to nifedipine). (NO) = used to activate PKG via increased cGMP signaling to up-regulate phosphorylation of MLCK
Are IM only and magnesium can also be used for preeclampsia
ADRs:
- diaphoresis
- flushing
- magnesium toxicity (give calcium gluconate to protect)
- fetal bone abnormalities for long-term exposure
- adjust dose for renal impairment
- *contraindications**
- MG
- cardiac issues present
- hypotension (NO only)
Maternal factors that would signal indicated use for oxytocics/uterotonics
Preeclampsia (mild and severe) Eclampsia HELLP Poorly controlled diabetes (any) Chronic HTN Heart disease Intrauterine infection Augmentation of protracted labor postpartum hemorrhage due to uterine aTony
PGE2 and oxytocin
Are required for onset of parturition and are the most commonly used agents to promote cervical ripening
Produce dose-dependent increases in
- uterine tone
- frequency of contractions
- intensity of contractions
Dinoprostone and Misoprostol
MOA: Both are PGE (PGE2 and PGE1 respectively) analogs used as uterotonic agents
Diniprostone = gel from that is administered intracervically or intravaginally
- remove 30 minutes prior to induction and induce with oxytocin
Misoprostol = tablets that are administered orally, vaginally or rectally
- allow for at least 4 hrs before induction with oxytocin
ADRs:
- fetal bradycardia
- fetal distress
- nausea/vomiting
- fever
- peripartum infections
- uterine hypertonicity and postpartum hemorrhage
Contraindications
- history of asthma
- glaucoma
- MI history
- unexplained vaginal bleeding
- chorioamnionits
- ROM
- previous C-section
Oxytocin
MOA: directly agonist of oxytocin receptors on uterus which increases calcium/calmodulin complexes
- is enhanced by PGE2s
- *always use lowest effective dose and precise IV administration with a continuous-infusion pump**
- increase as needed every 30-60 minutes with a maximum of 20 mU/min
Always need constant observation
MUST discontinue If tachysystole of the uterus (> 5. Contractions/10 minutes) or fetal distress arises
ADRs:
- serious toxicities below (super rare as long as you use low dose)
- off target vasopressin receptor activation = excessive fluid retention and water intoxication (HF, seizures, hyponatremia, etc.)
- excessive uterine contractions which causes transient placental blood flow reduction.
- hypotension
Contraindications
- fetal distress or malpresentations
- placental abruption or risks of uterine ruptures
Non-pharmacologic methods for obstetric pain management
Continuous support during labor
- provide best outcomes
- proper number nurses, midwifes, coaches, educators (changes based on patient)
- fewer operative vaginal or C-section deliveries
- fewer requests for pain medication
Warm baths and acupuncture
little evidence for = acupressure, hypnosis, TENS, breathing techniques, but if it helps the psychology of the patient then go for it
