Pharmacology Flashcards
Indications to promote UTERINE CONTRACTIONS
Postpartum hemorrhage 2° to uterine atony. Induction of labor, cervical ripening, and pregnancy termination are secondary indications.
Pitocin (Dosing)
Promotes Uterine Contractions
Dosing: Uterine Atony- 20 to 40 units in 1 liter of crystalloid solution administered over 15-30 minutes. Induction of labor- 1 to 40 milliunit per minute.
Look out for: ↓BP and ↑HR 2° vasodilation with bolus.
Methergine (methylergonovine)
Dosing
Promotes Uterine Contractions.
Dosing: 0.2mg intramuscularly, NEVER IV! 15 minute intervals to max dose of 0.8mg.
Look out for: ↑↑BP leading to pulmonary edema, cerebral hemorrhage, MI, emesis and/or retinal damage.
Contraindicated: chronic hypertension, preeclampsia, peripheral vascular disease, and ischemic heart disease.
Hemabate/Carboprost (15-methyl PGF2α) and Misoprostol (PGE1 analog)
Dosing
Promotes Uterine Contractions
Dosing: Hemabate for uterine atony- 250µg (micrograms) intramuscularly or intramyometrially, NEVER IV! 15 minute intervals to max dose of 1mg.
Look out for: Bronchoconstriction and hypoxemia
Contraindicated: reactive airway disease, cardiac disease and pulmonary hypertension.
Indications to promote UTERINE RELAXATION
Preterm labor, uterine inversion, uterine tetany, retained placenta, and fetal head entrapment.
Magnesium Sulfate (Dosing)
Promotes Uterine Relaxation
Dosing: IV bolus of 4-6g over 20 minutes, continued as infusion of 1-2g per hour.
Look out for: ↓BP after bolus. Muscle weakness. Defasciculating dose of NDNMB should be avoided, succinylcholine dose should not be changed but maintenance dose of NDNMB should be decreased. If magnesium toxicity occurs: Calcium Chloride (10-15mg/kg) or Calcium Gluconate (10-15mg/kg) over 10 minutes IV.
Magnesium Sulfate Levels
Level (mEq/L) Effects
1.5-2 Normal plasma level
4.0-9.0 Therapeutic Level
5.0-10.0 ECG changes (P-Q interval prolongation,
widened QRS complex)
10 Loss of deep tendon reflexes
15 SA and AV block, respiratory paralysis
25 Cardiac Arrest
Ritodrine and Terbutaline (Dosing)
Promotes Uterine Relaxation
Dosing: Uterine hypertonus or non-reassuring fetal status- 0.25mg IV or SQ. Infusion of 0.01 to 0.08mg/minute titrated to a maternal HR of 20% above baseline.
Look out for: Vasodilation. Maternal/fetal ↑HR, MI, dysrhythmia, or pulmonary edema (from β-2 mediated increased in pulmonary capillary permeability). Gluconeogenesis and glycogenolysis. Avoid agents that increase HR. Contraindicated: Significant cardiac disease or uncontrolled diabetes.
Nifedipine and Nicardipine (Dosing)
Promotes Uterine Relaxation
Dosing: Nifedipine 10-20 mg PO or SL q4-6 hours. Large bore IV (18 gauge or greater) and type and screen should be obtained.
Look out for: ↓BP, refractory postpartum hemorrhage.
Indomethacin and Ketorolac (Dosing)
Promotes Uterine Relaxation
Dosing: Indomethacin- 50mg loading dose PO or PR, followed by 25mg q4-6h. Ketorolac 30mg q6h IV or IM.
Contrainidcations: renal insufficiency, bleeding diathesis, and aspirin induced asthma. Administration prior to 32 weeks gestation.
Nitroglycerin (Dosing)
Promotes Uterine Relxation
Dosing: Profound, short duration uterine relaxation- 50-200µg (micrograms) IV. May repeat up to 500µg (micrograms). 2.5mL in 250mL bag = 50mcg/mL.
Look out for: transient hypotension and maternal headache.
Stadol (Butorphanol)
Dosing
Breakthrough pain- 1-2mg IV/IM q3-4h.
Look out for: Dysphoria, increased cardiac work, and increased pulmonary artery pressure.
Nubain (Nalbuphine)
Dosing
Pruritus- 3-4mg q3-6hrs IV. Breakthrough pain- 10-20mg q3-6hrs IV.
Look out for: Dysphoria, increased cardiac work, and increased pulmonary artery pressure.
Remifentanil (Dosing)
Dosing: (100mcg/ml) start dosing at 20mcg/injection or 0.25mcg/kg IBW, increase 10-20mcg, delay 5-10 mins, NO BASAL rate.
Duration of action: 5-10 mins. Fetal esterases are nearly fully developed at birth. One on one nursing care, continuous pulseox.
Uterine Physiology
Blood flow increase from 75ml/min (pre-pregnancy) to 800ml/min (term) or 15% of cardiac output.
Vascular response: ↑ α-1 sensitivity and nitric oxide (NO) release, ↓ endogenous vasoconstrictor (angiotensin II and endothelin) sensitivity.
Oxytocin: ↑ in number of receptors later in pregnancy starting at 20 weeks.