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PRETERM LABOR AND DELIVERY

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PRETERM LABOR AND DELIVERY Powered By Docstoc
					        HARRY SINGH, MD
DEPT. OF ANESTHESIOLOGY
                   UTMB
   Preterm Labor 9.5%-1982
   Preterm Labor 11%-1994
   69%-83% Neonatal deaths
   Despite improved care the incidence of preterm
    delivery remains greater than 11% in US
   Current areas of research:
   Determination of causes
   Early identification of women at risk
   Optimal recognition and treatment
   Preterm infant : 20-37 weeks gestation
    or 3 weeks before expected date of delivery

   SGA: Small for gestational age

   Infant weight < 2500 gms at birth-LBW
   Infant weight < 1500 gms at birth-VLBW
   ↑Survival rate with ↑gestational age and birth
    weight
   70%-80% survival in infants weighing 750 to 1000
    gms
   High mortality rate with weight < 750 gms
   24 weeks-Survival 43%
   25 weeks-Survival 74%
   26 weeks-Survival 83%
   Greatest gain achieved by prolonging pregnancy
    beyond 24 weeks gestation
   Survival exceeds 90% by 30 weeks gestation
   90% Preterm births: 30-36 weeks gestation
   Morbidity primary concern at this gestational age
   ↓ Morbidity from RDS > 36 weeks gestation
   ↓ Morbidity from IVH (grade III and IV) > 27 weeks
    gestation
   ↓ Morbidity from necrotizing enterocolitis and
    patent ductus arteriosus > 32 weeks gestation
   History of preterm delivery
   History of diethylstilbestrol exposure
   History of second trimester abortion
   Young age<18 years
   Low socioeconomic status
   Acute or chronic systemic disease
   Trauma
   Abdominal surgery during pregnancy
   Infections: Untreated syphilis, Neisseria
    gonorrhoeae, asymptomatic group B streptococcus,
    acute pyelonephritis, cervicovaginal infections
   Smoking
   Drug abuse
   Overdistention of cavity: multiple gestation,
    polyhydramnios
   Abnormal cavity: uterine anomaly, fibroids
   Foreign body: intrauterine device
   Cervical incompetence
   Trauma to cervix
   Faulty placentation: placenta previa, placental
    abruption
   Genetic abnormality
   Fetal death
   Premature rupture of membranes
   Iatrogenic-50%
   20%-25% Preterm deliveries don’t follow preterm
    labor

   Elective delivery:
   Severe preeclampsia
   Non reassuring fetal heart rate
   Preterm labor vs. false labor
   Criteria for Diagnosis:
   Gestational age between 20-37 weeks
   At least 4 documented uterine contractions in 20
    minutes or 8 in 60 minutes
   Cervical dilation of at least 2 cm
   Cervical effacement of 80%
   Physical examination
   Intravenous hydration
   Bed rest
   Fetal heart rate monitoring
   Ultrasonography for gestational age and weight
   Amniocentesis for fetal lung maturity and to rule
    out infection
   Speculum examination to rule out PPROM
   Gestational age between 20 and 34 weeks
   Fetal weight < 2500 gms
   Absence of fetal distress
   Benefits:↓Neonatal morbidity and mortality
   Risks: Maternal and/or fetal sepsis
   Maternal side effects of tocolytics
   Further compromise of a distressed fetus
   Indicated for the following scenarios:
   To facilitate transport from a small community
    hospital to a tertiary center
   To delay delivery for 24-48 hours allowing
    administration of glucocorticoids to accelerate fetal
    lung maturity
   Fetal resuscitation in utero in fetal distress
   Reduced incidence of respiratory distress syndrome
   Reduced incidence of intraventricular hemorrhage
   Reduction of neonatal morbidity and mortality
   ABSOLUTE:
   Fetal death
   Fetal anomalies incompatible with life
   Fetal distress warranting immediate delivery
   Chorioamnionitis/fever of unknown origin
   Severe hemorrhage
   Severe chronic HTN and/or PIH
   RELATIVE:
   Cervical dilation > 4 cm
   Ruptured membranes
   β-adrenergic agents:
     Ritodrine*
     Terbutaline
   Magnesium sulfate
   Prostaglandin synthetase inhibitor:
     Indomethacin
   Calcium channel blockers:
     Nifedipine

* Ritodrine is only FDA approved tocolytic, however,
  terbutaline, magnesium sulfate, nifedipine and
  indomethacin are widely used in US.
   During labor and delivery, preterm infant at high
    risk of acidosis and has high incidence of
    intracranial hemorrhage
   High incidence of CD due to fetal distress
   Preterm infant more sensitive to depressant effects
    of analgesic and anesthetic drugs.
   Regional anesthesia technique of choice to avoid
    depressant effects of anesthetic drugs.
   Epidural prevents precipitous vaginal delivery and
    rapid decompression of vulnerable fetal head
   Ritodrine and terbutaline commonly used agents
   May delay delivery for 24-48 hrs; however, not in
    substantial prolongation of pregnancy
   Contraindicated in severe cardiac or pulmonary
    disease
   Reported incidence of side effects vary from 0.54% to
    9% as per different studies
   Side effects include hypotension, tachycardia, cardiac
    arrhythmias, myocardial ischemia, pulmonary edema,
    hyperglycemia, hypokalemia and fetal tachycardia
   Side effects dose related
   Consider delaying administration of anesthesia where
    feasible until maternal side effects have subsided
   Extensive experience for use of seizure prophylaxis in
    preeclamptic women
   Little scientific evidence of efficacy of MgSO4 for
    tocolysis
   Many clinicians consider MgSO4 to be tocolytic of
    choice in patients at high risk of bleeding (P. Previa)
   Less frequent and less severe side effects than β-
    adrenergic agents
   Side effects include chest pain, palpitations, nausea,
    transient hypotension, blurred vision, sedation and
    pulmonary edema
   Can attenuate compensatory response to hemorrhage
   Some concern about possible increase in perinatal
    mortality
   May increase risk of hypotension during regional
   Loading dose 4 gm over 15-20 min
   Followed by infusion at 1-4 gm/hr
   Serum levels of 5-7 mg/dl required for tocolysis
   8-10 mg/dl; loss of tendon reflexes
   10-15 mg/dl: respiratory depression
   >10-15 mg/dl: cardiac conduction defects
   Potentiates both depolarizers and non-depolarizers
   Causes sedation, ↓MAC and ↓analgesic
    requirements
   Modest prolongation of bleeding time due to effect
    on platelet aggregation by antagonizing the effects
    of Ca++
   Acts by inhibiting cyclo-oxygenase
   Dose: 50 mg PO followed by 25 mg PO 4-6 hr
   Limit course of therapy to less than 72 hr and
    administer only before 32 week gestation to
    minimize neonatal side effects
   No cardiovascular side effects like other agents
   ↓ thromboxane A2 →↓platelet aggregation
   Does not necessitate assessment of coagulation
    status prior to regional due to transient reversible
    effect on platelet function
   Can cause premature closure of ductus arteriosus
    in utero resulting in persistent fetal circulation if
    administered after 32 weeks gestation
   Other side effects include oligohydramnios and
    neonatal necrotizing enterocolitis
   Reduced side effect profile compared to β-
    adrenergic agonists
   Some investigators suggest as first line tocolytic
    compared to others
   Can arrest labor for 48 hrs or longer
   Can be administered orally or sublingually
   Dose: 10-20 mg PO every 4-6 hours
   More effective with fewer side effects than
    β-adrenergic agents and better neonatal outcome
   However, adverse fetal effects as per some animal
    studies
   Usually mild maternal side effects like flushing
   Potential to cause vasodilatation, hypotension,
    myocardial depression and conduction defects
    when used in combination with volatile agents
   Studies in progress for agents with fewer maternal
    and fetal side effects

   Oxytocin antagonist:
    Atosiban
   Anticytokine agents:
    Urinary trypsin inhibitor
    Cytokines: Promote production of oxytocin and
    corticotropin, corticotropin stimulates
    prostaglandin release
   Nitric oxide donors
   Muir HA, Chestnut DH. Preterm Labor and Delivery
    in Principles and Practice of Obstetric Anesthesia,
    Editor David H Chestnut, Elsevier Mosby, PA.

				
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