OXYTOCIN

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OXYTOCIN

• Dr.Dhanalakshmy DNB (OG)

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• OXYTOCICS
• are the drugs of varying chemical nature that
  have the power to excite contraction of the
  uterine muscles.

Ergometrine Methergin
PGE2 PGF2?
E2F2?
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Oxytocin physiology

• Human hypothalamus

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PREPARATIONS

• Synthetic Oxytocin (Ptocin) 5 IU/ ml amp
• Syntometrine 5 U Oxytocin 0.5 mg Ergometrine
• Desaminooxytocin buccal tablets 50 IU
• Oxytocin nasal spray 40 IU/ ml

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UTERUS

• Oxitocin is the primary mediator of myometrial
  contractility during labor.
• During the second half of pregnancy, uterine
  smooth muscle shows an increase in the expression
  of oxytocin receptors(100-200fold) and becomes
  increasingly sensitive to the stimulant action of
  endogenous oxytocin.
• Stimulates PG synthesis.
• Physiological uterine contraction - fundal
  contraction cervical relaxation. (law of
  polarity maintained)
• Cervical and vaginal dilatation results in an
  acute release of oxytocin from the posterior
  pituitary in a process known as the Ferguson
  reflex.

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During lactation
STIMULUS
RESPONSE
myoepithelial cells contract
Axon terminals
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CVS

• In small doses Oxytocin produces vasodialation by
  direct relaxation of the vascular smooth muscles
• Transient hypotension flushing followed by
  tachycardia are observed

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KIDNEY

• In high concentration Oxytocin has weak
  antidiuretic pressor activity due to activation
  of vasopressin receptors

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ABSORPTION, METABOLISM, AND EXCRETION

• Intravenously (controlled infusion) for
  initiation and augmentation of labor.
• intramuscularly -control of postpartum bleeding.
• Buccal nasal spray- Limited use.
• Oxytocin is not bound to plasma proteins and is
  eliminated by the kidneys and liver.
• Circulating half-life of max. 5 minutes. (avg
  3-4min) as plasma, utrine placenta of pregnant
  women contain enzyme oxytocinase
• Circulating half life is 10 to 15 mins in non
  pregnant women

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ADMINISTRATION

• IV controlled infusion for initiation
  augmentation of labour , abortions
• IM for Post partum haemorrage
• Buccal , Nasal spray for lactation

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Toxicity

• serious toxicity is rare when oxytocin is used
  judiciously.

HYPER
STIMULATION
fetal distress
Grand multipara, Malpresentation Contracted
pelvis Prior uterine scar (hyterotomy)

• NOTE These complications can be detected
• early by means of
• standard fetal monitoring equipment.

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Inadvertent activation of vasopressin receptors-
40-50IU/min
Seizures death
30-40mIU/min
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OXYTOCIN BOLUS
HYPOTENSION
Transient vasodilation

• To avoid hypotension, oxytocin is
• administered intravenously as
• dilute solutions at a controlled rate.

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INDICATIONS
To minimise blood loss. Control PPH
-To accelerate Abortion (inevitable,
Missed). -Molar preg. -To stop bleeding. -Inductio
n of Abortion.
To induce labour. For cervical ripening.

• Augmentation of
• labour.
• Uterine inertia.
• Active management
• of 3rd stage

Contraction stress test (CST)
DIAGNOSTIC
Oxytocin sensitivity test (OST)
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Contraindications

• PREGNANCY
• Grand multipara
• malpresentation
• contracted pelvis
• cephalopelvic disproportion
• prior uterine scar (hysterotomy)

• LABOUR
• All cont. in preg.
• Obstructed labour
• Incoordinate uterine contraction
• FETAL DISTRESS
• prematurity

• ANY TIME
• Hypovolemic state
• Cardiac disease

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For induction of labour

• Principle
• Start with LOW DOSE, escalate to achieve optimal
  response
• (3contraction in 10min each lasting 45sec)
• Maintain the dose- oxytocin titration technique.
• OBJECTIVE- Maintain normal pattern of uterine
  activity till delivery and 30-60min beyond that.
• NOTE
• Start with 4mU/min ?every 20min
• Semi-Fowlers position - avoid venecaval
  compression.

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Calculation of dose delivered in milliunits(mU)
its correlation with drop rate per minute
Units of oxytocin mixed in 500ml Ringer solution 1unit1000 miliunits(mU) Drops per minute (15drops1ml) 15 30 60 In terms of mU/min
1 2 5 2 4 8 4 8 16 10 20 40
NOTE In majority of cases, max. response is seen
with 16 mU/min i.e 2U in 500ml RL at 60 drops
per min
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OBSERVATION DURING OXYTOCIN INFUSION

• RATE of flow calculating drops/min
• Uterine contraction - Finger tip palpation
  (hardening)
• Intra uterine pressure-peak 50to60mmHg resting
  10to15mmHg
• FHR
• Assessment of progress of labour - descent of
  presenting part dialatation of cervix

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Indications for stopping the oxytocin infusion

• Nature of uterine contractions-
• abnormal uterine contractions occurring
  frequently (every 2 min or less )
• lasting more than 60sec(hyperstimulation)
• ?tonus in between contractions
• Fetal distress
• Maternal complications
• Hyper stimulation is treated with 0.25 mg
  terbutalin

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THANK YOU
?