lab dosing schedule during labour

In clinical practice the following drugs are of importance: 1- OXYTOCINE. 2- ERGOMETRINE. 3- PROSTAGLANDINS.

OXYTOCIN (PITOCIN, SYNTOCINONE)

It is an octapeptide hormone released from the posterior lobe of the pituitry gland.

It stimulate contraction of myometrium of pregnant uterus particularly at term. It also stimulate contraction of myoepithelial cells of breast particularly after sucking and cause release of milk.

Clinical Uses:

1* Induction of labour. 2* Augmentation of slow labour. 3* prevention and treatment of post partum hemorrhage (combined with ergometrine). 4* Use as nasal spray to induce lactation. 5* Treatment of abortion.

CONTRAINDICATION1- women of high parity(more than 5).

2- mechanical obstruction to safe normal vaginal delivery such as contracted pelvis or abnormal fetus presentation.

3- previous uterine scar such as caesarean section and myomectomy.

 is an obstetric complication in which the placenta is inserted partially or wholly in lower uterine segment 4- (placenta previa).


ADMINSTRATION AND DOSAGE OF OXYTOCIN
It is given by i.v. infusion, but it is also given as nasal spray but this route show irregular absorption which lead to less contractility.


for induction of labour or to augment slow labour , the common method is to mix 2 units of oxytocin in 500 ml of 5%glucose water solution and start running this at 1 ml (15 drop)/min. this gives approximate dose of 2-4 m unit (milliunits) / min.

This dose is increased gradually at 15 min. interval according to strength and frequency of uterine contraction. This procedure can be done by manual control or infusion pump.

Unwanted effects of oxytocin:1-dose –related hypotension (arising from its vasodilator action ).2-its antidiuretic hormone like action on water excretion →water retention &hyponatraemia.3-inappropriate use can lead to uterine rupture .4-prolonged stimulation of uterus may cause fetal arrhythmias.

ERGOMETRINE (Ergonovine):

It is one of ergot derivatives which act by stimulation of uterine activity. It differ from oxytocin by: moderate dose of oxytocin cause generalized 1- Moderate dose of oxytocin cause contractions of uterus particularly of the fundus segment followed by full relaxation in between contractions . *.

While moderate doses of ergometrine cause contraction of uterus as a whole i.e. Fundus &cervix (tend to compress rather than to expel the fetus )with faster contraction (tetanic contraction ) i.e. no relaxation in between .


2*Oxytocin is given parenterally only while ergometrin is given parenteraly and orally 3* Duration of action of oxytocin is few seconds while ergometrine reach one hour. 4* ergometrine causes vasoconstriction leading to increase blood pressure particularly in already hypertensive patient, patient with peripheral vascular disease and heart disease.

CLINICAL USES OF ERGOMETRINE

1 * Prophylaxis and treatment of post-partum hemorrhage, in normal labour and in caesarean section. 2 * Treatment of bleeding in abortion. 3 * In puerperium if bleeding is heavy.

ADMINSTRATION AND DOSGE OF ERGOMETINE

Side effects of Ergometrine: 1- Vomiting 2- Vasoconstriction ,vasospasm even of the coronary arteries resuling in angina, gangrene 3- Hypertension

Character

Oxytocin
Ergometrine
Contraction
As physiological pattern
Tetanic contraction
Uses
As mentioned
PPH.,mainly
Onset &duration of action
Rapid onset Short duration
Moderate onset Long duration

PROSTAGLANDINS

a)PGE2b)PGF2ά They are modified fatty acids results from enzymatic synthesis from arachidonic acid. It has been suggested that it may play physiological rule during labour:1- Induction of labour when there are fetal or maternal contraindication to oxytocin.2- In case of fetal death in the uterus.-When vaginal delivery is desired for safety of mother or child in cases such as Rh. incompatibility or maternal diabetes mellitus.


They are modified fatty acids results from enzymatic synthesis from arachidonic acid. It has been suggested that it may play physiological rule during labour: 1- Induction of labour when there are fetal or maternal contraindication to oxytocin. 2- In case of fetal death in the uterus. 3-When vaginal delivery is desired for safety of mother or child in cases such as Rh. incompatibility or maternal diabetes mellitus.

ADMINISTRATION AND DOSAGE OF PGs

PGF2 available in 5 mg /ml sterile solution called Dinaprest. They are given i.v. , extra –amniotically, intra-amniotically, vaginal gel or vaginal pessary.1-I.V. ROUTE.:a-5 mg / ml of PGF2α is used for induction of labour when PG is not contra indicated as in asthma . For I V drips, Add 1 ml from ampoule to 1000 ml or 0.5 ml to 500 ml of sterile normal saline or 5 % glucose water, start with 2.5 µg / minute, maintained at least 30 minutes, if good contraction obtained, maintain the rate. If contraction is weak increase the dose to 5 µg / min.


3- INTRAAMNIOTIC It is use for therapeutic termination of pregnancy in a dose of 5 mg/ml solution used from ampule without dilution. Transabdominal tap of amniotic sac with drawn at least one ml of amniotic fluid, then 40 mg (8 ml) of PGF2 slowly injected in the amniotic sac.