OXYTOCIN

Here are the main methods and indications for the use of oxytocin. See also: breech presentation 19.8, and multiple pregnancies 19.11, etc.

Figure 18.8: AN OXYTOCIN TABLE. The dose of oxytocin received by the patient in milliunits per minute depends on the concentration of oxytocin in the bottle and the speed of the drip in drops per minute. The table assumes a standard drip set delivering 15–20 drops per ml. The concentration of oxytocin in the bottle is given in units per litre and not in units per 500 ml, as in the text.

ADJUST THE DOSE to the patient—’titrate it’ against the response. Start with a low dose and increase it until you get the response you need. The dose rate (’drops per minute’) is critical. Always start with a slow rate, and increase it if necessary every half hour, until she has the contractions she needs (usually 2 or 3 contractions every 10 minutes). Don’t give more than 60 drops per minute, or you will give too much fluid. If you need more than 30 drops a minute, double the concentration and halve the drip rate for the next bottle. Note that we give the units of oxytocin to be added to 500 ml of fluid (’one bottle’), and not to one litre.

TO INDUCE LABOUR:

To induce labour between 10 and 28 weeks when the baby is dead (16.4). The uterus is much less sensitive than it is at term, and there is less danger of rupture, so start with 5 units in 500 ml, at 25 drops a minute, and if this does not work, increase the dose the next day, as in Section 16.4. 100 units in 500 ml is the absolute maximum. Read what Section 16.4 has to say about the dangers of water intoxication.

To induce labour at term in primips or in multips <para-4 (19.3). Use 5 units in 500 ml at 10 drops a minute, and increase the speed of the drip to 60 drops/minute as necessary, as in Section 19.3.

If a multip at term is >para-4, use 2.5 units in 500 ml.

If the baby is dead at term, you can use up to 20 units/500 ml, except in multips >para-4.

CAUTION! (1) Whenever you give oxytocin to induce labour, give it by day rather than by night, when monitoring her reliably will be more difficult. (2) You can increase the drip rate, but don’t exceed the concentrations above for particular categories of patients.

TO ACCELERATE LABOUR:

To accelerate labour in primips. Give 2.5 units/500 ml, and don’t increase the concentration. Start at 10 drops a minute and increase the drip rate by 5 drops each half hour as necessary, to a maximum of 60, until you obtain contractions lasting 45–60 seconds at 2–3 minute intervals.

To accelerate labour in multips. This is controversial, so see above. Give the same dose as in primips, but with extra special care! A midwife must monitor the patient all the time. One contributor advises 1 unit in 500 ml. This is also the dose Primary Mother Care advises for the acceleration of labour, and then only in primips.

TO MAKE THE UTERUS CONTRACT AND CONTROL BLEEDING after abortion (16.2) or delivery (19.11a). For this purpose you can give oxytocin as an intravenous infusion, or by bolus intravenous injection. You can also give it by intramuscular injection. For this it is best combined with ergometrine as ’Syntometrine’ (ergometrine 0.5 mg, oxytocin 5 units in 1 ml).

If you are giving oxytocin in an intravenous drip to control bleeding after abortion or delivery, add 20 or (with a PPH) even 40 units (the maximum) to 500 ml of fluid. Usually quite a modest drip rate is sufficient to control bleeding, but in emergency, you can run the drip in ’fast’.

CAUTION! (1) Never give a bolus intravenous injection of oxytocin before the baby has been delivered. (2) Intramuscular injections of ergometrine or oxytocin can only be used safely to empty the uterus and expel the placenta and membranes before 16 weeks. After 16 weeks use an oxytocin drip.