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引產病人之選擇：
 適應項目：
懷孕引起之高血壓（Pregnancy
induced hypertention）
早期破水（Premature
rupture of membranes）
絨毛羊膜炎（Chorioamnionitis）
經由生化或生理評估，懷疑胎兒有危險者
（例如胎兒生長遲滯、過期妊娠、同種免疫isoimmunization）
母體內科問題（例如糖尿病、腎臟病、慢性阻塞性肺部疾病）
胎兒死亡
地域問題（離醫院太遠，擔心急產）
過期妊娠
禁忌項目：
胎盤或血管前置（Placenta
or vasa previa）
胎位不正
臍帶先露（Cord
presentation）
先前做過縱向子宮切開（Classical
incision）
生殖器官感染活性期庖疹
骨盆腔不正常結構
侵犯性子宮頸癌
Bishop scores：（評估子宮頸之狀況）
|
|
0 |
1 |
2 |
3 |
|
Dilatation (cm) |
0 |
1 ~ 2 |
3 ~ 4 |
5 ~ 6 |
|
Effacement |
0 ~ 30% |
40 ~ 50% |
60 ~ 70% |
80% |
|
Station |
-3 |
-2 |
-1 ~ 0 |
+1 ~ +2 |
|
Consistency |
Firm |
Medium |
Soft |
¾ |
|
Position |
Posterior |
Mid |
Anterior |
¾ |
常用方式：
Prostaglandin E2
PG E2
(0.5
mg/tab) P.O.
1#
q1h
´
dose/day。
Prostin E2
(3
mg/vaginal tablet), by a further
3
mg after
6
~
8
hrs if necessary, a total dose
£
6
mg。
PGE2不僅可促使子宮頸成熟，也可成功地引產，降低產程延長之機會，增加子宮收縮及降低子宮收縮素之要求。對於初產婦且有未成熟之子宮頸，PGE2效用大於人工破水及子宮收縮素。
Oxytocin (Piton-S):
10
unit/ml/amp
Medical induction or augmentation of labor。促進子宮收縮，預防產後出血等。
Piton-S
5U
in D5W
500
ml run
6
mgtt/min (30
min later)
ò
Piton-S run
12
mgtt/min
（30
min later）
ò
Piton-S run
20
mgtt/min
（30
min later）
ò
Piton-S run
30
mgtt/min
（30
min later）
ò
Piton-S run
40
mgtt/min
（30
min later）
ò
Piton-S run
50
mgtt/min
（30
min later）
ò
Piton-S run
60
mgtt/min
（30
min later必要時換成大滴，但須注意最大劑量及I/O）
ò
Piton-S run
20gtt/min
（30
min later）
ò
Piton-S run
30
gtt/min （30
min later）
ò
Piton-S run
40
gtt/min （30
min later）
ò
Piton-S run
50
gtt/min （30
min later）
ò
Piton-S run
60
gtt/min （Maximal）（60
mgtt =1
ml;
1gtt
=
4
mgtt）
調整子宮收縮素之劑量直到每10分鐘約有3
~
4次之宮縮即可。
Amniotomy
人工破水可安全且有效地引產或促進產程，人工破水之所以會引起宮縮，是由於產生了前列腺素，而內因性的子宮收縮素可能沒有此項作用。
產婦有不錯之子宮頸（Bishop
score大於等於9分），人工破水會引發成功之生產，此種產婦偶而需要子宮收縮素來加強。人工破水對於引產也有助益，擁護積極處理產程者認為人工破水是一關鍵因素，而他們的主張也由於有關子宮頸擴張大於3公分後使用人工破水而縮短產程之研究得到印證。
在人工破水之前需先確定胎頭已經在好的子宮頸位置，人工破水之後應立即記錄胎心音，產程通常會很快開始，此時可給予適當劑量之子宮收縮素。
Induction and Augmentation of labor
Induction of labour and
augmentation of labour are performed for different indications but the
methods are the same.
• Induction of labour: stimulating the uterus to begin labour.
• Augmentation of labour: stimulating the uterus during labour to
increase the frequency, duration and strength of contractions.
A good labour pattern is established when there are three contractions in
10 minutes, each lasting more than 40 seconds.
If the membranes are intact, it is recommended practice in both
induction and augmentation of labour to first perform artificial rupture
of membranes (ARM). In some cases, this is all that is needed to induce
labour. Membrane rupture, whether spontaneous or artificial, often sets
off the following chain of events:
- Amniotic fluid is expelled;
- Uterine volume is decreased;
- Prostaglandins are produced, stimulating labour;
- Uterine contractions begin (if the woman is not in labour) or become
stronger (if she is already in labour).
ARTIFICIAL RUPTURE OF MEMBRANES
• Review for indications.
Note: In areas of high HIV prevalence it is prudent to leave the
membranes intact for as long as possible to reduce perinatal transmission
of HIV.
• Listen to and note the fetal heart rate.
• Ask the woman to lie on her back with her legs bent, feet together and
knees apart.
• Wearing high-level disinfected gloves, use one hand to examine the
cervix and note the consistency, position, effacement and dilatation.
• Use the other hand to insert an amniotic hook or a Kocher clamp into the
vagina.
• Guide the clamp or hook towards the membranes along the fingers in the
vagina.
• Place two fingers against the membranes and gently rupture the membranes
with the instrument in the other hand. Allow the amniotic fluid to drain
slowly around the fingers.
• Note
the colour of the fluid (clear, greenish, bloody). If thick meconium is
present, suspect fetal distress.
• After ARM, listen to the fetal heart rate during and after a
contraction. If the fetal heart rate is abnormal (less than 100 or
more than 180 beats per minute), suspect
fetal distress.
• If delivery is not anticipated within 18 hours, give prophylactic
antibiotics in order to help reduce Group B streptococcus infection in the
neonate:
- penicillin G 2 million units IV;
- OR ampicillin 2 g IV, every 6 hours until delivery;
- If there are
no signs of infection after delivery, discontinue antibiotics.
• If good labour is not established 1 hour after ARM, begin
oxytocin infusion.
• If labour is induced because of severe maternal disease (e.g.
sepsis or eclampsia), begin oxytocin infusion at the same time as ARM.
INDUCTION OF LABOUR
ASSESSMENT OF THE CERVIX
The success of induction of labour is related to the condition of the
cervix at the start of induction. To assess the condition of the cervix, a
cervical exam is performed and a score is assigned based on the criteria
in Table P-6:
• If the cervix is favourable (has a score of 6 or more), labour is
usually successfully induced with oxytocin alone.
• If the cervix is unfavourable (has a score of 5 or less), ripen
the cervix using prostaglandins or a Foley catheter before induction.
TABLE P-6 Assessment of cervix for induction of labour
|
Factor |
Rating |
|
0 |
1 |
2 |
3 |
|
Dilatation (cm) |
closed |
1–2 |
3–4 |
more than 5 |
|
Length of cervix (cm) |
more than 4 |
3–4 |
1–2 |
less than 1 |
|
Consistency |
Firm |
Average |
Soft |
- |
|
Position |
Posterior |
Mid |
Anterior |
- |
|
Descent by station of head (cm from ischial spines) |
-3 |
-2 |
-1,
0 |
+1,
+2 |
|
Descent by abdominal palpation (fifths of head palpable) |
4/5 |
3/5 |
2/5 |
1/5 |
OXYTOCIN
Use oxytocin with great caution as fetal distress can occur from
hyperstimulation and, rarely, uterine rupture can occur. Multiparous women
are at higher risk for uterine rupture.
Carefully observe
women receiving oxytocin.
The effective dose of oxytocin varies greatly between women. Cautiously
administer oxytocin in IV fluids (dextrose or normal saline), gradually
increasing the rate of infusion until good labour is established (three
contractions in 10 minutes, each lasting more than 40 seconds). Maintain
this rate until delivery. The uterus should relax between contractions.
When oxytocin infusion
results in a good labour pattern, maintain the same rate until delivery.
• Monitor the woman’s pulse, blood pressure and contractions and check the
fetal heart rate.
• Review for indications.
Be sure induction is
indicated, as failed induction is usually followed by caesarean section.
• Ensure that the woman is on her left side.
• Record the following observations on a partograph every 30 minutes:
- rate of infusion of oxytocin (see below);
Note: Changes in arm position may alter the flow rate;
- duration and frequency of contractions;
- fetal heart rate. Listen every 30 minutes, always immediately after a
contraction. If the
fetal heart rate is less than 100 beats per minute, stop the
infusion.
• Infuse oxytocin 2.5 units in 500 mL of dextrose (or normal saline) at 10
drops per minute (Table P-7 and Table P-8 ). This is approximately 2.5 mIU
per minute.
• Increase the infusion rate by 10 drops per minute every 30 minutes until
a good contraction pattern is established (contractions lasting more than
40 seconds and occurring three times in 10 minutes).
• Maintain this rate until delivery is completed.
• If
hyperstimulation occurs (any contraction lasts longer than 60
seconds), or if there are more than four contractions in 10 minutes, stop
the infusion and relax the uterus using tocolytics:
- terbutaline 250 mcg IV slowly over 5 minutes;
- OR salbutamol 10 mg in 1 L IV fluids (normal saline or Ringer’s
lactate) at 10 drops per minute.
• If there are not three contractions in 10 minutes, each lasting
more than 40 seconds with the infusion rate at 60 drops per minute:
- Increase the oxytocin concentration to 5 units in 500 mL of dextrose
(or normal saline) and adjust the infusion rate to 30 drops per minute
(15 mIU per minute);
- Increase the infusion rate by 10 drops per minute every 30 minutes
until a satisfactory contraction pattern is established or the maximum
rate of 60 drops per minute is reached.
• If labour still has not been established using the higher
concentration of oxytocin:
- In multigravida and in women with previous caesarean scars,
induction has failed; deliver by caesarean section;
- In primigravida, infuse oxytocin at a higher concentration
(rapid escalation):
- Infuse oxytocin 10 units in 500 mL dextrose (or normal saline) at 30
drops per minute;
- Increase infusion rate by 10 drops per minute every 30 minutes until
good contractions are established;
- If good contractions are not established at 60 drops per minute
(60 mIU per minute), deliver by caesarean section.
Do not use oxytocin 10 units in 500 mL (i.e. 20 mIU/mL) in multigravida
and women with previous caesarean section.
TABLE P-7 Oxytocin infusion rates for induction of labour (Note 1 mL =
approximately 20 drops)
Time Since Induction
(hours) |
Oxytocin Concentration |
Drops per Minute |
Approximate Dose (mIU/minute) |
Volume Infused |
Total Volume Infused |
|
0.00 |
2.5
units in 500 mL dextrose or
normal saline (5 mIU/mL) |
10 |
3 |
0 |
0 |
|
0.50 |
Same |
20 |
5 |
15 |
15 |
|
1.00 |
Same |
30 |
8 |
30 |
45 |
|
1.50 |
Same |
40 |
10 |
45 |
90 |
|
2.00 |
Same |
50 |
13 |
60 |
150 |
|
2.50 |
Same |
60 |
15 |
75 |
225 |
|
3.00 |
5
units in 500 mL dextrose or normal
saline (10 mIU/mL) |
30 |
15 |
90 |
315 |
|
3.50 |
Same |
40 |
20 |
45 |
360 |
|
4.00 |
Same |
50 |
25 |
60 |
420 |
|
4.50 |
Same |
60 |
30 |
75 |
495 |
|
5.00 |
10
units in 500 mL dextrose or normal saline (20 mIU/mL) |
30 |
30 |
90 |
585 |
|
5.50 |
Same |
40 |
40 |
45 |
630 |
|
6.00 |
Same |
50 |
50 |
60 |
690 |
|
6.50 |
Same |
60 |
60 |
75 |
765 |
|
7.00 |
Same |
60 |
60 |
90 |
855 |
Increase the rate of
oxytocin infusion only to the point where good labour is established and
then maintain infusion at that rate.
TABLE P-8 Rapid escalation for primigravida: Oxytocin infusion rates for
induction of labour (Note 1 mL = approximately 20 drops)
Time Since Induction
(hours) |
Oxytocin Concentration |
Drops per Minute |
Approximate Dose (mIU/minute) |
Volume Infused |
Total Volume Infused |
|
0.00 |
2.5
units in 500 mL dextrose or
normal saline (5 mIU/mL) |
15 |
4 |
0 |
0 |
|
0.50 |
Same |
30 |
8 |
23 |
23 |
|
1.00 |
Same |
45 |
11 |
45 |
68 |
|
1.50 |
Same |
60 |
15 |
68 |
135 |
|
2.00 |
5
units in 500 mL dextrose or normal
saline (10 mIU/mL) |
30 |
15 |
90 |
225 |
|
2.50 |
Same |
45 |
23 |
45 |
270 |
|
3.00 |
Same |
60 |
30 |
68 |
338 |
|
3.50 |
10 units in 500 mL
dextrose or normal
saline (20 mIU/mL) |
30 |
30 |
90 |
428 |
|
4.00 |
Same |
45 |
45 |
45 |
473 |
|
4.50 |
Same |
60 |
60 |
68 |
540 |
|
5.00 |
Same |
60 |
60 |
90 |
630 |
PROSTAGLANDINS
Prostaglandins are highly effective in ripening the cervix during
induction of labour.
• Check the woman’s pulse, blood pressure and contractions and check the
fetal heart rate. Record findings on a partograph.
• Review for indications.
• Prostaglandin E2 (PGE2) is available in several forms (3 mg pessary or
2–3 mg gel). The prostaglandin is placed high in the posterior fornix of
the vagina and may be repeated after 6 hours if required.
Monitor uterine
contractions and fetal heart rate of all women undergoing induction of
labour with prostaglandins.
• Discontinue use of prostaglandins and begin oxytocin infusion if:
- membranes rupture;
- cervical ripening has been achieved;
- good labour has been established;
- OR 12 hours have passed.
MISOPROSTOL
• Use misoprostol to ripen the cervix only in highly selected
situations such as:
- severe pre-eclampsia or eclampsia when the cervix is unfavourable and
safe caesarean section is not immediately available or the baby is too
premature to survive;
- fetal death in-utero if the woman has not gone into spontaneous labour
after 4 weeks and platelets are decreasing.
• Place misoprostol 25 mcg in the posterior fornix of the vagina. Repeat
after 6 hours, if required;
• If there is no response after two doses of 25 mcg, increase to 50
mcg every 6 hours;
• Do not use more than 50 mcg at a time and do not exceed four doses (200
mcg).
Do not use oxytocin
within 8 hours of using misoprostol. Monitor uterine contractions and
fetal heart rate.
FOLEY CATHETER
The Foley catheter is an effective alternative to prostaglandins for
cervical ripening and labour induction. It should, however, be avoided in
women with obvious cervicitis or vaginitis.
If there is a history
of bleeding or ruptured membranes or obvious vaginal infection, do not use
a Foley catheter.
• Review for indications.
• Gently insert a high-level disinfected speculum into the vagina.
• Hold the catheter with a high-level disinfected forceps and gently
introduce it through the cervix. Ensure that the inflatable bulb of the
catheter is beyond the internal os.
• Inflate the bulb with 10 mL of water.
• Coil the rest of the catheter and place in the vagina.
• Leave the catheter inside until contractions begin, or for at least 12
hours.
• Deflate the bulb before removing the catheter and then proceed with
oxytocin.
AUGMENTATION OF LABOUR WITH OXYTOCIN
• Review for indications.
• Infuse oxytocin as described for induction of labour.
Note: Do not use rapid escalation for augmentation of labour.
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