anesthesia for obstetrics
obstetric is a study focuses on pregnancy, delivery,
pre and postpartum period .
in relation with anesthesia is defind
as : peripartum anesthetic and analgesic
activities performed during labor and delivery(natural delivery ),
cesarean delivery, removal of remaining placenta, and postpartum tubal
Physiological changes :
Maternal physiological changes occur to meet the increasing
metabolic demands of the foetus and prepare the mother for delivery these changes
will results in :
a- cardiovascular changes : Cardiac output increases by up to 50%
by the third trimester. Stroke volume increases by 35% predominately because of
the increased blood volume. The increase in circulating progesterone causes
vasodilatation and a fall in peripheral vascular resistance. Heart rate will
increases by 15 – 25% .
b- hematological changes : Blood Volume increases
progressively from 5-8 weeks gestation and reaches a maximum at approximately
30-34 weeks. The plasma volume increases by 45% mediated by estrogen and progesterone
acting on the kidneys initiating RAAS pathways. body water is totaly increases due
to renal sodium retention. Most of the excessive volume is accounted for by an
increased capacity of the uterine, breast, renal, striated muscle , with no
evidence of circulatory overload in the healthy parturient. Renal
erythropoietin increases red cell mass by 20-30% which is a smaller rise than
the plasma volume, resulting in haemodilution and a decrease in haemoglobin level
from 15 g/dl to 12 g/dl. This is termed the physiological anaemia of pregnancy.
c- respiratory changes
: Changes in the respiratory system are
of great significance to the anaesthetist and may be categorised as anatomical
and physiological. O2 consumption will increases , FRC will decreases due to
large uterus pressing on diaphragm and work of breathing will be increased .
Reports suggest failure to intubate the trachea is 6- 10 times more common in
the term parturient compared with non-pregnant.
d- gastrointestinal changes :
Aspiration of gastric contents is an important
cause of maternal morbidity and mortality associated with general anaesthesia. Heartburn can affect
up to 75% of woman at term and the supine position may trigger the reflux.
There is no evidence of delayed gastric emptying during pregnancy itself,
however labour is highly associated with
increased gastric volumes and delayed emptying. This is exacerbated by the
administration of opioids.
The enlarging uterus will displate the gastric axis
and causes a gradual displacement of stomach and intestines. These mechanical
forces will lead to increased intragastric pressures as well as a change in the
angle of the gastroesophageal junction, which in turn tends toward greater esophageal
reflux. Relaxation of the lower esophageal sphincter has been described,
but the upper oesophageal sphincter is not affected by progesterone as it is made
from striated muscle. Induction of GA will reduces upper oesophageal sphincter
tone, increasing the risk of aspiration. Pregnant women should be considered to
have a “full stomach” with increased risk of aspiration during most
e- renal changes : The increased blood volume and cardiac
output will lead the renal plasma flow
and glomerular filtration rate (GFR) to increase progressively during pregnancy
and both are 54-60% higher at term. The increased clearance of urea,
creatinine, and excretion of bicarbonate results in lower plasma levels than in
the non-pregnant population. Mild glycosuria and/or proteinuria can occur in normal
pregnancy because the increase in GFR may overwhelm the renal tubules ability
to reabsorb glucose and protein. normal creatinine level may show disease .
endocrine changes : ,pregnancy is associated with insulin resistance caused by
human placental lactogen. This will facilitate placental glucose transfer and any
carbohydrate load will cause a greater increase in plasma glucose. The foetus depends
on its own production of insulin, as mother insulin does not cross the
placenta. Approximately 5% of pregnancies are complicated by
maternal diabetes mellitus (80% of which are gestational). Maternal
hyperglycaemia will result in foetal
hyperglycaemia with secondary foetal hyperinsulinism and neonatal hypoglycaemia
after delivery . Insulin is the main ‘growth hormone’ of the fetus and
therefore infants of diabetic mothers are often macrosomic (> 4,000 g),
resulting in an increase in assisted caesarean sections and deliveries.
Types of delivery :
1 – natural vgainal delivery
2- cesarean section
c- sections :
is surgical method for delivering
of a baby. It involves incision in the mother’s abdomen and another in the
Indications for c- section :
A –related to foetal:
1- big babies .
2- very low birth weight .
3- abnormal lie either transvers or breach.
4- congenital anomalies.
5- conjoined twins , triplets .
B – related to maternal :
1- mother request
2- small pelvic outlet .
3- abnormal placentation .
4- maternal medical conditions ( aggressive hypertension
,heart disease) .
5-matenal had previous
Anesthesia types :
1- spinal anesthesia :
Which is the most common type in elective c- sections . aorto
caval compression should be avoided by using right widge to increase venous
return and blood flow to the foetus .
2- general anesthesia
Which is the plan for emergency c- sections with rapid sequence
induction and cricoids pressure . why ? because of the delivery of the baby should
be done in 30 mins .
Patient preparation before an elective c- section :
Placement of an intravenous IV line .
Infusion of IV fluids (eg, lactated Ringer solution or saline with 5% dextrose)
Placement of a Foley catheter (to drain the bladder and to monitor urine
Placement of an external fetal monitor and monitors for the patient’s blood
pressure, pulse, and O2 saturation.
Preoperative antibiotic prophylaxis (decreases risk of endometritis after
elective cesarean delivery by 76%, regardless of the type of cesarean delivery
emergent or elective
Evaluation by the surgeon and the anesthesiologist .
7-Complete blood count (CBC).
8- Blood type and screen,
9 – Screening tests for human
immunodeficiency virus, hepatitis B, syphilis.
10- Coagulation studies (eg, prothrombin and
activated partial thromboplastin
times, fibrinogen level) .
Medications should be avoided in c-section :
1- opiods like
morphine and fentanyl to avoid neonatal respiratory depression.
2- in aortic stenosis spinal medications should be avoided .
3- in liver disease hepatotoxic medications like volatile and
4- in renal
disease choice of drug depend on the renal ecxcretion should be avoided like recronium
5- in multiple
sclerosis succinylcholine should be avoided with sever musculoskeletal involvement
Types of placenta previa :
Placenta previa, occurs when the placenta covers
all or part of the cervix during the last
months of pregnancy. This condition can cause massive bleeding before or during
labor. It has four grades or
Grade I Low lying placenta .
II Meets the edge of
the cervix .
covers the cervix.
IV Completely covers
the cervix .
Is synthetic drug derive from oxytocin which is a natural
hormone secreted by posterior putitary gland , they increases the tone of
uterine contraction . used for induction and maintenance of labour , control
post partumhaemorrhage and promotion of milk ejection .
Complications associated with c-section :
1-Approximately 2-fold increase in maternal
mortality and morbidity with cesarean delivery relative to a vaginal delivery Partly related
to the procedure itself, and partly related to conditions that may have led to
needing to perform a cesarean delivery.
Infection( postpartum endomyometritis, fascial dehiscence, wound, urinary
Thromboembolic disease (eg, deep venous thrombosis, septic pelvic
Surgical injury (eg, uterine lacerations; bladder, bowel, ureteral injuries)
Delayed return of bowel function .