6.1 Obstretrics Flashcards
Physiological changes seen in pregnancy,
Cardiovascular system
Increase
Increase
Blood volume
Plasma volume
Cardiac output
Heart rate
Physiological changes seen in pregnancy,
Cardiovascular system
Decrease
Decrease
Systemic vascular resistance
Pulmonary vascular resistance
Pulmonary artery pressure
Physiological changes seen in pregnancy,
Cardiovascular system
Unchanged
Unchanged
Central venous pressure
Pulmonary capillary
wedge pressure
Physiological changes seen in pregnancy,
Respiratory system
Increase
Increase
Respiratory
system
Minute ventilation
Alveolar ventilation
Tidal volume
Inspiratory capacity
Physiological changes seen in pregnancy,
Respiratory system
Decrease
Decrease
Functional residual capacity
Minimum alveolar concentration
of volatile anaesthetics
Residual volume
Total lung capacity
Physiological changes seen in pregnancy,
Respiratory system
Unchanged
Unchanged
Respiratory rate
Forced vital capacity
Physiological changes seen in pregnancy
Gastric emptying time
Delayed gastric emptying
Consider patients as non-fasting
Physiological changes seen in pregnancy
Change in composition of blood
Higher increase in
plasma volume
than in red blood cell mass
Physiological anaemia
Physiological changes seen in pregnancy
Change of serum enzymes
Decrease in serum cholinesterase activity
Prolonged action of suxamethonium
Physiological changes seen in pregnancy
Albumin conc
Fall in albumin concentration
Higher free fraction of most
protein-bound drugs,
leading to toxicity
Physiological changes seen in pregnancy
Hormonal affect on LA
Progesterone-mediated
increased
sensitivity to
local anaesthetics
Use lower doses
Physiological changes seen in pregnancy
Change in MAC?
Decrease in minimum alveolar
concentration of
volatile anaesthetics
Use lower
minimum alveolar concentration values
Physiological changes seen in pregnancy
Fibronogen
fibrinogen levels are raised
Protein binding in foetus vs mother
protein binding in the foetus
is less than that in the mother.
This results in higher ionised
fraction of local anaesthetics
in the foetus.
This
free fraction further increases
with foetal acidosis,
resulting in ion trapping
Explain ion trapping.
The protein binding in the foetus is
less than that in the mother.
This results in higher ionised
fraction of local anaesthetics in the foetus.
This free fraction further increases
with foetal acidosis,
resulting in ion trapping.
Ion trapping how does this affect highly protein bound drugs like bupiv
Drugs like bupivacaine which are highly protein-bound may accumulate in this way
Does 2 Chloroprocaine accumulate in acidosis
2-Chloroprocaine is an
ester local anaesthetic.
It does not accumulate in foetus during acidosis,
as it undergoes
rapid hydrolysis by
pseudocholinesterease.
Does RA change newborn behaviour?
Transient neurobehavioural changes
may be seen in
newborn after regional anaesthesia
Pain during First stage of labour
Stage of labour Cause of pain Dermatomes
First stage
Cervical dilatation
Lower uterine segment distension
T10–L1
(Pain afferents via superior hypogastric plexus)
Pain during 2nd stage of labour
Stage of labour Cause of pain Dermatomes
Second stage
Vaginal vault and perineum
S2–S4 (pudendal nerves)
Epidural and labour
Can it Normalise a dysfxn labour?
How?
Epidural analgesia relieves pain.
This decreases the
catecholamine levels in
the mother and
may change dysfunctional
labour to normal labour.
Epidural and labour
Effect on Resp system
It also decreases the
maternal hyperventilation
and prevents left shift in oxygen–
haemoglobin dissociation curve.
Epidural and labour affects on stages
Epidural analgesia
may delay the second
stage of labour.
It may not affect the first stage of labour
pain relief during labour
Combined spinal epidural
affect on baby?
Due to instantaneous pain relief,
it results in fall in maternal catecholamine
and transient changes
in foetal heart rate (bradycardia)
Combined spinal epidural
PDPH
The incidence of
post-dural puncture headache
is similar to epidural block
Paracervical block:
Involves
use?
Paracervical block:
involves injection of
local anaesthetic at vaginal fornix.
It was mainly used to reduce
pain of first stage of labour.
Paracervical block:
Current use?
why
It is not commonly used,
due to its association with
constriction of uterine artery
and foetal asphyxia.
Paracervical block:
second stage
It is not effective for second stage
of labour, as it does not block
the sensory fibres arising from the
perineum.
Paravertebral lumbar sympathetic block
Use?
Common?
Paravertebral lumbar sympathetic block:
can be used for pain relief
during first stage of labour.
However, it is not popular,
as it is technically difficult
and there is higher risk of intravascular injection
Pudendal nerve block:
Where performed
Use?
Pudendal nerve block:
pudendal nerves are blocked
around ischial spines
(and not ischial tuberosity.)
It can be used for analgesia during
1
repair of episiotomy
2
as well as delivery of foetus with forceps
2-Chloroprocaine,
Use?
Preparation days gone by
-issue?
Changed to?
Issue?
2-Chloroprocaine,
which is used intrathecally,
is a preservative-free solution.
In the past, it was formulated
with a preservative sodium
bisulphite which
was shown to be neurotoxic.
Later it was replaced
with EDTA,
which caused severe back pain.
Is there any change to morphine that can be used for section
A new morphine formulation (lipid-encapsulated) for epidural use has been approved for analgesia after lower-segment Caesarean section.
Aspiration of epidural catheter
CSF / Blood
Positive aspiration of
blood or cerebrospinal fluid
from an epidural catheter
identifies intravascular or intrathecal location.
A negative aspiration still does not rule
out a partial intravascular
or intrathecal placement.
Hence it may not be able to
identify the correct location of
the catheter
Other tests that may be used to identify catheter location are:
1
test dose with lignocaine
45 mg with epinephrine 15 mcg
2
epidural hanging drop technique
3
meniscus fall sign
4
injection of air through the epidural catheter and precordial Doppler monitoring.
Maternal mortality RA v GA
The maternal mortality with
general anaesthesia is 16.7 times more
than regional anaesthesia,
according to studies between
1979 and 1990
in the United States.
Hypertensive disorders in pregnancy are classified as
Gestational hypertension:
Pre-eclampsia
Mild / Severe
Eclampsia
Chronic hypertension
Gestational hypertension
Gestational hypertension:
a rise in blood pressure
(> 140/90 mmHg)
after 20 weeks of gestation
without proteinuria
Pre-eclampsia
Pre-eclampsia:
a rise in blood pressure after
20 weeks of gestation
with proteinuria.
Oedema may or may not be present in preeclampsia.
Eclampsia
Eclampsia: pre-eclampsia associated with convulsions
Chronic hypertension
Chronic hypertension:
hypertension detected before 20 weeks of
gestation.
It can be primary or secondary.
Pre eclamptic
change in IV volume?
affect on spinal?
In pre-eclamptic patients,
intravascular volume is depleted.
Hence spinal anaesthesia is associated with severe hypotension in such patients.
Pre eclamptic
Epidural and BP
Epidural anaesthesia results
in gradual fall in blood pressure
and is easy to titrate by
small boluses of local anaesthetic.
Vasopressors and pre eclampsia
Lower doses of vasopressors
are required in patients
with pre-eclampsia,
as they have increased sensitivity to them
The nerve supply to the perineum is as follows.
- Genitofemoral nerve
- Ilioinguinal nerve
- Pudendal nerve
- Perineal branch of the posterior femoral nerve
Genitofemoral nerve
Genitofemoral nerve (L1, L2) –
innervates the
anterior part of perineum.
Ilioinguinal nerve
Ilioinguinal nerve –
innervates the anterior part of perineum
Pudendal nerve
arises
then
Pudendal nerve
arises from the anterior rami of S2–S4.
These form a trunk before
leaving the pelvis via
the greater sciatic foramen.
Pudendal nerve
passage
terminates
It passes immediately behind the
ischial spine and swings forward to
enter the perineum via the lesser sciatic foramen.
The nerve passes
through the ischiorectal fossa,
where it gives off its terminal branches,
which are
Pudendal nerve branches
Inferior rectal nerve
Perineal nerve
Superficial branch
Dorsal nerve of the clitoris
Inferior rectal nerve
branch of pudendal
– innervates the external
anal sphincter and the
perineal skin
Perineal nerve
Perineal nerve –
branch of pudendal
deep branch innervates the
sphincter urethrae and
other muscles of the anterior compartment
Superficial branch pudendal
Superficial branch –
and the skin of the perineum
posterior to the clitoris
branch of pudendal
Dorsal nerve of the clitoris
Dorsal nerve of the clitoris –
branch of pudendal
supplies the skin surrounding this
structure
Perineal branch of the posterior femoral nerve
innervates?
Perineal branch of the posterior femoral nerve
– innervates the
lateral part of perineum.
nerve supply to perineum nerve
Analgesics in pregnancy
safe
paracetamol
opioids
Analgesics in pregnancy
Unsafe
Unsafe
1 non-steroidal anti-inflammatory drugs foetus: renal dysfunction and patent ductus arteriosus mother: haemorrhage
Analgesics Breastfeeding
Safe
Breastfeeding
Safe
non-steroidal anti-inflammatory drugs and
paracetamol
opioids
antiepileptics (neuropathic pain)
tricyclic antidepressants: amitriptyline,
imipramine
selective serotonin reuptake inhibitors
Analgesics Breastfeeding
Unsafe (caution advised)
ketorolac
aspirin
up to 100 mg/day
