obstetrics facts

Question 1

WHO class 5 heart issues in obstetrics

Answer 1

Pulmonary arterial hypertension (any cause)
Severe systemic LV dysfunction (NYHA III/IV, LVEF <30%)
Previous peripartum cardiomyopathy and residual LV dysfunction
Aortic root dilation >45mm (Marfan) or >50mm (bicuspid valve)
Severe MS, AS or coarctation

Question 2

List 2 reasons why asthma can lead to improvement in asthma?

Answer 2

Progesterone effects on bronchial smooth muscle

Increased production of corticosteroid

Question 3

List 4 reasons why there is deterioration in some patients with asthma during pregnancy

Answer 3

Reduced sensitivity to β-agonists
Increased prostaglandin levels causing bronchoconstriction
Reduced cortisol sensitivity (as progesterone binds the receptor)
Reluctance to take usual medications

Question 4

3 complications asthmatic parturients at greater risk of?

Answer 4

Asthmatic parturients are more likely to have complications such as pre-term delivery, low birth weight and pre-eclampsia

Question 5

Name one key difference in management of an acute attack for pregnant vs non-pregnant patients

Answer 5

Management is the same as for non-pregnanct patients
One difference is a patient should be deemed to be ‘tiring’ at a PaCO2 of 4.0kPa, rather than a normal PaCO2, owing to the lower levels during pregnancy

Question 6

Follow-up frequency depends on WHO class- class 1, 2 and 3/4/5?

Answer 6

Follow-up frequency depends on WHO class e.g. class I (1-2x in pregnancy), class II (1x per trimester) or class III/IV (1-2x per month)

Question 7

name some changes to ECG due to pregancy alone

Answer 7

LVH
15-20’ left axis deviation
ST-segment and T-wave changes
Lead III: Q-wave and inverted T-wave
Lead AvF: attenuated Q wave
V1-3: inverted T-wave
Atrial or ventricular ectopics
Sinus tachycardia

Question 8

goals in management of cardiac pregnant patients

Answer 8

Minimise cardiovascular stress by minimising the work of labour and delivery
Monitor and maintain fluid balance
Avoid aortocaval compression
Provide aspiration prophylaxis
Implement invasive monitoring

Question 9

Assisted vaginal delivery ± early, incremental, epidural analgesia benefits?

Answer 9

This mode of delivery is advantageous over un-assisted vaginal delivery because there are fewer surges in cardiac output associated with pushing
It is also advantageous over LSCS due to:
Less blood loss
Reduced stress response
Reduced incidence of post-partum pulmonary complications, sepsis and VTE

Question 10

Early, incremental, epidural analgesia has several advantages?

Answer 10

Early, incremental, epidural analgesia has several advantages:
Limits increased cardiac output from pain due to analgesic effect
Reduces both preload and afterload
Limits sympathetic block by careful titration of the level of epidural block required
May be topped up for anaesthesia if required

Question 11

LCSC reserved for what group of cardiac patients?

Answer 11

Typically reserved for either obstetric indications or specific, high-risk maternal conditions:
Marfan syndrome with aortic root dilation >45mm
Acute or chronic aortic dissection
Intractable cardiac failure
Severe pulmonary artery hypertension
Severe aortic stenosis
The choice of anaesthetic for a LSCS should take into account the underlying cardiac disease and severity, wishes of the mother and anaesthetist’s preferences
Uterotonics

Question 12

Uterotonics in cardiac patients

Answer 12

Oxytocin when given as a rapid bolus can cause marked tachycardia, reduced SVR and reduced PVR
Therefore boluses are avoided and an infusion alone may be used
Ergometrine is avoided as it causes increased SVR, PVR and coronary vascular resistance
Carboprost should be avoided due to profound vasodilation, especially when SVR maintenance is important e.g. aortic stenosis

Question 13

How to treat vasodilatation associated with regional technique in patients with cardiac disease

Answer 13

Vasodilation is a feature and should be controlled with titratable vasopressors
Phenylephrine is preferred in stenotic valve lesions to maintain SVR
Ephedrine is preferred in regurgitant valvular lesions due to its positive chronotropic effect

Question 14

disadvantages of a GA section in cardiac patients

Answer 14

Those inherent to GA, inc. aspiration, failed I&V, anaesthetic effects on foetus

↑ blood loss compared to regional anaesthesia

Cardiac instability due to pressor effects of intubation

Effect of GA drugs, which are typically cardiac depressants and/or vasodilatory

Question 15

benefits of a GA in cardiac obstetric patients

Answer 15

Advantages
Reduced maternal anxiety:
↓ catecholamine release and less cardiac work

Stable parameters if ‘cardiac anaesthetic’ provided

Suitable in the anticoagulated patient

Question 16

Monitoring under GA for cardiac obstetrics patients

Answer 16

Standard AAGBI monitoring
Arterial line
Central line may be required, although caution is required with CVP monitoring in the obstetric patient as:
Anatomical variation of the SVC may mean CVC line tip is not where it should be
Irritation by the CVC line may precipitate arrhythmias
Underlying cardiac disease means CVP may not reflect LVEDV
CVP may be a less reliable guide to volume status, especially in PET
TOE may be useful

Question 17

Conduct of GA cardiac anaesthesia

Answer 17

One should aim to avoid tachycardia and large swings in blood pressure
At induction, obtund the hypertensive response to intubation (e.g. alfentanil 25μg/kg, remifentanil 0.5μg/kg) and titrate induction agent carefully
Maintenance is typically with volatile anaesthetic, although addition of remifentanil is useful to:
Reduce volatile requirement and therefore risk of atonic PPH
Reduce chance of hypertension on extubation if continued during emergency

Good analgesia is paramount because pain and tachycardia increase cardiac work; epidural/neuraxial opioids and use of other regional techniques e.g. TAP blocks

Question 18

Post-partum care of cardiac obstetric patient?

Answer 18

Planned admission to HDU/ITU may be required for 24-48hrs post-delivery
Mortality due to maternal cardiac disease tends to be post-partum, due to:
Reduced frequency of monitoring compared to ante-natal period
Large fluid shifts in the post-partum period including 500ml autotransfusion at the time of delivery → acute decompensation
Sub-optimal or early withdrawal of analgesia leading to catecholamine surges from pain → worsening cardiac function or arrhythmias

Answer 19

There is an increased incidence of congenital abnormalities with anti-epileptic drugs
Valproate is the most teratogenic of the lot
Patients should have their medication altered by a Neurologist; the lowest effective dose of a single agent should be used

Question 20

1/3rd of patients experience… in epilepsy pregnancy…
3 things

Answer 20

1/3rd of patients experience worsening seizure frequency, owing to:
Hormonal changes
Altered pharmacokinetics of anti-epileptic drugs
Poor concordance with anti-epileptics
1/3rd of patients experience no change in seizure frequency
1/3rd of patients experience an improvement in seizure frequency

Question 21

5 issues with drugs which are convulsant in epileptics

Answer 21

One should avoid pethidine, whose active metabolite norpethidine is pro-convulsant; other peripartum analgesics are mostly fair game

Tramadol, a technically viable although seldom-used post-operative analgesic, lowers the seizure threshold - especially in combination with SSRIs or TCAs

Tranexamic acid can induces seizures although this is unlikely in the 1-2g dosing regimen one might use in Obstetrics

If seizures occur they should be treated in the standard fashion (see notes from the ICM section on status epilepticus)

One should be mindful that seizures can be a manifestation of eclampsia, which should be excluded or treated accordingly