Non-obstetric surgery during pregnancy

A 23-year-old female presents on a Sunday evening with acute appendicitis and is

booked for urgent appendicectomy. She is Caucasian and has been a UK resident all

her life. She is 19 weeks pregnant. She was previously fit and well although has noticed

some peripheral oedema and dyspnoea on exertion recently. On examination, she is

found to be unwell, pyrexial (39.5 °C) and tachycardic. On praecordial auscultation, a

mid- to late-systolic murmur at the left sternal edge is audible. Her electrocardiogram

shows left axis deviation, some premature beats and some inconsistent T-wave

changes. An echocardiogram cannot be performed until Monday morning. Her electrolytes

are normal and she has been adequately volume resuscitated by the surgical team.

Which one of the following statements regarding conduct of anaesthesia is TRUE?

a) Surgery should not be delayed until a cardiology opinion can be given

b) Coagulopathy of pregnancy necessitates availability of blood component therapy

c) Nitrous oxide should be avoided as there is evidence that, as a potent inhibitor of

methionine synthetase, foetal detriment may be incurred

d) Awareness should be avoided by the use of slightly elevated concentrations of

volatile anaesthetic agent, given the increased minimum alveolar concentration

(MAC) associated with pregnancy

e) The prophylactic use of terbutaline, as a tocolytic, is recommended to avoid

precipitating miscarriage

Answer: a

Explanation

The clinical features described are normal in pregnancy. The majority (97%) of murmurs

detected in pregnancy are physiological and this murmur does not have sinister

features. Of the other 3%, patients have often had exposure to infectious disease

outside the UK. Furthermore, up to 93% of healthy pregnant women without structural

heart disease have been shown to have an audible murmur of the type described at

some stage during their pregnancy. The ECG changes are also normal in pregnancy.

This patient is clearly toxic from her appendicitis and having been pre-optimised

already, the greatest risk to mother and foetus is further delay. Pregnancy results in a

thrombophilic state so careful attention must be paid to thromboprophylaxis.

Theoretically nitrous oxide should be avoided for the reasons stated, but there is no

evidence that the foetus is harmed if it is used. Minimum alveolar concentration

decreases by up to 30% by 12 weeks gestation. There is no evidence for prophylactic

tocolytics. Non-steroidal anti-inflammatory drugs must be avoided to avoid premature

closure of the ductus arteriosus.

It should be noted that if a healthy pregnant woman presents to her midwife with

these features (and without a pressing surgical emergency) the risk–benefit balance is

altered: a high index of suspicion should be maintained and the murmur investigated.

Reference

Walton N, Melachuri V. Anaesthesia for non-obstetric surgery during pregnancy.

Contin Educ Anaesth Crit Care Pain 2006; 6(2): 83–5.